Test Bolus Technique Research Articles

Cervicocerebral Computed Tomography Angiography for Older Patients Based on Time to Peak and Number of Time Points to Peak in the Test Bolus Technique.

This study sought to optimize image quality and reduce the contrast dose by adjusting contrast agent and normal saline doses used in cervicocerebral computed tomography angiography (CTA) of older patients. Older patients who underwent cervicocerebral CTA were divided into group A (n = 110) and group B (n = 124). In the angiography scan, patients in group A were injected with 1.0 mL/kg contrast agent, followed by 40 mL saline chaser. In group B, contrast agent and normal saline doses were adjusted based on time to peak and number of time points to peak in the test bolus technique. The CT attenuation values, noise, signal-to-noise ratio, and contrast-to-noise ratio of target arteries and the right transverse sinus were objectively compared. Compared with group A, the contrast retention and artifacts in the right subclavian vein, right brachiocephalic veins, and superior vena cava were significantly decreased in group B. Furthermore, in group B, the noise at the bifurcation of the right common carotid artery increased by 1.7%, and the signal-to-noise ratio of the left middle cerebral artery M1 segment decreased by 6.6%. The contrast dose in group B decreased significantly (18.2%) as compared with group A. Based on time to peak and number of time points to peak with the test bolus, adjusting contrast and normal saline doses in cervicocerebral CTA for older people reduces contrast retention and artifacts in the veins of the injection side. Further, it also decreases the contrast dose needed to obtain image quality that satisfies diagnostic requirements.

Optimization of Preprocedural Full-cycle Computed Tomography in Patients Referred for Transcatheter Tricuspid Valve Repair: Test Bolus Versus Bolus Tracking.

Advancements in transcatheter mitral and tricuspid valve repair have resulted in growing demands in preprocedural computed tomography (CT) imaging. Due to the introduction of multidetector CT (MDCT), shorter acquisition times as well as high rates of heart failure and arrhythmias in this specific patient population, optimal synchronization between the passage of contrast agent and data acquisition is mandatory. There is no consensus on which acquisition technique should be used in this patient population. We aimed to optimize our preprocedural CT protocol comparing bolus tracking (BT) and test bolus (TB) techniques. We performed a retrospective analysis on 151 patients referred for full-cycle MDCT evaluation for transcatheter tricuspid valve repair comparing BT with TB (BT n=75 TB n=75). Contrast-to-noise ratios (CNR) were obtained. Demographic data, laboratory, electrocardiographic, and transthoracic echocardiography/transoesophageal echocardiography parameters were collected from electronic health records. Also, the volume of contrast agent and saline chaser and radiation dose length product and milliampere seconds were collected. BT and TB resulted in comparable CNR (BT: 0.47 [0.34 to 0.98]; TB: 0.51 [0.41 to 1.40]; P =0.1). BT was associated with a shorter scan duration (BT: 8.3min [4.1 to 24.4]; TB: 13.9min [6.2 to 41.4]; P <0.001), less radiation in terms of dose length product (BT: 1186±585; TB: 1383±679, P =0.04), and lower total volume administration (BT: 101mL [63 to 16]; TB: 114mL [71 to 154]; P <0.001). In patients with severely impaired ejection fraction (left ventricular ejection fraction [LVEF] ≤35%; n=65 [TB n=31; BT n=34]) using the TB technique yielded significantly better image quality in terms of CNR (TB=0.57 [0.41 to 1.07); BT=0.41 [0.34 to 0.65]; P =0.02). In patients with impaired LVEF (LVEF≤35%), the TB technique yielded significantly superior image quality and may be the preferred approach in this specific patient population. BT showed advantages in terms of shorter duration, less radiation, and lower contrast agent volume.

Optimization of the Parameters for the Test Bolus Technique in Computed Tomography Angiography of Head and Neck.

