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Xu Q, Fan J, Vinogradskiy Y, Chawla AK, Kubicek G, Yang H, Huynh K, LaCouture T, Grimm J, Nie W. Feasibility of patient-specific quality assurance (PSQA) for real-time robotic stereotactic body radiotherapy (SBRT) based on tumor motion traces. J Appl Clin Med Phys 2024; 25:e14352. [PMID: 38696697 PMCID: PMC11302821 DOI: 10.1002/acm2.14352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 01/30/2024] [Accepted: 03/07/2024] [Indexed: 05/04/2024] Open
Abstract
PURPOSE To design a patient specific quality assurance (PSQA) process for the CyberKnife Synchrony system and quantify its dosimetric accuracy using a motion platform driven by patient tumor traces with rotation. METHODS The CyberKnife Synchrony system was evaluated using a motion platform (MODUSQA) and a SRS MapCHECK phantom. The platform was programed to move in the superior-inferior (SI) direction based on tumor traces. The detector array housed by the StereoPhan was placed on the platform. Extra rotational angles in pitch (head down, 4.0° ± 0.15° or 1.2° ± 0.1°) were added to the moving phantom to examine robot capability of angle correction during delivery. A total of 15 Synchrony patients were performed SBRT PSQA on the moving phantom. All the results were benchmarked by the PSQA results based on static phantom. RESULTS For smaller pitch angles, the mean gamma passing rates were 99.75% ± 0.87%, 98.63% ± 2.05%, and 93.11% ± 5.52%, for 3%/1 mm, 2%/1 mm, and 1%/1 mm, respectively. Large discrepancy in the passing rates was observed for different pitch angles due to limited angle correction by the robot. For larger pitch angles, the corresponding mean passing rates were dropped to 93.00% ± 10.91%, 88.05% ± 14.93%, and 80.38% ± 17.40%. When comparing with the static phantom, no significant statistic difference was observed for smaller pitch angles (p = 0.1 for 3%/1 mm), whereas a larger statistic difference was observed for larger pitch angles (p < 0.02 for all criteria). All the gamma passing rates were improved, if applying shift and rotation correction. CONCLUSIONS The significance of this work is that it is the first study to benchmark PSQA for the CyberKnife Synchrony system using realistically moving phantoms with rotation. With reasonable delivery time, we found it may be feasible to perform PSQA for Synchrony patients with a realistic breathing pattern.
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Affiliation(s)
- Qianyi Xu
- Department of Advanced Radiation Oncology and Proton TherapyInova Schar Cancer InstituteFairfaxVirginiaUSA
- Department of Radiation OncologyThomas Jefferson UniversityPhiladelphiaPennsylvaniaUSA
| | - Jiajin Fan
- Department of Advanced Radiation Oncology and Proton TherapyInova Schar Cancer InstituteFairfaxVirginiaUSA
| | - Yevgeniy Vinogradskiy
- Department of Radiation OncologyThomas Jefferson UniversityPhiladelphiaPennsylvaniaUSA
| | - Ashish K. Chawla
- Department of Advanced Radiation Oncology and Proton TherapyInova Schar Cancer InstituteFairfaxVirginiaUSA
| | - Gregory Kubicek
- Department of Radiation OncologyUniversity of MiamiMiamiFloridaUSA
| | - Haihua Yang
- Department of Radiation OncologyTaizhou HospitalTaizhouZhejiangChina
| | - Kiet Huynh
- Department of Advanced Radiation Oncology and Proton TherapyInova Schar Cancer InstituteFairfaxVirginiaUSA
| | - Tamara LaCouture
- Department of Radiation OncologyThomas Jefferson UniversityPhiladelphiaPennsylvaniaUSA
| | - Jimm Grimm
- Department of Radiation OncologyWellstar Health SystemMariettaGeorgiaUSA
| | - Wei Nie
- Department of Advanced Radiation Oncology and Proton TherapyInova Schar Cancer InstituteFairfaxVirginiaUSA
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Liu M, Cygler JE, Dennis K, Vandervoort E. A dose perturbation tool for robotic radiosurgery: Experimental validation and application to liver lesions. J Appl Clin Med Phys 2022; 23:e13766. [PMID: 36094024 PMCID: PMC9680574 DOI: 10.1002/acm2.13766] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Revised: 07/09/2022] [Accepted: 08/04/2022] [Indexed: 11/07/2022] Open
Abstract
BACKGROUND An analytical tool is empirically validated and used to assess the delivered dose to liver lesions accounting for different types of errors in robotic radiosurgery treatment. MATERIAL AND METHODS A tool is proposed to estimate the target doses taking into account the translation, rotation, and deformation of a target. Translational errors are modeled as a spatial convolution of the planned dose with a probability distribution function derived from treatment data. Rotations are modeled by rotating the target volume about the imaging isocenter. Target deformation is simulated as an isotropic target expansion or contraction based on changes in inter-fiducial spacing. The estimated dose is validated using radiochromic film measurements in nine experimental conditions, including in-phase and out-of-phase internal-and-external breathing motion patterns, with and without uncorrectable rotations, and for homogenous and heterogeneous phantoms. The measured dose is compared to the perturbed and planned doses using gamma analyses. This proposed tool is applied to assess the dose coverage for liver treatments using D99/Rx where D99 and Rx are the minimum target and prescription