Dual-phase helical CT of the liver: effects of bolus tracking and different volumes of contrast material.
ABSTRACT To evaluate the effects of tracking and volume of contrast material on dual-phase helical computed tomography (CT) of the liver.
CT was performed in 120 consecutive patients. Either 100 mL (groups 1 and 2) or 120 mL (groups 3 and 4) of contrast material was injected at a rate of 4 mL/sec. In groups 1 and 3, the scanning delay was fixed, whereas in groups 2 and 4, scanning delays were determined individually by means of a semiautomatic bolus tracking device. The arterial phase began when splenic enhancement was greater than 10 HU and ended when hepatic enhancement was greater than 20 HU, which characterized the start of the portal venous phase.
The mean duration of the arterial phase was 11.6 (100 mL) and 12.2 seconds (120 mL). The arterial phase of the liver within the defined limits was sufficiently timed in only 16 (54%) patients in group 1, 25 (83%) in group 2, and 20 (67%) in groups 3, whereas it was significantly (P < .05) better in 28 (93%) patients in group 4. A significantly (P < .05) higher mean parenchymal enhancement in the portal venous phase (63.6 HU +/- 8.5) was obtained in group 4.
Bolus tracking of a volume of 120 mL provided the most accurate results in dual-phase liver CT.
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ABSTRACT: Bolus tracking can individualize time delay for the start of scans in spiral computed tomography (CT). We compared automatic bolus tracking method with fixed time-delay technique in biphasic contrast enhancement during multidetector CT of abdomen. Adult patients referred for spiral CT of the abdomen were randomized into two groups; in group 1, the arterial and portal phases of spiral scans were started 25 s and 55 s after the start of contrast material administration; in group 2, using the automatic bolus tracking software, repetitive monitoring scans were performed within the lumen of the descending aorta as the region of interest with the threshold of starting the diagnostic scans as 60 HU. The contrast enhancement of the aorta, liver, and spleen were compared between the groups. Forty-eight patients (23 males, 25 females, mean age=56.4±13.5 years) were included. The contrast enhancement of the aorta, liver, and spleen at the arterial phase was similar between the two groups (P>0.05). Regarding the portal phase, the aorta and spleen were more enhanced in the bolus-tracking group (P<0.001). The bolus tracking provided more homogeneous contrast enhancement among different patients than the fixed time-delay technique in the liver at portal phase, but not at the arterial phase. The automatic bolus-tracking method, results in higher contrast enhancement of the aorta and spleen at the portal phase, but has no effect on liver enhancement. However, bolus tracking is associated with reduced variability for liver enhancement among different patients.Iranian Journal of Radiology 01/2014; 11(1):e4617. · 0.18 Impact Factor
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ABSTRACT: OBJECTIVE. The purpose of this study was to compare scan quality and lesion conspicuity for late arterial and portal venous phase liver CT scans using fixed versus patient-tailored scan delay derived with an evidence-based timing bolus method. MATERIALS AND METHODS. We retrospectively identified the cases of 73 patients who underwent both multiphase liver CT with fixed late arterial and portal venous phase scan delay times of 45 and 80 seconds and subsequent multiphase liver CT with patient-tailored scan delay determined with a timing bolus and a previously reported relation between the time to peak aortic and liver enhancement. Both late arterial and portal venous phase scans were graded in terms of scan quality. Hepatic lesion conspicuity (difference in attenuation between lesion and liver parenchyma) for hypervascular lesions (late arterial phase) and hypovascular lesions (portal venous phase) was recorded. RESULTS. Patient-tailored scan delay reflected a wide range of times to peak aortic enhancement (mean, 24 seconds; range, 18-32 seconds) and yielded a greater proportion of optimal scans compared with fixed scan delay for both late arterial phase (92% versus 74%, p < 0.01) and portal venous phase (86% versus 70%, p < 0.05) scans. Mean hypervascular lesion conspicuity was greater for lesions imaged with patient-tailored scan delay rather than fixed scan delay (84.0 versus 57.0 HU, p < 0.01). CONCLUSION. Compared with examinations with fixed scan delay, multiphase liver CT that incorporates patient-tailored scan delay produces more optimally timed late arterial and portal venous phase CT scans with greater lesion conspicuity.American Journal of Roentgenology 02/2014; 202(2):318-23. · 2.74 Impact Factor