302 results on '"Feygelman, Vladimir"'
Search Results
2. Habitat escalated adaptive therapy (HEAT): a phase 2 trial utilizing radiomic habitat-directed and genomic-adjusted radiation dose (GARD) optimization for high-grade soft tissue sarcoma
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Naghavi, Arash O., Bryant, J. M., Kim, Youngchul, Weygand, Joseph, Redler, Gage, Sim, Austin J., Miller, Justin, Coucoules, Kaitlyn, Michael, Lauren Taylor, Gloria, Warren E., Yang, George, Rosenberg, Stephen A., Ahmed, Kamran, Bui, Marilyn M., Henderson-Jackson, Evita B., Lee, Andrew, Lee, Caitlin D., Gonzalez, Ricardo J., Feygelman, Vladimir, Eschrich, Steven A., Scott, Jacob G., Torres-Roca, Javier, Latifi, Kujtim, Parikh, Nainesh, and Costello, James
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- 2024
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3. Review on high spatial resolution dosimetry with pixelated semiconductor detectors for radiation therapy
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Filipev, Ilia, Paino, Jason, Poder, Joel, Cutajar, Dean, Hardcastle, Nicholas, Guatelli, Susanna, Petasecca, Marco, Lerch, Michael, Feygelman, Vladimir, Kron, Tomas, and Rosenfeld, Anatoly
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- 2024
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4. Novel Definitive Hypofractionated Accelerated Radiation Dose-painting (HARD) for Unresected Soft Tissue Sarcomas
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Bryant, John Michael, Mills, Matthew N., Yang, George Q., Liveringhouse, Casey, Palm, Russell, Johnstone, Peter A., Miller, Justin T., Latifi, Kujtim, Feygelman, Vladimir, and Naghavi, Arash O.
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- 2024
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5. Novel Postoperative Hypofractionated Accelerated Radiation Dose-Painting Approach for Soft Tissue Sarcoma
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Mills, Matthew, Miller, Justin, Liveringhouse, Casey, Bryant, John M., Kawahara, Yuki, Feygelman, Vladimir, Latifi, Kujtim, Yang, George, Johnstone, Peter A., and Naghavi, Arash O.
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- 2024
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6. Universal evaluation of MLC models in treatment planning systems based on a common set of dynamic tests
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Saez, Jordi, Bar-Deroma, Raquel, Bogaert, Evelien, Cayez, Romain, Chow, Tom, Clark, Catharine H., Esposito, Marco, Feygelman, Vladimir, Monti, Angelo F., Garcia-Miguel, Julia, Gershkevitsh, Eduard, Goossens, Jo, Herrero, Carmen, Hussein, Mohammad, Khamphan, Catherine, Kierkels, Roel G.J., Lechner, Wolfgang, Lemire, Matthieu, Nevelsky, Alexander, Nguyen, Daniel, Paganini, Lucia, Pasler, Marlies, Fernando Pérez Azorín, José, Ramos Garcia, Luis Isaac, Russo, Serenella, Shakeshaft, John, Vieillevigne, Laure, and Hernandez, Victor
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- 2023
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7. Magnetic Resonance-Guided Stereotactic Body Radiation Therapy/Hypofractionated Radiation therapy for Metastatic and Primary Central and Ultracentral Lung Lesions
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Sandoval, Maria L., Sim, Austin J., Bryant, John M., Bhandari, Menal, Wuthrick, Evan J., Perez, Bradford A., Dilling, Thomas J., Redler, Gage, Andreozzi, Jacqueline, Nardella, Louis, Feygelman, Vladimir, Latifi, Kujtim, and Rosenberg, Stephen A.
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- 2023
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8. A Practical Workflow for Magnetic Resonance–Guided Stereotactic Body Radiation Therapy to the Pancreas
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Sim, Austin J., Hoffe, Sarah E., Latifi, Kujtim, Palm, Russell F., Feygelman, Vladimir, Leuthold, Susan, Dookhoo, Marsha, Dennett, Maria, Rosenberg, Stephen A., and Frakes, Jessica M.
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- 2023
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9. Consensus Quality Measures and Dose Constraints for Head and Neck Cancer with an emphasis on Oropharyngeal and Laryngeal Cancer from the Veterans Affairs Radiation Oncology Quality Surveillance Program and American Society for Radiation Oncology Expert Panel
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Katsoulakis, Evangelia, Kudner, Randi, Chapman, Christina, Park, John, Puckett, Lindsay, Solanki, Abhi, Kapoor, Rishabh, Hagan, Michael, Kelly, Maria, Palta, Jatinder, Tishler, Roy, Hitchcock, Ying, Chera, Bhisham, Feygelman, Vladimir, Walker, Gary, Sher, David, Kujundzic, Ksenija, Wilson, Emily, Dawes, Samantha, Yom, Sue S., and Harrison, Louis
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- 2022
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10. MR-guided stereotactic body radiation therapy for intracardiac and pericardial metastases
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Sim, Austin J., Palm, Russell F., DeLozier, Kirby B., Feygelman, Vladimir, Latifi, Kujtim, Redler, Gage, Washington, Iman R., Wuthrick, Evan J., and Rosenberg, Stephen A.
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- 2020
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11. Essentially unedited deep-learning-based OARs are suitable for rigorous oropharyngeal and laryngeal cancer treatment planning.
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Jihye Koo, Caudell, Jimmy, Latifi, Kujtim, Moros, Eduardo G., and Feygelman, Vladimir
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LARYNGEAL cancer ,OROPHARYNGEAL cancer ,CANCER treatment ,PHYSICIANS - Abstract
Quality of organ at risk (OAR) autosegmentation is often judged by concordance metrics against the human-generated gold standard.However, the ultimate goal is the ability to use unedited autosegmented OARs in treatment planning,while maintaining the plan quality.We tested this approach with head and neck (HN) OARs generated by a prototype deep-learning (DL) model on patients previously treated for oropharyngeal and laryngeal cancer. Forty patients were selected, with all structures delineated by an experienced physician. For each patient, a set of 13 OARs were generated by the DL model. Each patient was re-planned based on original targets and unedited DL-produced OARs.The new dose distributions were then applied back to the manually delineated structures. The target coverage was evaluated with inhomogeneity index (II) and the relative volume of regret. For the OARs, Dice similarity coefficient (DSC) of areas under the DVH curves, individual DVH objectives, and composite continuous plan quality metric (PQM) were compared. The nearly identical primary target coverage for the original and re-generated plans was achieved, with the same II and relative volume of regret values. The average DSC of the areas under the corresponding pairs of DVH curves was 0.97 ± 0.06. The number of critical DVH points which met the clinical objectives with the dose optimized on autosegmented structures but failed when evaluated on the manual ones was 5 of 896 (0.6%). The average OAR PQM score with the re-planned dose distributions was essentially the same when evaluated either on the autosegmented or manual OARs. Thus, rigorous HN treatment planning is possible with OARs segmented by a prototype DL algorithm with minimal, if any, manual editing. [ABSTRACT FROM AUTHOR]
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- 2024
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12. 4DCT-Derived Ventilation Distribution Reproducibility Over Time
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Zhang, Geoffrey G., Latifi, Kujtim, Feygelman, Vladimir, Dilling, Thomas J., Moros, Eduardo G., Diniz Junqueira Barbosa, Simone, Series editor, Chen, Phoebe, Series editor, Du, Xiaoyong, Series editor, Filipe, Joaquim, Series editor, Kara, Orhun, Series editor, Kotenko, Igor, Series editor, Liu, Ting, Series editor, Sivalingam, Krishna M., Series editor, Washio, Takashi, Series editor, Fred, Ana, editor, and Gamboa, Hugo, editor
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- 2017
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13. Quantitatively Excessive Normal Tissue Toxicity and Poor Target Coverage in Postoperative Lung Cancer Radiotherapy Meta-analysis
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Abuodeh, Yazan, Naghavi, Arash O., Echevarria, Michelle, DeMarco, MaryLou, Tonner, Brian, Feygelman, Vladimir, Stevens, Craig W., Perez, Bradford A., and Dilling, Thomas J.
