Scan Delay Time Research Articles

A Study on the Optimization of Contrast Enhancement in Cerebrovascular CT in Hemorrhagic Stroke Patients

During the brain computed tomography angiography (Brain CTA) test of hemorrhagic stroke patients, we tried to find out the test method for optimizing contrast enhancement of cerebrovascular vessels by changing the location of the region of interest (ROI) and scan delay time. From September 2022 to February 2023, 80 patients who visited the emergency room and performed a Brain CTA test were tested, and 10 people in control group without disease were ROI set at C3 to C4 level and performed a test by 6-second delay scan as soon as contrast enhancement was performed on common carotid artery (CCA) with the naked eye. 40 people in the hemorrhagic stroke experiment group A setting the same test method as the control group were tested after A-0; 6 second, A-1; 8 second, A-2; 10 second, A-3; 12-second delay for 10 people each, and 30 people in experiment group B setting ROI at circle of willis level and as soon as contrast enhancement was performed in the middle cerebral artery (MCA) were tested after B-1; 2 second, B-2; 4 second, B-3; 6-second delay for 10 people each. The evaluation methods include quantitative evaluation that compares and analyzes the mean HU values and percentage values of internal carotid artery (ICA), MCA, superior sagittal sinus (SSS), and internal jugular vein (IJV) of the control group and experimental groups A and B, qualitative evaluation through reconstructed images, and significance evaluation was conducted using an independent sample t-test. As a result of the quantitative evaluation, the mean HU value of MCA in the experimental group was measured lower than that of the control group, 369 HU, but was generally close to 300 HU. In the MCA vs SSS percentage value, the experimental group B-2 was 0.7%, the closest value to the control group. As a result of the blind test through reconstructed images as a qualitative evaluation, the control group scored the highest with 16 points, and in the experimental group B-2 scored the highest with 15 points. As a result of significance evaluation through an independent sample t-test, the p-value of the control group and the experimental group B-2 was 0.408, which was evaluated as having no significant difference, and other experimental groups were evaluated that there was a significant difference. As a result of analyzing the test performed by changing the ROI position and scan delay time of control and experimental groups A and B, setting the ROI at the circle of willis level and testing after 4-second delay as soon as contrast enhancement is made in MCA will be useful for Brain CTA test in hemorrhagic stroke patients.

Optimizing the Imaging Scheme of Small-Dose Contrast Agent in 4D-CT Localization Enhancement Scan for Radiotherapy of Liver Cancer

The primary liver cancer radiation therapy 4D-CT-enhanced (CE-4DCT) scan can accurately reflect the state of the liver as it moves with respiration, and enables clear visualization of the tumor, providing a precise range for target area outlining. However, the CE-4DCT scan localization time of primary liver cancer is long, and the fixed delay time of diagnostic CT cannot obtain high-quality 4DCT images. To this end, we designed a randomized controlled study to investigate the ideal localization scan delay time parameters for primary liver cancer CE-4DCT. Patients with primary hepatocellular carcinoma who presented to our department for radiotherapy CT localization from January to December 2022 participated in this study. All subjects were randomly divided into two groups in a 1:1 ratio. CE-4DCT scans were performed using a high concentration of iodomepril (400 mg/ml) contrast agent with a contrast volume equal to the patient's body weight. The scanning parameters were set according to scheme A (flow rate 2.0 ml/s, delay time 30s) and B (2.0 ml/s, 35s) respectively. Before the CE-4D CT scan, CT plain scan was routinely performed, physicians measured the CT value (HU) of abdominal aorta, portal vein, left hepatic vein, middle hepatic vein, right hepatic vein, liver parenchyma and tumor lesion on CT40 time item and plain scan images respectively. The image quality was subjectively and qualitatively assessed. The image enhancement effect is divided into excellent, good, relatively poor and poor. A total of 18 patients were included in this study. Patient characteristics were well-balanced in both groups. There were statistical differences between the two groups (A vs B) in the abdominal aorta (226.66 ± 45.59 vs. 176.66 ± 32.84, p = 0.017), left hepatic vein (142.77 ± 24.41 vs. 164.88 ± 19.02, p = 0.048); in the portal vein, middle hepatic vein, right hepatic vein, liver parenchyma, and tumor lesions CT values were not statistically different. The comparison of all flat-scan images between the two groups was statistically significant. The comparison of all flat-scan images in both groups was statistically significant. The subjective qualitative assessment of the developing effect was excellent in 44.4% (33.3% vs. 11.1%), good in 16.7% (5.6% vs. 11.1%), and poor in 38.9% (16.7% vs. 22.2%) in both groups. image quality was slightly higher in group A than in group B, but did not reach statistical significance (χ2 = 1.088, p = 0.698). In patients with primary hepatocellular carcinoma with portal vein carcinoma thrombosis 83.33% subjectively evaluated poor results. Qualitatively acceptable enhanced images were obtained for primary hepatocellular carcinoma (CE-4DCT) localization scans with a delay time controlled at 30s when using the least amount of contrast agent and the same flow rate.

