Gamma passing rates of daily EPID transit images correlate to PTV coverage for breast cancer IMRT treatment plans.
J Appl Clin Med Phys
; 24(5): e13913, 2023 May.
Article
en En
| MEDLINE
| ID: mdl-36700363
ABSTRACT
PURPOSE:
The use of the transit image obtained with the electronic portal-imaging device (EPID) is becoming an extended method to perform in-vivo dosimetry. The transit images acquired during each fraction can be compared with a predicted image, if available, or with a baseline image, usually the obtained in the first fraction. This work aims to study the dosimetric impact of the failing fractions and to evaluate the appropriateness of using a baseline image in breast plans. MATERIAL ANDMETHODS:
Twenty breast patients treated in a Halcyon were retrospectively selected. For each patient and fraction, the treatment plan was calculated over the daily CBCT image. For each fraction, the differences respect to the treatment plan values of OARs and PTV dosimetric parameters were analyzed ΔDmean , ΔD95%, ΔD98%, ΔD2%, ΔV36Gy, ΔV38.5Gy, and ΔV43.5Gy. Daily fractions were ranked according to the differences found in the dosimetric parameters between the treatment plan and the daily CBCT to establish the best fraction. The daily transit images acquired in every fraction were compared to the first fraction using the global gamma index with the Portal Dosimetry tool. The comparison was repeated using the best fraction image as a baseline. We assessed the correlation of the dosimetric differences obtained from the CBCT images-based treatment plans with the gamma index passing rates obtained using first fraction and best fraction as baseline.RESULTS:
Average values of -11.6% [-21.4%, -3.3%] and -3.2% [-1.0%, -10.3%] for the ∆PTVD98% and ∆PTVD95% per every 10% decrease in the passing rate were found, respectively. When using the best fraction as baseline patients were detected with failing fractions that were not detected with the first fraction as baseline.CONCLUSION:
The gamma passing rates of daily transit images correlate with the coverage loss parameters in breast IMRT plans. Using first fraction image as baseline can lead to the non-detectability of failing fractions.Palabras clave
Texto completo:
1
Banco de datos:
MEDLINE
Asunto principal:
Neoplasias de la Mama
/
Radioterapia de Intensidad Modulada
Tipo de estudio:
Observational_studies
/
Risk_factors_studies
Límite:
Female
/
Humans
Idioma:
En
Año:
2023
Tipo del documento:
Article