盆腔肿瘤患者放疗期间体重指数变化对摆位误差及辐射剂量的影响

The effect of changes in body mass index on positioning error and radiation dose during radiotherapy in patients with pelvic tumors

目的探讨盆腔肿瘤(PT)患者放疗期间体重指数(BMI)变化对摆位误差及辐射剂量的影响。方法选取2021年10月至2022年3月新余市人民医院收治的37例PT患者作为研究对象,共收集到185次BMI测量及摆位误差、辐射剂量数据。根据BMI值分为正常组(BMI<25 kg/m2,n=16)、超重组(25 kg/m2≤BMI<35 kg/m2,n=7)与肥胖组(BMI≥35 kg/m2,n=14)。比较3组摆位误差,Spearman相关分析放疗期间BMI变化与X轴、Y轴、Z轴方向上摆位误差的相关性,评估位移误差引起靶区剂量的差异。结果3组X轴、Y轴、Z轴方向摆位误差比较差异有统计学意义(P<0.05);肥胖组X轴、Y轴、Z轴方向摆位误差均大于超重组、正常组,超重组大于正常组,差异有统计学意义(P<0.05)。随治疗周次增加,BMI下降呈增加趋势,摆位误差在X轴、Y轴方向呈增大趋势,差异有统计学意义(P<0.05);摆位误差在Z轴各时间点比较差异无统计学意义。BMI下降2~3 kg/m2摆位误差大于BMI下降1~<2 kg/m2及<1 kg/m2,且BMI下降1~<2 kg/m2大于BMI下降<1 kg/m2,差异有统计学意义(P<0.05)。Spearman相关分析显示,BMI变化与X轴(r=0.646,P<0.05)、Y轴(r=0.723,P<0.05)、Z轴(r=0.815,P<0.05)方向的摆位误差呈正相关。产生移位后计划的D95%、最小剂量、最大剂量均小于治疗计划,差异有统计学意义(P<0.05);而产生移位后计划的膀胱及左、右股骨头辐射剂量与治疗计划比较差异无统计学意义。结论行调强放射治疗的PT患者随BMI下降,X轴、Y轴、Z轴上的摆位误差增大,应根据BMI变化评估PT患者是否需重新制作热塑体膜。

Objective To investigate the effect of changes in body mass index(BMI)on positioning error and radiation dose during radiotherapy in patients with pelvic tumors(PT).Methods 37 PT patients admitted to Xinyu People's Hospital from October 2021 to March 2022 were selected as the research subjects,a total of 185 times of BMI,positioning error and dosimetry data were collected.37 PT patients were divided into the normal group(BMI<25 kg/m2,n=16),the overweight group(25 kg/m2≤BMI<35 kg/m2,n=7)and the obesity group(BMI≥35 kg/m2,n=14)according to the BMI value,Spearman rank correlation was used to analyze the correlation between BMI change during radiotherapy and the positioning errors in the X-axis,Y-axis and Z-axis directions,the difference in radiation dose caused by displacement error in the target area was evaluated.Results There were significant differences in positioning errors in the X-axis,Y-axis and Z-axis among three groups(P<0.05);the positioning errors in the X-axis,Y-axis and Z-axis directions in the obesity group were greater than those in the overweight group and the normal group,the over weight group was greater than the normal group,the differences were statistically significant(P<0.05).As the number of treatment weeks increased,BMI decline showed an increasing trend,and the positioning errors in the X-axis and Y-axis showed increasing trend,the differences were statistically significant(P<0.05);there was no significant difference in positioning errors at different time points on the Z-axis.The positioning errors in BMI decline 2~3 kg/m2 was greater than that in BMI decline 1~<2 kg/m2 and<1 kg/m2,the BMI decline 1~<2 kg/m2 was greater than BMI decline<1 kg/m2,the differences were statistically significant(P<0.05).Spearman correlation analysis showed that BMI changes were positively correlated with position-ing errors in the X-axis(r=0.646,P<0.05),Y-axis(r=0.723,P<0.05)and Z-axis(r=0.815,P<0.05)directions.The D95%,minimum dose and maxi-mum dose of plan after displacement were lower than those of the treatment plan,and the differences were statistically significant(P<0.05);there were no significant differences in the planned bladder,left and right femoral head projection doses between the plan after displacement and the treat-ment plan.Conclusion PT patients undergoing intensity modulated radiation therapy experience a decrease in BMI,increase the positioning error on the X-axis,Y-axis and Z-axis,evaluate whether PT patients need to remake thermoplastic films based on changes in BMI.