The aim of the study was to optimize low-dose scanning protocols for the test bolus technique in 64-detector computed tomography (CT) angiography (CTA) of the head and neck. A total of 250 patients were randomly divided into 5 groups of 50 patients each: conventional group (group A: 120 kV, 100 mA) and low-dose groups (group B: 100 kV, 100 mA; group C: 100 kV, 50 mA; group D: 80 kV, 100 mA; and group E: 80 kV, 50 mA). Subjective scores and objective measurements (CT values of the aortic arch, image noise, and signal-to-noise ratio) were used to evaluate the image quality and compare the radiation doses of the 5 groups. The image quality of the 5 groups met the diagnostic requirements, with no significant difference in the subjective evaluation findings (P > 0.05). There were significant differences in the CT values between the conventional group and low-dose groups (P < 0.05); however, there was no significant difference between groups B and C and between groups D and E (P > 0.05). Moreover, the volume CT dose index and dose length product of groups B, C, D, and E decreased by 37.62%, 70.45%, 65.28%, and 83.39%, respectively, compared with those of group A. Although the image noise of the low-dose groups increased, an appropriate reduction in the tube voltage enhanced the contrast medium-induced x-ray attenuation and increased the CT value, which resulted in a nonsignificant difference in the signal-to-noise ratio. Therefore, the image quality of the low-dose groups was not affected compared with that of the conventional group. In the test bolus technique in 64-detector CTA, the low-dose protocol of using 80 kV and 50 mA reduces the radiation dose by 83.39% compared with the conventional scan, without affecting the image quality.

The feasibility of low iodine dynamic CT angiography with test bolus for evaluation of lower extremity peripheral artery disease.

This study aims to determine if low iodine dynamic computed tomography angiography performed after a fixed delay or test bolus acquisition demonstrates high concordance with clinical computed tomography angiography (using a routine amount of iodinated contrast) to display lower extremity peripheral arterial disease. After informed consent, low iodine dynamic computed tomography angiography examination (using either a fixed delay or test bolus) using 50 ml of iodine contrast media was performed. A subsequent clinical computed tomography angiography using standard iodine dose (115 or 145 ml) served as the reference standard. A vascular radiologist reviewed dynamic and clinical computed tomography angiography images to categorize the lumen into "not opacified", "<50% stenosis", " 50 ̶70% stenosis", ">70% stenosis", and "occluded" for seven arterial segments in each lower extremity. Concordance between low iodine dynamic computed tomography angiography and the routine iodine reference standard was calculated. The clinical utility of 4D volume-rendered images was also evaluated. Sixty-eight patients (average age 66.1 ± 12.3 years, male; female = 49: 19) were enrolled, with 34 patients each undergoing low iodine dynamic computed tomography angiography using fixed delay and test bolus techniques, respectively. One patient assigned to the test bolus group did not undergo low iodine computed tomography angiography due to unavailable delayed time. The fixed delay was 13 s, with test bolus acquisition resulting in a mean variable delay prior to image acquisition of 19.5 s (range; 8-32 s). Run-off to the ankle was observed using low iodine dynamic computed tomography angiography following fixed delay and test bolus acquisition in 76.4% (26/34) and 100% (33/33) of patients, respectively (p = 0.005). Considering extremities with run-off to the ankle and without severe artifact, the concordance rate between low iodine dynamic computed tomography angiography and the routine iodine reference standard was 86.8% (310/357) using fixed delay and 97.9% (425/434) using test bolus (p < 0.001). 4D volume-rendered images using fixed delay and test bolus demonstrated asymmetric flow in 57.7% (15/26) and 58.1% (18/31) (p = 0.978) of patients, and collateral blood flow in 11.5% (3/26) and 22.6% (7/31) of patients (p = 0.319), respectively. Low iodine dynamic computed tomography angiography with test bolus acquisition has a high concordance with routine peripheral computed tomography angiography performed with standard iodine dose, resulting in improved run-off to the ankle compared to dynamic computed tomography angiography performed after a fixed delay. This method is useful for minimizing iodine dose in patients at risk for contrast-induced nephropathy. 4D volume-rendered computed tomography angiography images provide useful dynamic information.

