80kV低管电压扫描对脑CT血管成像图像质量及辐射剂量的影响

Effect of 80 kV Low Tube Voltage on Image Quality and Radiation Dose at Cerebral Computed Tomography Angiography

目的对比80kV及120kV管电压对脑CT血管成像(CTA)图像质量及辐射剂量的影响,探讨低管电压脑CTA的可行性。资料与方法100例行脑CTA检查的患者随机分为80kV组和120kV组,每组50例。测量两组患者脑动脉(包括基底动脉、颈内动脉颅内段、大脑前动脉、大脑中动脉、大脑后动脉)CT值,计算各部位的图像对比噪声比(CNR)及信噪比(SNR),并对图像主观质量(包括脑动脉重建图像质量、血管边缘形态、微小分支血管显示程度、整体图像质量)及诊断信心进行评价。结果 80kV组患者CT剂量指数容积(CTDIvol)、剂量长度乘积(DLP)、有效剂量(ED)较120kV组分别降低63.97%、64.54%、64.65%。80kV组患者脑血管CT值及其与脑实质对比值较120kV组显著增高(P<0.001)。80kV组患者图像噪声水平较120kV组显著增高(P<0.001),但两组患者血管CNR及SNR差异均无统计学意义(P>0.05)。与120kV组相比,80kV组患者血管边缘锐利程度降低,微小分支血管显示增多,但两组脑动脉重建图像质量、图像整体质量及对图像的诊断信心差异无统计学意义(P>0.05)。结论 80kV低管电压脑CTA不仅可以显著增加血管强化值及其与周边组织的对比,而且图像整体质量及诊断信心不受影响,并能大幅度地降低辐射剂量。

Purpose To investigate the effect of 80 kV and 120 kV tube voltage on image quality and radiation dose of cerebral CT angiography （CTA）, and to explore the possibility of low tube voltage in cerebral CTA. Materials and Methods A total of 100 patients underwent cerebral CTA were selected, and divided into 80 kV group （n-50） and 120 kV group （n=50）. CT values were evaluated for the following anatomic structures： basilar artery, internal carotid artery, anterior cerebral artery, middle cerebral artery and posterior cerebral artery. The contrast-to-noise ratio （CNR）, signal-to-noise ratio （SNR） were calculated, then the subjective assessment on image quality （including reconstructed images, vascular margin, presentation of small vessels and the whole image quality） and diagnostic confidence were evaluated. Results Compared with 120 kV group, the CT dose index volume （CTDIvo0, dose length product （DLP） and effective dose （ED） of 80 kV group reduced 63.97%, 64.54% and 64.65%, respectively. The mean CT values of blood vessels in 80 kV group were substantially higher than those in 120 kV group （P〈0.001）. Although the noise level was markedly higher in 80 kV group （P〈0.001）, the CNR and SNR showed no difference between the two groups （P〉0.05）. With 80 kV low tube voltage, the vascular margin showed rougher and the presentations of small vessels were obviously more than those with 120 kV tube voltage. However, the subjective scorings of the reconstructed images qualities, the whole image quality and diagnostic confidence showed no statistical difference between the two groups （P〉0.05）. Conclusion With 80 kV low tube voltage of cerebral CTA, the radiation dose can be markedly reduced without degradation of image quality and diagnostic confidence.