Optimization of Scan Delay in Contrast Enhanced Computed Tomography of Pancreas Using Bolus Tracking Category

Introduction: Pancreatic pathologies present a challenge for the medical imaging professionals for detection, classification and staging. Multiphasic multidetector computed tomography provides detailed visualization and definition of deeper and smaller structures and enhancement pattern of tumors during different phases. The objective of this study was to optimize the scan delay time for contrast enhanced computed tomography of pancreas after the use of bolus tracking technique. Materials and methods: Triphasic MDCT of the pancreas was performed on 109 patients after administration of 300-350 mgI/mL contrast medium injected at 3.5 mL/s. Patients were prospectively randomized into three groups with different scanning delays for the three phases (arterial, pancreatic, and venous) after bolus tracking was triggered at 100 HU of aortic contrast enhancement. Mean attenuation values of the abdominal aorta, superior mesenteric artery, pancreatic parenchyma, splenic vein, portal vein, and hepatic parenchyma were measured. Increases in attenuation values after contrast administration were assessed. Results: Mean contrast enhancement in the aorta (change in attenuation, 313–320 HU) and the superior mesenteric artery (change in attenuation, 291–302 HU) approached peak enhancement 4-7 seconds after bolus tracking was triggered. Pancreatic parenchyma became most intensely enhanced (change in attenuation, 107–110 HU) 20-25 seconds after triggering, and then the enhancement gradually decreased. Enhancement of the splenic vein and portal vein peaked at 22 seconds. Liver parenchyma reached 71 HU, 25 seconds after triggering and reached a plateau (change in attenuation, 81-76 HU) at a further scanning delay of 45–50 seconds. Conclusion: Based on the protocol used in this study, the optimum scan delay were 4-7 seconds for arterial phase, 10-22 seconds for pancreatic parenchymal phase and 40-50 seconds for the hepatic parenchymal phase; after bolus tracking triggered at 100 HU in the abdominal aorta.

Proposal of a novel protocol using estimated cardiac index fractional dose to improve aortic contrast enhancement for early-phase dynamic CT.

Maximum aortic computed tomography value (CTV) is difficult to control because of variations in cardiac function and patient physique. Therefore, to improve early-phase aortic enhancement on dynamic computed tomography (CT), we developed an estimated cardiac index fractional dose (eciFD). The eciFD protocol is a novel and original protocol for administering fractional dose (FD), representing the amount of iodine per unit body weight per injection duration, based on cardiac index (cardiac output divided by body surface area) as estimated by age in early-phase dynamic CT. At the time of administration, by selecting FD based on the patient's age and selecting a parameter that can achieve this FD, an aortic CTV ≥300 HU (ACTV≥300) can be obtained. This study aimed to investigate aortic enhancement on CT angiography using the eciFD protocol.This retrospective study investigated 291 consecutive patients who underwent dynamic CT from neck to abdomen after recommendation of the eciFD protocol at our institution. We compared early-phase aortic CTV distributions by scan delay between an eciFD group (eciFD applied, n = 135) and a non-eciFD group (eciFD not applied, n = 80). The effect of eciFD on early-phase ACTV≥300 was evaluated using logistic regression analysis adjusted for several potentially meaningful clinical confounders related to aortic CTV, namely male sex, heart rate ≤80 beats/min, estimated glomerular filtration rate ≤40 mL/min, use of eciFD, bolus tracking (BT), history of myocardial infarction, and order from the emergency center.The eciFD protocol was a significant factor for early-phase ACTV≥300 after adjusting for several confounders (odds ratio 3.03; 95% confidence intervals 1.59–5.77; P = .001). No interaction was seen between BT and eciFD protocol (p for interaction = 0.76). In terms of CTV distribution, with both a fixed scan delay time and BT, the eciFD group showed a high aortic CTV. The combination of eciFD protocol with BT provided a particularly high percentage of patients with ACTV≥300 (86.4%).The eciFD protocol was useful for improving aortic contrast enhancement. These findings need to be validated in a randomized controlled study.

