Medical Imaging Flashcards
What is radiology?
A branch of medicine concerned with the use of radiant energy or radioactive material in the diagnosis and treatment of disease
What is the difference between a radiologist and a radiographer?
A radiologist is a doctor who interprets images whereas a radiographer is someone who is trained to take the images
What is interventional radiography?
Medical sub-specialty of radiology utilising minimally-invasive image guided procedures
Give an example of invasive radiology
Angioplasty, insertion of a balloon into a vein or artery to widen it
How does an X-ray create an image?
When the beam passes through the human body, some of the X-rays are absorbed or scattered producing reduction of the beam
What is attenuation?
the reduction of the amplitude of a signal, electric current, or other oscillation
How does different tissues effect attenuation?
The higher density of tissue causes more attenuation so will show up as lighter grey or white on an X-ray
What are the five X-ray densities?
Air-Black Fat-Dark grey Soft tissue- Grey Bone-Light grey Metal-White
Why is it important to take images on multiple planes?
The fracture,break and dislocation may be hidden by one viewpoint
What is used to prevent radiation on certain body parts?
A metal screen, used primarily to stop radiation meeting the ovaries and testes
How would you take an image of a patient’s heart?
Posteriarly to avoid magnification of the heart
What is mammography?
Specific type of X-ray that uses low dosages which is designed for images of the breast
What is fluoroscopy?
Type of medical imaging that shows a continuous X-ray image on a monitor
When is fluoroscopy used?
When there is a need for real-time examination
Give an example of when fluoroscopy is appropriate
Implants during surgery, viewing movements of contrast agents
How does fluoroscopy differ from a regular X-ray?
The image is displayed on a fluorescent screen
What is angiography?
X-ray technique used in the examination of the arteries, veins and organs to diagnose blockages
What is the process of an angiograph?
A thin tube is inserted into an artery or vein, then a contrasting agent is injected to make the blood vessels visible on the X-ray image
What is tomography?
A method that produces images of single tissue plane
What does CT stand for?
Computed tomography
What does CAT stand for?
Computerized axial tomography
What is a CAT scan?
Radiologic imaging that uses a computer to generate an image of the tissue density in a slice of the patient
How should you envision yourself when seeing CAT scan?
The patient is on their back and your looking from their feet to their head
What are the advantages of CAT scans?
Fast, readily available, good imaging of bony structures abdomen and lungs
What are the disadvantages of a CAT scan?
High radiation dose, not so good at imaging soft tissue
What is scintigraphy
Radioisotopes attached to drugs that travel to a specific organ or tissue are taken internally and the emitted gamma radiation is captured by external detectors to form two-dimensional images in a similar process to the capture of x-ray images
What is the most commonly used radionuclide?
Technetium or 99mTc
What does the term metastable mean and what does this allow?
The radionuclide atom has two basic energy states, as the atom transforms from the high-energy state to the low-energy state, it emits a quantum of energy in the form of a gamma ray
What is single photon emission CT (SPECT)?
A scintigraphic technique whereby the the computer can detect subtle lesions overlain by other active structures
How can a SPECT scan be improved?
Fusing it with a CT scan, this improves sensitivity and specificity
What is a positron emission tomography (PET) scan?
A combination of computed tomography and scintillation
How does a PET scan work?
An isotope is attached to a biological compound to form a radio-pharmaceutical, which is injected into the patient to from a 3D image
What are the advantages of scintigraphy nuclear medicine?
Good functional information
Good localization of pathology
What are the disadvantages of scintigraphy nuclear medicine?
High radiation dose
Not so good at differentiating between different pathologies
What is a magnetic resonance imaging (MRI)?
A form of imaging that uses a powerful magnetic field and radiofrequencies to produce detailed images of the body’d internal structures
How is the imaged created in an MRI?
When the radio signal is turned on, the energy is absorbed by different atoms is reflected back out of the body
What are the three levels of signal intensity in a MRI?
High- white
Intermediate- grey
Low- black
What are the two basic types of MRI images?
T1 and T2 weighted images
Which type of MRI allows the image to see fat and water?
T2-weighted images
Which type of MRI is better at identifying a tumour?
T2
What are the advantages of MRI?
Gold standard of imaging
No radiation
Good localization of pathology
Good differentiation between pathologies
Excellent soft tissue imagine
What are the disadvantages of MRI?
Strong magnet
Not so good showing anatomy of bones
Cost
Long duration of scanning
Need for anaesthesia in younger children/uncooperative patients
Advantages of ultrasound?
Safe
No ionizing radiation
Relatively inexpensive
Disadvantages of ultrasound?
Highly operator dependent
Structures surrounded by bone cannot be seen
Cannot be used for some tissues due to attenuation
When should radiation be completely avoided?
In pregnant woman
