1
|
Dai T, Sloop AM, Schönfeld A, Flatten V, Kozelka J, Hildreth J, Bill S, Sunnerberg JP, Clark MA, Jarvis L, Pogue BW, Bruza P, Gladstone DJ, Zhang R. Electron beam response corrections for an ultra-high-dose-rate capable diode dosimeter. Med Phys 2024. [PMID: 38762909 DOI: 10.1002/mp.17121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Accepted: 04/29/2024] [Indexed: 05/21/2024] Open
Abstract
BACKGROUND Ultra-high-dose-rate (UHDR) electron beams have been commonly utilized in FLASH studies and the translation of FLASH Radiotherapy (RT) to the clinic. The EDGE diode detector has potential use for UHDR dosimetry albeit with a beam energy dependency observed. PURPOSE The purpose is to present the electron beam response for an EDGE detector in dependence on beam energy, to characterize the EDGE detector's response under UHDR conditions, and to validate correction factors derived from the first detailed Monte Carlo model of the EDGE diode against measurements, particularly under UHDR conditions. METHODS Percentage depth doses (PDDs) for the UHDR Mobetron were measured with both EDGE detectors and films. A detailed Monte Carlo (MC) model of the EDGE detector has been configured according to the blueprint provided by the manufacturer under an NDA agreement. Water/silicon dose ratios of EDGE detector for a series of mono-energetic electron beams have been calculated. The dependence of the water/silicon dose ratio on depth for a FLASH relevant electron beam was also studied. An analytical approach for the correction of PDD measured with EDGE detectors was established. RESULTS Water/silicon dose ratio decreased with decreasing electron beam energy. For the Mobetron 9 MeV UHDR electron beam, the ratio decreased from 1.09 to 1.03 in the build-up region, maintained in range of 0.98-1.02 at the fall-off region and raised to a plateau in value of 1.08 at the tail. By applying the corrections, good agreement between the PDDs measured by the EDGE detector and those measured with film was achieved. CONCLUSIONS Electron beam response of an UHDR capable EDGE detector was derived from first principles utilizing a sophisticated MC model. An analytical approach was validated for the PDDs of UHDR electron beams. The results demonstrated the capability of EDGE detector in measuring PDDs of UHDR electron beams.
Collapse
Affiliation(s)
- Tianyuan Dai
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
- Department of Radiation Oncology Physics and Technology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan Shandong, China
| | - Austin M Sloop
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | | | | | | | | | - Simon Bill
- Sun Nuclear Corp, Melbourne, Florida, USA
| | - Jacob P Sunnerberg
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | - Megan A Clark
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | - Lesley Jarvis
- Department of Medicine, Geisel School of Medicine, Dartmouth College Hanover, Lebanon, New Hampshire, USA
- Dartmouth Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire, USA
| | - Brian W Pogue
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
- Dartmouth Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire, USA
- Department of Medical Physics, Wisconsin Institutes for Medical Research, University of Wisconsin, Madison, Wisconsin, USA
| | - Petr Bruza
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | - David J Gladstone
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
- Department of Medicine, Geisel School of Medicine, Dartmouth College Hanover, Lebanon, New Hampshire, USA
- Dartmouth Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire, USA
| | - Rongxiao Zhang
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
- Department of Radiation Medicine, New York Medical College, Valhalla, New York, USA
| |
Collapse
|
2
|
Hirashima H, Nakamura M, Nakamura K, Matsuo Y, Mizowaki T. Dosimetric verification of four dose calculation algorithms for spine stereotactic body radiotherapy. JOURNAL OF RADIATION RESEARCH 2024; 65:109-118. [PMID: 37996097 PMCID: PMC10803157 DOI: 10.1093/jrr/rrad086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 09/18/2023] [Accepted: 10/16/2023] [Indexed: 11/25/2023]
Abstract
The applications of Type B [anisotropic analytical algorithm (AAA) and collapsed cone (CC)] and Type C [Acuros XB (AXB) and photon Monte Carlo (PMC)] dose calculation algorithms in spine stereotactic body radiotherapy (SBRT) were evaluated. Water- and bone-equivalent phantoms were combined to evaluate the percentage depth dose and dose profile. Subsequently, 48 consecutive patients with clinical spine SBRT plans were evaluated. All treatment plans were created using AXB in Eclipse. The prescription dose was 24 Gy in two fractions at a 10 MV FFF on TrueBeam. The doses were then recalculated with AAA, CC and PMC while maintaining the AXB-calculated monitor units and beam arrangement. The dose index values obtained using the four dose calculation algorithms were then compared. The AXB and PMC dose distributions agreed with the bone-equivalent phantom measurements (within ±2.0%); the AAA and CC values were higher than those in the bone-equivalent phantom region. For the spine SBRT plans, PMC, AAA and CC were overestimated compared with AXB in terms of the near minimum and maximum doses of the target and organ at risk, respectively; the mean dose difference was within 4.2%, which is equivalent with within 1 Gy. The phantom study showed that the results from AXB and PMC agreed with the measurements within ±2.0%. However, the mean dose difference ranged from 0.5 to 1 Gy in the spine SBRT planning study when the dose calculation algorithms changed. Users should incorporate a clinical introduction that includes an awareness of these differences.
