Hypervascular Hepatocellular Carcinomas: Bolus Tracking with a 40-Detector CT Scanner to Time Arterial Phase Imaging

Abstract

Peak TLC during the HAP occurred 18 seconds after triggering.

Effect of varying contrast material iodine concentration and injection technique on the conspicuity of hepatocellular carcinoma during 64-section MDCT of patients with cirrhosis

“…The second factor for the differences we found in tumour conspicuity and arterial enhancement between MCCM and HCCM during the hepatic arterial phase is the discrepancy in the duration of the contrast material injection (on average, 30 s vs 24 s, respectively, for scheme B) using a fixed injection flow rate. Although our bolus-tracking technique compares favourably with that proposed by two recent investigations on the optimal timing for the acquisition of the hepatic arterial phase using fast MDCT systems [2,3], it should be noted that our protocol did not adjust the post-triggering delay according to the contrast material injection duration. The small disparity in the average injection duration (approximately 6 s) between MCCM and HCCM could have resulted in suboptimal synchronisation of CT data acquisition with contrast medium enhancement [19,20].…”

“…To determine the scanning delay for hepatic arterial phase imaging, the contrast medium transit time in the abdominal aorta was assessed by a low-dose (120 kVp, 50 mAs) automatic bolus-tracking technique with automated scan-triggering software (Care Bolus CT; Siemens Medical Systems). Arterial phase scanning was started automatically 18 s after the trigger threshold (150 HU above the baseline (290-310 HU in absolute value)) was reached at the level of the supracoeliac abdominal aorta (range 25-40 s) [2]. The hepatic venous and delayed phases were started automatically 70 and 180 s, respectively, after the start of contrast medium injection.…”

“…Although this technique has shown several advantages over conventional CT, including better discrimination between different circulatory phases, the potential for scanning during peak organ enhancement throughout the entire imaging volume and true isotropic CT data sets, it has raised considerable challenges for the design of scanning and contrast material injection protocols that are optimised for the detection of hypervascular HCC lesions [1]. Recent investigations have emphasised the importance of using test bolus or bolus-tracking methods to synchronise CT data acquisition with the peak tumourto-liver contrast for hypervascular HCC lesions [2,3]; however, the most effective contrast medium injection technique for maximising tumour enhancement during the narrow temporal acquisition of modern MDCT systems remains largely unexplored. Previous studies with early generation MDCT scanners reported conflicting results with varying volumes and concentrations of iodine, injection flow rates and durations of injection of contrast material on the conspicuity of hypervascular HCC tumours [4][5][6][7][8].…”

Focal Liver Lesions

“…The timing of the image acquisition in relation to contrast media administration depends on whether imaging is required during early arterial phase (for arterial anatomy only), late arterial phase (for hypervascular tumor detection and characterization), or venous phase (for follow-up imaging and hypovascular tumor detection). For the detection and characterization of focal liver lesions, late arterial phase imaging (with a delay of aortic transit time plus 15-18 s) [6,7] and a venous phase scan (20-30 s interscan delay or with fixed delay of ~60-70 s) are performed. However, the use of combinations of these imaging phases also depends on specific indications [8].…”

The added diagnostic value of 64-row multidetector CT combined with contrast-enhanced US in the evaluation of hepatocellular nodule vascularity: implications in the diagnosis of malignancy in patients with liver cirrhosis

“…The CT number was monitored by one region-of-interest (ROI) cursor (0.8-2.0 cm²) placed in the abdominal aorta at the L1 vertebral body level with a trigger threshold set at 140 HU. The arterial phase started with a delay of 18 s after the threshold had been reached [20]. Real-time, low-dose (120 kVp, 15 mAs) serial monitoring studies began 8 s after the start of the contrast material injection.…”