A CT based dosimetry system for intracavitary therapy in carcinoma of the cervix

The physical dose distribution from intracavitary sources used in the treatment of carcinoma of the cervix can be accurately calculated in three dimensions. However, it is no simple matter to relate dose to critical tissues within the pelvis. We have studied 10 patients and have used CT scanning with dummy sources to determine the dose to lymph nodes, bladder and rectum. This technique may be superior to the use of orthogonal radiographs and highlights the limitations of the use of the flexible rectal dose meter. Further work will required to determine whether or not the morbidity of radical radiotherapy can be reduced using such detailed dosimetry to adjust therapy and eliminate small areas of high dose to critical normal tissues. In one case, CT showed a spontaneous and unexplained uterine perforation by the intrauterine tube one day after check films had shown a satisfactory position.