Collapse
Affiliation(s)
- Hideaki Hirashima
- Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Mitsuhiro Nakamura
- Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
- Department of Advanced Medical Physics, Graduate School of Medicine, Kyoto University, 53 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Kiyonao Nakamura
- Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Yukinori Matsuo
- Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Takashi Mizowaki
- Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| |
Collapse
|
3
|
Baumann KS, Kaupa S, Bach C, Engenhart-Cabillic R, Zink K. Monte Carlo calculation of perturbation correction factors for air-filled ionization chambers in clinical proton beams using TOPAS/GEANT. Z Med Phys 2021; 31:175-191. [PMID: 33775521 DOI: 10.1016/j.zemedi.2020.08.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Revised: 08/20/2020] [Accepted: 08/31/2020] [Indexed: 10/21/2022]
Abstract
INTRODUCTION Current dosimetry protocols for clinical protons using air-filled ionization chambers assume that the perturbation correction factor is equal to unity for all ionization chambers and proton energies. Since previous Monte Carlo based studies suggest that perturbation correction factors might be significantly different from unity this study aims to determine perturbation correction factors for six plane-parallel and four cylindrical ionization chambers in proton beams at clinical energies. MATERIALS AND METHODS The dose deposited in the air cavity of the ionization chambers was calculated with the help of the Monte Carlo code TOPAS/Geant4 while specific constructive details of the chambers were removed step by step. By comparing these dose values the individual perturbation correction factors pcel, pstem, psleeve, pwall, pcav⋅pdis as well as the total perturbation correction factor pQ were derived for typical clinical proton energies between 80 and 250MeV. RESULTS The total perturbation correction factor pQ was smaller than unity for almost every ionization chamber and proton energy and in some cases significantly different from unity (deviation larger than 1%). The maximum deviation from unity was 2.0% for cylindrical and 1.5% for plane-parallel ionization chambers. Especially the factor pwall was found to differ significantly from unity. It was shown that this is due to the fact that secondary particles, especially alpha particles and fragments, are scattered from the chamber wall into the air cavity resulting in an overresponse of the chamber. CONCLUSION Perturbation correction factors for ionization chambers in proton beams were calculated using Monte Carlo simulations. In contrast to the assumption of current dosimetry protocols the total perturbation correction factor pQ can be significantly different from unity. Hence, beam quality correction factors [Formula: see text] that are calculated with the help of perturbation correction factors that are assumed to be unity come with a corresponding additional uncertainty.
Collapse
Affiliation(s)
- Kilian-Simon Baumann
- University Medical Center Giessen-Marburg, Department of Radiotherapy and Radiooncology, Marburg, Germany; University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany; Marburg Ion-Beam Therapy Center (MIT), Marburg, Germany.
