CAJ | 학술논문

目的探讨保乳术后自主呼吸控制(ABC)辅助全乳调强放疗(IMRT)过程中分次内及分次间靶区位移对剂量分布的影响.方法 ABC辅助CT模拟定位,获得3个呼吸状态的5套CT图像,分别为自主呼吸(FB)1套、适度深吸气呼吸控制(mDIBH)2套、深呼气呼吸控制(DEBH)2套.放疗10～15次后,ABC辅助重复CT模拟定位,并获得与初次定位相同的5套CT图像.在Pinnacle3治疗计划系统中,以初次定位的第1套mDIBH状态下CT图像制定正向IMRT计划,将此计划分别复制到初次定位的第2套及重复定位的第1套mDIBH状态下的CT图像上,保持射野角度、方向、大小、形状及处方剂量等参数不变,比较计划中某一子野中高剂量区所覆盖的乳腺体积变化.结果初次定位的第1套mDIBH状态下CT图像制定的IMRT计划中,多叶准直器(MLC)遮挡后,挡高剂量线子野内接受103%高剂量照射的平均乳腺体积为(1.16±0.39)cm3,同一IMRT计划复制到初次定位的第2套mDIBH状态下的CT图像上,挡高剂量线子野内接受103%高剂量照射的平均乳腺体积为(3.88±1.07)cm3,两者差异无统计学意义(P=0.103).同一IMRT计划复制到重复定位的第1套mDIBH状态下的CT图像上,挡高剂量线子野内接受103%高剂量照射的乳腺体积为(51.66±8.68)cm3,两者差异有统计学意义(P<0.01).结论如果保持相同的mDIBH阈值,单次放疗中,靶区位移对IMRT照射剂量分布无明显影响;如果不进行摆位误差校正,分次照射间IMRT计划中挡高剂量区子野位置会发生明显变化,从而导致照射剂量分布的明显变化.
목적 탐토보유술후자주호흡공제(ABC)보조전유조강방료(IMRT)과정중분차내급분차간파구위이대제량분포적영향.방법 ABC보조CT모의정위,획득3개호흡상태적5투CT도상,분별위자주호흡(FB)1투、괄도심흡기호흡공제(mDIBH)2투、심호기호흡공제(DEBH)2투.방료10～15차후,ABC보조중복CT모의정위,병획득여초차정위상동적5투CT도상.재Pinnacle3치료계화계통중,이초차정위적제1투mDIBH상태하CT도상제정정향IMRT계화,장차계화분별복제도초차정위적제2투급중복정위적제1투mDIBH상태하적CT도상상,보지사야각도、방향、대소、형상급처방제량등삼수불변,비교계화중모일자야중고제량구소복개적유선체적변화.결과 초차정위적제1투mDIBH상태하CT도상제정적IMRT계화중,다협준직기(MLC)차당후,당고제량선자야내접수103%고제량조사적평균유선체적위(1.16±0.39)cm3,동일IMRT계화복제도초차정위적제2투mDIBH상태하적CT도상상,당고제량선자야내접수103%고제량조사적평균유선체적위(3.88±1.07)cm3,량자차이무통계학의의(P=0.103).동일IMRT계화복제도중복정위적제1투mDIBH상태하적CT도상상,당고제량선자야내접수103%고제량조사적유선체적위(51.66±8.68)cm3,량자차이유통계학의의(P<0.01).결론 여과보지상동적mDIBH역치,단차방료중,파구위이대IMRT조사제량분포무명현영향;여과불진행파위오차교정,분차조사간IMRT계화중당고제량구자야위치회발생명현변화,종이도치조사제량분포적명현변화.
Objective To explore the influence of intrafraction and interfraction target displacement on the dose distribution in the target of forward whole-breast intensity-modulated radiotherapy (IMRT) assisted by active breathing control (ABC). Methods Each of the selected patient who had received breast conserving surgery was immobilized and received the primary CT simulation assisted by ABC device to get five sets of CT images in three different breathing status, including free breathing (FB) ( one set), moderate deep inspiration breathing hold (mDIBH) (two sets) and deep expiration breathing hold (DEBH) (2 sets). After 10 to 15 fractions of radiation, the repeated CT simulation was completed and the same five sets of CT images were obtained at FB, mDIBH, and DEBH, respectively. In the Pinnacle3 treatment planning system, the forward IMRT planning was completed on the first set of mDIBH CT images from the primary CT simulation, and the planning was separately copied by the special system order to the second set of CT images from the primary CT simulation and to the first set of CT images from the repeated CT simulation, keeping the primary angle, direction, size and shape of the MLC field and prescribed dose un-changed, the volumes covered by selected high dose area in the selected segment were compared. Results In the planning based on the first set of mDIBH CT images from the primary CT simulation, the volume irradiated by equal and more than 103% of prescribed dose in the segment was (1.16±0.39) cm3, and the volumes were (3.88±1.07) cm3 and (51.66 ± 8.68) cm3 in the plannings copied from the first set of mDIBH CT images from the primary CT simulation respectively to the second set of CT images from the primary CT simulation and first set of CT images from the repeat CT simulation, the difference of the volume in the two plannings based on the two set mDIBH CT image from the primary CT simulation was not statistically significant (t = -1. 672, P =0. 103). The difference of the volume in the two plannings based on the two sets of mDIBH CT images respectively from the primary and repeat CT simulations had a significant difference (t = - 5. 728, P < 0.01 ). Conclusion If the same threshold of mDIBH is maitained during IMRT after breast conserving surgery, the influence of the intrafraetion target displacement on the dose distribution is not significant. However, if set-up error is not adjusted, the interfraction change of position of the segment given to cover the high dose area in the IMRT planning will be significant, resulting in a significant change of dose distribution in the breast.