9 Reporting in Brachytherapy: Dose and Volume Specification

Reporting in Brachytherapy 185

NB : (1) For oesophagus and vagina, where large applicators can be introduced into the cavity, the mucosa is totally dilated and the external contour of the applicator coincides with the inner mucosal surface. The applicator and the lumen diameter then become identical, and the reference depth can be measured from the external surface of the applicator (Fig 6.19, 20C-H). (2) When a non-centered device is used (e.g. frequent in bronchus and with some systems in endovascular brachytherapy), it is difficult to specify the actual dose at the mucosa or at the reference depth. The best estimation of the maximum and minimum doses should then be reported (Fig 6.17, 18). 7.4.3 Minimum Target Dose The Minimum Target Dose is the minimum dose to the PTV. It should be (at least) equal to the dose defined by the clinician as adequate to treat the PTV. The Minimum Target Dose should be reported; this requires information about the depth and the length of the PTV. The Minimum Target Dose should be reported as absolute dose value (in Gy) and as a percentage of the dose at the reference point. 7.4.4 Reference depth – Reference point A Reference depth of 5 mm, from the surface in the organ wall, in the central plane, is recommended for oesophagus, bronchus and vagina (Fig 6.19, 20). In endovascular brachytherapy (Fig 6.20A), a reference depth of 1 mm, from the endothelium (surface wall) in the artery, is recommended for reporting dose to the patient, for coronary arteries. For peripheral arteries, a depth of 2 mm is recommended.

The reference point for reporting is located at the reference depth. Prescribing and reporting doses at the same depth certainly simplifies the procedures and reduces the risk of confusion and accidents (compare experience in postoperative vaginal brachytherapy) (Fig 6.20F).