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Article ; Online: Stereotactic radiotherapy of intracranial tumor beds on a ring-mounted Halcyon LINAC.

Misa, Joshua / McCarthy, Shane / Clair, William St / Pokhrel, Damodar

Journal of applied clinical medical physics

2024 , Page(s) e14281

Abstract: Purpose: This study sought to evaluate the feasibility and efficacy of the Halcyon Ring Delivery System (RDS) for delivering stereotactic radiotherapy (SRT) treatments for intracranial tumors beds.: Methods: Ten previously treated brain SRT patients ... ...

Abstract	Purpose: This study sought to evaluate the feasibility and efficacy of the Halcyon Ring Delivery System (RDS) for delivering stereotactic radiotherapy (SRT) treatments for intracranial tumors beds. Methods: Ten previously treated brain SRT patients for 30 Gy in five fractions with non-coplanar HyperArc plans on TrueBeam (6MV-FFF) were replanned on Halcyon (6MV-FFF) using the same number of arcs and Eclipse's AcurosXB dose engine. Plan quality evaluation metrics per SRT protocol included: PTV coverage, GTV dose (minimum and mean), target conformity indices (CI), heterogeneity index (HI), gradient index (GI), maximum dose 2 cm away from the PTV (D Results: The Halcyon RDS provided highly conformal SRT plans for intracranial tumor beds with similar dose to target. When benchmarked against clinically delivered HyperArc plans, target coverage, CI(s) and HI were statistically similar. The Halcyon plans saw no statistical difference in maximum OAR doses to the brainstem, spinal cord, and cochlea. Due to the machine's coplanar geometry, the Halcyon plans showed a decrease in optic pathway dose (0.75 Gy vs. 2.08 Gy, p = 0.029). Overall, Halcyon's coplanar geometry resulted in a larger GI (3.33 vs. 2.72, p = 0.008) and a larger D Conclusions: When benchmarked against clinically delivered HyperArc treatments, the Halcyon brain SRT plans provided similar plan quality and delivery accuracy but achieved faster overall treatment times. We have started treating select brain SRT patients on the Halcyon RDS for patients having tumor beds greater than 1 cm in diameter with the closest OAR distance of greater than 2 cm away from the target. We recommend other clinics to consider commissioning SRT treatments on their Halcyon systems-allowing including remote Halcyon-only clinics to provide exceptionally high-quality therapeutic brain SRT treatments to an otherwise underserved patient cohort.
Language	English
Publishing date	2024-01-26
Publishing country	United States
Document type	Journal Article
ZDB-ID	2010347-5
ISSN	1526-9914 ; 1526-9914
ISSN (online)	1526-9914
ISSN	1526-9914
DOI	10.1002/acm2.14281
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Article ; Online: The spatial accuracy of ring-mounted halcyon linac versus C-arm TrueBeam linac for single-isocenter/multi-target SBRT treatment.

Pokhrel, Damodar / Mallory, Richard / Bernard, Mark E

Medical dosimetry : official journal of the American Association of Medical Dosimetrists

2023 Volume 48, Issue 3, Page(s) 170–175

Abstract: Stereotactic body radiotherapy (SBRT) treatment of oligometastatic lesions via single-isocenter/multi-target (SIMT) plan is more efficient than using multi-isocenter/multitarget SBRT. This study quantifies the spatial positioning accuracy of 2 ... ...

