[Usefulness of Delay Time Setting in Computed Tomography Pulmonary Angiography].

PURPOSE: During computed tomography pulmonary angiography (CTPA), a decrease in the CT value of the pulmonary artery may be observed due to poor contrast enhancement, even though the imaging is performed at the optimum timing while continuously injecting a contrast medium. This study focused on the increase in blood flow in the superior and inferior vena cava during inspiration that affects the decrease in the CT value of the pulmonary artery and investigated a radiography method in which a delay time was set after inspiration in clinical cases. METHODS: A total of 50 patients who underwent CTPA for suspected pulmonary thromboembolism were included. Using the bolus tracking method, we monitored the pulmonary arteries before and after inspiration, and investigated the CT value changes. RESULTS: A decrease in the CT value of the pulmonary artery after inspiration was observed in approximately 30% of cases. By setting the delay time, the contrast enhancement effect before and after inspiration became equivalent. CONCLUSION: As a result of this study, avoiding a decrease in the CT value of the pulmonary artery is possible by setting a delay time after inspiration, which is considered useful during CTPA.

[Contrast-enhancement Effects of Dual-peak Contrast Medium Injection Method Using Bolus-tracking Technique in Coronary and Aorta CT Angiography].

OBJECTIVE: We compared the contrast-enhancement effects of the coronary arterial phase and the aortic phase in coronary and aorta computed tomography angiography (CA-CTA) using the bolus-tracking technique-based single-peak contrast medium injection (BT-SPI) method and the bolus-tracking technique-based dual-peak contrast medium injection (BT-DPI) method. METHOD: CA-CTA images were acquired from 30 patients, using BT-SPI and BT-DPI. Regions of interest were selected in the right ventricle and ascending aorta during the coronary arterial phase, and in the aorta during the aortic phase to obtain mean CT values. The mean CT values were used to compare the contrast-enhancement effects of BT-SPI and BT-DPI. RESULTS: The mean CT value of the right ventricle during the coronary arterial phase obtained using BT-SPI (320 Hounsfield unit [HU]) and BT-DPI (83 HU) was significantly different (p<0.05). Using BT-SPI and BT-DPI, the mean CT values of the ascending aorta during the coronary arterial phase were 361 HU and 379 HU, respectively, and those of the aorta during the aortic phase were 436 HU and 437 HU, respectively. The difference in the mean CT values for the aorta between BT-SPI and BT-DPI during the coronary arterial and aortic phases was insignificant. CONCLUSION: The retention of the contrast medium in the right ventricle during the coronary arterial phase using BT-DPI was lower than that using BT-SPI. BT-DPI showed substantial contrast-enhancement effects in both the coronary arterial and aortic phases.

Triple-phase MDCT of liver: Scan protocol modification to obtain optimal vascular and lesional contrast.

CONTEXT: With advances in 16-slice multidetector computed tomography (MDCT), the entire liver can be scanned in 4-6 s and a single breath-hold dual-phase scan can be performed in 12-16 s. Consequently, optimizing the scan window has become critical. AIM: The purpose of our study was to optimize scan delays using bolus-tracking techniques for triple-phase CT of the liver. SETTINGS AND DESIGN: Fifty patients with liver lesions were randomly divided into two groups with 25 patients each. The patients were subjected to triple-phase MDCT of liver with two different scan protocols. MATERIALS AND METHODS: They were administered 1.5 mL/kg of 300 mg/mL of iohexol at a rate of 3.0 mL/s with a pressure injector. Using bolus-tracking program, scans were commenced at 4, 19, and 44 s and 8, 23, and 48 s for the first, second, and third phases, respectively. The mean CT values [Hounsfield unit (HU)] were measured in the aorta, hepatic artery, portal vein, hepatic vein, liver parenchyma, and lesion using circular region of interest cursor ranging in size from 5 to 20 mm in diameter on all phases. STATISTICAL ANALYSIS USED: Statistical analysis was carried out using paired Student's t-test. RESULTS: In hepatic arterial phase, hepatic artery has shown better enhancement in Group B (8 s) (P = 0.0498) compared with Group A (4 s). In portal venous phase, there were no significant differences in contrast enhancement index (CEI) values at any of the six measured regions between the groups. In the hepatic venous phase, liver parenchyma has shown nearly significant (P = 0.0664) higher CEI values in Group B (48 s) when compared with Group A (44 s). CONCLUSION: A scan delay of 8 s, after trigger threshold (100 HU) is reached in the lower thoracic aorta, is optimal for the early arterial phase imaging, this phase being most helpful for assessment of hepatic arterial tree (CT angiography). The liver parenchyma showed maximum enhancement at 48 s scan delay.

Optimal scan delay depending on contrast material injection duration in abdominal multi-phase computed tomography of pancreas and liver in normal Beagle dogs.