Pulmonary embolism: Low dose contrast MSCT pulmonary angiography with modified test bolus technique

PurposeThis study aims to prove that the test bolus technique provides a better selective imaging study of the pulmonary arterial system in comparison to the automatic bolus-tracking technique. MethodA prospective study included 600 patients, classified into 2 groups where each group consisted of 300 patients. In group A, we used the bolus tracking technique with 80−100 ml of contrast while in group B test bolus technique was used with 50 mL of contrast. ResultsIt was clear that the Main PA average density was 260.5 HU in group A and increased to 320 HU in group B with P value < 0.002. The Ascending aorta average density decreased from 250 HU in group A to 130 HU in group B with P value <.001. The average score was increased by 35 % (from 1.75 in group A to 2.8 in group B with P value < .001). The Volume of IV contrast needed decreased by 40 % in group B compared to group A. ConclusionMSCTPA using test bolus method reduces the amount of the contrast used with better opacification of the pulmonary artery and its sub segmental branches in addition to reduced artifact.

Triple-phased mesenteric CT angiography using a test bolus technique for evaluation of the mesenteric vasculature and small intestinal wall contrast enhancement in dogs.

Computed tomography angiography is widely used for the assessment of various mesenteric vascular and bowel diseases in humans. However, there are only few studies that describe CT angiography application to mesenteric vessels in dogs. In this prospective, experimental, exploratory study, the mesenteric vasculature and enhancement pattern of the intestinal wall were evaluated on triple-phase CT angiography, and improvement of the visibility of vasculature was assessed on multiplanar reformation, maximum intensity projection, and volume rendering technique. After test bolus scanning at the level of the cranial mesenteric artery arising from the aorta, mesenteric CT angiography was performed in 10 healthy, male, Beagle dogs. Scan delay was set based on time-to-attenuation curves, drawn by placing the regions of interest over the aorta, intestinal wall, and cranial mesenteric vein. Visualization and enhancement of mesenteric arteries and veins were evaluated with multiplanar reformation, maximum intensity projection, and volume rendering techniques. The degree of intestinal wall enhancement was assessed on the transverse images in precontrast, arterial, intestinal, and venous phases. Pure arterial images were obtained in the arterial phase. Venous phase images allowed good portal vascular mapping. All CT angiography images were of high quality, allowing for excellent visualization of the anatomy of mesenteric vasculature including the small branches, particularly on maximum intensity projection and volume rendering technique. Distinct contrast enhancement of the intestinal wall was observed in both intestinal and venous phases. Findings indicated that this technique is feasible for the evaluation of mesenteric circulation in dogs.

Optimal Region of Interest Location of Test Bolus Technique in Extra Cranial Carotid Contrast Enhanced Magnetic Resonance Angiography

This study is aimed to optimize a location of region of interest (ROI) in test bolus carotid contrast enhanced magnetic resonance angiography (CE-MRA) at 3.0T. A total of consecutive 270 patients with no cardiovascular and vessel diseases were selected. Patients underwent elliptical centric 3D CE-MRA with the test bolus technique to identify the individual arterial arrival time. Quantitative measurements were performed by drawing ROIs of 25 ㎟ and signal intensities (SI) were measured in the center of common carotid artery (CCA), internal carotid artery (ICA) and aortic arch (AA). As a result, ROIs located within AA showed a significantly clarified arterial peak and over three times increased SI, while no significant arterial peak time differences were observed compared to ROIs located within CCA. In conclusion, it was demonstrated that the aortic arch is the optimal position to locate ROI in test bolus images of the carotid CE-MRA.

The effect of arm positioning on timing and enhancement of intravenous contrast media at coronary computed tomography angiography.

