Test Bolus Injection Research Articles

Double low-dose computed tomography (CT) angiography of craniocervical arteries using a test bolus of diluted contrast medium and a personalized contrast protocol

To prospectively assess the value of a test bolus of diluted contrast medium (CM) combined with a personalized contrast protocol in craniocervical computed tomography angiography (cc-CTA) with low radiation and CM doses. Eighty-six consecutive subjects were divided into two groups at random (43 in each one): group A: 100/Sn140 kVp, filtered back-projection reconstruction, iopromide (370 mgI/ml) 50 ml; group B: 80/Sn140 kVp, iterative reconstruction, iodixanol (270 mgI/ml). In group B, the test bolus contained 27 ml of diluted CM, a personalized protocol with low-concentration CM was used for angiography, and the test bolus injection duration in angiography remained the same. Artery values over 200 Hounsfield units were considered significant. Image quality for all cases was found to be diagnostic. No significant differences were found in the arterial densities of the ascending aorta or basilar artery between the groups. The values of the common carotid artery, internal carotid artery, and middle cerebral artery in group B were significantly lower. The effective dose and average iodine uptake were significantly lower in group B. With double-low-dose cc-CTA, test bolus scanning based on diluted CM combined with a personalized contrast protocol can yield diagnostic-quality images and significantly reduce the radiation and CM doses.

An Optimized Test Bolus Contrast Injection Protocol for Consistent Coronary Artery Luminal Enhancement for Coronary CT Angiography

Consistent levels of coronary artery enhancement are essential for quantitative analysis of coronary artery plaque. We studied three contrast injection protocols for coronary CT angiography (CCTA) and compared mean attenuation level and consistency of vascular contrast enhancement. We hypothesized that test bolus adjusted protocols will have a superior consistency of coronary attenuation compared to a weight-based protocol. We prospectively evaluated a standard test bolus injection protocol (protocol 1, 32 subjects) and an optimized test bolus injection protocol (protocol 2, 59 subjects) in comparison to a body weight-based injection protocol (60 subjects). The test bolus was diluted contrast (20%-30% iopamidol 370 mixed with normal saline); peak aortic attenuation was measured and used to calculate a specific water/contrast mixture for the CCTA. The mean attenuation of the coronary lumen was measured on CCTA. Metrics of optimum arterial enhancement included the percentage of patients within a predetermined range for coronary attenuation (325-500 HU) and optimal timing with maximal ascending aortic attenuation. In addition, interpatient variation in coronary enhancement was quantified as percentage standard deviation of the attenuation. The mean attenuation of the coronary arteries was similar in all protocols (362, 364, and 375 HU for the weight-based, test bolus 1 and 2 protocols, respectively). The percentage standard deviations of the weight-based, test bolus 1 and 2 protocols for coronary attenuation were 25.3%, 27.1%, and 10.5%, respectively (p < 0.0001). Test optimized bolus protocol 2 yielded the highest percentage of scans within the preferred coronary attenuation range (88%, p = 0.002). In test bolus protocol 2, the contrast timing was optimal in 73% of cases compared to only 22% of cases in the body mass guided injection protocol (protocol 1, p < 0.0001). An optimized test bolus guided injection protocol resulted in a marked reduction in variation in coronary enhancement for CCTA compared to a body weight-based injection protocol.

A non-invasive cardiac output measurement as an alternative to the test bolus technique during CT angiography

To investigate the association between a non-invasive cardiac output (CO) measurement and the scan delay, as derived from a test bolus injection protocol. The secondary objective was to determine which factors affect the relationship between the CO and scan delay. Fifty-five patients referred for a contrast-enhanced (thorax-)abdomen CT examination were included in this feasibility study. A test bolus examination was performed prior to the abdominal CT. During the test bolus injection, the CO of the patient was measured using a non-invasive finger-cuff measurement. Associations were analysed using linear regression analyses. Age, gender, height, weight, and blood pressure were included as potential confounders. Linear regression analysis showed a negative and significant association between CO and delay. The regression formula was as follows: scan delay (seconds)=26.8-1.6 CO (l/min), with a 95% CI between -2.3 and -1.0 (p<0.001). Weight appeared to be a confounder in this relation, and gender and blood pressure were effect modifiers. There was no interaction between scan delay and age, height and weight. There is a negative and significant association between the non-invasive CO measurement and the CT scan delay; however, to validate these findings a larger cohort study is needed to investigate whether the non-invasively determined scan delay is as accurate as the use of a test bolus.

