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Haba T, Nishihara Y, Saito Y, Tomimura T, Ogawa S, Tanabe K, Asada Y, Kobayashi M, Koyama S. Estimating organ dose with optimized peak dose index in cone-beam CT scans. Phys Med 2024; 118:103215. [PMID: 38224662 DOI: 10.1016/j.ejmp.2024.103215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 12/20/2023] [Accepted: 01/05/2024] [Indexed: 01/17/2024] Open
Abstract
PURPOSE Organ dose evaluation is important for optimizing cone beam computed tomography (CBCT) scan protocols. However, an evaluation method for various CBCT scanners is yet to be established. In this study, we developed scanner-independent conversion coefficients to estimate organ doses using appropriate peak dose (f(0)) indices. METHODS This study included various scanners (angiography scanners and linear accelerators) and protocols for the head and body (thorax, abdomen, and pelvis) scan regions. f(0) was measured at five conventional positions (center position (f(0)c) and four peripheral positions (f(0)p) at 90° intervals) in the CT dose index (CTDI) phantom. To identify appropriate measurement positions for organ dose estimation, various f(0) indices were considered. Organ doses were measured by using optically stimulated luminescence dosimeters positioned in an anthropomorphic phantom. Thereafter, the conversion coefficients were calculated from each obtained f(0) value and organ or tissue dose using a linear fit for all scanners, and the coefficient of variation (CV) of the conversion coefficients was calculated for each organ or tissue. The f(0) index with the minimum CV value was proposed as the appropriate index. RESULTS The appropriate f(0) index was determined as f(0)c for the body region and a maximum of four f(0)p values for the head region. Using the proposed conversion coefficients based on the appropriate f(0) index, the organ/tissue doses were well estimated with a mean error of 14.2% across all scanners and scan regions. CONCLUSIONS The proposed scanner-independent coefficients are useful for organ dose evaluation using CBCT scanners.
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Affiliation(s)
- Tomonobu Haba
- Faculty of Radiological Technology, School of Medical Science, Fujita Health University, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan.
| | - Yusei Nishihara
- Department of Radiology, Fujita Health University Hospital, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan
| | - Yasunori Saito
- Department of Radiology, Fujita Health University Hospital, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan
| | - Takeshi Tomimura
- Department of Radiology, Fujita Health University Hospital, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan
| | - Shuta Ogawa
- Department of Radiology, Fujita Health University Hospital, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan
| | - Kaho Tanabe
- Faculty of Radiological Technology, School of Medical Science, Fujita Health University, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan
| | - Yasuki Asada
- Faculty of Radiological Technology, School of Medical Science, Fujita Health University, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan
| | - Masanao Kobayashi
- Faculty of Radiological Technology, School of Medical Science, Fujita Health University, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan
| | - Shuji Koyama
- Brain & Mind Research Center, Nagoya University, 1-1-20 Daiko-Minami, Higashi-ku, Nagoya, Aichi, Japan
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Shimomura T, Fujiwara D, Inoue Y, Takeya A, Ohta T, Nozawa Y, Imae T, Nawa K, Nakagawa K, Haga A. Virtual cone-beam computed tomography simulator with human phantom library and its application to the elemental material decomposition. Phys Med 2023; 113:102648. [PMID: 37672845 DOI: 10.1016/j.ejmp.2023.102648] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 06/19/2023] [Accepted: 07/29/2023] [Indexed: 09/08/2023] Open
Abstract
PURPOSE The purpose of this study is to develop a virtual CBCT simulator with a head and neck (HN) human phantom library and to demonstrate the feasibility of elemental material decomposition (EMD) for quantitative CBCT imaging using this virtual simulator. METHODS The library of 36 HN human phantoms were developed by extending the ICRP 110 adult phantoms based on human age, height, and weight statistics. To create the CBCT database for the library, a virtual CBCT simulator that simulated the direct and scattered X-ray on a flat panel detector using ray-tracing and deep-learning (DL) models was used. Gaussian distributed noise was also included on the flat panel detector, which was evaluated using a real CBCT system. The usefulness of the virtual CBCT system was demonstrated through the application of the developed DL-based EMD model for case involving virtual phantom and real patient. RESULTS The virtual simulator could generate various virtual CBCT images based on the human phantom library, and the prediction of the EMD could be successfully performed by preparing the CBCT database from the proposed virtual system, even for a real patient. The CBCT image degradation owing to the scattered X-ray and the statistical noise affected the prediction accuracy, although these effects were minimal. Furthermore, the elemental distribution using the real CBCT image was also predictable. CONCLUSIONS This study demonstrated the potential of using computer vision for medical data preparation and analysis, which could have important implications for improving patient outcomes, especially in adaptive radiation therapy.