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- 2018
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14. A head and neck treatment planning strategy for a CBCT‐guided ring‐gantry online adaptive radiotherapy system.
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Nasser, Nour, Yang, George Q., Koo, Jihye, Bowers, Mark, Greco, Kevin, Feygelman, Vladimir, Moros, Eduardo G., Caudell, Jimmy J., and Redler, Gage
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GOAL (Psychology) ,RADIOTHERAPY ,CONE beam computed tomography ,VOLUMETRIC-modulated arc therapy - Abstract
Purpose: A planning strategy was developed and the utility of online‐adaptation with the Ethos CBCT‐guided ring‐gantry adaptive radiotherapy (ART) system was evaluated using retrospective data from Head‐and‐neck (H&N) patients that required clinical offline adaptation during treatment. Methods: Clinical data were used to re‐plan 20 H&N patients (10 sequential boost (SEQ) with separate base and boost plans plus 10 simultaneous integrated boost (SIB)). An optimal approach, robust to online adaptation, for Ethos‐initial plans using clinical goal prioritization was developed. Anatomically‐derived isodose‐shaping helper structures, air‐density override, goals for controlling hotspot location(s), and plan normalization were investigated. Online adaptation was simulated using clinical offline adaptive simulation‐CTs to represent an on‐treatment CBCT. Dosimetric comparisons were based on institutional guidelines for Clinical‐initial versus Ethos‐initial plans and Ethos‐scheduled versus Ethos‐adapted plans. Timing for five components of the online adaptive workflow was analyzed. Results: The Ethos H&N planning approach generated Ethos‐initial SEQ plans with clinically comparable PTV coverage (average PTVHigh V100% = 98.3%, Dmin,0.03cc = 97.9% and D0.03cc = 105.5%) and OAR sparing. However, Ethos‐initial SIB plans were clinically inferior (average PTVHigh V100% = 96.4%, Dmin,0.03cc = 93.7%, D0.03cc = 110.6%). Fixed‐field IMRT was superior to VMAT for 93.3% of plans. Online adaptation succeeded in achieving conformal coverage to the new anatomy in both SEQ and SIB plans that was even superior to that achieved in the initial plans (which was due to the changes in anatomy that simplified the optimization). The average adaptive workflow duration for SIB, SEQ base and SEQ boost was 30:14, 22.56, and 14:03 (min: sec), respectively. Conclusions: With an optimal planning approach, Ethos efficiently auto‐generated dosimetrically comparable and clinically acceptable initial SEQ plans for H&N patients. Initial SIB plans were inferior and clinically unacceptable, but adapted SIB plans became clinically acceptable. Online adapted plans optimized dose to new anatomy and maintained target coverage/homogeneity with improved OAR sparing in a time‐efficient manner. [ABSTRACT FROM AUTHOR]
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- 2023
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15. Treatment of Central Nervous System Tumors on Combination MR-Linear Accelerators: Review of Current Practice and Future Directions.
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Bryant, John Michael, Doniparthi, Ajay, Weygand, Joseph, Cruz-Chamorro, Ruben, Oraiqat, Ibrahim M., Andreozzi, Jacqueline, Graham, Jasmine, Redler, Gage, Latifi, Kujtim, Feygelman, Vladimir, Rosenberg, Stephen A., Yu, Hsiang-Hsuan Michael, and Oliver, Daniel E.
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PARTICLE accelerators ,CENTRAL nervous system tumors ,CANCER patients ,CHEMORADIOTHERAPY ,RADIOTHERAPY - Abstract
Simple Summary: Magnetic resonance imaging (MRI) has several advantages over computerized tomography (CT) in the treatment planning of central nervous system (CNS) malignancies. The adoption of hybrid MRI and linear accelerators (MRLs) has allowed for more effective tumor control and reduced unnecessary neurotoxicity through precise daily adaptations. In this review, we provide a summary of the evidence for MRLs in the management of various CNS tumors. Additionally, we discuss the potential of multiparametric MRI and genomically guided radiotherapy to enhance patient outcomes. Magnetic resonance imaging (MRI) provides excellent visualization of central nervous system (CNS) tumors due to its superior soft tissue contrast. Magnetic resonance-guided radiotherapy (MRgRT) has historically been limited to use in the initial treatment planning stage due to cost and feasibility. MRI-guided linear accelerators (MRLs) allow clinicians to visualize tumors and organs at risk (OARs) directly before and during treatment, a process known as online MRgRT. This novel system permits adaptive treatment planning based on anatomical changes to ensure accurate dose delivery to the tumor while minimizing unnecessary toxicity to healthy tissue. These advancements are critical to treatment adaptation in the brain and spinal cord, where both preliminary MRI and daily CT guidance have typically had limited benefit. In this narrative review, we investigate the application of online MRgRT in the treatment of various CNS malignancies and any relevant ongoing clinical trials. Imaging of glioblastoma patients has shown significant changes in the gross tumor volume over a standard course of chemoradiotherapy. The use of adaptive online MRgRT in these patients demonstrated reduced target volumes with cavity shrinkage and a resulting reduction in radiation dose to uninvolved tissue. Dosimetric feasibility studies have shown MRL-guided stereotactic radiotherapy (SRT) for intracranial and spine tumors to have potential dosimetric advantages and reduced morbidity compared with conventional linear accelerators. Similarly, dosimetric feasibility studies have shown promise in hippocampal avoidance whole brain radiotherapy (HA-WBRT). Next, we explore the potential of MRL-based multiparametric MRI (mpMRI) and genomically informed radiotherapy to treat CNS disease with cutting-edge precision. Lastly, we explore the challenges of treating CNS malignancies and special limitations MRL systems face. [ABSTRACT FROM AUTHOR]
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- 2023
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16. Commissioning Compensator-Based IMRT with a Flattening Filter Free Beam
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Robinson, Joshua, Opp, Daniel, Zhang, Geoffrey, Cashon, Ken, Kozelka, Jakub, Hunt, Dylan, Walker, Luke, Hoffe, Sarah, Shridhar, Ravi, Feygelman, Vladimir, and Long, Mian, editor
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- 2013
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17. Monte Carlo Study of Dose Difference in Electron Conformal Therapy Planning Introduced by Bolus Material Approximation
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Zhang, Ray R., Feygelman, Vladimir, Harris, Eleanor, Moros, Eduardo, Li, Weiqi, Zhang, Geoffrey G., and Long, Mian, editor
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- 2013
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18. Monte Carlo comparison of superficial dose between flattening filter free and flattened beams
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Javedan, Khosrow, Feygelman, Vladimir, Zhang, Ray R., Moros, Eduardo G., Correa, Candace R., Trotti, Andy, Li, Weiqi, and Zhang, Geoffrey G.