Low-dose CT angiography of the abdominal aorta and reduced contrast medium volume: Assessment of image quality and radiation dose

To determine the effect of using 80kV tube voltage and a reduced amount of contrast medium on the image quality and radiation dose of computed tomography angiography (CTA) of the abdominal aorta. Patients who were referred for a CTA examination of the abdominal aorta were included in this technical efficacy study. Thirty patients were divided randomly into two groups. Fifteen patients underwent a dual-energy CT (DECT) protocol (Group A). Fifteen patients were scanned with the use of an automated tube potential selection algorithm tool (Group B). In both protocols, a test bolus injection of 10ml ioversol (350mg iodine/ml) was used, followed by 20ml of 1:1 saline-diluted contrast medium. Quantitative analysis comprised determination of the mean attenuation and contrast-to-noise ratio. Qualitative image analysis was performed independently by five radiologists. The estimated radiation dose in terms of CT dose index and effective dose was recorded and compared with a standard 120kV protocol. In Group B, six patients underwent CTA at 80kV, seven patients underwent CTA at 100kV and two patients underwent CTA at 120kV. The mean contrast-enhancement values of Group A (80kV) and the 80kV subgroup of Group B were 16.5% and 27.6% higher compared to the 100kV subgroup of Group B, these differences were, however, not significant. There were no significant differences in mean image quality between groups. In patients undergoing CTA at 80kV the effective dose decreased by up to 51.3% compared to a conventional 120kV CTA protocol. The findings of this study support the hypothesis that 80kV in CTA of the abdominal aorta can reliably be used with only 30ml contrast medium in total and a 50% reduction in radiation dose. The overall image quality was diagnostically adequate; however, it appeared to be suboptimal in patients with a BMI above 28kg/m(2).

Optimization of scan timing for aortic computed tomographic angiography using the test bolus injection technique.

With fast computed tomography (CT), it is possible for the scanning to outpace the contrast medium bolus during aortic CT angiography (CTA). To evaluate the effectiveness of a new method for reducing the risk of outpacing in which the scan start timing (ST) and speed can be estimated from the peak enhancement time measured at the femoral artery using a single test-bolus injection (femoral artery test injection method [FTI method]). In 30 cases of aortic CTA, we measured the time to peak enhancement at the femoral artery (TPF) and the ascending aorta (TPA) with test-bolus injection performed twice in each examination. From the resultant linear relationship between TPF and transit time (TT = TPF - TPA), we developed a method for determining the ST and TT from TPF. One hundred patients were assigned to two groups: FTI and bolus tracking (BT), each with 50 patients. CT values were measured in main vessels (ascending aorta, descending aorta, femoral artery). The CT values of the vessels and the rate of cases with more than 300 HU (good cases) were compared between the two groups. The enhancement in the FTI method was significantly higher than that of the BT method (average CT values: FTI, 388.3 ± 52.4; BT, 281.2 ± 59.1; P < 0.001). The rates of good cases for FTI and BT were 86.0% and 46.0%, respectively. The FTI method was very effective in reducing the risk of outpacing of the contrast medium transit in aortic CTA without the need for an additional contrast medium dose.

Reduction of contrast medium volume in abdominal aorta CTA: Multiphasic injection technique versus a test bolus volume

