Diagnostic Imaging AI Flashcards
Why are higher exposure factors needed when using a grid?
Higher exposure factors (higher mAs) are needed when using a grid to increase the quantity of primary X-ray photons.
What is the purpose of the lead shutters in the X-ray collimator?
The lead shutters in the X-ray collimator are used to adapt the size of the radiographic field to the body area being radiographed.
Why are intensifying screens used in conventional (screen-film) radiography?
Intensifying screens are used in conventional radiography to amplify the effect of X-rays, as the radiographic film is poorly sensitive to X-rays.
Where are the intensifying screens integrated in screen-film radiography?
The intensifying screens are integrated into both sides of the light-proof X-ray cassette, with the radiographic film placed in between.
What are the two important properties of intensifying screens?
The two important properties of intensifying screens are speed (ability to produce light and amplify the effect of X-rays) and sharpness (spatial resolution).
When are fast screens preferred in radiography?
Fast screens are preferred for large body parts (abdomen) or when movement artifacts are an issue (thorax).
Why is it recommended to have both fast and slow screens/cassettes available?
It is recommended to have both fast and slow screens/cassettes available to optimize image detail and resolution for different body areas (e.g. long bones).
What are the five sequential steps in film processing?
The five sequential steps in film processing are developing, rinsing, fixing, rinsing, and drying.
What are the two main types of digital radiography systems?
The two main types of digital radiography systems are computed radiography (CR) and direct digital radiography (DDR).
How does computed radiography (CR) work?
Computed radiography (CR) uses imaging cassettes containing a ‘storage phosphor’ plate that stores the absorbed X-ray energy in crystals and is later read by a machine using a laser beam.
What is the key difference between computed radiography (CR) and direct digital radiography (DDR)?
The key difference is that CR systems require a plate reader to scan and erase the storage phosphor plate, while DDR systems capture the radiographic image directly without using a plate reader.
What are some advantages of digital radiography over conventional radiography?
Some advantages of digital radiography over conventional radiography include higher contrast resolution, image manipulation capabilities, fewer exposures needed, quicker process, and easier image storage and sharing.
In what format are digital images stored in digital radiography?
Digital images in digital radiography are stored as computer files in DICOM format.
What is the importance of centring and positioning in radiography?
Centring and positioning in radiography is important to ensure that the body part being radiographed is well positioned and that unwanted rotation is avoided. This helps in obtaining accurate and clear radiographic images.
Give an example of superimposition on a dorsoventral projection of the thorax.
On a dorsoventral projection of the thorax, the sternum should be superimposed with the thoracic spine.
What should be superimposed with each other on lateral projections of the thorax?
On lateral projections of the thorax, the costochondral junctions should be superimposed with each other.
What should be superimposed with each other on lateral projections of the lumbar spine or abdomen?
On lateral projections of the lumbar spine or abdomen, the transverse processes of the lumbar vertebrae should be superimposed with each other.
Why is it important to avoid unnecessary superimposition of the surrounding anatomy onto the radiographic image?
Avoiding unnecessary superimposition of the surrounding anatomy onto the radiographic image is important to obtain a clear and unobstructed view of the specific body part being examined.
What are artefacts in radiography?
Artefacts in radiography are abnormalities or distortions that can appear on a radiograph, which do not represent actual structures. They can affect the appearance of the image and may lead to diagnostic errors if not recognized as artefacts.
What are some examples of artefacts that can occur in digital radiography?
In digital radiography, some artefacts that can occur include grainy images due to under-exposure, loss of structure margins with over-exposure, radiolucent halo surrounding metal implants (Uberschwinger artefact), ghost images from incomplete erasure of the CR plate, and moire artefact (bands seen across the image) resulting from interference between the sampling frequency and grid lines.
What are the biologic effects of X-rays?
X-rays are a form of ionising radiation that can cause harm to living tissues. They can ionise atoms and interfere with the molecular chemistry of cells, resulting in cellular damage. The specific effects depend on the tissue irradiated, characteristics of the radiation, dose received, and duration of exposure.
What is the basic structure of the X-ray tube?
The X-ray tube is composed of the cathode (source of electrons) and the anode (tungsten target), housed in a vacuum glass envelope surrounded by oil and lead housing.
What is the function of the cathode in the X-ray tube?
The cathode is a wire filament made of tungsten and it heats up to form a cloud of free electrons when a small electrical current is passed through it.
What is the function of the anode in the X-ray tube?
The anode is a tungsten target that releases X-rays when collided with accelerated electrons.
What is the purpose of the X-ray generator?
The X-ray generator provides the electrical power to accelerate the electrons in the X-ray tube and produce X-rays.
What are the principle interactions of X-rays with matter?
The principle interactions of X-rays with matter include absorption, scattering, and transmission.
What is the influence of kilovoltage on image contrast?
Higher kilovoltage results in lower image contrast, while lower kilovoltage results in higher image contrast.
How can scatter radiation be reduced?
Scatter radiation can be reduced by using grids, collimators, and lead shielding.
What are the key differences between conventional, computed, and direct digital radiography?
Conventional radiography uses film, computed radiography uses imaging plates, and direct digital radiography uses digital detectors.
Why are pregnant women not permitted to enter radiography rooms?
Pregnant women are not permitted to enter radiography rooms because exposure to radiation can be harmful to the developing fetus.
What are the three main sources of radiation in diagnostic radiology?
The three main sources of radiation in diagnostic radiology are the primary beam, scattered radiation, and leakage radiation from the X-ray tube.
What is the purpose of lead clothing in radiography?
Lead clothing provides protection from scattered radiation, not the primary beam. It should never be placed within the primary beam, even if protected.
How can exposure to ionizing radiation be reduced?
Exposure to ionizing radiation can be reduced by minimizing exposure time, increasing distance from the source of radiation, and using barriers containing materials that absorb X-rays.
What is the principle of the inverse square law in radiography?
The inverse square law states that the intensity of radiation at a given point is inversely proportional to the square of the distance between that point and the source of the radiation.
What is the goal of using barriers in radiography?
The goal of using barriers is to reduce radiation dose as much as possible. Lead is commonly used as a barrier material to absorb X-rays.
What legislation governs the use of X-rays in veterinary practice?
The use of X-rays in veterinary practice is governed by the Ionising Radiations Regulations 2017 (IRR17), the associated Approved Code of Practice, and Guidance Notes for the Protection of Persons against Ionising Radiations arising from Veterinary Use.
Why is regular image back-up and retrieval important in digital radiography?
Regular image back-up and retrieval are important in digital radiography to ensure that images are not lost and can be accessed when needed.
What are the potential storage issues when printing digital radiographs onto paper or film?
Printing digital radiographs onto paper or film can impact cost savings and lead to similar storage issues as with conventional radiographs.
What is the importance of acquiring radiographs of good diagnostic quality?
Acquiring radiographs of good diagnostic quality reduces the chance of missing or misinterpreting a lesion.
According to an eminent veterinary radiologist, what are poor radiographs considered to be?
According to an eminent veterinary radiologist, poor radiographs are considered to be either totally useless or totally misleading.
Why is it necessary to take two orthogonal projections for complete radiographic evaluation of an object?
Taking two orthogonal projections allows for the assessment of all three dimensions of a three-dimensional object.
What is distortion in radiography and how can it be minimized?
Distortion in radiography occurs when a three-dimensional object is converted into a two-dimensional image. It can be minimized by keeping the object close to the image receptor, ensuring proper positioning, and centering the X-ray beam.
What factors should be considered when evaluating radiographic image quality?
The factors that should be considered when evaluating radiographic image quality include density, contrast, sharpness, centring and collimation, and positioning.
What can cause a conventional radiograph to be too pale or too dark?
A conventional radiograph can be too pale due to under-exposure or under-development and too dark due to over-exposure or over-development.
What are the factors that affect X-ray beam attenuation?
The factors that affect X-ray beam attenuation are tissue thickness, tissue composition (density and atomic number), and X-ray energy (kV).
What are the five types of opacity detected on a radiograph, from darkest to brightest?
The five types of opacity detected on a radiograph, from darkest to brightest, are air/gas, fat, soft tissue/fluid, bone/mineral, and metal.
Why can soft tissues and fluid not be differentiated on a radiograph?
Soft tissues and fluid cannot be differentiated on a radiograph because they have the same opacity.
What determines the contrast obtained with the photoelectric effect?
The differences in density and atomic number between tissue types determine the contrast obtained with the photoelectric effect.
What effect does the Compton effect have on image contrast?
The Compton effect decreases image contrast by producing scattered X-rays, causing a diffuse blackening of the radiographic image.
How does the contrast of the radiographic image vary with the selected kilovoltage (kV)?
The contrast of the radiographic image progressively decreases as the kilovoltage (kV) increases.
What technique is preferred for abdominal radiography to maximize contrast between fat and soft tissue?
For abdominal radiography, it is preferred to use a low kilovoltage (kV) and a high milliamperes-second (mAs) to promote the photoelectric effect and maximize contrast between fat and soft tissue.
What are the main methods of scatter reduction in radiography?
The main methods of scatter reduction in radiography are using a grid, collimation to keep the radiographic field size small, and using a lower kilovoltage (kV) if possible/appropriate.
What is the purpose of a step-up transformer in the X-ray machine?
The purpose of a step-up transformer is to convert low input voltage into high output voltage through the process of electromagnetic induction.
What type of current is required for the X-ray machine?
The X-ray machine requires an AC or alternating current.
What is the role of a diode in a rectifier circuit?
A diode is an electrical component that only allows current to flow in one direction in a rectifier circuit.
