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Nikandrovs M, McClean B, Shields L, McCavana P, Vintró LL. Clinical treatment planning for kilovoltage radiotherapy using EGSnrc and Python. J Appl Clin Med Phys 2023; 24:e13832. [PMID: 36444164 PMCID: PMC9924114 DOI: 10.1002/acm2.13832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 09/22/2022] [Accepted: 10/05/2022] [Indexed: 12/02/2022] Open
Abstract
Kilovoltage radiotherapy dose calculations are generally performed with manual point dose calculations based on water dosimetry. Tissue heterogeneities, irregular surfaces, and introduction of lead cutouts for treatment are either not taken into account or crudely approximated in manual calculations. Full Monte Carlo (MC) simulations can account for these limitations but require a validated treatment unit model, accurately segmented patient tissues and a treatment planning interface (TPI) to facilitate the simulation setup and result analysis. EGSnrc was used in this work to create a model of Xstrahl kilovoltage unit extending the range of energies, applicators, and validation parameters previously published. The novel functionality of the Python-based framework developed in this work allowed beam modification using custom lead cutouts and shields, commonly present in kilovoltage treatments, as well as absolute dose normalization using the output of the unit. 3D user-friendly planning interface of the developed framework facilitated non-co-planar beam setups for CT phantom MC simulations in DOSXYZnrc. The MC models of 49 clinical beams showed good agreement with measured and reference data, to within 2% for percentage depth dose curves, 4% for beam profiles at various depths, 2% for backscatter factors, 0.5 mm of absorber material for half-value layers, and 3% for output factors. End-to-end testing of the framework using custom lead cutouts resulted in good agreement to within 3% of absolute dose distribution between simulations and EBT3 GafChromic film measurements. Gamma analysis demonstrated poor agreement at the field edges which was attributed to the limitations of simulating smooth cutout shapes. Dose simulated in a heterogeneous phantom agreed to within 7% with measured values converted using the ratio of mass energy absorption coefficients of appropriate tissues and air.
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Affiliation(s)
- Mihails Nikandrovs
- School of PhysicsUniversity College DublinBelfieldIreland
- St. Lukes Radiation Oncology NetworkDublinIreland
| | - Brendan McClean
- Centre for Physics in Health and MedicineUniversity College DublinBelfieldDublinIreland
- St. Lukes Radiation Oncology NetworkDublinIreland
| | - Laura Shields
- Centre for Physics in Health and MedicineUniversity College DublinBelfieldDublinIreland
- St. Lukes Radiation Oncology NetworkDublinIreland
| | - Patrick McCavana
- Centre for Physics in Health and MedicineUniversity College DublinBelfieldDublinIreland
- St. Lukes Radiation Oncology NetworkDublinIreland
| | - Luis León Vintró
- School of PhysicsUniversity College DublinBelfieldIreland
- Centre for Physics in Health and MedicineUniversity College DublinBelfieldDublinIreland
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Hill R, Healy B, Butler D, Odgers D, Gill S, Lye J, Gorjiara T, Pope D, Hill B. Australasian recommendations for quality assurance in kilovoltage radiation therapy from the Kilovoltage Dosimetry Working Group of the Australasian College of Physical Scientists and Engineers in Medicine. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2018; 41:781-808. [DOI: 10.1007/s13246-018-0692-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Penchev P, Mäder U, Fiebich M, Zink K. Design and evaluation of a Monte Carlo based model of an orthovoltage treatment system. Z Med Phys 2015; 25:341-352. [PMID: 26119861 DOI: 10.1016/j.zemedi.2015.05.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Revised: 05/28/2015] [Accepted: 05/29/2015] [Indexed: 10/23/2022]
Abstract
The aim of this study was to develop a flexible framework of an orthovoltage treatment system capable of calculating and visualizing dose distributions in different phantoms and CT datasets. The framework provides a complete set of various filters, applicators and x-ray energies and therefore can be adapted to varying studies or be used for educational purposes. A dedicated user friendly graphical interface was developed allowing for easy setup of the simulation parameters and visualization of the results. For the Monte Carlo simulations the EGSnrc Monte Carlo code package was used. Building the geometry was accomplished with the help of the EGSnrc C++ class library. The deposited dose was calculated according to the KERMA approximation using the track-length estimator. The validation against measurements showed a good agreement within 4-5% deviation, down to depths of 20% of the depth dose maximum. Furthermore, to show its capabilities, the validated model was used to calculate the dose distribution on two CT datasets. Typical Monte Carlo calculation time for these simulations was about 10 minutes achieving an average statistical uncertainty of 2% on a standard PC. However, this calculation time depends strongly on the used CT dataset, tube potential, filter material/thickness and applicator size.
