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Background: Stereotactic radiosurgery (SRS) is a widely employed strategy for intracranial metastases, utilizing linear accelerators and volumetric modulated arc therapy (VMAT). Ensuring precise linear accelerator performance is crucial, given the small planning target volume (PTV) margins. Rapid dose falloff is vital to minimize brain radiation necrosis. Despite advances in SRS planning, tools for end‐to‐end testing of SRS treatments are lacking, hindering confidence in the procedure. Purpose: This study introduces a novel end‐to‐end three‐dimensional (3D) anthropomorphic dosimetry system for characterization of a radiosurgery platform, aiming to measure planning metrics, dose gradient index (DGI), brain volumes receiving at least 10 and 12 Gy (V10, V12), as well as assess delivery uncertainties in multitarget treatments. The study also compares metrics from benchmark plans to enhance understanding and confidence in SRS treatments. Methods: The developed anthropomorphic 3D dosimetry system includes a modified Stereotactic End‐to‐End Verification (STEEV) phantom with a customized insert integrating 3D dosimeters and a fiber optic CT scanner. Labview and MATLAB programs handle optical scanning, image preprocessing, and dosimetric analysis. SlicerRT is used for 3D dose visualization and analysis. A film stack insert was used to validate the 3D dosimeter measurements at specific slices. Benchmark plans were developed and measured to investigate off‐axis errors, dose spillage, small field dosimetry, and multi‐target delivery. Results: The accuracy of the developed 3D dosimetry system was rigorously assessed using radiochromic films. Two two‐dimensional (2D) dose planes, extracted from the 3D dose distribution, were compared with film measurements, resulting in high passing rates of 99.9% and 99.6% in gamma tests. The mean relative dose difference between film and 3D dosimeter measurements was −1%, with a standard deviation of 2.2%, well within dosimeter uncertainties. In the first module, evaluating single‐isocenter multitarget treatments, a 1.5 mm dose distribution shift was observed when targets were 7 cm off‐axis. This shift was attributed to machine mechanical errors and image‐guided system uncertainties, indicating potential limitations in conventional gamma tests. The second module investigated discrepancies in intermediate‐to‐low dose spillage, revealing higher measured doses in the connecting region between closely positioned targets. This discrepancy was linked to uncertainties in treatment planning system (TPS) modeling of out‐of‐field dose and multileaf collimator (MLC) characteristics, resulting in lower DGI values and higher V10 and V12 values compared to TPS calculations. In the third module, irradiating multiple targets showed consistent V10 and V12 values within 1 cm3 agreement with dose calculations. However, lower DGI values from measurements compared to calculations suggested intricacies in the treatment process. Conducting vital end‐to‐end testing demonstrated the anthropomorphic 3D dosimetry system's capacity to assess overall treatment uncertainty, offering a valuable tool for enhancing treatment accuracy in radiosurgery platforms. Conclusions: The study introduces a novel anthropomorphic 3D dosimetry system for end‐to‐end testing of a radiosurgery platform. The system effectively measures plan quality metrics, captures mechanical errors, and visualizes dose discrepancies in 3D space. The comprehensive evaluation capability enhances confidence in the commissioning and verification process, ensuring patient safety. The system is recommended for commissioning new radiosurgery platforms and remote auditing of existing programs. [ABSTRACT FROM AUTHOR]

Background and purpose: Motion management techniques are important to spare the healthy tissue adequately. However, they are complex and need dedicated quality assurance. The aim of this study was to create a dynamic phantom designed for quality assurance and to replicate a patient’s size, anatomy, and tissue density. Materials and methods: A computed tomography (CT) scan of a cancer patient was used to create molds for the lungs, heart, ribs, and vertebral column via additive manufacturing. A pump system and software were developed to simulate respiratory dynamics. The extent of respiratory motion was quantified using a 4DCT scan. End-to-end tests were conducted to evaluate two motion management techniques for lung stereotactic body radiotherapy (SBRT). Results: The chest wall moved between 4 mm and 13 mm anteriorly and 2 mm to 7 mm laterally during the breathing. The diaphragm exhibited superior-inferior movement ranging from 5 mm to 16 mm in the left lung and 10 mm to 36 mm in the right lung. The left lung tumor displaced ± 7 mm superior-inferiorly and anterior-posteriorly. The CT numbers were for lung: −716 ± 108 HU (phantom) and −713 ± 70 HU (patient); bone: 460 ± 20 HU (phantom) and 458 ± 206 HU (patient); soft tissue: 92 ± 9 HU (phantom) and 60 ± 25 HU (patient). The end-to-end testing showed an excellent agreement between the measured and the calculated dose for ion chamber and film dosimetry. Conclusions: The phantom is recommended for quality assurance, evaluating the institution’s specific planning and motion management strategies either through end-to-end testing or as an external audit phantom.