How many diodes are typically used in a rectifier circuit?
Four diodes are typically used in a rectifier circuit.
What is the purpose of a rectifier circuit in the X-ray generator?
The rectifier circuit ensures that electrons always flow in the correct direction across the X-ray tube, regardless of the change in polarity caused by the alternating current.
What is the advantage of using rectifier circuits in X-ray generation?
Rectifier circuits produce a rectified waveform, which allows X-ray production throughout the entire AC cycle and improves efficiency.
What are the three main types of X-ray generator designs?
The three main types of X-ray generator designs are single-phase, three-phase, and high-frequency generators.
What is the main interaction of X-rays with matter when they have low energy?
The main interaction of X-rays with matter when they have low energy is through absorption, specifically the photoelectric effect.
What is saturation artifact?
Saturation artifact refers to the complete black appearance of soft tissues on over-exposed digital radiographs, which cannot be corrected by image manipulation.
What is contrast in radiography?
Contrast is the difference in density between two adjacent areas on a radiograph.
What factors affect the contrast of an image?
The inherent contrast of the body part, energy of the X-ray photons, amount of scattered radiation reaching the film, and characteristics of the screen-film combination or digital filter/algorithm used.
How can image contrast be improved?
Image contrast can be improved by using a lower kV, reducing scatter with techniques such as collimation and using a grid, and correcting any processing errors in conventional radiography.
What is sharpness in radiography?
Sharpness refers to the ability to distinguish the edges of structures and small details.
What are the three main types of radiographic unsharpness?
The three main types of radiographic unsharpness are movement blur, geometric unsharpness, and screen unsharpness.
What causes movement blur in radiographs?
Movement blur can be caused by patient motion or movement of the table or image receptor.
How can movement blur be reduced?
Movement blur can be reduced by keeping the exposure time as low as possible and using sedation or general anesthesia when necessary.
What is thermionic emission?
Thermionic emission is the release of electrons from a heated cathode.
What is the purpose of the focussing cup in an X-ray tube?
The focussing cup keeps the cloud of electrons tightly together in a beam.
How are the electrons accelerated towards the anode in an X-ray tube?
The electrons are accelerated by applying a large potential difference (or voltage) across the X-ray tube.
What are the two types of anode found in X-ray machines?
The two types of anode are stationary anode and rotating anode.
How does a rotating anode differ from a stationary anode?
A rotating anode has a higher heat loading capacity and is more resistant to heat damage than a stationary anode.
What are the three key parameters adjustable on the control console of an X-ray generator?
The three key parameters are kilovoltage (kV), tube current (mA), and exposure time (seconds).
How does the kilovoltage (kV) affect X-ray production?
The higher the kilovoltage (kV), the higher the energy of the X-rays produced.
What is the composite factor mAs in X-ray production?
The composite factor mAs is the product of tube current (mA) and exposure time (seconds), affecting the quantity of X-rays produced.
Which cells are the most sensitive to radiation?
The most sensitive cells to radiation are cells in the gonads, bone marrow, and epithelial tissues.
Why are muscle and nervous tissue more resistant to radiation?
Muscle and nervous tissue are more resistant to radiation because they are composed of well differentiated cells.
How does the cell environment affect radiosensitivity?
The presence of oxygen enhances free radical damage and increases radiosensitivity due to the formation of reactive oxygen species.
What are the two types of biologic effects of ionising radiation exposure?
The two types of biologic effects are deterministic effects (or tissue reactions) and stochastic effects.
What are deterministic effects of ionising radiation?
Deterministic effects are directly related to the absorbed radiation dose and have a threshold dose below which the effect does not occur.
What are some consequences of local irradiation?
Local irradiation can result in immediate effects like inflammation and necrosis, or delayed effects like atrophic fibrosis.
What are stochastic effects of ionising radiation?
Stochastic effects are random chance events caused by radiation-induced cellular mutations that can result in cancer or hereditary/genetic effects.
Why are stochastic effects of ionising radiation considered potentially harmful?
Stochastic effects have no threshold dose and can occur even with very low doses, making every irradiation potentially harmful.
What legislation implements the worker safety aspects of the Basic Safety Standards Directive?
Ionising Radiations Regulations 1999 (IRR99)
What is the title of the Approved Code of Practice that accompanies IRR17?
Work with ionising radiation: Ionising Radiations Regulations 2017. Approved Code of Practice and Guidance
What do the Guidance Notes for the Protection of Persons against Ionising Radiations provide?
Practical methods of working with X-rays in veterinary practice that afford a high level of radiation protection
What is the purpose of the legislation, code of practice, and guidance notes?
To protect the patient and personnel from hazards arising from the use of ionising radiation, and to describe safe working practice
What must a veterinary practice using X-rays do?
Notify the Health and Safety Executive
Who is responsible for ensuring that all work with X-rays is carried out safely in a veterinary practice?
Internal Radiation Protection Supervisor (RPS)
What role does the Radiation Protection Advisor (RPA) have?
Assist the RPS in setting up a safe system of work within the practice
What should be placed above all doorways leading to the controlled area?
Radiation trefoil signs
What is the first step in evaluating radiographs?
The first step in evaluating radiographs is to decide if the study is adequate and diagnostic.
How can you reduce the risk of missing a lesion in a radiograph?
Developing a consistent routine and being methodical when evaluating radiographs can help reduce the risk of missing a lesion.
What is ‘satisfaction of search’ in radiographic interpretation?
‘Satisfaction of search’ is when an obvious lesion is found and the rest of the image is not thoroughly examined.
What should be taken into consideration when re-evaluating a radiograph?
When re-evaluating a radiograph, the signalment of the animal, the history, and the clinical signs should be taken into consideration.
Why should radiographs always be oriented in the same direction?
Radiographs should be oriented in the same direction for consistency, which enables the reader to become more familiar with how a certain body part should appear in the image.
What is the recommended order to evaluate structures on a thoracic radiograph?
The recommended order to evaluate structures on a thoracic radiograph is: 1) Soft tissues surrounding the thorax, including the visible portion of the abdomen 2) The visible skeletal structures 3) The lungs and trachea / bronchi 4) The pleural space 5) The cardiac silhouette 6) The pulmonary blood vessels and great vessels 7) The mediastinum
What are the rules for radiographic orientation?
The rules for radiographic orientation are: Lateral views - cranial / rostral.
What are the two abnormalities that can be identified with contrast radiography?
The two abnormalities that can be identified with contrast radiography are filling defects and contrast leakage.
What can cause filling defects in contrast radiography?
Filling defects in contrast radiography can be caused by intestinal foreign bodies, uroliths, blood clots, and gas bubbles in the urinary tract, and tumors affecting the wall of the gastrointestinal or urinary tract.
What is contrast leakage in contrast radiography?
Contrast leakage in contrast radiography is confirmed when the contrast agent can be seen in an area that should not normally contain contrast. It can occur following rupture of the gastrointestinal or urinary tract.
Give an example where contrast can extend into a region it would not normally be visible without leakage occurring.
An example where contrast can extend into a region it would not normally be visible without leakage occurring is with a non-perforated gastrointestinal ulcer, where an ‘out-pouching’ of contrast into the stomach/duodenal wall may be seen on a barium series.
What should be done prior to any study of the gastrointestinal tract or the urinary tract?
Prior to any study of the gastrointestinal tract or the urinary tract (or when general anesthesia is necessary), the patient should be starved for at least 12 hours.
Why is chemical restraint contraindicated for some gastrointestinal studies?
Chemical restraint is contraindicated for some gastrointestinal studies because it can cause accidental aspiration of the contrast agent.
What are the three different phases observed in an intravenous urography (IVU) following the intravenous injection of contrast?
The three different phases observed in an intravenous urography (IVU) following the intravenous injection of contrast are: 1. Vascular phase, 2. Nephrogram phase, and 3. Pyelogram phase.
When performing an IVU to investigate for an ectopic ureter, what additional procedure should be performed first?
When performing an IVU to investigate for an ectopic ureter, a pneumocystogram should be performed first to highlight the termination of the ureters.
What are the two forms of interstitial lung pattern?
The two forms of interstitial lung pattern are unstructured interstitial pattern and nodular (or structured interstitial pattern).
How is atelectatic lung different from consolidated lung?
Atelectatic lung is reduced in size and the alveoli are empty and collapsed, while consolidated lung retains a normal size but the alveoli are replaced with fluid or cells instead of air.
Which lung lobe is affected in lung lobe torsion in deep-chested dogs? And in barrel-chested dogs?
In deep-chested dogs, lung lobe torsion affects the right middle lobe. In barrel-chested dogs, it affects the left cranial lobe.
What does an unstructured interstitial pattern in the lungs indicate?
An unstructured interstitial pattern in the lungs indicates a diffuse infiltration of the interstitium with fluid (oedema, exudate, haemorrhage) or cells (inflammatory, neoplastic fibrocytes).
What are some examples of alveolar patterns?
Some examples of alveolar patterns are pneumonia in a dog, cardiogenic oedema in a dog, and angiostrongylosis in a dog.
What causes an increase in opacity in the unstructured interstitial pattern?
An increase in opacity in the unstructured interstitial pattern is caused by a mild and often diffuse infiltration of the interstitium with fluid or cells.
What are some differentials for a diffuse opacification in the lungs?
Some differentials for diffuse opacification in the lungs are neoplasia (lymphoma, haemangiosarcoma, etc.), pneumonitis (viral, parasitic, etc.), disease in transition (onset of cardiogenic or non-cardiogenic pulmonary edema, pneumonia, etc.), pulmonary fibrosis (Westie), eosinophilic bronchopneumopathy (in conjunction with other signs), and artifactual causes (underexposed, underdeveloped radiographs, obesity).