doses, respectively. These metrics are used to evaluate plan robustness to different magnitudes of rotational errors. Case studies are presented to illustrate how to improve plan robustness against delivery errors. RESULTS In the experimental validations, measured dose agrees with the estimated dose at the 2%/2 mm level. When accounting for translational and rotational tracking residual errors using this tool, approximately one-fifth of targets are considered underdosed (D99/Rx < 1.0). If target expansion or contraction is modeled, approximately one-third of targets are underdosed. The dose coverage can be improved if treatments are planned following proposed guidelines. CONCLUSION The dose perturbation model can be used to assess dose delivery accuracy and investigate plan robustness to different types of errors.
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Affiliation(s)
- Ming Liu
- Department of Medical PhysicsThe Ottawa Hospital Cancer CenterOttawaCanada
- Department of PhysicsCarleton UniversityOttawaCanada
| | - Joanna E. Cygler
- Department of Medical PhysicsThe Ottawa Hospital Cancer CenterOttawaCanada
- Department of PhysicsCarleton UniversityOttawaCanada
- Division of Medical Physics, Department of RadiologyThe University of OttawaOttawaCanada
| | - Kristopher Dennis
- Division of Radiation OncologyThe Ottawa Hospital and the University of OttawaOttawaCanada
| | - Eric Vandervoort
- Department of Medical PhysicsThe Ottawa Hospital Cancer CenterOttawaCanada
- Department of PhysicsCarleton UniversityOttawaCanada
- Division of Medical Physics, Department of RadiologyThe University of OttawaOttawaCanada
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Liu M, Cygler JE, Vandervoort E. Patient-specific PTV margins for liver stereotactic body radiation therapy determined using support vector classification with an early warning system for margin adaptation. Med Phys 2020; 47:5172-5182. [PMID: 32740935 DOI: 10.1002/mp.14419] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Revised: 04/02/2020] [Accepted: 07/22/2020] [Indexed: 01/02/2023] Open
Abstract
PURPOSE An adaptive planning target volume (PTV) margin strategy incorporating a volumetric tracking error assessment after each fraction is proposed for robotic stereotactic body radiation therapy (SBRT) liver treatments. METHODS AND MATERIALS A supervised machine learning algorithm employing retrospective data, which emulates a dry-run session prior to planning, is used to investigate if motion tracking errors are <2 mm, and consequently, planning target volume (PTV) margins can be reduced. A fraction of data collected during the beginning of a treatment course emulates a dry-run session (mock) before planning. Twenty features are calculated using mock data and used for support vector classification (SVC). A treatment course is labeled as Class 1 if the maximum root-mean-square radial tracking error for all remaining fractions is below 2 mm, or Class 2 otherwise. We evaluate the classification using fivefold cross-validation, leave-one-out cross-validation, 500 repeated random subsampling cross-validation, and the receiver operating characteristic (ROC) metric. The classification is independently cross-validated on a cohort of 48 treatment plans for other anatomical sites. A per fraction assessment of volumetric tracking errors is performed for the standard 5 mm PTV margin (PTVstd ) for courses predicted as Class 2; or for a margin reduced by 2 mm (PTVstd-2mm ) for those predicted as Class 1. We perturb the gross tumor volume (GTV) by the tracking errors for each x-ray image acquisition and calculate the fractional GTV voxel occupancy probability (Pi ) inside the PTV for each treatment fraction i. For treatment courses classified as Class 1, an early warning system flags treatment courses having any Pi < 0.99, and the subsequent treatments are proposed to be replanned using PTVstd . RESULTS The classification accuracies are 0.84 ± 0.06 using fivefold cross-validation, and 0.77 when validated using an independent testing set (other anatomical sites). Eighty percent of treatment courses are correctly classified using leave-one-out cross-validation. The sensitivity, precision, specificity, F1 score, and accuracy are 0.81 ± 0.09, 0.85 ± 0.08, 0.80 ± 0.11, 0.83 ± 0.06, and 0.80 ± 0.07, respectively, using 500 repeated random subsampling cross-validation. The area under the curve for the ROC metric is 0.87 ± 0.05. The four most important features for classification are related to standard deviations of motion tracking errors, the linearity between the target location and external LED marker positions, and marker radial motion amplitudes. Eleven of 64 cases predicted to be of Class 1 have 0.96 < Pi < 0.99 for each treatment fraction, and require replanning using PTVstd . In comparison, the PTVstd always covers the perturbed GTVs with Pi > 0.99 for all patients. CONCLUSIONS Support vector classification is proposed for the classification of different motion tracking errors for patient courses based on a mock session before planning for SBRT liver treatments. It is feasible to implement patient-specific PTV margins in the clinic, assisted with an early warning system to flag treatment courses that require replanning using larger PTV margins in an adaptive treatment strategy.