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Affiliation(s)
- Taisei Shimomura
- Graduate School of Biomedical Sciences, Tokushima University, Tokushima 770-8503, Japan; Department of Radiology, The University of Tokyo Hospital, Bunkyo, Tokyo 113-8655, Japan
| | - Daiyu Fujiwara
- Graduate School of Biomedical Sciences, Tokushima University, Tokushima 770-8503, Japan
| | - Yuki Inoue
- Graduate School of Biomedical Sciences, Tokushima University, Tokushima 770-8503, Japan
| | - Atsushi Takeya
- Graduate School of Biomedical Sciences, Tokushima University, Tokushima 770-8503, Japan
| | - Takeshi Ohta
- Department of Radiology, The University of Tokyo Hospital, Bunkyo, Tokyo 113-8655, Japan
| | - Yuki Nozawa
- Department of Radiology, The University of Tokyo Hospital, Bunkyo, Tokyo 113-8655, Japan
| | - Toshikazu Imae
- Department of Radiology, The University of Tokyo Hospital, Bunkyo, Tokyo 113-8655, Japan
| | - Kanabu Nawa
- Department of Radiology, The University of Tokyo Hospital, Bunkyo, Tokyo 113-8655, Japan
| | - Keiichi Nakagawa
- Department of Radiology, The University of Tokyo Hospital, Bunkyo, Tokyo 113-8655, Japan
| | - Akihiro Haga
- Graduate School of Biomedical Sciences, Tokushima University, Tokushima 770-8503, Japan.
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Wang C, Lin X, Liu H, Fu J, Zhuo W, Liu H. Construction of a computational MDCT model for simulations of the detector signals. RADIATION MEDICINE AND PROTECTION 2023. [DOI: 10.1016/j.radmp.2023.02.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023] Open
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Higuchi T, Haga A. X-ray energy spectrum estimation based on a virtual computed tomography system. Biomed Phys Eng Express 2023; 9. [PMID: 36623292 DOI: 10.1088/2057-1976/acb158] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Accepted: 01/09/2023] [Indexed: 01/11/2023]
Abstract
This paper presents a method for estimating the x-ray energy spectrum for computed tomography (CT) in the diagnostic energy range from the reconstructed CT image itself. To this end, a virtual CT system was developed, and datasets, including CT images for the Gammex phantom labeled by the corresponding energy spectra, were generated. Using these datasets, an artificial neural network (ANN) model was trained to reproduce the energy spectrum from the CT values in the Gammex inserts. In the actual application, an aluminum-based bow-tie filter was used in the virtual CT system, and an ANN model with a bow-tie filter was also developed. Both ANN models without/with a bow-tie filter can estimate the x-ray spectrum within the agreement, which is defined as one minus the absolute error, of more than 80% on average. The agreement increases as the tube voltage increases. The estimation was occasionally inaccurate when the amount of noise on the CT image was considerable. Image quality with a signal-to-noise ratio of more than 10 for the basis material of the Gammex phantom was required to predict the spectrum accurately. Based on the experimental data acquired from Activion16 (Canon Medical System, Japan), the ANN model with a bow-tie filter produced a reasonable energy spectrum by simultaneous optimization of the shape of the bow-tie filter. The present method requires a CT image for the Gammex phantom only, and no special setup, thus it is expected to be readily applied in clinical applications, such as beam hardening reduction, CT dose management, and material decomposition, all of which require exact information on the x-ray energy spectrum.
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Affiliation(s)
- Takayuki Higuchi
- Department of Biomedical Sciences, Tokushima University, Tokushima 770-8503, Japan
| | - Akihiro Haga
- Department of Biomedical Sciences, Tokushima University, Tokushima 770-8503, Japan
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Monte-Carlo techniques for radiotherapy applications II: equipment and source modelling, dose calculations and radiobiology. JOURNAL OF RADIOTHERAPY IN PRACTICE 2023. [DOI: 10.1017/s1460396923000080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/05/2023]
Abstract
Abstract
Introduction:
This is the second of two papers giving an overview of the use of Monte-Carlo techniques for radiotherapy applications.
