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Yamada T, Nakano H, Tanabe S, Sakai T, Tanabe S, Oka T, Sakai H, Oshikane T, Nakano T, Ohta A, Kanazawa T, Kaidu M, Ishikawa H. Verification of Qfix Encompass™ couch modeling using the Acuros XB algorithm and HypeArc™ using a high-spatial-resolution two-dimensional diode array. Med Dosim 2023; 48:261-266. [PMID: 37455221 DOI: 10.1016/j.meddos.2023.06.002] [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: 03/18/2023] [Revised: 05/15/2023] [Accepted: 06/20/2023] [Indexed: 07/18/2023]
Abstract
We modeled the Qfix Encompass™ immobilization system and further verified the calculated dose distribution of the AcurosXB (AXB) dose calculation algorithm using SRS MapCHECKⓇ (SRSMC) in the HyperArc™ (HA) clinical plan. An Encompass system with a StereoPHAN™ QA phantom was scanned by SOMATOM go.Sim and imported to an Eclipse™ treatment planning system to create a treatment plan for Encompass modeling. The Encompass modeling was performed in the StereoPHAN with a pinpoint ion chamber for 6 MV and 6 MV flattening filter free (6 MV FFF), and 2 × 2 cm2, 4 × 4 cm2, and 6 × 6 cm2 irradiation field sizes. The dose calculation algorithm used was AXB ver. 15.5 with a 1.0 mm calculation grid size. The Hounsfield unit (HU) values of the Encompass modeling were set to 400, -100, -200, and -300 for Encompass, and -400, -600, -700, and -800 for the Encompass base. We evaluated the dose distribution after Encompass modeling by SRSMC using gamma analysis in 12 patients. We adopted HU values of -200 for Encompass, -800 for Encompass base for 6 MV, and -200 for Encompass and -700 for Encompass. Base for 6 MV FFF was adopted as the HU values for the Encompass modeling based on the measurement results. The proposed Encompass modeling resulted in a mean pass rate evaluation >98% for both 6 MV and 6 MV FFF when the 1%/1 mm criterion was used, demonstrating that the proposed HU value can be adopted to calculate more accurate dose distributions.
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Affiliation(s)
- Takumi Yamada
- Section of Radiology, Department of Clinical Support, Niigata University Medical and Dental Hospital, Niigata, 951-8520, Japan
| | - Hisashi Nakano
- Department of Radiation Oncology, Niigata University Medical and Dental Hospital, Niigata 951-8520, Japan; Department of Medical Physics and Engineering, Osaka University Graduate School of Medicine, Osaka, 565-0871, Japan.
| | - Satoshi Tanabe
- Department of Radiation Oncology, Niigata University Medical and Dental Hospital, Niigata 951-8520, Japan
| | - Tatsuya Sakai
- Section of Radiology, Department of Clinical Support, Niigata University Medical and Dental Hospital, Niigata, 951-8520, Japan
| | - Shunpei Tanabe
- Department of Radiation Oncology, Niigata University Medical and Dental Hospital, Niigata 951-8520, Japan
| | - Tetsuya Oka
- Section of Radiology, Department of Clinical Support, Niigata University Medical and Dental Hospital, Niigata, 951-8520, Japan
| | - Hironori Sakai
- Section of Radiology, Department of Clinical Support, Niigata University Medical and Dental Hospital, Niigata, 951-8520, Japan
| | - Tomoya Oshikane
- Department of Radiation Oncology, Niigata University Medical and Dental Hospital, Niigata 951-8520, Japan
| | - Toshimichi Nakano
- Department of Radiology and Radiation Oncology, Niigata University Graduate School of Medical and Dental Sciences, Niigata, 951-8122, Japan
| | - Atsushi Ohta
- Department of Radiation Oncology, Niigata University Medical and Dental Hospital, Niigata 951-8520, Japan
| | - Tsutomu Kanazawa
- Section of Radiology, Department of Clinical Support, Niigata University Medical and Dental Hospital, Niigata, 951-8520, Japan
| | - Motoki Kaidu
- Department of Radiology and Radiation Oncology, Niigata University Graduate School of Medical and Dental Sciences, Niigata, 951-8122, Japan
| | - Hiroyuki Ishikawa
- Department of Radiology and Radiation Oncology, Niigata University Graduate School of Medical and Dental Sciences, Niigata, 951-8122, Japan
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Bawazeer O, Herath S, Sarasanandarajah S, Kron T, Dunn L, Deb P. A simple and efficient method to measure beam attenuation through a radiotherapy treatment couch and immobilization devices. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2019; 42:1183-1189. [PMID: 31452056 DOI: 10.1007/s13246-019-00789-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Accepted: 08/09/2019] [Indexed: 11/29/2022]
Abstract