Purpose: The purpose of the study was to investigate the dosimetric characteristics of radiophotoluminescent glass dosimeters (RGDs) for pencil beam scanning proton therapy. The RGD's end-to-end testing of intensity-modulated proton therapy (IMPT) plans was also evaluated. Materials and Methods: The dosimetric characteristics of the GD-302M type glass dosimeter were studied in terms of uniformity, short-term and long-term reproducibility, stability of the magazine position readout, dose linearity in the range from 0.2 to 20 Gy, energy response in 70-220 MeV, and fading effect. The reference conditions of the spot scanning beam from the Varian ProBeam Compact system were operation at 160 MeV, a 2 cm water-equivalent depth in a solid water phantom, a 10 cm × 10 cm field size at the isocenter, and 2 Gy dose delivery. End-to-end testing of IMPT plans for the head, abdomen, and pelvis was verified using the Alderson Rando phantom. The overall uncertainty analysis was confirmed in this study. Results: The relative response of RGDs for the uniformity test was within 0.95-1.05. The percentages of the coefficients of variation for short-term and long-term reproducibility were 1.16% and 1.50%, respectively. The dose ACE glass dosimetry reader FGD-1000 showed a stable magazine position readout. The dose was found to be linear with R2 = 0.9988. The energy response relative to 160 MeV was approximately within 4.0%. The fading effect was within 2.4%. For the end-to-end test, the difference between the treatment plan and RGD measurement was within 1.0%. The overall uncertainty of the RGD measurement for the proton beam was 4.6%, which covered all energy ranges in this study. Conclusion: The experimental study indicates that the RGDs have the potential to be used in the dosimetry of therapeutic proton beams, including end-to-end dosimetry. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of the study was to investigate the dosimetric characteristics of radiophotoluminescent glass dosimeters (RGDs) for pencil beam scanning proton therapy. The RGD's end-to-end testing of intensity-modulated proton therapy (IMPT) plans was also evaluated. Materials and Methods: The dosimetric characteristics of the GD-302M type glass dosimeter were studied in terms of uniformity, short-term and long-term reproducibility, stability of the magazine position readout, dose linearity in the range from 0.2 to 20 Gy, energy response in 70–220 MeV, and fading effect. The reference conditions of the spot scanning beam from the Varian ProBeam Compact system were operation at 160 MeV, a 2 cm water-equivalent depth in a solid water phantom, a 10 cm × 10 cm field size at the isocenter, and 2 Gy dose delivery. End-to-end testing of IMPT plans for the head, abdomen, and pelvis was verified using the Alderson Rando phantom. The overall uncertainty analysis was confirmed in this study. Results: The relative response of RGDs for the uniformity test was within 0.95–1.05. The percentages of the coefficients of variation for short-term and long-term reproducibility were 1.16% and 1.50%, respectively. The dose ACE glass dosimetry reader FGD-1000 showed a stable magazine position readout. The dose was found to be linear with R2 = 0.9988. The energy response relative to 160 MeV was approximately within 4.0%. The fading effect was within 2.4%. For the end-to-end test, the difference between the treatment plan and RGD measurement was within 1.0%. The overall uncertainty of the RGD measurement for the proton beam was 4.6%, which covered all energy ranges in this study. Conclusion: The experimental study indicates that the RGDs have the potential to be used in the dosimetry of therapeutic proton beams, including end-to-end dosimetry.

Purpose: The study is intended to perform an end-to-end test of the entire intraoperative process using cadaver heads. A simulation of tumor removal was performed, followed by irradiation of the bed and measurement of absorbed doses with radiochromic films. Materials and Methods: Low-energy X-ray intraoperative radiotherapy (IORT) was used for irradiation. A computed tomography study was performed at each site and the absorbed doses calculated by the treatment planning system, as well as absorbed doses with radiochromic films, were studied. Results: The absorbed doses in the organs at risk (OAR) were evaluated in each case, obtaining maximum doses within the tolerance limits. The absorbed doses in the target were verified and the deviations were

Purpose: The study is intended to perform an end‑to‑end test of the entire intraoperative process using cadaver heads. A simulation of tumor removal was performed, followed by irradiation of the bed and measurement of absorbed doses with radiochromic films. Materials and Methods: Low‑energy X‑ray intraoperative radiotherapy (IORT) was used for irradiation. A computed tomography study was performed at each site and the absorbed doses calculated by the treatment planning system, as well as absorbed doses with radiochromic films, were studied. Results: The absorbed doses in the organs at risk (OAR) were evaluated in each case, obtaining maximum doses within the tolerance limits. The absorbed doses in the target were verified and the deviations were <1%. Conclusions: These tests demonstrated that this comprehensive procedure is a reproducible quality assurance tool which allows continuous assessment of the dosimetric and geometric accuracy of clinical brain IORT treatments. Furthermore, the absorbed doses measured in both target and OAR are optimal for these treatments. [ABSTRACT FROM AUTHOR]

• Set-up of a Stereotactic Body Radiation Therapy (SBRT) e2e test. • Multicenter validation of the e2e test. • All participants were successful in performing the e2e test following the instructions. Set up a lung SBRT end-to-end (e2e) test and perform a multicentre validation. A group of medical physicists from four hospitals and the Italian Institute of Ionizing Radiation Metrology designed the present e2e test. One sub-group set up the test, while another tested its feasibility and ease of use. A satisfaction questionnaire was used to collect user feedback. Each participating centre (PC) received the ADAM breathing phantom, a microDiamond detector and radiochromic films. Following the e2e protocol, each PC performed its standard internal procedure for simulating, planning, and irradiating the phantom. Each PC uploaded its planning and treatment delivery data in a shared Google Drive. A single centre analyzed all the data. The e2e test was successfully performed by all PCs. Participants' comments indicated that ADAM was well suited to the purpose and the protocol well described. All PCs performed the test in static and dynamic modes. The ratio between measured and planned point dose obtained by PC1, PC2, PC3, PC4 was: 0.99, 0.96, 1.01 and 1.01 (static track) and 0.99, 1.02, 1.01 and 0.94 (dynamic track). The gamma passing rates (3 % global, 3 mm) between planned and measured dose maps were 98.5 %, 94.0 %, 99.1 % and 94.0 % (static track) and 99.5 %, 96.5 %, 86.0 % and 94.5 % (dynamic track) for PC1, PC2, PC3 and PC4, respectively. An e2e test for lung SBRT has been proposed and tested in a multicentre framework. The results and user feedback prove the validity of the proposed e2e test. [ABSTRACT FROM AUTHOR]

