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

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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. Key words: Breast neoplasms; Magnetic resonance imaging; Comparative study