| | - Sina Kaupa
- University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany
| | - Constantin Bach
- University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany
| | - Rita Engenhart-Cabillic
- University Medical Center Giessen-Marburg, Department of Radiotherapy and Radiooncology, Marburg, Germany; Marburg Ion-Beam Therapy Center (MIT), Marburg, Germany
| | - Klemens Zink
- University Medical Center Giessen-Marburg, Department of Radiotherapy and Radiooncology, Marburg, Germany; University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany; Marburg Ion-Beam Therapy Center (MIT), Marburg, Germany; Frankfurt Institute of Advanced Studies - FIAS, Frankfurt, Germany
| |
Collapse
|
4
|
Ito S, Araki F, Ohno T. Impact of transverse magnetic fields on dose response of a radiophotoluminescent glass dosimeter in megavoltage photon beams. Med Phys 2020; 47:1995-2004. [DOI: 10.1002/mp.14054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Revised: 01/13/2020] [Accepted: 01/20/2020] [Indexed: 11/10/2022] Open
Affiliation(s)
- Shotaro Ito
- Graduate school of Health Sciences Kumamoto University 4‐24‐1 Kuhonji, Chuo‐ku Kumamoto 862‐0976Japan
| | - Fujio Araki
- Department of Health Sciences Faculty of Life Sciences Kumamoto University 4‐24‐1 Kuhonji, Chuo‐ku Kumamoto 862‐0976Japan
| | - Takeshi Ohno
- Department of Health Sciences Faculty of Life Sciences Kumamoto University 4‐24‐1 Kuhonji, Chuo‐ku Kumamoto 862‐0976Japan
| |
Collapse
|
5
|
Nakaguchi Y, Nakamura Y, Yotsuji Y. Validation of secondary dose calculation system with manufacturer-provided reference beam data using heterogeneous phantoms. Radiol Phys Technol 2019; 12:126-135. [PMID: 30684237 DOI: 10.1007/s12194-019-00499-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 01/16/2019] [Accepted: 01/19/2019] [Indexed: 10/27/2022]
Abstract
The Mobius3D (M3D) system (Mobius Medical Systems) is a second-check dosimetry system. We investigated the dose calculation accuracy of this system using heterogeneous phantoms with reference beam data provided by the manufacturer using simple and patient plans. We compared the dose distributions between M3D and the treatment planning system, as well as the measurements in solid water phantoms, heterogeneous phantoms, and patient plans for Varian and Elekta accelerators. The M3D results agreed well with the measurements in the solid water phantoms for the simple plans. However, the accuracy of M3D appeared to depend on the type of accelerator, as indicated by the slight differences in the dose measurements. Furthermore, the M3D dose measurements differed by 5-10% in the lung and bone regions. Regarding the patient plans, we confirmed that M3D is reasonably accurate as a second-check system, despite the slight accelerator type-dependent dose difference.
Collapse
Affiliation(s)
- Yuji Nakaguchi
- Department of Radiological Technology, Kumamoto University Hospital, 1-1-1 Honjyo, Kumamoto, Japan.
| | - Yuya Nakamura
- Department of Radiological Technology, Kumamoto University Hospital, 1-1-1 Honjyo, Kumamoto, Japan
| | - Yohei Yotsuji
- Department of Radiological Technology, Kumamoto University Hospital, 1-1-1 Honjyo, Kumamoto, Japan
| |
Collapse
|
6
|
Matsuoka T, Araki F, Ohno T, Sakata J, Tominaga H. Dependence of volume dose indices on dose calculation algorithms for VMAT-SBRT plans for peripheral lung tumor. Med Dosim 2018; 44:284-290. [PMID: 30455092 DOI: 10.1016/j.meddos.2018.10.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2018] [Revised: 10/20/2018] [Accepted: 10/23/2018] [Indexed: 11/24/2022]
Abstract
The purpose of this study was to investigate the dependence of volume dose indices on dose calculation algorithms for volumetric modulated arc therapy (VMAT) for stereotactic body radiotherapy (SBRT) plans to treat peripheral lung tumors by comparing them with those of Monte Carlo (MC) calculations. VMAT-SBRT plans for peripheral lung tumors were created using the Eclipse treatment planning system (TPS) for 24 patients with nonsmall cell lung cancer. VMAT dose distributions for gross tumor volume (GTV), internal target volume (ITV), and planning target volume (PTV) were calculated using the analytical anisotropic algorithm (AAA), the Acuros XB (AXB) algorithm, and a MC algorithm. VMAT dose distributions of the 3 algorithms were compared using their volume dose indices from dose volume histograms (DVHs), a dose difference map, and 3-dimensional gamma analysis. The DVHs for GTV and ITV from AAA, AXB, and MC were in good agreement. The difference between the ITV and PTV volume dose indices from AAA and MC increased as D98, D95, D80, D50, and D2. In particular, the difference between D98 for PTV from AAA and MC was up to 48%. A >5% difference between D95 for PTV from AAA and MC was 11 patients, but only 2 patients for ITV. The volume dose indices for AXB were near those of MC. AAA tended to overestimate the PTV volume dose indices compared to AXB and MC. Thus, we propose that the volume dose indices for the ITV be used because they are independent of dose calculation algorithms.
