9 Reporting in Brachytherapy: Dose and Volume Specification

Reporting in Brachytherapy 187

Fig 6.18 : Small diameter applicator (6mm) in a wide oesophageal lumen with moderate stenosis. Position of the applicator is either concentric or eccentric. Dose prescription is at 5 mm from the applicator surface or at 10 mm from the source axis.

A: Position of the applicator is concentric. The reported dose is at 5 mm from the applicator surface (100%). However, this does not correspond to a certain dose at a certain depth in the oesophageal wall. Therefore, the maximum and minimum dose in the oesophageal wall should be reported in addition. In this case, this variation is between ~ 80% to 290% (factor 3.7). The dose at the applicator surface is 290%. However, this

dose does not correspond to a certain dose at a certain point on the luminal surface. Therefore, in addition to the maximum, the minimum dose should also be reported. In this case this is 100% (factor 2.9). B: If the applicator is eccentric, the dose at the mucosa/tumour surface varies between ~ 60% to 290% (factor 4.8), the dose within the oesophageal wall varies between ~ 45% to 290% (factor 6-7).

C: Concentric position of the applicator. Dose prescription is 10 mm from the source axis. The dose to be reported at 5mm from the applicator surface is 130%. In this case dose variations are as follows : mucosa/tumour surface: 130% to 370% (factor 2.9), within the oesophageal wall: 100% to 370% (factor 3.7).

D: Eccentric position of the applicator. Dose prescription is at 10 mm from the source axis. The dose to be reported at 5 mm from the applicator surface is 130%. Dose variations are as follows : mucosa/tumour surface : ~80 % to 370% (factor 4.6); within the oesophageal wall : ~ 60% to 370% (factor 6.2).