Abstract	Stereotactic body radiotherapy (SBRT) treatment of oligometastatic lesions via single-isocenter/multi-target (SIMT) plan is more efficient than using multi-isocenter/multitarget SBRT. This study quantifies the spatial positioning accuracy of 2 commercially available LINAC systems for SIMT treatment pertaining to the potential amplification of error as a function of the target's distance-to-isocenter. We compare the Ring-Gantry Halcyon LINAC equipped with the fast iterative conebeam-CT (iCBCT) for image-guided SIMT treatment, and the SBRT-dedicated C-Arm TrueBeam with standard pretreatment CBCT imaging. For both systems, Sun Nuclear's MultiMet Winston-Lutz Cube phantom with 6 metallic BBs distributed at different planes up to 7 cm away from the isocenter was used. The phantom was aligned and imaged via CBCT, and then couch corrections were applied. To treat all 6 BBs, an Eclipse 10-field 3D-conformal Field-in-Field (2×2 cm
Language	English
Publishing date	2023-04-13
Publishing country	United States
Document type	Journal Article
ZDB-ID	645065-9
ISSN	1873-4022 ; 0958-3947 ; 0739-0211
ISSN (online)	1873-4022
ISSN	0958-3947 ; 0739-0211
DOI	10.1016/j.meddos.2023.03.005
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Article ; Online: Letter to the Editor: In Response to Sarkar et al.

Pokhrel, Damodar / Visak, Justin

Journal of applied clinical medical physics

2021 Volume 22, Issue 6, Page(s) 283–285

MeSH term(s)	Humans ; Lung ; Particle Accelerators ; Radiosurgery ; Radiotherapy Dosage
Language	English
Publishing date	2021-05-27
Publishing country	United States
Document type	Letter ; Comment
ZDB-ID	2010347-5
ISSN	1526-9914 ; 1526-9914
ISSN (online)	1526-9914
ISSN	1526-9914
DOI	10.1002/acm2.13277
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Article ; Online: How much rotational error is clinically acceptable for single-isocenter/two-lesion lung SBRT treatment on halcyon ring delivery system (RDS)?

Pokhrel, Damodar / Mallory, Richard / Bernard, Mark E / Kudrimoti, Mahesh

Journal of applied clinical medical physics

2023 Volume 24, Issue 7, Page(s) e14068

Abstract: Purpose: SBRT treatment of two separate lung lesions via single-isocenter/multi-target (SIMT) plan on Halcyon RDS could improve patient comfort, compliance, patient throughput, and clinic efficiency. However, aligning two separate lung lesions ... ...

Abstract	Purpose: SBRT treatment of two separate lung lesions via single-isocenter/multi-target (SIMT) plan on Halcyon RDS could improve patient comfort, compliance, patient throughput, and clinic efficiency. However, aligning two separate lung lesions synchronously via a single pre-treatment CBCT scan on Halcyon can be difficult due to rotational patient setup errors. Thus, to quantify the dosimetric impact, we simulated loss of target(s) coverage due to small, yet clinically observable rotational patient setup errors on Halcyon for SIMT treatments. Methods: Seventeen previously treated 4D-CT based SIMT lung SBRT patients with two separate lesions (total 34 lesions, 50 Gy in five fractions to each lesion) on TrueBeam (6MV-FFF) were re-planned on Halcyon (6MV-FFF) using a similar arc geometry (except couch rotation), dose engine (AcurosXB algorithm), and treatment planning objectives. Rotational patient setup errors of [± 0.5⁰ to ± 3.0⁰] on Halcyon were simulated via Velocity registration software in all three rotation axes and recalculated dose distributions in Eclipse treatment planning system. Dosimetric impact of rotational errors was evaluated for target coverage and organs at risk (OAR). Results: Average PTV volume and distance to isocenter were 23.7 cc and 6.1 cm. Average change in Paddick's conformity indexes were less than -5%, -10%, and -15% for 1°, 2°, and 3°, respectively for yaw, roll, and pitch rotation directions. Maximum drop off of PTV(D100%) coverage for 2° rotation was -2.0% (yaw), -2.2% (roll), and -2.5% (pitch). With ±1° rotational error, no PTV(D100%) loss was found. Due to anatomical complexity: irregular and highly variable tumor sizes and locations, highly heterogenous dose distribution, and steep dose gradient, no trend for loss of target(s) coverage as a function of distance to isocenter and PTV size was found. Change in maximum dose to OAR were acceptable per NRG-BR001 within ±1.0° rotation, but were up to 5 Gy higher to heart with 2° in the pitch rotation axis. Conclusion: Our clinically realistic simulation results show that rotational patient setup errors up to 1.0° in any rotation axis could be acceptable for selected two separate lung lesions SBRT patients on Halcyon. Multivariable data analysis in large cohort is ongoing to fully characterize Halcyon RDS for synchronous SIMT lung SBRT.
MeSH term(s)	Humans ; Radiosurgery/methods ; Radiotherapy Planning, Computer-Assisted/methods ; Radiotherapy Dosage ; Radiotherapy, Intensity-Modulated/methods ; Retrospective Studies ; Lung Neoplasms/radiotherapy ; Lung Neoplasms/surgery ; Lung Neoplasms/pathology ; Lung/pathology
Language	English
Publishing date	2023-06-13
Publishing country	United States
Document type	Journal Article
ZDB-ID	2010347-5
ISSN	1526-9914 ; 1526-9914
ISSN (online)	1526-9914
ISSN	1526-9914
DOI	10.1002/acm2.14068
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Article: Development and Quality Assurance of Multileaf Collimator (MLC) Auto-Feathering Junctions for Multi-Isocenter Supine Volumetric Modulated Arc Therapy (VMAT) Craniospinal Axis Irradiation on Halcyon.

