Quantitative magnetization transfer imaging derived macromolecular‐to‐free pool‐size ratio (PSR) and relaxation rate of the free water pool (R1f) values were extracted and compared between PRLs and nPRLs, NAWM surrounding PRLs and nPRLs, and whole brain WM lesions and NAWM of PRL+ and PRL− people with MS (pwMS). The gene discussed is PRL; the disease is myeloid sarcoma.