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- 2014
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19. Study of 201 Non-Small Cell Lung Cancer Patients Given Stereotactic Ablative Radiation Therapy Shows Local Control Dependence on Dose Calculation Algorithm
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Latifi, Kujtim, Oliver, Jasmine, Baker, Ryan, Dilling, Thomas J., Stevens, Craig W., Kim, Jongphil, Yue, Binglin, DeMarco, MaryLou, Zhang, Geoffrey G., Moros, Eduardo G., and Feygelman, Vladimir
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- 2014
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20. Cross-validation of two commercial methods for volumetric high-resolution dose reconstruction on a phantom for non-coplanar VMAT beams
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Feygelman, Vladimir, Stambaugh, Cassandra, Opp, Daniel, Zhang, Geoffrey, Moros, Eduardo G., and Nelms, Benjamin E.
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- 2014
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21. Stability of endoscopic ultrasound-guided fiducial marker placement for esophageal cancer target delineation and image-guided radiation therapy
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Fernandez, Daniel C., Hoffe, Sarah E., Barthel, James S., Vignesh, Shivakumar, Klapman, Jason B., Harris, Cynthia, Almhanna, Khaldoun, Biagioli, Matthew C., Meredith, Kenneth L., Feygelman, Vladimir, Rao, Nikhil G., and Shridhar, Ravi
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- 2013
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22. 2499: Hospitalization and dose to Middle Constrictor and Parotid during CRT for Oropharynx Cancer
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Caudell, Jimmy, Koo, Jihye, Yang, George, Echevarria, Michelle, and Feygelman, Vladimir
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- 2024
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23. A method for a priori estimation of best feasible DVH for organs-at-risk: Validation for head and neck VMAT planning
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Ahmed, Saeed, Nelms, Benjamin, Gintz, Dawn, Caudell, Jimmy, Zhang, Geoffrey, Moros, Eduardo G., and Feygelman, Vladimir
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- 2017
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24. Sensitivity of Image Features to Noise in Conventional and Respiratory-Gated PET/CT Images of Lung Cancer: Uncorrelated Noise Effects
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Oliver, Jasmine A., Budzevich, Mikalai, Hunt, Dylan, Moros, Eduardo G., Latifi, Kujtim, Dilling, Thomas J., Feygelman, Vladimir, and Zhang, Geoffrey
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- 2017
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25. The future of MRI in radiation therapy belongs to integrated MRI-linac systems, not the standalone MRI-Sim
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Feygelman, Vladimir, Lohr, Frank, and Orton, Colin G.
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- 2017
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26. Superficial and peripheral dose in compensator‐based FFF beam IMRT
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Zhang, Daniel G., Feygelman, Vladimir, Moros, Eduardo G., Latifi, Kujtim, Hoffe, Sarah, Frakes, Jessica, and Zhang, Geoffrey G.
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- 2017
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27. Stereotactic Magnetic Resonance-Guided Adaptive and Non-Adaptive Radiotherapy on Combination MR-Linear Accelerators: Current Practice and Future Directions.
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Bryant, John Michael, Weygand, Joseph, Keit, Emily, Cruz-Chamorro, Ruben, Sandoval, Maria L., Oraiqat, Ibrahim M., Andreozzi, Jacqueline, Redler, Gage, Latifi, Kujtim, Feygelman, Vladimir, and Rosenberg, Stephen A.
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PARTICLE accelerators ,CONNECTIVE tissues ,MAGNETIC resonance imaging ,PATIENT-centered care ,TREATMENT effectiveness ,RADIATION doses ,DRUG synergism ,TUMORS ,RADIOSURGERY ,MEDICAL practice ,COMPUTER-assisted image analysis (Medicine) - Abstract
Simple Summary: Stereotactic body radiotherapy (SBRT) is an effective radiation therapy technique that heavily relies upon daily image guidance to achieve the necessary precision. Magnetic resonance imaging (MRI) offers significant advantages over computed tomography (CT), which has traditionally been used for daily image guidance for SBRT. Hybrid MRI and linear accelerators (MRLs) allow for the delivery of stereotactic MR-guided adaptive radiotherapy (SMART) and improve patient outcomes for many types of tumors. In this review, we summarized the evidence for SMART as it related to ablative treatments and explored how multi-parametric MRIs could continue to improve patient outcomes. Stereotactic body radiotherapy (SBRT) is an effective radiation therapy technique that has allowed for shorter treatment courses, as compared to conventionally dosed radiation therapy. As its name implies, SBRT relies on daily image guidance to ensure that each fraction targets a tumor, instead of healthy tissue. Magnetic resonance imaging (MRI) offers improved soft-tissue visualization, allowing for better tumor and normal tissue delineation. MR-guided RT (MRgRT) has traditionally been defined by the use of offline MRI to aid in defining the RT volumes during the initial planning stages in order to ensure accurate tumor targeting while sparing critical normal tissues. However, the ViewRay MRIdian and Elekta Unity have improved upon and revolutionized the MRgRT by creating a combined MRI and linear accelerator (MRL), allowing MRgRT to incorporate online MRI in RT. MRL-based MR-guided SBRT (MRgSBRT) represents a novel solution to deliver higher doses to larger volumes of gross disease, regardless of the proximity of at-risk organs due to the (1) superior soft-tissue visualization for patient positioning, (2) real-time continuous intrafraction assessment of internal structures, and (3) daily online adaptive replanning. Stereotactic MR-guided adaptive radiation therapy (SMART) has enabled the safe delivery of ablative doses to tumors adjacent to radiosensitive tissues throughout the body. Although it is still a relatively new RT technique, SMART has demonstrated significant opportunities to improve disease control and reduce toxicity. In this review, we included the current clinical applications and the active prospective trials related to SMART. We highlighted the most impactful clinical studies at various tumor sites. In addition, we explored how MRL-based multiparametric MRI could potentially synergize with SMART to significantly change the current treatment paradigm and to improve personalized cancer care. [ABSTRACT FROM AUTHOR]
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- 2023
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28. Impact of dose on lung ventilation change calculated from 4D-CT using deformable image registration in lung cancer patients treated with SBRT
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Latifi, Kujtim, Dilling, Thomas J., Feygelman, Vladimir, Moros, Eduardo G., Stevens, Craig W., Montilla-Soler, Jaime L., and Zhang, Geoffrey G.
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- 2015
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29. Re-Planning for Compensator-Based IMRT with Original Compensators
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Zhang, Geoffrey, Feygelman, Vladimir, Stevens, Craig, Li, Weiqi, Leuthold, Susan, Springett, Gregory, and Hoffe, Sarah
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- 2011
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30. Motion-weighted target volume and dose-volume histogram: A practical approximation of four-dimensional planning and evaluation
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Zhang, Geoffrey, Feygelman, Vladimir, Huang, Tzung-Chi, Stevens, Craig, Li, Weiqi, and Dilling, Thomas
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- 2011
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31. Adaptive hypofractionted and stereotactic body radiotherapy for lung tumors with real-time MRI guidance.
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Bryant, John M., Sim, Austin J., Feygelman, Vladimir, Latifi, Kujtim, and Rosenberg, Stephen A.
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LUNG tumors ,STEREOTACTIC radiotherapy ,IMAGE-guided radiation therapy ,MAGNETIC resonance imaging ,TECHNOLOGICAL innovations - Abstract
The treatment of central and ultracentral lung tumors with radiotherapy remains an ongoing clinical challenge. The risk of Grade 5 toxicity with ablative radiotherapy doses to these high-risk regions is significant as shown in recent prospective studies. Magnetic resonance (MR) image-guided adaptive radiotherapy (MRgART) is a new technology and may allow the delivery of ablative radiotherapy to these high-risk regions safely. MRgART is able to achieve this by utilizing small treatment margins, real-time gating/tracking and on-table plan adaptation to maintain dose to the tumor but limit dose to critical structures. The process of MRgART is complex and has nuances and challenges for the treatment of lung tumors. We outline the critical steps needed for appropriate delivery of MRgART for lung tumors safely and effectively. [ABSTRACT FROM AUTHOR]
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- 2023
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32. Evaluation of a 3D Diode Array Dosimeter for Helical Tomotherapy Delivery QA
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Feygelman, Vladimir, Opp, D., Javedan, K., Saini, A.J., and Zhang, G.
