- •In order to estimate patient’s doses around the metallic shield for electron treatment.
- •Use of 3D scanner and printer to fabricate patient’s specific dummy shields.
- •The dummy shields were used to generate metal artifact-free CT images.
- •TPS and Monte Carlo dose calculations on the metal artifact-free CT images and film measurements.
Patient’s CT images taken with metallic shields for radiotherapy suffer from artifacts. Furthermore, the treatment planning system (TPS) has a limitation on accurate dose calculations for high density materials. In this study, a Monte Carlo (MC)-based method was developed to accurately evaluate the dosimetric effect of the metallic shield. Two patients with a commercial tungsten shield of lens and two patients with a custom-made lead shield of lip were chosen to produce their non-metallic dummy shields using 3D scanner and printer. With these dummy shields, we generated artifact-free CT images. The maximum CT number allowed in TPS was assigned to metallic shields. MC simulations with real material information were carried out. In addition, clinically relevant dose-volumetric parameters were calculated for the comparison between MC and TPS. Relative dosimetry was performed using radiochromic films. The dose reductions below metallic structures were shown on MC dose distributions, but not evident on TPS dose distributions. The differences in dose-volumetric parameters of PTV between TPS and MC for eye shield cases were not clearly shown. However, the mean dose of lens from TPS and MC was different. The MC results were in superior agreement with measured data in relative dosimetry. The lens dose could be overestimated by TPS. The differences in dose-volumetric parameters of PTV between TPS and MC were generally larger in lip cases than in eye cases. The developed method is useful in predicting the realistic dose distributions around the organs blocked by the metallic shields.
To read this article in full you will need to make a payment
Purchase one-time access:Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
One-time access price info
- For academic or personal research use, select 'Academic and Personal'
- For corporate R&D use, select 'Corporate R&D Professionals'
Subscribe:Subscribe to Physica Medica: European Journal of Medical Physics
Already a print subscriber? Claim online access
Already an online subscriber? Sign in
Register: Create an account
Institutional Access: Sign in to ScienceDirect
- The Physics of Radiation Therapy.4th ed. Lippincott Williams & Wilkins, Philadelphia2010
- Management of lower lip cancer: a retrospective analysis of 118 patients and review of the literature.Ann Plast Surg. 2003; 50: 43-50
- Back-scattering from metals in superficial therapy with high energy electrons.Brit J Radiol. 1974; 47: 467-470
- Dosimetric evaluation of lead and tungsten eye shields in electron beam treatment.Int J Radiat Oncol. 1996; 35: 599-604
- Evaluation of eye shields made of tungsten and aluminum in high-energy electron beams.Int J Radiat Oncol Biol Phys. 1998; 97: 233-237
- Standard Ophthalmology.7th ed. Igaku-Shoin, Tokyo1998
- Correction of CT artifacts and its influence on Monte Carlo dose calculations.Med Phys. 2007; 34: 2119-2132
- Image reconstruction and the effect on dose calculation for hip prostheses.Med Dosim. 2003; 28: 113-117
- Assessing the effect of electron density in photon dose calculations.Med Phys. 2006; 33: 540-552
- Dosimetric impact of a CT metal artefact suppression algorithm for proton, electron and photon therapies.Phys Med Biol. 2006; 51: 5183-5197
- Application of a dummy eye shield for electron treatment planning.J Radiat Res. 2013; 54: 174-181
- The 3D scanner for measuring body surface area: a simplified calculation in the Chinese adult.Appl Ergon. 2003; 34: 273-278
- Preliminary study of potential for rapid prototype and surface scanned radiotherapy facemask production technique.J Med Eng Technol. 2002; 26: 16-21