This study was conducted to establish the values for optimal fixed scan delays and diagnostic scan delays associated with the bolus-tracking technique using various contrast material injection durations in canine abdominal multi-phase computed tomography (CT). This study consisted of two experiments employing the crossover method. In experiment 1, three dynamic scans at the porta hepatis were performed using 5, 10 and 15 sec injection durations. In experiment 2, two CT scans consisting of five multi-phase series with different scan delays of 5 sec intervals for bolus-tracking were performed using 5, 10 and 15 sec injection duration. Mean arrival times to aortic enhancement peak (12.0, 15.6, and 18.6 sec for 5, 10, and 15 sec, respectively) and pancreatic parenchymal peak (17.8, 25.1, and 29.5 sec) differed among injection durations. The maximum mean attenuation values of aortas and pancreases were shown at the scan section with 0 and 5, 0 and 10 and 5 and 10 sec diagnostic scan delays during each injection duration, respectively. The optimal scan delays of the arterial and pancreatic parenchymal phase in multi-phase CT scan using fixed scan delay or bolus-tracking should be determined with consideration of the injection duration.

Optimal scan delay depending on contrast material injection duration in abdominal multi-phase computed tomography of pancreas and liver in normal Beagle dogs

This study was conducted to establish the values for optimal fixed scan delays and diagnostic scan delays associated with the bolus-tracking technique using various contrast material injection durations in canine abdominal multi-phase computed tomography (CT). This study consisted of two experiments employing the crossover method. In experiment 1, three dynamic scans at the porta hepatis were performed using 5, 10 and 15 sec injection durations. In experiment 2, two CT scans consisting of five multi-phase series with different scan delays of 5 sec intervals for bolus-tracking were performed using 5, 10 and 15 sec injection duration. Mean arrival times to aortic enhancement peak (12.0, 15.6, and 18.6 sec for 5, 10, and 15 sec, respectively) and pancreatic parenchymal peak (17.8, 25.1, and 29.5 sec) differed among injection durations. The maximum mean attenuation values of aortas and pancreases were shown at the scan section with 0 and 5, 0 and 10 and 5 and 10 sec diagnostic scan delays during each injection duration, respectively. The optimal scan delays of the arterial and pancreatic parenchymal phase in multi-phase CT scan using fixed scan delay or bolus-tracking should be determined with consideration of the injection duration.

Optimising the scan delay for arterial phase imaging of the liver using the bolus tracking technique

Objective: To optimize the delay time before the initiation of arterial phase scan in the detection of focal liver lesions in contrast enhanced 5 phase liver CT using the bolus tracking technique. Patients and Methods: Delay - the interval between threshold enhancement of 100 hounsfield unit (HU) in the abdominal aorta and commencement of the first arterial phase scan. Using a 16 slice CT scanner, a plain CT of the liver was done followed by an intravenous bolus of 120 ml nonionic iodinated contrast media (370 mg I/ml) at the rate of 4 mL/s. The second phase scan started immediately after the first phase scan. The portal venous and delay phases were obtained at a fixed delay of 60 s and 90 s from the beginning of contrast injection. Contrast enhancement index (CEI) and subjective visual conspicuity scores for each lesion were compared among the three groups. Results: 84 lesions (11 hepatocellular carcinomas, 17 hemangiomas, 39 other hypervascular lesions and 45 cysts) were evaluated. CEI for hepatocellular carcinomas appears to be higher during the first arterial phase in the 6 seconds delay group. No significant difference in CEI and mean conspicuity scores among the three groups for hemangioma, other hypervascular lesions and cysts. Conclusion: The conspicuity of hepatocellular carcinomas appeared better during the early arterial phase using a bolus tracking technique with a scan delay of 6 seconds from the 100 HU threshold in the abdominal aorta.

Optimising the scan delay for arterial phase imaging of the liver using the bolus tracking technique.

OBJECTIVE: To optimize the delay time before the initiation of arterial phase scan in the detection of focal liver lesions in contrast enhanced 5 phase liver CT using the bolus tracking technique. PATIENTS AND METHODS: Delay - the interval between threshold enhancement of 100 hounsfield unit (HU) in the abdominal aorta and commencement of the first arterial phase scan. Using a 16 slice CT scanner, a plain CT of the liver was done followed by an intravenous bolus of 120 ml nonionic iodinated contrast media (370 mg I/ml) at the rate of 4 mL/s. The second phase scan started immediately after the first phase scan. The portal venous and delay phases were obtained at a fixed delay of 60 s and 90 s from the beginning of contrast injection. Contrast enhancement index (CEI) and subjective visual conspicuity scores for each lesion were compared among the three groups. RESULTS: 84 lesions (11 hepatocellular carcinomas, 17 hemangiomas, 39 other hypervascular lesions and 45 cysts) were evaluated. CEI for hepatocellular carcinomas appears to be higher during the first arterial phase in the 6 seconds delay group. No significant difference in CEI and mean conspicuity scores among the three groups for hemangioma, other hypervascular lesions and cysts. CONCLUSION: The conspicuity of hepatocellular carcinomas appeared better during the early arterial phase using a bolus tracking technique with a scan delay of 6 seconds from the 100 HU threshold in the abdominal aorta.