Methods:
The first paper gave an introduction and introduced some of the codes that are available to the user wishing to model the different aspects of radiotherapy treatment. It also aims to serve as a useful companion to a curated collection of papers on Monte-Carlo that have been published in this journal.
Results and Conclusions:
This paper focuses on the application of Monte-Carlo to specific problems in radiotherapy. These include radiotherapy and imaging beam production, brachytherapy, phantom and patient dosimetry, detector modelling and track structure calculations for micro-dosimetry, nano-dosimetry and radiobiology.
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Martin CJ, Abuhaimed A. Variations in size-specific effective dose with patient stature and beam width for kV cone beam CT imaging in radiotherapy. JOURNAL OF RADIOLOGICAL PROTECTION : OFFICIAL JOURNAL OF THE SOCIETY FOR RADIOLOGICAL PROTECTION 2022; 42:031512. [PMID: 35917802 DOI: 10.1088/1361-6498/ac85fa] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Accepted: 08/02/2022] [Indexed: 06/15/2023]
Abstract
The facilities now available on linear accelerators for external beam radiotherapy enable radiation fields to be conformed to the shapes of tumours with a high level of precision. However, in order for the treatment delivered to take advantage of this, the patient must be positioned on the couch with the same degree of accuracy. Kilovoltage cone beam computed tomography systems are now incorporated into radiotherapy linear accelerators to allow imaging to be performed at the time of treatment, and image-guided radiation therapy is now standard in most radiotherapy departments throughout the world. However, because doses from imaging are much lower than therapy doses, less effort has been put into optimising radiological protection of imaging protocols. Standard imaging protocols supplied by the equipment vendor are often used with little adaptation to the stature of individual patients, and exposure factors and field sizes are frequently larger than necessary. In this study, the impact of using standard protocols for imaging anatomical phantoms of varying size from a library of 193 adult phantoms has been evaluated. Monte Carlo simulations were used to calculate doses for organs and tissues for each phantom, and results combined in terms of size-specific effective dose (SED). Values of SED from pelvic scans ranged from 11 mSv to 22 mSv for male phantoms and 8 mSv to 18 mSv for female phantoms, and for chest scans from 3.8 mSv to 7.6 mSv for male phantoms and 4.6 mSv to 9.5 mSv for female phantoms. Analysis of the results showed that if the same exposure parameters and field sizes are used, a person who is 5 cm shorter will receive a size SED that is 3%-10% greater, while a person who is 10 kg lighter will receive a dose that is 10%-14% greater compared with the average size.
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Affiliation(s)
- C J Martin
- Department of Clinical Physics and Bioengineering, University of Glasgow, Gartnavel Royal Hospital, Glasgow G12 0XH, United Kingdom
| | - A Abuhaimed
- King Abdulaziz City for Science and Technology (KACST), Riyadh, Saudi Arabia
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Heidarloo N, Mahmoud Reza Aghamiri S, Saghamanesh S, Azma Z, Alaei P. A novel analytical method for computing dose from kilovoltage beams used in Image-Guided radiation therapy. Phys Med 2022; 96:54-61. [PMID: 35219962 DOI: 10.1016/j.ejmp.2022.02.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 02/12/2022] [Accepted: 02/20/2022] [Indexed: 10/19/2022] Open
Abstract
PURPOSE A modified convolution/superposition algorithm is proposed to compute dose from the kilovoltage beams used in IGRT. The algorithm uses material-specific energy deposition kernels instead of water-energy deposition kernels. METHODS Monte Carlo simulation was used to model the Elekta XVI unit and determine dose deposition characteristics of its kilovoltage beams. The dosimetric results were compared with ion chamber measurements. The dose from the kilovoltage beams was then computed using convolution/superposition along with material-specific energy deposition kernels and compared with Monte Carlo and measurements. The material-specific energy deposition kernels were previously generated using Monte Carlo. RESULTS The obtained gamma indices (using 2%/2mm criteria for 95% of points) were lower than 1 in almost all instances which indicates good agreement between simulated and measured depth doses and profiles. The comparisons of the algorithm with measurements in a homogeneous solid water slab phantom, and that with Monte Carlo in a head and neck CT dataset produced acceptable results. The calculated point doses were within 4.2% of measurements in the homogeneous phantom. Gamma analysis of the calculated vs. Monte Carlo simulations in the head and neck phantom resulted in 94% of points passing with a 2%/2mm criteria. CONCLUSIONS The proposed method offers sufficient accuracy in kilovoltage beams dose calculations and has the potential to supplement the conventional megavoltage convolution/superposition algorithms for dose calculations in low energy range.
