高b值MR扩散加权成像在乳腺良恶性病变诊断中的应用价值

Application of high b-value MR diffusion weighted imaging for malignant and benign breast lesions

目的 评价高b值MR DWI及ADC值在乳腺良恶性病变诊断中的应用价值.方法 165例患者在行乳腺MR动态增强扫描前行不同b值（分别为500、1500 s/mm2）的DWI扫描,对171个怀疑或高度怀疑恶性病变者行回顾性分析.以正常乳腺组织为参考基准,选择增强图像中异常强化的高信号病变,同时在高b值（b= 1500 s/mm2）DWI中视觉判定是高信号的病变定义为恶性病变阳性结果,否则为良性病变阴性结果.对其中111个DWI视觉判定阳性结果的病变计算ADC值.依据全部病变穿刺活检病理诊断结果,应用Fisher精确检验和Wilcoxon秩和检验对比分析高b值DWI视觉评估中恶性和良性病变的阳性和阴性病灶数,以ADC值=1.13×10^-3 mm^2/s作为临界值,计算诊断的特异度和敏感度.结果 乳腺病变穿刺活检病理证实的171个乳腺病变中,91个恶性病变,80个良性病变.高b值DWI视觉评估,139个阳性结果中,恶性病变83个,良性病变56个；32个阴性结果中,良性病变24个,恶性病变8个（非肿块性导管原位癌）,差异有统计学意义（P＜0.01）.所有浸润性癌和肿块样导管原位癌（DCIS）在DWI视觉判定中为阳性,8例非肿块性DCIS判定为假阴性,总体的敏感度为91.2％ （83/91）,特异性为30.0％ （24/80）.110个肿块样病变和1个局灶性病变DWI视觉评估阳性结果的病变中,63个恶性病变平均ADC值为（0.73±0.24）×10^-3 mm^2/s,48个良性病变平均ADC值为（1.19±0.42）×10^-3mm^2/s,差异有统计学意义（Z=5.818,P＜0.01）.以ADC值=1.13×10^-3mm^2/s作为临界值时,61个恶性病变为阳性结果,2个黏液癌为假阴性结果；27个良性病变为阴性结果,21个良性病变为假阳性,诊断敏感度是96.8％（61/63）,特异度为56.2％ （27/48）.结论 高b值DWI及ADC值对乳腺良恶性病变的鉴别诊断有一定的作用,但在诊断非肿块性乳腺病变时仍需慎重.

Objective To evaluate the application of high b-value diffusion weighted imaging （DWI） and ADC values for malignant and benign breast lesions.Methods There were 165 patients with 171 suspicious malignant breast lesions received low and high b-value （ 500 and 1500 s/mm2 ） DWI scan before dynamic contrast-enhanced MRI （DEC-MRI）.Using normal breast as the reference base,the signal intensity and ADC values of the 171 lesions on high-b-value （ b = 1500 s/mm2 ） DWI were retrospectively analyzed If a lesion showed abnormal enhancement on DCE-MRI and high signal intensity on high-b-value （b = 1500 s/mm2 ） DWI,that lesion was defined as positive result on behalf of malignant lesion; the otherwise was defined as negative result on behalf of benign lesion.ADC values were calculated for the 111 lesions with positive results on DWI.And all lesions received a biopsy after MR scan.References to the histopatholngical results,the amounts of positive and negative results on high-b value DWI were recorded.Using 1.13 × 10 -3mm2/s as the cutoff value,the sensitivity and specificity of ADC value for the diagnosis of malignant breast lesion were calculated.Fisher exact tests and Wilcoxon rank sum tests were used for statistical analyses.Results There are 91 malignant and 80 benign lesions the 171 lesions confirmed by histopathology.On high-b value DWI,139 lesions were visually positive results,including 83 malignant and 56 benign lesions.Other 32 lesions were visually negative results,including 24 benign lesions and 8 malignant lesions （non-mass ductal carcinoma in situ）.There are statistically significant difference between malignant and benign lesions （ P 〈 0.01 ）.All invasive carcinoma and mass-forming DCIS were visually positive results,whereas eight non-mass DCIs lesions were visually negative results,the overall sensitivity and specificity were 91.2% （83/91）and 30.0% （24/80）,respectively.In the 111 lesions with DWI positive result （ 110 mass lesions and one focal lesion）,the mean ADC value of the 63 malignant lesions was （0.73 ±0.24） × 10-3 mm2/s,whereas the mean ADC value of the 48 benign lesions was（ 1.19 ±0.42） ×10-3 mm2/s.There was statistically significant difference between benign and malignant lesions （Z =5.818,P 〈0.01 ）.When ADC value of 1.13 × 10-3 mm2/s was chosen as the cutoff value,61 malignant lesions were true positive results,2 mucinous carcinoma were false-negative results,27 benign lesions were true negative results,21 benign lesions were false-positive results,the sensitivity and specificity was 96.8%（61/63） and 56.2% （27/48）,respectively.Conclusions High b-value DWI and ADC values were useful for distinguishing of malignant and benign breast lesions,but it should be cautious when it was used for the diagnosis of non-mass breast lesions.