What are some differentials for a localized opacification in the lungs?
Some differentials for localized opacification in the lungs are collapse/partial atelectasis, pulmonary thromboembolism, bronchial foreign body, and disease in transition.
What are the Roentgen signs used to describe a radiographic abnormality or lesion?
The Roentgen signs used to describe a radiographic abnormality or lesion are size, shape, location, number, margination, and opacity.
How is the overall size of an organ or structure identified on a radiograph?
The overall size of an organ or structure can be identified on a radiograph by comparing it to the size of an adjacent structure rather than based on its absolute dimension.
What are some structures often used as reference points to compare the size of organs on a radiograph?
Some structures often used as reference points to compare the size of organs on a radiograph are the intercostal spaces or vertebral body length for the cardiac silhouette, and the vertebral body length for the kidneys.
How can an increase in the size of an organ or structure that is not normally visible on a radiograph be identified?
An increase in the size of an organ or structure that is not normally visible on a radiograph can be identified when it becomes visible due to the increase in size.
What is the significance of shape in radiographic interpretation?
The shape of an organ can be altered by the presence of a lesion, enlargement of a chamber, or compression by an extrinsic lesion. Lesions within organs or structures should also be described in terms of their shape.
How can abnormalities of location be identified in radiographic imaging?
Abnormalities of location can be identified in radiographic imaging by having a good knowledge of normal anatomy and the relationships between organs. Confirmation often requires two orthogonal radiographic projections.
What are some potential causes for alterations in the position of a structure observed on a radiograph?
Alterations in the position of a structure observed on a radiograph can be caused by luxation of a joint, displacement of abdominal organs through a rupture, or other pathological conditions.
Why is it important to check the periphery of an image and the surrounding structures in radiographic interpretation?
It is important to check the periphery of an image and the surrounding structures in radiographic interpretation because lesions are commonly missed in these areas.
What is the main use of barium sulphate in diagnostic radiology?
The main use of barium sulphate is for imaging of the digestive system.
What happens when barium leaks into the peritoneal cavity?
If barium leaks into the peritoneal cavity, it can cause a severe granulomatous peritonitis, which can be life-threatening.
What is the most common risk associated with the use of barium?
The most common risk associated with the use of barium is the danger of an associated aspiration pneumonia.
How can barium aspiration be prevented?
The best way to prevent barium aspiration is to administer it via a stomach tube, and to use a cuffed endotracheal tube if the patient is under general anaesthesia.
What are the four categories of iodinated contrast agents based on their chemical structure?
The four categories of iodinated contrast agents are: 1. Ionic monomers (tri-iodinated), 2. Ionic dimers (hexa-iodinated), 3. Non-ionic monomers (tri-iodinated), 4. Non-ionic dimers (hexa-iodinated).
What is the difference between ionic monomeric agents and ionic dimeric agents?
Ionic monomeric agents contain sodium (increasing toxicity) or meglumine salts, while ionic dimeric agents have lower osmolarity than monomeric agents.
Why can’t ionic contrast agents be used for myelography?
Ionic contrast agents (monomeric or dimeric) cannot be used for myelography due to the increased risk of causing seizures.
Which type of iodinated contrast agents cause less side effects following intra-thecal injection?
Non-ionic monomeric agents cause less side effects following intra-thecal injection.
What is the benefit of using non-ionic dimeric iodinated contrast agents?
Non-ionic dimeric iodinated contrast agents have a lower osmolarity and are less toxic than ionic products.
How are non-ionic dimeric iodinated contrast agents excreted from the body?
Non-ionic dimeric iodinated contrast agents are excreted via the kidneys by glomerular filtration.
What are the organs most sensitive to systemic reactions caused by iodinated contrast agents?
The cardiovascular system, the kidneys, and the nervous system are the most sensitive organs to systemic reactions caused by iodinated contrast agents.
What is the main hemodynamic side-effect of iodinated contrast agents?
The main hemodynamic side-effect of iodinated contrast agents is vasodilation, which can lead to hypotension and tachycardia.
Why should iodinated contrast agents be avoided in patients with left-sided congestive heart failure?
Iodinated contrast agents should be avoided in patients with left-sided congestive heart failure due to the risk of causing hypotension and further compromising the cardiovascular system.
Which patients might have extra-renal excretion of iodinated contrast agents?
Patients with severe renal insufficiency might have extra-renal excretion of iodinated contrast agents, eliminated by the liver (in the bile).
What is the recommended type of iodinated contrast agent for myelography and similar procedures?
Only non-ionic iodinated contrast agents with low osmolarity should be used for myelography and similar procedures.
What is a common complication seen with myelography?
The most frequent complication seen with myelography is the occurrence of seizures when the patient recovers from general anesthesia.
What factors should be considered when determining the cause of left-sided cardiomegaly?
The breed, age, and size of the patient should be taken into consideration.
What are some diseases that commonly cause left-sided cardiomegaly in Cavalier King Charles Spaniels or Poodles?
Degenerative mitral valve disease is a common cause of left-sided cardiomegaly in these breeds.
In larger breeds of dogs, what is a more likely cause of left-sided cardiomegaly?
Dilated cardiomyopathy is more likely to be the cause in larger breeds of dogs.
What would be more likely as the cause of left-sided cardiomegaly in a puppy?
A congenital cardiac disease, such as patent ductus arteriosus, ventricular septal defect, or mitral valve dysplasia, would be more likely.
What would be more likely as the cause of left-sided cardiomegaly in an older dog?
Degenerative mitral valve disease or dilated cardiomyopathy would be more likely.
What are some possible further tests that may be needed to reach a final diagnosis?
Endoscopy, bronchoscopy, rhinoscopy, ultrasonography, CT, MRI, fluoroscopy, fine needle aspiration biopsy, needle core biopsy, surgical biopsy, blood tests, and surgery are possible further tests.
When is radiography most useful for examination?
Radiography is most useful for examination of the thorax.
What are the limitations of radiography?
Radiography is limited for examinations of the head and abdomen, as well as for examination of the spine without myelography.
Why should thoracic radiographs be taken in sternal recumbency prior to radiography?
Thoracic radiographs should be taken in sternal recumbency to avoid atelectasis.
What is the importance of taking radiographs quickly in thoracic imaging?
Radiographs should be taken quickly to reduce the amount of lung collapse that occurs between views.
In what respiratory phase should radiographs be taken to ensure optimum lung aeration?
Radiographs should be taken during peak inspiration to ensure optimum lung aeration.
What technique should be used to avoid blurring artifacts caused by respiratory motion?
A high kVP-low mAs technique should be used to avoid blurring artifacts caused by respiratory motion.
When should chemical restraint be used in thoracic radiography?
Chemical restraint should be used to prevent blurring artifacts caused by voluntary patient motion where appropriate and necessary.
What should be done with the thoracic limbs to prevent superimposition of brachial muscles with the cranial thorax?
The thoracic limbs should be pulled cranially to prevent superimposition of the brachial muscles with the cranial thorax.
What are the three structures that can be identified within the lungs on a normal radiograph?
The three structures that can be identified within the lungs on a normal radiograph are pulmonary arteries, pulmonary veins, and bronchial walls.
What is the location of cranial lobar pulmonary veins in relation to the pulmonary arteries on lateral views?
The cranial lobar pulmonary veins are located ventral to the pulmonary arteries on lateral views.
What are the radiographic features of a bronchial lung pattern?
The radiographic features of a bronchial lung pattern include increased visibility of bronchial walls, thickened bronchi referred to as ‘donuts’ when viewed end-on, and thickened bronchi referred to as ‘tramlines’ when viewed side-on.
What is peribronchial cuffing and what does it indicate?
Peribronchial cuffing is the infiltration of cells or fluid in the peribronchial space, which indicates interstitial disease.
What are the differentials for a bronchial lung pattern?
The differentials for a bronchial lung pattern include bronchitis, bronchopneumonia, eosinophilic bronchopneumopathy, and diffuse tumor.
What are the differentials for peribronchial cuffing?
The differentials for peribronchial cuffing include cardiogenic pulmonary edema, bronchopneumonia, and eosinophilic bronchopneumopathy.
What is an alveolar lung pattern?
An alveolar lung pattern is an increase in lung opacity caused by the replacement of gas in the alveoli with fluid or cells, or when the alveoli are collapsed and void of air.
What features are present in an alveolar lung pattern?
An alveolar lung pattern may have air bronchograms, a lobar sign, and increased lung opacity causing border effacement of soft tissue structures.
What are the differentials for an alveolar lung pattern?
The differentials for an alveolar lung pattern include atelectasis, pneumonia, cardiogenic edema, non-cardiogenic edema, hemorrhage, lung lobe torsion, pulmonary thromboembolism, and tumors.
What are some examples of conditions that can be under-estimated based on radiography alone?
Hyperparathyroidism, fractures or tumors, nasal tumors
Which radiographic projections are used to evaluate the nasal cavities and frontal sinuses?
Intra-oral dorsoventral and rostrocaudal projections, respectively
When is CT sometimes necessary for an accurate evaluation of nasal disorders?
When the lesions are extensive or there is invasion of the cribriform plate or orbit by tumors, or involvement of the frontal sinus with aspergillosis
How can certain nasopharyngeal disorders be detected on radiographs?
Sometimes on well-positioned lateral projections of the head
What types of ear diseases can sometimes be identified on radiographs?
