Abdominal CT Flashcards
How are CT images made?
- xrays from multiple sources mounted on a gantry are sent through the patient in axial slices
- attenuation of the xrays is measured by detectors mounted on opposite side of gantry
- data is analyzed by computer to generate a cross sectional image along the slice
What are the detectors in a CT scan measuring?
Attenuation that is summed from the multiple angles from the multiple xray sources on the gantry. Attentuation is measured in hounsfield units, which is an arbitrary unit with water being 0 and everything being measured relative to water.
What is xray attenuation?
The degree to which the tissue absorbs the xray energy. Tissue that completely absorbs xrays (bone, metal) appear totally undeveloped to the detector (white). Tissue that lets all xrays pass through appears black (air). Anything in between is on a gray scale.
What is the purpose of giving contrast?
It increases the contrast of the tissue b/c tissue absorbs the contrast for a temporary period of time before the contrast is excreted in feces or urine. This allows for greater visualization of the tissue.
- When IV contrast is given, what is the agent that causes the contrast to appear on CT?
- What is the path it follows in the body from injection?
- How is it excreted?
- What would you look at on a CT image to determine if IV contrast had been given?
- This can only be given to patients who have normal […] function
In some patients with diminished kidney function, contrast can cause nephropathy
- What is the agent in oral contrast that allows for visualization?
- Why is this given?
- When is it given if you want to see the colon?
- What would you look at on CT to determine if oral contrast had been given?
How do you know that you’re in the abdomen from a CT stack?
Where is the stomach on CT image?
Under left hemidiaphragm between liver and spleen
Where is the spleen on CT?
What organ is shown? Label image.
What organ is shown? Label image.
How can you tell that you’ve entered the upper abdomen?
- Where is the pancreas located in the abdomen?
- What is its relationship to the stomach, IVC, aorta, kidney, and splenic vein?
As you move inferiorly in CT, how does the view of the pancreas change?
Head of pancreas more visible as you move inferiorly, less of tail and body visible
What organs are seen in the anterior pararenal space?
If a person has pancreatitis, how would their CT image appear differently than a normal person?
What landmarks tell you you’re in the lower abdomen on CT?
What is a coronal image most useful for?
What is a saggital image most useful for?