ObjectiveThe purpose of this study is to reduce the administered contrast medium volume in abdominal CTA by using a test bolus injection, with the preservation of adequate quantitative and qualitative vessel enhancement. Study designFor this technical efficacy study 30 patients, who were referred for a CTA examination of the abdominal aorta, were included. Randomly 15 patients were assigned to undergo a multiphasic injection protocol and received 89mL of contrast medium (Optiray 350) (protocol I). Fifteen patients were assigned to the test bolus injection protocol (protocol II), which implies injection of a 10mL test bolus of Optiray 350 prior to performing CTA with a 40mL of contrast medium. Quantitative assessment of vascular enhancement was performed by measuring the amount of Hounsfield Units in the aorta at 30 positions from the celiac trunk to the iliac arteries in both groups. Qualitative assessment was performed by three radiologists who scored the images at a 5-point scale. ResultsQuantitative assessment showed that there was no significant difference in vascular enhancement for patients between the two protocols, with mean attenuation values of 280.9±50.84HU and 258.60±39.28HU, respectively. The image quality of protocol I was rated 4.31 (range: 3.67/5.00) and of protocol II 4.11 (range: 2.67/5.00). These differences were not statistically significant. ConclusionThis study showed that by using a test bolus injection and the administration of 50mL of contrast medium overall, CTA of the abdominal aorta can reliably be performed, with regard to quantitative and qualitative adequate vessel enhancement.

Novel contrast-injection protocol for coronary computed tomographic angiography: contrast-injection protocol customized according to the patient’s time-attenuation response

We developed a new individually customized contrast-injection protocol for coronary computed tomography (CT) angiography based on the time-attenuation response in a test bolus, and investigated its clinical applicability. We scanned 60 patients with suspected coronary diseases using a 64-detector CT scanner, who were randomly assigned to one of two protocols. In protocol 1 (P1), we estimated the contrast dose to yield a peak aortic attenuation of 400 HU based on the time-attenuation response to a small test-bolus injection (0.3 ml/kg body weight) delivered over 9 s. Then we administered a customized contrast dose over 9 s. In protocol 2 (P2), the dose was tailored to the patient's body weight; this group received 0.7 ml/kg body weight with an injection duration of 9 s. We compared the two protocols for dose of contrast medium, peak attenuation, variations in attenuation values of the ascending aorta, and the success rate of adequate attenuation (250-350 HU) of the coronary arteries. The contrast dose was significantly smaller in P1 than in P2 (36.9 ± 9.2 vs 43.1 ± 7.0 ml, P < 0.01). Peak aortic attenuation was significantly less under P1 than under P2 (384.1 ± 25.0 vs 413.5 ± 45.7, P < 0.01). The mean variation (standard deviation) of the attenuation values was smaller in P1 than in P2 (25.0 vs 45.7, P < 0.01). The success rate of adequate attenuation of the coronary arteries was significantly higher with P1 than with P2 (85.0 vs 65.8 %, P < 0.01). P1 facilitated a reduction in the contrast dose, reduced the individual variations in peak aortic attenuation, and achieved optimal coronary CT attenuation (250-350 HU) more frequently than P2.

Cardiac Output Obtained from Test Bolus Injections as a Factor in Contrast Injection Rate Revision of Following Coronary CT Angiography

Optimal contrast enhancement is crucial for the detection of coronary artery stenoses and atherosclerotic changes in coronary CT angiography (CTA). To demonstrate the feasibility of using the cardiac output (CO) obtained from the test bolus injection data-set (COtest) as a factor in contrast injection rate revision of the following coronary CTA. The test bolus injection data-sets of 52 consecutive coronary CTAs were examined. COtest was calculated from the test bolus data-set. Aortic peak enhancement (APE) was measured on the following coronary CTA. We simulated the APE at a fixed contrast injection rate of 4 mL/s (simAPE) in each patient. The ranges of COtest and simAPE were 2.82-7.56 L/min and 194-527 Hounsfield Units, respectively. There was a significant negative correlation (R = -0.802, P < 0.001) between simAPE and COtest. COtest can be used for injection rate revision on coronary CTA.

Evaluation of ITA Graft Function Using CT Angiography

A less invasive method to assess internal thoracic artery (ITA) graft function after coronary artery bypass grafting (CABG) is desired. This study reports the novel method to estimate ITA graft function using CT angiography. Fifty ITA grafts were assessed. Hounsfield Unit transition of each graft on the same cross section was detected during the Test Bolus Injection, which led to the making of a time density curve (TDC), for each ITA. Variables from the TDC were compared statistically with data obtained from Pulse Doppler Echo (PDE), the best indicator of graft function, of ITA grafts. The ascending slope of the TDC was significantly associated with the following PDE data: Velocity time integral (VTI), VTI × Heart Rate (HR) and Mean Flow of ITA graft. A multivariate analysis showed an especially strong relationship with the ascending slope of the TDC and VTI × HR (R(2) = 0.588). The ascending slope of the TDC means the concentration transition of contrast media, which may be affected by the blood stream in the ITA graft. This study suggests the possibility of the ability to assess ITA graft function by CT angiography.

