An Investigation into the Couch Coefficient Accuracy of Exact IGRT Couch with Eclipse Treatment Planning System in Vital Beam Varian Linear Accelerator

Authors

  • Mahya Badrasa Department of Medical Physics, Faculty of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
  • Mojan Mobaraki Department of Medical Physics, Faculty of Medicine, International Campus, Shahid Sadoughi University of Medical Sciences and Health Services, Yazd, Iran
  • Abolfazl Nickfarjam Department of Medical Physics, Faculty of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
  • Mohammad Hasan Larizadeh Department of Radiation Oncology, Afzalipour Radiation Oncology Center, Kerman University of Medical Sciences, Kerman, Iran
  • Nasim Namiranian Yazd Diabetes Research Center, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
  • Nima Hamzian Department of Medical Physics, Faculty of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran

DOI:

https://doi.org/10.18502/fbt.v13i3.22740

Keywords:

Radiotherapy Treatment Couch; Exact Image-Guided Radiation Therapy Couch; Attenuation; Eclipse Treatment Planning System.

Abstract

Purpose: Posterior oblique beams are increasingly common in radiotherapy techniques. Radiation beams traversing through the treatment couch would be attenuated and cause under-dosage in the tumor region. The attenuation of an IGRT carbon fiber Couch for different angles, energies, field sizes, measurement points, couch regions, and the ability of the Eclipse treatment planning system to predict doses were investigated.

Materials and Methods: The Varian Vital Beam linear accelerator (Varian Medical Systems) and the Exact IGRT couch top, a new device for patient positioning, were utilized. The couch coefficient was calculated using in-air gantry angle measurements to determine the most attenuation angle. the attenuation measurements were performed in three measurement points of an inhomogeneous PMMA phantom using a farmer ionization chamber for three energies with six field sizes in three regions of an IGRT couch at the most attenuation gantry angle.

Results: The results of the couch coefficient measurements demonstrated that in three regions of the IGRT couch at an angle of 130˚, the photon beam was most attenuated. The difference between the calculated dose by the Eclipse treatment planning system and the experimental dose measurements was 1.855%. The difference is less than 3% and the attenuation was within the allowable range for treatment.

Conclusion: The IGRT treatment couch in posterior oblique gantry angles decreased the dose in the measurement points due to gantry angle, field size, energy, and couch region. The Eclipse treatment planning system can sufficiently predict the tumor dose distribution.

Published

2026-09-22

Issue

Volume (13) issue (3)

Section

Articles