Collapse
Affiliation(s)
- Takanori Matsuoka
- Graduate School of Health Sciences, Kumamoto University, Kumamoto, Japan
| | - Fujio Araki
- Department of Health Sciences, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.
| | - Takeshi Ohno
- Department of Health Sciences, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | | | | |
Collapse
|
7
|
Archibald-Heeren BR, Byrne MV, Hu Y, Cai M, Wang Y. Robust optimization of VMAT for lung cancer: Dosimetric implications of motion compensation techniques. J Appl Clin Med Phys 2017; 18:104-116. [PMID: 28786213 PMCID: PMC5874938 DOI: 10.1002/acm2.12142] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Revised: 06/01/2017] [Accepted: 06/02/2017] [Indexed: 12/25/2022] Open
Abstract
In inverse planning of lung radiotherapy, techniques are required to ensure dose coverage of target disease in the presence of tumor motion as a result of respiration. A range of published techniques for mitigating motion effects were compared for dose stability across 5 breath cycles of ±2 cm. Techniques included planning target volume (PTV) expansions, internal target volumes with (OITV) and without tissue override (ITV), average dataset scans (ADS), and mini-max robust optimization. Volumetric arc therapy plans were created on a thorax phantom and verified with chamber and film measurements. Dose stability was compared by DVH analysis in calculations across all geometries. The lung override technique resulted in a substantial lack of dose coverage (-10%) to the tumor in the presence of large motion. PTV, ITV and ADS techniques resulted in substantial (up to 25%) maximum dose increases where solid tissue travelled into low density optimized regions. The results highlight the need for care in optimization of highly heterogeneous where density variations may occur with motion. Robust optimization was shown to provide greater stability in both maximum (<3%) and minimum dose variations (<2%) over all other techniques.
Collapse
Affiliation(s)
- Ben R Archibald-Heeren
- Radiation Oncology Centre, Sydney Adventist Hospital, Sydney, NSW, Australia.,Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - Mikel V Byrne
- Radiation Oncology Centre, Sydney Adventist Hospital, Sydney, NSW, Australia
| | - Yunfei Hu
- Radiation Oncology Centre, Sydney Adventist Hospital, Sydney, NSW, Australia.,Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - Meng Cai
- Radiation Oncology Centre, Sydney Adventist Hospital, Sydney, NSW, Australia.,Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - Yang Wang
- Radiation Oncology Centre, Sydney Adventist Hospital, Sydney, NSW, Australia.,Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| |
Collapse
|
8
|
Hu Y, Byrne M, Archibald-Heeren B, Squires M, Teh A, Seiffert K, Cheers S, Wang Y. A Feasibility Study on the Use of TomoTherapy Megavoltage Computed Tomography Images for Palliative Patient Treatment Planning. J Med Phys 2017; 42:163-170. [PMID: 28974863 PMCID: PMC5618464 DOI: 10.4103/jmp.jmp_32_17] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 06/12/2017] [Accepted: 06/14/2017] [Indexed: 11/16/2022] Open
Abstract
Dedicated rapid access palliative radiation therapy improves patients' access to care, allowing more timely treatment which would positively impact on quality of life. The TomoTherapy (Accuray, Sunnyvale, CA) system provides megavoltage (MV) fan-beam computed tomography (FBCT) as the image guidance technique, and a module called "statRT" that allows the use of these MV FBCT images for direct planning. The possibility of using this imaging modality for palliative radiotherapy treatment planning is assessed against accepted planning CT standards by performing tests following AAPM TG 66 and an end-to-end measurement. Results have shown that MV FBCT images acquired by TomoTherapy are of sufficient quality for the purpose of target delineation and dose calculation for palliative treatments. Large image noise and extended scan acquisition time are the two main drawbacks, so this imaging modality should only be used for palliative treatments at areas with well-known, easily distinguishable, and relatively immobile targets such as spine and whole brain.