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Affiliation(s)
- Nematollah Heidarloo
- Department of Medical Radiation Engineering, Shahid Beheshti University, Tehran, Iran
| | | | - Somayeh Saghamanesh
- Center for X-ray Analytics, Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland
| | - Zohreh Azma
- Department of Medical Radiation Engineering, Shahid Beheshti University, Tehran, Iran; Erfan Radiation Oncology Center, Erfan-Niyayesh hospital, Iran University of Medical Science, Tehran, Iran
| | - Parham Alaei
- Department of Radiation Oncology, University of Minnesota, Minneapolis, MN, USA
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Monte Carlo simulation of a cone-beam CT system for lightweight casts. RADIATION DETECTION TECHNOLOGY AND METHODS 2021. [DOI: 10.1007/s41605-021-00279-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Heidarloo N, Aghamiri SMR, Saghamanesh S, Azma Z, Alaei P. Generation of material-specific energy deposition kernels for kilovoltage x-ray dose calculations. Med Phys 2021; 48:5423-5439. [PMID: 34173989 DOI: 10.1002/mp.15061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2021] [Revised: 06/11/2021] [Accepted: 06/14/2021] [Indexed: 11/10/2022] Open
Abstract
PURPOSE Dose calculation of kilovoltage x rays used in Image-Guided Radiotherapy has been investigated in recent years using various methods. Among these methods are model-based ones that suffer from inaccuracies in high-density materials and at interfaces when used in the kilovoltage energy range. The main reason for this is the use of water energy deposition kernels and simplifications employed such as density scaling in heterogeneous media. The purpose of this study was to produce and characterize material-specific energy deposition kernels, which could be used for dose calculations in this energy range. These kernels will also have utility in dose calculations in superficial radiation therapy and orthovoltage beams utilized in small animal irradiators. METHODS Water energy deposition kernels with various resolutions; and high-resolution, material-specific energy deposition kernels were generated in the energy range of 10-150 kVp, using the EGSnrc Monte Carlo toolkit. The generated energy deposition kernels were further characterized by calculating the effective depth of penetration, the effective radial distance, and the effective lateral distance. A simple benchmarking of the kernels against Monte Caro calculations has also been performed. RESULTS There was good agreement with previously reported water kernels, as well as between kernels with different resolution. The evaluation of effective depth of penetration, and radial and laterals distances, defines the relationship between energy, material density, and the shape of the material-specific kernels. The shape of these kernels becomes more forwardly scattered as the energy and material density are increased. The comparison of the dose calculated using the kernels with Monte Carlo provides acceptable results. CONCLUSIONS Water and material-specific energy deposition kernels in the kilovoltage energy range have been generated, characterized, and compared to previous work. These kernels will have utility in dose calculations in this energy range once algorithms capable of employing them are fully developed.
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Affiliation(s)
- Nematollah Heidarloo
- Department of Medical Radiation Engineering, Shahid Beheshti University, Tehran, Iran
| | | | - Somayeh Saghamanesh
- Center for X-ray Analytics, Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland
| | - Zohreh Azma
- Department of Medical Radiation Engineering, Shahid Beheshti University, Tehran, Iran.,Erfan Radiation Oncology Center, Erfan-Niyayesh Hospital, Iran University of Medical Science, Tehran, Iran
| | - Parham Alaei
- Department of Radiation Oncology, University of Minnesota, Minneapolis, MN, USA
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Darvish-Molla S, Spurway A, Sattarivand M. Comprehensive characterization of ExacTrac stereoscopic image guidance system using Monte Carlo and Spektr simulations. Phys Med Biol 2020; 65:245029. [PMID: 32392546 DOI: 10.1088/1361-6560/ab91d8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The purpose of this work is to develop accurate computational methods to comprehensively characterize and model the clinical ExacTrac imaging system, which is used as an image guidance system for stereotactic treatment applications. The Spektr toolkit was utilized to simulate the spectral and imaging characterization of the system. Since Spektr only simulates the primary beam (ignoring scatter), a full model of ExacTrac was also developed in Monte Carlo (MC) to characterize the imaging