Effect of replacing cochlea contour with inner ear contour on cochlea dose-volume calculations in conventional ۲ dimensional and conformal ۳ dimensional radiotherapy of brain

Introduction: Sensorineural hearing loss (SNHL) is one of the possible complications of radiotherapy treatment of brain tumors. The auditory system of patients with brain tumors often is placed inside of radiation field and receives a significant amount of radiation dose resulting in hearing loss. The purpose of this study was to compare contouring and delivery dose to cochlea and inner ear in two techniques of ۳D conformal radiotherapy (۳DCRT) vs ۲D conventional radiotherapy in patients with brain tumors Materials and Methods: This was a prospective study. Forty-three patients (۲۳male and ۲۰ female) who received radiotherapy for brain tumors in the radiation oncology department of Isfahan Milad Hospital during ۲۰۱۶ entered the study. Computerized tomography (CT) images of the patients were used for contouring of cochlea and inner ear by radiation oncologist. Dose Volume Histograms (DVHs) for ۲D and ۳D techniques were compared using TiGRT treatment planning system. Results: In ۲D technique the mean dose of the cochlea and inner ear was ۲۶۲۴ ± ۳۳۸.۷(cGy) and ۲۷۱۸.۳ ± ۳۴۱.۳(cGy), respectively. In ۳DCRT technique the mean dose of the cochlea and inner ear was ۲۵۰۷±۲۹۴.۶(cGy) and ۲۵۸۱± ۲۹۵.۶(cGy), respectively. The mean dose of inner ear and cochlea in ۳DCRTmethod was %۵.۳ and %۴.۶ lower than ۲D, respectively Conclusion: The study of dosimetric parameters of the auditory system in treatment planning of two methods of radiation therapy showed that there was no significant difference between the doses of cochlea and inner ear in ۲D and ۳D methods ( Pvalues=۰.۸۶,۰.۸۵).Therefore in treatment planning of these two radiotherapy techniques, contour of cochlea can be replaced by inner ear.

کلیدواژه ها:

Contouring ، Cochlea ، Inner ear ، ۲D and ۳D dimensional radiotherapy ، brain tumor