16 Cervix Carcinoma

Cervix Cancer 335

7.1 cm in width, and 5.4 cm in thickness for limited disease and 9.7, 8.6, and 7.1 cm, respectively for extended disease (96). The computer calculated volumes average 87 cm 3 (from 46 - 155 cm 3 ) for the reference isodose going through point A corresponding to a total isoeffective dose for the reference isodose at point A from 73 - 83 for limited and from 80 - 90 Gy for extended disease. The 60 Gy reference volumes average 176 and 316 cm 3 , respectively, in limited and extended disease assuming an isodose of 4.7 Gy and 3.1 Gy to be isoeffective (50 Gy EBT + BT (96)). Fig 14.13: Vienna Method (continued 4)

Fig 14.13F: Typical individual adaptation of the standard dose distribution for a large tumour extending into the lateral and posterior parametrium on the left. Increase of the dwell times in the ring on the left and reduction by one ring position on the right (compare figs. 5,14 (same patient)). Asymmetrical enlargement of the treated volume (100%: 89 Gy) in the posterior left lateral direction according to individual tumour spread without overall significant enlargement of the treated volume (108 cm 3 ). The bilateral dimensions of the 89 and 60 Gy volume are indicated, which differ by 8 mm and 9 mm, respectively, in the lateral direction. The dose to point A is 7.3 Gy on the right side and 8.6 Gy on the left. The 60 Gy reference volume is 316 cm 3 . (For dose to the critical organs compare Fig 14.14) Sectional image based treatment planning for dose calculation has been systematically used since one decade. If the axis of the uterine tandem is chosen as the reference axis, the following relationships hold (see fig. 5.2 (imaging chapter)): (para) sagittal MRI planes parallel to the axis of the uterine tandem correspond roughly to the lateral radiograph (if the axis of the uterine tandem is not laterally deviated), (para)coronal MRI planes parallel to the axis of the uterine tandem correspond roughly to the anteriorposterior radiograph (if the axis of the uterine tandem is parallel to the craniocaudal body axis), (para)transverse planes (MRI/CT) parallel to the axis of the vaginal sources (ring) have no corresponding projection images. If sectional images cannot be introduced digitally into the computerized treatment planning system, the main issue is to confirm on the images