Otitis externa and otitis media
What can cause destruction of the wall of the tympanic bulla, which may be identified on radiographs?
Some neoplastic processes, such as cholesteatoma
What can plain radiography demonstrate in the spine?
Severe bony lesions, such as tumors, displaced fractures, advanced discospondylitis, and degenerative changes
When do radiographic signs of discospondylitis become visible?
Around 2-3 weeks after the onset of the infection
Why is contrast radiography sometimes required during a radiographic study?
Because of the poor contrast resolution of plain radiography
What are some causes of mediastinal mass lesions?
The causes of mediastinal mass lesions can include neoplasia, cysts, abscesses, and granulomas.
What can radiography alone determine in cases of mediastinal mass lesions?
Radiography alone cannot differentiate between the different causes for a mass lesion.
What is a safe sampling method to identify pleural effusions?
Thoracocentesis and analysis of the pleural fluid is normally necessary.
What technique can be useful when dealing with smaller volumes of pleural fluid?
Ultrasonography can be useful to identify a safe sampling ‘window’.
What is a common use of radiography in patients with cardiac disease?
Radiography is used to identify and monitor left-sided congestive heart failure.
Why is radiography as the sole technique for imaging the abdomen not recommended?
Abdominal radiography has limitations, such as poor inherent contrast and inability to differentiate fluid from soft tissue.
What is an example of an abdominal organ enlargement that may be seen on radiographs?
Hepatomegaly (enlargement of the liver) can potentially be seen on a radiograph.
What further tests may be necessary to accurately determine the exact cause of an enlarged abdominal organ?
Ultrasound imaging is often necessary to accurately determine the cause of an enlarged abdominal organ.
What can cause a change in position of a structure?
The change in position may be secondary to the alteration in size and/or shape of an adjacent structure.
How can the position of a lesion affect the diagnosis or intervention?
The position of a lesion is important because it can strongly influence the diagnosis or subsequent intervention.
Why is it important to be familiar with the radiographic anatomy of each body region?
It is important to be familiar with the radiographic anatomy of each body region in order to avoid misinterpretation.
What is an example of a tubular soft tissue opacity structure located between the descending colon and the bladder in a female dog?
The presence of a tubular soft tissue opacity structure located between the descending colon and the bladder would favor enlargement of the uterus in a female dog.
How can the number of organs or tissues influence the differential diagnosis?
The presence or absence of a single lesion versus multiple lesions can influence the differential diagnosis.
What can influence the margin of a lesion?
The margins of a lesion can be well-defined or blurred/ill-defined. A lesion can also have a long or short transition zone with normal tissue.
What does an increase in opacity on an X-ray image usually indicate?
An increase in opacity is usually caused by the presence of an excessive amount of fluid or soft tissue, or by the presence of abnormal mineralizations.
What should be done once the entire radiograph has been evaluated?
A summary or list of the key findings/lesions should be compiled once the entire radiograph has been evaluated.
What are some examples of focal radiolucent lung lesions?
Some examples of focal radiolucent lung lesions are necrotic tumors, abscesses/granulomas, and gas-filled bullae.
How can radiography be useful for evaluating the thorax?
Radiography is a good technique for evaluating the thorax because it allows for the visualization of lung abnormalities.
What can make the interpretation of lungs difficult?
Various factors can make the interpretation of lungs difficult, such as the presence of overlapping structures or unclear findings on the radiograph.
What are the recommended imaging techniques if radiographs are inconclusive?
If radiographs are inconclusive, CT (Computed Tomography) and US (Ultrasound) can be useful for further evaluation.
What are the characteristics of necrotic lung tumors?
Necrotic lung tumors typically have thick and irregular walls.
What are the characteristics of abscesses/granulomas?
Abscesses/granulomas usually have thick and irregular walls.
What are the characteristics of gas-filled bullae?
Gas-filled bullae typically have thin and regular walls.
What are some examples of unstructured interstitial patterns?
Pulmonary oedema, Interstitial haemorrhage, Interstitial pneumonia, Pulmonary fibrosis, Lymphoma
What is a nodular interstitial lung pattern?
A nodular interstitial lung pattern is created by the presence of soft tissue opacity nodules arising from the interstitium.
What are some possible differential diagnoses for a nodular interstitial lung pattern?
Artefacts, Neoplasia, Granulomas, Abscess, Fluid-filled bulla, Cyst, Haematoma, Fluid or mucus filled bronchus viewed end-on
What are end-on pulmonary blood vessels?
End-on pulmonary blood vessels are vessels that are seen overlying vessels of equal or greater diameter in radiographs.
What are some differential diagnoses for a vascular pattern?
Conditions associated with increased lung radiolucency.
What conditions can cause diffuse lung radiolucency?
Artefact, Hypovascularity, Hyperinflation.
What is pulmonary hypovascularity?
Pulmonary hypovascularity is associated with a reduction in the size of the pulmonary blood vessels, making the lungs appear more radiolucent.
What is an example of diffuse lung radiolucency?
Hypoadrenocorticism
What imaging modality is better for evaluating small abdominal structures?
Ultrasonography
What are some signs that would suggest a neoplastic process in an abdominal mass?
Presence of lung nodules (metastases) or involvement of more than one organ
What is a common cause of reduced or loss of serosal detail in the abdomen?
Haemorrhage, carcinomatosis, or peritonitis
What is a good technique for identifying gastrointestinal foreign bodies?
Radiography
When is ultrasonography limited in identifying the cause of gastrointestinal mechanical obstruction?
When there is a large volume of gas within the gastrointestinal tract
What is the imaging modality of choice for diagnosing gastric dilatation and volvulus?
Radiography
What imaging technique is preferred for evaluating the head due to the superimposition of complex bony structures?
Cross-sectional imaging techniques (CT and MRI)
What imaging technique is useful for identifying radiopaque uroliths?
Plain radiographs
What imaging modalities have largely replaced contrast radiography?
Ultrasonography and endoscopy.
What is the purpose of colonography?
To demonstrate the position of the colon and evaluate the colonic wall or look for ileocaecocolic intussusception.
What is required for the majority of CT examinations?
Intravenous injection of an iodinated contrast agent.
What are some uses of contrast radiography that are still very useful?
Investigating suspected rupture of the urinary tract, identifying radiolucent calculi, determining the location of the bladder, investigating oesophageal disorders.
Why is correct radiographic technique important in evaluating the lungs?
It makes it easier to assess the lungs, increases confidence in making an assessment, and reduces the number of avoidable misdiagnoses.
What views should be obtained for a complete assessment of the lungs?
Dorsoventral (DV) / ventrodorsal (VD) and both lateral views.
What is the golden rule of thoracic radiography?
The DV / VD view(s) should always be taken first to avoid lung collapse caused by positioning the patient in lateral recumbency.
Why is taking a single thoracic radiograph not appropriate for assessing the lungs?
It does not allow a complete assessment of the lungs and lesions may be missed or interpreted incorrectly.
What is the main use of contrast radiography in orthopaedic cases?
Performing a shoulder arthrogram
What is the purpose of oesophagography?
To investigate causes of regurgitation
What technique can be used to investigate for urethral obstructions?
Urethrography or vaginourethrography
Which imaging modality has largely replaced myelography?
MRI and CT
What can angiocardiography be used to detect?
Congenital cardiac diseases such as pulmonic stenosis or aortic stenosis, and for evaluation of the coronary arteries
What is the purpose of a barium follow through?
To investigate for foreign bodies, tumors, inflammatory conditions, and assess gastrointestinal transit time
What are the indications for gastrography?
Evaluation of the gastric wall, detecting foreign bodies, and investigating causes of delayed gastric emptying
What is the purpose of dynamic evaluations of the pharynx/oesophagus with fluoroscopy?
To investigate functional disorders or sliding intermittent hiatal hernias
What are the dangers associated with MRI?
The magnetic field used in MRI is very powerful and strict safety measures must be followed to avoid accidents occurring. Metallic objects can turn into dangerous projectiles or crush personnel against the MRI machine. Staff members with a pacemaker and certain types of metal implants should also be prevented from entering the MRI room. Patient microchips create annoying artifacts on MRI which can prevent proper evaluation of the region of interest.
What are the main indications for MRI in veterinary medicine?
In veterinary medicine, MRI is mainly used to assess the brain and spine. It is helpful in identifying brain diseases such as neoplasia, inflammatory disease, vascular pathology, and congenital abnormalities. MRI also allows for better evaluation of intramedullary pathology within the spine and for pathology affecting the spinal nerves.
What can MRI detect in the brain?
MRI is sensitive in detecting large lesions like neoplasia and severe inflammatory disease. It is also more sensitive than CT in detecting subtle changes caused by mild inflammatory disease, infarcts, degenerative disease, congenital abnormalities, metastases, and cranial nerve lesions.
Why is MRI the preferred imaging modality for assessing spinal diseases?
MRI is preferred for evaluating intervertebral disc herniation as it can detect the degenerated and herniated disc rapidly without the need for performing myelography. It allows for easy identification of the lateralization of the lesion and helps in surgical planning. MRI also enables assessment of the spinal cord itself, which is not possible with CT or radiography.
What can MRI detect in the spinal cord?
MRI can detect intramedullary pathology such as fibrocartilaginous embolism, cord neoplasia, and cord edema. It is also useful in identifying intradural extramedullary neoplasia (e.g. meningioma, nerve sheath tumors) and assessing the extent of these tumors. Additionally, MRI is sensitive for diagnosing discospondylitis before any evidence of bony destruction is seen on CT or radiography.