Purpose: End‐to‐end testing (E2E) is a necessary process for assessing the readiness of the stereotactic radiosurgery (SRS) program and annual QA of an SRS system according to the AAPM MPPG 9a. This study investigates the differences between using a new SRS MapCHECK (SRSMC) system and an anthropomorphic phantom film‐based system in a large network with different SRS delivery techniques. Methods and materials: Three SRS capable Linacs (Varian Medical Systems, Palo Alto, CA) at three different regional sites were chosen to represent a hospital network, a Trilogy with an M120 multi‐leaf collimator (MLC), a TrueBeam with an M120 MLC, and a TrueBeam Stx with an HD120 MLC. An anthropomorphic STEEV phantom (CIRS, Norfolk, VA) and a phantom/diode array: StereoPHAN/SRSMC (Sun Nuclear, Melbourne, FL) were CT scanned at each site. The new STV‐PHANTOM EBT‐XD films (Ashland, Bridgewater, NJ) were used. Six plans with various complexities were measured with both films and SRSMC in the StereoPHAN to establish their dosimetric correlations. Three SRS cranial plans with a total of sixteen fields using dynamic conformal arc and volumetric‐modulated arc therapy, with 1–4 targets, were planned with Eclipse v15.5 treatment planning system (TPS) using a custom SRS beam model for each machine. The dosimetric and localization accuracy were compared. The time of analysis for the two systems by three teams of physicists was also compared to assess the throughput efficiency. Results: The correlations between films and SRSMC were found to be 0.84 (p = 0.03) and 0.16 (p = 0.76) for γ (3%, 1 mm) and γ (3%, 2 mm), respectively. With film, the local dose differences (ΔD) relative to the average dose within the 50% isodose line from the three sites were found to be −3.2%–3.7%. The maximum localization errors (Elocal) were found to be within 0.5 ± 0.2 mm. With SRSMC, the ΔD was found to be within 5% of the TPS calculation. Elocal were found to be within 0.7 to 1.1 ± 0.4 mm for TrueBeam and Trilogy, respectively. Comparing with film, an additional uncertainty of 0.7 mm was found with SRSMC. The delivery and analysis times were found to be 6 and 2 h for film and SRSMC, respectively. Conclusions: The SRS MapCHECK agrees dosimetrically with the films within measurement uncertainties. However, film dosimetry shows superior sub‐millimeter localization resolving power for the MPPG 9a implementation. [ABSTRACT FROM AUTHOR]

Online magnetic resonance (MR)‐guided radiotherapy is expected to benefit brain stereotactic radiosurgery (SRS) due to superior soft tissue contrast and capability of daily adaptive planning. The purpose of this study was to investigate daily adaptive plan quality with setup variations and to perform an end‐to‐end test for brain SRS with multiple metastases treated with a 1.5‐Tesla MR‐Linac (MRL). The RTsafe PseudoPatient Prime brain phantom was used with a delineation insert that includes two predefined structures mimicking gadolinium contrast‐enhanced brain lesions. Daily adaptive plans were generated using six preset and six random setup variations. Two adaptive plans per daily MR image were generated using the adapt‐to‐position (ATP) and adapt‐to‐shape (ATS) workflows. An adaptive patient plan was generated on a diagnostic MR image with simulated translational and rotational daily setup variation and was compared with the reference plan. All adaptive plans were compared with the reference plan using the target coverage, Paddick conformity index, gradient index (GI), Brain V12 or V20, optimization time and total monitor units. Target doses were measured as an end‐to‐end test with two ionization chambers inserted into the phantom. With preset translational variations, V12 from the ATS plan was 17% lower than that of the ATP plan. With a larger daily setup variation, GI and V12 of the ATS plan were 10% and 16% lower than those of the ATP plan, respectively. Compared to the ATP plans, the plan quality index of the ATS plans was more consistent with the reference plan, and within 5% in both phantom and patient plans. The differences between the measured and planned target doses were within 1% for both treatment workflows. Treating brain SRS using an MRL is feasible and could achieve satisfactory dosimetric goals. Setup uncertainties could be accounted for using online plan adaptation. The ATS workflow achieved better dosimetric results than the ATP workflow at the cost of longer optimization time. [ABSTRACT FROM AUTHOR]

Background and purpose: Post-operative spine stereotactic body radiation therapy (SBRT) represents a significant challenge as there are many restrictions on beam geometry to avoid metal hardware as it surrounds the target volume. In this study, an international multi-institutional end-to-end test using an in-house spine phantom was developed and executed. The aim was to evaluate the impact of titanium spine hardware on planned and delivered dose for post-operative spine SBRT. Materials and methods: Five centers performed simulation, planning and irradiation of the spine phantom, with/without titanium metal hardware (MB/B), following our pre-specified protocol. The doses were calculated using the centers’ treatment planning system (TPS) and measured with radiophotoluminescent glass dosimeters (RPLDs) embedded within each phantom. Results: The dose differences between the RPLD measured and calculated doses in the target region were within ± 5% for both phantoms studied. Differences greater than 5% were observed for the spinal cord and the out-of-the target regions due to steeper dose gradient regions that are created in these plans. Dose measurements within ± 3% were observed between RPLDs that were embedded in MB and B inserts. For the spinal cord and the out-of-target regions surrounded by metal hardware, the dose measured using RPLDs was within 3% different near the titanium screws compared to the dose measured near only the metal rods. Conclusion: We have successfully performed the first multi-institutional end-to-end dose analysis using an in-house phantom built specifically for post-operative spine SBRT. The differences observed between the measured and planned doses in the presence of metal hardware were clinically insignificant.