Misa, Joshua / McCarthy, Shane / St Clair, William / Pokhrel, Damodar

Cureus

2023 Volume 15, Issue 9, Page(s) e45640

Abstract: Currently, there is a lack of methods and tools that efficiently evaluate the auto-feathering junctions created by multileaf collimator (MLCs) for supine volumetric modulated arc therapy (VMAT) craniospinal irradiation (CSI) plans. We have investigated ... ...

Abstract	Currently, there is a lack of methods and tools that efficiently evaluate the auto-feathering junctions created by multileaf collimator (MLCs) for supine volumetric modulated arc therapy (VMAT) craniospinal irradiation (CSI) plans. We have investigated the feasibility of stitching together multi-isocenter fluence maps to then analyze the feathered junctions for patient-specific quality assurance (QA). Furthermore, we investigated the capability of Halcyon for the treatment of CSI patients. Three patients, who previously underwent VMAT CSI treatment on TrueBeam (6-MV flattening filter-free (FFF)) for 36 Gy in 20 fractions were replanned for Halcyon. A multi-isocenter approach with only translational superior-inferior shifts was used for both platforms. Each isocenter consists of two full arcs with anterior avoidance sectors, ±5° collimator rotations between arcs, and 5-8 cm of overlapping MLC auto-feathering junctions. All plans were QA'd via electronic portal imaging device (EPID) portal dosimetry and analyzed with a gamma criteria of 3%/3 mm. A variety of plan quality metrics were analyzed to evaluate dose distributions to the target, doses to organs at risk (OARs), and integral dose to the patient. A MATLAB script was developed to stitch the calculated and measured fluence maps in order to perform patient-specific QA for the composite fluence. The Halcyon plans provided highly conformal and homogenous dose distributions to the entire CSI target, superior to the clinical TrueBeam plans, while sparing critical organs with significantly lower values of V10Gy and V18Gy by up to 2% and 2.5%, respectively. Qualitative depictions of vertical dose profiles from the stitched DICOM of the entire CSI target for both planned and delivered fluence maps demonstrated equivalency, with slightly lower average pass rates with Halcyon (97%) compared to TrueBeam (99.9%). This approach to stitch multiple measured versus calculated EPID fluence maps has shown to be a feasible and accurate method and will be helpful for comprehensive VMAT CSI QA on both platforms. Further implementation of this script will be used in examining dosimetric impacts of daily patient positioning errors at MLC auto-feathering junctions.
Language	English
Publishing date	2023-09-20
Publishing country	United States
Document type	Journal Article
ZDB-ID	2747273-5
ISSN	2168-8184
ISSN	2168-8184
DOI	10.7759/cureus.45640
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Article ; Online: Benchmarking halcyon ring delivery system for hypofractionated breast radiotherapy: Validation and clinical implementation of the fast-forward trial.