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- 2010
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33. Generation of Composite Dose and Biological Effective Dose (BED) Over Multiple Treatment Modalities and Multistage Planning Using Deformable Image Registration
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Zhang, Geoffrey, Huang, Tzung-Chi, Feygelman, Vladimir, Stevens, Craig, and Forster, Kenneth
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- 2010
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34. Robustness Assessment of Images From a 0.35T Scanner of an Integrated MRI-Linac: Characterization of Radiomics Features in Phantom and Patient Data.
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Ericsson-Szecsenyi, Rebecka, Zhang, Geoffrey, Redler, Gage, Feygelman, Vladimir, Rosenberg, Stephen, Latifi, Kujtim, Ceberg, Crister, and Moros, Eduardo G.
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LINEAR accelerators ,RADIOMICS ,STEREOTACTIC radiotherapy ,SCANNING systems ,FEATURE extraction ,FOUR-dimensional imaging - Abstract
Purpose: Radiomics entails the extraction of quantitative imaging biomarkers (or radiomics features) hypothesized to provide additional pathophysiological and/or clinical information compared to qualitative visual observation and interpretation. This retrospective study explores the variability of radiomics features extracted from images acquired with the 0.35 T scanner of an integrated MRI-Linac. We hypothesized we would be able to identify features with high repeatability and reproducibility over various imaging conditions using phantom and patient imaging studies. We also compared findings from the literature relevant to our results. Methods: Eleven scans of a Magphan
® RT phantom over 13 months and 11 scans of a ViewRay Daily QA phantom over 11 days constituted the phantom data. Patient datasets included 50 images from ten anonymized stereotactic body radiation therapy (SBRT) pancreatic cancer patients (50 Gy in 5 fractions). A True Fast Imaging with Steady-State Free Precession (TRUFI) pulse sequence was selected, using a voxel resolution of 1.5 mm × 1.5 mm × 1.5 mm and 1.5 mm × 1.5 mm × 3.0 mm for phantom and patient data, respectively. A total of 1087 shape-based, first, second, and higher order features were extracted followed by robustness analysis. Robustness was assessed with the Coefficient of Variation (CoV < 5%). Results: We identified 130 robust features across the datasets. Robust features were found within each category, except for 2 second-order sub-groups, namely, Gray Level Size Zone Matrix (GLSZM) and Neighborhood Gray Tone Difference Matrix (NGTDM). Additionally, several robust features agreed with findings from other stability assessments or predictive performance studies in the literature. Conclusion: We verified the stability of the 0.35 T scanner of an integrated MRI-Linac for longitudinal radiomics phantom studies and identified robust features over various imaging conditions. We conclude that phantom measurements can be used to identify robust radiomics features. More stability assessment research is warranted. [ABSTRACT FROM AUTHOR]- Published
- 2022
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35. Maintaining dosimetric quality when switching to a Monte Carlo dose engine for head and neck volumetric‐modulated arc therapy planning.
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Feygelman, Vladimir, Latifi, Kujtim, Bowers, Mark, Greco, Kevin, Moros, Eduardo G., Isacson, Max, Angerud, Agnes, and Caudell, Jimmy
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VOLUMETRIC-modulated arc therapy ,RADIATION dosimetry ,HEAD & neck cancer ,TISSUES - Abstract
Head and neck cancers present challenges in radiation treatment planning due to the large number of critical structures near the target(s) and highly heterogeneous tissue composition. While Monte Carlo (MC) dose calculations currently offer the most accurate approximation of dose deposition in tissue, the switch to MC presents challenges in preserving the parameters of care. The differences in dose‐to‐tissue were widely discussed in the literature, but mostly in the context of recalculating the existing plans rather than reoptimizing with the MC dose engine. Also, the target dose homogeneity received less attention. We adhere to strict dose homogeneity objectives in clinical practice. In this study, we started with 21 clinical volumetric‐modulated arc therapy (VMAT) plans previously developed in Pinnacle treatment planning system. Those plans were recalculated "as is" with RayStation (RS) MC algorithm and then reoptimized in RS with both collapsed cone (CC) and MC algorithms. MC statistical uncertainty (0.3%) was selected carefully to balance the dose computation time (1–2 min) with the planning target volume (PTV) dose‐volume histogram (DVH) shape approaching that of a "noise‐free" calculation. When the hot spot in head and neck MC‐based treatment planning is defined as dose to 0.03 cc, it is exceedingly difficult to limit it to 105% of the prescription dose, as we were used to with the CC algorithm. The average hot spot after optimization and calculation with RS MC was statistically significantly higher compared to Pinnacle and RS CC algorithms by 1.2 and 1.0 %, respectively. The 95% confidence interval (CI) observed in this study suggests that in most cases a hot spot of ≤107% is achievable. Compared to the 95% CI for the previous clinical plans recalculated with RS MC "as is" (upper limit 108%), in real terms this result is at least as good or better than the historic plans. [ABSTRACT FROM AUTHOR]
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- 2022
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36. Triggered kV Imaging During Spine SBRT for Intrafraction Motion Management.
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Koo, Jihye, Nardella, Louis, Degnan, Michael, Andreozzi, Jacqueline, Yu, Hsiang-hsuan M., Penagaricano, Jose, Johnstone, Peter A. S., Oliver, Daniel, Ahmed, Kamran, Rosenberg, Stephen A., Wuthrick, Evan, Diaz, Roberto, Feygelman, Vladimir, Latifi, Kujtim, Moros, Eduardo G., and Redler, Gage
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SPINE ,THORACIC vertebrae ,PHYSICIANS ,STEREOTACTIC radiotherapy ,LUMBAR vertebrae - Abstract
Purpose: To monitor intrafraction motion during spine stereotactic body radiotherapy(SBRT) treatment delivery with readily available technology, we implemented triggered kV imaging using the on-board imager(OBI) of a modern medical linear accelerator with an advanced imaging package. Methods: Triggered kV imaging for intrafraction motion management was tested with an anthropomorphic phantom and simulated spine SBRT treatments to the thoracic and lumbar spine. The vertebral bodies and spinous processes were contoured as the image guided radiotherapy(IGRT) structures specific to this technique. Upon each triggered kV image acquisition, 2D projections of the IGRT structures were automatically calculated and updated at arbitrary angles for display on the kV images. Various shifts/rotations were introduced in x, y, z, pitch, and yaw. Gantry-angle-based triggering was set to acquire kV images every 45°. A group of physicists/physicians(n = 10) participated in a survey to evaluate clinical efficiency and accuracy of clinical decisions on images containing various phantom shifts. This method was implemented clinically for treatment of 42 patients(94 fractions) with 15 second time-based triggering. Result: Phantom images revealed that IGRT structure accuracy and therefore utility of projected contours during triggered imaging improved with smaller CT slice thickness. Contouring vertebra superior and inferior to the treatment site was necessary to detect clinically relevant phantom rotation. From the survey, detectability was proportional to the shift size in all shift directions and inversely related to the CT slice thickness. Clinical implementation helped evaluate robustness of patient immobilization. Based on visual inspection of projected IGRT contours on planar kV images, appreciable intrafraction motion was detected in eleven fractions(11.7%). Discussion: Feasibility of triggered imaging for spine SBRT intrafraction motion management has been demonstrated in phantom experiments and implementation for patient treatments. This technique allows efficient, non-invasive monitoring of patient position using the OBI and patient anatomy as a direct visual guide. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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37. Superficial and peripheral dose in compensator‐based FFF beam IMRT
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Zhang, Daniel G., Feygelman, Vladimir, Moros, Eduardo G., Latifi, Kujtim, Hoffe, Sarah, Frakes, Jessica, and Zhang, Geoffrey G.