The introduction of real-time imaging by magnetic resonance guided linear accelerators (MR-Linacs) enabled adaptive treatments and gating on the tumor position. Different end-to-end tests monitored the accuracy of our MR-Linac during the first year of clinical operation. We report on the stability of these tests covering a static, adaptive and gating workflow. Film measurements showed gamma passing rates of 96.4% ± 3.4% for the static tests (five measurements) and for the two adaptive tests 98.9% and 99.99%, respectively (criterion 2%/2mm). The gated point dose measurements in the breathing phantom were 2.7% lower than in the static phantom.

Objective . The FLASH effect can potentially be used to improve the therapeutic ratio of radiotherapy (RT) through delivery of Ultra-high-dose-rate (UHDR) irradiation. Research is actively being conducted to translate UHDR-RT and for this purpose the Mobetron is capable of producing electron beams at both UHDR and conventional dose rates for FLASH research and translation. This work presents commissioning of an UHDR Mobetron with end-to-end tests developed for preclinical research. Approach . UHDR electron beams were commissioned with an efficient approach utilizing a 3D-printed water tank and film to fully characterize beam characteristics and dependences on field size, pulse width (PW) and pulse repetition frequency (PRF). This commissioning data was used to implement a beam model using the GAMOS Monte Carlo toolkit for the preclinical research. Then, the workflow for preclinical FLASH irradiation was validated with end-to-end tests delivered to a 3D-printed mouse phantom with internal inhomogeneities. Main results. PDDs, profiles and output factors acquired with radiochromic films were precisely measured, with a PRF that showed little effect on the UHDR beam energy and spatial characteristics. Increasing PW reduced the D max and R 50 by 2.08 mm µ s -1 and 1.28 mm µ respectively. An end-to-end test of the preclinical research workflow showed that both profiles in head-foot and lateral directions were in good agreement with the MC calculations for the heterogeneous 3D printed mouse phantom with Gamma index above 93% for 2 mm/2% criteria, and 99% for 3 mm/3%. -1 respectively. An end-to-end test of the preclinical research workflow showed that both profiles in head-foot and lateral directions were in good agreement with the MC calculations for the heterogeneous 3D printed mouse phantom with Gamma index above 93% for 2 mm/2% criteria, and 99% for 3 mm/3%. Significance . The UHDR Mobetron is a versatile tool for FLASH preclinical research and this comprehensive beam model and workflow was validated to meet the requirements for conducting translational FLASH research., (© 2024 Institute of Physics and Engineering in Medicine.)

Featured Application: Transit dosimetry, with Electronic Portal Imaging Device (EPID), is a powerful tool for in vivo dosimetry (IVD). Despite its wide availability and its simplicity of use, the clinical implementation of such a dosimetric technique is still challenging. One reason for the difficulty of IVD implementation is the lack of guidelines around the validation and acceptance of EPID IVD algorithms. In this paper we propose an evaluation method for assessing the accuracy of a novel 3D EPID back-projection algorithm for IVD. To the best of our knowledge, the EPID back-projection algorithms have never been validated in anthropomorphic phantom against direct two-dimensional measurements, and the new algorithm, introduced in version 5.8 of the Dosimetry Check software for dealing with tissue inhomogeneity, has never been evaluated before. The aim of this study was to develop and apply an evaluation method for assessing the accuracy of a novel 3D EPID back-projection algorithm for in vivo dosimetry. The novel algorithm of Dosimetry Check (DC) 5.8 was evaluated. A slab phantom homogeneously filled, or with air and bone inserts, was used for fluence reconstruction of different squared fields. VMAT plans in different anatomical sites were delivered on an anthropomorphic phantom. Dose distributions were measured with radiochromic films. The 2D Gamma Agreement Index (GAI) between the DC and the film dose distributions (3%, 3 mm) was computed for assessing the accuracy of the algorithm. GAIs between films and TPS and between DC and TPS were also computed. The fluence reconstruction accuracy was within 2% for all squared fields in the three slabs' configurations. The GAI between the DC and the film was 92.7% in the prostate, 92.9% in the lung, 96.6% in the head and the neck, and 94.6% in the brain. An evaluation method for assessing the accuracy of a novel EPID algorithm was developed. The DC algorithm was shown to be able to accurately reconstruct doses in all anatomic sites, including the lung. The methodology described in the present study can be applied to any EPID back-projection in vivo algorithm. [ABSTRACT FROM AUTHOR]

An independent dosimetry audit based on end-to-end testing of the entire chain of radiation therapy delivery is highly recommended to ensure consistent treatments among proton therapy centers. This study presents an auditing methodology developed by the MedAustron Ion Beam Therapy Center (Austria) in collaboration with the National Physical Laboratory (UK) and audit results for five scanned proton beam therapy facilities in Europe. The audit procedure used a homogeneous and an anthropomorphic head phantom. The phantoms were loaded either with an ionization chamber or with alanine pellets and radiochromic films. Homogeneously planned doses of 10 Gy were delivered to a box-like target volume in the homogeneous phantom and to two clinical scenarios with increasing complexity in the head phantom. For all tests the mean of the local differences of the absolute dose to water determined with the alanine pellets compared to the predicted dose from the treatment planning system installed at the audited institution was determined. The mean value taken over all tests performed was −0.1 ± 1.0%. The measurements carried out with the ionization chamber were consistent with the dose determined by the alanine pellets with a mean deviation of −0.5 ± 0.6%. The developed dosimetry audit method was successfully applied at five proton centers including various "turn-key" Cyclotron solutions by IBA, Varian and Mevion. This independent audit with extension to other tumour sites and use of the correspondent anthropomorphic phantoms may be proposed as part of a credentialing procedure for future clinical trials in proton beam therapy. [ABSTRACT FROM AUTHOR]