Adequate intravenous contrast media (CM) enhancement is crucial for evaluation of the coronary arteries. To compare the timing and enhancement of intravenous CM at coronary computed tomography angiography (CCTA) when positioning the arms in the traditional superior direction with that of positioning them in the ventral direction during the CM injection. One hundred patients were randomized into two groups. Group A (n = 50) had their arms positioned in the superior direction, resting on a head and arm support. Group B (n = 50) held their arms resting on the front panel of the computer tomography (CT) scanner. Scanning delay time was defined by test bolus technique. A total of 60 mL iodixanol, 320 mg/mL, was followed by a 50 mL saline flush at 6 mL/s. Cardiac output (CO) and heart rate (HR) were obtained before scanning. The attenuation was calculated by placing regions of interest (ROI) in ascending aorta, left atrium, and inferior vena cava. More patients in group A compared with group B (26 versus 14) showed a higher attenuation of the left atrium in comparison to the ascending aorta (P < 0.05). Body weight (BW) and CO were significantly related to the attenuation of ascending aorta (P < 0.01). By placing the arms in a ventral, instead of superior position the frequency of too early imaging at CCTA can be reduced.

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.

Qualitative indices and enhancement rate of CT pulmonary angiography in patients with suspected pulmonary embolism: Comparison between test bolus and bolus-tracking methods.

Background:The aim of the present study was to assess the qualitative indices and enhancement rate of computed tomographic pulmonary angiography (CTPA) in patients with suspected pulmonary embolism using Test bolus and Bolus-tracking techniques.Materials and Methods:Fifty-two patients with suspected pulmonary embolism that passed informed consent were randomly divided in the two groups. In each group, demographic characteristics, qualitative indices, and enhancement rate of CTPA were recorded.Results:The diagnostic result obtained in majority of the participants in the two groups (88.5 % in Test bolus group vs. 73.1% in the Bolus tracking group). In the case of quantitative variables, no statistically significant differences were found between the groups (P > 0.05). The only statistically significant difference between the two groups is average of “X-ray dose”.Conclusion:The results of our study show that there is no statistically significant difference between the Bolus Tracking and Test Bolus techniques for producing more homogeneous enhancement.

Enhancement Characteristics of the Computed Tomography Pulmonary Angiography Test Bolus Curve and Its Use in Predicting Right Ventricular Dysfunction and Mortality in Patients With Acute Pulmonary Embolism.

The purpose of the study was to evaluate the relationship between computed tomography pulmonary angiography (CTPA) test bolus curve data and mortality in patients with pulmonary embolism (PE) in comparison with conventional methods of right ventricular (RV) dysfunction. The study was approved by our institutional review board and is HIPAA-compliant. We retrospectively evaluated consecutive CTPA studies performed with a test bolus technique in a 2-year period. A time-density curve was derived from each test bolus. For comparison, left ventricular (LV) and RV dimensions (area, diameter) and PE load score (Qanadli method) were measured using CT data. A cardiologist blinded to the clinical and other imaging data reviewed a subset of the corresponding echocardiographic images to assess for RV dysfunction. Demographic data, mode of treatment, and patient outcome information were gathered using electronic medical records. Test bolus and anatomic data were correlated with PE-related mortality. A total of 71 patients (34 men and 37 women, average age 54.4 y) who had a CTPA performed using a test bolus technique were diagnosed with acute PE. Factors that significantly correlated with PE-related mortality on univariate analysis were: age above 60 years (odds ratio 19.1, P = 0.05), RV/LV diameter >1.5 (odds ratio 48.8, P < 0.001), RV/LV area >1 (odds ratio 8.6, P = 0.06), bolus curve upslope time >6 seconds (odds ratio 23.3, P = 0.04), 50% downslope time >6 seconds (odds ratio 20, P = 0.01), and embolus load score >15 (odds ratio 25, P = 0.03). The predictive value of upslope time (Exp(B) 1.65, P = 0.05), RV/LV diameter (Exp(B) 43.8, P = 0.01), and RV/LV area (Exp(B) 16.7, P = 0.01) were confirmed to be statistically significant in multivariate analyses. Data from the CTPA timing bolus curve provide prognostic value similar to the best conventional methods for predicting PE-related mortality.

