Time-Dependent Diffusion Using Oscillating-Gradient Spin-echo Sequence in Extra-Axial Brain Tumors [Presidential Award Proceedings]

Oscillating-gradient spin-echo (OGSE) prototype sequences can shorten the eŠective diŠusion time (DeŠ) and add information regarding the internal structure of lesions. The purpose of our study was to investigate the utility of changes in diŠusivity between short and long DeŠ values in distinguishing diŠerent types of extra-axial brain tumors. Twelve patients with meningiomas, 13 with acoustic neuromas, and 11 with pituitary adenomas were scanned using a 3T magnetic resonance (MR) scanner. DiŠusion tensor imaging (DTI) was performed using b-values of 0 and 1000 s/mm2. OGSE imaging using a trapezoid-cosine waveform was performed with DeŠ values of 6.5 and 35.2 ms. The diŠusivity of each tumor was measured after setting a manually deˆned region of interest (ROI). The relative percentage change between the shorter and longer DeŠ values was then calculated. The relative percentage changes of the three tumor types were compared using the Steel-Dwass test. The relative percentage changes of l2, l3, and mean diŠusivity (MD) were signiˆcantly higher in pituitary adenomas than in meningiomas and acoustic neuromas, but not signiˆcantly diŠerent between meningiomas and acoustic neuromas. The dependence of l2, l3, and MD on DeŠ values between 6.5 and 35.2 ms was stronger in pituitary adenomas than in meningiomas and acoustic neuromas, suggesting diŠerences in internal tissue structure. Our results showed that the use of DTI with a shorter DeŠ provides additional information about the microstructure of brain tumors. OGSE imaging may help in the diŠerentiation of diŠerent types of tumors that show atypical imaging ˆndings on conventional MRI.