| PURPOSE: To evaluate the clinical value of MR diffusion-weighted imaging(DWI) and ADC maps in the diagnosis of brain tumor and tumor-lesions and discuss the corresponding biophysics mechanism. Find a correlation, if any, between the ADC and histologic analysis of rumors.METERIALS AND METHODS: 57patients with brain tumor and tumor-like lesions (25 gliomas , 14 metastatic tumor, 11 meningiomas, 2 malignancy neoplasms, 2 viral encephalitis, 2 brain abscess) were prospectively studied using routine MR and diffusion-weighted with a single-shot gradient-echo echo-planar pulse sequence(6265/101[TR/TE]) and b values of 0 and 1000s/mm2. Signal characteristics on routine MR were compared with the appearances on DWI and ADC maps. The ADC values were calculated within various brain tumor, various tumor components ,both benign and malignant astrocytoma. Comparisons were made by analysis of variance. We also evaluated the correlation between ADC values and the nuclear-to-cytoplasmic (N/C) ratio from 11 astrocytoma histologic samples .RESULTS: The ADC values of solid gliomas(1.16 0.21) 10-9m2/s, metastases (0.97 0.26) 10-9m2/s and meningioma(1.09 0.28) 10-9m2/s were in the same range other than infection and granulocytic leukemia infiltration. ADCs were higher in low-grade(1.28 0.16) 10-9m2/s than high-grade astrocytomas (1.11 0.13) 10-9m2/s and glioblastomas (0.82 0.13) 10-9m2/s(p<0.01). Virous tumor components have striking difference(p<0.001). Nonenhancing tumor were found on DWI. The ADC value of astrocytoma correlated well with tumor N/C ratio (r=-0.77,p<0.01 ). CONCLUSION: The apparent diffusion coefficient may be predictive of tumor classification although there is some overlap and may be a useful tool in characterizing nonenhancing tumor components, inflammatory lesions and the other diseases from Hematopoietic system. Measurement of water diffusivity and N/C ratio suggest thathigher N/C ratio contributes to more restricted diffusion.
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