Faculty Bibliography

PURPOSE: To evaluate thin-section computed tomography (CT) performed during the corticomedullary and nephrographic phases of contrast material enhancement in the characterization of renal masses. MATERIALS AND METHODS: A prospective study of 30 patients was undertaken with CT to characterize 31 'indeterminate' renal masses. In all patients, 5-mm-thick, contiguous, high-tube-current (320-340-mA) scans were obtained through the kidneys before (axial mode), during (helical mode, 25-second delay, corticomedullary-phase images), and after (axial mode, 120-second delay, nephrographic-phase images) administration of a 117-second biphasic injection of intravenous contrast material. RESULTS: Eight of 16 neoplasms measured less than 20 HU on CT scans obtained without contrast material enhancement; measurements of two of these corresponded to 'cyst attenuation' during the corticomedullary phase. Enhancement of 10 HU or greater was demonstrated in 11 neoplasms during the corticomedullary phase and in all neoplasms in the nephrographic phase. No enhancement was seen in 15 radiologically benign cysts. Both renal neoplasms and normal renal cortex demonstrated significantly greater enhancement in the nephrographic phase compared with that in the corticomedullary phase (P = .0002 and P < .0001, respectively). CONCLUSION: Enhancement of renal neoplasms is time dependent and may not be evident in hypovascular tumors analyzed during the early corticomedullary phase. Reliance on absolute CT attenuation measurements, without use of internal standards as controls, may lead to misdiagnosis of neoplasms as cysts

OBJECTIVE. The purpose of this study was to compare the degree and timing of peak hepatic enhancement, optimal scanning intervals, and optimal delay times of moderate-rate uniphasic and biphasic contrast material injection protocols for hepatic helical CT. MATERIALS AND METHODS. One hundred fifty patients were randomized into three injection protocols, receiving 42.3 g iodine (150 ml iothalamate meglumine) delivered using 3 ml/sec uniphasic, 2 ml/sec uniphasic, or biphasic (3 ml/sec [50 ml], 1 ml/sec [100 ml]) technique. Statistically fitted aortic and hepatic enhancement curves were generated from dynamic incremental CT data for each patient. Protocols were compared by maximum hepatic enhancement, and contrast enhancement indices were modeled for a 38-sec helical acquisition. RESULTS. The 3 ml/sec and 2 ml/sec uniphasic protocols produced higher peak hepatic enhancement (64 +/- 15 H and 62 +/- 15 H [mean +/- 1 SD]) than the 3 ml/sec biphasic protocol (52 +/- 10 H; p < .001). Contrast enhancement indices for the 3 ml/sec uniphasic and 2 ml/sec uniphasic protocols (385 +/- 398 H/sec and 397 +/- 412 H/sec) were significantly greater than the index for the 3 ml/sec biphasic protocol (123 +/- 194 H/sec; p < .0001) at a 50-H threshold. Optimal scan delay times were 50 +/- 8, 75 +/- 7, and 119 +/- 8 sec, respectively, for the 3 ml/sec uniphasic, 2 ml/sec uniphasic, and 3 ml/sec biphasic techniques. CONCLUSION. The moderate-rate uniphasic injections studied provided greater hepatic enhancement throughout the helical acquisition without requiring the prohibitively long delay time necessitated by the moderate-rate biphasic injection. These findings differ from prior results that showed that a uniphasic injection may provide comparable levels of hepatic enhancement when compared with a high-flow-rate biphasic injection

CT plays an important role in the evaluation of patients with suspected colonic inflammation. High-resolution, thin-section imaging of the gastrointestinal tract allows assessment of both the intraluminal and extraluminal components of colonic disease, thereby enabling radiologists to detect and stage colonic pathology accurately. In addition, CT can be used to guide percutaneous drainage of abscess collections, often obviating the need for surgical intervention. This article describes CT techniques for diagnosing inflammatory diseases of the colon as well as the typical CT appearances

PURPOSE: Two percent glutaraldehyde on colonic mucosa may result in a toxic colitis, and the clinical features may mimic those of colonic ischemia. The study was performed to determine the radiologic appearance of glutaraldehyde-induced toxic colitis. MATERIALS AND METHODS: A retrospective review was performed with the clinical and imaging findings in four patients with glutaraldehyde-induced colitis seen during a 6-year period. RESULTS: Patients developed a self-limited syndrome of cramps and abdominal pain, tenesmus, and rectal bleeding within 48 hours of uncomplicated sigmoidoscopy or colonoscopy. Sample cultures excluded enteric pathogens. Computed tomography (CT) demonstrated circumferential thickening of the colonic wall in a left-sided distribution in all patients. Heterogeneous mural enhancement (target-sign appearance) was noted in two patients. Follow-up CT studies confirmed resolution of mural wall thickening with conservative management. CONCLUSION: The clinical and radiologic features of glutaraldehyde-induced toxic colitis may mimic those of colonic ischemia. This complication should be suspected in patients who develop hemorrhagic colitis immediately after undergoing colonoscopy