Collapse
Affiliation(s)
- Yunfei Hu
- Radiation Oncology Centres, Gosford, NSW, Australia
| | - Mikel Byrne
- Radiation Oncology Centres, Wahroonga, NSW, Australia
| | | | | | - Amy Teh
- Radiation Oncology Centres, Gosford, NSW, Australia
- Radiation Oncology Centres, Wahroonga, NSW, Australia
| | | | - Sonja Cheers
- Radiation Oncology Centres, Gosford, NSW, Australia
| | - Yang Wang
- Radiation Oncology Centres, Wahroonga, NSW, Australia
| |
Collapse
|
9
|
Accuracy of dose calculation algorithms for virtual heterogeneous phantoms and intensity-modulated radiation therapy in the head and neck. Radiol Phys Technol 2015; 9:77-87. [DOI: 10.1007/s12194-015-0336-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Revised: 10/05/2015] [Accepted: 10/05/2015] [Indexed: 11/29/2022]
|
10
|
Tanny S, Holmes S, Sperling N, Parsai EI. Technical Note: Influence of Compton currents on profile measurements in small-volume ion chambers. Med Phys 2015; 42:5768-72. [DOI: 10.1118/1.4929555] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
|
11
|
Tanny S, Sperling N, Parsai EI. Correction factor measurements for multiple detectors used in small field dosimetry on the Varian Edge radiosurgery system. Med Phys 2015; 42:5370-6. [DOI: 10.1118/1.4928602] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
|
12
|
Hirata K, Nakamura M, Yoshimura M, Mukumoto N, Nakata M, Ito H, Inokuchi H, Matsuo Y, Mizowaki T, Hiraoka M. Dosimetric evaluation of the Acuros XB algorithm for a 4 MV photon beam in head and neck intensity-modulated radiation therapy. J Appl Clin Med Phys 2015. [PMID: 26218997 PMCID: PMC5690026 DOI: 10.1120/jacmp.v16i4.5222] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
In this study, we assessed the differences in the dose distribution of a 4 MV photon beam among different calculation algorithms: the Acuros XB (AXB) algorithm, the analytic anisotropic algorithm (AAA), and the pencil beam convolution (PBC) algorithm (ver. 11.0.31), in phantoms and in clinical intensity‐modulated radiation therapy (IMRT) plans. Homogeneous and heterogeneous, including middle‐, low‐, and high‐density, phantoms were combined to assess the percentage depth dose and lateral dose profiles among AXB, AAA, and PBC. For the phantom containing the low‐density area, AXB was in agreement with measurement within 0.5%, while the greatest differences between the AAA and PBC calculations and measurement were 2.7% and 3.6%, respectively. AXB showed agreement with measurement within 2.5% at the high‐density area, while AAA and PBC overestimated the dose by more than 4.5% and 4.0%, respectively. Furthermore, 15 IMRT plans, calculated using AXB, for oropharyngeal, hypopharyngeal, and laryngeal carcinomas were analyzed. The dose prescription was 70 Gy to 50% of the planning target volume (PVT70). Subsequently, each plan was recalculated using AAA and PBC while maintaining the AXB‐calculated monitor units, leaf motion, and beam arrangement. Additionally, nine hypopharyngeal and laryngeal cancer patients were analyzed in terms of PTV70 for cartilaginous structures (PVT70_cartilage). The doses covering 50% to PTV70 calculated by AAA and PBC were 2.1%±1.0% and 3.7%±0.8% significantly higher than those using AXB, respectively (p<0.01). The increases in doses to PTV70_cartilage calculated by AAA and PBC relative to AXB were 3.9% and 5.3% on average, respectively, and were relatively greater than those in the entire PVT70. AXB was found to be in better agreement with measurement in phantoms in heterogeneous areas for the 4 MV photon beam. Considering AXB as the standard, AAA and PBC overestimated the IMRT dose for head and neck cancer. The dosimetric differences should not be ignored, particularly with cartilaginous structures in PTV. PACS number: 87.55.‐x, 87.55.dk, 87.55.kd
Collapse
|
13
|
Bueno M, Carrasco P, Jornet N, Muñoz-Montplet C, Duch MA. On the suitability of ultrathin detectors for absorbed dose assessment in the presence of high-density heterogeneities. Med Phys 2014; 41:081710. [DOI: 10.1118/1.4886760] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
|