system. To ensure proper performance of both simulation models, Spektr and MC data were compared to the measured spectral and half value layers (HVLs) values. To validate the simulation results, x-ray spectra of the ExacTrac system were measured for various tube potentials using a CdTe spectrometer with multiple added narrow collimators. The raw spectra were calibrated using a 57Co source and corrected for the escape peaks and detector efficiency. HVLs in mm of Al for various energies were measured using a calibrated RaySafe detector. Spektr and MC HVLs were calculated and compared to the measured values. The patient surface dose was calculated for different clinical imaging protocols from the measured air kerma and HVL values following the TG-61 methodology. The x-ray focal spot was measured by slanted edge technique using gafchromic films. ExacTrac imaging system beam profiles were simulated for various energies by MC simulation and the results were benchmarked by experimentally acquired beam profiles using gafchromic films. The effect of 6D IGRT treatment couch on beam hardening, dynamic range of the flat panel detector and scatter effect were determined using both Spektr simulation and experimental measurements. The measured and simulated spectra (of both MC and Spektr) for various kVps were compared and agreed within acceptable error. As another validation, the measured HVLs agreed with the Spektr and MC simulated HVLs on average within 1.0% for all kVps. The maximum and minimum patient surface doses were found to be 1.06 mGy for shoulder (high) and 0.051 mGy for cranial (low) imaging protocols, respectively. The MC simulated beam profiles were well matched with experimental results and replicated the penumbral slopes, the heel effect, and out-of-field regions. Dynamic range of detector (in terms of air kerma at detector surface) was found to be in the range of [6.1 × 10-6, 5.3 × 10-3] mGy. Accurate MC and Spektr models of the ExacTrac image guidance system were successfully developed and benchmarked via experimental validation. While patient surface dose for available imaging protocols were reported in this study, the established MC model may be used to obtain 3D imaging dose distribution for real patient geometries.
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Affiliation(s)
- Sahar Darvish-Molla
- Department of Medical Physics, Juravinski Cancer Centre at Hamilton Health Sciences, Hamilton, ON, Canada. Author to whom any correspondence should be addressed
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Ding GX, Alaei P, Curran B, Flynn R, Gossman M, Mackie TR, Miften M, Morin R, Xu XG, Zhu TC. Image guidance doses delivered during radiotherapy: Quantification, management, and reduction: Report of the AAPM Therapy Physics Committee Task Group 180. Med Phys 2018; 45:e84-e99. [PMID: 29468678 DOI: 10.1002/mp.12824] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 01/10/2018] [Accepted: 01/10/2018] [Indexed: 11/07/2022] Open
Abstract
BACKGROUND With radiotherapy having entered the era of image guidance, or image-guided radiation therapy (IGRT), imaging procedures are routinely performed for patient positioning and target localization. The imaging dose delivered may result in excessive dose to sensitive organs and potentially increase the chance of secondary cancers and, therefore, needs to be managed. AIMS This task group was charged with: a) providing an overview on imaging dose, including megavoltage electronic portal imaging (MV EPI), kilovoltage digital radiography (kV DR), Tomotherapy MV-CT, megavoltage cone-beam CT (MV-CBCT) and kilovoltage cone-beam CT (kV-CBCT), and b) providing general guidelines for commissioning dose calculation methods and managing imaging dose to patients. MATERIALS & METHODS We briefly review the dose to radiotherapy (RT) patients resulting from different image guidance procedures and list typical organ doses resulting from MV and kV image acquisition procedures. RESULTS We provide recommendations for managing the imaging dose, including different methods for its calculation, and techniques for reducing it. The recommended threshold beyond which imaging dose should be considered in the treatment planning process is 5% of the therapeutic target dose. DISCUSSION Although the imaging dose resulting from current kV acquisition procedures is generally below this threshold, the ALARA principle should always be applied in practice. Medical physicists should make radiation oncologists aware of the imaging doses delivered to patients under their care. CONCLUSION Balancing ALARA with the requirement for effective target localization requires that imaging dose be managed based on the consideration of weighing risks and benefits to the patient.