Pokhrel, Damodar / Smith, Mason / Volk, Alexander / Bernard, Mark E

Journal of applied clinical medical physics

2023 Volume 24, Issue 9, Page(s) e14047

Abstract: Purpose: The aim of this study was to demonstrate the feasibility and efficacy of an iterative CBCT-guided breast radiotherapy with Fast-Forward trial of 26 Gy in five fractions on a Halcyon Linac. This study quantifies Halcyon plan quality, treatment ... ...

Abstract	Purpose: The aim of this study was to demonstrate the feasibility and efficacy of an iterative CBCT-guided breast radiotherapy with Fast-Forward trial of 26 Gy in five fractions on a Halcyon Linac. This study quantifies Halcyon plan quality, treatment delivery accuracy and efficacy by comparison with those of clinical TrueBeam plans. Materials and methods: Ten accelerated partial breast irradiation (APBI) patients (four right, six left) who underwent Fast-Forward trial at our institute on TrueBeam (6MV beam) were re-planned on Halcyon (6MV-FFF). Three site-specific partial coplanar VMAT arcs and an Acuros-based dose engine were used. For benchmarking, PTV coverage, organs-at-risk (OAR) doses, beam-on time, and quality assurance (QA) results were compared for both plans. Results: The average PTV was 806 cc. Compared to TrueBeam plans, Halcyon provided highly conformal and homogeneous plans with similar mean PTVD95 (25.72 vs. 25.73 Gy), both global maximum hotspot < 110% (p = 0.954) and similar mean GTV dose (27.04 vs. 26.80 Gy, p = 0.093). Halcyon provided lower volume of ipsilateral lung receiving 8 Gy (6.34% vs. 8.18%, p = 0.021), similar heart V1.5 Gy (16.75% vs. 16.92%, p = 0.872), V7Gy (0% vs. 0%), mean heart dose (0.96 vs. 0.9 Gy, p = 0.228), lower maximum dose to contralateral breast (3.2 vs. 3.6 Gy, p = 0.174), and nipple (19.6 vs. 20.1 Gy, p = 0.363). Compared to TrueBeam, Halcyon plans provided similar patient-specific QA pass rates and independent in-house Monte Carlo second check results of 99.6% vs. 97.9% (3%/2 mm gamma criteria) and 98.6% versus 99.2%, respectively, suggesting similar treatment delivery accuracy. Halcyon provided shorter beam-on time (1.49 vs. 1.68 min, p = 0.036). Conclusion: Compared to the SBRT-dedicated TrueBeam, Halcyon VMAT plans provided similar plan quality and treatment delivery accuracy, yet potentially faster treatment via one-step patient setup and verification with no patient collision issues. Rapid delivery of daily APBI on Fast-Forward trial on Halcyon with door-to-door patient time < 10 min, could reduce intrafraction motion errors, and improve patient comfort and compliance. We have started treating APBI on Halcyon. Clinical follow-up results are warranted. We recommend Halcyon users consider implementing the protocol to remote and underserved APBI patients in Halcyon-only clinics.
MeSH term(s)	Humans ; Benchmarking ; Lung/radiation effects ; Radiosurgery/methods ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted/methods ; Radiotherapy, Intensity-Modulated/methods ; Female
Language	English
Publishing date	2023-05-23
Publishing country	United States
Document type	Clinical Trial ; Journal Article
ZDB-ID	2010347-5
ISSN	1526-9914 ; 1526-9914
ISSN (online)	1526-9914
ISSN	1526-9914
DOI	10.1002/acm2.14047
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Two novel stereotactic radiotherapy methods for locally advanced, previously irradiated head and neck cancers patients.

