Effects of Magnetization Transfer in Gadolinium-Enhanced Brain MR Imaging

ABSTRACT

PURPOSE: To evaluate the effect of magnetization transfer(MT) in contrast-enhanced brain MR imaging of the various intracranial diseases. MATERIALS AND METHODS: We prospectively studied the effect of MT incontrast-enhanced brain MR imaging 101 patients with a variety of intracranial diseases. In all patients contrast-enhanced T1-weighted(TR/TE = 550/14) SE MR images with and without MT were obtained on a 1.5 Tsuper conducting unit(Magnetom, Siemens). The MT pulse used for MT images was an 8.1 msec(=250 Hz band width) syncpulse, 1000 Hz off-resonance. We randomly divided the patients into two groups group I and group II. Group I consisted of 54 patients in whom contrast-enhanced images without MT and then images with MT were obtained just ofter the injection of Gd-DTPA(0.1 mmol/kg). In group II(47 patients), contrast-enhanced images with MT and then the images without MT were obtained, considering the delayed-enhancement effect. The effect of MT was assessed visually and quantitatively. For quantitative assessment, contrast to noise ratios(CNR) were calculated in 27 cases with enhancing intracranial tumors larger than 1 cm. We then compared CNRs of contrast-enhanced images with and without MT. The paired t-test was used for statistical analysis. RESULTS: On visual assessment, only11.9%(12/101) of normally enhancing structures and only 20.3%(14/69) of enhancing lesions showed improved enhancement in images with MT. There was however, no case in which the enhancing lesion was seen only in MR image with MT but not in that without MT. On quantitative analysis there was no statistically significant difference between overall images with MT and those without MT(p>0.05). The average CNR of images with MT was higher than that of images without MT in group I, but not in group II. CONCLUSION: MT in contrast-enhanced brain MR imaging resulted in contrast improvement in a limited number(less than approximately 20%) of patients. Routine application of MT images to contrast-enhanced brain MR imaging may be of limited value. Further studies on the clinical usefulness of MT technique with more refined MT pulse are thus needed.