scholarly journals Rebuild-up Effect on Superficial Cardiac Lesion Surrounded by Low-density Lungs: Volumetric Modulated Arc Therapy (VMAT) Planning Study Using 3-D Printed Phantom for Ventricular Tachycardia (VT)

2021 ◽  
Author(s):  
Si-Won No ◽  
Jun-Bong Shin ◽  
Yong-Ki Bae ◽  
Jungmin Kim ◽  
Semie Hong ◽  
...  
Keyword(s):  
Ventricular Tachycardia ◽  
Volumetric Modulated Arc Therapy ◽  
Low Density ◽  
Film Dosimetry ◽  
Palo Alto ◽  
Photon Beams ◽  
Dose Distributions ◽  
Cardiac Lesion ◽  
Cardiac Phantom ◽  
Arc Therapy

Abstract The study aimed to evaluate dose distributions on the superficial cardiac lesion surrounded by low-density lungs. We fabricated the 3-D printed cardiac phantom to insert in a multipurpose lungman phantom (KYOTO KAGAKU, Japan) for simulating a stereotactic body radiation therapy (SBRT) in ventricular tachycardia (VT) treatment. The cardiac phantom consists of 11 slabs with 1-cm intervals and is designed to insert radiochromic film (Gafchromic EBT3, Ashland Advanced Materials, Bridgewater, NJ) for film dosimetry. We used film dosimetry scanners (DosimetryPRO Advantage Red, Vidar Systems Corporation, Herndon, VA) with dedicated film dosimetry software (OP-IMRT, ver.1.6, IBA dosimetry, Germany). Volumetric modulated arc therapy (VMAT) technique was applied to optimize the dose distribution using the anisotropic analytic algorithm (AAA) in a radiation treatment planning (RTP) system (Eclipse v. 13.6, Varian, Palo Alto, CA). We used the 6-MV and 15-MV photon energies from a LINAC (Clinac iX, Varian, Palo Alto, CA) to investigate the planning target volume (PTV) under-dose effects due to the inner dose rebuild-up by energy dependence. The dose distributions in the VMAT plans with 6-MV and 15-MV showed good competitive coverages of the cardiac lesion without any severe underdose pattern. On the other side, the film dosimetry results showed significant dose variations near the interface of the cardiac lesion surrounded by low-density lung. The differences between the planning and the film dosimetry results revealed pretty well in both photon energies. The maximum dose differences in the cardiac PTV were ranged from 4.1–7.7% and 4.1–8.1% for 6-MV photon beams and 15-MV photon beams. Furthermore, EBT3 film measurements showed that the widths of 50% of profiles were reduced by 1.3 cm and 2.3 cm on 6-MV photon beams and 15-MV photon beams, respectively. In addition, 3-D printing techniques enabled quite challengeable dose measurements to reveal this kind of dose discrepancies in humanoid structures. This study showed that clinical cases like VT SBRT surrounded by severe inhomogeneous matter could induce wrongly to estimate appropriate dose delivery and to evaluate reasonable clinical outcomes.

Volumetric modulated arc therapy planning based on virtual monochromatic images: Effect of inaccurate CT numbers on dose distributions

2019 ◽  
Vol 60 ◽  
pp. 83-90 ◽  
Author(s):  
Shingo Ohira ◽  
Riho Komiyama ◽  
Tsukasa Karino ◽  
Hayate Washio ◽  
Yoshihiro Ueda ◽  
...  
Keyword(s):  
Volumetric Modulated Arc Therapy ◽  
Therapy Planning ◽  
Dose Distributions ◽  
Arc Therapy

scholarly journals Considerations for the verification of volumetric modulated arc therapy-planned dose distributions

2019 ◽  
Vol 3 ◽  
Author(s):  
Lourens Strauss ◽  
William Shaw
Keyword(s):  
Error Detection ◽  
Volumetric Modulated Arc Therapy ◽  
Standard Of Care ◽  
Target Volume ◽  
Pass Rates ◽  
Dose Distributions ◽  
Dose Volume ◽  
Multi Leaf Collimator ◽  
Arc Therapy ◽  
Verification Systems

Background: Volumetric modulated arc therapy (VMAT) is the standard of care for many clinical indications, but should only be considered with proper technical support and quality assurance (QA) in place. Despite the high accuracy of VMAT systems, errors can be present and adequate verification is required. Dosimetric VMAT verification systems have a broadly similar analysis philosophy. However, many factors influence the analyses and the subsequent QA outcome, based on which the plan will pass or fail.Aim: This study investigated various factors that influence the dosimetric impact and detectability of known linac component deviations on VMAT QA, including geometries, tissue densities, gamma criteria and dose–volume differences.Setting: Universitas Hospital (Annex), Bloemfontein, South Africa.Methods: Deliberate multi-leaf collimator (MLC)-bank offsets were introduced on four different VMAT plans of the prostate, nasopharynx and brain. Measured reference dose sets were compared to measured QA results, using the IBA Dolphin© detector and Compass© software for three dosimetric scenarios. Gamma pass rates over a range of criteria from 1%/2-mm to 4%/4-mm in the total volumes and per structure, as well as dose–volume differences were studied.Results: Gamma tests in the total patient/phantom did not sufficiently detect errors. The calculation media did not influence the QA outcome greatly. However, the detection geometry affected the results. Per structure gamma analyses provided superior error detection, although still missed some clinically relevant differences. The addition of dose–volume analyses highlighted several important errors.Conclusion: Volumetric modulated arc therapy using only total volume gamma analyses can easily overlook clinically relevant errors. The choice of gamma criterion is crucial. Verification with at least a per structure gamma test in combination with dose–volume checks is recommended, especially in small target volume cases.

