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KMID : 0880420210220060922
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Korean Journal of Radiology
2021 Volume.22 No. 6 p.922 ~ p.930
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Why Is a b-value Range of 1500?2000 s/mm2 Optimal for Evaluating Prostatic Index Lesions on Synthetic Diffusion-Weighted Imaging?
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Cha So-Yeon
Kim Eun-Ju
Park Sung-Yoon
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Abstract
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Objective: It is uncertain why a b-value range of 1500?2000 s/mm2 is optimal. This study was aimed at qualitatively and quantitatively analyzing the optimal b-value range of synthetic diffusion-weighted imaging (sDWI) for evaluating prostatic index lesions.
Materials and Methods: This retrospective study included 92 patients who underwent DWI and targeted biopsy for magnetic resonance imaging (MRI)-suggested index lesions. We generated sDWI at a b-value range of 1000?3000 s/mm2 using dedicated software and true DWI data at b-values of 0, 100, and 1000 s/mm2. We hypothesized that lesion conspicuity would be best when the background (i.e., MRI-suggested benign prostatic [bP] and periprostatic [pP] regions) signal intensity (SI) is suppressed and becomes homogeneous. To prove this hypothesis, we performed both qualitative and quantitative analyses. For qualitative analysis, two independent readers analyzed the b-value showing the best visual conspicuity of an MRI-suggested index lesion. For quantitative analysis, the readers assessed the b-value showing the same bP and pP region SI. The 95% confidence interval (CI) or interquartile range of qualitatively and quantitatively selected optimal b-values was assessed, and the mean difference between qualitatively and quantitatively selected b-values was investigated.
Results: The 95% CIs of optimal b-values from qualitative and quantitative analyses were 1761?1805 s/mm2 and 1640?1771 s/mm2 (median, 1790 s/mm2 vs. 1705 s/mm2; p = 0.003) for reader 1, and 1835?1895 s/mm2 and 1705?1841 s/mm2 (median, 1872 s/mm2 vs. 1763 s/mm2; p = 0.022) for reader 2, respectively. Interquartile ranges of qualitatively and quantitatively selected optimal b-values were 1735?1873 s/mm2 and 1573?1867 s/mm2 for reader 1, and 1775?1945 s/mm2 and 1591?1955 s/mm2 for reader 2, respectively. Bland?Altman plots consistently demonstrated a mean difference of less than 100 s/mm2 between qualitatively and quantitatively selected optimal b-values.
Conclusion: b-value range showing a homogeneous background signal may be optimal for evaluating prostatic index lesions on sDWI. Our qualitative and quantitative data consistently recommend b-values of 1500?2000 s/mm2.
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KEYWORD
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Prostate, Magnetic resonance imaging, Diffusion, Neoplasm
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