What are the advantages of MRI in diagnosing discospondylitis?
MRI is very sensitive for diagnosing discospondylitis as it can detect subtle abnormalities with the help of IV contrast injection, before any evidence of bony destruction will be seen on CT or radiography.
What are some focal splenic abnormalities that can be identified on an ultrasound?
Focal splenic abnormalities can include nodules, masses, or less well-defined areas of parenchymal change.
What can cause diffuse abnormalities in the spleen on an ultrasound?
Diffuse abnormalities in the spleen can be caused by extramedullary hematopoiesis, nodular hyperplasia, neoplastic infiltration, infection, vascular compromise (splenic torsion), and vascular engorgement (secondary to sedation / GA with ACP or barbiturates).
How does splenic torsion appear on an ultrasound?
Splenic torsion creates a “starry sky” appearance in the splenic parenchyma, with a hypoechoic and lacy appearance due to dilated and obstructed blood vessels.
What is the recommended scanning technique for evaluating the left kidney?
The left kidney can usually be found caudal to the costal arch and the splenic head. Pressure can be applied to the transducer to displace overlying bowel loops if necessary.
Where does the right kidney usually lie in dogs?
The right kidney normally lies partially within the costal arch in dogs, and is usually harder to completely evaluate than the left kidney.
What are some normal findings of the renal cortex on an ultrasound?
The normal renal cortex has a homogenous, finely speckled appearance and is usually hypoechoic compared to the spleen. In cats, it can be more echogenic due to fat deposition, especially in older males.
How can the kidneys be scanned to evaluate for focal lesions?
The kidneys should be scanned in a longitudinal plane by sliding or fanning the probe across the width of the kidney, and also in a transverse plane by sliding or fanning the probe along the length of the kidney.
What can be seen in the renal medulla on an ultrasound?
The renal medulla appears hypoechoic to anechoic and is separated into sections by the echogenic pelvic diverticuli and interlobar vessels. Arcuate arteries may be seen as fine discontinuous echogenic lines at the corticomedullary junction.
What are the main indications for performing ultrasound in the neck region?
The main indications for performing ultrasound in the neck region are the presence of a mass and suspected hyperparathyroidism.
What are the differential diagnoses for a mass in the neck region?
The differential diagnosis for a mass in the neck region includes lymphadenopathy (reactive or malignant), salivary gland pathology (mucocoele, infection, neoplasia), thyroid neoplasia, and abscesses.
What can be identified with ultrasound in the evaluation of the eyes?
Ultrasound can identify retrobulbar masses (neoplasia, abscess) or retinal detachment. It can also detect other ocular diseases such as cataracts, vitreous degeneration, and intraocular tumors.
What conditions can ultrasonography detect in the sciatic nerve?
Ultrasonography can detect evidence of enlargement/neoplasia in the superficial part of the sciatic nerve and can be used to guide FNAs.
What is the goal of performing abdominal ultrasonography?
The goal of performing abdominal ultrasonography is to achieve a thorough examination of the abdomen and obtain diagnostic quality images to answer clinical questions related to vomiting, intestinal obstruction, and renal disease, among others.
Why should patients be starved overnight before abdominal ultrasonography?
Patients should be starved overnight for abdominal ultrasonography to prevent hinderance of the examination by the presence of food or gas in the gastrointestinal tract.
What preparation is necessary before performing abdominal ultrasonography?
Patients should have their hair clipped from the xiphisternum to the pubis and to the level of the lumbar muscles laterally. The application of surgical spirit and ultrasound gel is also required for good contact between the ultrasound probe and the skin.
What is the recommended scanning routine for abdominal ultrasonography?
The recommended scanning routine for abdominal ultrasonography starts in right lateral recumbency. It involves assessing various abdominal structures including the liver, stomach, pancreas, spleen, kidneys, adrenal glands, lymph nodes, bladder, prostate, colon, small intestines, and other specific organs.
When should sedation or general anesthesia be preferred for abdominal ultrasonography?
Sedation or general anesthesia should be preferred for abdominal ultrasonography, especially when the patient is not well-behaved or has tense abdominal muscles, to ensure a thorough examination and if sampling is planned.
What is the ultrasonographic appearance of intussusception?
Intussusceptions have a very recognisable ultrasonographic appearance, with multiple concentric rings in a transverse section and multiple layers in a longitudinal section.
What structures can complicate the appearance of intussusception in ultrasound images?
Other structures such as fat, blood vessels, lymph nodes, and tumors can be associated with the invaginated bowel and complicate the appearance of intussusception.
What is the characteristic feature of gastric and intestinal foreign bodies in ultrasound?
Gastric and intestinal foreign bodies in ultrasound are usually recognized by the reflection of sound from their surface, producing a bright echogenic interface with distal acoustic shadowing.
What intestinal wall changes are frequently seen in the region of a foreign body?
Intestinal wall changes frequently observed in the region of a foreign body include localised thickening and loss of layering.
How can ultrasonography be useful in detecting GI perforation caused by a foreign body?
Ultrasonography can help detect signs of GI perforation caused by a foreign body, including changes to the affected intestinal segment, peritoneal fluid accumulation, increased echogenicity of the mesenteric fat, regional lymphadenopathy, and presence of free gas as reverberation artefacts.
What is the difference between corrugation and plication of the small intestine?
Corrugation of the small intestine appears as an undulating appearance to the intestinal wall, while plication caused by a linear foreign body causes pronounced bunching and a linear echogenic shadowing interface within the lumen.
How can the pancreas be located during ultrasound scanning?
In dogs, the right limb of the pancreas can be located between the right kidney and duodenum, using the duodenum as a landmark. In cats, the left limb of the pancreas is larger and easier to see, located along the lesser curvature of the stomach towards the spleen.
What landmarks are used to locate the right limb of the pancreas?
The duodenum, which lies adjacent to the right body wall and can be followed cranially towards the stomach, and the right kidney, which lies medial to the duodenum, are used to locate the right limb of the pancreas.
What are the advantages of ultrasound?
Ultrasound is non-invasive, provides good soft tissue detail, enables evaluation of internal organ architecture, allows differentiation of fluid from soft tissue, and can detect small volumes of fluid.
How can ultrasound be used to examine abdominal structures?
Ultrasound has excellent contrast resolution, differentiates between fluid and soft tissue, and enables a more detailed assessment of the abdomen. It is useful for identifying abnormalities, guiding fine needle aspirates and needle core biopsies, detecting peritoneal fluid, and diagnosing various abdominal diseases.
What are the disadvantages of using ultrasonography?
The main disadvantage is that ultrasound results can vary depending on the machine and the sonographer. It requires practice and experience to obtain quality images and interpret them correctly. Ultrasound machines can be expensive, and the equipment is prone to damage if not handled carefully. Ultrasound examinations require hair clipping, which some owners may object to. The presence of gas and large amounts of fat can hinder examinations and reduce image quality. Additionally, many ultrasound findings are non-specific and may require further cytology or histology for a final diagnosis.
What can ultrasound be used for besides abdominal imaging?
Ultrasound can also be used for thoracic imaging, echocardiography, imaging the neck, as well as examining eyes, hydrocephalus, nerves, and tendons.
How does ultrasound compare to radiography in terms of soft tissue detail?
Ultrasound provides very good soft tissue detail, whereas radiography has limited assessment of the abdomen due to poor contrast resolution.
Why is sedation sometimes beneficial during ultrasound?
Sedation can be beneficial for stressed or tense patients, as it helps with restraint and allows for smoother ultrasound examinations.
What can hyperechoic mesenteric fat indicate during ultrasound?
The presence of hyperechoic mesenteric fat during ultrasound can indicate the presence of peritonitis.
What are some severe lesions that can be demonstrated by CT?
Severe lesions such as neoplasia (e.g. glioma, meningioma, trigeminal nerve tumour, pituitary macroadenoma), hydrocephalus, and severe inflammatory diseases (e.g. abscesses, necrotising meningoencephalitis) can be demonstrated by CT.
Why is MRI preferred over CT for neuroimaging?
MRI is preferred over CT for neuroimaging because small or subtle intracranial pathology such as inflammatory disease, vascular disease (e.g. stroke), or congenital lesions may be missed with CT.
What are the preferred imaging modalities for evaluating the nasal cavities and paranasal sinuses?
CT is the imaging modality of choice for evaluating the nasal cavities and paranasal sinuses.
What are some other indications for performing a head CT?
Other indications for performing a head CT include retrobulbar disease, middle ear disease, dental disease/abscess, or a mass of unknown origin (abscess, tumour, lymph node, salivary gland).
What can CT be used for in the evaluation of the soft tissue structures of the neck?
CT is a very good technique for evaluating the soft tissue structures of the neck, including lymph nodes, thyroid glands, larynx, esophagus, or the muscles and fascial planes.
What is the main use of spine CT?
Spine CT is a very good imaging modality for identifying bony lesions of the spinal column.
What diseases can CT be used to investigate in chondrodystrophoid breeds of dog?
CT is a good imaging technique for looking for intervertebral disc disease in chondrodystrophoid breeds of dog (e.g. Dachshund, Bulldog, Basset hound).
What is the proposed method for assessing renal size in dogs?
The proposed method for assessing renal size in dogs is using the ratio between renal length and the aortic diameter (K:Ao ratio).
What is the normal range for the K:Ao ratio in dogs?
The normal range for the K:Ao ratio in dogs is 5.5 to 9.1.
How can the ureters be seen ultrasonographically in normal animals?
The ureterovesicular junctions may be seen in normal animals as convex structures on the dorsal bladder mucosa.
