Chapter 68 - Radiography Flashcards
What condition might cervical spinal radiographs suggest in ataxic horses?
Spinal cord compression
Which imaging technique is particularly sensitive for detecting large colon enteroliths?
Digital abdominal radiographs
What component of the x-ray tube is responsible for emitting x-rays?
Anode
What is the term for the area on the anode that is struck by electrons?
Focal spot
Which factor is adjusted to change the number of x-rays produced?
Milliampere (mA)
Exposure time (s)
What is the main advantage of fast intensifying screens in radiography?
Higher sensitivity to x-rays
Which digital radiography system uses photostimulable phosphors?
Computed radiography
Which setting controls the maximum energy of the electrons accelerated in an x-ray tube?
kVp
What happens to the latent image on photostimulable phosphors over time?
It disappears
What is the purpose of collimating the primary x-ray beam?
Reduce radiation exposure
What can radiography diagnose in the lumbar spine?
Degenerative lesions
What is an important aspect to consider when using screen-film radiography?
Processing must be precise
Which imaging technique may be required to confirm abnormalities found in cervical spinal radiographs?
Myelography
Which type of radiographic film is most suitable for high-detail examinations?
Slow/detail systems
What is the main advantage of digital radiography over screen-film systems?
It allows for post-exposure image manipulation
How does the housing of the x-ray unit contribute to safety?
It is lead shielded to protect operators
What is the role of the intensifying screen in screen-film radiography?
To convert x-rays into visible light
What must be done to the PSP after it has been used to capture an image?
To convert x-rays into visible light
Which body region is typically more challenging to radiograph?
Thoracolumbar spine
What is the effect of using a high mAs setting in radiography?
Increased exposure time
Which factor influences the resolution of an x-ray image?
A) Cathode type
B) Focal spot size
C) Film speed
What do higher kilovoltage (kVp) settings provide in x-ray imaging?
More x-ray penetration
What is the primary function of flat-panel detectors (FPDs) in digital imaging?
To convert x-ray energy into an electronic signal
What file format is standard for medical imaging data?
DICOM
How does pixel size affect image resolution in digital radiography?
Smaller pixel size increases resolution
What does PACS stand for in medical imaging?
Picture Archive and Communication System
How do digital radiographs compare in dynamic range to screen-film systems?
Digital radiographs have a vastly superior dynamic range
What technology is used in fluoroscopy to produce real-time images?
Image intensifier
What is one major advantage of fluoroscopy?
Real-time observation of dynamic studies
Which component in fluoroscopy converts x-ray energy to light?
Input fluorescent screen
What does the term “dynamic range” refer to?
The ability to produce diagnostic images across exposure values
Which scintillator material is used in indirect digital FPD systems?
Gadolinium oxysulfide
What is a limitation of fluoroscopy systems?
Limited penetration and resolution
Which factor should be considered to avoid distortion in radiographic images?
Keeping the tube and cassette parallel
How many orthogonal projections should each study contain at a minimum?
2
What is the simplest type of contrast medium used in radiography?
Negative contrast medium
What is the composition of a 60% w/v barium sulfate solution?
A) 60 g of barium sulfate in 40 mL of water B) 60 g of barium sulfate in 100 mL of total volume C) 40 g of barium sulfate in 60 mL of water
B) 60 g of barium sulfate in 100 mL of total volume
hat is a significant risk of using ionic contrast agents in myelographic studies?
A) Hypotension B) Seizures and death C) Allergic reactions
B) Seizures and death
Which iodinated contrast agents are preferred for arthrograms?
Nonionic agents
What type of contrast agent is barium sulfate?
Positive contrast agent
What principle does ALARA stand for in radiation safety?
A) As low as reasonably achievable
What is the main source of radiation exposure for veterinary staff during x-ray procedures?
B) Scatter radiation
How can distance help reduce radiation exposure?
It decreases the amount of scatter radiation received
Why is collimation important in radiography?
It reduces patient dose and scatter radiation
What does “border effacement” refer to in radiographic interpretation?
Loss of margins between structures of similar opacity
What type of radiographic patterns indicate aggressive bone processes?
Irregular or indistinct margins
What type of contrast study involves adding gas to separate structures?
Negative contrast study
What is a potential complication of using room air as a negative contrast medium?
