Dual-energy CT angiography of the lungs: Comparison of test bolus and bolus tracking techniques for the determination of scan delay

Department of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, D-68167 Mannheim, Germany.
European journal of radiology (Impact Factor: 2.37). 01/2012; 81(1):132-8. DOI: 10.1016/j.ejrad.2010.06.023
Source: PubMed


To prospectively compare test bolus and bolus tracking for the determination of scan delay of pulmonary dual-energy CT angiography in patients with suspected pulmonary embolism.
60 consecutive patients referred for CTA for exclusion of PE were randomized either into a test bolus group or into a bolus tracking group. All exams were performed on a 64-channel dual source CT scanner. A standard single-acquisition dual-energy CTA was performed after injection of 100ml Iomeprol 400 followed by a saline chaser of 4 ml/s. The scan delay was determined using either test bolus (n=30) or bolus tracking (n=30). Test bolus was performed using an additional 20 ml Iomeprol 400 injected with a rate of 4 ml/s during acquisition of a series of dynamic low-dose monitoring scans followed by injection of a saline bolus of 20 ml using the same flow rate. For DECT angiography of the lungs 100ml Iomeprol 400 was injected with an injection rate of 4 ml/s followed by a saline chaser of 20 ml using the same flow rate. Attenuation profiles of different vascular segments (pulmonary arteries, pulmonary parenchyma, aorta, all 4 heart chambers) were measured to evaluate the timing techniques. Overall image quality of dual-energy "perfusion" maps and virtual 120 kV CTA images was evaluated by two radiologists regarding the present of artifacts.
In all patients an adequate and homogeneous contrast enhancement of more than 400 Hounsfield units (HU) was achieved in the different vascular districts. No statistically significant difference between test bolus and bolus tracking was found regarding vessel attenuation or overall image quality.
A homogeneous opacification of the different vascular territories and the pulmonary parenchyma as well as a sufficient image quality can be achieved with either bolus tracking or test bolus techniques.

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    • "The 40-mL group was found to have a lower mean venous attenuation and less residual CM in IJV on the ipsilateral side of injection than those of 50-mL group. Moreover, we attempted to decrease the amount of CM used for the test bolus to 5 mL, based on the faster rate of injection of 6 mL/s, which was significantly lower than those we found in the literature [14,31,15,32,33]. In our study, the average PME of a 5-mL test bolus was 176 HU at the bifurcation of the CCA. "
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    ABSTRACT: Our study aims to evaluate the image quality and feasibility of 128-slice dual-energy CTA (DE-CTA) for supra-aortic arteries using reduced amounts of contrast medium (CM). A prospective study was performed in 54 patients receiving CTA of the head and neck with a 128-slice dual-source CT system. Patients were randomized into two groups with a volume of either 40 mL of CM (Group I) or 50 mL of CM (Group II). Arterial and venous enhancements were recorded for quantitative assessment. Qualitative assessments for images without bone removal (BR) were based on a) the visualization of the circle of Willis and b) streak artifacts due to residual CM in the subclavian or internal jugular veins ipsilateral to injection of CM. Qualitative assessment of dual-energy images using BR was based on the presence of bone remnants and vessel integrity. Quantitative data was compared using the Student t test. The χ(2) test was used for the qualitative measurements of streak artifacts in veins while the Mann-Whitney U test was used for the qualitative measurements of images with BR. Arterial and venous attenuation was significantly higher in Group II (P=0.000). Image quality regarding the circle of Willis was excellent in both groups (3.90±0.30 for Group I and 4.00±0 for Group II) . Imaging of the internal jugular veins was scored higher in Group I (1.87±0.72) compared with Group II (1.48±0.51) (P=0.021). Within Group I using BR, mean scores for bone remnants did not differ significantly (P>0.05) but mean scores of vessel integrity (P<0.05) did. Contrast-enhanced head and neck CTA is feasible using a scan protocol with low amounts of contrast medium (40 mL) on a 128-slice dual-energy CTA. The 40-mL protocol provides satisfactory image quality before and after dual-energy bone-removal post-processing.
    Full-text · Article · Nov 2013 · PLoS ONE
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    • "Thus, the volume varied depending on the patients' blood flow rate, although it was less than 100 mL with shorter injection times in all cases. Neither protocol involved the use of a saline chaser injection, as used in other studies.6,7 "
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    ABSTRACT: Introduction Optimal arterial opacification is crucial in imaging the pulmonary arteries using CT. This poses the challenge of precisely timing data acquisition to coincide with the transit of the contrast bolus through the pulmonary vasculature. The aim of this study was to investigate if a change in CT pulmonary angiogram (CTPA) scanning protocol resulted in improved opacification of the pulmonary arteries. Comparison was made between the Smart Prep Protocol (SPP) and the Timing Bolus Protocol (TBP) for opacification in the pulmonary trunk. Methods A total of 160 CTPA examinations (80 using each protocol) performed between January 2010 and February 2011 were assessed retrospectively. Region of interest (ROI) measurements were taken and the average pixel value, standard deviation, maximum and minimum were recorded. For each of these variables a mean value was then calculated and compared for each protocol. Results Minimum opacification of 200 HU was achieved in 98% of the TBP sample but only 90% the SPP sample (p = 0.0983). The average ROI measurement over the pulmonary trunk for the SPP was 329 ( 21) HU, while for the TBP it was 396 ( 22) HU (p = 0.0017). The TBP also recorded higher maximum (p = 0.0024) and minimum (p = 0.0039) levels of opacification. Conclusion Although results differ from previous studies, this study has found that a TBP resulted in significantly better opacification of the pulmonary trunk than the SPP.
    Full-text · Article · Jun 2013
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    ABSTRACT: CT pulmonary angiography (CTPA) has become the de facto clinical "gold standard" for the diagnosis of acute pulmonary embolism (PE) and has replaced catheter pulmonary angiography and ventilation-perfusion scintigraphy as the first-line imaging method. The factors underlying this algorithmic change are rooted in the high-sensitivity and specificity, cost-effectiveness, and 24-hour availability of CTPA. In addition, CTPA is superior to other imaging methods in its ability to diagnose and exclude, in a single examination, a variety of diseases that mimic the symptoms of PE. This article reviews the current role of CTPA in the diagnosis of acute PE as well as more recent developments, such as the use of CT parameters of right ventricular dysfunction for patient prognostication and the assessment of lung perfusion with CT.
    No preview · Article · Oct 2010 · Journal of cardiovascular computed tomography
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