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Phantoms, Imaging ,87.55.Gh ,Radiotherapy Planning, Computer-Assisted ,87.55.km ,Radiotherapy Dosage ,Equipment Design ,superficial dose ,Neoplasms ,Radiation Oncology Physics ,Humans ,Scattering, Radiation ,Radiotherapy, Intensity-Modulated ,Particle Accelerators ,compensator‐based IMRT ,87.53.Bn ,Monte Carlo ,Monte Carlo Method ,flattening filter‐free ,Filtration - Abstract
Flattening filter‐free (FFF) beams produce higher dose rates. Combined with compensator‐based intensity modulated radiotherapy (IMRT) techniques, the dose delivery for each beam can be much shorter compared to the flattened beam MLC‐based or flattened beam compensator‐based IMRT. This ‘snap shot’ IMRT delivery is beneficial to patients for tumor motion management. Due to softer energy, superficial doses in FFF beam treatment are usually higher than those from flattened beams. Due to no flattening filter, thus less photon scattering, peripheral doses are usually lower in FFF beam treatment. However, in compensator‐based IMRT using FFF beams, the compensator is in the beam pathway. Does it introduce beam hardening effects and scattering such that the superficial dose is lower and peripheral dose is higher compared to FFF beam MLC‐based IMRT? This study applied Monte Carlo techniques to investigate the superficial and peripheral doses in compensator‐based IMRT using FFF beams and compared it to the MLC‐based IMRT using FFF beams and flattened beams. Besides varying thicknesses of brass slabs to simulate varying thicknesses of compensators, a simple cone‐shaped compensator was simulated to mimic a clinical application. The dose distribution in water phantom by the cone‐shaped compensator was then simulated by multiple MLC‐defined FFF and flattened beams with varying apertures. After normalization to the maximum dose, Dmax, the superficial and peripheral doses were compared between the FFF beam compensator‐based IMRT and FFF/flattened beam MLC‐based IMRT. The superficial dose at the central 0.5 mm depth was about 1% (of Dmax) lower in the compensator‐based 6 MV FFF (6FFF) IMRT compared to the MLC‐based 6FFF IMRT, and about 8% higher than the flattened 6 MV MLC‐based IMRT dose. At 8 cm off‐axis at depth of central maximum dose, dmax, the peripheral dose between the 6FFF and flattened 6 MV MLC demonstrated similar doses, while the compensator dose was about 1% (of Dmax) higher. Compensators reduce the superficial doses slightly compared to open FFF beams, but increases the peripheral doses due to scatter in the compensator.
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- 2016
38. Dosimetric leaf gap and leaf trailing effect in a double‐stacked multileaf collimator.
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Hernandez, Victor, Saez, Jordi, Angerud, Agnes, Cayez, Romain, Khamphan, Catherine, Nguyen, Daniel, Vieillevigne, Laure, and Feygelman, Vladimir
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COLLIMATORS ,LEAF anatomy ,DYNAMIC testing - Abstract
Purpose: To investigate (i) the dosimetric leaf gap (DLG) and the effect of the "trailing distance" between leaves from different multileaf collimator (MLC) layers in Halcyon systems and (ii) the ability of the currently available treatment planning systems (TPSs) to approximate this effect. Methods: DICOM plans with transmission beams and sweeping gap tests were created in Python for measuring the DLG for each MLC layer independently and for both layers combined. In clinical Halcyon plans both MLC layers are interchangeably used and leaves from different layers are offset, thus forming a trailing pattern. To characterize the impact of such configuration, new tests called "trailing sweeping gaps" were designed and created where the leaves from one layer follow the leaves from the other layer at a fixed "trailing distance" t between the tips. Measurements were carried out on five Halcyons SX2 from different institutions and calculations from both the Eclipse and RayStation TPSs were compared with measurements. Results: The dose accumulated during a sweeping gap delivery progressively increased with the trailing distance t. We call this "the trailing effect." It is most pronounced for t between 0 and 5 mm, although some changes were obtained up to 20 mm. The dose variation was independent of the gap size. The measured DLG values also increased with t up to 20 mm, again with the steepest variation between 0 and 5 mm. Measured DLG values were negative at t = 0 (the leaves from both layers at the same position) but changed sign for t ≥ 1 mm, in line with the positive DLG sign usually observed with single‐layer rounded‐end MLCs. The Eclipse TPS does not explicitly model the leaf tip and, as a consequence, could not predict the dose reduction due to the trailing effect. This resulted in dose discrepancies up to +10% and −8% for the 5 mm sweeping gap and up to ±5% for the 10 mm one depending on the distance t. RayStation implements a simple model of the leaf tip that was able to approximate the trailing effect and improved the agreement with measured doses. In particular, with a prototype version of RayStation that assigned a higher transmission at the leaf tip the agreement with measured doses was within ±3% even for the 5 mm gap. The five Halcyon systems behaved very similarly but differences in the DLG around 0.2 mm were found across different treatment units and between MLC layers from the same system. The DLG for the proximal layer was consistently higher than for the distal layer, with differences ranging between 0.10 mm and 0.24 mm. Conclusions: The trailing distance between the leaves from different layers substantially affected the doses delivered by sweeping gaps and the measured DLG values. Stacked MLCs introduce a new level of complexity in TPSs, which ideally need to implement an explicit model of the leaf tip in order to reproduce the trailing effect. Dynamic tests called "trailing sweeping gaps" were designed that are useful for characterizing and commissioning dual‐layer MLC systems. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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39. On the MLC leaves alignment in the direction orthogonal to movement.
