Purpose: This study aims to evaluate the diagnostic efficacy of synthetic diffusion-weighted imaging (sDWI) at various high b-values in distinguishing malignant from benign breast lesions and to compare its performance with that of conventional DWI (cDWI).

Methods: After the exclusion of 22 lesions, 63 women (age range, 24-99 years; mean age, 53.7 ± 15.1 years) with 68 suspicious breast lesions on ultrasound who underwent multiparametric breast magnetic resonance imaging before biopsy between January 2021 and April 2023 were included in this retrospective study. According to the pathological results, lesions were classified as malignant or benign. Volumetric mask images were defined. The lesion signal/normal breast signal ratio [relative signal intensity (rSI)] was measured on different diffusion-weighted images (cDWI at b = 800 and 1500 s/mm²; sDWI at b = 1500-5000 s/mm²), and lesion SI on apparent diffusion coefficient (ADC) 0-800 and ADC0-1500 maps (mADC) was calculated. The diagnostic performances of these parameters were evaluated using a receiver operating characteristic curve analysis and the DeLong test in both the mass and non-mass lesion groups.

Results: A total of 32 (47.06%) benign and 36 (52.94%) malignant lesions were identified. Malignant lesions exhibited significantly higher rSI values on cDWI800, cDWI1500, sDWI1500, sDWI2000, and sDWI3000 (P values: <0.001, <0.001, <0.001, <0.001, <0.001, 0.03) and lower mADC800 and mADC1500 values (P values: 0.01 and 0.03). In mass lesions, synthetic b1500 and conventional b1500 demonstrated diagnostic accuracy comparable with that of routine mADC800 and mADC1500. However, in non-mass lesions, high-b-value DWI maps (b ≥ 2000 s/mm²) significantly outperformed mADC and cDWI in differentiating malignant from benign lesions. The highest diagnostic accuracy in non-mass lesions was observed with rSIC4000 [area under the curve (AUC) = 0.87], whereas in mass lesions, rSIC1500 exhibited the highest diagnostic performance (AUC = 0.79).

Conclusion: The optimal b-value for DWI differs between mass and non-mass breast lesions, emphasizing the need for separate evaluation protocols. Although high-b-value sDWI provides limited added diagnostic value in mass lesions, it significantly improves malignancy detection in non-mass lesions, outperforming cDWI and ADC mapping.

Clinical significance: This study underscores the need for a tailored DWI protocol for optimal breast lesion characterization, particularly for non-mass lesions, where high-b-value synthetic imaging enhances diagnostic accuracy.

Keywords: Breast; breast cancer; high-b-value; magnetic resonance imaging; synthetic diffusion-weighted imaging.

目的： 本研究旨在评估不同高b值的合成扩散加权成像（sDWI）在区分乳腺恶性与良性病变中的诊断效能，并将其性能与常规DWI（cDWI）进行比较。

方法： 排除22个病灶后，本回顾性研究纳入了63名女性（年龄范围：24-99岁；平均年龄53.7 ± 15.1岁），这些女性在2021年1月至2023年4月期间因超声检查发现乳腺可疑病变而在活检前进行了多参数乳腺磁共振成像。根据病理结果，将病灶分为恶性或良性。定义了体积掩模图像，并测量不同扩散加权图像（cDWI在b = 800和1500 s/mm²；sDWI在b = 1500-5000 s/mm²）上的病灶信号/正常乳腺信号比[相对信号强度(rSI)]，并计算了表观扩散系数(ADC) 0-800和ADC0-1500图(mADC)上的病灶信号强度(SI)。使用受试者工作特征曲线分析及DeLong检验评估这些参数在肿块型和非肿块型病灶组中的诊断性能。

结果： 共识别出32（47.06%）个良性病变和36（52.94%）个恶性病变。恶性病变在cDWI800、cDWI1500、sDWI1500、sDWI2000及sDWI3000上的rSI值显著较高(P 值：P 值：0.01 和 0.03)。在肿块型病变中，合成b1500和常规b1500的诊断准确性与传统mADC800和mADC1500相当。然而，在非肿块型病灶中，高b值DWI图（≥2000 s/mm²）显著优于mADC及cDWI在区分恶性与良性病变方面的性能。非肿块型病变中最高的诊断准确性表现为rSIC4000 [曲线下面积(AUC) = 0.87]，而肿块型病灶中，rSIC1500表现出最高的诊断效能 (AUC = 0.79)。

结论： DWI的最优b值在肿块型与非肿块型乳腺病变之间有所不同，强调了需要分别制定评估方案。尽管高b值sDWI在肿块型病灶中的诊断价值有限，但它显著提高了对非肿块型病灶恶性检测的准确性，并优于cDWI和ADC图。

临床意义： 本研究强调了为最佳乳腺病变特征制定定制化DWI协议的重要性，尤其是在非肿块型病灶中，高b值合成成像显著提升了诊断准确性。