CT Abdomen - Read Like A Radiologist
Practicing viewing, describing, and interpreting abdominal CT scans the way a radiologist does. A hands-on preparation for your teaching session.
Densities & scan phases
Before you interpret cases, it is essential that you master the 'language' of CT: what do the densities (‘shades of gray’) on a CT image mean, and why are multiple scan phases performed?
CT densities: what are you actually looking at?
Every tissue absorbs X-ray radiation to a different degree. This is expressed in Hounsfield units (HU). By knowing the HU value of a structure — or estimating it from the gray value — you can distinguish between fat, fluid, blood, parenchyma, and air (Fig. 1). Has your knowledge of X-ray radiation, HU values, and CT technique faded? Then read the module X-ray/CT technique.
Question 2a. Scroll through the CT abdomen examination (Fig. 2), in which 6 circles have been placed on various structures.
For each circle, note: (1) the estimated HU value, (2) the tissue type, (3) an example of where else you might encounter this tissue type. Use Figure 1 as an aid.
Scan phases
A CT abdomen is not always performed in a single phase. Depending on the clinical question, a specific protocol is selected. Understanding the different phases — and the vascular anatomy associated with them — is essential for recognizing pathology and for understanding why pathology is more visible in some phases than in others.
Question 3.
Look at the four CT phases in Figure 3.
a. Which scan phase do you see here? What features do you recognize it by?
b. Note 3 aspects/findings that you can assess much better on a CT examination with intravenous contrast.
c. Provide a clinical question for each phase for which you specifically need that phase.
Answers: see next page
Text & Illustrations
drs. A. van der Plas (MSK radiologist Maastricht UMC+)
05/10/2026