Original Research Characterizing Iron Deposition in Multiple Sclerosis Lesions Using Susceptibility Weighted Imaging

Purpose: To investigate whether the variable forms of pu-tative iron deposition seen with susceptibility weighted im-aging (SWI) will lead to a set of multiple sclerosis (MS) lesion characteristics different than that seen in conven-tional MR imaging. Materials and Methods: Twenty-seven clinically definite MS patients underwent brain scans using magnetic reso-nance imaging including: pre- and postcontrast T1-weighted imaging, T2-weighted imaging, FLAIR, and SWI at 1.5 T, 3 T, and 4 T. MS lesions were identified separately in each imaging sequence. Lesions identified in SWI were re-evaluated for their iron content using the SWI filtered phase images. Results: There were a variety of new lesion characteristics identified by SWI, and these were classified into six types. A total of 75 lesions were seen only with conventional imag-ing, 143 only with SWI, and 204 by both. From the iron quantification measurements, a moderate linear correla-tion between signal intensity and iron content (phase) was established. Conclusion: The amount of iron deposition in the brain may serve as a surrogate biomarker for different MS lesion characteristics. SWI showed many lesions missed by con-ventional methods and six different lesion characteristics. SWI was particularly effective at recognizing the presence of iron in MS lesions and in the basal ganglia and pulvinar thalamus. Key Words: multiple sclerosis; iron deposition; suscepti-bility weighted imaging; phase imagin