Analisis Letak Tracking Di Area Arteri Carotis Interna Dan Arcus Aorta Pada Pemeriksaan Cta Cerebral Di Instalasi Radiologi RSUD Salatiga

Background: In the CTA examination of cerebral angiography at the Radiology Installation of Salatiga Hospital, the flow rate used was 5 ml/s, bolus tracking contrast media was placed in 2 different places, some radiographers used the internal carotid artery and some used the aortic arch as an indicator of ROI tracking. Image acquisition is done by adjusting the scan delay post injection of contrast media and pre bolus tracking, so that the difference in the placement of the tracking affects the scan delay time and the dose given to the patient. The purpose of this study is to determine the location of accurate tracking in terms of image information and radiation dose given to the patient.Methods: This type of research is descriptive with qualitative data. The research object is the patient who performs Cerebral CTA examination with tracking location on the interna carotid artery(ICA) and aortic arch. The research subjects were 2 radiographers and 1 radiologist. Data collection was done by interview observation method.Results: Research shows that in Cerebral CTA examination using ROI tracking in the ICA area, there is a risk of contrast media entering the blood vessels if the scan delay time setting is not right, while the ROI tracking setting in the aortic arch is safer if the patient moves the tracking location is still around blood vessels but the radiation given to the patient tends to be larger as the scanning area increasesConclusions: The use of tracking ROI in the area of the internal carotid artery and aortic arch on CTA Cerebral examination can be used according to the radiographer's expertise in finding these blood vessels, the use of the right scan delay time affects the scanning results produced.

Reducing amount of contrast agent after compression of right brachial artery using a blood pressure cuff in computed tomography cerebrovascular angiography.

To invastgate feasibility of low-dose contrast agent in cerebral computed tomography angiography (CTA) to alleviate side effects. Siemens' Somatom Definition AS+CT scanner, Heine's blood pressure monitor G7-M237 (BP cuff) and Ultravist contrast agent (370 mg Iodine/ml) are used. CTA is acquired using following scan parameters including slice thickness of 1mm, image acquisition parameters of 128×0.6 mm, pitch size of 0.8 mm, 175 effective mAs, 120 kVp tube voltage, scan delay time of 3 seconds, and the scan time of 4 seconds. This study is conducted by securing the IV route in the left antecubital vein before injection of contrast agent, wrapping BP cuff around the branchial artery of the opposite right arm after setting the pressure to 200 mmHg. Then, the injection rate of the contrast agent is fixed at 4.5 cc/sec and contrast agent was injected in three different amounts (70, 80, and 100 cc). Bp cuff is released from this moment when HU value reachs 100. In this study, the mean HU values measured from common carotid artery are 412.45±5.89 when injecting 80cc contrast agent and using BP cuff and 399.64±5.51 when injecting 100 cc contrast agenet and not using BP cuff, respectively. In middle cerebral artery M1, the mean HU values are 325.23±38.29 when injecting 80cc contrast agent and using BP cuff and 325.00±30.63 when injecting 100cc contrast agent blood and not using pressure cuff, respectively. Difference of mean HU values is not statistically significant (p > 0.05) with and without using BP cuff. This study demonstrates that reducing amount of contrast agent is possible when the right brachial artery is compressed using BP cuff. Study results indicate that reducing 20% injection of contrast agent in CT cerebrovascular angiography can still yield comparable imaging results with conventional contrast angent usage, which implies that less side effects are expected with a contrast agent injection. Thus, this study can serve as a reference for potential reducing side effect during CT cerebrovascular angiography.

Relative Enhancement Ratio of Portal Venous Phase to Unenhanced CT in the Diagnosis of Lipid-poor Adrenal Adenomas.

