M Atri

Hepatic CT enhancement: effect of the rate and volume of contrast medium injection in an animal model

AbstractBackground: To evaluate the relative effect of rate of injection and volume of contrast medium on aortic, portal, and hepatic enhancement during computed tomography (CT).n Methods: Thirty-eight nonincremental CT examinations were performed in three mini-pigs by using a combination of three different volumes (1.5, 2, and 3 mL/kg) and five different rates (1.5, 3, 4.5, 6, and 7.5 mL/s) of contrast material injection. Time-density enhancement curves of the aorta, portal vein, and liver were plotted over time for each rate of injection, each volume of contrast, and each volume–rate combination. In addition, aortic, portal, and liver peak enhancements, time-to-peak enhancements, optimal scanning intervals, and contrast enhancement indices were calculated for each volume–rate combination.n Results: Higher rates of injection increased peak aortic enhancement but had no effect on peak portal or hepatic enhancement. This result may be explained by the dilution of the bolus of contrast medium in the splanchnic circulation. When the results of a 6-mL/s injection of 1.5 mL/kg of contrast material were compared with a 3-mL/s injection of 2 mL/kg, maximum aortic enhancement increased by 32%, whereas maximum liver enhancement decreased by 35%.n Conclusion: An increase in the rate of contrast injection results in an increase of peak aortic enhancement even when the total iodine load is decreased. However, an increase of the rate of contrast injection does not increase maximum liver enhancement, which is related to the total iodine dose injected. Therefore, one cannot compensate a decrease in the iodine load by an increase in injection rate in contrast-enhanced CT of the liver.

Incidence of portal vein thrombosis complicating liver metastasis as detected by duplex ultrasound.

In a prospective study of 100 patients with liver metastasis using real‐time ultrasound, 8 patients (8%) were found to have portal vein thrombosis (PVT). Sixty seven of these patients, which included all with PVT, also underwent duplex examination. Pulsed Doppler showed absent flow in 4 of 8 patients, indicating complete obstruction. The other 4 showed different degrees of flow suggesting incomplete obstruction or collateral formation. We conclude that PVT complicating liver metastasis is not a rare finding.

Accuracy of ultrasound in counting and measuring gallstones

A prospective study of accuracy of ultrasound in measuring and counting gallstones was undertaken in 30 patients undergoing cholecystectomy. Stones were correctly counted (up to five) in 27 of 30 patients. Ninety-three of 106 stones (88%) examined were measured accurately (with a 2 mm error margin). The size of the smaller stones tended to be overestimated, whereas the size of the larger stones tended to be underestimated. When non-operative treatment of gallstones is considered, ultrasound can be used as the first examination to identify patients who will not be eligible for one or another protocol on the basis of size or number of stones.

Effect of portal venous flow augmentation on liver enhancement with CT

Abstract.Background: The purpose of this study was to evaluate the effect of portal flow augmentation on hepatic computed tomographic (CT) enhancement.nn Methods: Thirteen patients undergoing follow-up CT of the liver within 6 months of initial study ingested 470 mL of Ensure® 30 min before the second examination. Contrast medium injection and scanning parameters were identical for both studies.nn Results: The time to peak and the maximum and mean liver enhancements were 68 s, 56 HU, and 46 HU, respectively, for the examinations without Ensure® and 68 s, 53 HU, and 44 HU for the examinations with Ensure®. No significant difference was found between the two groups when mean liver enhancement was calculated over 3-s time intervals.nn Conclusion: Portal venous flow augmentation induced by a meal had no effect on liver enhancement.n