Prediction of Aortic Enhancement on Coronary CTA Images Using a Test Bolus of Diluted Contrast Material

The purpose of our study was to compare test bolus techniques using undiluted or diluted contrast material for their ability to predict aortic enhancement on coronary computed tomographic angiography (c-CTA) images. We divided 200 consecutive patients who underwent c-CTA on a 64-MDCT scanner into two groups. In group A (n=100), we used a test bolus of undiluted contrast material and in group B (n=100), the contrast material was diluted. The injection volume was body weight×0.2 (contrast material 100%) in group A and body weight×0.7 (contrast material 30%, saline 70%) in group B. We then compared the CT number in the ascending aorta on c-CTA images obtained with undiluted and diluted contrast media to the CT number on c-CTA images. The mean CT number in the ascending aorta was significantly higher in group B than group A (217.1 vs. 157.4HU, P<.001). There was a significant difference in the correlation between the CT number of the ascending aorta on c-CTA images and on images acquired with the test bolus using undiluted or diluted test bolus (P<.001). In group B, the correlation had a strong positive linear relationship (r=0.72, P<.001), whereas in group A the positive linear relationship was weak (r=0.36). The test bolus with diluted contrast material was useful for predicting aortic enhancement before c-CTA scanning.

Low contrast volume run-off CT angiography with optimized scan time based on double-level test bolus technique – feasibility study

PurposeTo verify the technical feasibility of low contrast volume (40mL) run-off CT angiography (run-off CTA) with the individual scan time optimization based on double-level test bolus technique. Materials and methodsA prospective study of 92 consecutive patients who underwent run-off CTA performed with 40mL of contrast medium (injection rate of 6mL/s) and optimized scan times on a second generation of dual-source CT. Individual optimized scan times were calculated from aortopopliteal transit times obtained on the basis of double-level test bolus technique – the single injection of 10mL test bolus and dynamic acquisitions in two levels (abdominal aorta and popliteal arteries). Intraluminal attenuation (HU) was measured in 6 levels (aorta, iliac, femoral and popliteal arteries, middle and distal lower-legs) and subjective quality (3-point score) was assessed. Relations of image quality, test bolus parameters and arterial circulation involvement were analyzed. ResultsHigh mean attenuation (HU) values (468; 437; 442; 440; 342; 274) and quality score in all monitored levels was achieved. In 91 patients (0.99) the sufficient diagnostic quality (score 1–2) in aorta, iliac and femoral arteries was determined. A total of 6 patients (0.07) were not evaluable in distal lower-legs. Only the weak indirect correlation of image quality and test-bolus parameters was proved in iliac, femoral and popliteal levels (r values: −0.263, −0.298 and −0.254). The statistically significant difference of the test-bolus parameters and image quality was proved in patients with occlusive and aneurysmal disease. ConclusionWe proved the technical feasibility and sufficient quality of run-off CTA with low volume of contrast medium and optimized scan time according to aortopopliteal transit time calculated from double-level test bolus.

Comparison of test bolus and bolus tracking techniques for dual-energy CT lung perfusion scan

Objective To compare the test bolus technique with the bolus tracking technique for dual-energy CT pulmonary angiography in patients suspected of pulmonary embolism (PE). Methods A total of 60 patients were randomized into 2 groups:bolus tracking technique group (group B,n=30) and test bolus technique group (group T,n=30).A standard dual-energy CT pulmonary angiography (CTPA) was performed after injection of 60 ml contrast medium followed by 35ml saline chaser at a speed of 4 ml/s.Attenuation profiles of different vascular segments (the subclavian vein,superior vena cava,left atrium,pulmonary trunk,S1 and S10 pulmonary artery) and enhancement value of lung parenchyma were measured to evaluate the timing techniques.The overall image quality Key words: Pulmonary embolism; Tomography,X-ray computed; Angiography; Contrast media

The comparison of bolus tracking and test bolus techniques for computed tomography thoracic angiography in healthy beagles

