Møller Jakob Møllenbach, Østergaard Mikkel, Thomsen Henrik S, Hangaard Stine, Sørensen Inge J, Madsen Ole Rintek, Pedersen Susanne J
Department of Radiology, Herlev-Gentofte Hospital, Herlev, Denmark.
Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet, Glostrup, Denmark.
BJR Open. 2020 Dec 21;2(1):20200004. doi: 10.1259/bjro.20200004. eCollection 2020.
The apparent diffusion coefficient (ADC) may be used as a biomarker for diagnosis and/or monitoring treatment response in patients with axial spondyloarthritis (axSpA), but this requires reliable ADC measurements. This study assessed test-retest repeatability and reproducibility of ADC measurements using four different region of interest (ROI) settings.
In this prospective study, the sacroiliac joints (SIJs) of 25 patients with axSpA and 24 age- and sex-matched healthy volunteers were imaged twice at a mean interval of 6.8 days in a 1.5 T scanner using, multishot echoplanar diffusion-weighted sequences. ADCs at four ROI settings were assessed: 5 mm and 10 mm anatomic band-shaped, 15 mm linear, and 40 mm circular.
Intraclass correlation coefficient (ICC) assessments showed that the interstudy repeatability was good for median ADC (ADC) and 95th-percentile ADC (ADC) measurements in patients with axSpA (0.77-0.83 and 0.75-0.83, respectively), but poor-to-moderate in healthy subjects (0.27-0.55 and 0.13-0.37, respectively). For all ROI settings, intrareader reproducibility was excellent for ADC-measurements (ICC:0.85-0.99) and moderate-to-excellent for ADC measurements (ICC:0.68-0.96). The 5 mm ROI had the least estimated bias and highest level of agreement on Bland-Altman plots. The interreader reproducibility was moderate (ICC:0.71). The 15 mm linear ROI produced significantly greater ADC and ADC measurements than all other ROI settings ( < 0.01-0.02), except for the circular ROI ADC measurements.
ROI settings influence ADC measurements. Interstudy repeatability of SIJ ADC measurements is independent of ROI settings. However, the 5 mm ROI showed the least bias and random error and seems preferable.
ADC measurements are affected by ROI settings, and this should be taken into account when assessing ADC maps.
表观扩散系数（ADC）可作为轴向性脊柱关节炎（axSpA）患者诊断和/或监测治疗反应的生物标志物，但这需要可靠的ADC测量值。本研究使用四种不同的感兴趣区域（ROI）设置评估了ADC测量的重测重复性和再现性。
在这项前瞻性研究中，25例axSpA患者和24例年龄及性别匹配的健康志愿者的骶髂关节（SIJ）在1.5T扫描仪中使用多次激发平面回波扩散加权序列进行成像，平均间隔6.8天成像两次。评估了四种ROI设置下的ADC值：5mm和10mm解剖带状、15mm线性和40mm圆形。
组内相关系数（ICC）评估显示，axSpA患者中，研究间重复性对于中位数ADC（ADC）和第95百分位数ADC（ADC）测量良好（分别为0.77 - 0.83和0.75 - 0.83），但在健康受试者中为差至中等（分别为0.27 - 0.55和0.13 - 0.37）。对于所有ROI设置，同一读者的再现性对于ADC测量极佳（ICC：0.85 - 0.99），对于ADC测量为中等至极佳（ICC：0.68 - 0.96）。5mm ROI在Bland - Altman图上估计偏差最小且一致性水平最高。不同读者间的再现性为中等（ICC：0.71）。15mm线性ROI产生的ADC和ADC测量值显著高于所有其他ROI设置（<0.01 - 0.02），圆形ROI的ADC测量值除外。
ROI设置会影响ADC测量。SIJ的ADC测量的研究间重复性与ROI设置无关。然而，5mm ROI显示出最小的偏差和随机误差，似乎更可取。
ADC测量受ROI设置影响，在评估ADC图时应予以考虑。