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Affiliation(s)
- Petar Penchev
- Institute of Medical Physics and Radiation Protection - IMPS University of Applied Sciences, Gießen, Germany.
| | - Ulf Mäder
- Institute of Medical Physics and Radiation Protection - IMPS University of Applied Sciences, Gießen, Germany
| | - Martin Fiebich
- Institute of Medical Physics and Radiation Protection - IMPS University of Applied Sciences, Gießen, Germany
| | - Klemens Zink
- Institute of Medical Physics and Radiation Protection - IMPS University of Applied Sciences, Gießen, Germany; University Hospital Marburg, Department of Radiotherapy and Radiation Oncology, Philipps-University, Marburg, Germany
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Hill R, Healy B, Holloway L, Kuncic Z, Thwaites D, Baldock C. Advances in kilovoltage x-ray beam dosimetry. Phys Med Biol 2014; 59:R183-231. [DOI: 10.1088/0031-9155/59/6/r183] [Citation(s) in RCA: 110] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Mesbahi A, Zakariaee SS. Effect of anode angle on photon beam spectra and depth dose characteristics for X-RAD320 orthovoltage unit. Rep Pract Oncol Radiother 2013; 18:148-52. [PMID: 24416546 DOI: 10.1016/j.rpor.2012.12.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Revised: 09/23/2012] [Accepted: 12/18/2012] [Indexed: 12/01/2022] Open
Abstract
BACKGROUND In radiation therapy with orthovoltage units, the tube design has a crucial effect on its dosimetric features. AIM In this study, the effect of anode angle on photon beam spectra, depth dose and photon fluence per initial electron was studied for a commercial orthovoltage unit of X-RAD320 biological irradiator. MATERIALS AND METHODS The MCNPX MC code was used for modeling in the current study. We used the Monte Carlo method to model the X-RAD320 X-ray unit based on the manufacturer provided information. The MC model was validated by comparing the MC calculated photon beam spectra with the results of SpekCalc software. The photon beam spectra were calculated for anode angles from 15 to 35 degrees. We also calculated the percentage depth doses for some angles to verify the impact of anode angle on depth dose. Additionally, the heel effect and its relation with anode angle were studied for X-RAD320 irradiator. RESULTS Our results showed that the photon beam spectra and their mean energy are changed significantly with anode angle and the optimum anode angle of 30 degrees was selected based on less heel effect and appropriate depth dose and photon fluence per initial electron. CONCLUSION It can be concluded that the anode angle of 30 degrees for X-RAD320 unit used by manufacturer has been selected properly considering the heel effect and dosimetric properties.
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Affiliation(s)
- Asghar Mesbahi
- Medical Physics Department, Medical School, Tabriz University of Medical Sciences, Tabriz, Iran ; Radiation Oncology Department, Imam Hospital, Tabriz, Iran
| | - Seyed-Salman Zakariaee
- Medical Physics Department, Medical School, Tabriz University of Medical Sciences, Tabriz, Iran
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Kusunoki T, Ikeda K. Neuroendocrine Carcinoma Arising in a Wound of the Postoperative Maxillary Sinus. Clin Pract 2012; 2:e16. [PMID: 24765415 PMCID: PMC3981353 DOI: 10.4081/cp.2012.e16] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Revised: 11/02/2011] [Accepted: 01/12/2012] [Indexed: 11/23/2022] Open
Abstract
We report a case of a neuroendocrine carcinoma arising in a wound of the postoperative maxillary sinus that was difficult to distinguish from a postoperative maxillary cyst. The patient was a 65-year-old Japanese woman who complained of left exophthalmos with cheek swelling and eye movement disorders. In past history, she had, 40 years previously undergone operation on the bilateral maxillary sinus by Caldwell-Luc's method. In a preoperative computed tomography, a mass occupied the left maxillary sinus showing irregular densities with destruction of the posterior bone walls and invasion into the left orbital. Both TI and T2 weighted magnetic resonance imaging showed low intensities and unevenness in the mass. We performed a biopsy of the maxillary tumor according to Caldwell-Luc's method. Histological examination diagnosed neuroendocrine carcinoma. Radiation therapy (total 66Gy) resulted in partial response for this tumor. However, sinonasal neuroendocrine carcinoma has been identified as highly aggressive, with a high probability of recurrence and metastasis.
