SU‐E‐I‐24: Determining the Optimal B‐Values to Use in Diffusion Weighted Imaging for Differentiating Benign and Malignant Breast Lesions

Purpose: To investigate and determine the optimal b‐values for Diffusion Weighted Imaging(DWI) for Apparent Diffusion Coefficient(ADC) maps in differentiating normal, benign and malignant breast tissue. Methods: Twenty‐five patients underwent diffusion‐weighted magnetic resonance imaging (DWI‐MRI) and conventional breast MRI with suspicious breast fmdings(BIRADS >4). Breast lesions were defined by pathology. The DWI was acquired with different b‐values ranging from 0,500, 600,750 and 1000s/mm². Apparent Diffusion Coefficient(ADC) maps of breast tissue were constructed using different b‐values, e.g., using either 2 b‐values(0– 1000) or combinations of 3 or more (0,500,1000 or 0,600,750,1000). Quantitative analyses of the ADC maps of glandular, fatty and lesion tissue were obtained. Ratios of lesion to glandular tissue(L/GT) and signal to noise(SNR) were assessed. Paired t‐tests were performed for statistical significance. Results: Eighteen patients had invasive ductal carcinoma and 7 had benign breast lesions. The mean ADC value for malignant lesions using all b values was 1.17±0.16×10‐3mm²/s with a lesion to glandular(L/GT) ratio=0.65. The benign lesions, ADC map value was 1.86±0.03×10‐3mm²/s with L/GT=0.98. There was a significant difference(P<0.05) between benign and malignant lesions ADC map value.The lowest SNR(12±6) was with single b‐values. There was a significant difference(P<0.05) in SNR with multiple b‐values(34±6) compared to single b‐values. The highest SNR was given by using two b values greater than 500. Finally, the background noise for all combinations was surprising stable and ranged between 60±20%. Conclusions: This is the first study to investigate the effect of changing different b values in DWI breast imaging. There were significant differences in the SNR between single and multiple b values. Our data show suggest that the recommended b‐values for DWI in breast are 0, and two that are 500 or greater. Therefore use of at least 3 b‐values in DWI/ADC mapping of breast lesions are needed for better characterization of benign and malignant breast tissue.