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目的:观察脊柱图像引导放射治疗(image guided radiation therapy,IGRT)不同方案放疗过程中放疗区域脊髓MRI弥散加权成像(diffusion-weighted imaging,DWI)的表观扩散系数(apparent diffusion coefficient,ADC),为IGRT优化提供实验依据。方法:选用雄性成年比格犬36只,根据放疗方案中照射野数(A,5、7、9野)、单次剂量(B,16、20Gy)、放射剂量率(C,4、6Gy/min)及照射角度(D,等角度、不等角度)4个临床放疗常用因素,按L12(3×23)正交实验表共12种方案对T7~T12椎体及其附件进行IGRT,每周1次,总剂量均为80Gy。每种方案3只犬。分别于放疗前、开始放疗后每2周进行放疗区域脊髓ADC值检测,并对所测得ADC值进行正交实验的方差分析,从而得出脊柱IGRT的较优方案。结果:放疗前各方案组间ADC值无统计学差异(P>0.05)。经过不同方案的放疗后,各方案组ADC值均出现升高,开始放疗后6周出现ADC最大值,至放疗结束后第3个月时所测ADC值均仍高于放疗前自身水平。相同时间点不同放疗方案脊髓ADC值存在差异(P<0.05),各时间点照射野5野、单次剂量20Gy,放射剂量率6Gy/min、等角度照射时的ADC最大,而照射野9野、单次剂量16Gy,放射剂量率4Gy/min、等角度照射时的ADC值最小。照射野数、单次剂量和放射剂量率对放疗区域脊髓ADC值的影响有统计学意义(P<0.05),照射角度对ADC值的影响无统计学意义(P>0.05);且各因素对脊髓损伤影响的主效应排序为单次剂量>放射剂量率>照射野数。结论:照射野数、单次剂量、放射剂量率及照射角度会影响脊柱IGRT放疗区域脊髓的损伤程度,应用IGRT时应选择优化方案。
OBJECTIVE: To observe the apparent diffusion coefficient (ADC) of diffusion-weighted imaging (DWI) of spinal cord in radiotherapy area under different regimens of spinal irradiation guided by guided radiotherapy (IGRT) IGRT optimization provides experimental basis. Methods: Thirty-six male adult beagle dogs were selected according to the radiation field number (A, 5, 7, and 9), single dose (B, 16 and 20 Gy), and radiation dose rate min and angle of irradiation (D, isometric and unequal) were used to determine the IGRT of T7-T12 vertebral body and its attachments according to the 12 clinical programs of L12 (3 × 23) Week 1, the total dose is 80Gy. Three dogs for each program. Respectively before radiotherapy, began radiotherapy every 2 weeks after radiotherapy area spinal cord ADC value detection, and the measured ADC value of the orthogonal experiment analysis of variance, resulting in spinal IGRT better program. Results: Before radiotherapy, there was no significant difference in ADC values between the two groups (P> 0.05). After the radiotherapy of different regimens, the ADC values of all the regimen groups increased, and the maximum value of ADC appeared 6 weeks after radiotherapy. The ADC value measured at 3 months after radiotherapy was still higher than that before radiotherapy. The ADC values of spinal cord at different time points were different (P <0.05). At each time point, the radiation field was 5 fields, the single dose was 20Gy and the radiation dose rate was 6Gy / min. , A single dose of 16Gy, radiation dose rate 4Gy / min, equal angle irradiation ADC value minimum. The effects of irradiation field number, single dose and radiation dose rate on the ADC value of radiotherapy area were statistically significant (P <0.05), and the influence of irradiation angle on ADC value was not statistically significant (P> 0.05) The main effects of spinal cord injury were ranked as single dose> radiation dose rate> irradiation field number. Conclusion: The number of irradiation field, single dose, radiation dose rate and irradiation angle will affect the degree of spinal cord injury in spinal IGRT radiotherapy area. IGRT should be optimized.