锥形束CT预测前列腺癌靶区运动的研究

Study on cone beam CT in predicting the movement of prostate cancer target

目的分析前列腺癌首次放疗前和代表相对计划CT分次间靶区位移的分次放疗前锥形束CT(CBCT)校准数据之间的关系,以期预测分次间靶区位移。方法选取16例前列腺癌患者为研究对象,记录其首次放疗前CBCT校准位移值和分次放疗前CBCT校准位移平均值,分析两者之间的相关性并初步建立分析、预测靶区运动的一元回归方程模型。结果16例患者首次放疗前左右、头脚、腹背方向的CBCT校准位移绝对值为(0.384±0.270)、(0.980±0.570)、(2.462±1.105)mm,平均分次放疗前CBCT校准位移绝对值为(0.719±0.464)、(1.387±0.757)、(2.884±1.607)mm。首次放疗前CBCT校准位移绝对值和平均分次放疗前CBCT校准位移绝对值在左右方向上呈弱相关(r=0.359,P>0.05),在头脚方向上呈弱相关(r=-0.326,P>0.05),在腹背方向上呈强相关(r=0.833,P<0.01)。结论临床仅可应用腹背方向上首次放疗前CBCT校准位移预测分次间靶区位移(背向),但试验过程仍需优化。

Objective To analyze the relationship between the calibration data of cone beam CT(CBCT)before first radiotherapy and the data representing the target fractional displacement before fractional radiotherapy for treatment of prostate cancer,so as to predict the target fractional displacement.Methods Sixteen patients with prostate cancer were selected.CBCT calibration displacements before first radiotherapy and mean values of fractional radiotherapy were recorded.The correlation between the mean value and calibration displacement value was analyzed.Then a regression equation model was established initially to analyze and predict the target movement.Results The absolute mean values of CBCT calibration displacement before first radiotherapy were(0.384±0.270)mm in directions of left-right,(0.980±0.570)mm in head-feet directions,(2.462±1.105)mm in anterior-posterior directions for all the patients,and were(0.719±0.464)mm,(1.387±0.757)mm,(2.884±1.607)mm,respectively before fractional radiotherapy.There was a weak correlation between absolute mean value of CBCT calibration displacement before first radiotherapy and absolute mean value for fractional radiotherapy in directions of left-right and head-feet directions(r=0.359,-0.326,P>0.05),and strong correlation between absolute mean value for fractional radiotherapy of CBCT calibration displacement and absolute mean value before first radiotherapy in anterior-posterior directions(r=0.833,P<0.01).Conclusion CBCT calibration displacement before first radiotherapy in anterior-posterior directions could be used to predict the target displacement of fractional radiotherapy(posterior direction).It is necessary to optimize the experiment process.