Sato Toshiyuki, Isoda Hiroyoshi, Fujimoto Koji, Furuta Akihiro, Fujimoto Masakazu, Ito Katsuhiro, Kobayashi Takashi, Nakamoto Yuji
Department of Diagnostic Imaging and Nuclear Medicine, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Preemptive Medicine and Lifestyle Disease Research Center, Kyoto University Hospital, Kyoto, Japan.
J Magn Reson Imaging. 2021 Dec;54(6):1979-1988. doi: 10.1002/jmri.27771. Epub 2021 Jun 4.
Diffusion-weighted imaging (DWI) is an important method for clinically significant prostate cancer (csPCa) diagnosis; however, the Prostate Imaging-Reporting and Data System (PI-RADS) requires the subjective assessment of "markedly hypointense or not" on apparent diffusion coefficient (ADC) map. We hypothesize that weighted diffusion subtraction (WDS) images, created by weighted subtraction of high and low b-value DWIs, might better show areas of ADC values below a set threshold, thus decreasing the subjectivity of the assessment.
To evaluate the diagnostic ability of WDS for csPCa by comparing scores based on WDS images (DWI/WDS) with those based on PI-RADS DWI (DWI/ADC).
Retrospective.
Eighty-six PCa patients.
FIELD STRENGTH/SEQUENCES: 3.0 T; DWI.
Four readers assessed the probability of csPCa in lesions (overall, in the peripheral zone [PZ] and transitional zone [TZ]) using 5-point DWI/ADC and DWI/WDS scores. Prostatectomy specimens were the reference standard. ADC values and contrast between csPCa and normal prostate tissue on ADC maps and WDS images were calculated with reference to the pathological map.
Diagnostic ability was evaluated by Jackknife alternative free-response receiver-operating characteristic curve. Figure of merit (FOM), sensitivity, and positive predictive value (PPV) between the DWI/ADC and DWI/WDS scores were compared using paired t-test. Inter-reader agreement was analyzed using κ statistics, and the significance probability was calculated using the Z statistic. Wilcoxon signed-rank test was used to compare contrast between csPCa and normal prostate tissue on ADC maps and WDS images. A P value <0.05 was considered statistically significant.
FOM and sensitivity of the DWI/WDS scores were significantly better than those of the DWI/ADC scores overall, in the PZ and TZ (FOM: overall, 0.715 vs. 0.783; PZ, 0.756 vs. 0.815; TZ, 0.653 vs. 0.738. Sensitivity: overall, 0.512 vs. 0.607; PZ, 0.485 vs. 0.573; TZ, 0.636 vs. 0.761). For PPV, a statistically significant difference was observed overall (0.727 vs. 0.777). The κ value of DWI/WDS score was significantly higher than that of DWI/ADC score overall and in the PZ (overall, 0.614 vs. 0.792; PZ, 0.609 vs. 0.797). Contrast was significantly higher overall in the PZ and TZ in WDS images (median, 1.26, 1.19, and 1.61) than in ADC maps (0.46, 0.47, and 0.41).
WDS images performed better than ADC maps in the diagnosis of csPCa and in inter-reader agreement of the diagnosis.
4 Technical Efficacy Stage: 2.
扩散加权成像（DWI）是临床上诊断有意义前列腺癌（csPCa）的重要方法；然而，前列腺影像报告和数据系统（PI-RADS）要求对表观扩散系数（ADC）图进行“是否明显低信号”的主观评估。我们假设，通过对高、低b值DWI进行加权相减创建的加权扩散减法（WDS）图像，可能能更好地显示低于设定阈值的ADC值区域，从而降低评估的主观性。
通过比较基于WDS图像（DWI/WDS）的评分与基于PI-RADS DWI（DWI/ADC）的评分，评估WDS对csPCa的诊断能力。
回顾性研究。
86例前列腺癌患者。
场强/序列：3.0 T；DWI。
4名阅片者使用5分制的DWI/ADC和DWI/WDS评分评估病变（总体、外周带[PZ]和移行带[TZ]）中csPCa的可能性。前列腺切除标本为参考标准。参照病理图计算ADC值以及csPCa与正常前列腺组织在ADC图和WDS图像上的对比度。
通过留一法替代自由反应型受试者操作特征曲线评估诊断能力。使用配对t检验比较DWI/ADC和DWI/WDS评分之间的品质因数（FOM）、敏感性和阳性预测值（PPV）。使用κ统计分析阅片者间的一致性，并使用Z统计计算显著性概率。采用Wilcoxon符号秩检验比较csPCa与正常前列腺组织在ADC图和WDS图像上的对比度。P值<0.05被认为具有统计学意义。
总体、PZ和TZ中，DWI/WDS评分的FOM和敏感性显著优于DWI/ADC评分（FOM：总体，0.715对0.783；PZ，0.756对0.815；TZ，0.653对0.738。敏感性：总体，0.512对0.607；PZ，0.485对0.573；TZ，0.636对0.761）。对于PPV，总体上观察到统计学显著差异（0.727对0.777）。DWI/WDS评分的κ值总体上和在PZ中显著高于DWI/ADC评分（总体，０.614对0.792；PZ，0.609对0.797）。WDS图像中PZ和TZ的总体对比度（中位数分别为1.26、1.19和1.61）显著高于ADC图（0.46、0.47和0.41）。
在csPCa诊断及阅片者间诊断一致性方面，WDS图像比ADC图表现更好。
4 技术效能阶段：2。
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