Dual-energy computed tomographic angiography of head and neck arteries with different contrast material doses in second generation dual-source computed tomography system

To explore the feasibility of a dual-energy computed tomographic angiography (DECTA) protocol using test-bolus injection with reduction of contrast material (CM) dose in second generation dual-source CT system. Totally 57 consecutive patients underwent CT angiography scan covering the cervical and cerebral arteries. CT was performed with second generation dual-source CT system. The time to peak (T) using a test-bolus injection was calculated. The patients were divided into three groups (A, B, and C) with different CM doses (40, 45, and 50 ml) and different delay time points [ (T+1) , (T+1) , and (T+2) s] . All the patients were followed by a 48 ml saline flush. Arterial enhancements were quantified by measuring attenuation values of the aortic arch, bifurcation of common carotid artery, contralateral internal jugular vein of the CM injection, superior vein cava, proximal middle cerebral artery, basilar artery, and straight sinus on source images. Visualizations of intracranial artery and ipsilateral venous effect of the CM injection were rated on a four-point grading scale on CTA images for qualitative assessment. Although the attenuation of internal jugular vein and straight sinus were significantly lower in group A than in groups B and C (P<0.05) , the attenuation of aortic arch, superior vein cava, common carotid artery, middle cerebral artery, and basilar artery vessels showed no significant differences among these three groups. The scores of the visualizations of intracranial artery and ipsilateral venous effect of the CM injection were also not significantly different among these three groups. Based on the delay time calculated by a test-bolus injection, a reduced-dose contrast material may provide an equal degree of arterial attenuation and a lower attenuation of vein for dual-energy CTA covering the craniocervical region in second generation dual-source CT system.

Comparison of two different injection rates of gadoxetic acid for arterial phase MRI of the liver

To compare two different injection rates for gadoxetic acid-enhanced hepatic arterial phase images on hepatic dynamic MRI. Hepatic arterial phase images were obtained after an intravenous bolus injection of gadoxetic acid at a rate of 1 mL/second in 62 patients and 2 mL/second in 64 patients on a 3 Tesla MR scanner using a test-bolus injection method. The signal-to-noise ratios (SNR) of the liver, portal vein, hepatic vein, aorta, spleen and pancreas were measured. The contrast-to-noise ratio (CNR) of hypervascular hepatic tumors was calculated. Two radiologists independently scored items to evaluate image quality of hepatic arterial phase and detected hypervascular hepatocellular carcinoma (HCC). The SNR of the aorta on the arterial phase images was significantly higher in the 1 mL/second group (235.43 +/- 82.59) than in the 2 mL/second group (190.94 +/- 96.90, P < 0.05). The SNRs of the liver, spleen and pancreas, the CNRs of hypervascular hepatic tumors, the detection rate of hypervascular HCC and subjective ratings for the optimal arterial enhancement were comparable between the two groups. Injection rates of 2 mL/second and 1 mL/second provided comparable image qualities on arterial phase images of hepatic dynamic MRI using gadoxetic acid.

Effect of cardiac function on aortic peak time and peak enhancement during coronary CT angiography

Purpose To examine the manner in which cardiac function affects the magnitude and timing of aortic contrast enhancement during coronary CT angiography (CTA). Materials and methods Twenty-nine patients (21 men, 8 women; mean age, 64.4 ± 13.4 years; mean weight, 59.4 ± 10.3 kg) underwent measurement of cardiac output within 2 weeks of coronary CTA. The cardiac output of each patient was measured by the thermodilution technique and the cardiac index was calculated from the body surface area. During coronary CTA, attenuation of the descending aorta was measured at the workstation every 3 s. The aortic peak time (APT) and aortic peak enhancement (APE) of each patient were calculated. Pearson's correlation coefficient analysis was used to investigate the relationships between the cardiac output or cardiac index and APT or APE. Furthermore, the relationship between patient factors or parameters on test bolus injection and APT or APE was also evaluated. Results The range of cardiac output, cardiac index, APT, and APE was 1.55–10.46 L/min (mean: 4.77 ± 2.13), 1.11–5.30 L/(min-m 2) (mean: 3.28 ± 1.08), 25–51 s (mean: 38.3 ± 7.5), and 273.1–598.1 HU (mean: 390.4 ± 72.1), respectively. With an increase in the cardiac index, both APT ( r = −0.698, p < 0.0001) and APE ( r = −0.573, p = 0.0009) decreased. There were significant correlations between the patient body weight and APT and APE with the test bolus injection, and with APT and APE during coronary CTA. Conclusion The APT and APE during coronary CTA are closely related to cardiac function.

