Early clinical experience with varian halcyon V2 linear accelerator: Dual‐isocenter IMRT planning and delivery with portal dosimetry for gynecological cancer treatments

Kim, Hayeon; Huq, M. Saiful; Lalonde, R.J.; Houser, Christopher J.; Beriwal, Sushil; Heron, Dwight E.

doi:10.1002/acm2.12747

Cited by 27 publications

(33 citation statements)

References 26 publications

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“…The feasibility of in-vivo portal dosimetry was also demonstrated. 35 The presented study aims at validating the ability to detect deviations between planned and delivered fluences for VMAT and IMRT plans by portal dosimetry measurements acquired at the Halcyon linac.In addition, understanding the system's sensitivity to detect potentially relevant inaccuracies in treatment plan delivery is mandatory for its introduction into clinical routine. With this aim, unmodified VMAT plans spanning the complete clinical spectrum of treatment sites together with a representative set of treatment plans, in which different kinds of intentional errors were built in, were measured with both the portal imager and the ArcCHECK phantom (Sun Nuclear Corporation, Melbourne, FL), 10 a common means for dosimetric pre-treatment QA as reference.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity and specificity of Varian Halcyon's portal dosimetry for plan‐specific pre‐treatment QA

Razinskas

Schindhelm

Sauer

et al. 2023

J Applied Clin Med Phys

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Developed as a plan-specific pre-treatment QA tool, Varian portal dosimetry promises a fast, high-resolution, and integrated QA solution. In this study, the agreement between predicted fluence and measured cumulative portal dose was determined for the first 140 patient plans at our Halcyon linear accelerator. Furthermore, the capability of portal dosimetry to detect incorrect plan delivery was compared to that of a common QA phantom. Finally, tolerance criteria for verification of VMAT plan delivery with Varian portal dosimetry were derived. Methods: All patient plans and the corresponding verification plans were generated within the Eclipse treatment planning system. Four representative plans of different treatment sites (prostate, prostate with lymphatic drainage, rectum, and head & neck) were intentionally altered to model incorrect plan delivery. Investigated errors included both systematic and random errors. Gamma analysis was conducted on both portal dose (criteria γ 2%/2 mm , γ 2%/1 mm , and γ 1%/1 mm ) and ArcCHECK measurements (criteria γ 3%/3 mm , γ 3%/2 mm , and γ 2%/2 mm ) with a 10% low-dose threshold. Performance assessment of various acceptance criteria for plan-specific treatment QA utilized receiver operating characteristic (ROC) analysis. Results: Predicted and acquired portal dosimetry fluences demonstrated a high agreement evident by average gamma passing rates for the clinical patient plans of 99.90%, 96.64%, and 91.87% for γ 2%/2 mm , γ 2%/1 mm , and γ 1%/1 mm , respectively. The ROC analysis demonstrated a very high capability of detecting erroneous plan delivery for portal dosimetry (area under curve (AUC) > 0.98) and in this regard outperforms QA with the ArcCHECK phantom (AUC ≈ 0.82). With the suggested optimum decision thresholds excellent sensitivity and specificity is simultaneously possible. Conclusions: Owing to the high achievable spatial resolution, portal dosimetry at the Halcyon can reliably be deployed as plan-specific pre-treatment QA tool to screen for errors. It is recommended to support the fluence integrated portal dosimetry QA by independent phantom-based measurements of a random sample survey of treatment plans.

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Section: Introductionmentioning

confidence: 99%

Sensitivity and specificity of Varian Halcyon's portal dosimetry for plan‐specific pre‐treatment QA

Razinskas

Schindhelm

Sauer

et al. 2023

J Applied Clin Med Phys

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“…In addition, CBCT generated from the onboard imager system mounted on a linear accelerator suffers from motion artifacts due to very slow gantry rotation speed. The development of enclosed ring gantry for both linac and onboard imager system allows at least four times faster gantry rotation, thus greatly mitigating the motion artifacts especially for anatomical sites with internal patient motion 20–22 …”

Section: Introductionmentioning

confidence: 99%

“…The development of enclosed ring gantry for both linac and onboard imager system allows at least four times faster gantry rotation, thus greatly mitigating the motion artifacts especially for anatomical sites with internal patient motion. [20][21][22] Recent studies on CBCT images obtained from new linac models (Halcyon/Ethos v3.1, Varian Medical Systems, Palo Alto, CA) have shown promising results with improvements in image quality compared to the standard FDK-based CBCT. 13,20,23,24 The new CBCT system has three major improvements, including a faster gantry speed for image acquisition, a high ratio anti-scatter grid enabled by the non-movable ring gantry imaging system for both source and detector for scatter reduction, and a novel iterative reconstruction algorithm combining statistical reconstruction with an advanced edgepreserving noise reduction filter to improve soft-tissue contrast.…”

