Medical Imaging Flashcards
Which uses more ionising radiation - CT or MRI?
CT
Give x2 examples of diagnostic imaging which do not use ionising radiation.
Ultrasound and MRI.
Approximately what percentage of background radiation exposure is from ionising sources?
15%
What affects the attenuation of x-rays?
The type of tissue
How does air appear on the x-ray?
Black
How does soft tissue appear on the x-ray?
Grey
How does bone appear on the x-ray?
White
How does fat appear on the x-ray?
Black
How does metal appear on the x-ray?
White
Which are the two commonly used contrast agents?
Barium and iodine
Why do we use a contrast agent in x-rays?
To enhance the differences between tissues of similar densities.
How is CT different to X-ray?
CT can differentiate between soft tissue and water.
Which are the three CT windows?
Soft tissue, bone and lung windows
What are the two main risks for using contrast agents?
Kidney damage and allergic reactions.
Do ultrasound scans use x-rays?
No.
How do MRIs work?
The MRI is made up of a strong magnet which is supercooled with liquid helium. Radiowaves are transmitted into the patient and interact with protons (water) in the patient’s body.
How would fat appear in a CT vs. MRI?
CT = Black, MRI = White.
How would air appear in a CT vs. MRI?
Both would appear black.
How would fluid appear in a CT vs. MRI?
CT = Dark grey MRI = Black
How would bone marrow appear in a CT vs. MRI?
CT = Grey MRI = White
What is the difference in the way bones appear in CT vs MRI?
CT = White MRI = Black
What is PET?
Positron emission tomography = detects metabolic changes rather than structural changes. Particularly used in locating cancer.
In relation to the anterior and posterior positions, what do dorsal and ventral relate to?
Dorsal = posterior Ventral = anterior
What are the upper and lower surfaces of the foot called?
The dorsal and plantar surfaces.
Dorsal = upper
Plantar = lower