We propose a simple and efficient method to measure beam attenuation in one or two dimensions using an amorphous silicon electronic portal imaging device (a-Si EPID). The proposed method was validated against ionization chamber measurements. Beam attenuation through treatment couches (Varian Medical Systems) and immobilization devices (CIVCO Radiotherapy, USA) was examined. The dependency of beam attenuation on field size, photon energy, thickness of the couch, and the presence of a phantom were studied. Attenuation images were derived by computing the percentage difference between images obtained without and with a couch or immobilization devices determining the percentage of attenuation at the center and the mean attenuation. The beam attenuation measurements obtained with an a-Si EPID and an ionization chamber agreed to within ± 0.10 to 1.80%. No difference was noted between the center and mean of an attenuated image for a small field size of 5 × 5 cm2, whereas a large field size of 15 × 15 cm2 exhibited differences of up to 1.13%. For an 18 MV beam, the a-Si EPID required additional build-up material for accurate assessment of beam attenuation. The a-Si EPID could measure differences in beam attenuation through an image guided radiotherapy (IGRT) couch regardless of the variabilities in couch thickness. Interestingly, the addition of a phantom reduced the magnitude of attenuation by approximately 1.20% for a field size of 15 × 15 cm2. A simple method is proposed that provides the user with beam attenuation data in either 2D or 1D within a few minutes.
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Affiliation(s)
- Omemh Bawazeer
- Discipline of Medical Radiations, RMIT University, Melbourne, Australia. .,Discipline of Sciences, Umm Al-Qura University, Mecca, Saudi Arabia.
| | - Sisira Herath
- Department of Physical Sciences, Peter MacCallum Cancer Centre, Melbourne, Australia
| | - Sivananthan Sarasanandarajah
- Discipline of Medical Radiations, RMIT University, Melbourne, Australia.,Department of Physical Sciences, Peter MacCallum Cancer Centre, Melbourne, Australia.,Department of Medical Imaging and Radiation Sciences, Monash University, Melbourne, Australia
| | - Tomas Kron
- Department of Physical Sciences, Peter MacCallum Cancer Centre, Melbourne, Australia.,Sir Peter MacCallum Cancer Institute, University of Melbourne, Melbourne, Australia
| | - Leon Dunn
- Epworth Radiation Oncology, Epworth Hospital, Melbourne, Australia
| | - Pradip Deb
- Discipline of Medical Radiations, RMIT University, Melbourne, Australia
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Olch AJ, Gerig L, Li H, Mihaylov I, Morgan A. Dosimetric effects caused by couch tops and immobilization devices: Report of AAPM Task Group 176. Med Phys 2014; 41:061501. [DOI: 10.1118/1.4876299] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Foo J, Stensmyr R. Depth dose comparison of measured and calculated dose for the Eclipse virtual carbon couch top models with air gap variation. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2013; 36:457-63. [PMID: 24132584 DOI: 10.1007/s13246-013-0224-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Accepted: 10/08/2013] [Indexed: 11/26/2022]
Abstract
This study assessed the accuracy of Eclipse™ (Varian Medical Systems, Palo Alto, CA, USA) treatment planning system (TPS) dose calculations when using virtual couch top models to account for couch presence in patient treatments. The Flat panel and Unipanel couch tops for the Varian Exact Couch were used in this study. Assigned Hounsfield unit (HU) for the virtual couch tops were varied and TPS calculated dose was compared to measured data to determine an optimal assigned HU. Air gaps of up to 10 cm were introduced between couch and phantom to assess the ability of the models to replicate dose in this situation, commonly seen clinically. Dose was measured at a range of depths, for each air gap thickness, in order to assess the model both near surface and at various depths beyond the dose maximum. Optimal HU was taken to be that which had the best agreement between measured and calculated dose over the range of gaps and depths tested. For the Flat panel couch top this was found to be -500 HU and for the Unipanel couch top, -200 HU. Default HU parameters originally set in the models was found to be not optimal for the whole range of depths studied. With optimal HU parameters set, there was good agreement between calculated and measured dose for depths greater than 0.5 cm, but discrepancies were still observed near surface. When implementing virtual couch top models, users could improve dose calculation accuracy by determining the optimal HU from comparisons over several clinical depths rather than a single depth.
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Affiliation(s)
- Jacqueline Foo
- Nepean Cancer Care Centre, Nepean Hospital, Cnr Great Western Highway and Somerset St, Kingswood, NSW, 2747, Australia,
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