Is the dose distribution distorted in IMRT and RapidArc treatment when patient plans are swapped across beam‐matched machines?

Krishnappan, C.; Radha, C. Anu; Subramani, Vendhan; Gunasekaran, Madhan Kumar

doi:10.1120/jacmp.v17i5.6104

Cited by 3 publications

(2 citation statements)

References 12 publications

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“…The criteria used for the beam matching acceptance were based on the suitability of dose percentage graph in-depth and radiation beam profile [12]. The evaluated dosimetry beam data of the beam-matched LINACs show their similar dosimetry characteristics.…”

Section: Discussionmentioning

confidence: 99%

Implementation of Beam Matching Concept for the New Installed Elekta Precise Treatment System Medical LINACs in Indonesia

Firmansyah

Sunaryati

et al. 2021

Atom Indo.

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A concept of radiation beam matching of some medical linear accelerators (LINACs) that have identical characteristics of the models, radiation quality, and multileaf collimator features may be implemented as long as the manufacturer provides complete specifications so that a Treatment Planning System (TPS) can be used for many beam-matched LINACs. This paper describes a preliminary study on the implementation of the beam matching concept for five units Elekta Precise Treatment System LINACs that have recently been installed in Indonesia. The beam matching criteria were based on the percentage depth dose (PDD) and beam profile for photon and electron beams. Dosimetry measurements were carried out by using an SNC 125 ionization chamber of 0.125 cm 3 in volume, PTW Pinpoint 3D of 0.016 cm 3 in volume, and PTW Farmer Chamber of 0.6 cm 3 in volume. The results indicated that the PDD 10 of 6 and 10 MV photon beams among installed five units LINACs have excellent compatibility each others with a maximum deviation of less than 0.4 %, while the maximum deviation for dose depth of 80 % (R 80 ) for the electron beams with nominal energies of 4, 6, 8, 10, 15 and 18 MeV is 1 mm. The measurement results for the flatness profile were less than 6 %, and symmetry profiles were less than 3 %. It also outlines the determination of the absorbed dose to water under reference conditions. The results of the calibration of output doses show that the absorbed dose in the water was 1 cGy ≈ 1 MU. The data obtained from measurements for each LINAC conform with the requirements of the beam matching process set by the manufacturer.

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Section: Discussionmentioning

confidence: 99%

Implementation of Beam Matching Concept for the New Installed Elekta Precise Treatment System Medical LINACs in Indonesia

Firmansyah

Sunaryati

et al. 2021

Atom Indo.

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“…Dosimetric Leaf Gap (DLG) is a key parameter in matching linacs, most importantly for dynamic treatments 5,7,19 . Dosimetric Leaf Gap calibration require submillimeter precision and having many linacs to be matched in a clinic require optimizing the DLG value so it can be achieved within a certain tolerance by all linacs.…”

Section: Methodsmentioning

confidence: 99%

Dosimetric and mechanical equivalency of Varian TrueBeam linear accelerators

Ghazal

Södergren

Westermark

et al. 2020

J Applied Clin Med Phys

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To investigate and improve the level of equivalency of Varian TrueBeam linear accelerators (linacs) in energy-, dosimetric leaf gap-(DLG) and jaw calibration. Methods: Eight linacs with four photon energies: 6 MV, 6 MV FFF, 10 MV FFF, and 15 MV, and three electron energies (on two linacs): 6, 9, and 12 MeV were commisioned and beam-matched. Initially, symmetry of lateral profiles was calibrated for maximum field size. Energy-matching was then performed for photons by adjusting diagonal profiles at maximum field size and depth of maximum dose to coincide with the reference linac, and for electrons by matching the range at percentage depth of ionization of 90%, 80%, and 50%. Calibration of DLG was performed for 6 MV and evaluated among the linacs. The relationship between DLG and the Gap value was investigated. A method using electronic portal imaging device (EPID) was developed and implemented for jaw calibration. Results: Symmetry calibration for photons (electrons) was within 1% (0.7%), further improving the vendor's acceptance criteria. Photon and electron energy-matching was within 0.5% and 0.1 mm, respectively. Calibration of DLG was within 0.032 mm among the linacs and utilizing the relationship between DLG and the Gap value resulted in an empirical calibration method which was implemented to simplify DLG adjustment. Using EPID-based method of calibration, evaluation of the jaw-positioning among the linacs for 30 cm × 30 cm field size was within 0.4 mm and in the junction area within 0.2 mm. Dose delivery error of VMAT-plans were at least 99.2% gamma pass rate (1%, 1 mm). Conclusions: High level of equivalency, beyond clinically accepted criteria, of True-Beam linacs could be achieved which reduced dose delivery systematic errors and increased confidence in interchanging patients among linacs.

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