Deciphering ADC disparities in breast MRI: Implications for left-right asymmetry and standardization.

Purpose

To systematically evaluate the impact of MRI software updates on apparent diffusion coefficient (ADC) values, assess potential left-right asymmetry in bilateral breast ADC values, and explore standardization techniques to enhance diagnostic reliability in lesion classification.

Methods

A total of 420 patients (mean age, 54.2 ± 14.2 years) who underwent 3 T breast MRI between 2021 and 2025 were retrospectively analyzed. The ADC values in fibroglandular tissue (FGT) and pectoralis major muscle (PMM) were compared before and after a software update using an unpaired t-test. Left-right asymmetries were assessed using paired and unpaired t-tests. Differences in lesion ADC values between malignancies were analyzed. The diagnostic performance of three region of interest (ROI) methods-whole-lesion mean (WL-mean), small-ROI mean (SR-mean), and small-ROI minimum (SR-min)-was evaluated using receiver operating characteristic analysis. The effect of standardization using ratios or differences relative to FGT and PMM on diagnostic accuracy was also examined.

Results

The ADC values were affected by the software update, and notable left-right asymmetries were observed in both FGT and PMM. Malignancies had significantly lower ADC values than benign lesions. Among the ROI methods, SR-min yielded the highest diagnostic accuracy, although diagnostic performance was lower in non-mass lesions than in mass lesions across the ROI methods. Standardization using ratios or differences relative to FGT and PMM did not improve diagnostic performance.

Conclusions

ADC measurements are sensitive to technical variables and exhibit unexpected laterality effects, thereby complicating standardization. While general thresholds may guide interpretation, establishing universally standardized ADC values remains challenging.