Rapid acceptance testing of modern linac using on-board MV and kV imaging systems

Yaddanapudi, S; Cai, Bin; Harry, Taylor; Dolly, S; Sun, Baozhou; Li, Hua; Stinson, Keith; Noël, C.; Santanam, Lakshmi; Pawlicki, Todd; Mutic, Sasa; Goddu, S

doi:10.1002/mp.12294

Cited by 17 publications

(41 citation statements)

References 41 publications

(89 reference statements)

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“…Linacs that included amorphous silicon (aS1000) EPIDs were used in this study (TrueBeam, Varian Medical Systems, Palo Alto, CA, USA). Work exploring the use of the onboard electronic portal imaging device (EPID) for expediting the conventional linac ATP (ATP conv ) has been completed . Using the EPID with a newly designed phantom; a series of Extensible Markup Language (XML) files are generated to automate the ATP conv tests and optimize the setup and steps for various ATP tests.…”

Section: Methodsmentioning

confidence: 99%

Risk assessment of a new acceptance testing procedure for conventional linear accelerators

et al. 2017

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Section: Methodsmentioning

confidence: 99%

Risk assessment of a new acceptance testing procedure for conventional linear accelerators

et al. 2017

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“…More recently, film has been widely replaced with onboard x‐ray‐based imaging panels such as electronic portal imaging devices (EPID) for C‐arm linacs and parallel plate CT detectors for helical‐based systems . These arrays have proven to be robust, efficient, and sensitive tools for MLC QA by measuring x‐ray fluence profiles .…”

Section: Introductionmentioning

confidence: 99%

Characterization of positional accuracy of a double‐focused and double‐stack multileaf collimator on an MR‐guided radiotherapy (MRgRT) Linac using an IC‐profiler array

et al. 2019

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Purpose With advance magnetic resonance (MR)‐guided online adaptive radiotherapy (MRgoART) relying on calculation‐based intensity‐modulated radiation therapy (IMRT) quality assurance (QA), accurate and sensitive QA of the multileaf collimator (MLC) becomes an increasingly essential component for routine machine QA. As such, it is important to assure compliance with the AAPM TG142 guidelines to supplement calculation‐based QA methods for an online adaptive radiotherapy program. We have developed and implemented an efficient and highly sensitive QA procedure using an ionization chamber profiler (ICP) array to enable real‐time characterization of the positional accuracy of a double‐focused and double‐stacked MLC on a clinical MR‐guided radiotherapy (MRgRT) system and to supplement calculation‐based QA for an MRgoART program. Methods An in‐house MR‐compatible jig was used to position the ICP (detector resolution 5 mm on X/Y axis) at an extended SDD of 108.4 cm to enable each MLC leaf (8.3 mm leaf width at isocenter) to be uniquely determined by two neighboring ion chambers. The MRgRT linac system utilizes a novel jawless, double‐focused, and double‐stacked MLC design such that the upper bank (MLC1) and lower bank (MLC2) are offset by half a leaf width. Positional accuracy was characterized by three methods: single bank half‐beam block (HBB) at central axis, forward slash diagonal (FSD), and backslash diagonal (BSD) at off‐axis. Measurements were performed for each bank in which each leaf occludes half of a detector. A corresponding reference field with the MLC retracted from occlusion was measured. The sensitivities of HBB, FSD, and BSD were evaluated by introducing 0.5–2.5 mm of known errors in 0.5 mm increments, in both positive and negative directions. The relationship between detector response and MLC error was established. Over a 6‐month longitudinal assessment, we have evaluated MLC performance with weekly QA of HBB among cardinal angles, and monthly QA of FSD and BSD. Results A strong correlation was found between detector response of percentage dose difference and MLC positional error introduced (N = 350 introduced errors) for both HBB and FSD/BSD with coefficient of determination of 0.999 and 0.977, respectively. The relationship between detector response to MLC positional change was found to be 20.65%/mm for HBB and 11.14%/mm for FSD and BSD. At baseline, the mean MLC positional accuracy averaged across all leaves was 0.06 ± 0.27 mm (HBB), 0.04 ± 0.52 mm (FSD), −0.06 ± 0.51 mm (BSD). The mean MLC positional accuracy relative to baseline over the 6‐month assessment was found to be highly reproducible at 0.00 ± 0.12 mm (HBB; N = 28 weeks), −0.02 ± 0.19 mm (FSD; N = 6 months), −0.03 ± 0.19 mm (BSD; N = 6 months). Conclusions Positional accuracy of a novel jawless, double‐focused, double‐stacked MLC has been characterized and monitored over 6 months with an efficient, highly sensitive, and robust method using an ICP array. This routine QA method supplements calculation‐based IMRT QA for an online adaptive radio...

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“…The methods presented have all been modified specific to this new application. Specifically, the work of Yaddanapudi et al 9. provides a method of checking photon beam symmetry using PSM‐corrected EPID images for linac acceptance testing purposes and the work of Bin Cai et al 10.…”

Section: Introductionmentioning

confidence: 99%

A proposed method for linear accelerator photon beam steering usingEPID

Barnes

Menk

Lamichhane

et al. 2018

J Applied Clin Med Phys

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Beam steering is the process of calibrating the angle and translational position with which a linear accelerator's (linac's) electron beam strikes the x‐ray target with respect to the collimator rotation axis. The shape of the dose profile is highly dependent on accurate beam steering and is essential for ensuring correct delivery of the radiotherapy treatment plan. Traditional methods of beam steering utilize a scanning water tank phantom that makes the process user‐dependent. This study is the first to provide a methodology for both beam angle steering and beam translational position steering based on EPID imaging of the beam and does not require a phantom. Both the EPID‐based beam angle steering and beam translational steering methods described have been validated against IC Profiler measurement. Wide field symmetry agreement was found between the EPID and IC Profiler to within 0.06 ± 0.14% (1 SD) and 0.32 ± 0.11% (1 SD) for flattened and flattening‐filter‐free (FFF) beams, respectively. For a 1.1% change in symmetry measured by IC Profiler the EPID method agreed to within 0.23%. For beam translational position steering, the EPID method agreed with IC Profiler method to within 0.03 ± 0.05 mm (1 SD) at isocenter. The EPID‐based methods presented are quick to perform, simple, accurate and could easily be integrated with the linac, potentially via the MPC application. The methods have the potential to remove user variability and to standardize the process of beam steering throughout the radiotherapy community.

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Rapid acceptance testing of modern linac using on-board MV and kV imaging systems

Cited by 17 publications

References 41 publications

Risk assessment of a new acceptance testing procedure for conventional linear accelerators

Risk assessment of a new acceptance testing procedure for conventional linear accelerators

Characterization of positional accuracy of a double‐focused and double‐stack multileaf collimator on an MR‐guided radiotherapy (MRgRT) Linac using an IC‐profiler array

A proposed method for linear accelerator photon beam steering usingEPID

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