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Affiliation(s)
- Ming Liu
- Department of Physics, Carleton University, Ottawa, ON, K1S 5B6, Canada
| | - Joanna E Cygler
- Department of Physics, Carleton University, Ottawa, ON, K1S 5B6, Canada.,Department of Medical Physics, The Ottawa Hospital Cancer Centre, Ottawa, ON, K1H 8L6, Canada.,Department of Radiology, University of Ottawa, Ottawa, ON, K1H 8L6, Canada
| | - Eric Vandervoort
- Department of Physics, Carleton University, Ottawa, ON, K1S 5B6, Canada.,Department of Medical Physics, The Ottawa Hospital Cancer Centre, Ottawa, ON, K1H 8L6, Canada.,Department of Radiology, University of Ottawa, Ottawa, ON, K1H 8L6, Canada
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Kawata K, Kamomae T, Oguchi H, Kawabata F, Okudaira K, Kawamura M, Ohtakara K, Itoh Y, Naganawa S. Evaluation of newly implemented dose calculation algorithms for multileaf collimator-based CyberKnife tumor-tracking radiotherapy. Med Phys 2020; 47:1391-1403. [PMID: 31913508 DOI: 10.1002/mp.14013] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Revised: 12/30/2019] [Accepted: 12/30/2019] [Indexed: 11/09/2022] Open
Abstract
PURPOSE In the previous treatment planning system (TPS) for CyberKnife (CK), multileaf collimator (MLC)-based treatment plans could be created only by using the finite-size pencil beam (FSPB) algorithm. Recently, a new TPS, including the FSPB with lateral scaling option (FSPB+) and Monte Carlo (MC) algorithms, was developed. In this study, we performed basic and clinical end-to-end evaluations for MLC-based CK tumor-tracking radiotherapy using the MC, FSPB+, and FSPB. METHODS Water- and lung-equivalent slab phantoms were combined to obtain the percentage depth dose (PDD) and off-center ratio (OCR). The CK M6 system and Precision TPS were employed, and PDDs and OCRs calculated by the MC, FSPB+, and FSPB were compared with the measured doses obtained for 30.8 × 30.8 mm2 and 60.0 × 61.6 mm2 fields. A lung motion phantom was used for clinical evaluation and MLC-based treatment plans were created using the MC. The doses were subsequently recalculated using the FSPB+ and FSPB, while maintaining the irradiation parameters. The calculated doses were compared with the doses measured using a microchamber (for target doses) or a radiochromic film (for dose profiles). The dose volume histogram (DVH) indices were compared for all plans. RESULTS In homogeneous and inhomogeneous phantom geometries, the PDDs calculated by the MC and FSPB+ agreed with the measurements within ±2.0% for the region between the surface and a depth of 250 mm, whereas the doses calculated by the FSPB in the lung-equivalent phantom region were noticeably higher than the measurements, and the maximum dose differences were 6.1% and 4.4% for the 30.8 × 30.8 mm2 and 60.0 × 61.6 mm2 fields, respectively. The maximum distance to agreement values of the MC, FSPB+, and FSPB at the penumbra regions of OCRs were 1.0, 0.6, and 1.1 mm, respectively, but the best agreement was obtained between the MC-calculated curve and measurements at the boundary of the water- and lung-equivalent slabs, compared with those of the FSPB+ and FSPB. For clinical evaluations using the lung motion phantom, under the static motion condition, the dose errors measured by the microchamber were -1.0%, -1.9%, and 8.8% for MC, FSPB+, and FSPB, respectively; their gamma pass rates for the 3%/2 mm criterion comparing to film measurement were 98.4%, 87.6%, and 31.4% respectively. Under respiratory motion conditions, there was no noticeable decline in the gamma pass rates. In the DVH indices, for most of the gross tumor volume and planning target volume, significant differences were observed between the MC and FSPB, and between the FSPB+ and FSPB. Furthermore, significant differences were observed for lung Dmean , V15 Gy , and V20 Gy between the MC, FSPB+, and FSPB. CONCLUSIONS The results indicate that the doses calculated using the MC and FSPB+ differed remarkably in inhomogeneous regions, compared with the FSPB. Because the MC was the most consistent with the measurements, it is recommended for final dose calculations in inhomogeneous regions such as the lung. Furthermore, the sufficient accuracy of dose delivery using MLC-based tumor-tracking radiotherapy by CK was demonstrated for clinical implementation.