The comparison of imaging quality between bolus-triggering and test-bolus technique used in 64-slice spiral CT angiography of lower extremity arteries

Objective To investigate the clinical value of multi-slice CT angiography (MSCTA) of lower limbs in patients with peripheral arterial occlusive disease (PAOD) using the test-bolus technique.Methods Forty-four patients with PAOD were enrolled consecutively in the study.In group I, 18 subjects underwent CTA by bolus triggering method and in group 2, 26 subjects underwent CTA by test-bolus technique.During scanning procedure in group 2 subjects, the bolus transit time to aorta ( TAO ), popliteal arteries (Tpop ) and aorto-popliteal bolus transit time (T,) were calculated through dynamic acquisition at their respective level and the delay time were immediately set as TAO and scan time as double Tt.Two independent senior attending physicians with training experience in interpreting CTA determined the quality of each arterial segment visualization based on 5 parameters (1.visible farthest branch, 2.clarity of vessels border, 3.presence of venous contamination, 4.grading of stenosis, 5.CT value at 4 arterial segments).Inter-observer agreement on imaging quality between readers was evaluated using Cohen's k statistic by calculating K values.X2 test and t test were used to compare the quality of images in both groups.Results In group 2 patients,a larger individual variation in transit time of the contrast to reach aorta was obserued [ TAO = ( 17.1 ± 2.6) s with a range of 12.0—22.0 s ] and aorto-popliteal transit time [ Tt = ( 14.8 ± 5.5 ) s with a range of 8.0—24.0 s ].CTA of group 2 patients demonstrated bettor quality over group I patients' CTA, especifieally in the infra-pop|iteal and foot area arteries. There was an excellent inter-observer agreement for group 2 patients ( K ＞ 0.80 ) whereas in group 1 agreement in infra-popliteal segments for venous contamination ( K value 0.60 ) and stenosis degree ( K value 0.50 ) were not satisfactory enough.Group 1 patients were reported to have more severe stonosis in infra-popliteal and foot arteries( X2 = 30.55 and22.41,P＜0.01).Conclusion There was a wide interindividual variation in transit time for contrast medium to reach aorta and pollteal artery. Adaptive method by using two low-dose test bolus injection determined interindividual variation in delay time and scan time and thus above parameters was able to produce better quality images than using bolus triggering technique in below knee and foot region arteries. Key words: Tomography,spiral computed; Angiography; Arterial occlusive diseases

新しい造影方法であるｔｅｓｔ ｂｏｌｕｓ ｔｒａｃｋｉｎｇ法の開発と，冠状動脈ＣＴ造影検査における有用性について

The test bolus tracking (TBT) method is a new injection method of contrast medium that we developed. The TBT method is an injection technique that continuously performs the test bolus injection and the main bolus injection, such that the best acquisition of scan timing and the improvement of examination efficiency can be expected. We compared the TBT method and the test injection method by coronary CT angiography. The results demonstrated that the contrast enhancement of the coronary arteries was high and the variation of the CT value was also small in the TBT method. When the scan timing expected by the TI method and the TBT method were compared, it was different of two seconds or more by the case with 43%. However, the variation of CT value was small for the TBT method in these cases. Therefore, the TBT method is a very useful method for CCTA.

