Visualising the Bowel Flashcards
(33 cards)
What type of radiation does X-ray imaging use?
A penetrating form of electromagnetic radiation.
In what patient positions can X-rays be taken?
Supine or erect.
What are the two main directions X-rays can be taken from?
Postero-anterior (PA) and antero-posterior (AP).
Which is more common: PA or AP X-ray?
PA (postero-anterior).
Why is PA X-ray preferred over AP?
Because the closer an object is to the film, the less prone it is to magnification and blurring.
What do X-rays produce?
Projections.
Why are at least two X-ray projections needed?
To determine anatomical placement, as images are composed of overlapping shadows from stacked tissues.
What color does air appear on an X-ray?
Black.
What color does fat appear on an X-ray?
Dark gray.
What color does water (and soft tissue) appear on an X-ray?
Light gray.
What color does bone appear on an X-ray?
White.
What color does metal appear on an X-ray?
Very white.
What type of agents are used in fluoroscopy?
Contrast agents like barium or iodine.
Are barium and iodine radio-lucent or radio-opaque?
Radio-opaque.
What contrast agents are used in angiography?
Barium or iodine.
Are the contrast agents used in angiography radio-opaque or radio-lucent?
Radio-opaque.
What does a CT scan use to generate images?
X-rays projected onto a detector.
What is sent to the computer from the CT scan?
A numerical value based on tissue radiodensity.
What is a tomogram?
A “slice” image produced by CT.
How are CT radiodensities displayed?
As shades of gray, assigned a Hounsfield Unit (HU).
Can CT images be enhanced? If so, how?
Yes, with contrast agents.
In what planes can digital CT images be viewed?
Multiple planes.
What are the main types of MRI sequences?
T1, T2, Fat Saturated, and Vascular Contrast images.
In which MRI sequence does fluid appear bright?
T2-weighted.