Computed tomography thoracic angiography studies were performed on five adult beagles using the bolus tracking (BT) technique and the test bolus (TB) technique, which were performed at least two weeks apart. For the BT technique, 2 mL/kg of 300 mgI/mL iodinated contrast agent was injected intravenously. Scans were initiated when the contrast in the aorta reached 150 Hounsfield units (HU). For the TB technique, the dogs received a test dose of 15% of 2 mL/kg of 300 mgI/mL iodinated contrast agent, followed by a series of low dose sequential scans. The full dose of the contrast agent was then administered and the scans were conducted at optimal times as identified from time attenuation curves. Mean attenuation in HU was measured in the aorta (Ao) and right caudal pulmonary artery (rCPA). Additional observations included the study duration, milliAmpere (mA), computed tomography dose index volume (CTDI[vol]) and dose length product (DLP). The attenuation in the Ao (BT = 660 52 HU ± 138 49 HU, TB = 469 82 HU ± 199 52 HU, p = 0.13) and in the rCPA (BT = 606 34 HU ± 143 37 HU, TB = 413 72 HU ± 174.99 HU, p = 0.28) did not differ significantly between the two techniques. The BT technique was conducted in a significantly shorter time period than the TB technique (p = 0.03). The mean mA for the BT technique was significantly lower than the TB technique (p = 0.03), as was the mean CTDI(vol) (p = 0.001). The mean DLP did not differ significantly between the two techniques (p = 0.17). No preference was given to either technique when evaluating the Ao or rCPA but the BT technique was shown to be shorter in duration and resulted in less DLP than the TB technique.

Optimizing contrast medium injection protocol individually with body weight for high-pitch prospective ECG-triggering coronary CT angiography

To individually optimize contrast medium protocol for high-pitch prospective ECG-triggering coronary CT angiography using body weight. Ninety patients undergoing high-pitch coronary CT angiography were randomly assigned to 3 contrast medium injection protocols with bolus tracking technique: Group A, 0.7 ml CM per kg patient weight (ml/kg); Group B, 0.6 ml/kg; Group C, 0.5 ml/kg. Each group had 30 patients. The CT values of superior vena cava (SVC), pulmonary artery (PA), ascending aorta (AA), left atrium (LA), left ventricle (LV), left main artery (LM) and proximal segment of right coronary artery (RCA) were measured. The image quality of coronary artery was evaluated on per-segment basis using a 4-point scale (1-excellent, 4-non-diagnosis). The CT value was not significantly different on AA (p = 0.735), LM (p = 0.764), and proximal segment of RCA (p = 0.991). The CT value was significantly different on SVC, PA, LA and LV (all p < 0.05). The mean image quality score was 1.6 ± 0.1, 1.6 ± 0.1 and 1.6 ± 0.1 (p = 0.217). The volume of CM was 47 ± 8, 44 ± 8 and 36 ± 6 ml for 3 groups (p < 0.001). The effective radiation dose was 0.88 ± 0.04, 0.87 ± 0.06, and 0.85 ± 0.07 mSv for 3 groups. Contrast medium could be reduced to 0.5 ml/kg for high-pitch coronary CT angiography without compromising diagnostic image quality, which associated ~50 % reduction of total contrast volume compared with standard contrast protocol with test bolus technique.

Test Bolus Technique for Detection of Pulmonary Emboli at 64-Slice Multidetector Computed Tomography Angiography

Test Bolus Technique for Detection of Pulmonary Emboli at 64-Slice Multidetector Computed Tomography Angiography

Intravenous Contrast Material Administration at High-pitch Dual-source CT Coronary Angiography: Bolus-tracking Technique with Shortened Time of Respiratory Instruction Versus Test Bolus Technique

