OBJECTIVE To determine whether a 3D magnetic resonance imaging (MRI) sequence with postprocessing applied to simulate computed tomography (CT) ("pseudo-CT") images can be used instead of CT to measure acetabular version and alpha angles and to plan for surgery in patients with femoroacetabular impingement (FAI). MATERIALS AND METHODS Four readers retrospectively measured acetabular version and alpha angles on MRI and CT images of 40 hips from 20 consecutive patients (9 female patients, 11 male patients; mean age, 26.0 ± 6.5 years) with FAI. 3D models created from MRI and CT images were assessed by 2 orthopedic surgeons to determine the need for femoroplasty and/or acetabuloplasty. Interchangeability of MRI with CT was tested by comparing agreement between 2 readers using CT (intramodality) with agreement between 1 reader using CT and 1 using MRI (intermodality). RESULTS Intramodality and intermodality agreement values were nearly identical for acetabular version and alpha angle measurements and for surgical planning. Increases in inter-reader disagreement for acetabular version angle, alpha angle, and surgical planning when MRI was substituted for CT were - 2.1% (95% confidence interval [CI], - 7.7 to + 3.5%; p = 0.459), - 0.6% (95% CI, - 8.6 to + 7.3%; p = 0.878), and 0% (95% CI, - 15.1 to + 15.1%; p = 1.0), respectively, when an agreement criterion ≤ 5° was used for angle measurements. CONCLUSION Pseudo-CT MRI was interchangeable with CT for measuring acetabular version and highly favorable for interchangeability for measuring alpha angle and for surgical planning, suggesting that MRI could replace CT in assessing patients with FAI.

中文翻译：

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CT和3D“伪CT” MRI的互换性可用于股骨髋臼撞击患者的术前计划。

目的要确定是否可以使用经过后处理的3D磁共振成像（MRI）序列来模拟计算机断层扫描（CT）（“伪CT”）图像，而不是使用CT来测量髋臼型和α角，并计划进行手术股骨髋臼撞击（FAI）的患者。材料与方法四位读者回顾性分析了连续20例FAI患者（共9例女性，11例男性；平均年龄26.0±6.5岁）的40例髋关节的MRI和CT图像的髋臼形态和α角。由两名骨科医生评估了从MRI和CT图像创建的3D模型，以确定是否需要进行股骨成形术和/或髋臼成形术。通过比较2位使用CT的阅读器之间的一致性（内模态）与1位使用CT的阅读器与1位使用MRI的互感性（模态），来测试MRI与CT的互换性。结果对于髋臼型和α角测量以及手术计划，模内和模间一致性值几乎相同。当使用MRI代替CT时，髋臼版本角度，α角和手术计划在阅读者之间的分歧增加--2.1％（95％置信区间[CI]，-7.7至+ 3.5％； p = 0.459），-0.6当达成一致标准≤5°时，分别为％（95％CI，-8.6至+ 7.3％; p = 0.878）和0％（95％CI，-15.1至+ 15.1％; p = 1.0）角度测量。