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Chow JCL, Grigorov GN. Effect of the bone heterogeneity on the dose prescription in orthovoltage radiotherapy: A Monte Carlo study. Rep Pract Oncol Radiother 2011; 17:38-43. [PMID: 24376995 DOI: 10.1016/j.rpor.2011.09.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Revised: 08/05/2011] [Accepted: 09/25/2011] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND In orthovoltage radiotherapy, since the dose prescription at the patient's surface is based on the absolute dose calibration using water phantom, deviation of delivered dose is found as the heterogeneity such as bone present under the patient's surface. AIM This study investigated the dosimetric impact due to the bone heterogeneity on the surface dose in orthovoltage radiotherapy. MATERIALS AND METHODS A 220 kVp photon beam with field size of 5 cm diameter, produced by a Gulmay D3225 orthovoltage X-ray machine was modeled by the BEAMnrc. Phantom containing water (thickness = 1-5 mm) on top of a bone (thickness = 1 cm) was irradiated by the 220 kVp photon beam. Percentage depth dose (PDD), surface dose and photon energy spectrum were determined using Monte Carlo simulations (the BEAMnrc code). RESULTS PDD results showed that the maximum bone dose was about 210% higher than the surface dose in the phantoms with different thicknesses of water. Surface dose was found to be increased in the range of 2.5-3.7%, when the distance between the phantom surface and bone was increased in the range of 1-5 mm. The increase of surface dose was found not to follow the increase of water thickness, and the maximum increase of surface dose was found at the thickness of water equal to 3 mm. CONCLUSIONS For the accepted total orthovoltage radiation treatment uncertainty of 5%, a neglected consideration of the bone heterogeneity during the dose prescription in the sites of forehead, chest wall and kneecap with soft tissue thickness = 1-5 mm would cause more than two times of the bone dose, and contribute an uncertainty of about 2.5-3.7% to the total uncertainty in the dose delivery.
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Affiliation(s)
- James C L Chow
- Radiation Medicine Program, Princess Margaret Hospital and Department of Radiation Oncology, University of Toronto, Toronto, ON M5G 2M9, Canada ; Department of Physics, Ryerson University, Toronto, ON M5B 2K3, Canada
| | - Grigor N Grigorov
- Department of Medical Physics, Grand River Regional Cancer Center, Kitchener, ON N2G 1G3, Canada
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D’Alimonte L, Sinclair E, Seed S. Orthovoltage energies for palliative care in the 21st century: Is there a need? Radiography (Lond) 2011. [DOI: 10.1016/j.radi.2010.09.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Terribilini D, Fix MK, Frei D, Volken W, Manser P. VMC++ validation for photon beams in the energy range of 20-1000 keV. Med Phys 2010; 37:5218-27. [PMID: 21089755 DOI: 10.1118/1.3488892] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE In high energy teletherapy, VMC++ is known to be a very accurate and efficient Monte Carlo (MC) code. In principle, the MC method is also a powerful dose calculation tool in other areas in radiation oncology, e.g., brachytherapy or orthovoltage radiotherapy. However, VMC++ is not validated for the low-energy range of such applications. This work aims in the validation of the VMC++ MC code for photon beams in the energy range between 20 and 1000 keV. METHODS Dose calculations were performed in different 40 x 40 x 40 cm3 phantoms of different materials. Dose distributions of monoenergetic (ranging from 20 to 1000 keV) 10 x 10 and 2 x 2 cm2 parallel beams were calculated. Voxel sizes of 4 x 4 x 4 and 1 x 1 x 1 mm3 were used for the dose calculations. The resulting dose distributions were compared to those calculated using EGSnrc, which is used as a golden standard in this work. RESULTS At energies between 100 and 1000 keV, EGSnrc and VMC++ calculated dose distributions agree within the statistical uncertainty of about 1% (1sigma). At energies < or = 50 keV, dose differences of up to 1.6% (in % of D(max)) occur when VMC++ and EGSnrc are compared. Turning off Rayleigh scattering, binding effects for Compton scattering, and the atomic relaxation after photoelectric absorption in EGSnrc (all not implemented in VMC++) leads to an agreement between both MC codes within statistical uncertainty. Further, using the KERMA approximation feature implemented in VMC++ leads to very efficient simulations in the energy range between 20 and 1000 keV. CONCLUSIONS Further improvements for very low energies in accuracy of VMC++ could be achieved by implementing Rayleigh scattering, binding effects for Compton scattering, and the atomic relaxation after photoelectric absorption. Implementation into VMC++ of KERMA approximation has been validated.