Background and Purpose: Motion management techniques are important to spare the healthy tissue adequately. However, they are complex and need dedicated quality assurance. The aim of this study was to create a dynamic phantom designed for quality assurance and to replicate a patient's size, anatomy, and tissue density., Materials and Methods: A computed tomography (CT) scan of a cancer patient was used to create molds for the lungs, heart, ribs, and vertebral column via additive manufacturing. A pump system and software were developed to simulate respiratory dynamics. The extent of respiratory motion was quantified using a 4DCT scan. End-to-end tests were conducted to evaluate two motion management techniques for lung stereotactic body radiotherapy (SBRT)., Results: The chest wall moved between 4 mm and 13 mm anteriorly and 2 mm to 7 mm laterally during the breathing. The diaphragm exhibited superior-inferior movement ranging from 5 mm to 16 mm in the left lung and 10 mm to 36 mm in the right lung. The left lung tumor displaced ± 7 mm superior-inferiorly and anterior-posteriorly. The CT numbers were for lung: -716 ± 108 HU (phantom) and -713 ± 70 HU (patient); bone: 460 ± 20 HU (phantom) and 458 ± 206 HU (patient); soft tissue: 92 ± 9 HU (phantom) and 60 ± 25 HU (patient). The end-to-end testing showed an excellent agreement between the measured and the calculated dose for ion chamber and film dosimetry., Conclusions: The phantom is recommended for quality assurance, evaluating the institution's specific planning and motion management strategies either through end-to-end testing or as an external audit phantom., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Author(s).)

In this study, we aim to evaluate the comprehensive geometric accuracy of proton rotating gantries by performing an end-to-end test using a cone-shaped scintillator screen detector, known as XRV-124. The XRV-124 comprises a cone-shaped sheet-like scintillator and charge-coupled device camera that detects the scintillation light. First, the results of the Winston–Lutz and end-to-end XRV-124 tests performed on a conventional linear accelerator were compared to confirm the reliability of the XRV-124, and the snout position dependency of the geometric accuracy was evaluated for the proton rotating gantry as a pre-verification process. Thereafter, an end-to-end test including computed tomography imaging and irradiation in 30° steps from 0° to 330° for two proton rotating gantries, which have the same specifications, was performed. The results of the pre-verification indicated that sufficient accuracy was obtained for the end-to-end test of the proton rotating gantry. The end-to-end test results showed a peak-to-peak deviation of up to 2 mm for some of the coordinate axes. The two gantries exhibited almost similar results in terms of the absolute quantity; however, a few trends were different. Thus, the beam axis deviations were confirmed to be within the safety margin, as expected in clinical practice. Based on the results of this study, the XRV-124 can be used as a comprehensive end-to-end constancy test tool, as it enables a comparative verification of multiple rotating gantries and geometric accuracy verification of different treatment modalities. [ABSTRACT FROM AUTHOR]

The purpose of this study was to develop a novel quality assurance (QA) program to check the entire treatment chain of image-guided brachytherapy with dose distribution evaluation in a single setup and irradiation using a gel dosimeter. A polymer gel was used, and the readout was performed by magnetic resonance scanning. A CT-based treatment plan was generated using the Oncentra planning system (Elekta, Sweden), and irradiation was performed three times using an afterloading device with an Ir-192 source. The dose-response curve of the gel was created using 6-MV X-ray, which is independent of the source beams. Planar gamma images on a coronal plane along the source transport axis were calculated using the measured dose as a reference, and the calculated doses were used in several error simulations (no error; 2.0 or 2.5 mm systematic and random source dwell mispositioning; and dose error of 2%, 5%, 10%, and 20%). The dose- R 2 (spin-spin relaxation rate) conversion table revealed that the uncertainty and dose resolution of 6-MV X-ray were better than those of Ir-192 and also constant between the three measurements. With the 3%/1 mm criteria, there were statistically significant differences between each pair of settings except dose error of 2% and 5%. This work depicts a simple and efficient end-to-end test that can provide a clinically useful tool for QA of image-guided brachytherapy. In this QA program, air kerma strength and dwell position setting could also be verified. This test can also distinguish between different types of error. [ABSTRACT FROM AUTHOR]

The aim of this study was to develop and apply an evaluation method for assessing the accuracy of a novel 3D EPID back-projection algorithm for in vivo dosimetry. The novel algorithm of Dosimetry Check (DC) 5.8 was evaluated. A slab phantom homogeneously filled, or with air and bone inserts, was used for fluence reconstruction of different squared fields. VMAT plans in different anatomical sites were delivered on an anthropomorphic phantom. Dose distributions were measured with radiochromic films. The 2D Gamma Agreement Index (GAI) between the DC and the film dose distributions (3%, 3 mm) was computed for assessing the accuracy of the algorithm. GAIs between films and TPS and between DC and TPS were also computed. The fluence reconstruction accuracy was within 2% for all squared fields in the three slabs’ configurations. The GAI between the DC and the film was 92.7% in the prostate, 92.9% in the lung, 96.6% in the head and the neck, and 94.6% in the brain. An evaluation method for assessing the accuracy of a novel EPID algorithm was developed. The DC algorithm was shown to be able to accurately reconstruct doses in all anatomic sites, including the lung. The methodology described in the present study can be applied to any EPID back-projection in vivo algorithm.

