The Abdomen

The Abdomen: Scan Technique

CT is superior for detecting abnormal nodes in the upper retroperitoneum and inferior mediastinum. It provides visualization of enlarged nodes in the mesentary and hilar areas. Evaluation of extranodal tissue in the liver, kidney, bone, and lungs during a single examination is possible using current CT technology. (Figures 13-16)

Imaging of the Abdomen (Figure 13)

Contrast enhanced CT of the abdomen. The images displayed above are moving from superior to inferior. Note the concentration of contrast in the aorta.

Imaging of the Abdomen (Figure 14)

Continuation from Figure 13 moving distally. Note the level of the kidneys. The left kidney appeared in Figure 13 but the right kidney does not appear until figure 14. This is a normal appearance.

Imaging of the Abdomen (Figure 15)

Continuation of Figure 14 moving distally. The left renal artery is clearly displayed.

Imaging of the Abdomen (Figure 16)

Continuation of Figure 15 moving distally. Note the excellent concentration of contrast still within the aorta. There is a clear delineation of the descending aorta from the inferior vena cava.

Helical CT scanning, with the rapid acquisition of a volumetric data set, has resulted in a dramatic increase in sensitivity and specificity in the evaluation of hepatic abnormalities. The appropriate contrast enhancement, intravenous contrast and oral contrast, is necessary when imaging the abdominal organs, especially the liver. With helical CT, complete scanning of the liver can be accomplished in less than 20 seconds. Multiple scans through the liver can be performed corresponding to various phases of hepatic enhancement including arterial, venous and equilibrium as well as delayed phases. Multiphase CT can result in increased lesion detection and the pattern of enhancement on these different phases can result in lesion characterization. Since the entire liver can be scanned in a single breath hold, misregistration artifacts caused by voluntary or involuntary motion are reduced or eliminated. Additionally, thinner slices can be acquired and reconstructed at finer intervals when compared with conventional CT. Therefore, the effect of partial volume averaging of small lesions is reduced with resultant improvement in lesion detection and characterization.