| Objective: Gliomas are the most common primary neop- lasms of the central nervous system in adults and glioblastoma in particular being the most common. The prognosis for patients with high-grade gliomas has remained poor despite improvements in radiotherapy and chemotherapy. Accurate preoperative diagnosis of the tumor grade is important for the determination of appropriate treatment strategies. Magnetic resonance diffusion imaging is the unique method of measuring and imaging the diffusion of the water molecule in vivo at present. It can reflect the microscopical movement of water molecule .It is a method of fMRI (functional MR imaging) which is studying brain diseases at the cell level based on EPI (echo planar imaging) technique. Magnetic resonance diffusion imaging includes DWI (diffusion weighted imaging,) and DTI(diffusion tensor imaging). DWI has been applied routinely for several years mainly in the diagnosis of acute cerebral infarction. DTI is an advanced quantitative form of DWI. DTI is a modification of DWI that is sensitive to the preferential diffusion of brain water along axonal fibres, a property called anisotropic diffusion; this technique can demonstrate white matter tract anatomy and can detect subtle changes in white matter tracts in diseases。DTI can be used to measure not only the magnitude (diffusivity), but also the directionality (anisotropy) of water diffusion. Fractional anisotropy (FA) and average diffusion coefficient (ADC) are the quantitative indices for diffusivity and anisotropy, respectively. The microstructural organization of the brain tissue affects the molecular motion of water. Therefore, the FA and MD reflect microstructural changes of tissue caused by damage from degenerative diseases, brain ischemia and brain tumors. The histological diagnosis of glioma malignancy is based on the presence of nuclear heteromorphism, nuclear mitosis, endothelial proliferation, and necrosis. These characteristics may affect the FA and MD values of gliomas.This study used DTI technique with echo-planar technique to discuss the value of preoperative evaluation of gliomas, to measure the average diffusion coefficient(ADC) and relative average diffusion coefficient(rADC) of different tumor patients in differentiating solid portion, necrotic region, edema region, normal brain tissue of opposite side, to study the role of these indices measurement in the preoperative grading and prognosis prediction of brain and to help the clinical diagnosis and treatment.Methods and materials: This study included 39 patients of gliomas proved by surgery and pathology diagnosis (15 females and 24 males) age 16-59 (mean age 43) treated at the Second Hospital of Hebei Medical University, from April 2006 to October 2006, and the number of grade(â… ï½žâ…¡)(low-grade) and grade(Ⅲ～Ⅳ)(high-grade) is 30 and 9 respectively, the standard of pathological grading is set according to WHO classification criteria of brain tumors. All the patients received neither radiological nor chemical therapy for their tumor prior to MRI examination. All the patients were examined with routine MRI, echo-planar MR DTI and a contrast material–enhanced T1-weighted sequence on a Signa 3.0 T clinical imaging system,and 8-channel array head coil. All the MR DTI data were transmitted into ADW4.2 workstation for post-processing, and were analysed with Functool software. The regions of interest (ROIs) were determined on the T2WI or the TIWI with contrast medium according to characteristic of image. With three regions of interest in each region measurement was taken for three times and their average was designated in calculation. ADC maps and ADC values of solid portion, necrotic region, edema region of the tumor, and normal white matter of opposite side were analysed and measured respectively, rADC values were calculated. All the data were precessed SAS6.12 soft ware. All the metrologic data were designated as average±standard deviation. Statistical significance was set at P < 0.05.Results:1 Routine MRI and DTI can show clearly the tumors of all patients. Signal intensity of solid portion, necrotic region of the tumor and peritumoral edema and normal brain tissue were obviously different in ADC maps. 2 Mean ADC values of solid portion of low-grade gliomas (1.42±0.42×10-3mm2/s)were higher than those of high-grade gliomas(1.21±0.16×10-3mm2/s). Differences between the mean ADC values of low-grade gliomas and high-grade gliomas were not significant(T=2.0923,P>0.05).3 Mean ADC values of peritumoral edema of low-grade gliomas (1.42±0.42×10-3mm2/s)were higher than those of high-grade gliomas(1.21±0.16×10-3mm2/s). Differences between the mean ADC values of low-grade gliomas and high-grade gliomas were not significant(T=0.6515,P>0.05).4 Mean ADC values of necrotic region of low-grade gliomas (1.42±0.42×10-3mm2/s)were higher than those of high-grade gliomas(1.21±0.16×10-3mm2/s), differences between the mean ADC values of low-grade gliomas and high-grade gliomas were not significant(T= 2.2224,P>0.05).5 In high-grade gliomas group, mean ADC values of solid portion, necrotic region of the tumor and peritumoral edema region were higher than those of contralateral normal white matter(0.85±0.10×10-3mm2/s); mean ADC values of necrotic region of the tumor were higher than other three regions. Significant differences of mean ADC values were found in solid portion, necrotic region of the tumor ,and peritumoral edema region compared with contralateral normal white matter. Mean ADC values of necrotic region of the tumor were significantly different from those of other three regions. There was no significant difference between solid portion and peritumoral edema region.6 In low-grade gliomas group, mean ADC values of solid portion, necrotic region of the tumor and peritumoral edema region were higher than those of contralateral normal white matter(0.79±0.13×10-3mm2/s); mean ADC values of necrotic region of the tumor were higher than other three regions. Significant differences of mean ADC values were found in solid portion, necrotic region of the tumor , and peritumoral edema region compared with contralateral normal white matter. Mean ADC values of necrotic region of the tumor were significantly different from those of other three regions. There was no significant difference between solid portion and peritumoral edema region.7 Mean rADC values of solid portion of low-grade gliomas (1.81±0.44)were significantly(T= 3.2573,P<0.05) higher than those of high-grade gliomas(1.44±0.20).8 Mean rADC values of peritumoral edema of low-grade gliomas (1.93±0.29)were higher than those of high-grade gliomas(1.79±0.19). Differences between the mean rADC values of low-grade gliomas and high-grade gliomas were not significant(T= 0.8207,P>0.05).9 Mean ADC values of necrotic region of low-grade gliomas (1.42±0.42×10-3mm2/s)were higher than those of high-grade gliomas(1.21±0.16×10-3mm2/s). Differences between the mean ADC values of low-grade gliomas and high-grade gliomas were not significant(T= 1.0872,P>0.05). Conclusion:1 ADC maps can clearly show tumors. Signal intensity of solid portion, necrotic region of the tumor and peritumoral edema and normal brain tissue were obviously different.2 ADC value can be used to distinguish not only normal white matter from solid portion, necrotic region of the tumor and peritumoral edema, but also necrotic region from solid portion of the tumor and peritumoral edema.3 The mean rADC value can be used to distinguish solid portion of high-grade glioma from those of low-grade glioma; the mean rADC values of solid portion of low-grade gliomas were higher than those of high grade gliomas.
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