Gas embolism
How does a nonionic iodinated contrast agent differ from an ionic agent?
It does not dissociate in solution
How do kVp and mAs settings affect radiographic image quality?
Higher kVp increases exposure and scatter, reducing contrast; higher mAs darkens images but increases tissue interactions.
What is a key consideration when evaluating nondisplaced stress fractures?
They may not be evident until days later
What happens to the image contrast when kVp is decreased?
Image contrast increases, resulting in more distinct blacks and whites
What is the effect of scatter radiation on image quality?
Scatter radiation degrades image quality by reducing contrast and obscuring details.
What is the purpose of grids in radiography?
Grids reduce scatter radiation reaching the film or digital receiver, improving image quality.
What is the recommended grid ratio for techniques with kVp below 90?
A grid ratio of at least 8:1 is recommended.
Why are grids rarely used for equine distal limb imaging?
Distal limbs are usually less than 10 cm thick, making alignment difficult.
How is overexposure corrected in digital systems?
By decreasing mAs by half or kVp by 10-15%, and then re-imaging if necessary.
What is quantum mottle?
Quantum mottle is the grainy appearance in underexposed digital images due to low signal-to-background noise.
How can motion artifacts be minimized during imaging?
Use sedation to minimize patient movement, stabilize the x-ray tube, and select the highest mA with the lowest exposure time.
What do grid artifacts appear as on a radiograph?
Grid artifacts appear as white lines parallel to the lead strips when misaligned.
What are the five basic radiographic opacities in order from least to most dense?
Gas, fat, soft tissue/fluid, bone/mineral, and metal.
What artifact results from the incorrect alignment of a grid?
It causes visible white lines across the image.
How does increasing mAs affect the radiographic image?
It results in a darker image with less tissue interaction compared to increasing kVp.
What is the primary reason for using the highest mA and lowest time possible during imaging?
To minimize the risk of motion artifacts due to shorter exposure times.
Figure 68-1. Basic x-ray tube configuration with a rotating anode; the drawing is not to scale.
Figure 68-2. Radiographic equipment: (A) 400-speed film-screen equipment. (B) Computed radiography cassette and imaging plate. (C) AGFA computed radiography processor. (D) Sound-Eklin Mark IIG direct digital radiography system. Image plate sends the x-ray information transformed into electric signal to a computer for display.
Figure 68-3. Diagram of the internal components of computed radiography versus indirect and direct flat-panel detectors.
Figure 68-4. The large animal fluoroscopy unit from General Electric, at the Michigan State University Teaching Hospital. The x-ray tube is capable of producing high kVp and mA technique and is seen to the left of the stocks. The image intensifier, to the right, captures the x-ray information and is coupled either to a closed circuit video system or digital detection system for real-time display. The acquisition station seen to the left enables the user to see displayed images and capture them as they are taken.
Figure 68-5. (A) Caudocranial projection of a stifle with incorrect angle of the x-ray beam relative to the joint, resulting in artefactual narrowing of the medial and lateral femorotibial joint space. (B) Caudocranial projection of the same stifle with correct angle of the x-ray beam, resulting in a normal appearance to the joint.
Figure 68-6. (A) The lateromedial radiographic view of the stifle of a 3-year-old Thoroughbred gelding simulating high-mAs, low-kVp technique with film. Note that though the contrast within the bone is great, allowing visualization of trabecular pattern, the large contrast of the image makes soft tissues less visible. (B) The same radiographic view simulating high-kVp technique. Note the large numbers of grays allowing visualization of soft tissues, differentiation from fat, and the relative lack of contrast within bony structures. Note that the relative brightness of the two images is similar.
Figure 68-7. (A) A lateromedial projection of the caudal cervical spine without a grid. Note the relative poor contrast between the bone and adjacent soft tissues. (B) A lateromedial projection of the same spine, but with a 12 : 1 grid. The contrast between bone and soft tissues is improved compared with A.
Figure 68-8. Clipping artifact with a digital radiography system. The soft tissues cranial to the stifle joint are rendered black (indicated by arrow) from overexposure in this region. Note that the adjacent anatomy is normally displayed and the junction with the clipped area is abrupt.