What causes subcapsular fluid in the kidneys?
Subcapsular fluid in the kidneys can be caused by trauma (haemorrhage, urine), acute renal failure, infection (pyelonephritis, leptospirosis, FIP), or neoplasia.
What are perinephric pseudocysts and where are they located?
Perinephric pseudocysts are large accumulations of fluid located between the capsule and the renal cortex, surrounding one or both kidneys.
What can increased cortical echogenicity in the kidneys indicate?
Increased cortical echogenicity in the kidneys can indicate nephritis, toxin ingestion (e.g. ethylene glycol), neoplasia, or normal cats with fatty infiltration.
What is the medullary rim sign and what can it indicate?
The medullary rim sign is a continuous hyperechoic band sometimes seen at the corticomedullary junction. It can indicate several renal diseases such as hypercalcemic nephropathy, ethylene glycol intoxication, acute tubular necrosis, chronic interstitial nephritis, and feline infectious peritonitis.
What are the causes of reduced cortical echogenicity and decreased corticomedullary definition in the kidneys?
Causes of reduced cortical echogenicity and decreased corticomedullary definition in the kidneys include congenital renal dysplasia, chronic inflammatory disease, and end-stage renal disease.
What are some of the causes of diffuse hepatic abnormalities?
Diffuse hepatic abnormalities can be caused by inflammation, edema, cystic mucosal hyperplasia, neoplasia, and other conditions.
How can choleliths be identified on ultrasound?
Choleliths can be identified by settling with gravity in the dependent aspect of the gall bladder and often casting an acoustic shadow.
What are the differentials for gall bladder wall thickening?
The differentials for gall bladder wall thickening include inflammation (cholecystitis), edema, cystic mucosal hyperplasia, and neoplasia.
What is a gall bladder mucocele?
A gall bladder mucocele is an excessive accumulation of mucus in the gall bladder lumen, which can lead to overdistension, wall necrosis, rupture, and biliary obstruction.
How can a gall bladder mucocele be identified on ultrasound?
A gall bladder mucocele can be identified by the peripheral accumulation of hypoechoic mucus, causing central displacement of the echogenic biliary sludge.
What are some other causes of biliary obstruction?
Other causes of biliary obstruction include pancreatitis, choleliths, and neoplasia in the biliary tract, duodenum, or pancreas.
What is the scanning technique for visualizing the spleen on ultrasound?
The transducer is positioned along the left costal margin, and the spleen is examined in both sagittal and transverse planes by sliding the transducer along its length.
What are the normal findings of the spleen on ultrasound?
In a dog, the spleen should appear more echogenic than the liver, have a finer echotexture, and have smooth margins with a well-defined fine echogenic capsule.
When should normal postpartum involution be complete in dogs?
Normal postpartum involution should be complete by 3-4 weeks in dogs.
When should normal postpartum involution be complete in cats?
Normal postpartum involution should be complete by day 24 in cats.
What are the main ultrasonographic findings of pyometra?
The main ultrasonographic findings of pyometra are an enlarged uterus and uterine horns.
How does the luminal contents of an enlarged uterus with pyometra usually appear on ultrasound?
The luminal contents of an enlarged uterus with pyometra usually appear anechoic on ultrasound.
What important evidence should be looked for when dealing with stump pyometra?
When dealing with stump pyometra, evidence of ovarian remnants should also be looked for.
What is the scanning technique for examining the prostate?
For examination of the prostate, a full bladder is also helpful for providing an acoustic window. The prostate is identified by following the bladder neck caudally to the urethra, and should be scanned in both transverse and longitudinal planes.
When does the echogenicity of the prostate vary with age and entirety?
The echogenicity of the prostate is more likely to be hyperechoic in young entire animals and hypoechoic in older and castrated animals.
What is the appearance of the testicles on ultrasound?
The testicles are oval in shape, with a smooth echogenic capsule and moderately echogenic homogenous parenchyma.
What is the cause of the mirror image of the liver parenchyma seen beyond the diaphragm?
The mirror image of the liver parenchyma beyond the diaphragm is an artifact due to the highly reflective nature of the liver/lung interface.
How can the liver margins provide information about liver health?
Smooth margins suggest normal liver size, while irregular margins may indicate chronic disease or the presence of multiple nodules distorting the liver capsule.
How can liver size be assessed using ultrasonography?
The location of the caudal liver borders with respect to the costal margin can give an indication of liver size. An enlarged liver will extend well beyond the rib cage, while a small liver will be tucked well within the rib cage.
What can an increase in the visibility of the portal vessel walls indicate?
An increase in the visibility of the portal vessel walls could be due to an overall decrease in the echogenicity of the hepatic parenchyma.
What can the dilation of the hepatic veins indicate?
Dilation of the hepatic veins could be due to right-sided heart failure with secondary engorgement of the caudal vena cava or due to obstruction of the vena cava itself.
What can anomalous vessels and turbulent blood flow be associated with?
Anomalous vessels and turbulent blood flow are often associated with portosystemic shunts or, more rarely, arterio-venous fistulae.
Where is the gallbladder located and how does it appear on ultrasound?
The gallbladder is located just to the right of the midline, between the quadrate and right medial liver lobes. It usually appears as an anechoic rounded or ovoid structure.
What can echoes within the gallbladder indicate?
Echoes within the gallbladder may be due to slice thickness artifact (pseudosludge), sludge, or choleliths.
How is each image (or frame) made in ultrasound?
Each image is made by electronically sweeping a thin ultrasound beam through the field of view, creating numerous thin scan lines per image.
What is the purpose of updating the images multiple times per second?
Updating the images multiple times per second allows the tissues and any movement to be assessed in real time.
What is M-mode in ultrasound?
M-mode records a thin section of the ultrasound image over time, displaying the movement of the interfaces along the selected line with time.
What is the main use of M-mode in ultrasound?
M-mode is mainly used during echocardiography for quantitative assessment of the function of the ventricles and the heart valves.
What machine controls can be manipulated by the operator on ultrasound machines?
Machine controls that can be manipulated by the operator include: Transducer frequency, Overall gain, Time gain compensation, Depth, Focal point depth, Sector angle, Correlation / persistence, and Pre / post processing.
How does the transducer frequency affect the ultrasound image?
The higher the frequency of the ultrasound beam, the better the resolution of the image will be, but higher frequency transducers have limited penetration and cannot image deeper structures.
What does changing the overall gain on an ultrasound machine affect?
Changing the overall gain affects the degree of amplification of the echoes within the receiver, which alters the brightness of the whole image.
What is the purpose of time gain compensation in ultrasound?
Time gain compensation enables a higher gain (or greater amplification) to be applied to the echoes received from deeper tissues, compensating for the increased ultrasound beam attenuation at greater depths and ensuring uniform image brightness throughout the depth of the image.
What information do MRI signals provide about the protons in the patient?
MRI signals provide information about the exact location of the protons in the patient.
How are the signals produced by different tissues distinguishable in MRI?
The signals produced by different tissues are distinct because their protons realign at different speeds, allowing the body tissues to be distinguished from each other.
What is the function of the computer in the MRI process?
The MRI signal is collected and transmitted to the computer to be analyzed and processed to form the MRI image.
What are the five key sequences used in MRI?
The five key sequences used in MRI are T1 weighted images (T1w), T2 weighted images (T2w), FLAIR (Fluid-Attenuated Inversion Recovery), STIR (Short Tau Inversion Recovery), and T2* sequences.
How does fluid appear in T2w sequences and T1w or FLAIR sequences?
Fluid appears white (hyperintense) on T2w sequences and black (hypointense) on T1w or FLAIR sequences.
What is the basic concept of MRI imaging planes?
During an MRI study, each sequence acquisition is planned and reconstructed in a specific imaging plane, such as transverse, sagittal, and dorsal.
What are the advantages of MRI over radiography or CT?
MRI has superior contrast resolution, excellent for assessing soft tissue structures, can differentiate fluid from fat, muscle, spinal cord, or brain, and removes the problem of superimposition.
Why are MRI studies of veterinary patients performed under general anesthesia?
It is very important that the animal does not move during the examination, and MRI machines produce a lot of noise.
What is the purpose of a directed search pattern in evaluating the intestines?
A directed search pattern is used to minimize the risk of missing important lesions.
How can the evaluation of some areas of the intestinal wall be limited?
The presence of gas and ingesta in the lumen may limit the evaluation of some areas of the intestinal wall.
What type of probes are ideal for evaluating the intestines?
Linear probes are ideal for evaluating the intestines as they provide superior near field imaging.
What type of probes may be required for larger patients or loop located deeper within the abdomen?
For larger patients or loop located deeper within the abdomen, lower frequency probes (e.g. curvilinear or microconvex) may be required to provide adequate penetration.
What are the normal findings in the stomach?
The stomach is located just caudal to the liver with the fundus to the left of the midline and the pylorus midline (in cats) or to the right of midline (in dogs).
What serves as a landmark for locating the right pancreatic limb?
The duodenum serves as a landmark for locating the right pancreatic limb.
What is the characteristic appearance of the stomach and small intestine on ultrasonography?
The stomach and small intestine demonstrate a characteristic 5-layered appearance on ultrasonography (mucosal interface/surface, mucosa, submucosa, muscularis, serosa).
What should be assessed when examining the stomach and intestine on ultrasound?
The stomach and intestine should be assessed for wall thickness, presence or absence of layering, echogenicity of the layers, relative width of the layers, luminal diameter, and the degree of motility.
What can make the pancreas more difficult to find on ultrasound?