Pokhrel, Damodar / Misa, Josh / McCarthy, Shane / Yang, Eddy S

Medical dosimetry : official journal of the American Association of Medical Dosimetrists

2023 Volume 49, Issue 2, Page(s) 114–120

Abstract: To determine the feasibility and utility of conebeam CT-guided stereotactic radiotherapy for locally recurrent, previously irradiated head and neck cancer (HNC) patients on the Halcyon, a ring delivery system (RDS). This research aims to quantify plan ... ...

Abstract	To determine the feasibility and utility of conebeam CT-guided stereotactic radiotherapy for locally recurrent, previously irradiated head and neck cancer (HNC) patients on the Halcyon, a ring delivery system (RDS). This research aims to quantify plan quality, treatment delivery accuracy, and overall efficacy by comparing against novel clinical TrueBeam HyperArc method. Ten recurrent HNC patients who were treated at our institution on TrueBeam (6MV-FFF) for 30 to 40 Gy in 3 to 5 fractions with noncoplanar HyperArc plans were re-planned on Halcyon (6MV-FFF). These plans were re-planned with the same Acuros-based dose engine. Additionally, we used site-specific full/partial coplanar VMAT arcs. PTV coverage, mean dose to GTV, maximum dose to organs-at-risk (OAR), beam-on time (BOT), and quality assurance (QA) results were investigated and compared. Halcyon provided highly conformal HNC SRT plans with slightly superior mean PTVD99 coverage (96.7% vs 95.5%, p = 0.071), and slightly lower mean GTV dose (37.8 Gy vs 38.2 Gy, p = 0.241) when compared to the HyperArc plans. Differences in plan conformality and maximum dose to OARs were statistically insignificant. Due to Halcyon's coplanar geometry, D2cm was significantly higher (p = 0.001) but Halcyon did result in a reduced normal brain dose by 1 Gy on average and up to 5.2 Gy in some cases. Halcyon provided similar patient-specific QA pass rates with a 2%/2mm gamma criteria (98.2% vs 98.5%) and independent in-house Monte Carlo second check results (97.7% vs 98.2%), suggesting identical treatment delivery accuracy. Halcyon plans resulted in slightly longer beam-on time (3.16 vs 2.30 minutes, p = 0.010), however door-to-door patient time is expected to be <10 minutes. Compared to clinical TrueBeam HyperArc, Halcyon SRT plans provided similar plan quality and treatment delivery accuracy with a potentially faster overall treatment using fully automated patient setup and verification. Rapid delivery of recurrent HNC SRT may reduce intrafraction motion errors while also improving patient compliance and comfort. To provide high-quality of HNC SRT similar to HyperArc, we recommend Halcyon users consider commissioning this novel method. This method will be useful for remote and underserved patient cohorts including Halcyon-only clinics as well.
MeSH term(s)	Humans ; Head and Neck Neoplasms/radiotherapy ; Radiotherapy Planning, Computer-Assisted/methods ; Radiosurgery/methods ; Radiotherapy Dosage ; Neoplasm Recurrence, Local/radiotherapy ; Organs at Risk ; Radiotherapy, Intensity-Modulated/methods ; Feasibility Studies
Language	English
Publishing date	2023-10-20
Publishing country	United States
Document type	Journal Article
ZDB-ID	645065-9
ISSN	1873-4022 ; 0958-3947 ; 0739-0211
ISSN (online)	1873-4022
ISSN	0958-3947 ; 0739-0211
DOI	10.1016/j.meddos.2023.09.003
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Jg. 1995 - 2021: Lesesall (2.OG)
ab Jg. 2022: Lesesaal (EG)

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Article: Gamma Knife Radiosurgery to Four Brainstem Lesions After Whole Brain Radiation Therapy.