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Affiliation(s)
- George X Ding
- Department of Radiation Oncology, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA
| | - Parham Alaei
- University of Minnesota, Minneapolis, MN, 55455, USA
| | - Bruce Curran
- Virginia Commonwealth University, Richmond, VA, 23284, USA
| | - Ryan Flynn
- University of Iowa, Iowa City, IA, 52242, USA
| | | | | | | | | | - X George Xu
- Rensselaer Polytechnic Institute, Troy, NY, 12180, USA
| | - Timothy C Zhu
- University of Pennsylvania, Philadelphia, PA, 19104, USA
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Abuhaimed A, Martin CJ, Sankaralingam M. A Monte Carlo study of organ and effective doses of cone beam computed tomography (CBCT) scans in radiotherapy. JOURNAL OF RADIOLOGICAL PROTECTION : OFFICIAL JOURNAL OF THE SOCIETY FOR RADIOLOGICAL PROTECTION 2018; 38:61-80. [PMID: 28952463 DOI: 10.1088/1361-6498/aa8f61] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Cone-beam CT (CBCT) scans utilised for image guided radiation therapy (IGRT) procedures have become an essential part of radiotherapy. The aim of this study was to assess organ and effective doses resulting from new CBCT scan protocols (head, thorax, and pelvis) released with a software upgrade of the kV on-board-imager (OBI) system. Organ and effective doses for protocols of the new software (V2.5) and a previous version (V1.6) were assessed using Monte Carlo (MC) simulations for the International Commission on Radiological Protection (ICRP) adult male and female reference computational phantoms. The number of projections and the mAs values were increased and the size of the scan field was extended in the new protocols. Influence of these changes on organ and effective doses of the scans was investigated. The OBI system was modelled in EGSnrc/BEAMnrc, and organ doses were estimated using EGSnrc/DOSXYZnrc. The MC model was benchmarked against experimental measurements. Organ doses resulting from the V2.5 protocols were higher than those of V1.6 for organs that were partially or fully inside the scans fields, and increased by (3-13)%, (10-77)%, and (13-21)% for the head, thorax, and pelvis protocols for both phantoms, respectively. As a result, effective doses rose by 14%, 17%, and 16% for the male phantom, and 13%, 18%, and 17% for the female phantom for the three scan protocols, respectively. The scan field extension for the V2.5 protocols contributed significantly in the dose increases, especially for organs that were partially irradiated such as the thyroid in head and thorax scans and colon in the pelvic scan. The contribution of the mAs values and projection numbers was minimal in the dose increases, up to 2.5%. The field size extension plays a major role in improving the treatment output by including more markers in the field of view to match between CBCT and CT images and hence setting up the patient precisely. Therefore, a trade-off between the risk and benefits of CBCT scans should be considered, and the dose increases should be monitored. Several recommendations have been made for optimisation of the patient dose involved for IGRT procedures.
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Affiliation(s)
- Abdullah Abuhaimed
- The National Centre for Applied Physics, King Abdulaziz City for Science and Technology, Riyadh, Saudi Arabia
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Marchant TE, Joshi KD. Comprehensive Monte Carlo study of patient doses from cone-beam CT imaging in radiotherapy. JOURNAL OF RADIOLOGICAL PROTECTION : OFFICIAL JOURNAL OF THE SOCIETY FOR RADIOLOGICAL PROTECTION 2017; 37:13-30. [PMID: 27922831 DOI: 10.1088/1361-6498/37/1/13] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Accurate knowledge of ionizing radiation dose from cone-beam CT (CBCT) imaging in radiotherapy is important to allow concomitant risks to be estimated and for justification of imaging exposures. This study uses a Monte Carlo CBCT model to calculate imaging dose for a wide range of imaging protocols for male and female patients. The Elekta XVI CBCT system was modeled using GATE and simulated doses were validated against measurements in a water tank and thorax phantom. Imaging dose was simulated in the male and female ICRP voxel phantoms for a variety of anatomical sites and imager settings (different collimators, filters, full and partial rotation). The resulting dose distributions were used to calculate effective doses for each scan protocol. The Monte Carlo simulated doses agree with validation measurements within 5% and 10% for water tank and thorax phantom respectively. Effective dose for head CBCT scans was generally lower for scans centred on the pituitary than the larynx (0.03 mSv versus 0.06 mSv for male ICRP phantom). Pelvis CBCT scan effective dose was higher for the female than male phantom (5.11 mSv versus 2.80 mSv for M15 collimator scan), principally due to the higher dose received by gonads for the female scan. Medium field of view thorax scan effective doses ranged from 1.38-3.19 mSv depending on scan length and phantom sex. Effective dose for half rotation thorax scans with offset isocentre varied by almost a factor of three depending on laterality of the isocentre, patient sex and imaged field length. The CBCT imaging doses simulated here reveal large variations in dose depending on imaging isocentre location, patient sex and partial rotation angles. This information may be used to estimate risks from CBCT and to optimize CBCT imaging protocols.