Figure 68-9. (A) Dorsopalmar metacarpal projection using very low kVp/mAs settings showing severe quantum mottle artifact from underexposure. (B) Same metacarpus, but with moderately increased kVp/mAs settings. Note that the image is improved, but mottle remains over the thick midmetacarpal region. (C) Same metacarpus, but with correct kVp/mAs settings. Note that mottle is no longer present.
Figure 68-11. White lines travel across the image from a decentered grid. If lines occur in a regular, very closely apposed fashion, grids are usually the culprit. Note the irregular white line (arrow) along the upper right side of the image, representing hair in the cassette, as well
Figure 68-12. The same dorsoplantar projection of the tarsus processed differently at the acquisition station. The left most image (A) is properly processed, with optimal contrast and resolution. Note that the other images may be made too light (B) or too dark (C) If unsharp masking is reduced (D), the image will lose the well-defined margins of bony structures.
resulting in well-defined white lines on the film where it was not completely exposed. Scratched screen artifacts can be differentiated from scratched film by touching the radiographic film. With a film scratch, a divot or physical defect can be felt in the emulsion, whereas with a scratched screen, unexposed emulsion remains on the film (no defect is felt).
Dirt Artifacts
Dirt or debris within the radiographic cassette between the intensifying screen and film blocks light emitted from the radiographic VetBooks
Figure 68-10. Lateral projection of a cervical spine, magnified to demonstrate the normal grid lines present when using a stationary 12 : 1 grid (arrows).
Figure 68-13. Dirty light guide artifact with a computed radiography (CR) system. Two parallel white lines (arrow) seen along the right side of the image are caused by debris on the light guide within the CR image processor.
In esography what contrast do you use? in case of perforation what do you use instead?
Barium sulfate suspension 60% w/v, orally, volume dependent upon patient swallowing; not to be used if esophageal perforation is suspected (use iodinated contrast instead)
In esophagography what are the timmings for image take?
take lateral cervical and thoracic films 5 and 15 sec after swallowing, respectively
In a foal with suspected gastric ulceration or obstruction of SI what constrast do you use?
5 mL/kg 30% w/v barium sulfate suspension through nasogastric tube; not to be used if gastrointestinal perforation is suspected (use iodinated contrast instead; ionic form not recommended if patient is dehydrated)
In foals with suspected gastric obstruction what is the fast preparation
4–12 h fast prep, (4 h if <2 weeks old), standing right lateral, recumbent bilateral and ventrodorsal films, survey before contrast, then films at time
0,
30 min,
2 h,
then 2 h intervals until contrast reaches small colon
In case of foal with suspected rectal stricture, sectional hypoplasia, or mass what technique do you use? name the tx, constrast and way of administration
Barium colonogram: 20% w/v barium sulfate suspension, volume is patient specific but should begin at approximately 5–10 mL/kg; not to be used if rectal perforation is suspected
Clean rectum of as much feces as possible, administer contrast through rubber tube with catheter tip or largest Foley catheter available (up to 26 F available)
Dacryocystorhinography is used when?
Chronic epiphora, orbital trauma, chronic nonresponsive conjunctivitis, proptosis of third eyelid
Dacryocystorhinography is used what is the contrast?
Nondiluted ionic or nonionic iodinated contrast, approximately 5 mL per injection, or until contrast is seen at the medial canthus of eye
how do you perform dacryocystorhinography?
Catheterize nasal puncta, take film as injecting the contrast (or duct may not be uniformly filled), nasolacrimal duct better resolved with CT, but large abnormalities can be seen on radiographs
sialography consists in what?
In catheterizing the salivary duct of interest, preferably watched as injected with fluoroscopy, but orthogonal views taken after injection are an alternative, films repeated if complete filling is not seen, iatrogenic rupture of duct and/or salivary gland are a potential complication with Nondiluted ionic or nonionic iodinated contrast,
20 mL/kg, or until sufficient back pressure
is felt or contrast leaks around catheter
What are the indications of sialography?
Swelling or tubular structure suspected associated with salivary system, abnormal ptyalism or discharge localized to a single salivary duct
Fistulography is performed with which type of contrast?
Nondiluted ionic or nonionic iodinated contrast, volume is study specific, injected until contrast begins to leak around catheter or sufficient back pressure in a draining tract or sequestrum
Arthrography/bursography/tenography
Nondiluted nonionic iodinated contrast for bursa or tendon sheath, diluted 1 : 1 with saline for arthrogram, volume is joint or bursa specific; distend the structure in question until slightly distended and mild back pressure is felt
Selective angiography is used in laminitis and is used with what type of contrast?
