CAJ | 학술논문

目的测量兆伏级锥形束CT (MVCBCT)成像在头颈部图像引导放疗的周边剂量(PD),评价PD与MVCBCT成像机器跳数(MU)间关系,探讨MVCBCT扫描射野对PD的影响.方法将0.65 cm3电离室插放在特设固体水体模中,使用MVCBCT图像采集预案对体模头颈部扫描,测量射野外体模中心垂直平面在不同深度和距射野边缘不同距离的PD.使用相同电离室在体模中参考点上审视MVCBCT成像的MU与PD的线性关系,并在射野外体模横断面上测量PD均匀性.结果在体模中测量的PD随着射野外距离增加呈指数下降,随着测量深度增加而降低,并随着扫描射野增大而增加.PD与MVCBCT成像MU间呈线性正比关系.PD分布不均匀,高剂量区位于前部.结论 MVCBCT成像时的PD主要依赖于MVCBCT成像MU和扫描射野.临床应用时应尽量考虑在不牺牲图像质量前提下,减少MVCBCT成像MU和缩小扫描射野降低PD.
목적 측량조복급추형속CT (MVCBCT)성상재두경부도상인도방료적주변제량(PD),평개PD여MVCBCT성상궤기도수(MU)간관계,탐토MVCBCT소묘사야대PD적영향.방법 장0.65 cm3전리실삽방재특설고체수체모중,사용MVCBCT도상채집예안대체모두경부소묘,측량사야외체모중심수직평면재불동심도화거사야변연불동거리적PD.사용상동전리실재체모중삼고점상심시MVCBCT성상적MU여PD적선성관계,병재사야외체모횡단면상측량PD균균성.결과 재체모중측량적PD수착사야외거리증가정지수하강,수착측량심도증가이강저,병수착소묘사야증대이증가.PD여MVCBCT성상MU간정선성정비관계.PD분포불균균,고제량구위우전부.결론 MVCBCT성상시적PD주요의뢰우MVCBCT성상MU화소묘사야.림상응용시응진량고필재불희생도상질량전제하,감소MVCBCT성상MU화축소소묘사야강저PD.
Objective To evaluate the peripheral dose (PD) from megavoltage cone-beam CT (MVCBCT) imaging for head-and-neck region image-guided radiation therapy,to determine the correlation of PD with monitor unit (MU),and to investigate the impact of imaging field size on the PD.Methods Measurements of PD from MVCBCT were made with a 0.65 cm3 ionization chamber placed in a specially designed phantom at various depths and distances from the field edges.The PD at reference point inside the phantom was measured with the same ionization chamber to investigate the linearity between MU used for MVCBCT and the PD.The homogeneity of PD in the axial plane of the phantom were measured.Results PD from MVCBCT increased with increasing number of MU used for imaging and with increasing the field size.The measured PD in the phantom decreased exponentially as distance from the field edges increased.PD also decreased as the depth from the phantom surface increased.There was a strong linear relationship between PD and MUs used for MVCBCT.The PD was heterogeneous,with higher dose at the anterior than the posterior.Conclusions The PD from MVCBCT depend much on the MVCBCT delivery MU and the scan field size.In clinic,using the smallest number of MU allowable and reducing MVCBCT scanning field size without compromising acquired image quality is an effective method of reducing the PD.