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Affiliation(s)
- T E Marchant
- The University of Manchester, Manchester Academic Health Science Centre, The Christie NHS Foundation Trust, Manchester, M20 4BX, UK. Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester, M20 4BX, UK
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Vilches-Freixas G, Létang JM, Brousmiche S, Romero E, Vila Oliva M, Kellner D, Deutschmann H, Keuschnigg P, Steininger P, Rit S. Technical Note: Procedure for the calibration and validation of kilo-voltage cone-beam CT models. Med Phys 2016; 43:5199. [DOI: 10.1118/1.4961400] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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15
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Thing RS, Bernchou U, Mainegra-Hing E, Hansen O, Brink C. Hounsfield unit recovery in clinical cone beam CT images of the thorax acquired for image guided radiation therapy. Phys Med Biol 2016; 61:5781-802. [DOI: 10.1088/0031-9155/61/15/5781] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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16
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Menten MJ, Fast MF, Nill S, Oelfke U. Using dual-energy x-ray imaging to enhance automated lung tumor tracking during real-time adaptive radiotherapy. Med Phys 2015; 42:6987-98. [PMID: 26632054 DOI: 10.1118/1.4935431] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Revised: 10/20/2015] [Accepted: 10/28/2015] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Real-time, markerless localization of lung tumors with kV imaging is often inhibited by ribs obscuring the tumor and poor soft-tissue contrast. This study investigates the use of dual-energy imaging, which can generate radiographs with reduced bone visibility, to enhance automated lung tumor tracking for real-time adaptive radiotherapy. METHODS kV images of an anthropomorphic breathing chest phantom were experimentally acquired and radiographs of actual lung cancer patients were Monte-Carlo-simulated at three imaging settings: low-energy (70 kVp, 1.5 mAs), high-energy (140 kVp, 2.5 mAs, 1 mm additional tin filtration), and clinical (120 kVp, 0.25 mAs). Regular dual-energy images were calculated by weighted logarithmic subtraction of high- and low-energy images and filter-free dual-energy images were generated from clinical and low-energy radiographs. The weighting factor to calculate the dual-energy images was determined by means of a novel objective score. The usefulness of dual-energy imaging for real-time tracking with an automated template matching algorithm was investigated. RESULTS Regular dual-energy imaging was able to increase tracking accuracy in left-right images of the anthropomorphic phantom as well as in 7 out of 24 investigated patient cases. Tracking accuracy remained comparable in three cases and decreased in five cases. Filter-free dual-energy imaging was only able to increase accuracy in 2 out of 24 cases. In four cases no change in accuracy was observed and tracking accuracy worsened in nine cases. In 9 out of 24 cases, it was not possible to define a tracking template due to poor soft-tissue contrast regardless of input images. The mean localization errors using clinical, regular dual-energy, and filter-free dual-energy radiographs were 3.85, 3.32, and 5.24 mm, respectively. Tracking success was dependent on tumor position, tumor size, imaging beam angle, and patient size. CONCLUSIONS This study has highlighted the influence of patient anatomy on the success rate of real-time markerless tumor tracking using dual-energy imaging. Additionally, the importance of the spectral separation of the imaging beams used to generate the dual-energy images has been shown.
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Affiliation(s)
- Martin J Menten
- Joint Department of Physics at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London SM2 5NG, United Kingdom
| | - Martin F Fast
- Joint Department of Physics at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London SM2 5NG, United Kingdom
| | - Simeon Nill
- Joint Department of Physics at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London SM2 5NG, United Kingdom
| | - Uwe Oelfke
- Joint Department of Physics at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London SM2 5NG, United Kingdom
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Alaei P, Spezi E. Imaging dose from cone beam computed tomography in radiation therapy. Phys Med 2015; 31:647-58. [PMID: 26148865 DOI: 10.1016/j.ejmp.2015.06.003] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Revised: 05/29/2015] [Accepted: 06/05/2015] [Indexed: 12/26/2022] Open
Abstract
Imaging dose in radiation therapy has traditionally been ignored due to its low magnitude and frequency in comparison to therapeutic dose used to treat patients. The advent of modern, volumetric, imaging modalities, often as an integral part of linear accelerators, has facilitated the implementation of image-guided radiation therapy (IGRT), which is often accomplished by daily imaging of patients. Daily imaging results in additional dose delivered to patient that warrants new attention be given to imaging dose. This review summarizes the imaging dose delivered to patients as the result of cone beam computed tomography (CBCT) imaging performed in radiation therapy using current methods and equipment. This review also summarizes methods to calculate the imaging dose, including the use of Monte Carlo (MC) and treatment planning systems (TPS). Peripheral dose from CBCT imaging, dose reduction methods, the use of effective dose in describing imaging dose, and the measurement of CT dose index (CTDI) in CBCT systems are also reviewed.
