16 Cervix Carcinoma

318 Cervix Cancer

E: Placement of the dummy sources.

F,G: AP and lateral radiographs with the mould delineated and certain reference points for dose calculation: A: cervix; B: Bladder ICRU point; C: Rectal points (in the rectal probe); D: Pelvic wall points.

Drawing and positioning of the vaginal catheters: taking into account the anatomy of the patient, the tumour topography and the target volume, the position of the two vaginal catheters is drawn. The two catheters must be parallel to the anterior superior surface of the mould (parallel to the surface of the cervix), lateralised to the left and right part of the cervical lip, parallel to each other, and separated by a distance equal to the mean length of the two vaginal sources. The depth of the vaginal catheters in the mould is decided according to the projected source length, from 3 up to 6 mm in a short and long source, respectively. The lengths of the vaginal catheters and their space are determined according to the dimensions of the tumour. This length can be modified and adapted for the loading with the radioactive source dependent on the situation shown on the radiograph. The two vaginal catheters are introduced and fixed on the internal surface of the moulded applicator. Final preparation of the mould applicator: Different modifications of the mould are necessary: one hole for the cervical os, an indication for the external meatus of the urethra, and several perforations to fix the mould to the vaginal wall and to allow circulation of the liquid antiseptics for daily vaginal irrigation with liquid antiseptics, which is done through a tube inserted into the mould. These perforations eliminate the risk of displacement of the device, the vaginal mucosa herniates through each perforation. No vaginal packing is necessary, as the packing is integrated into this moulded applicator, keeping the catheters in place at the same position and keeping the same topography throughout the whole period of brachytherapy (104). With this system the patient can move out of the bed without risk of displacement of the material and the complications of prolonged bed rest such as thrombosis can be prevented and better tolerance is obtained.