Purpose: We created a phantom and analysis program for the assessment of IGRT positional accuracy. We verified the accuracy of analysis and the practicality of this evaluation method at several facilities., Method: End-to-end test was performed using an in-house phantom, and EPID images were acquired after displacement by an arbitrary amount using a micrometer, with after image registration as the reference. The difference between the center of the target and the irradiated field was calculated using our in-house analysis program and commercial software. The end-to-end test was conducted at three facilities, and the IGRT positional accuracy evaluation was verified., Result: The maximum difference between the displacement of the target determined from the EPID image and the arbitrary amount of micrometer displacement was 0.24 mm for the in-house analysis program and 0.30 mm for the commercial software. The maximum difference between the center of the target and the irradiation field on EPID images acquired at the three facilities was 0.97 mm., Conclusion: The proposed evaluation method using our in-house phantom and analysis program can be used for the assessment of IGRT positional accuracy.

Abstract We conducted a multi-institutional assessment of a recently developed end-to-end monthly quality assurance (QA) protocol for external beam radiation therapy treatment chains. This protocol validates the entire treatment chain against a baseline to detect the presence of complex errors not easily found in standard component-based QA methods. Participating physicists from 3 institutions ran the end-to-end protocol on treatment chains that include Imaging and Radiation Oncology Core (IROC)-credentialed linacs. Results were analyzed in the form of American Association of Physicists in Medicine (AAPM) Task Group (TG)-119 so that they may be referenced by future test participants. Optically stimulated luminescent dosimeter (OSLD), EBT3 radiochromic film, and A1SL ion chamber readings were accumulated across 10 test runs. Confidence limits were calculated to determine where 95% of measurements should fall. From calculated confidence limits, 95% of measurements should be within 5% error for OSLDs, 4% error for ionization chambers, and 4% error for (96% relative gamma pass rate) radiochromic film at 3% agreement/3 mm distance to agreement. Data were separated by institution, model of linac, and treatment protocol (intensity-modulated radiation therapy [IMRT] vs volumetric modulated arc therapy [VMAT]). A total of 97% of OSLDs, 98% of ion chambers, and 93% of films were within the confidence limits; measurements were found outside these limits by a maximum of 4%, < 1%, and < 1%, respectively. Data were consistent despite institutional differences in OSLD reading equipment and radiochromic film calibration techniques. Results from this test may be used by clinics for data comparison. Areas of improvement were identified in the end-to-end protocol that can be implemented in an updated version. The consistency of our data demonstrates the reproducibility and ease-of-use of such tests and suggests a potential role for their use in broad end-to-end QA initiatives. [ABSTRACT FROM AUTHOR]

Abstract Aim In this study, an accuracy survey of intensity-modulated radiation therapy (IMRT) and volumetric arc radiation therapy (VMAT) implementation in radiotherapy centers in Thailand was conducted. Background It is well recognized that there is a need for radiotherapy centers to evaluate the accuracy levels of their current practices, and use the related information to identify opportunities for future development. Materials and methods An end-to-end test using a CIRS thorax phantom was carried out at 8 participating centers. Based on each center's protocol for simulation and planning, linac-based IMRT or VMAT plans were generated following the IAEA (CRP E24017) guidelines. Point doses in the region of PTVs and OARs were obtained from 5 ionization chamber readings and the dose distribution from the radiochromic films. The global gamma indices of the measurement doses and the treatment planning system calculation doses were compared. Results The large majority of the RT centers (6/8) fulfilled the dosimetric goals, with the measured and calculated doses at the specification points agreeing within ±3% for PTV and ±5% for OARS. At 2 centers, TPS underestimated the lung doses by about 6% and spinal cord doses by 8%. The mean percentage gamma pass rates for the 8 centers were 98.29 ± 0.67% (for the 3%/3 mm criterion) and 96.72 ± 0.84% (for the 2%/2 mm criterion). Conclusions The 8 participating RT centers achieved a satisfactory quality level of IMRT/VMAT clinical implementation. [ABSTRACT FROM AUTHOR]

Purpose: One of the important developments in brachytherapy in recent years has been the clinical implementation of complex modern technical procedures. Today, 3D-imaging has become the standard procedure and it is used for contouring and precise position determination and reconstruction of used brachytherapy applicators. Treatment planning is performed on the basis of these imaging methods, followed by data transfer to the afterloading device. Therefore, checking the entire treatment chain is of high importance. In this work, we describe an end-to-end test for computed tomography (CT)-based brachytherapy with an high-dose-rate (HDR) afterloading device, which fulfills the recommendation of the German radiation-protection-commission. Material and methods: The treatment chain consists of a SOMATOM S64 CT scanner (Siemens Medical), the treatment planning system (TPS) BrachyVision v.13.7 (VMS), which utilizes the calculation formalism TG-43 and the Acuros algorithm v. 1.5.0 (VMS) as well as GammaMedplus HDR afterloader (VMS) using an Ir-192 source. Measurement setups for common brachytherapy applicators are defined in a water phantom, and the required PMMA applicator holders are developed. These setups are scanned with the CT and the data is imported into the TPS. Computed TPS reference dose values for significant points located on the side of the applicator are compared with dose measurements performed with a PinPoint 3D chamber 31016 (PTW Freiburg). Results: The deviations for the end-to-end test between computed and measured values are shown to be ≤ 5%, when using an implant needle or vaginal cylinder. Furthermore, it can be demonstrated that the test procedure provides reproducible results, while repositioning the applicators without carrying out a new CT-scan. Conclusions: The end-to-end test presented allows a practice-oriented realization for checking the whole treatment chain for HDR afterloading technique and CT-imaging. The presented phantom seems feasible for performing periodic system checks as well as to verify newly introduced brachytherapy techniques with sufficient accuracy. [ABSTRACT FROM AUTHOR]