The sensitivity of gamma index analysis to detect multileaf collimator (MLC) positioning errors using Varian TrueBeam EPID and ArcCHECK for patient-specific prostate volumetric-modulated arc therapy (VMAT) quality assurance

2017 ◽  
Vol 17 (1) ◽  
pp. 66-77 ◽  
Author(s):  
Borna Maraghechi ◽  
Jack Davis ◽  
Nicholas Mitchell ◽  
Meeral Shah ◽  
Andre Fleck ◽  
...  
Keyword(s):  
Volumetric Modulated Arc Therapy ◽  
Patient Specific ◽  
Multileaf Collimator ◽  
Control Points ◽  
Dose Distributions ◽  
Positioning Errors ◽  
Gamma Index ◽  
Arc Therapy ◽  
Epid Dosimetry ◽  
Higher Sensitivity

AbstractBackgroundDue to the increased degree of modulation and complexity of volumetric-modulated arc therapy (VMAT) plans, it is necessary to have a pre-treatment patient-specific quality assurance (QA) programme. The gamma index is commonly used to quantitatively compare two dose distributions. In this study we investigated the sensitivity of single- and multi-gamma criteria techniques to detect multileaf collimator (MLC) positioning errors using the Varian TrueBeam Electronic Portal Imaging DeviceTM (EPID) dosimetry and the ArcCHECKTM device.Materials and methodsAll active MLC positions of seven intact prostate patients VMAT plans were randomly changed with a mean value of 0.25, 0.5, 1 and 2 mm and a standard deviation of 0.1 mm on 25, 50, 75 and 100% of the control points. The change in gamma passing rates of six gamma criteria of 3%/3 mm, 3%/2 mm, 3%/1 mm, 2%/2 mm, 2%/1 mm and 1%/1 mm were analysed individually (single-gamma criterion) and as a group (multi-gamma criteria) as a function of the simulated errors. We used the improved and global gamma calculation algorithms with a low dose threshold of 10% in the EPID and ArcCHECK software, respectively. The changes in the planning target volume dose distributions and the organs at risk due to the MLC positioning errors were also studied.ResultsWhen 25, 50, 75 and 100% of the control points were modified by the introduction of the simulated errors, the smallest detectable errors with the EPID were 2, 1, 0.5 and 0.5 mm, respectively, using the multi-gamma criteria technique. Similarly for the single-gamma criteria technique errors as small as 2, 1, 1 and 1 mm applied to 25, 50, 75 and 100% of the control points, respectively, were detectable using a 2%/2 mm criterion. However, the smallest detectable errors with the ArcCHECK when using the multi-gamma criteria technique were 2, 2 and 1 mm when MLC errors were applied on 50, 75 and 100% of the control points. When only 25% of the control points were affected the ArcCHECK were unable to detect any of the errors applied. No noticeable difference was observed in the sensitivity using the single- or the multi-gamma criteria techniques with the ArcCHECK.ConclusionThe Varian TrueBeam EPID dosimetry shows a higher sensitivity in detecting MLC positioning errors compared with the ArcCHECK regardless of using the single- or the multi-gamma criteria techniques. Higher sensitivity was observed using the multi-gamma criteria technique compared with the single-criterion technique when using the EPID.

scholarly journals Three-dimensional radiochromic film dosimetry for volumetric modulated arc therapy using a spiral water phantom

2013 ◽  
Vol 54 (6) ◽  
pp. 1153-1159 ◽  
Author(s):  
M. Tanooka ◽  
H. Doi ◽  
H. Miura ◽  
H. Inoue ◽  
Y. Niwa ◽  
...  
Keyword(s):  
Volumetric Modulated Arc Therapy ◽  
Three Dimensional ◽  
Radiochromic Film ◽  
Film Dosimetry ◽  
Water Phantom ◽  
Arc Therapy

scholarly journals Time-resolved dose distributions to moving targets during volumetric modulated arc therapy with and without dynamic MLC tracking

2013 ◽  
Vol 40 (11) ◽  
pp. 111723 ◽  
Author(s):  
Thomas Ravkilde ◽  
Paul J. Keall ◽  
Cai Grau ◽  
Morten Høyer ◽  
Per R. Poulsen
Keyword(s):  
Volumetric Modulated Arc Therapy ◽  
Moving Targets ◽  
Dose Distributions ◽  
Time Resolved ◽  
Arc Therapy
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