Background The development of an accurate, practical, noninvasive, and widely available diagnostic approach to characterize lipid-poor adrenal lesions (greater than 10 HU at unenhanced CT) remains an ongoing demand. Purpose To investigate whether combined assessment of unenhanced and portal venous phase CT allows for the differentiation of lipid-poor adrenal adenomas from nonadenomas. Materials and Methods Patients with lipid-poor adrenal lesions who underwent unenhanced and portal venous phase CT with a single-energy scanner between January 2016 and March 2020 were identified retrospectively. For each lesion, the unenhanced and contrast-enhanced attenuation were measured; the absolute enhancement (contrast-enhanced minus unenhanced attenuation [HU]) and relative enhancement ratio ([absolute enhancement divided by unenhanced attenuation] × 100%) were calculated. The sensitivity achieved at 95% specificity to distinguish adenomas from nonadenomas was determined with receiver operating characteristic curve analysis and compared among parameters with use of the McNemar test. Results A total of 220 patients (mean age ± standard deviation, 66 years ± 12; 134 men) with 131 lipid-poor adenomas and 89 nonadenomas were analyzed. The sensitivity (achieved at 95% specificity) of the relative enhancement ratio (86% [113 of 131 adenomas; 95% CI: 79, 92] at a threshold of >210%) was higher than that of unenhanced attenuation (50% [66 of 131 adenomas; 95% CI: 42, 59] at a threshold of ≤21 HU), contrast-enhanced attenuation (3% [four of 131 adenomas; 95% CI: 1, 8] at a threshold of >120 HU), and absolute enhancement (24% [32 of 131 adenomas; 95% CI: 17, 33] at a threshold of >74 HU; all P < .001). The sensitivities of the relative enhancement ratio were 100% (58 of 58 adenomas; 95% CI: 94, 100), 83% (52 of 63 adenomas; 95% CI: 71, 91), and 30% (three of 10 adenomas; 95% CI: 7, 65) for adenomas measuring unenhanced attenuation of more than 10 HU up to 20 HU, 21-30 HU, and more than 30 HU, respectively. Conclusion A relative enhancement ratio threshold of greater than 210%, measured at unenhanced and portal venous phase CT, accurately differentiated lipid-poor adenomas from nonadenomas, particularly for lesions with unenhanced attenuation of 10-30 HU. © RSNA, 2021 Online supplemental material is available for this article.

An optimized test bolus for computed tomography pulmonary angiography and its application at 80\u2009kV with 10\u2009ml contrast agent

Computed tomography pulmonary angiography (CTPA) is usually used for pulmonary embolism (PE) detection. However, the determination of scan timing remains a challenge due to the short scan duration of CTPA. We aimed to develop an optimized test bolus to determine scan delay in CTPA. The time-enhancement curves were obtained by measuring the enhancement within a region of interest in the main pulmonary artery and vein. A total of 70 patients were randomly divided into two groups (n = 35 each): the control group underwent CTPA using the test bolus approach and the test group underwent CTPA using the biphasic time-enhancement curves approach. Tube voltages of 100 kVp and 80 kVp and 20 ml and 10 ml contrast agent were adopted in the control and test groups, respectively. The CT numbers, image quality, PE detection was evaluated. There was a point of intersection between the pulmonary artery and vein test bolus enhancement curves. The scan delay time (TDELAY) was obtained based on the time at intersection (TCROSS) and the scan duration (TSD): TDELAY = TCROSS − TSD. The mean CT numbers for pulmonary vein in the control were higher than those in the test group (all p < 0.001). The image quality for the pulmonary arteries in the test group was better than that in the control group (p < 0.01), with artifact reduction in the superior vena cava. Segmental PE could be detected using the optimized protocol. The radiation dose and iodine load in the test group were all lower than those in the control (p < 0.01). We established an approach to calculate the scan delay of CTPA, and this approach could be used for CTPA at 80 kVp with 10 ml contrast agent.