Objective To investigate the feasibility of acquiring the similar homogeneous enhancement using bolus-tracking techniques with shortened respiratory time in prospectively electrocardiogram-gated high-pitch spiral acquisition mode (Flash mode) coronary computed tomography angiography (CCTA) compared with test bolus technique. Methods One hundred and eighty-four consecutive patients with mean heart rate ≤65 beats per minute undergoing CCTA were prospectively included in this study. The patients were randomly divided into two groups. Patients in the group A (n=92) instructed to shorten respiratory time received CCTA using bolus-tracking technique with high-pitch spiral acquisition mode (Flash mode), while those in the group B (n=92) underwent CCTA with test bolus technique. The attenuation in the ascending aorta, image noise, contrast-to-noise ratio and radiation doses of the two groups were assessed. Results There were no significant differences in the mean attenuation values in the ascending aorta (483.18±59.07 HU vs. 498.7±83.51 HU, P=0.183), image noise (21.4±4.5 HU vs. 20.9±4.3 HU, P=0.414), contrast-to-noise ratio (12.1±4.2 vs. 13.8±5.1, P=0.31) between the groups A and B. There were no significant differences in the radiation dose of dynamic monitoring scans (0.056±0.026 mSv vs. 0.062±0.018 mSv, P=0.068) and radiation dose of angiography (0.94±0.07 mSv vs. 0.96±0.15 mSv, P=0.926) between the two groups, while 15 mL less contrast material volume was administered in the group A than the group B. Conclusion Bolus-tracking technique with shortened time of respiratory in Flash mode of dual-source CT yields the similar homogeneous enhancement with less contrast material in comparison to the test bolus technique.

Compact-bolus dynamic CT protocol with a test bolus technique in 64-MDCT coronary angiography: comparison of fixed injection rate and duration protocol

We compared the fixed injection rate protocol (P2) with the fixed injection duration protocol (P1) for coronary CT angiography using the test bolus technique. We randomly assigned 100 patients to one of two protocols. In P1, they received 0.7 mL/kg Iohexol-350 in an injection duration of 9 s, and we selected a delay of 3 s after peak enhancement of test bolus scan. In P2, they received 0.7 mL/kg Iohexol-350 at an injection rate of 5 mL/s, and we selected a delay after peak enhancement of test bolus scan using the following formula: TID/2-2 s, where TID is the injection duration of full bolus. We compared attenuation values in the ascending aorta and coronary arteries and patient-to-patient enhancement variability at each segment. At all segments, CT attenuations of P2 were significantly greater than those of P1 (ascending aorta 400 ± 64 vs. 368 ± 60, P = 0.01; left main trunk 399 ± 67 vs. 369 ± 55, P = 0.02; proximal-RCA 393 ± 66 vs. 363 ± 56, P = 0.01). There was no significant difference in patient-to-patient enhancement variability at all segments between the two groups (P > 0.05). P2 yielded superior vessel enhancement and comparable patient-to-patient enhancement variability compared with P1 in thin patients.

Optimization of scan protocol in pulmonary angiography of second generation dual source computed tomography

To explore the scan protocol of second generation dual source computed tomography (CT) for CT pulmonary angiogram (CTPA) in patients with suspected pulmonary embolism and determine the proper volume of contrast medium. A total of 120 patients undergoing CTPA were recruited. All examinations were performed on a second generation dual source CT. The scan delay was determined with the test bolus technique. Four contrast volume protocols were designed, namely groups A, B, C and D respectively (n = 30 each). For CTPA scan of groups A, B, C and D, 35, 40, 45 and 50 ml contrast medium were injected at an injection rate of 4 ml/s, followed by a saline chaser of 55, 50, 45 and 40 ml respectively. Attenuation profiles of different vascular segments (subclavian vein, vena cava, left atrium, pulmonary trunk, S1 artery, S10 artery) were measured to evaluate the timing techniques. The image quality and artifact of iodine map were analyzed by two radiologists for comparisons. The percentage of pulmonary arteries exceeding optimal attenuation (> 200 HU) showed that groups of B, C and D were higher than group A (93% - 100% vs 80% - 90%). The image quality of group A was lower than the others (P < 0.05) while the other groups showed no significant difference. The artifacts of iodine map of group A were much fewer than the others (P < 0.05) and group D was much more than the other groups (P < 0.05). Groups B and C had a score of 4.13 and 3.67 respectively without significant difference (P = 0.091). With the aids of test bolus technique and proper injection protocol (40 ml contrast medium followed by 50 ml saline), the high quality image and low volume of iodine can be realized with second generation dual source CT for CTPA.