Magnetization Transfer on T2-weighted Image: Magnetization Transfer Ratios in Normal Brain and CerebralLesions

ABSTRACT

PURPOSE: To evaluate the magnetization transfer ratio(MTR) of various normal structures and pathologiclesions, as seen on magnetization transfer T2-weighted images (MT+T2WI). MATERIALS AND METHODS: In ten normalvolunteers, T2-weighted images without MT (MT-T2WI) and with MT(MT+T2WI) were obtained. Off-set pulses used inMT+T2WI were 400, 600, 1000, 1500, and 2000Hz. In 60 clinical cases infarction(n=10), brain tumors(n=5), traumatichematomas(n=5), other hematomas(n=3) vascular malformation(n=2) white matter disease(n=2) normal(n=31) andothers(n=2), both MT-T2WI and MT+T2WI images were obtained using an off-set pulse of 600 Hz. In all volunteers andpatients, MTR in various normal brain parenchyma and abnormal areas was measured. RESULT: The MTRs of white andgray matter were 48% and 45% respectively at 400 Hz, 26% and 22% at 600Hz, 12% and 11% of 1000Hz, 10% and 9% 1500HZ, and 9% and 8% at 2000Hz of RF. The MTR of CSF was 43% at 400 Hz of off-resonance RF, while the contrastresolution of T2WI was poor. An off-resonance of 600Hz appeared to be the optimal frequency. In diseased areas,MTRs varied but were usually similar to or lower than those of brain parenchyma. CONCLUSION: The optimaloff-resonance RF on MT+T2WI appears to be 600 Hz for relatively high MTR of brain parenchyma and low MTR of CSF,in which MTRs of white and gray matter were 26% and 22%, respectively, of 600Hz off-set pulse. The MTRs ofcerebral lesions varied and further studies of various cerebral lesions are needed.