Optimization of scan delay for multi-phase computed tomography by using bolus tracking in normal canine kidney

This study was performed to optimize scan delays for canine kidney by using a bolus-tracking technique. In six beagle dogs, computed tomography (CT) of the kidney was performed three times in each dog with different scan delays after a bolus-tracking trigger of 100 Hounsfield units (HU) of aortic enhancement. Delays were 5, 20, 35, and 50 sec for the first scan, 10, 25, 40, and 55 sec for the second scan, and 15, 30, 45, and 60 sec for the third scan. The renal artery-to-vein contrast difference peaked at 5 sec, and the renal cortex-to-medulla contrast difference peaked at 10 sec. The renal cortex-to-medulla contrast difference approached zero at a scan delay of 30 sec after the bolus trigger. For the injection protocol used in this study, the optimal scan delay times for renal arterial, corticomedullary, and nephrographic phases were 5, 10, and 30 sec after triggering at 100 HU of aortic enhancement using the bolus-tracking technique. The bolus-tracking technique is useful in multi-phase renal CT study as it compensates for different transit times to the kidney among different animals, requires a small dose of contrast media, and does not require additional patient radiation exposure.

Temporal Changes of Texture Features Extracted From Pulmonary Nodules on Dynamic Contrast-Enhanced Chest Computed Tomography: How Influential Is the Scan Delay?

The aim of this study was to describe the temporal changes of various texture features extracted from pulmonary nodules on dynamic contrast-enhanced computed tomography (DCE-CT) and to compare the feature values among multiple scanning time points. We also aimed to analyze the variability of texture features across multiple scan delay times. This retrospective study was approved by the institutional review board of Seoul National University Hospital with waiver of patients' informed consent. Twenty patients (M:F, 6:14; mean age, 60.25 ± 11.97 years) with 20 lung nodules (mean size, 24.1 ± 12.3 mm) underwent DCE-CT with multiple scan delays (30, 60, 90, 120, 150, 180, 210, 240, 300, and 480 seconds) after precontrast scans. Lung nodule segmentation and texture feature extraction were performed at each time point using in-house software. Texture feature values were compared among the multiple time points using the Friedman test with post hoc pairwise Wilcoxon signed rank test. In addition, the dynamic range (DR) reflecting the variability between 2 time points to the interpatient range was calculated. Thereafter, we determined the stable time range that met both "DR greater than 0.90" and "no statistically significant difference" between all time point pairs for each feature. The degree of variability across all scan delay times was obtained using coefficients of variation. Standard deviation, variance, entropy, sphericity, discrete compactness, gray-level cooccurrence matrix (GLCM) inverse difference moment (IDM), GLCM contrast, and GLCM entropy did not show significant differences between scan delays of 30 and 180 seconds with DR greater than 0.90 between all time point pairs. When the range was narrowed down to 60 to 150 seconds, an additional 2 values (mean and homogeneity) showed stability. Among the 13 texture features, entropy, sphericity, discrete compactness, and GLCM entropy exhibited the lowest variability (coefficient of variation ≤5%). Most texture features exhibited stability with low variation between 60 and 150 seconds on DCE-CT. Thus, texture features extracted from contrast-enhanced CT with a scan delay range of 60 to 150 seconds can be used for tumor characterization despite the heterogeneity in delay time.

Low-Voltage, High-Pitch Computerized Tomography Angiography of the Infrarenal Aorta and Lower Extremity Vessels: Assessment of Radiation Dose, Image Quality With Hybrid Iterative Reconstruction, and Efficacy of Test Injection Using a Monitoring Scan at Knee Level.

Our aim was to assess image quality and radiation dose of low-voltage high-pitch computed tomography angiography of the infrarenal aorta and lower extremities and evaluate the efficacy of test injection technique using a monitoring scan at knee level. A total of 60 patients with suspected peripheral arterial disease were divided into 2 groups: group 1 (30 patients, 80 kVp, high pitch [3.2], and hybrid iterative reconstruction [sinogram-affirmed iterative reconstruction]) and group 2 (30 patients, 120 kVp, low pitch [1.0], and filtered back projection reconstruction). The test injection technique at knee level was used to determine the scan delay time in group 1. The image quality and radiation exposure were compared. There were significant differences between the 2 groups in mean (SD) arterial attenuation (80 vs 120 kVp: 507.78 [103.01] vs 317.54 [62.03] Hounsfield units, P < 0.001), mean (SD) signal-to-noise ratio (51.04 [20.29] vs 34.66 [9.94], P < 0.001), and contrast-to-noise ratio (44.83 [17.93] vs 28.26 [9.60], P < 0.001). No difference in subjective image quality was found between the 2 groups (all P > 0.05). The imaging time was significantly shorter in group 1 (2.70 [0.11] vs 14.65 [0.90s], P < 0.001). The mean (SD) effective dose was significantly lower in the 80 kVp group (0.76 [0.06] vs 4.29 [0.63] mSv, P < 0.001). The 80-kVp high-pitch computed tomography angiography of the lower limbs using sinogram-affirmed iterative reconstruction yields reduction of radiation exposure as well as obtains acceptable image quality if acquisition protocols are used in conjunction with the test injection technique using monitoring scan at knee level to determine the delay time.

