256-Slice Craniocervical Multidetector Computed Tomography Angiography With40Milliliters Of Contrast Volume

Background and Purpose:With the advent of modern256-slice multidectector computed tomography(MDCT) scanners, the scan acquisition time has greatly reduced and the image qualityhas further improved owing to its high spatial as well as temporal resolution.Craniocervical computed tomography angiography (CTA) has become an importanttool for the assessment of the extracranial and intracranial vessels. However, artifactsare commonplace in CTA, are distracting and may compromise accurate diagnosis.Perivenous artifacts are well reported concerned on CTA. Hence, the goals of thisprospective study were to study the attenuation values of craniocervical vessels andthe perivenous artifacts at the subclavian vein using different volumes of contrastmedia (40ml versus50ml) with256-slice craniocervical MDCT angiography.Material and Methods:This prospective study was approved by institutional review board (IRB) and theinformed consent was obtained from all the patients. Sixty six patients were randomlyassigned into two groups (Group A and B), each comprising33patients. All patientsunderwent craniocervical CTA examination. Group A (21men,12women; mean age,56.87±11.53; age range,29–73years) received the department’s standard protocolof50ml intravenous contrast volume, whereas Group B (19men,14women; meanage,56.94±11.51years; age range,37–87years) received40ml of contrast volume.In both groups, injection rate was5ml/s, followed by a40ml flush of saline. Allstudies were performed with same scanning parameters with256-slice CT scannerusing a real time-bolus tracking technique. Quantitatively, mean attenuation values forboth groups were measured in arteries and veins of the craniocervical region. In thearterial system, attenuation values were measured at seven points in the aorto-carotidartery, and at three points in the vertebro-basilar artery. Likewise, attenuation valuesof veins were also measured at four points. Qualitatively, two radiologistsindependently evaluated the axial source and maximum intensity projection (MIP) images for the occurrence of artifacts at the subclavian vein using a four-point scale.Attenuation profiles were calculated using unpaired student’s t-test, and the Mann–Whitney U test was used for qualitative analysis. Probability values less than0.05were considered statistically significant.Results:Although there were no statistically significant differences in mean arterialattenuation profiles (aorto-carotid artery (p=0.87) and vertebra-basilar artery (p=0.72))in Group A versus Group B, mean venous attenuation values were lower in Group Bthan in Group A (110±19.61HU vs.188.27±57.4HU; p<0.001). When comparedwith Group A qualitatively, the perivenous artifacts in the subclavian veins wereevaluated as less prominent (p<0.001) in Group B, whereas there was no significantdifference during the qualitative assessment of the arterial images.Conclusion:Use of40ml contrast medium on cervical CTA can reduce venous attenuationprofiles and decrease perivenous artifacts in the subclavian veins when compared with50ml.