Bernard, Mark E / St Clair, William / Pokhrel, Damodar

Cureus

2021 Volume 13, Issue 8, Page(s) e17226

Abstract: Our patient was a 58-year-old female with a history of extensive stage small cell lung cancer initially diagnosed in November 2018. She received palliative radiation to the right hip and whole brain in December of 2018 and then received chemotherapy. ... ...

Abstract	Our patient was a 58-year-old female with a history of extensive stage small cell lung cancer initially diagnosed in November 2018. She received palliative radiation to the right hip and whole brain in December of 2018 and then received chemotherapy. Unfortunately, in October 2019, the repeat brain magnetic resonance imaging (MRI) showed recurrent lesions and she was referred for Gamma Knife Radiosurgery (GKRS). At the time of the treatment, she was found to have four brainstem lesions as well as a left frontal lobe and a right frontal lobe lesion. She completed GKRS to all six lesions without any neurological complications seen in her short-term follow-up. This case report adds to the growing body of literature showing safety of GKRS for multiple brainstem lesions.
Language	English
Publishing date	2021-08-16
Publishing country	United States
Document type	Case Reports
ZDB-ID	2747273-5
ISSN	2168-8184
ISSN	2168-8184
DOI	10.7759/cureus.17226
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Article ; Online: Improving treatment efficiency via photon optimizer (PO) MLC algorithm for synchronous single-isocenter/multiple-lesions VMAT lung SBRT.

Sanford, Lana / Pokhrel, Damodar

Journal of applied clinical medical physics

2019 Volume 20, Issue 10, Page(s) 201–207

Abstract: Purpose: Elderly patients with multiple primary or oligometastases (<5 lesions) lesions with associated co-morbidities may not retain their treatment position for the traditional long SBRT treatment time with individual isocenters for each lesion. ... ...

Abstract	Purpose: Elderly patients with multiple primary or oligometastases (<5 lesions) lesions with associated co-morbidities may not retain their treatment position for the traditional long SBRT treatment time with individual isocenters for each lesion. Treating multiple lesions synchronously using a single-isocenter volumetric arc therapy (VMAT) plan would be more efficient with the use of the most recently adopted photon optimizer (PO) MLC algorithm and improve the patient comfort. Herein, we quantified the clinical performance of PO versus its predecessor progressive resolution optimizer (PRO) algorithm for single-isocenter/multiple-lesions VMAT lung SBRT. Materials and methods: Fourteen patients with metastatic non-small-cell lung cancer lesions (two to five, both uni- and bilateral lungs) received a highly conformal single-isocenter co/non-coplanar VMAT (2-6 arcs) SBRT treatment plan. Patients were treated with a 6X-FFF beam and Acuros algorithm with a single-isocenter placed between/among the lesions, using PO for MLC optimization. Average isocenter to tumor distance was 5.5 ± 1.9 cm. Mean combined PTV derived from 4D-CT scans was 38.7 ± 22.7 cc. Doses were 54 Gy/50 Gy in 3/5 fractions prescribed to 70%-80% isodose line so that at least 95% of the PTV receives 100% of prescribed dose. Plans were re-optimized using PRO algorithm. Plans were compared via ROTG-0915 protocol criteria for target conformity, heterogeneity and gradient indices, and dose to organs-at-risk (OAR). Additionally, total number of monitor units (MU), modulation factor (MF) and beam-on time were compared. Results: All plans met SBRT protocol requirements for target coverage and OAR doses. Comparison of target coverage and dose to the OAR showed no statistical significance between the two plans. PO had 1042 ± 753 (P < 0.001) less MU than PRO resulting in a beam-on time of about 0.75 ± 0.5 min (P < 0.001) less, on average. For similar dose distribution, a significant reduction of beam delivery complexity was observed with PO (average MF = 3.7 ± 0.7) vs PRO MLC algorithm (average MF = 4.4 ± 1.3) (P < 0.001). Conclusions: PO MLC algorithm improved treatment efficiency without compromising plan quality when compared to PRO algorithm for single-isocenter/multi-lesions VMAT lung SBRT. Shorter beam-on time can potentially reduce intrafraction motion errors and improve patient compliance. PO MLC algorithm is recommended for future clinical lung SBRT plan optimization.
MeSH term(s)	Algorithms ; Carcinoma, Non-Small-Cell Lung/secondary ; Carcinoma, Non-Small-Cell Lung/surgery ; Four-Dimensional Computed Tomography/methods ; Humans ; Lung Neoplasms/pathology ; Lung Neoplasms/surgery ; Lung Volume Measurements ; Organs at Risk/radiation effects ; Phantoms, Imaging ; Photons ; Prognosis ; Quality Assurance, Health Care/standards ; Radiosurgery/standards ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted/standards ; Radiotherapy, Intensity-Modulated/methods ; Retrospective Studies
Language	English
Publishing date	2019-09-20
Publishing country	United States
Document type	Journal Article
ZDB-ID	2010347-5
ISSN	1526-9914 ; 1526-9914
ISSN (online)	1526-9914
ISSN	1526-9914
DOI	10.1002/acm2.12721
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Article ; Online: Clinical evaluation of photon optimizer (PO) MLC algorithm for stereotactic, single-dose of VMAT lung SBRT.