Patient-Tailored Scan Delay for Multiphase Liver CT: Improved Scan Quality and Lesion Conspicuity With a Novel Timing Bolus Method

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. 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. 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). 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.

Determination of lowest possible contrast volume in computed tomography pulmonary angiography by using pulmonary transit time

The aim of this study was to assess the effectiveness of the modified test-bolus (mTB) method in computed tomography pulmonary angiography (CTPA). The Institutional Review Board approved this retrospective study. We reviewed 24 patients (nine men, 15 women; age range, 21-88years) in whom CTPA was performed either by Bolus-Tracking (BT) (n=12) or mTB (n=12) methods. Pulmonary transit time (PTT) was used to determine scan delay time and contrast volume in the mTB group. The contrast volume, radiation dose, quantitative measures, and qualitative scores of enhancement were compared. The chi-squared test, Mann-Whitney U test, and κ statistics were used. The significance level was 0.05. The effective dose (P=0.028) and contrast volume (P<0.001) was significantly lower in the mTB group than those in the BT group. The difference in the quantitative measures and qualitative scores of enhancement between groups was statistically insignificant (P=0.729, P=0.635, respectively). Significantly fewer artefacts were observed in the mTB group (P=0.024). By taking into account PTT, mTB appears to be a promising method for tailoring CTPA to the patient with the use of less contrast material and resulting in fewer artifacts.

Time dependency of bone density estimation from computed tomography with intravenous contrast agent administration

Our study has demonstrated that in contrast-enhanced multi-detector computed tomography (MDCT)-based bone density measurements, the scan delay time after contrast agent administration is a statistically significant variable for the derivation of quantitative computed tomography (QCT)-equivalent bone mineral density (BMD) values. Earlier investigators have proposed to derive QCT-equivalent BMD values from contrast-enhanced MDCT scans by using a merely density-based conversion equation. The purpose of this study was to investigate whether the scan delay after intravenous (IV) contrast agent administration might affect BMD values derived in this way. A retrospective data analysis was performed on 198 subjects who underwent standardized biphasic MDCT. Average densities values (in Hounsfield units) of lumbar vertebral bodies 1 to 3 (L1-L3) were compared between phases I and II of the biphasic MDCT scan. Furthermore, QCT-equivalent BMD (BMDQCT) values were calculated using a previously published conversion equation. Paired t-test analysis revealed that IV contrast agent administration leads to a statistically significant increase (8.6 %; p < 0.0001) in overall density of L1-L3 from phases I to II. Moreover, comparison of BMDQCT values between phases I and II reveals a change from osteoporotic to osteopenic in 4.5 % of the study population and from osteopenic to normal for 11.1 % of the subjects. Furthermore, it was revealed that the density increase from phases I to II shows a weak, yet statistically significant (p < 0.001) age dependency. Our study demonstrates that the use of a mere density-based conversion equation for deriving BMDQCT from MDCT scans ignores time dependency as an important variable. Furthermore, our results indicate that the actual age-dependent BMD itself might be another relevant variable that needs to be included in a MDCT-to-QCT conversion equation.

