Purpose: To determine the potential of apparent diffusion coefficient
(ADC) in predicting the pathologic grade and prognosis of primary
brain tumors.
Materials and methods: MR images of 27 patients with primary
brain tumors were reviewed. For each individual patient, 3-4 regions
of interest (ROIs) were placed manually over solid tumor components
on MR images that corresponded to the maximum contrast enhancing
region, if any. Both hemorrhagic and necrotic regions were
avoided. The lowest ADC value was calculated from images with
diffusion gradient b values of 0, 500, and 1000 sec/mm2. ADC values
were correlated with the final histologic grade as well as with post operative
disease free survival (DFS). A P value <0.05 was considered
significant.
Results: A significant negative correlation was found between ADC
and tumor grading (R = -0.65, P = 0.003). Among the studied cohort,
18 patients were subjected to complete surgical resection of their
tumor burden. Along a median follow-up period of 15 month, 12/18
(67%) operable patients developed local tumor recurrence, whereas,
6 (33%) patients remained disease free. The preoperative minimum
ADC values of the progression group were significantly lower than
those of the stable group (mean, 0.7 x 10-3 mm2/sec vs. 1.0 x 10-3
mm2/sec, P <0.001).
Conclusion: Quantitative Diffusion-weighted MR Imaging is a simple
and reliable technique for preoperative grading and outcome prediction
of primary brain tumors.