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Affiliation(s)
- Kohei Kawata
- Department of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya, Aichi, 461-8673, Japan
| | - Takeshi Kamomae
- Department of Radiology, Nagoya University Graduate School of Medicine, Nagoya, Aichi, 466-8550, Japan
| | - Hiroshi Oguchi
- Department of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya, Aichi, 461-8673, Japan
| | - Fumitaka Kawabata
- Department of Radiological Technology, Nagoya University Hospital, Nagoya, Aichi, 466-8560, Japan
| | - Kuniyasu Okudaira
- Department of Radiological Technology, Nagoya University Hospital, Nagoya, Aichi, 466-8560, Japan
| | - Mariko Kawamura
- Department of Radiology, Nagoya University Graduate School of Medicine, Nagoya, Aichi, 466-8550, Japan
| | - Kazuhiro Ohtakara
- Department of Radiology, Nagoya University Graduate School of Medicine, Nagoya, Aichi, 466-8550, Japan
| | - Yoshiyuki Itoh
- Department of Radiology, Nagoya University Graduate School of Medicine, Nagoya, Aichi, 466-8550, Japan
| | - Shinji Naganawa
- Department of Radiology, Nagoya University Graduate School of Medicine, Nagoya, Aichi, 466-8550, Japan
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Akino Y, Shiomi H, Sumida I, Isohashi F, Seo Y, Suzuki O, Tamari K, Otani K, Higashinaka N, Hayashida M, Mabuchi N, Ogawa K. Impacts of respiratory phase shifts on motion-tracking accuracy of the CyberKnife Synchrony™ Respiratory Tracking System. Med Phys 2019; 46:3757-3766. [PMID: 30943311 DOI: 10.1002/mp.13523] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Revised: 02/14/2019] [Accepted: 03/26/2019] [Indexed: 12/25/2022] Open
Abstract
PURPOSE The SynchronyTM Respiratory Tracking System (SRTS) component of the CyberKnife® Robotic Radiosurgery System (Accuray, Inc., Sunnyvale CA) enables real-time tracking of moving targets by modeling the correlation between the targets and external surrogate light-emitting diode (LED) markers placed on the patient's chest. Previous studies reported some cases with respiratory phase shifts between lung tumor and chest wall motions. In this study, the impacts of respiratory phase shifts on the motion-tracking accuracy of the SRTS were investigated. METHODS A plastic scintillator was used to detect the position of the x-ray beams. The scintillation light was recorded using a camera in a dark room. A moving phantom moved a U-shaped frame on the scintillator with a 4th power of sinusoidal functions. Three metallic markers for motion tracking and four fluorescent tapes were attached to the frame. The fluorescent tapes were used to identify phantom position and respiratory phase for each video frame. The beam positions collected, when considered relative to the phantom motion, represent the degree of tracking error. Beam position was calculated by adding error value to phantom position. Motions with respiratory phase shifts between the target and an extra stage mimicking chest wall motion were also tested for LED markers. Log files of the SRTS were analyzed to evaluate correlation errors. RESULTS When target and LED marker motions were synchronized with a respiratory cycle of 4 s, the maximum tracking errors for 90% and 95% of beam-on time were 1.0 mm and 1.2 mm, respectively. The frequency of tracking errors increased when LED marker motion phase preceded target motion. Tracking errors that corresponded to 90% beam-on time were within 2.4 mm for 5-15% of phase shifts. In contrast, the tracking errors were very large when the LED marker delayed to the target motions; the maximum errors of 90% beam-on time were 3.0, 3.8, and 7.5 mm for 5%, 10%, and 15% of phase shifts, respectively. The patterns of the tracking errors derived from the scintillation light were very similar to those of the correlation data of the SRTS derived from the log files, indicating that the tracking errors caused mainly due to the errors in modeling the correlation data. With long respiratory cycle of 6 s, the tracking errors were significantly decreased; the maximum tracking errors for 95% beam-on time were 1.6 mm and 2.2 mm for early and delayed LED motion. CONCLUSION We have investigated the motion-tracking accuracy of the CyberKnife SRTS for cases with the respiratory phase shift between the target and the LED marker. The maximum tracking errors for 90% probability were within 2.4 mm when the target delays to the LED markers. When LED marker delays, however, very large tracking errors were observed. With a long respiratory cycle, the tracking errors were greatly improved to less than 2.2 mm. Coaching slow breathing will be useful for accurate motion tracking radiotherapy.
