宫颈癌后程放疗时子宫A点截面偏移的测量及影响

Result and Influence of Measuring A Point Section of Uterus Excursion in Late Course Radiotherapy of Cervical Carcinoma

目的探讨宫颈癌放疗后程实施盆腔外照射时子宫A点截面偏移对全盆腔大野及中央挡铅野的剂量分布及均匀性的影响,寻求宫颈癌四野照射合理铅块设计配合腔内照射治疗的更佳方法。方法随机测量128例中晚期宫颈癌患者放疗后程子宫A点截面的位置,后装治疗时,插入宫腔管后用泛影葡胺或优维显浸泡纱布填塞固定,在模拟定位机下测量宫颈口上2 cm截面(A点截面)宫腔管与人体中线(左右间)、前后中平面(前后野中央)相互距离的关系。结果子宫A点截面在正中线位者44例,占34.38%(44/128);偏右者33例,占25.78%(33/128);偏左者51例,占39.84%(51/128)。其中偏移在1 cm以上者46例,占35.94%(46/128),左右最大偏移为2.1 cm。子宫A点截面在正中平面位(前后野中间)者12例,占9.38%(12/128);偏前者43例,占33.59%(43/128);偏后者73例,占57.03%(73/128)。其中偏移在1 cm以上者49例,占38.28%(49/128),前后最大偏移为2.3 cm。结论子宫A点截面前后移位对放射剂量分布、均匀性无影响;而左右偏移对挡铅后的放射剂量分布与均匀性有一定影响。宫颈移位型宫颈癌盆腔四野照射时如果仍为盆腔中央挡铅,可能导致子宫旁的低剂量区。采用沿子宫中轴平面挡铅法,个体化调整盆腔四野挡铅,能更好地消除子宫旁的低剂量区。

Objective To explore the effect of A point section of uterus excursion on dose distribution and homogeneous of central Pb shield field and pelvic field, and to study more reasonable method of radiation barrier for cervical carcinoma treated with external radiation. Methods The 128 cases of A point section position were measured randomly of middle or advanced uterus cervical carcinoma in late course radiotherapy. Tandem applicator was put into uterine cavity, and it was fixed with angiografin or ultravist soaked gauze. Under the simulator, the distance interrelations between Uterine axis（ in the A point section of uterus）and the body middle line （between right and left） , and the body front-back middle plane （between front field and back filed）were measured. Results A point section of uterus in body middle line had 44 cases,only about 34.38% （44/128） ; leaned to right be about 33 cases,only 25.78%, （33/128） ; leaned to left be about 51 cases,only 39.84% （51/128）. Removing more than 1 cm had about 46 cases,only 35.94% （46/128）. Maxi-excursion in the right and the left was 2.1 cm. A point section of uterus in the body middle plane （ between front field and back field） had 12 cases, only 9.38% （ 12/128 ） , leaned to front be 43 cases,only 33.59% （43/128） ; leaned to back be 73 cases,only 57.03% （73/128）. Removing more than 1 cm had about 49 cases, only 38.28% （49/128）. Maxi-excursion between the front and the back was 2.3 cm. Conclusion A point section of uterus excursion between the front and the back has no influence on radiologic dose distribution and homogenous. Removing between the left and the right have some influence on radiologic dose distribution and homogenous in central Pb shield field. It might bring about lower dose area around uterus with used fixed lead brick for radiation barrier when treated with external radiation. Cervical excursion cancer treated with external radiation used with lead brick along with the uterine central axis, and radiation barrier with lead brick individuate may help for to avoid the lower dose area around uterus.