Comparison of pancreatic acinar cell carcinoma and adenocarcinoma using multidetector-row computed tomography

To distinguish acinar cell carcinoma (ACC) from pancreatic adenocarcinoma (AC) by comparing their computed tomography findings. Patients with ACC and AC were identified on the basis of results obtained using surgically resected pancreatectomy specimens. The preoperative computer tomographic images of 6 acinar cell carcinoma patients and 67 pancreatic adenocarcinoma patients in 4 phases (non-contrast, arterial, portal venous, and delayed phase) were compared. The scan delay times were 40, 70, and 120 s for each contrast-enhanced phase. The visual pattern, tomographic attenuation value, and time attenuation curve were assessed and compared between AC and ACC cases using the χ² test, Wilcoxon signed-rank test, and Mann Whitney U test. The adenocarcinomas tended to be hypodense in all 4 phases. The acinar cell carcinomas also tended to be hypodense in the 3 contrast-enhanced phases, although their computed tomographic attenuation values were higher. Further, 5 of the 6 acinar cell carcinomas (83%) were isodense in the non-contrast phase. The time attenuation curve of the adenocarcinomas showed a gradual increase through the 4 phases, and all adenocarcinomas showed peak enhancement during the delayed phase. The time attenuation curve of the acinar cell carcinomas showed peak enhancement during the portal venous phase in 4 cases and during the arterial phase in 2 cases. None of the 6 acinar cell carcinomas showed peak enhancement during the delayed phase. The tumor density in the non-contrast phase and time attenuation curve pattern clearly differ between acinar cell carcinomas and adenocarcinomas, and multidetector-row computed tomography can thus distinguish these tumors.

The evaluation of combined CT pulmonary and bronchial arteriography for the diagnosis of hemoptysis

To establish the method of multi-slice spiral CT pulmonary angiography (CTPA)combined with bronchial angiography (CTBA) and to evaluate its value for diagnosis and treatment in hemoptysis. After contrast material was administered intravenously, a 16-detector row helical CT scanner (Light Speed Ultra 16; GE Medical Systems) was used to complete CTPA first with a scan delay time of 12 - 16 s. Then CTBA was carried out, with a scan delay time of 26 - 28 s. The images were reformatted to evaluate the pulmonary artery and bronchial artery (BA). In 36 cases of hemoptysis, CTPA showed 7 pulmonary arterial abnormalities (3 cases with pulmonary embolism, 4 cases with one of pulmonary artery abnormity, primary pulmonary artery leiomyosarcoma, loss of sharpness of pulmonary artery or occlusion of right-inferior lung artery). In the 36 cases, CTBA showed 37 right BAs (11 tortuosity and thickening), 40 left right BAs (10 tortuosity and thickening) and 3 non-bronchial systemic arteries (1 from abdominal aorta tortuosity and thickening). Abnormal vessels had a close relation with pulmonary diseases. With this method CTPA and CTBA can be completed in a single procedure and abnormal pulmonary arteries and bronchial arteries can be shown clearly. This procedure maybe of important value for the diagnosis and treatment of hemoptysis.

Sixty-four MDCT achieves higher contrast in pancreas with optimization of scan time delay

To compare different multidetector computed tomography (MDCT) protocols to optimize pancreatic contrast enhancement. Forty consecutive patients underwent contrast-enhanced biphasic MDCT (arterial and portal-venous phase) using a 64-slice MDCT. In 20 patients, the scan protocol was adapted from a previously used 40-channel MDCT scanner with arterial phase scanning initiated 11.1 s after a threshold of 150 HU was reached in the descending aorta, using automatic bolus tracking (Protocol 1). The 11.1-s delay was changed to 15 s in the other 20 patients to reflect the shorter scanning times on the 64-channel MDCT compared to the previous 40-channel system (Protocol 2). HU values were measured in the head and tail of the pancreas in the arterial and portal-venous phase. Using an 11.1-s delay, 74.2 HU (head) were measured on average in the arterial phase and 111.2 HU (head) were measured using a 15-s delay (P < 0.0001). For the pancreatic tail, the average attenuation level was 76.73 HU (11.1 s) and 99.89 HU (15 s) respectively (P = 0.0002). HU values were also significantly higher in the portal-venous phase [pancreatic head: 70.5 HU (11.1 s) vs 84.0 HU (15 s) (P = 0.0014); pancreatic tail: 67.45 HU (11.1 s) and 77.18 HU (15 s) using Protocol 2 (P = 0.0071)]. Sixty-four MDCT may yield a higher contrast in pancreatic study with (appropriate) optimization of scan delay time.