Nondiluted (for radiography) nonionic iodinated contrast injected into specified artery or vein (see right), continuous infusion with pressure injector or single 20 mL injection, 1 : 1 diluted for CT in common digital artery or medial or lateral palmar digital vein infusion for laminitis, and medial palmar artery infusion reported for CT
Excretory urography (foal only) is used with which contrast?
880 mg I/kg of ionic or nonionic iodinated contrast given intravenously as a rapid bolus; this should not be done in dehydrated patients, and may cause contrast-induced nephrotoxicity
how do you perform excretory urography (foal only)
For ectopic ureters, prep bladder with pneumocystogram through urethral catheter, take films at time of injection, 5 min, 15 min, and 30 min postinjection, more films may be required if poor renal function
Excretory urography (foal only) is used in which clinical cases?
Suspected ectopic ureters, suspected uroretroperitoneum or peritoneum, renal azotemia
what are the projection/views used in pastern/PIP?
1) Lateromedial
2) Proximal 30-degree dorsopalmar/-plantar
what are the projection/views used in P3?
1) Lateromedial.
2) Proximal 60-degree dorsopalmar
3) Flexed proximal 60 degree, D45°MPLO and D45°LPMO
what are the projection/views used in navicular?
1) Lateromedial
2) Proximal 65-degree dorsopalmar
3) Flexed 45- to 70-degree (to cassette) palmaroproximal palmarodistal (skyline)
what are the projection/views used in the canoon bones MCIII and MTIII, II, III, IV?
1) Lateromedial
2) Dorsopalmar/-plantar
3) D45°LPMO and D45°MPLO
what are the projection/views used in the knee/carpus?
1) Lateromedial
2) Dorsopalmar
3) D45°LPMO and D45°MPLO
what are the projection/views used in the hock/tarsus?
1) Lateromedial
2) Dorsoplantar
3) D35°LPMO and P35°LDMO
what are the projection/views used in the stifle?
1) Lateromedial
2) Caudolateral 45- to 60-degree craniomedial oblique
what are the projection/views used in the shoulder?
1) Mediolateral
2) Cranial 45-degree medial caudolateral oblique
what is the projection for thorax?
Lateral views centered:
1) Cranioventral
2) Caudoventral
3) Caudodorsal (usually × 2)
4) If needed, craniodorsal
what are the projection/views used in the elbow?
1) Mediolateral
2) Craniocaudal
what is the projection used in the pelvis?
Ventrodorsal; if standing, 10- to 25-degree caudal
Lateral in ponies and miniatures
what is the projection for skull and teeth/nasal sinuses?
1) Lateral
2) Dorsoventral
3) Dorsal (maxilla) or ventral (mandible) 30-degree lateral obliques
what extra projections of skull/teeth/nasal/sinus might be required 1) Lateral
2) Dorsoventral
3) Dorsal (maxilla) or ventral (mandible) 30-degree lateral obliques?
1) Intraoral dorsoventral (maxilla) or ventrodorsal (mandible)
2) Obliques for temporomandibular joint
In the case of the fetlock beside the Proximal 20 degree, D45°LPMO and D45°MPLO?
1) Flexed lateromedial
2) Flexed D45°LPMO and D45°MPLO
3) Flexed dorsoproximal to dorsodistal (skyline)
what are the obliques used in PIP joint projections?
Proximal 30 degree, D45°LPMO and D45°MPLO
what is the patellar skiline name of projection?
Flexed proximal 60- to 70-degree dorsoproximal dorsodistal (patellar skyline)
what are the oblique views required for knee/carpus?
1) Flexed lateromedial
2) Flexed dorsoproximal to dorsodistal (skyline): 35-degree distal row of carpal bones, 55-degree proximal row, and 85-degree distal radius
what are the extraordinary projections for hock/tarsus?
1) Flexed lateromedial
2) Flexed 65-degree proximal plantaroproximal plantarodistal (skyline)
what is the name of the skyline of the hock?
Flexed 65-degree proximal plantaroproximal plantarodistal (skyline)
