Evaluation of underdosage in the external photon beam radiotherapy of glottic carcinoma: Monte Carlo study.
OBJECTIVE
Underdosage in the human larynx may be the true factor behind the decrease in local control rates.


METHODS
To evaluate underdosage with Monte Carlo a CT-based geometrical model of the patient's neck (mathematical neck) was created. Dose was calculated for a pair of 6 Me V parallel-opposed photon beams modulated with 15 degree steel wedges.


RESULTS
At least 5% of volume of 3.5 cm(3) hypothetical tumor near the air wall of the larynx receives less than 86% of the maximum tumor dose. The same volume received less than 91% of the maximum tumor dose when the mathematical neck had no air cavities.


CONCLUSIONS
We conclude the significant underdosage at the air-tissue interface in the larynx occurs in traditional radiotherapy treatments, especially in the glottic part of the larynx.
Spirydovich
Siarhei
S
Department of Radiation Oncology, Indiana University School of Medicine, Indianapolis, IN 46202-5289, USA. sspirydo@iupui.edu
Papiez
Lech
L
Moskvin
Vadim
V
Desrosiers
Paul
P
D019985:Benchmarking; D002277:Carcinoma / Q000532:radiotherapy*; D003198:Computer Simulation; D005931:Glottis / Q000528:radiation effects*; D006801:Humans; D021621:Imaging, Three-Dimensional; D007822:Laryngeal Neoplasms / Q000532:radiotherapy*; D008954:Models, Biological; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000706:statistics & numerical data*; D011882:Radiotherapy, High-Energy; D014057:Tomography, X-Ray Computed