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Latifi, Kujtim, Lotey, Rajiv, and Feygelman, Vladimir
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IONIZATION chambers ,FAILURE mode & effects analysis ,FAILURE analysis ,COLLIMATORS - Abstract
The main focus of the recommended spatial accuracy tests for the multi‐leaf collimators (MLC) is calibration of the leaf position along the movement direction and overall alignment to the radiation isocenter. No explicit attention was typically paid to the alignment of the leaves from the opposing banks in the direction orthogonal to movement. This paper is a case study demonstrating that verification of such alignment at the time of acceptance testing is prudent. The original standard MLC (SMLC) on an MRIdian MRI‐guided linac (ViewRay Inc., Mountain View, CA, USA) was upgraded to a high‐speed MLC (HSMLC), which is supposed to be mechanically identical to the SMLC except for the higher drive screw pitch. The results of the end‐to‐end IMRT tests demonstrated unacceptable dosimetric results exemplified by an average and maximum ion chamber (IC) point dose error in the high‐dose low‐gradient region of 2.5 ± 1.4% and 4.6%, respectively. Before the upgrade, those values were 0.3 ± 0.7% and 0.9%, respectively. An exhaustive analysis of possible failure modes eventually zeroed in on the average misalignment of about 1 mm in the Y (along the couch) direction between the right and left upper MLC banks. The MLC was replaced, reducing the Y‐direction misalignment to 0.4 mm. As a result, the average and maximum IC dose‐errors became acceptable 1.0 ± 0.7% and 1.6%, respectively. Simple film and/or chamber array tests during acceptance testing can easily detect Y‐direction misalignments between opposing leaves banks measuring a fraction of a mm at isocenter. Left undetected, such misalignment can cause nontrivial dosimetric consequences. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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40. Volumetric modulated arc planning for lung stereotactic body radiotherapy using conventional and unflattened photon beams: a dosimetric comparison with 3D technique
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Zhang Geoffrey G, Ku Lichung, Dilling Thomas J, Stevens Craig W, Zhang Ray R, Li Weiqi, and Feygelman Vladimir
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Medical physics. Medical radiology. Nuclear medicine ,R895-920 ,Neoplasms. Tumors. Oncology. Including cancer and carcinogens ,RC254-282 - Abstract
Abstract Purpose Frequently, three-dimensional (3D) conformal beams are used in lung cancer stereotactic body radiotherapy (SBRT). Recently, volumetric modulated arc therapy (VMAT) was introduced as a new treatment modality. VMAT techniques shorten delivery time, reducing the possibility of intrafraction target motion. However dose distributions can be quite different from standard 3D therapy. This study quantifies those differences, with focus on VMAT plans using unflattened photon beams. Methods A total of 15 lung cancer patients previously treated with 3D or VMAT SBRT were randomly selected. For each patient, non-coplanar 3D, coplanar and non-coplanar VMAT and flattening filter free VMAT (FFF-VMAT) plans were generated to meet the same objectives with 50 Gy covering 95% of the PTV. Two dynamic arcs were used in each VMAT plan. The couch was set at ± 5° to the 0° straight position for the two non-coplanar arcs. Pinnacle version 9.0 (Philips Radiation Oncology, Fitchburg WI) treatment planning system with VMAT capabilities was used. We analyzed the conformity index (CI), which is the ratio of the total volume receiving at least the prescription dose to the target volume receiving at least the prescription dose; the conformity number (CN) which is the ratio of the target coverage to CI; and the gradient index (GI) which is the ratio of the volume of 50% of the prescription isodose to the volume of the prescription isodose; as well as the V20, V5, and mean lung dose (MLD). Paired non-parametric analysis of variance tests with post-tests were performed to examine the statistical significance of the differences of the dosimetric indices. Results Dosimetric indices CI, CN and MLD all show statistically significant improvement for all studied VMAT techniques compared with 3D plans (p < 0.05). V5 and V20 show statistically significant improvement for the FFF-VMAT plans compared with 3D (p < 0.001). GI is improved for the FFF-VMAT and the non-coplanar VMAT plans (p < 0.01 and p < 0.05 respectively) while the coplanar VMAT plans do not show significant difference compared to 3D plans. Dose to the target is typically more homogeneous in FFF-VMAT plans. FFF-VMAT plans require more monitor units than 3D or non-coplanar VMAT ones. Conclusion Besides the advantage of faster delivery times, VMAT plans demonstrated better conformity to target, sharper dose fall-off in normal tissues and lower dose to normal lung than the 3D plans for lung SBRT. More monitor units are often required for FFF-VMAT plans.
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- 2011
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41. Unlocking a closed system: dosimetric commissioning of a ring gantry linear accelerator in a multivendor environment.
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Saini, Amarjit, Tichacek, Chris, Johansson, William, Redler, Gage, Zhang, Geoffrey, Moros, Eduardo G., Qayyum, Muqeem, and Feygelman, Vladimir
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LINEAR accelerators ,IONIZATION chambers ,CONFIDENCE intervals ,GAMMA distributions ,HEPATIC portal system ,DYNAMIC testing - Abstract
The Halcyon™ platform is self‐contained, combining a treatment planning (Eclipse) system TPS) with information management and radiation delivery components. The standard TPS beam model is configured and locked down by the vendor. A portal dosimetry‐based system for patient‐specific QA (PSQA) is also included. While ensuring consistency across the user base, this closed model may not be optimal for every department. We set out to commission independent TPS (RayStation 9B, RaySearch Laboratories) and PSQA (PerFraction, Sun Nuclear Corp.) systems for use with the Halcyon linac. The output factors and PDDs for very small fields (0.5 × 0.5 cm2) were collected to augment the standard Varian dataset. The MLC leaf‐end parameters were estimated based on the various static and dynamic tests with simple model fields and honed by minimizing the mean and standard deviation of dose difference between the ion chamber measurements and RayStation Monte Carlo calculations for 15 VMAT and IMRT test plans. Two chamber measurements were taken per plan, in the high (isocenter) and lower dose regions. The ratio of low to high doses ranged from 0.4 to 0.8. All percent dose differences were expressed relative to the local dose. The mean error was 0.0 ± 1.1% (TG119‐style confidence limit ± 2%). Gamma analysis with the helical diode array using the standard 3%Global/2mm criteria resulted in the average passing rate of 99.3 ± 0.5% (confidence limit 98.3%–100%). The average local dose error for all detectors across all plans was 0.2% ± 5.3%. The ion chamber results compared favorably with our recalculation with Eclipse and PerFraction, as well as with several published Eclipse reports. Dose distribution gamma analysis comparisons between RayStation and PerFraction with 2%Local/2mm criteria yielded an average passing rate of 98.5% ± 0.8% (confidence limit 96.9%–100%). It is feasible to use the Halcyon accelerator with independent planning and verification systems without sacrificing dosimetric accuracy. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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42. Pretreatment CT and PET radiomics predicting rectal cancer patients in response to neoadjuvant chemoradiotherapy.
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Zhigang Yuan, Frazer, Marissa, Rishi, Anupam, Latifi, Kujtim, Tomaszewski, Michal R., Moros, Eduardo G., Feygelman, Vladimir, Felder, Seth, Sanchez, Julian, Dessureault, Sophie, Imanirad, Iman, Kim, Richard D., Harrison, Louis B., Hoffe, Sarah E., Zhang, Geoffrey G., and Frakes, Jessica M.
- Abstract
Background: The purpose of this study was to characterize pre-treatment non-contrast computed tomography (CT) and 18F-fluorodeoxyglucose positron emission tomography (PET) based radiomics signatures predictive of pathological response and clinical outcomes in rectal cancer patients treated with neoadjuvant chemoradiotherapy (NACR T). Materials and methods: An exploratory analysis was performed using pre-treatment non-contrast CT and PET imaging dataset. The association of tumor regression grade (TRG) and neoadjuvant rectal (NAR) score with pre-treatment CT and PET features was assessed using machine learning algorithms. Three separate predictive models were built for composite features from CT + PET. Results: The patterns of pathological response were TRG 0 (n = 13; 19.7%), 1 (n = 34; 51.5%), 2 (n = 16; 24.2%), and 3 (n = 3; 4.5%). There were 20 (30.3%) patients with low, 22 (33.3%) with intermediate and 24 (36.4%) with high NAR scores. Three separate predictive models were built for composite features from CT + PET and analyzed separately for clinical endpoints. Composite features with α = 0.2 resulted in the best predictive power using logistic regression. For pathological response prediction, the signature resulted in 88.1% accuracy in predicting TRG 0 vs. TRG 1-3; 91% accuracy in predicting TRG 0-1 vs. TRG 2-3. For the surrogate of DFS and OS, it resulted in 67.7% accuracy in predicting low vs. intermediate vs. high NAR scores. Conclusion: The pre-treatment composite radiomics signatures were highly predictive of pathological response in rectal cancer treated with NACR T. A larger cohort is warranted for further validation. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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43. Light-induced adiabatic structural relaxation and electronic energy deactivation in Pyridinium bications
- Author
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Knyazhansky, Michael I., Metelitsa, Anatoly V., Makarova, Nadezhda I., Feygelman, Vladimir M., and Tymyansky, Jacob R.
