Characteristics and pitfalls of contrast-enhanced, T1-weighted magnetization transfer images of the brain

Rationale and Objectives. This study was undertaken to clarify the differen ce in signal pattern on contrast material-enhanced T1-weighted magnetic res onance (MR) magnetization transfer (MT) images between enhancing and nonenh ancing lesions in various intracranial diseases and to determine the necess ity of nonenhanced MT images for evaluating lesional contrast enhancement. Materials and Methods. MR images of 116 patients who underwent nonenhanced T1-weighted imaging, nonenhanced MT imaging, and contrast-enhanced MT imagi ng were reviewed. The increase in signal intensity of lesions relative Co n ormal brain was compared between nonenhanced T1-weighted images and contras t-enhanced MT images. Signal intensity of lesions was compared with that of the striate nucleus and white matter on contrast-enhanced MT images. True enhancement was determined by comparison with nonenhanced MT images. Results, In all, 143 lesions, including 86 enhancing and 57 nonenhancing le sions, were identified among 63 patients. Almost all (99%) of the enhancing lesions were hyperintense to striate nucleus on contrast-enhanced MT image s, and most (>87%) showed moderate to marked signal intensity increase from nonenhanced T1-weighted images to contrast-enhanced MT images. Most (>95%) of the nonenhancing lesions showed mild or no increase in relative signal intensity, and most (75%) were iso- or hypointense to striate nucleus on co ntrast-enhanced MT images. A few nonenhancing lesions (4%-6%), however. sho wed increase in signal intensity that was indistinguishable from true enhan cement without comparison to nonenhanced MT images. Conclusion. Nonehanced MT images should be obtained to assess pathologic en hancement accurately.