A tense abdomen due to pain and the presence of gas within the adjacent GI tract.
What is the normal appearance of the pancreas on ultrasound?
The normal pancreas is an elongated V-shaped structure, which is isoechoic to hypoechoic to the surrounding abdominal fat.
What is the classic appearance of acute pancreatitis on ultrasound?
An enlarged and diffusely hypoechoic pancreas, surrounded by hyperechoic fat.
What can fluid-filled lesions in pancreatitis represent?
Haemorrhage, necrosis, pseudocysts, or abscesses.
How can pancreatic neoplasia be distinguished from pancreatitis on ultrasound alone?
Pancreatic neoplasia cannot be distinguished from pancreatitis on the basis of the ultrasonographic appearance alone.
What is the most common type of pancreatic tumor?
Adenocarcinomas.
What clinical signs may be observed in patients with insulinomas?
Patients with insulinomas often display clinical signs of hypoglycemia, even when the tumor is very small.
What is the preferred imaging modality for identifying pancreatic tumors?
Abdominal CT is normally the preferred and most sensitive imaging modality for identifying pancreatic tumors.
What is acoustic impedance?
Acoustic impedance is the resistance of different tissue types to the transmission of ultrasound waves, which is determined by their tissue density and the velocity at which the ultrasound beam travels through them.
How is acoustic impedance calculated?
Acoustic impedance is calculated by multiplying tissue density by velocity: Acoustic impedance = tissue density x velocity.
What happens when a sound wave crosses a boundary between two tissues with different acoustic impedance?
Part of the sound wave is reflected back to the transducer as an echo, while the remaining portion is transmitted into the deeper tissue.
What determines the proportion of sound wave reflected and transmitted at a tissue boundary?
The proportion of sound wave reflected and transmitted at a tissue boundary depends on the difference in acoustic impedance between the two tissues.
What happens when there is a large difference in acoustic impedance at a tissue interface?
A large reflection occurs, resulting in no useful image beyond the interface or an acoustic shadow. This is observed at soft tissue-gas and soft tissue-bone interfaces.
What happens when there is a small difference in acoustic impedance at a tissue interface?
A small reflection occurs, allowing for a useful image beyond the interface. For example, this occurs at soft tissue-fat interfaces.
What is the angle of incidence?
The angle at which an ultrasound wave encounters an interface.
What happens if the angle of incidence is perpendicular (90 degrees) to the interface?
The echo is reflected in the exact opposite direction, while the transmitted portion of the sound wave continues in the same direction.
What are the upper limits for normal small intestinal wall thickness in dogs?
The jejunum should measure no more than 4.7 mm and the duodenum no more than 6 mm.
What are the upper limits for normal small intestinal wall thickness in cats?
The duodenum normally measures less than 3-3.5 mm and the jejunum less than 2.5-3 mm.
What are the normal rates of peristalsis in the stomach and proximal duodenum?
4-5 contractions per minute.
What are the normal rates of peristalsis in the rest of the small intestine?
1-3 contractions per minute.
What can prevent the far intestinal wall from being assessed and the luminal diameter from being measurable?
Gas in the intestine causing shadowing.
What are the four general luminal patterns that can be identified in the normal small intestine?
- Mucous Pattern, 2. Gas, 3. Fluid, 4. Alimentary.
What is the most common finding with inflammatory diseases in the gastrointestinal tract?
Thickening of the wall with preservation of wall layering.
What are the most common tumour types causing wall thickening and loss of layering in the gastrointestinal tract?
Adenocarcinoma, lymphoma, mast cell tumour, and leiomyosarcoma.
Where are inguinal lymph nodes found?
Inguinal lymph nodes are found in the flank outside of the peritoneal cavity.
What is the normal appearance of lymph nodes in the mesentery?
Normal lymph nodes in the mesentery are usually isoechoic to hypoechoic and fusiform in shape.
What is the typical length of medial iliac lymph nodes?
The length of medial iliac lymph nodes is typically up to 6cm.
How do normal jejunal nodes appear on ultrasound?
Normal jejunal nodes are typically elongated and uniformly hypoechoic.
Which abdominal organs are often not visualized during an ultrasonographic examination?
Normal hepatic, splenic, gastric, and pancreaticoduodenal nodes are often not visualized.
What is the characteristic appearance of an abscess on ultrasound?
Abscesses tend to have thick walls and echogenic contents; they may cause distal enhancement and acoustic shadowing if they contain gas.
Where can the abdominal aorta and caudal vena cava be examined from?
The cranial abdominal aorta and caudal vena cava can be examined from ventrally with the animal in dorsal recumbency, or from the flank and caudal intercostal area.
In what position is the aorta located in relation to the caudal vena cava?
The aorta is located in the dorsal midline, to the left of the caudal vena cava.
Which structures appear brighter deep to fluid-filled structures?
The tissues deep to fluid-filled structures appear brighter.
Where are acoustic shadows most often seen?
Acoustic shadows are most often seen deep to the gall bladder and the urinary bladder.
What causes the production of anechoic shadow deep to highly reflective interfaces?
An anechoic shadow is produced when the ultrasound beam is largely reflected and/or absorbed at the interface, such as a soft tissue-bone interface.
What are acoustic shadows useful for identifying?
Acoustic shadows are useful for identifying foci of mineralization, calculi, and foreign bodies.
What produces reverberation artifacts?
Reverberation artifacts are produced when sound waves are reflected multiple times between two strong reflectors, usually foci of gas within the patient and the ultrasound probe.
How is a mirror image artifact created?
A mirror image artifact is created by the reflection of an ultrasound beam from a highly reflective interface, such as the diaphragm-lung interface, back into the organ being examined.
What causes edge shadowing?
Edge shadowing is caused by the bending of ultrasound waves when they hit a curved surface at a tangent.
What creates the appearance of pseudo-sludge in the bladder lumen?
Slice thickness artifact creates the appearance of pseudo-sludge in the bladder lumen.
What position is the patient turned into to scan the liver from the right side?
Left lateral recumbency
What is the purpose of scanning the small intestines during an abdominal ultrasound?
To ensure a thorough examination
Why is it sometimes helpful to put patients in dorsal recumbency during an abdominal ultrasound?
To redistribute fluid / gas within the GI tract, or to follow distended or tortuous GI loops
Does the order in which you choose to scan the abdominal organs matter during an abdominal ultrasound?
No, the order does not matter
What should be considered when choosing the ultrasound probe and frequency for abdominal ultrasound?
The size of the patient and the organ being examined
Where should the probe be placed to obtain a sagittal image of the liver?
On the ventral midline immediately caudal to the xiphisternum (marker pointing cranially)
How should the ultrasound beam be directed to examine the entire liver in the transverse plane?
The probe should be rotated 90 degrees and ‘fanned’ from cranial to caudal
What is the normal echogenicity and echotexture of the liver in cats and dogs?
Fairly uniform echogenicity and slightly coarse echotexture
What can CT images be reconstructed into?
CT images can be reconstructed into a sagittal, dorsal, or any oblique plane using a dedicated CT workstation or any DICOM viewing software.
What is the unit of measurement used in CT?
The unit of measurement used in CT is the Hounsfield unit (HU).
What is the range of Hounsfield units?
The Hounsfield units range from -1000 (air) to +4000 (compact bone).
What are the window width and window level used for in CT?
The window width and window level are used to highlight the tissue of interest in CT images.
What is the advantage of CT over radiography in terms of superimposition?
The lack of superimposition is an advantage of CT over radiography.
What is the advantage of CT over radiography in terms of contrast resolution?
The improved contrast resolution is an advantage of CT over radiography.
What is the advantage of multidetector technology in CT scanners?
Multidetector technology allows CT scanners to acquire multiple slices simultaneously and greatly increases the speed of CT image acquisition.
What can CT images be reconstructed in?
CT images can be reconstructed in different planes such as transverse, dorsal, sagittal, and oblique.
What can cause areas of marked hyperechogenicity that may shadow in the prostate?
Fibrosis, gas, or mineralisation
What is the appearance of the prostate in cases of prostatic neoplasia?
Enlarged, irregular and asymmetric shape, and heterogeneous echogenicity
What are the suggestive findings of a prostatic tumour?
Extension into the bladder neck or urethra, disruption of the prostatic capsule, and sublumbar lymph node enlargement
What diseases can show similar appearances to prostatic neoplasia?
Benign prostatic hyperplasia and prostatitis
Where are paraprostatic cysts located?
Outside of the prostatic capsule
How can paraprostatic cysts be distinguished from the bladder?
Careful examination of the bladder neck region
What imaging techniques complement each other when assessing the gastrointestinal tract?
Ultrasonography and radiography
Why should contrast radiographic procedures follow ultrasonography in the gastrointestinal tract?
Because barium causes attenuation of sound and degrades the ultrasound image
What are the main disadvantages of CT?
The main disadvantages of CT are the requirement for sedation or general anaesthesia and the use of ionising radiation.
Why is radiation protection important in CT?
Radiation protection is important in CT because the use of ionising radiation requires following radiation protection rules.
How does the contrast resolution of CT compare to that of radiography, ultrasound, and MRI?
The contrast resolution of CT is better than radiography, but not as good as ultrasound or MRI.
Why is MRI normally preferred for neurological examinations?
MRI is normally preferred for neurological examinations because its superior contrast resolution allows for a more detailed assessment of the brain and spinal cord.
What are the considerations when performing a CT study?
A CT study should be properly justified, based on an adequate prior clinical work up and a specific clinical question in mind.