Section: Introductionmentioning

confidence: 99%

Technical note: Characterization of novel iterative reconstructed cone beam CT images for dose tracking and adaptive radiotherapy on L‐shape linacs

et al. 2022

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Background Cone‐beam computed tomography (CBCT) allows for patient setup and positioning, and potentially dose verification or adaptive replanning prior to each treatment delivery. Poor CBCT image quality due to scatter artifacts and patient motion has been a major limiting factor. A new image reconstruction algorithm was recently clinically implemented for improving image quality through iterative reconstruction (iCBCT). Purpose This study aims to characterize iCBCT image quality, establish image value (HU)‐to‐relative electron density (RED) calibration curves for dose calculation, and assess the dosimetric accuracy for different anatomical sites. Material and methods Both conventional CBCT and iCBCT scans were acquired from a Varian TrueBeam On‐Board Imager system. A Catphan 604 phantom was scanned to compare image quality between the traditional Feldkamp–Davis–Kress (FDK) and novel iterative reconstruction techniques. Computerized Imaging Reference Systems (CIRS) electron density phantom was used to construct site‐specific HU‐RED curves corresponding to various scan settings. The CIRS Dynamic Thorax phantom, Rando pelvis phantom, and BrainLab head phantom were used for assessing dosimetric accuracy calculated on iCBCT images, compared to that on traditional FDK‐based CBCT images. All phantoms were scanned on a computed tomography (CT) to obtain baseline HU values for comparison. Results Test results obtained from Catphan showed statistically significant improvement with iCBCT, compared to FDK CBCT. Average HU differences from the baseline CT values were improved to within ±30 HU for iCBCT, compared to FDK CBCT for phantom studies. Dose calculated on iCBCT for both phantoms and patient cases directly using baseline HU‐RED calibration from CT showed 0.5%–2.0% accuracy from the baseline dose calculated on CT, which is comparable to doses calculated using site‐specific HU‐RED calibration curves. Conclusion iCBCT provides improved image quality, improved HU accuracy compared to CT baseline, and has potential to provide online dose verification as part of the adaptive radiotherapy workflow directly using the baseline HU‐RED calibration curve from CT.

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“…Recent research results report the more aggressive impact of targeted γ-ray irradiation compared to the general one; however, it is important to consider, for example, electron beam therapy, which is widely used nowadays because of its high success rate in the treatment of, for example, gynecological malignancies [ 5 ]. At the same time, the effects of this kind of radiation on spermatogenesis remain unexplored, and this raises a number of questions: whether the apoptotic rate of male gametes is accelerated, on which stages of spermatogenesis they are more likely to be damaged, and for how long these pathomorphological changes persist after electron irradiation.…”

Section: Introductionmentioning

confidence: 99%

Assessment of Proliferation and Apoptosis in Testes of Rats after Experimental Localized Electron Irradiation

Demyashkin

Koryakin

Moiseev

et al. 2022

CIMB

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Background and purpose: With the emergence of linear accelerators in radiotherapy, it becomes necessary to accurately select new dosing regimens. The purpose of this study was to assess the morphological changes of spermatogenesis after radiation exposure. Materials and methods: Male Wistar rats (n = 40) were subjected to targeted ionizing radiation on a pulsed electron accelerator “NOVAC-11” with doses of 2, 8 and 12 Gy. Spermatogenesis was assessed a week later using light microscopy and immunohistochemical method (antibodies to Ki-67, Bcl-2, p53, Caspase 3). Results: A decrease in the number of normal germ cells was seen in all experimental groups, while radioresistant Sertoli and Leydig cells were barely affected. The most serious damage to the tubules and germ cells was observed in 8 and 12 Gy irradiation groups. IHC analysis of testes after irradiation showed a shift in the proliferative-apoptotic balance toward apoptosis of germ cells: a decrease in the expression levels of Ki-67 and Bcl-2, an increase in p53-positive and caspase 3-positive cells by the end of the experiment. Conclusion: Dose-dependent progressive pathomorphological changes in histoarchitectonics of the testes are traced, and a decrease in the number of germ cells is seen on the seventh day after irradiation with a pulsed electron accelerator “NOVAC-11”.

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Early clinical experience with varian halcyon V2 linear accelerator: Dual‐isocenter IMRT planning and delivery with portal dosimetry for gynecological cancer treatments

Cited by 27 publications

References 26 publications

Sensitivity and specificity of Varian Halcyon's portal dosimetry for plan‐specific pre‐treatment QA

Sensitivity and specificity of Varian Halcyon's portal dosimetry for plan‐specific pre‐treatment QA

Technical note: Characterization of novel iterative reconstructed cone beam CT images for dose tracking and adaptive radiotherapy on L‐shape linacs

Assessment of Proliferation and Apoptosis in Testes of Rats after Experimental Localized Electron Irradiation

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