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Affiliation(s)
- Dario Terribilini
- Division of Medical Radiation Physics, Inselspital and University of Berne, CH-3010 Berne, Switzerland.
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Bazalova M, Zhou H, Keall PJ, Graves EE. Kilovoltage beam Monte Carlo dose calculations in submillimeter voxels for small animal radiotherapy. Med Phys 2010; 36:4991-9. [PMID: 19994508 DOI: 10.1118/1.3238465] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Small animal conformal radiotherapy (RT) is essential for preclinical cancer research studies and therefore various microRT systems have been recently designed. The aim of this paper is to efficiently calculate the dose delivered using our microRT system based on a microCT scanner with the Monte Carlo (MC) method and to compare the MC calculations to film measurements. METHODS Doses from 2-30 mm diameter 120 kVp photon beams deposited in a solid water phantom with 0.2 x 0.2 x 0.2 mm3 voxels are calculated using the latest versions of the EGSnrc codes BEAMNRC and DOSXYZNRC. Two dose calculation approaches are studied: a two-step approach using phase-space files and direct dose calculation with BEAMNRC simulation sources. Due to the small beam size and submillimeter voxel size resulting in long calculation times, variance reduction techniques are studied. The optimum bremsstrahlung splitting number (NBRSPL in BEAMNRC) and the optimum DOSXYZNRC photon splitting (Nsplit) number are examined for both calculation approaches and various beam sizes. The dose calculation efficiencies and the required number of histories to achieve 1% statistical uncertainty--with no particle recycling--are evaluated for 2-30 mm beams. As a final step, film dose measurements are compared to MC calculated dose distributions. RESULTS The optimum NBRSPL is approximately 1 x 10(6) for both dose calculation approaches. For the dose calculations with phase-space files, Nsplit varies only slightly for 2-30 mm beams and is established to be 300. Nsplit for the DOSXYZNRC calculation with the BEAMNRC source ranges from 300 for the 30 mm beam to 4000 for the 2 mm beam. The calculation time significantly increases for small beam sizes when the BEAMNRC simulation source is used compared to the simulations with phase-space files. For the 2 and 30 mm beams, the dose calculations with phase-space files are more efficient than the dose calculations with BEAMNRC sources by factors of 54 and 1.6, respectively. The dose calculation efficiencies converge for beams with diameters larger than 30 mm. CONCLUSIONS A very good agreement of MC calculated dose distributions to film measurements is found. The mean difference of percentage depth dose curves between calculated and measured data for 2, 5, 10, and 20 mm beams is 1.8%.
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Affiliation(s)
- Magdalena Bazalova
- Department of Radiation Oncology, Molecular Imaging Program at Stanford, Stanford University, Stanford, California 94305, USA.
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Jiang H, Seco J, Paganetti H. Effects of Hounsfield number conversion on CT based proton Monte Carlo dose calculations. Med Phys 2007; 34:1439-49. [PMID: 17500475 PMCID: PMC2292645 DOI: 10.1118/1.2715481] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The Monte Carlo method provides the most accurate dose calculations on a patient computed tomography (CT) geometry. The increase in accuracy is, at least in part, due to the fact that instead of treating human tissues as water of various densities as in analytical algorithms, the Monte Carlo method allows human tissues to be characterized by elemental composition and mass density, and hence allows the accurate consideration of all relevant electromagnetic and nuclear interactions. On the other hand, the algorithm to convert CT Hounsfield numbers to tissue materials for Monte Carlo dose calculation introduces uncertainties. There is not a simple one to one correspondence between Hounsfield numbers and tissue materials. To investigate the effects of Hounsfield number conversion for proton Monte Carlo dose calculations, clinical proton treatment plans were simulated using the Geant4 Monte Carlo code. Three Hounsfield number to material conversion methods were studied. The results were compared in forms of dose volume histograms of gross tumor volume and clinical target volume. The differences found are generally small but can be dosimetrically significant. Further, different methods may cause deviations in the predicted proton beam range in particular for deep proton fields. Typically, slight discrepancies in mass density assignments play only a minor role in the target region, whereas more significant effects are caused by different assignments in elemental compositions. In the presence of large tissue inhomogeneities, for head and neck treatments, treatment planning decisions could be affected by these differences because of deviations in the predicted tumor coverage. Outside the target area, differences in elemental composition and mass density assignments both may play a role. This can lead to pronounced effects for organs at risk, in particular in the spread-out Bragg peak penumbra or distal regions. In addition, the significance of the elemental composition effect (dose to water vs. dose to tissue) is tissue-type dependent and is also affected by nuclear reactions.