• End-to-end tests in a dynamic respiratory thorax phantom revealed dose deviations up to 10%. • Largest deviations were observed for the smallest 1 cm diameter target. • Deviations were not highlighted by classical quality controls. • Calculations algorithms tend to underestimate the dose. The aim of this study is to perform patient quality controls and end-to-end tests for stereotactic VMAT lung treatment plans and to investigate the influence of various parameters on the results. 18 plans were defined by an experimental design methodology to cover a large variety of stereotactic VMAT lung treatments including different doses per fraction, target diameters, target movements and respiratory parameters. Plans were first controlled using portal dosimetry and a homogeneous static cylindrical phantom. End-to-end tests were then performed in a dynamic respiratory thorax phantom. Measurements were conducted with ionization chamber and films. Calculations were performed with the AcurosXB and AAA algorithms in 6 FFF. Portal dosimetry gave excellent gamma pass rates (greater than 97.1 %) and dose deviations between measurement and calculations in a homogeneous static phantom were smaller than 2 %. The methodology followed for comparing calculated and measured doses in a moving target was validated in static fields (largest deviation smaller than 2 %). End-to-end tests showed mean deviations of 1.9 %, 3.3 % and 6.6 % for the 3, 2 and 1 cm diameter's target respectively. Deviations increased for larger movements for the 1 cm lesion. End-to-end tests revealed that stereotactic VMAT lung treatment plans for moving targets can be delivered within 5 % for 3 and 2 cm diameter targets and amplitudes up to 1.5 cm. The AcurosXB and AAA algorithms however tend to underestimate the dose to the target. Even with satisfactory patient quality controls like portal dosimetry, extra care should be taken for GTV lesions smaller than 2 cm. [ABSTRACT FROM AUTHOR]

Purpose . Since January 2021, the Leksell ® Vantage head frame (V-frame) is used for Gamma Knife ® treatments in addition to the historical Leksell ® G-Frame known as the reference. The aim of this study was to compare the spatial accuracy of treatments with these two frames. Methods . Firstly, the constancy of the geometric accuracy of the system according to the Elekta quality assurance process was carried out during sixteen months with V and G-frames' adaptors. Then, End-to-end test was carried out with both V and G-frame using an anthropomorphic phantom and Gafchromic ® films. The overall precision of the radiation center was calculated as the displacement vector for a 4 mm collimator shot. Additionally, the Cone Beam Computed Tomography (CBCT) positioning system was used to assess the precision of the Leksell coordinates system defined by V-frames on 64 patients in comparison to G-frames for 46 patients. To ensure that patient's head movement was not possible during treatment with the V-frame, the High Definition Motion Management (HDMM) system was used and a final CBCT was performed at the end of the irradiation. Results . The QA constructor's tests done with the G-frame and V-frame adaptor gave similar results over sixteen months. End-to-end tests demonstrated that the mean positioning accuracy was 0.54 mm (SD of 0.14 mm) and 0.70 mm (SD of 0.14 mm) with V-frame and G-frame respectively. The displacement vector given by CBCT ranged from 0.02 to 1.05 mm with a mean value of 0.38 mm (SD of 0.18 mm) for the 64 V-framed patients and from 0 to 0.92 mm with a mean value of 0.31 mm (SD of 0.18 mm) for the 46 G-framed patients. The mean translation movement between the beginning and the end of the 64 treatments with V-frame was 0.08 mm (SD of 0.04 mm, maximum value of 0.19 mm). Conclusion . We estimated that V-frames are as precise as G-frames with a targeting accuracy of less than 1 mm., (© 2023 IOP Publishing Ltd.)

Background and purpose A methodology is presented to quantify the uncertainty associated with linear accelerator-based frameless intracranial stereotactic radiotherapy (SRT) combining end-to-end phantom tests and clinical data. Methods and materials The following steps of the SRT chain were analysed: planning computed tomography (CT) and magnetic resonance (MR) scans registration, target volume delineation, CT and cone beam CT (CBCT) registration and intrafraction-patient displacement. The overall accuracy was established with an end-to-end test. The measured uncertainties were combined, deriving the total systematic ( Σ T ) and random ( σ T ) error components, to estimate the GTV-PTV margin. Results The uncertainty in the MR-CT registration was on average 0.40 mm (averaged over AP, CC and LR directions). Rotational variations were smaller than 0.5° in all directions. Interobser variation in GTV delineation was on average 0.29 mm. The uncertainty in the CBCT-CT registration was on average 0.15 mm. Again, rotational variations were smaller than 0.5° in all directions. The systematic and random intrafraction displacement errors were on average 0.55 mm and 0.45 mm, respectively. The systematic and random positional errors from the end-to-end test were on average 0.49 mm and 0.53 mm, respectively. Combining these uncertainties resulted in an average Σ T = 0.9 mm and σ T = 0.7 mm and an average GTV-PTV margin of 2.8 mm. Conclusion This comprehensive methodology including end-to-end tests enabled a GTV-PTV margin calculation considering all sources of uncertainties. This generic method can also be used for other treatment sites. [ABSTRACT FROM AUTHOR]

