Comparison of intensity normalization methods in prostate, brain, and breast cancer multi-parametric magnetic resonance imaging

Intensity variation in multi-parametric magnetic resonance imaging (MP-MRI) poses challenges for MRI analyses. Previous studies have employed several normalization methods, but a lack of consensus on which results in the most comparable images exists. This study analyzed MP-MRI data from patients with prostate, brain, or breast cancer to evaluate common intensity normalization methods to best harmonize intensities across sites, vendors, and magnetic field strengths. Additionally, we calculated radiomic features after normalization to assess downstream effects. In prostate cancer, normalization methods were tested on T2-weighted imaging (T2WI), including a subset scanned with and without an endorectal coil (ERC). In glioblastoma (GBM) patients, methods were evaluated on various MRI sequences. For breast cancer, methods were tested on T1-weighted nonfat-suppressed images. All methods were compared using a two one-sided test (TOST) to test for equivalence of mean and standard deviation of intensity distributions. Across every comparison, the Z-score of intensity within a mask of the organ consistently provided an equivalent distribution (all p < 0.001). Likewise, Z-score normalization provided the highest percentage of radiomic features that were statistically. Our results suggest that normalizing intensity using the Z-score of MRI intensity within an organ mask produces the most comparable intensities across multiple settings.