Patient-specific Contrast Injection Protocols for Cardiovascular Multidetector Row Computed Tomography

To develop patient-specific contrast injections for uniform enhancement of cardiovascular multidetector row computed tomography (MDCT) images. Sixty-two patients were imaged using electrocardiogram (ECG)-gated spiral MDCT. Thirty patients (group 1) received a uniphasic injection; the remaining 32 patients (group 2) received patient-specific multiphasic injections. For group 2 patients, the vasculature between injection and imaging sites was considered a "gray box" whose transfer function was determined from a test bolus injection and the resulting enhancement in the left side of the heart. This transfer function was used to determine the injection necessary to achieve 250 Hounsfield units in the left side of the heart. Intraindividual and interindividual variation of enhancement were determined for both groups. Superior vena cava (SVC) artifacts were graded on a 4-point scale. The measured indices of intraindividual variation were significantly smaller in group 2 than in group 1 (P < 0.05), indicating improved uniformity with patient-specific injections. The interindividual variation of mean enhancement in group 2 was smaller than in group 1, but the difference was not significant. The severity of SVC artifacts was significantly reduced (P < 0.05) for thinner patients (<83 kg) in group 2 compared with similar patients in group 1. Patient-specific multiphasic contrast injections yielded more uniform enhancement in the left side of the heart on MDCT images with reduced intraindividual variation of enhancement compared with standard uniphasic injections. Patient-specific injections also reduced SVC artifacts in patients <83 kg.

Preoperative Evaluation of Perigastric Vascular Anatomy by 3-Dimensional Computed Tomographic Angiography Using 16-Channel Multidetector-Row Computed Tomography for Laparoscopic Gastrectomy in Patients With Early Gastric Cancer

The purpose of this study was to evaluate the efficacy of 3-dimensional computed tomographic angiography (3D CTA) using 16-channel multidetector-row helical computed tomography (MDCT) in the preoperative visualization of laparoscopic gastrectomy for early gastric cancer. Twenty consecutive patients with early gastric cancer who underwent computed tomographic (CT) examination using 16-channel MDCT (0.625 mm x 16) before surgery were included in this study. At a rate of 4 mL/s, 2 mL/kg of 300 mg I/mL contrast material was intravenously injected. Timing for arterial phase scanning was determined by using a test bolus injection. Portal phase imaging was performed 70 seconds after the start of bolus injection. By using volume rendering and maximum intensity projection techniques, 3D CT angiograms of perigastric vessels were reconstructed from CT images of 0.625-mm thickness on computer workstations. In all cases, the left gastric artery (LGA) and the right gastric artery were correctly identified on 3D CTA, and the left gastric vein was also depicted on 3D CTA in all cases. In 2 cases, the aberrant left hepatic artery from LGA was correctly identified on 3D CTA. In 1 case, the accessory LGA from the left hepatic artery was correctly identified on 3D CTA. The variations of the veins included the left gastric vein flowing into the portal vein in 10 cases: the splenic vein in 9 and the junction of the portal and splenic veins in 1. A 3D CTA reconstructed from 16-channel MDCT images clearly revealed perigastric vascular anatomy in all cases, which is important for laparoscopic gastrectomy. Three-dimensional CTA is useful for the preoperative visualization of laparoscopic gastrectomy.

Quantitative prediction of contrast enhancement from test bolus data in cardiac MSCT

The purpose of this study was to evaluate a new algorithm for the prediction of contrast enhancement from test bolus data in cardiac multislice spiral computed tomography (MSCT). An algorithm for the prediction of contrast enhancement using test bolus data was developed. A total of 30 consecutive patients (15 male, 69.5 +/- 9.6 years) underwent cardiac MSCT (12 x 0.75 mm, 120 kV, 500 mAs(eff.)) with a biphasic contrast material injection protocol. Contrast timing was derived from a standard 20 ml test bolus injection. Based on the test bolus time attenuation curves, expected enhancement values were computed for the ascending and descending aorta and the pulmonary trunk and compared with measured data from the cardiac CT scan. At the level of the test bolus measurement in the ascending aorta, the corresponding attenuation values were 309.4 +/- 49.6 Hounsfield Units (HU) for the predicted and 285.6 +/- 42.6 HU for the measured attenuation, respectively. The mean deviation between predicted and measured CT values was 32.8 +/- 48.2 HU (upper and lower limits of agreement 101.4/-53.8 HU), indicating a slight systematic tendency for overestimation. For 80% of the patients the prediction error was less than 50 HU. Prediction of contrast enhancement in cardiac MSCT from test bolus data is feasible with a relatively small mean deviation; 80% of the predictions were within a range that might be acceptable for routine clinical application.