Purpose: Spatial accuracy is most crucial when small targets like the trigeminal nerve are treated. Although current quality assurance procedures typically verify that individual apparatus, like the MRI scanner, CT scanner, Gamma Knife, etc., are meeting specifications, the cumulative error of all equipment and procedures combined may exceed safe margins. This study uses an end-to-end approach to assess the overall targeting errors that may have occurred in individual patients previously treated for trigeminal neuralgia. Methods: The trigeminal nerve is simulated by a 3 mm long, 3.175 mm (1/8 in.) diameter MRIcontrast filled cavity embedded within a PMMA plastic capsule. The capsule is positioned within the head frame such that the location of the cavity matches the Gamma Knife coordinates of an arbitrarily chosen, previously treated patient. Gafchromic EBT2 film is placed at the center of the cavity in coronal and sagittal orientations. The films are marked with a pinprick to identify the cavity center. Treatments are planned for radiation delivery with 4 mm collimators according to MRI and CT scans using the clinical localizer boxes and acquisition protocols. Shots are planned so that the 50% isodose surface encompasses the cavity. Following irradiation, the films are scanned and analyzed. Targeting errors are defined as the distance between the pinprick, which represents the intended target, and the centroid of the 50% isodose line, which is the center of the radiation field that was actually delivered. Results: Averaged over ten patient simulations, targeting errors along the x, y, and z coordinates (patient's left-to-right, posterior-to-anterior, and head-to-foot) were, respectively, -0.060 ± 0.363, -0.350 ± 0.253, and 0.348 ± 0.204 mm when MRI was used for treatment planning. Planning according to CT exhibited generally smaller errors, namely, 0.109 ± 0.167, -0.191 ± 0.144, and 0.211 ± 0.094 mm. The largest errors along individual axes in MRI- and CT-planned treatments were, respectively, -0.761 mm in the y-direction and 0.428 mm in the x-direction, well within safe limits. Conclusions: The highly accurate dose delivery was possible because the Gamma Knife, MRI scanner, and other equipment performed within tight limits and scans were acquired using the thinnest slices and smallest pixel sizes available. Had the individual devices performed only near the limits of their specifications, the cumulative error could have left parts of the trigeminal nerve undertreated. The presented end-to-end test gives assurance that patients had received the expected high quality treatment. End-to-end tests should become part of clinical practice. [ABSTRACT FROM AUTHOR]

Objective. In MR-guided radiotherapy (MRgRT) for prostate cancer treatments inter-fractional anatomy changes such as bladder and rectum fillings may be corrected by an online adaption of the treatment plan. To clinically implement such complex treatment procedures, however, specific end-to-end tests are required that are able to validate the overall accuracy of all treatment steps from pre-treatment imaging to dose delivery. Approach. In this study, an end-to-end test of a fractionated and online adapted MRgRT prostate irradiation was performed using the so-called ADAM-PETer phantom. The phantom was adapted to perform 3D polymer gel (PG) dosimetry in the prostate and rectum. Furthermore, thermoluminescence detectors (TLDs) were placed at the center and on the surface of the prostate for additional dose measurements as well as for an external dose renormalization of the PG. For the end-to-end test, a total of five online adapted irradiations were applied in sequence with different bladder and rectum fillings, respectively. Main results. A good agreement of measured and planned dose was found represented by highγ-index passing rates (3%/3mmcriterion) of the PG evaluation of98.9%in the prostate and93.7%in the rectum. TLDs used for PG renormalization at the center of the prostate showed a deviation of-2.3%. Significance. The presented end-to-end test, which allows for 3D dose verification in the prostate and rectum, demonstrates the feasibility and accuracy of fractionated and online-adapted prostate irradiations in presence of inter-fractional anatomy changes. Such tests are of high clinical importance for the commissioning of new image-guided treatment procedures such as online adaptive MRgRT., (© 2021 Institute of Physics and Engineering in Medicine.)

The introduction of real-time imaging by magnetic resonance guided linear accelerators (MR-Linacs) enabled adaptive treatments and gating on the tumor position. Different end-to-end tests monitored the accuracy of our MR-Linac during the first year of clinical operation. We report on the stability of these tests covering a static, adaptive and gating workflow. Film measurements showed gamma passing rates of 96.4% ± 3.4% for the static tests (five measurements) and for the two adaptive tests 98.9% and 99.99%, respectively (criterion 2%/2mm). The gated point dose measurements in the breathing phantom were 2.7% lower than in the static phantom., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2020 The Authors.)

Background and Purpose: Post-operative spine stereotactic body radiation therapy (SBRT) represents a significant challenge as there are many restrictions on beam geometry to avoid metal hardware as it surrounds the target volume. In this study, an international multi-institutional end-to-end test using an in-house spine phantom was developed and executed. The aim was to evaluate the impact of titanium spine hardware on planned and delivered dose for post-operative spine SBRT., Materials and Methods: Five centers performed simulation, planning and irradiation of the spine phantom, with/without titanium metal hardware (MB/B), following our pre-specified protocol. The doses were calculated using the centers' treatment planning system (TPS) and measured with radiophotoluminescent glass dosimeters (RPLDs) embedded within each phantom., Results: The dose differences between the RPLD measured and calculated doses in the target region were within ± 5% for both phantoms studied. Differences greater than 5% were observed for the spinal cord and the out-of-the target regions due to steeper dose gradient regions that are created in these plans. Dose measurements within ± 3% were observed between RPLDs that were embedded in MB and B inserts. For the spinal cord and the out-of-target regions surrounded by metal hardware, the dose measured using RPLDs was within 3% different near the titanium screws compared to the dose measured near only the metal rods., Conclusion: We have successfully performed the first multi-institutional end-to-end dose analysis using an in-house phantom built specifically for post-operative spine SBRT. The differences observed between the measured and planned doses in the presence of metal hardware were clinically insignificant., Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Dr. Arjun Sahgal has received honorarium for past educational seminars from Medtronic and Elekta AB and research grants from Elekta AB. Dr. Arjun Sahgal has participated on the medical advisory board for Varian Medical Systems and Merck. Dr. Arjun Sahgal has received honorarium for past educational seminars from Accuray and Medtronic., (© 2020 The Authors.)