- Patient specific 3D printed phantom for IMRT quality assurance.Phys Med Biol. 2014; 59: 5763-5773
- New technique for developing a proton range compensator with use of a 3-dimensional printer.Int J Radiat Oncol. 2014; 88: 453-458
- A Customized bolus produced using a 3-dimensional printer for radiotherapy.PLoS ONE. 2014; 9e110746
- Design and production of 3D printed bolus for electron radiation therapy.J Appl Clin Med Phys. 2014; 15: 194-211
- Clinical implementation of 3D printing in the construction of patient specific bolus for electron beam radiotherapy for non-melanoma skin cancer.Radiother Oncol. 2016; 121: 148-153
- Monte Carlo simulation of backscatter from lead for clinical electron beams using EGSnrc.Med Phys. 2008; 35: 1241-1250
- Dosimetric characteristics of backscattered electrons in lead.Phys Med Biol. 2000; 45: 1841-1849
- Simple calculation of the electron-backscatter factor.Med Phys. 1992; 19: 1423-1426
- Report of the AAPM Task Group No. 105: Issues associated with clinical implementation of Monte Carlo-based photon and electron external beam treatment planning.Med Phys. 2007; 34: 4818-4853
- Fifty years of Monte Carlo simulations for medical physics.Phys Med Biol. 2006; 51: R287-R301
- Monte Carlo modelling of external radiotherapy photon beams.Phys Med Biol. 2003; 48: R107-R164
- 3D electron dose calculation using a Voxel based Monte Carlo algorithm (VMC).Med Phys. 1996; 23: 445-457
- MMC–a high-performance Monte Carlo code for electron beam treatment planning.Phys Med Biol. 1995; 40: 543-574
Walters B, Kawrakow I, Rogers DWO. DOSXYZnrc users manual. NRCC report PIRS-794revB; 2011.
- BEAM: a Monte Carlo code to simulate radiotherapy treatment units.Med Phys. 1995; 22: 503-524
- Solid water as phantom material for dosimetry of electron backscatter using low-energy electron beams: a Monte Carlo evaluation.Med Phys. 2009; 36: 1587-1594
- Design and evaluation of electron beam energy degraders for breast boost irradiation.Radiat Oncol. 2016; 11: 1-10
- Dosimetric effect of internal metallic ports in temporary tissue expanders on postmastectomy radiation therapy: a Monte Carlo study.Phys Med Biol. 2017; 62: 4623-4636
- Using Monte Carlo methods to commission electron beams: a feasibility study.Med Phys. 2002; 29: 771-786
- Monte Carlo simulation for scanning technique with scattering foil free electron beam: a proof of concept study.PLoS ONE. 2017; 12e0177380
- Digital Imaging and Communications in Medicine (DICOM): A Practical Introduction and Survival Guide.Springer, Berlin2008
- Beam coordinate transformations from DICOM to DOSXYZnrc.Phys Med Biol. 2012; 57: N513-N523
- CERR: A computational environment for radiotherapy research.Med Phys. 2003; 30: 979-985
- Volumetric modulated arc therapy: planning and evaluation for prostate cancer cases.Int J Radiat Oncol Biol Phys. 2010; 76: 1456-1462
- Clinical comparison of head and neck and prostate IMRT plans using absorbed dose to medium and absorbed dose to water.Phys Med Biol. 2006; 51: 4967-4980
- Investigation of the clinical potential of scattering foil free electron beams.Phys Med Biol. 2014; 59: 819-836
- Clinical implementation of a Monte Carlo treatment planning system.Med Phys. 1999; 26: 2133-2143
- Review of electron beam therapy physics.Phys Med Biol. 2006; 51: R455-R489
- Calibration of CT Hounsfield units for radiotherapy treatment planning of patients with metallic hip prostheses: the use of the extended CT-scale.Phys Med Biol. 2003; 48: 1591-1603
- Dosimetric considerations for patients with HIP prostheses undergoing pelvic irradiation. Report of the AAPM Radiation Therapy Committee Task Group 63.Med Phys. 2017; 30: 1162-1182
- Full Monte Carlo and measurement-based overall performance assessment of improved clinical implementation of eMC algorithm with emphasis on lower energy range.Phys Med. 2016; 30: 1162-1182
Published online: June 16, 2020
Accepted: June 1, 2020
Received in revised form: May 10, 2020
Received: December 14, 2019
© 2020 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.