- Published
- 2000
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44. Semiconductor dosimetry in modern external-beam radiation therapy.
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Rosenfeld, Anatoly B, Biasi, Giordano, Petasecca, Marco, Lerch, Michael L F, Villani, Giulio, and Feygelman, Vladimir
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RADIOTHERAPY ,METAL oxide semiconductor field-effect transistors ,RADIATION dosimetry ,SEMICONDUCTOR diodes ,SEMICONDUCTORS ,FIELD-effect transistors - Abstract
Semiconductor dosimeters are ubiquitous in modern external-beam radiation therapy. They possess key features. The response, electronically available in real time, is stable and linear with absorbed dose for given irradiation conditions; the radiation-sensitive volume can be rather small in size, while retaining mechanical strength and high sensitivity. We describe three common semiconductor dosimeters: diodes, metal-oxide-semiconductor field-effect transistors and diamonds. We discuss in detail their operation principles and applications in modern external-beam radiation therapy, primarily with megavoltage photon beams. We also explore their use in proton and heavy ion therapy, and in experimental radiotherapy techniques such as synchrotron-based micro-beam radiation therapy. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
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45. CT-based radiomic features to predict pathological response in rectal cancer: A retrospective cohort study.
- Author
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Yuan, Zhigang, Frazer, Marissa, Zhang, Geoffrey G, Latifi, Kujtim, Moros, Eduardo G, Feygelman, Vladimir, Felder, Seth, Sanchez, Julian, Dessureault, Sophie, Imanirad, Iman, Kim, Richard D, Harrison, Louis B, Hoffe, Sarah E, and Frakes, Jessica M
- Subjects
RECTAL cancer ,COHORT analysis ,RETROSPECTIVE studies ,ENDORECTAL ultrasonography ,CANCER patients ,PREDICTION models ,PREDICTIVE tests ,RECTUM tumors ,TUMOR classification ,COMPUTED tomography ,COMBINED modality therapy ,TUMOR grading - Abstract
Introduction: Innovative biomarkers to predict treatment response in rectal cancer would be helpful in optimizing personalized treatment approaches. In this study, we aimed to develop and validate a CT-based radiomic imaging biomarker to predict pathological response.Methods: We used two independent cohorts of rectal cancer patients to develop and validate a CT-based radiomic imaging biomarker predictive of treatment response. A total of 91 rectal cancer cases treated from 2009 to 2018 were assessed for the tumour regression grade (TRG) (0 = pathological complete response, pCR; 1 = moderate response; 2 = partial response; 3 = poor response). Exploratory analysis was performed by combining pre-treatment non-contrast CT images and patterns of TRG. The models built from the training cohort were further assessed using the independent validation cohort.Results: The patterns of pathological response in training and validation groups were TRG 0 (n = 14, 23.3%; n = 6, 19.4%), 1 (n = 31, 51.7%; n = 15, 48.4%), 2 (n = 12, 20.0%; n = 7, 22.6%) and 3 (n = 3, 5.0%; n = 3, 9.7%), respectively. Separate predictive models were built and analysed from CT features for pathological response. For pathological response prediction, the model including 8 radiomic features by random forest method resulted in 83.9% accuracy in predicting TRG 0 vs TRG 1-3 in validation.Conclusion: The pre-treatment CT-based radiomic signatures were developed and validated in two independent cohorts. This imaging biomarker provided a promising way to predict pCR and select patients for non-operative management. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
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46. AAPM Task Group 329: Reference dose specification for dose calculations: Dose‐to‐water or dose‐to‐muscle?
- Author
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Kry, Stephen F., Feygelman, Vladimir, Balter, Peter, Knöös, Tommy, Charlie Ma, C.‐M., Snyder, Michael, Tonner, Brian, and Vassiliev, Oleg N.
- Subjects
- *
CORRECTION factors , *TECHNICAL specifications , *CALIBRATION - Abstract
Linac calibration is done in water, but patients are comprised primarily of soft tissue. Conceptually, and specified in NRG/RTOG trials, dose should be reported as dose‐to‐muscle to describe the dose to the patient. Historically, the dose‐to‐water of the linac calibration was often converted to dose‐to‐muscle for patient calculations through manual application of a 0.99 dose‐to‐water to dose‐to‐muscle correction factor, applied during the linac clinical reference calibration. However, many current treatment planning system (TPS) dose calculation algorithms approximately provide dose‐to‐muscle (tissue), making application of a manual scaling unnecessary. There is little guidance on when application of a scaling factor is appropriate, resulting in highly inconsistent application of this scaling by the community. In this report we provide guidance on the steps necessary to go from the linac absorbed dose‐to‐water calibration to dose‐to‐muscle in patient, for various commercial TPS algorithms. If the TPS does not account for the difference between dose‐to‐water and dose‐to‐muscle, then TPS reference dose scaling is warranted. We have tabulated the major vendors' TPS in terms of whether they approximate dose‐to‐muscle or calculate dose‐to‐water and recommend the correction factor required to report dose‐to‐muscle directly from the TPS algorithm. Physicists should use this report to determine the applicable correction required for specifying the reference dose in their TPS to achieve this goal and should remain attentive to possible changes to their dose calculation algorithm in the future. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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47. Comprehensive evaluation of the high‐resolution diode array for SRS dosimetry.