Focal Liver Lesion Detection in Gadoxetic Acid-enhanced Liver MRI: Effects of Scan Delay, Hepatic Function, and Magnetic Field Strength

Purpose : To determine the effects of scan delay, hepatic function, and magnetic field strength on the performance of gadoxetic acid enhanced magnetic resonance imaging. Materials and Methods : Gadoxetic acid enhanced MRI conducted in 72 patients with 10 minutes and 20 minutes delay were reviewed retrospectively. For quantitative analysis, liver-to-lesion signal difference ratio (SDR) was measured and compared according to scan delay time, hepatic function and magnetic field strength. For qualitative analysis, two board-certificated radiologists reviewed 10-minute delay and 20-minute delay images. The sensitivity and specificity of each reader was compared. Results : The SDR of 20-minute images in non-cirrhotic patients was significantly higher (p 0.05) to 10-min delay images. In comparisons according to the magnetic strength, there was no significant difference between 1.5-T and 3.0-T systems. Comparisons of ROC curves showed no statistically significant differences in sensitivity and specificity between 10-minute and 20-minute delay images. Conclusion : An increase in the liver-to-lesion signal difference ratio was dependent on the patients'hepatic function but not dependent on the magnetic strength. There was no significant difference in sensitivity or specificity between the 10-minute and 20-minute delay images.

A prospective study to evaluate the depictability of the hepatic veins on abdominal contrast-enhanced CT in small children

The optimal conditions for abdominal contrast-enhanced (CE) CT, especially with respect to depiction of the hepatic veins (HVs), have not been well studied in small children. We compared the depiction of the HVs in small children using scan delay times of 50 s and 60 s and a power injector. The degree of contrast enhancement of the HVs according to body weight was also evaluated. A total of 50 CT studies in 31 children ages 2 days to 3 years 4 months (median 12 months) with a body weight less than 15 kg were prospectively evaluated. Nonionic contrast medium (300 mgI/ml) at a dose of 2 ml/kg and an injection rate calculated as (body weight in kilograms x 0.1) ml/s was injected through a 24-gauge intravenous catheter. Scan delay time was randomly chosen at 50 s or 60 s (25 times each). Subjective assessment of HV depiction was performed and the difference in CT number between the HV and hepatic parenchyma (HV-HP value) was calculated. In all cases, subjective assessment of HV depiction was good and the HV-HP value was greater than 20 HU. The mean+/-SD HV-HP value was 47.7+/-13.2 HU. There were no differences in the mean HV-HP values between scan delay times of 50 s and 60 s (P=0.58). For small children, this protocol for pediatric abdominal CECT resulted in good depiction of the HVs with no difference between scan delay times of 50 s and 60 s.

Choice of optimal phase for liver angiography and multi-phase scanning with multi-slice spiral CT

Objective To evaluate the effieaey of test bolus technique with multi-slice spiral CT (MSCT) for determining the optimal scan delay time in CT Hepatic artery (HA)-portal vein (PV) angiography and multi-phase scanning.Methods MSCT liver angiography and multi-phase scanning were performed in 187 patients divided randomly into two groups.In group A (n =59),the scan delay time was set according to the subjective experiences of operators; in group B (n=128),the scan delay time was determined by test bolus technique.Abdominal aorta and superior mesenteric,vein were selected as target blood vessels,and 50 HU was set as enhancement threshold value.20 ml contrast agent was injected intravenously and time-density curve of target blood vessels were obtained,then HA-PV scanning delay time were calculated respectively.The quality of CTA images obtained by using these 2 methods were compared and statistically analysed using Chi-square criterion.Resuits For hepatic artery phase,the images of group A are:excellent in 34(58%),good in 17(29%),and poor in 8 (13%),while those of group B are excellent in 128( 100%),good in 0(0%),and poor in 0(0%).For portal vein phase,the images of group Aare:excellent in 23(39%),good in 27(46%),and poor in 9(15%),while those of group B are excellent in 96 (75%),good in 28 (22%),and poor in 4 (3%) respectively.There was statistically significant difference between the ratios of image quality in group A and group B (X2=14.97,9.18,P < 0.05).Conclusion Accurate scan delay time was best determined by using test bolus technique,which can improve the image quality of liver angingraphy and multi-phase scanning. Key words: Angiography; Hepatic artery; Portal vein; Tomography,X-ray computed