[Head and neck adaptive radiotherapy: A tool for the detection of patients requiring adaptive radiotherapy]

The purpose of this work was to implement a simple dosimetric alert tool in a retrospective study for six patients suffering from head and neck cancer to detect when a patient might require an adaptive radiotherapy.

The dosimetric tool generates a 3D cartography of two dosimetric complementary information: a dose variation tolerance map and a dose differential map. The tolerance map is calculated on the initial scanner (CTinit) using the planned dose distribution. It shows for each voxel of each delineated volume the availability for local dose variations during the course of radiotherapy without exceeding the dose threshold. The differential dose map is generated on the tomographic image CBCT (CBCTtreatment). It shows dose variations between the planned and the actual delivered dose distribution for each voxel. By comparing both maps, when a voxel presents a value superior to the corresponding dose variation tolerance, an alert is generated and the anatomical areas concerned are visually indicated to the physician.

The application of the dosimetric tool on six patients with head and neck cancers reveals the ability of the tool to detect cases requiring a new treatment plan. Two patients whose the tumour shrinkage produced an increase of the delivered dose to the spinal cord beyond 45 Gy have been detected.

The development of the dosimetric tool allows the automatic detection, with no delineation needs, of patients suffering from head and neck cancers requiring an adaptive strategy.