- Author
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Ahmed, Saeed, Zhang, Geoffrey, Moros, Eduardo G., and Feygelman, Vladimir
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RADIATION dosimetry ,PRINTED circuits ,DIODES ,IONIZATION chambers ,MOTION picture distribution ,CORRECTION factors ,SCINTILLATORS - Abstract
A high‐resolution diode array has been comprehensively evaluated. It consists of 1013 point diode detectors arranged on the two 7.7 × 7.7 cm2 printed circuit boards (PCBs). The PCBs are aligned face to face in such a way that the active volumes of all diodes are in the same plane. All individual correction factors required for accurate dosimetry have been validated for conventional and flattening filter free (FFF) 6MV beams. That included diode response equalization, linearity, repetition rate dependence, field size dependence, angular dependence at the central axis and off‐axis in the transverse, sagittal, and multiple arbitrary planes. In the end‐to‐end tests the array and radiochromic film dose distributions for SRS‐type multiple‐target plans were compared. In the equalization test (180° rotation), the average percent dose error between the normal and rotated positions for all diodes was 0.01% ± 0.1% (range −0.3 to 0.4%) and −0.01% ± 0.2% (range −0.9 to 0.9%) for 6 MV and 6MV FFF beams, respectively. For the axial angular response, corrected dose stayed within 2% from the ion chamber for all gantry angles, until the beam direction approached the detector plane. In azimuthal direction, the device agreed with the scintillator within 1% for both energies. For multiple combinations of couch and gantry angles, the average percent errors were −0.00% ± 0.6% (range: −2.1% to 1.6%) and −0.1% ± 0.5% (range −1.6% to 2.1%) for the 6MV and 6MV FFF beams, respectively. The measured output factors were largely within 2% of the scintillator, except for the 5 mm 6MV beam showing a 3.2% deviation. The 2%/1 mm gamma analysis of composite SRS measurements produced the 97.2 ± 1.3% (range 95.8‐98.5%) average passing rate against film. Submillimeter (≤0.5 mm) dose profile alignment with film was demonstrated in all cases. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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48. Evaluating IMRT and VMAT dose accuracy: Practical examples of failure to detect systematic errors when applying a commonly used metric and action levels
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Nelms, Benjamin E., Chan, Maria F., Jarry, Geneviève, Lemire, Matthieu, Lowden, John, Hampton, Carnell, and Feygelman, Vladimir
- Subjects
Radiation Therapy Physics ,Quality Control ,Phantoms, Imaging ,Radiotherapy Planning, Computer-Assisted ,Uncertainty ,Reproducibility of Results ,Radiotherapy Dosage ,Imaging, Three-Dimensional ,Gamma Rays ,Image Processing, Computer-Assisted ,Humans ,Radiotherapy, Intensity-Modulated ,Radiometry ,Algorithms - Abstract
PURPOSE: This study (1) examines a variety of real-world cases where systematic errors were not detected by widely accepted methods for IMRT/VMAT dosimetric accuracy evaluation, and (2) drills-down to identify failure modes and their corresponding means for detection, diagnosis, and mitigation. The primary goal of detailing these case studies is to explore different, more sensitive methods and metrics that could be used more effectively for evaluating accuracy of dose algorithms, delivery systems, and QA devices. METHODS: The authors present seven real-world case studies representing a variety of combinations of the treatment planning system (TPS), linac, delivery modality, and systematic error type. These case studies are typical to what might be used as part of an IMRT or VMAT commissioning test suite, varying in complexity. Each case study is analyzed according to TG-119 instructions for gamma passing rates and action levels for per-beam and/or composite plan dosimetric QA. Then, each case study is analyzed in-depth with advanced diagnostic methods (dose profile examination, EPID-based measurements, dose difference pattern analysis, 3D measurement-guided dose reconstruction, and dose grid inspection) and more sensitive metrics (2% local normalization/2 mm DTA and estimated DVH comparisons). RESULTS: For these case studies, the conventional 3%/3 mm gamma passing rates exceeded 99% for IMRT per-beam analyses and ranged from 93.9% to 100% for composite plan dose analysis, well above the TG-119 action levels of 90% and 88%, respectively. However, all cases had systematic errors that were detected only by using advanced diagnostic techniques and more sensitive metrics. The systematic errors caused variable but noteworthy impact, including estimated target dose coverage loss of up to 5.5% and local dose deviations up to 31.5%. Types of errors included TPS model settings, algorithm limitations, and modeling and alignment of QA phantoms in the TPS. Most of the errors were correctable after detection and diagnosis, and the uncorrectable errors provided useful information about system limitations, which is another key element of system commissioning. CONCLUSIONS: : Many forms of relevant systematic errors can go undetected when the currently prevalent metrics for IMRT/VMAT commissioning are used. If alternative methods and metrics are used instead of (or in addition to) the conventional metrics, these errors are more likely to be detected, and only once they are detected can they be properly diagnosed and rooted out of the system. Removing systematic errors should be a goal not only of commissioning by the end users but also product validation by the manufacturers. For any systematic errors that cannot be removed, detecting and quantifying them is important as it will help the physicist understand the limits of the system and work with the manufacturer on improvements. In summary, IMRT and VMAT commissioning, along with product validation, would benefit from the retirement of the 3%/3 mm passing rates as a primary metric of performance, and the adoption instead of tighter tolerances, more diligent diagnostics, and more thorough analysis.
- Published
- 2013
49. A hybrid volumetric dose verification method for single‐isocenter multiple‐target cranial SRS.
- Author
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Ahmed, Saeed, Kapatoes, Jeff, Zhang, Geoffrey, Moros, Eduardo G., and Feygelman, Vladimir
- Subjects
CHROMIUM isotopes ,RADIOCHROMATOGRAPHY ,IONIZATION chambers ,GAMMA distributions ,RADIOSURGERY - Abstract
Abstract: A commercial semi‐empirical volumetric dose verification system (PerFraction [PF], Sun Nuclear Corp.) extracts multi‐leaf collimator positions from the electronic portal imaging device movies collected during a pre‐treatment run, while the rest of the delivered control point information is harvested from the accelerator log files. This combination is used to reconstruct dose on a patient CT dataset with a fast superposition/convolution algorithm. The method was validated for single‐isocenter multi‐target SRS VMAT treatments against absolute radiochromic film measurements in a cylindrical phantom. The targets ranged in size from 0.8 to 3.6 cm and in number from 3 to 10 per plan. A total of 17 films rotated at different angles around the cylinder axis were analyzed. Each of 27 total targets was intercepted by at least one film, and 2–4 different films were analyzed per plan. Film dose was always scaled to the ion chamber measurement in a high‐dose, low‐gradient area deliberately created at the isocenter. The planar dose agreement between PF and film using 3%(Global dose‐difference normalization)/1 mm gamma analysis was on average 99.2 ± 1.1%. The point dose difference in the low‐gradient area in the middle of every target was below 3%, while PF‐reconstructed and film dose centroids for individual targets showed submillimeter agreement when measured on a well aligned accelerator. Volumetrically, all voxels in all plans agreed between PF and the primary treatment planning system at the 3%/1 mm level. With proper understanding of its advantages and shortcomings, the tool can be applied to patient‐specific QA in routine radiosurgical clinical practice. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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50. Practical quantification of image registration accuracy following the AAPM TG‐132 report framework.
- Author
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Latifi, Kujtim, Caudell, Jimmy, Zhang, Geoffrey, Hunt, Dylan, Moros, Eduardo G., and Feygelman, Vladimir
- Subjects
IMAGE quality in medical radiography ,TOMOGRAPHY image quality ,IMAGE quality in radiography ,IMAGE quality in diagnostic ultrasonic imaging ,MEDICAL electronics - Abstract
Abstract: The AAPM TG 132 Report enumerates important steps for validation of the medical image registration process. While the Report outlines the general goals and criteria for the tests, specific implementation may be obscure to the wider clinical audience. We endeavored to provide a detailed step‐by‐step description of the quantitative tests’ execution, applied as an example to a commercial software package (Mirada Medical, Oxford, UK), while striving for simplicity and utilization of readily available software. We demonstrated how the rigid registration data could be easily extracted from the DICOM registration object and used, following some simple matrix math, to quantify accuracy of rigid translations and rotations. The options for validating deformable image registration (DIR) were enumerated, and it was shown that the most practically viable ones are comparison of propagated internal landmark points on the published datasets, or of segmented contours that can be generated locally. The multimodal rigid registration in our example did not always result in the desired registration error below ½ voxel size, but was considered acceptable with the maximum errors under 1.3 mm and 1°. The DIR target registration errors in the thorax based on internal landmarks were far in excess of the Report recommendations of 2 mm average and 5 mm maximum. On the other hand, evaluation of the DIR major organs’ contours propagation demonstrated good agreement for lung and abdomen (Dice Similarity Coefficients, DSC, averaged over all cases and structures of 0.92 ± 0.05 and 0.91 ± 0.06, respectively), and fair agreement for Head and Neck (average DSC = 0.73 ± 0.14). The average for head and neck is reduced by small volume structures such as pharyngeal constrictor muscles. Even these relatively simple tests show that commercial registration algorithms cannot be automatically assumed sufficiently accurate for all applications. Formalized task‐specific accuracy quantification should be expected from the vendors. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
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