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Affiliation(s)
| | - Joao Seco
- Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts
| | - Harald Paganetti
- Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts
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Demarco JJ, Chetty IJ, Solberg TD. A Monte Carlo tutorial and the application for radiotherapy treatment planning. Med Dosim 2002; 27:43-50. [PMID: 12019965 DOI: 10.1016/s0958-3947(02)00087-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Monte Carlo-based treatment planning algorithms are advancing rapidly and will certainly be implemented as part of conventional treatment planning systems in the near future. This paper was designed as a basic tutorial for using the Monte Carlo method as applied to radiotherapy treatment planning. The tutorial addresses the basic transport differences between photon and electron transport as well as the sampling distributions. The implementation of a virtual linac source model and the conversion from the Monte Carlo source modeling reference plane into the treatment reference plane is discussed. The implementation of a thresholding algorithm for converting CT electron density to patient specific materials is also presented. A 6-field prostate boost treatment is used to compare a conventional treatment planning algorithm (pencil beam model) with a Monte Carlo simulation algorithm. The agreement between the 2 calculation methods is good based upon the qualitative comparison of the isodose distribution and the dose-volume histograms for the prostate and the rectum. The effects of statistical uncertainty on the Monte Carlo calculation are also presented.
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Affiliation(s)
- J J Demarco
- UCLA Department of Radiation Oncology, University of California Los Angeles, 90095-6951, USA.
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Abstract
This article describes photon beam Monte Carlo simulation for multi leaf collimator (MLC)-based intensity-modulated radiotherapy (IMRT). We present the general aspects of the Monte Carlo method for the non-Monte Carloist with an emphasis given to patient-specific radiotherapy application. Patient-specific application of the Monte Carlo method can be used for IMRT dose verification, inverse planning, and forward planning in conventional conformal radiotherapy. Because it is difficult to measure IMRT dose distributions in heterogeneous phantoms that approximate a patient, Monte Carlo methods can be used to verify IMRT dose distributions that are calculated using conventional methods. Furthermore, using Monte Carlo as the dose calculation method for inverse planning results in better-optimized treatment plans. We describe both aspects and present our recent results to illustrate the discussion. Finally, we present current issues related to clinical implementation of Monte Carlo dose calculation. Monte Carlo is the most recent, and most accurate, method of radiotherapy dose calculation. It is currently in the process of being implemented by various treatment planning vendors and will be available for clinical use in the immediate future.
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Affiliation(s)
- T Pawlicki
- Department of Radiation Oncology, Stanford University School of Medicine, CA 94305-5304, USA.
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Ioppolo JL, Price RI, Tuchyna T, Buckley CE. Diagnostic x-ray dosimetry using Monte Carlo simulation. Phys Med Biol 2002; 47:1707-20. [PMID: 12069088 DOI: 10.1088/0031-9155/47/10/307] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
An Electron Gamma Shower version 4 (EGS4) based user code was developed to simulate the absorbed dose in humans during routine diagnostic radiological procedures. Measurements of absorbed dose using thermoluminescent dosimeters (TLDs) were compared directly with EGS4 simulations of absorbed dose in homogeneous, heterogeneous and anthropomorphic phantoms. Realistic voxel-based models characterizing the geometry of the phantoms were used as input to the EGS4 code. The voxel geometry of the anthropomorphic Rando phantom was derived from a CT scan of Rando. The 100 kVp diagnostic energy x-ray spectra of the apparatus used to irradiate the phantoms were measured, and provided as input to the EGS4 code. The TLDs were placed at evenly spaced points symmetrically about the central beam axis, which was perpendicular to the cathode-anode x-ray axis at a number of depths. The TLD measurements in the homogeneous and heterogenous phantoms were on average within 7% of the values calculated by EGS4. Estimates of effective dose with errors less than 10% required fewer numbers of photon histories (1 x 10(7)) than required for the calculation of dose profiles (1 x 10(9)). The EGS4 code was able to satisfactorily predict and thereby provide an instrument for reducing patient and staff effective dose imparted during radiological investigations.
