急性期放射性脑损伤磁共振扩散张量成像的定量研究

目的 利用磁共振扩散张量成像(DTI)定量分析,探讨正常脑组织不同部位急性期放射损伤的敏感性。方法 44例欲行全颅放疗的颅内肿瘤患者,在放疗前及放疗后3周行磁共振常规扫描、增强扫描及扩散张量成像,测量非肿瘤侧大脑半球接受总放射剂量为27 Gy时的等剂量区域内脑回灰质、脑回白质、深部灰质、深部白质的表观扩散系数(ADC)、部分各向异性(FA)、相对各向异性(RA)、容积比率(VR)等指标,并进行对比分析。 结果 所有患者常规及增强磁共振扫描非肿瘤侧大脑半球均未发现异常信号,而放疗后脑回灰质ADC值升高(t=-3.819,P<0.05),脑深部灰质核团ADC、容积比率值升高(t=-3.31、-2.810,P<0.05),脑深部灰质核团FA、RA值降低(t=2.906、2.349,P<0.05),其余部位放疗前后DTI各指标差异无统计学意义。结论 在急性期脑灰质较白质对放疗损伤敏感,DTI能从组织细胞功能水平对放射性脑损伤急性反应进行评价。

Quantitative study on MR diffusion tensor imaging at acute stage of radiation-induced brain injury

Objective To explore the sensibility of radiation-induced normal brain injury in different regions at acute stage after all cranial radiotherapy by MR diffusion tensor imaging(DTI). Methods A total of 44 patients with brain tumors undergoing whole cranial radiotherapy were examined with convention and enhancement magnetic resonance imaging and diffusion tensor imaging before and three weeks after radiotherapy. The apparent diffusion coefficient(ADC), fractional anisotropy(FA), relative anisotropy(RA) and volume ratio(VR) of DTI in contralateral brain hemisphere after radiotherapy with the dose of 27 Gy were measured and analyzed in different regions. Results No abnormal signal intensities were revealed in convention and enhancement MRI.ADC values in superficial cerebral convolution gray matter, ADC and VR values in deep gray nucleus were increased(t=-3.321,-2.810, P<0.05 ), while FA and RA values in deep gray nucleus were descended(t=2.906,2.349, P<0.05). There was no statistically significant difference among DTI index in other regions. Conclusions The brain gray matter more sensitive to radiation-induced brain injury in than white matter at acute stage of radiation. DTI could be used to evaluate the functional changes at the histocytology level of radiation-induced brain injury, and to explain the early clinical reactions after radiotherapy.