Opacification of the urinary tract in portal venous spiral CT without delayed scans.

In portal venous spiral CT there is no visible renal contrast excretion within the usual period of scanning. To opacify collecting systems additional delayed scanning is required. We administered an extra pre-dose of contrast medium before the main portal venous bolus in order to opacify the urinary tract and studied its effects on liver attenuation. In 32 patients examined first by non-contrast spiral CT 20 ml of a non-ionic IV CM were injected. Five minutes later, orientating cuts in the liver and along the urinary tract were obtained. Immediately thereafter, a 120-ml bolus was administered at 3 ml/s for portal venous phase helical CT (60-s delay craniocaudad). The quality of renal excretion was graded visually (excellent, fair, poor, none). Hepatic attenuation measurements were performed at comparable regions of interest. In all patients 20 ml CM opacified the renal pelvis after 5 min. Depiction of the ureters was excellent in 14, fair in 11 and poor or none in 7 cases. There was little effect on mean hepatic attenuation by the 20-ml pre-bolus after 5 min: mean enhancement 2.3 HU (range -0.6 to 7.8 HU). Mean hepatic enhancement after the 120-ml portal venous bolus ranged between 23.6 and 74.1 HU (mean 51.5 HU). When opacification of the urinary tract is necessary, pre-administration of a 20-ml bolus 5 min before portal venous scanning may save an extra delayed spiral. The effects on hepatic enhancement are negligible.

Helical CT cholangiography for the detection and localization of bile duct leakage.

OBJECTIVE: We describe the use of helical CT cholangiography or helical CT after administration of biliary i.v. contrast material to verify and localize bile duct leakage. CONCLUSION: Helical CT cholangiography revealed bile leaks in seven patients after penetrating trauma or liver or gallbladder surgery and excluded bile leaks in two patients with blunt liver trauma. Endoscopic retrograde cholangiography was performed in only one of seven patients with bile leakage and was avoided in an additional two patients in whom CT cholangiography excluded leakage. The method is a feasible, noninvasive tool for the detection and localization of bile leaks and may help avoid endoscopic retrograde cholangiography.

Optimizing liver contrast in helical liver CT: value of a real-time bolus-triggering technique.

Optimal liver enhancement during portal venous-phase helical CT is crucial in the detection of parenchymal liver lesions. In the prospective study reported here we investigated the effects of a real-time bolus-tracking system on mean and maximal liver enhancement. In 79 patients referred to us for abdominal CT we injected 120 ml of non-ionic contrast (300 mg I/ml) at a rate of 3 ml/s. After a nonintravenous contrast upper abdominal scan a portal venous phase was performed. In 39 patients (mean weight 72.6 +/- 18.7 kg, range 48-139 kg) real-time bolus tracking was performed using the CARE Bolus software (Siemens, Erlangen, Germany). The software performs repetitive low-dose test scans in a preselected region of interest and measures the Hounsfield attenuation and liver enhancement in real-time. After a critical threshold (we selected 31 HU) is surpassed, the software starts diagnostic spiral scanning. Our control consisted of 40 patients weighing 51-100 kg (mean 73.2 +/- 11.1 kg) who were scanned with a fixed, preselected start delay of 80 s. Mean hepatic enhancement was 54.0 +/- 9.9 HU (range 33.3-74 HU) in 37 automatically triggered patients, mean peak hepatic enhancement 64.6 +/- 12.6 HU (range 42.0-91.8 HU). In 2 patients of the study group scanning had to be started manually. In the control group with fixed delay mean enhancement was 48.3 +/- 9.2 HU (range 33.8-71.6 HU) and peak enhancement 55.5 +/- 9.7 HU (range 39.7-81.0 HU). Differences were significant (p < 0.05, Student's t-test). Real-time bolus tracking significantly increased mean hepatic enhancement and may improve portal venous hepatic CT scanning.