Faculty Bibliography

PURPOSE: To determine the effects of cyst diameter and location (intrarenal, exophytic), renal attenuation, section collimation, and computed tomographic (CT) interscanner variability on renal cyst pseudoenhancement in a phantom model. MATERIALS AND METHODS: A customized anthropomorphic phantom was designed to accept 40-, 140-, and 240-HU renal inserts containing intrarenal and exophytic 7-, 10-, and 15-mm cysts. Each phantom and insert were scanned with five different helical CT scanners by using 1.0-1.5-mm, 2.50-3.75-mm, 5.0-mm, 7.0-8.0-mm, and 10.0-mm section collimation. Means and SDs of CT number measurements were obtained for each cyst within each variably 'enhanced' renal insert. Mixed-model analysis of variance accommodating heteroscedasticity of data was used to assess the effect of scanner type, section collimation, and cyst diameter on cyst attenuation. RESULTS: Pseudoenhancement (range, 10.3-28.3 HU), observed by using effective section collimation equal to or less than 50% of cyst diameter, occurred in 34 (38%) of 90 intrarenal cyst measurements. Pseudoenhancement was observed with all five CT scanners, though the magnitude of the effect was nonuniform. Significant interactions were noted between renal cyst diameter, background renal attenuation, and CT scanner type in terms of their effects on cyst attenuation. No appreciable pseudoenhancement was observed with exophytic cysts. CONCLUSION: Pseudoenhancement is maximal when small (< or = 1.5-cm) intrarenal cysts are scanned during maximal levels of renal parenchymal enhancement. The magnitude of this effect varies with scanner type but may be large enough to prevent accurate lesion characterization, despite use of a thin-section helical CT data acquisition technique

Invasive aspergillosis is an opportunistic infection that characteristically affects the immunocompromised host, resulting in a high degree of morbidity and mortality. Although the portal of entry is usually pulmonary, there are rare reports of invasive aspergillosis localized to the gastrointestinal tract. In addition, haematological spread may develop, with life threatening disseminated infection involving the vital organs and the gastrointestinal tract. Although disseminated infection is well recognized, the CT findings of gastrointestinal disease have not been reported to our knowledge. We describe the CT findings in a patient with invasive aspergillosis involving the gastrointestinal tract, which resulted in intestinal ischaemia complicated by small bowel obstruction

PURPOSE: To compare the diagnostic accuracy of focused helical computed tomography (CT) with orally administered contrast material with that of nonfocused helical CT with orally and intravenously administered contrast material. MATERIALS AND METHODS: After receiving oral contrast material, 228 patients with clinically suspected appendicitis underwent focused appendiceal CT (5-mm section thickness, 15-cm coverage in the right lower quadrant). Immediately thereafter, helical CT of the entire abdomen and pelvis was performed following intravenous administration of contrast material (abdomen, 7-mm section thickness; pelvis, 5-mm section thickness). Studies were separated and independently interpreted by three observers who were blinded to patient names. Diagnoses were established by means of surgical and/or clinical follow-up findings. RESULTS: Fifty-one (22.4%) of 228 patients had acute appendicitis. Readers diagnosed appendicitis with 83.3%, 73.8%, and 71.4% sensitivity and 93.0%, 92.3%, and 97.9% specificity with focused nonenhanced appendiceal CT. Readers diagnosed appendicitis with 92.9%, 92.9%, and 88.1% sensitivity and 93.7%, 95.1%, and 96.5% specificity with nonfocused enhanced CT. Summary areas under the receiver operating characteristic curve estimates for focused nonenhanced and nonfocused enhanced CT were 0.916 and 0.964, respectively; the differences were statistically significant (P <.05) for two of three readers. All readers demonstrated higher sensitivities for detecting the inflamed appendix with nonfocused enhanced CT. Appendicitis was missed with focused CT in two patients whose inflamed appendix was not included in the imaging of the right lower quadrant. All readers were significantly more confident in diagnosing alternative conditions with nonfocused enhanced CT. CONCLUSION: Diagnostic accuracy of helical CT for acute appendicitis improved significantly with use of intravenous contrast material

Omental infarction, an uncommon cause of acute abdominal pain, is the result of compromised perfusion to the greater omentum. Although its etiology remains uncertain, predisposing factors include obesity [Surg. Today 30 (2000) 451], strenuous activity [N. Z. Med. J. 111 (1998) 211], trauma, and idiopathic omental torsion. Often confused with acute appendicitis or cholecystitis on clinical grounds [Surg. Today 30 (2000) 451], its diagnosis has traditionally been one of exclusion, based on intraoperative and pathologic findings. This diagnosis can be made radiologically based on the characteristic findings of an inflammatory mass containing fat and fluid. We describe a case of right lower quadrant omental infarction temporally related to bowel surgery

OBJECTIVE: The purpose of our study was to determine the minimum optimal dose of IV contrast medium for helical CT that can preserve image quality while reducing cost. SUBJECTS AND METHODS: Four hundred sixty-three patients from six centers were enrolled in a prospective trial in which patients were randomized into one of four weight-based dose categories of iopromide, 300 mg I/mL: 1.25, 1.50, 1.75, and 2.0 mL/kg. Six of 463 patients were excluded from analysis. A radiologist at each center who was unaware of the volume of contrast medium administered determined whether the scans were acceptable. The responses were analyzed by dose, in aggregate, and by weight. Enhancement values (in Hounsfield units) in regions of interest in the liver, pancreas, aorta, and kidneys were obtained at a single time during the scan. The participating radiologist was unaware of these values. Finally, three additional nonparticipating site observers assessed the images for acceptability, diagnostic quality, and overall level of confidence. A cost model comparing incurred charges in using 150 or 100 mL, or 1.5 mL/kg, of low osmolality contrast medium was developed from experience in an additional 303 patients. RESULTS: We found no clinically significant difference in acceptability of scans at doses greater than 1.5 mL/kg. However, significant variability occurred among the centers. The use of 1.5 mL/kg led to a savings of $9927.16 for 303 patients when compared with the use of 150 mL at list price. The cost is the same for 1.5 mL/kg or use of 100 mL of contrast medium. CONCLUSION: A weight-based dose at 1.5 mL/kg of low osmolality contrast medium can provide acceptable scans in most patients, with a significant cost savings

This article reviews the radiologic and endoscopic diagnosis of Crohn's disease. Radiographic and endoscopic findings of Crohn's disease are discussed; a practical approach to the selection of radiologic modalities is presented; and the role of endoscopy in diagnosis and treatment is explained