Neuroradiological Diagnostic Tools: New MRI Perspectives

MR angiography5,17 is traditionally divided into “non-contrast enhanced” (NCE MRA) and “contrast-enhanced” (CE MRA) techniques. Contrast-enhanced techniques were initially developed to solve some of the problems encountered with non-contrast-enhanced methods, namely the long examination times, pulsatile flow artefacts, saturation when the mean blood flow is slow or when the imaging slice is parallel to the vessel, the characteristic problems of time of flight (TOF) acquisitions, and the need to define a priori beforehand the velocity sensitivity for phase contrast (PC) acquisitions. Currently used contrast-enhanced techniques 7,8,15,18 are based on the acquisition of 3D gradient-echo sequences synchronized at the first passage of contrast medium by different strategies (detection of a test bolus injection, automated triggering, fluoroscopic imaging). Basically, contrast medium is administered to counteract saturation induced by slow blood flow or flow directed parallel to the imaging slice. Contrast medium serves to obtain a “static” image of vascular structures with acquisitions times ranging from a few seconds to 1–2 minutes. To avoid venous contamination, different methods have been used to collect data (centric-approach, elliptical-centric phase encoding order, etc.) in an attempt to record first the information relating to low spatial frequencies (contrast data) with respect to high spatial frequencies (detail and contour data).

Measurement of cardiac output from a test-bolus injection in multislice computed tomography.

The aim of this study was to assess the feasibility of non-invasive determination of cardiac function from test-bolus data in multislice spiral computed tomography (MSCT). In 25 patients enhancement data gathered from a standardized test-bolus injection were analyzed. The test-bolus examination was performed prior to a retrospectively ECG-gated MSCT of the heart. A time-attenuation curve was obtained in the ascending aorta at the level of the pulmonary arteries. A gamma variate fit was applied to the curve in order to exclude recirculation and get pure first-pass data. Using the known amount of iodine injected, cardiac output (CO), and stroke volume (SV) were determined from integration of the fitted contrast enhancement curve using a reformation of the Stewart-Hamilton equation. Results were compared with CO and SV calculated from the geometric analysis of the retrospectively gated MSCT data using the ARGUS Software (Siemens, Forchheim, Germany). The CO and SV determined from test-bolus analysis and from geometric analysis correlated well with Pearson's correlation coefficients of 0.87 and 0.88, respectively. The standard deviation of the difference between both methods was 0.51 l/min for CO (8.6%) and 11.0 ml for SV (12.3%). Non-invasive quantification of CO seems to be feasible from a standard test-bolus injection. It provides valuable information on cardiac function without additional radiation or application of contrast material.

Analysis of cardiopulmonary transit times at contrast material-enhanced MR imaging in patients with heart disease.

To build a database of arm-to-aorta circulation times for contrast enhancement and to determine if measured transit times can help in discrimination between patients with and patients without heart disease. Findings at test-bolus examinations performed before acquisition of contrast material-enhanced magnetic resonance (MR) angiographic images of the head and neck were retrospectively reviewed. The times from test-bolus injection to first and peak enhancement in regions of interest were recorded in 77 patients with coronary artery disease, left ventricular hypertrophy, and/or impaired left ventricular function and 33 control subjects. Transit times in patients and control subjects were compared with Student t test. Linear regression was performed to measure the correlation coefficient. Transit times in patients with heart disease, including those with a normal ejection fraction, were significantly prolonged compared with those in control subjects (P <.05). Mean time to peak enhancement in the carotid artery bifurcation was 16.6 seconds +/- 1.9 (SD) and 20.8 seconds +/- 3.9 in control subjects and patients, respectively. Threshold value of 18 seconds for time to peak signal intensity in the carotid artery bifurcation provided highest combination of sensitivity and specificity. All (11 of 11) patients with an ejection fraction less than 40% and only three (9%) of 33 control subjects had circulation times greater than this threshold. No significant correlation was found between transit times and age, sex, weight, and height. Transit times measured with MR imaging may help in discrimination between patients with and patients without heart disease, independently of other cardiac functional parameters.