Visak, Justin / McGarry, Ronald C / Pokhrel, Damodar

Medical dosimetry : official journal of the American Association of Medical Dosimetrists

2020 Volume 45, Issue 4, Page(s) 321–326

Abstract: Recently implemented photon optimizer (PO) MLC optimization algorithm is mandatory for RapidPlan modeling in Eclipse. This report quantifies and compares the dosimetry and treatment delivery parameters of PO vs its predecessor progressive resolution ... ...

Abstract	Recently implemented photon optimizer (PO) MLC optimization algorithm is mandatory for RapidPlan modeling in Eclipse. This report quantifies and compares the dosimetry and treatment delivery parameters of PO vs its predecessor progressive resolution optimizer (PRO) algorithm for a single-dose of volumetric modulated arc therapy (VMAT) lung stereotactic body radiation therapy (SBRT). Clinical SBRT treatment plans for 12 early-stage non-small-cell lung cancer patients receiving 30 Gy in 1 fraction using PRO-VMAT were re-optimized using the PO-VMAT MLC algorithm with identical planning parameters and objectives. Average planning target volume derived from the 4D CT scans was 13.6 ± 12.0 cc (range: 4.3 to 41.1 cc) Patients were treated with 6 MV flattening filter free beam using Acuros-based calculations and 2.5 mm calculation grid-size (CGS). Both treatment plans were normalized to receive same target coverage and identical CGS to isolate effects of MLC positioning optimizers. Original PRO and re-optimized PO plans were compared via RTOG-0915 protocol compliance criteria for target conformity, gradient indices, dose to organs at risks and delivery efficiency. Additionally, PO-VMAT plans with a 1.25 mm CGS were evaluated. Both plans met RTOG protocol requirements. Conformity indices showed no statistical difference between PO 2.5 mm CGS and PRO 2.5 mm CGS plans. Gradient index (p = 0.03), maximum dose to 2 cm away from planning target volume in any direction (D
MeSH term(s)	Algorithms ; Carcinoma, Non-Small-Cell Lung/radiotherapy ; Four-Dimensional Computed Tomography ; Humans ; Lung ; Lung Neoplasms/radiotherapy ; Lung Neoplasms/surgery ; Organs at Risk ; Radiosurgery ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted ; Radiotherapy, Intensity-Modulated
Language	English
Publishing date	2020-05-20
Publishing country	United States
Document type	Journal Article
ZDB-ID	645065-9
ISSN	1873-4022 ; 0958-3947 ; 0739-0211
ISSN (online)	1873-4022
ISSN	0958-3947 ; 0739-0211
DOI	10.1016/j.meddos.2020.03.004
Database	MEDical Literature Analysis and Retrieval System OnLINE

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