1 Department of Radiology, University of Nebraska Medical Center, 981045 Nebraska Medical Center, Omaha, NE 68198-1045.
AJR Am J Roentgenol. 2014 Mar;202(3):648-55. doi: 10.2214/AJR.13.11286.
The objective of our study was to evaluate image quality and overall adequacy of low-dose CT angiography (CTA) with model-based iterative reconstruction (MBIR) in patients who had undergone endovascular aneurysm repair (EVAR) of a thoracic or abdominal aortic aneurysm.
Thirty patients, all of whom had undergone standard-dose CTA performed previously with adaptive statistical iterative reconstruction (ASIR), underwent low-dose CTA for surveillance after EVAR. Two radiologists randomly evaluated both studies, and quality parameters were assessed. The maximal aneurysm diameter was measured, and the images were evaluated to see whether an endoleak was present. The image noise and contrast-to-noise ratio (CNR) were measured. The volume CT dose index and dose-length product were recorded.
The mean image score for low-dose CTA was acceptable to very good in all categories of assessment. There was no significant difference between low-dose CTA and standard-dose CTA in the evaluation of the stent lumen. Subjective assessments of stent configuration, aneurysm outline, aortic branch vessel outline, overall adequacy of vascular imaging, and overall adequacy of solid organ imaging were superior on standard-dose CTA. Interobserver agreement for endoleak detection was higher for low-dose CTA. There was no significant difference in the mean aneurysm diameter between the two readers on low-dose CTA and standard-dose CTA. The effective radiation dose for low-dose CTA was lower than standard-dose CTA during both the arterial (mean, 4.4 vs 16.2 mSv, respectively) and the delayed (2.4 vs 6.7 mSv) phase acquisitions. The measured image noise was lower (14.7 vs 19.3 HU) and CNR was higher (25.6 vs 17.1) on the low-dose CTA studies than on the standard-dose CTA studies.
Low-dose CTA with MBIR enables up to 73% dose reduction as compared with CTA performed with ASIR while maintaining diagnostic adequacy for CTA surveillance of patients who have undergone EVAR of a thoracic or abdominal aortic aneurysm.
本研究旨在评估模型迭代重建（MBIR）在接受胸或腹主动脉瘤血管内修复术（EVAR）的患者中进行低剂量 CT 血管造影（CTA）的图像质量和整体充分性。
30 名患者均曾接受过自适应统计迭代重建（ASIR）的标准剂量 CTA 检查，在 EVAR 后进行低剂量 CTA 随访。两名放射科医生随机评估了这两种检查，并评估了质量参数。测量最大动脉瘤直径，并评估图像是否存在内漏。测量图像噪声和对比噪声比（CNR）。记录容积 CT 剂量指数和剂量长度乘积。
低剂量 CTA 的所有评估类别中，平均图像评分均为可接受至很好。低剂量 CTA 和标准剂量 CTA 在支架管腔评估方面无显著差异。支架构型、动脉瘤轮廓、主动脉分支血管轮廓、血管成像总体充分性和实质器官成像总体充分性的主观评估在标准剂量 CTA 上更好。低剂量 CTA 检测内漏的观察者间一致性更高。两名观察者在低剂量 CTA 和标准剂量 CTA 上测量的平均动脉瘤直径无显著差异。低剂量 CTA 的动脉期（平均分别为 4.4 和 16.2 mSv）和延迟期（2.4 和 6.7 mSv）有效辐射剂量均低于标准剂量 CTA。低剂量 CTA 测量的图像噪声较低（14.7 与 19.3 HU），CNR 较高（25.6 与 17.1）。
与 ASIR 进行的 CTA 相比，MBIR 低剂量 CTA 可将剂量减少 73%，同时保持对接受胸或腹主动脉瘤 EVAR 的患者进行 CTA 随访的诊断充分性。