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Affiliation(s)
- J L Ioppolo
- Medical Technology and Physics Department, Sir Charles Gairdner Hospital, Nedlands, WA, Australia.
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Reino AJ. Factors in the pathogenesis of tumors of the sphenoid and maxillary sinuses: a comparative study. Laryngoscope 2000; 110:1-38. [PMID: 11037807 DOI: 10.1097/00005537-200010001-00001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES/HYPOTHESIS To explain the processes that lead to the development of tumors in the maxillary and sphenoid sinuses. STUDY DESIGN A 32-year review of the world's literature on neoplasms of these two sinuses and a randomized case-controlled study comparing the normal mucosal architecture of the maxillary to the sphenoid sinus. METHODS Analysis of a 32-year world literature review reporting series of cases of maxillary and sphenoid sinus tumors. Tumors were classified by histological type and separated into subgroups if an individual incidence rate was reported. Histomorphometry of normal maxillary and sphenoid sinus mucosa was performed in 14 randomly selected patients (10 sphenoid and 4 maxillary specimens). Specimens were fixed in 10% formalin, embedded in paraffin, and stained with periodic acid-Schiff (PAS) and hematoxylin. Histomorphometric analysis was performed with a Zeiss Axioscope light microscope (Carl Zeiss Inc., Thornwood, NY) mounted with a Hamamatsu (Hamamatsu Photonics, Tokyo, Japan) color-chilled 3 charge coupled device digital camera. The images were captured on a 17-inch Sony (Sony Corp., Tokyo, Japan) multiscan monitor and analyzed with a Samba 4000 Image Analysis Program (Samba Corp., Los Angeles, CA). Five random areas were selected from strips of epithelium removed from each sinus, and goblet and basal cell measurements were made at magnifications x 100 and x 400. RESULTS The literature review revealed that the number and variety of tumors in the maxillary sinus are much greater than those in the sphenoid. The incidence of metastatic lesions to each sinus is approximately equal. No recognized pattern of spread from any particular organ system could be determined. On histomorphometric study there were no statistically significant differences between the sinuses in the concentration of goblet cells, basal cells, or seromucinous glands. CONCLUSIONS Factors involved in the pathogenesis of tumors of the maxillary and sphenoid sinuses include differences in nasal physiology, embryology, morphology, and topography. There are no significant histological differences in the epithelium and submucous glands between the two sinuses to explain the dissimilar formation of neoplasms.
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Affiliation(s)
- A J Reino
- Manhattan Ear, Nose and Throat Associates, New York, New York 10128, USA
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Schneider W, Bortfeld T, Schlegel W. Correlation between CT numbers and tissue parameters needed for Monte Carlo simulations of clinical dose distributions. Phys Med Biol 2000; 45:459-78. [PMID: 10701515 DOI: 10.1088/0031-9155/45/2/314] [Citation(s) in RCA: 489] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
We describe a new method to convert CT numbers into mass density and elemental weights of tissues required as input for dose calculations with Monte Carlo codes such as EGS4. As a first step, we calculate the CT numbers for 71 human tissues. To reduce the effort for the necessary fits of the CT numbers to mass density and elemental weights, we establish four sections on the CT number scale, each confined by selected tissues. Within each section, the mass density and elemental weights of the selected tissues are interpolated. For this purpose, functional relationships between the CT number and each of the tissue parameters, valid for media which are composed of only two components in varying proportions, are derived. Compared with conventional data fits, no loss of accuracy is accepted when using the interpolation functions. Assuming plausible values for the deviations of calculated and measured CT numbers, the mass density can be determined with an accuracy better than 0.04 g cm(-3). The weights of phosphorus and calcium can be determined with maximum uncertainties of 1 or 2.3 percentage points (pp) respectively. Similar values can be achieved for hydrogen (0.8 pp) and nitrogen (3 pp). For carbon and oxygen weights, errors up to 14 pp can occur. The influence of the elemental weights on the results of Monte Carlo dose calculations is investigated and discussed.
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Affiliation(s)
- W Schneider
- Department of Medical Physics, Deutsches Krebsforschungszentrum, Heidelberg, Germany
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