[An auxiliary system for optimizing the simulation and percutaneous irradiation of cranial-caudal contiguous head-neck-mediastinal fields].
OBJECTIVE
Percutaneous irradiation in the head and neck region via opposing lateral fields with caudally contiguous ventral and/or dorsal fields makes very high demands on simulation, instrument adjustment and documentation. At the outer boundaries of the irradiation volumes, there is always the danger of overdosage or underdosage with the familiar consequences.


METHODS
Four targeting systems in one plane were inserted in a perspex frame each consisting of two concentric rings and two orthogonal crossbars. Under simulation conditions, the lateral radiation fields take up one half of the targeting systems and the ventro-dorsal fields occupy the remaining half. The corresponding targeting systems project exactly on or into each other with compensation of the beam divergence.


RESULTS
A definitively exact irradiation via cranio-caudally contiguous fields with different incident beam direction is possible by using the four targeting systems in one plane. Compensation of divergence is aimed for by rotation of the table and gantry angle modification, errors of compensation can already be checked optically from 0.5 degree. Deviations of 5 mm in the simulated longitudinal arrangement of the contiguous fields can be imaged on the documentation film made with therapy activity.


CONCLUSIONS
On the one hand, the auxiliary system presented allows both recognition of undesired field overlap and gaps in contiguous fields with different incident beam direction. On the other hand, it can be unequivocally documented whether the therapy is correct. Treatment errors can thus be minimized.
Sistermanns
J
J
Abteilung für Strahlentherapie und radiologische Onkologie, Krankenhaus Maria Hilf GmbH, Mönchengladbach.
D003198:Computer Simulation; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D008479:Mediastinal Neoplasms / Q000532:radiotherapy*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*
Hilfssystem zur Optimierung von Simulation und perkutaner Radiatio bei kranial-kaudal aneinandergrenzenden Kopf-Hals-Mediastinum-Feldern.