Department of Diagnostic Radiology, Singapore General Hospital, Outram Road, Singapore, 169608, Singapore.
Duke-NUS Medical School, Singapore, Singapore.
Neuroradiology. 2021 Oct;63(10):1659-1667. doi: 10.1007/s00234-021-02658-2. Epub 2021 Feb 5.
The callosal angle (CA) is a useful biomarker in the diagnosis and management of idiopathic normal pressure hydrocephalus (NPH). Used incorrectly, CA measurements are variable, affecting its reliability as a clinical tool. Our objectives are to evaluate (i) reproducibility of established CA measurements between trained raters and (ii) impact of minor angular mal-rotations of the true coronal plane on CA measurements.
CAs were measured by two independent raters on three-dimensional isovolumetric T1-weighted brain MRI of NPH patients and healthy controls using the established true coronal plane reformatted orthogonal to the plane containing the anterior-posterior commissural (AC-PC) line at the level of the posterior commissure. CA changes were subsequently evaluated when the coronal plane was mal-rotated by ± 5° and ± 10° in anterior-posterior and clockwise-anticlockwise directions. Inter-rater reliability of CA measurements was assessed using the intraclass correlation coefficient (ICC).
On the true coronal plane, inter-rater ICC was excellent (0.973) for NPH patients and good (0.875) for controls. On mal-rotated coronal plane setups, ICC for CA was worse in controls (0.484-0.886) than NPH (0.879-0.981) groups and in clockwise-anticlockwise (0.484-0.956) than anterior-posterior (0.503-0.981) mal-rotations. CA changes secondary to mal-rotations from the true coronal plane were significant in NPH patients (P < 0.0001 to 0.0378) but not in controls (P > 0.1).
This is the first demonstration of how small angular mal-rotations of the coronal plane used for CA measurement affect its value and inter-rater reliability, highlighting the importance of a standardized protocol when measuring the CA in NPH workup.
胼胝体角（CA）是诊断和治疗特发性正常压力脑积水（NPH）的有用生物标志物。如果使用不当，CA 测量值会发生变化，从而影响其作为临床工具的可靠性。我们的目标是评估（i）经过培训的评分者之间已建立的 CA 测量值的可重复性，以及（ii）真实冠状面的轻微角度偏转而对 CA 测量值的影响。
使用与包含后联合的前后联合（AC-PC）线在后联合水平的平面正交的已建立的真实冠状面，由两名独立的评分者在 NPH 患者和健康对照者的三维等容 T1 加权脑 MRI 上测量 CA。随后，当冠状面在前-后和顺时针-逆时针方向偏转而旋转±5°和±10°时，评估 CA 的变化。CA 测量的组内相关系数（ICC）评估了评分者之间的可靠性。
在真实的冠状面上，NPH 患者的评分者间 ICC 为极好（0.973），而对照组的 ICC 为良好（0.875）。在偏置冠状面设置中，CA 的 ICC 在对照组中比 NPH 组差（0.484-0.981），在顺时针-逆时针方向（0.484-0.956）比前-后方向（0.503-0.981）更差。与从真实冠状面发生的偏置相关的 CA 变化在 NPH 患者中具有显著意义（P<0.0001 至 0.0378），但在对照组中则无意义（P>0.1）。
这是首次证明用于 CA 测量的冠状面的小角度偏转而如何影响其价值和评分者间的可靠性，突出了在 NPH 检查中测量 CA 时标准化方案的重要性。
