Cerebral white matter: technical development and clinical applications of effective magnetization transfer (MT) power concepts for high-power, thin-section, quantitative MT examinations.

Abstract

To evaluate white matter disorders with magnetization transfer (MT) techniques. In 46 healthy volunteers and 46 clinical patients, MT Z spectra were obtained with various continuous-wave-equivalent MT powers (B1CW) and frequency offsets. With B1CW of 270 Hz and 4,000-Hz frequency offset, the MT ratio of normal callosal white matter was 59.2% +/- 1.5 (standard deviation), with less than 5% contribution from direct saturation and spin locking. A small statistically significant (P < .01) regional variation in normal white matter was seen. Plaques in MS patients had a broad (or wide) range of MT ratios; normal appearing white matter had a slightly reduced MT ratio. Vasogenic edema had a minimal effect on MT ratio, and radiation necrosis showed prominent reductions in MT ratio. High MT power techniques can expand the dynamic range of MT ratios, maintain a relatively pure MT effect, and be used effectively in MT imaging to evaluate white matter disorders.