What are some examples of good reasons for performing a CT study?
Good reasons for performing a CT study include investigating for the presence of a nasal mass, suspected vascular malformation, tumour staging, or compressive myelopathy.
What are some limitations of CT when examining the head and neck?
CT provides good assessment of the complex bony structures of the skull and can identify fractures and acute intracranial haemorrhages, but has limitations compared to MRI.
What are some advantages of CT in examining the head and neck?
CT is the imaging modality of choice for identifying skull fractures and provides good resolution of the fine bony detail in the head and neck region.
What does the ultrasound transducer do when the reflected ultrasound wave returns?
The ultrasound transducer distorts the piezoelectric crystal, which produces a voltage.
How long is a typical pulse of ultrasound emitted by the transducer?
A typical pulse of ultrasound emitted by the transducer is approximately 3 wavelengths long, which is approximately 1.5mm.
What percentage of time does the transducer spend producing ultrasound waves?
The transducer produces ultrasound waves for 1% of the time.
What are the three basic types of ultrasound probe?
The three basic types of ultrasound probe are linear, curvilinear and microconvex, and phased array.
What structures are linear probes limited to examining?
Linear probes are limited to examining more superficial structures, such as superficial intestinal loops and tendons.
What advantage do curvilinear and microconvex probes have for scanning under and between the ribs?
Curvilinear and microconvex probes have a curved footprint, which makes scanning under and between the ribs easier.
What is the ideal probe choice in terms of frequency?
The ideal probe choice is one that provides the highest frequency with adequate penetration.
What is the most commonly used display mode in ultrasound imaging?
The most commonly used display mode in ultrasound imaging is B-mode.
What is the preferred imaging modality for assessing neurological disorders?
MRI
Why is CT preferred over MRI for imaging bony lesions?
CT provides superior spatial resolution and is better suited for imaging bone.
What are some extracranial structures that can be evaluated using MRI?
Nasal disease, middle and inner ear disease, masticatory muscle myositis, retrobulbar masses, lymphadenopathies, salivary gland disease, and unknown soft tissue masses.
Why is MRI rarely used to image the thorax and abdomen in veterinary medicine?
There are movement artifacts caused by breathing and heartbeat, lower spatial resolution of images, long examination time, requirement for general anesthesia, and increased cost.
Which imaging modality is better suited for assessing soft tissues like the spinal cord and nerve roots?
MRI
What is the advantage of CT over MRI in terms of cost and examination time?
CT is less expensive and provides very fast examination times.
When is myelography not necessary in conjunction with MRI or CT studies?
Myelography is not necessary with MRI because of the ability to alter tissue contrast using different acquisition sequences.
Which imaging modality provides superior contrast resolution?
MRI
What is the most common type of bladder tumor?
Transitional cell carcinomas
Where are bladder tumors most commonly found?
In the region of the bladder neck
How can bladder ruptures be best diagnosed?
Using positive contrast cystography
Why can bladder ruptures be difficult to recognize with ultrasound?
Residual urine can remain in the bladder
Where are the ovaries located?
Caudal to the respective kidneys
What is the ideal time to perform pregnancy detection?
At least 30 days since the last mating
What are the normal findings of the uterine body in a non-pregnant bitch?
Up to 1cm in diameter, fairly homogenous, hypoechoic structure located between the bladder and colon
How can the uterus be distinguished from the small intestine in an ultrasound?
Lack of peristalsis, lack of intraluminal gas, and lack of the characteristic 5-layered appearance
What are some small abdominal structures/organs that can be evaluated using ultrasonography?
Adrenal glands, pancreas, lymph nodes
What are some challenges in identifying small abdominal structures/organs using ultrasonography?
Large breed dogs, obese patients, and gas within the GI tract can obscure visibility
Why is ultrasonography the preferred imaging modality for evaluating gastrointestinal wall layering and thickness?
It provides better visualization compared to abdominal radiographs, especially for smaller structures/organs
Why may uroliths not always be visible on abdominal radiographs?
They can be radiolucent
In which locations can uroliths be more difficult to identify with ultrasound?
Ureters or urethra
What is the recommended imaging modality for diagnosing portosystemic shunts and evaluating their morphology?
CT angiography
What limitations does abdominal ultrasonography have?
Poor specificity of lesions detected, hindrance of visibility due to GI tract content, decreased resolution in large/deep-chested dogs, limited visibility of cranial abdominal structures in large/deep-chested dogs
What is the preferred imaging modality for evaluating the morphology and function of the heart?
Echocardiography
What can cause more marked pyelectasia?
Pyelonephritis or ureteral obstruction.
When is dilation of the renal pelvis called hydronephrosis instead of pyelectasia?
When it is caused by an obstructive disease.
What are the possible causes of ureteral obstruction?
Calculi, structures, inflammation, and neoplasia.
How are renal calculi usually seen on ultrasound?
As hyperechoic foci casting a strong distal acoustic shadow.
Where are the adrenal glands located in relation to the kidneys?
Cranial and medial to the kidneys.
Which gland is usually easier to find, the left or right adrenal gland?
The left adrenal gland.
What shape does the left adrenal gland have in dogs?
‘Peanut’ shape.
What is the characteristic shape of the right adrenal gland in dogs?
‘Arrow’ shape.
What is ultrasound?
Ultrasound is a mechanical form of energy that travels in waves and is produced by the vibration of a crystal within the ultrasound transducer.
What is the frequency of ultrasound waves measured in?
The frequency of ultrasound waves is measured in hertz (Hz).
What is the wavelength of ultrasound waves measured in?
The wavelength of ultrasound waves is measured in millimeters (mm).
What is the velocity of ultrasound waves dependent on?
The velocity of ultrasound waves is dependent on the stiffness and density of the medium.
What is the average velocity of ultrasound waves in soft tissue?
The average velocity of ultrasound waves in soft tissue is 1540 m/s.
What is the audible range of sound frequencies for human beings?
The audible range of sound frequencies for human beings is 20 Hz to 20 kHz.
What is the main property of ultrasound waves that distinguishes it from other diagnostic imaging modalities?
Ultrasound is the only diagnostic imaging modality that does not use electromagnetic radiation.
What is the principle behind ultrasound wave energy transmission?
Ultrasound waves transmit energy by alternating regions of compression (high pressure) and rarefaction (low pressure) of the particles within the medium.
What are the paired arteries that leave just caudal to the renal arteries?
The paired testicular/ovarian arteries.
What determines the significance of a thrombus in the abdominal blood vessels?
The size and location of the thrombus.
What is the principle behind computed tomography (CT)?
CT uses X-rays and cross-sectional imaging technique.
What is the rotate-rotate geometry in CT scanners?
Both the X-ray tube and the detector array rotate around the patient.
What are the advantages of modern CT scanners with multiple detectors?
Faster image acquisition, reduced motion artifacts, and ability to perform CT angiography and cardiac imaging.
What contrast agents can be used in CT examinations?
Iodinated contrast agents.
In veterinary patients, when are CT examinations usually performed?
Under deep sedation or general anesthesia.
What are the imaging planes used in CT images?
The images are acquired in different planes.
What can also produce large lesions besides malignant tumours?
Benign tumours and nodular hyperplasia
What is the most common sign of malignancy in adrenal gland masses?
Identifying evidence of vascular invasion
What imaging technique is used to scan the bladder?
Transverse and longitudinal planes
How should the probe be moved when scanning the bladder in a longitudinal plane?
Slid or fanned from left to right
What is the best state of distension for scanning the bladder?
At least moderately distended with urine
What does the bladder wall appear as in ultrasound?
An echogenic double line
What can be mistaken for sediment, calculi or masses within the bladder?
Artefacts like reverberation, range ambiguity, side and grating lobes, and refraction
What might bladder wall thickening indicate in non-distended bladder?
An artefactual finding
What imaging modality is often used to distinguish true mediastinal lesions from lung pathology located towards the lung hilum?
Thoracic CT
What is one advantage of ECG-gated CT studies?
They eliminate the artifacts caused by cardiac motion.
Why is ultrasonography the imaging modality of choice for abdominal assessment?
It provides excellent soft tissue detail and is cheaper than other modalities.
What can limit the effectiveness of ultrasonography in large or deep chested patients?
The presence of a large amount of gas in the GI tract or fat in the peritoneal cavity.
What is CT angiography used for in abdominal studies?
To perform a detailed assessment of vascular structures during different phases.
What can be evaluated after an IV injection of iodinated contrast during a CT-IVU?
The ureters, mainly to investigate for ectopia, rupture, masses, obstruction, or strictures.
What imaging modality is preferred for assessing complex joints like elbows and tarsi?
CT
What is the basis of MRI as a cross-sectional imaging technique?
Strong magnetic fields and radio waves, instead of x-rays.
What imaging technique is useful for investigating bone metastases, multiple myeloma, and early vertebral osteosarcomas?
CT
What is CT more sensitive than radiography for detecting in terms of bone destruction?
Early signs of bone destruction
What infectious disease involving the vertebrae can CT be a good technique for assessing?
Discospondylitis
What can be detected in the late stage of early discospondylitis?
New bone production and fusion of the two adjacent vertebrae
What imaging modality is considered the optimum for evaluating peripheral nerves?
MRI
What imaging technique is very good for evaluating bones but more limited for assessing soft tissue structures?
CT
When may it be necessary to perform CT myelography in order to identify a lesion explaining neurological signs?
If a lesion cannot be identified with CT alone
What does CT myelography provide a better assessment of in terms of lesions?
Extradural lesions, intradural extramedullary lesions, and intramedullary lesions
