title: Respiratory gated radiotherapy-pretreatment patient specific quality assurance.
abstract: Organ motions during inter-fraction and intra-fraction radiotherapy introduce errors in dose delivery, irradiating excess of normal tissue, and missing target volume. Lung and heart involuntary motions cause above inaccuracies and gated dose delivery try to overcome above effects. Present work attempts a novel method to verify dynamic dose delivery using a four-dimensional (4D) phantom. Three patients with mobile target are coached to maintain regular and reproducible breathing pattern. Appropriate intensity projection image set generated from 4D-computed tomography (4D-CT) is used for target delineation. Intensity modulated radiotherapy plans were generated on selected phase using CT simulator (Siemens AG, Germany) in conjunction with "Real-time position management" (Varian, USA) to acquire 4D-CT images. Verification plans were generated for both ion chamber and Gafchromic (EBT) film image sets. Gated verification plans were delivered on the phantom moving with patient respiratory pattern. We developed a MATLAB-based software to generate maximum intensity projection, minimum intensity projections, and average intensity projections, also a program to convert patient breathing pattern to phantom compatible format. Dynamic thorax quality assurance (QA) phantom (Computerized Imaging Reference Systems type) is used to perform the patient specific QA, which holds an ion chamber and film to measure delivered radiation intensity. Exposed EBT films are analyzed and compared with treatment planning system calculated dose. The ion chamber measured dose shows good agreement with planned dose within ± 0.5% (0.203 ± 0.57%). Gamma value evaluated from EBT film shows passing rates 92-99% (96.63 ± 3.84%) for 3% dose and 3 mm distance criteria. Respiratory gated treatment delivery accuracy is found to be within clinically acceptable level.
authors.affiliation: Division of Radiation Oncology, Medanta Cancer Institute, Medanta - The Medicity, Gurgaon, Haryana, India.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Thiyagarajan
authors.affiliation: Department of Radiation Oncology, Nayati Healthcare and Research, Mathura, India.
authors.forename: Sujit Nath
authors.initials: SN
authors.lastname: Sinha
authors.affiliation: Department of Radiation Oncology, Royal Hospital, Muscat, Sultanate of Oman.
authors.forename: Ramamoorthy
authors.initials: R
authors.lastname: Ravichandran
authors.affiliation: Division of Medical Physics, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India.
authors.forename: Kothandaraman
authors.initials: K
authors.lastname: Samuvel
authors.affiliation: Division of Medical Physics, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India.
authors.forename: Girigesh
authors.initials: G
authors.lastname: Yadav
authors.affiliation: Department of Medical Physics, Kuwait Cancer Control Centre, Shuwaikh, Kuwait.
authors.forename: Ashok Kumar
authors.initials: AK
authors.lastname: Sigamani
authors.affiliation: Division of Radiation Oncology, Medanta Cancer Institute, Medanta - The Medicity, Gurgaon, Haryana, India.
authors.forename: Vikraman
authors.initials: V
authors.lastname: Subramani
authors.affiliation: Department of Physics, School of Advanced Sciences, VIT University, Vellore, Tamil Nadu, India.
authors.forename: N Arunai Nambi
authors.initials: NA
authors.lastname: Raj
keywords: Gated dose delivery; pretreatment quality assurance; respiratory gating; three-dimensional imaging