Department of Radiology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Japan.
J Vasc Surg. 2012 Mar;55(3):679-87. doi: 10.1016/j.jvs.2011.09.091. Epub 2011 Nov 21.
This study clarified whether unenhanced magnetic resonance imaging (MRI) is an alternative to contrast-enhanced computed tomography (CT) for aortoiliac arterial measurement before endovascular abdominal aortic aneurysm repair (EVAR).
The institutional review board approved this prospective study. Twenty patients being considered for EVAR underwent MRI using a steady-state free-precession sequence in a 1.5-T system and contrast-enhanced CT within 4 weeks of each other. Two independent observers reviewed MRI and CT in random order using vessel analysis software and measured seven diameters, four lengths, and the angle of the aortoiliac arteries. The intermodality, interobserver, and intraobserver agreements were assessed for each measurement by intraclass correlation coefficients (ICCs) and the Altman-Bland method. Additionally, the observers independently recorded the number of bilateral renal arteries, decided EVAR suitability, and selected the main endograft on each modality.
Intermodality ICCs for observers A and B showed ranges of 0.83 to 0.99 and 0.70 to 0.98; interobserver ICCs for MRI and CT showed ranges of 0.73 to 0.99 and 0.65 to 0.99; and intraobserver ICCs for MRI and CT showed ranges of 0.59 to 0.99 and 0.59 to 0.99. In intermodality, interobserver, and intraobserver comparisons, mean differences in diameters were included within the range -1 to +1 mm, excluding three of seven diameters on CT in interobserver comparison and one of seven on CT in intraobserver comparison. Mean differences in lengths were included within the range -5 to +5 mm, excluding one of four lengths in observer B in intermodality comparison and one of four on MRI and CT in interobserver comparison. All mean differences in angles were included within the range -5° to +5°. Both observers detected all 40 bilateral main renal arteries on MRI and CT. Of the 13 accessory renal arteries, observers A and B detected four (31%) and nine (69%), respectively, on MRI; in contrast, both observers detected 11 (85%) on CT. The observers independently determined that the same seven patients were suitable for EVAR on MRI and CT. Of the seven selected main endografts, seven and six diameters and five and six lengths agreed exactly between MRI and CT for observers A and B, respectively.
Although contrast-enhanced CT remains the gold standard for preoperative EVAR planning, unenhanced MRI with steady-state free-precession sequence can be an alternative modality for patients with contraindications for CT, such as renal impairment, because the intermodality agreement for preoperative measurements is as good as interobserver and intraobserver agreement.
本研究旨在明确在血管腔内腹主动脉瘤修复术（EVAR）前，对比增强 CT 检查是否可被非增强磁共振成像（MRI）替代用于主动脉髂动脉测量。
本研究经机构审查委员会批准，纳入 20 例拟行 EVAR 治疗的患者，在 4 周内分别进行稳态自由进动序列 1.5-T 系统 MRI 和对比增强 CT 检查。两位独立观察者以随机顺序使用血管分析软件分别对 MRI 和 CT 进行评估，并测量 7 个直径、4 个长度和主动脉髂动脉角度。采用组内相关系数（ICC）和 Altman-Bland 法评估两种模态之间、观察者之间和观察者内的一致性。此外，观察者还分别记录双侧肾动脉数量，判断 EVAR 适应证，并在每种模态上选择主要血管内移植物。
观察者 A 和 B 的两种模态之间的 ICC 范围分别为 0.83 至 0.99 和 0.70 至 0.98；MRI 和 CT 观察者之间的 ICC 范围分别为 0.73 至 0.99 和 0.65 至 0.99；MRI 和 CT 观察者内的 ICC 范围分别为 0.59 至 0.99 和 0.59 至 0.99。在两种模态之间、观察者之间和观察者内的比较中，直径的平均差异在-1 至+1mm 范围内，观察者之间的 CT 比较中有 7 个直径中的 3 个和观察者内的 CT 比较中有 7 个直径中的 1 个除外。长度的平均差异在-5 至+5mm 范围内，观察者 B 的两种模态之间的 CT 比较中有 4 个长度中的 1 个除外。角度的所有平均差异均在-5°至+5°范围内。两位观察者均在 MRI 和 CT 上检测到所有 40 个双侧主肾动脉。13 个副肾动脉中，观察者 A 和 B 在 MRI 上分别检测到 4 个（31%）和 9 个（69%），而在 CT 上两位观察者均检测到 11 个（85%）。观察者独立判断 7 名患者在 MRI 和 CT 上均适合 EVAR。对于 7 名观察者 A 和 B，在 MRI 和 CT 上，7 个和 6 个直径以及 5 个和 6 个长度完全一致。
虽然对比增强 CT 仍然是 EVAR 术前计划的金标准，但对于存在 CT 禁忌证（如肾功能损害）的患者，使用稳态自由进动序列的非增强 MRI 可以作为替代方法，因为术前测量的两种模态之间的一致性与观察者之间和观察者内的一致性一样好。