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Affiliation(s)
- Yuichi Akino
- Oncology Center, Osaka University Hospital, Suita, Osaka, 565-0871, Japan.,Soseikai CyberKnife Center, Fushimi-ku, Kyoto, 612-8248, Japan
| | - Hiroya Shiomi
- Soseikai CyberKnife Center, Fushimi-ku, Kyoto, 612-8248, Japan.,Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka, 565-0871, Japan
| | - Iori Sumida
- Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka, 565-0871, Japan
| | - Fumiaki Isohashi
- Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka, 565-0871, Japan
| | - Yuji Seo
- Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka, 565-0871, Japan
| | - Osamu Suzuki
- Department of Carbon Ion Radiotherapy, Osaka University Graduate School of Medicine, Suita, Osaka, 565-0871, Japan
| | - Keisuke Tamari
- Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka, 565-0871, Japan
| | - Keisuke Otani
- Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka, 565-0871, Japan
| | | | - Miori Hayashida
- Soseikai CyberKnife Center, Fushimi-ku, Kyoto, 612-8248, Japan
| | | | - Kazuhiko Ogawa
- Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka, 565-0871, Japan
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Liu M, Cygler JE, Vandervoort E. Geometrical tracking accuracy and appropriate PTV margins for robotic radiosurgery of liver lesions by SBRT. Acta Oncol 2019; 58:906-915. [PMID: 30799669 DOI: 10.1080/0284186x.2019.1578896] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Purpose: To assess the geometrical accuracy and estimate adequate PTV margins for liver treatments using the Synchrony respiratory tracking system. Material and methods: Treatment log files are analyzed for 72 liver patients to assess tracking accuracy. The tracking error is calculated as the quadratic sum of the correlation, the predictor and the beam positioning errors. Treatment target rotations and rigid body errors reported by the system are also evaluated. The impact of uncorrected rotations is assessed by rotating the planned dose distribution and reassessing target coverage. Total PTV margins are estimated by summing in quadrature tracking errors and rigid body errors. Relationships are explored between tracking errors, model linearity and motion amplitudes of internal and external markers. Results: Margins of 3, 2, 2 mm in SUP-INF, LT-RT and ANT-POST directions, respectively, are sufficient to account for tracking and beam positioning errors for 95% of patients. If rigid body error is also considered, margins increase to 4 mm isotropic. Rotations could not be corrected for 92% of patients due to imperfect fiducial implantation and limitations in the magnitude of corrections that the system can apply. Uncorrected rotations would lead to average estimated dose reductions of 2.7% ± 5.8% of the prescribed dose for D99 of GTVs (5 mm PTV expansion) in which the target was well covered in the original plan (28 of 31 GTVs). 80% of tracking models exhibit near linear correlation between internal and external marker motions with small tracking errors (<2.2 mm). Conclusions: Isotropic PTV margins considering tracking errors and target rigid body errors could be used for liver SBRT treatments if rotational corrections can be calculated accurately so that systematic rotational offsets can be avoided. The linearity of the internal and external breathing motions might be useful for other types of treatment modalities for liver cancer.
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Affiliation(s)
- Ming Liu
- Department of Physics, Carleton University, Ottawa, Canada
| | - Joanna E. Cygler
- Department of Physics, Carleton University, Ottawa, Canada
- Department of Medical Physics, The Ottawa Hospital Cancer Centre, Ottawa, Canada
- Department of Radiology, University of Ottawa, Ottawa, Canada
| | - Eric Vandervoort
- Department of Physics, Carleton University, Ottawa, Canada
- Department of Medical Physics, The Ottawa Hospital Cancer Centre, Ottawa, Canada
- Department of Radiology, University of Ottawa, Ottawa, Canada
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