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Affiliation(s)
| | - Emiliano Spezi
- School of Engineering, Cardiff University, Cardiff, Wales, UK; Velindre Cancer Centre, Cardiff, Wales, UK
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18
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Azimi R, Alaei P, Spezi E, Hui SK. Characterization of an orthovoltage biological irradiator used for radiobiological research. JOURNAL OF RADIATION RESEARCH 2015; 56:485-492. [PMID: 25694476 PMCID: PMC4426923 DOI: 10.1093/jrr/rru129] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Revised: 12/16/2014] [Accepted: 12/27/2014] [Indexed: 06/01/2023]
Abstract
Orthovoltage irradiators are routinely used to irradiate specimens and small animals in biological research. There are several reports on the characteristics of these units for small field irradiations. However, there is limited knowledge about use of these units for large fields, which are essential for emerging large-field irregular shape irradiations, namely total marrow irradiation used as a conditioning regimen for hematological malignancies. This work describes characterization of a self-contained Orthovoltage biological irradiator for large fields using measurements and Monte Carlo simulations that could be used to compute the dose for in vivo or in vitro studies for large-field irradiation using this or a similar unit. Percentage depth dose, profiles, scatter factors, and half-value layers were measured and analyzed. A Monte Carlo model of the unit was created and used to generate depth dose and profiles, as well as scatter factors. An ion chamber array was also used for profile measurements of flatness and symmetry. The output was determined according to AAPM Task Group 61 guidelines. The depth dose measurements compare well with published data for similar beams. The Monte Carlo-generated depth dose and profiles match our measured doses to within 2%. Scatter factor measurements indicate gradual variation of these factors with field size. Dose rate measured by placing the ion chamber atop the unit's steel plate or solid water indicate enhanced readings of 5 to 28% compared with those measured in air. The stability of output over a 5-year period is within 2% of the 5-year average.
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Affiliation(s)
- Rezvan Azimi
- Department of Radiation Oncology, University of Minnesota, 420 Delaware Street, SE MMC 494, Minneapolis, MN 55455, USA
| | - Parham Alaei
- Department of Radiation Oncology, University of Minnesota, 420 Delaware Street, SE MMC 494, Minneapolis, MN 55455, USA
| | - Emiliano Spezi
- Department of Medical Physics, Velindre Cancer Centre, Velindre Road, CF14 2TL, Cardiff, UK
| | - Susanta K Hui
- Department of Radiation Oncology, University of Minnesota, 420 Delaware Street, SE MMC 494, Minneapolis, MN 55455, USA
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Brochu FM, Burnet NG, Jena R, Plaistow R, Parker MA, Thomas SJ. Geant4 simulation of the Elekta XVI kV CBCT unit for accurate description of potential late toxicity effects of image-guided radiotherapy. Phys Med Biol 2014; 59:7601-8. [PMID: 25415354 DOI: 10.1088/0031-9155/59/24/7601] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
This paper describes the modelisation of the Elekta XVI Cone Beam Computed Tomography (CBCT) machine components with Geant4 and its validation against calibration data taken for two commonly used machine setups. Preliminary dose maps of simulated CBCTs coming from this modelisation work are presented. This study is the first step of a research project, GHOST, aiming to improve the understanding of late toxicity risk in external beam radiotherapy patients by simulating dose depositions integrated from different sources (imaging, treatment beam) over the entire treatment plan. The second cancer risk will then be derived from different models relating irradiation dose and second cancer risk.
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Affiliation(s)
- F M Brochu
- University of Cambridge, Department of Oncology, Cambridge Biomedical Campus, Addenbrooke's Hospital, Cambridge, CB2 0QQ, UK. University of Cambridge, Department of Physics, Cavendish Laboratory, J J Thomson Avenue, Cambridge, UK
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Hioki K, Araki F, Ohno T, Nakaguchi Y, Tomiyama Y. Absorbed dose measurements for kV-cone beam computed tomography in image-guided radiation therapy. Phys Med Biol 2014; 59:7297-313. [DOI: 10.1088/0031-9155/59/23/7297] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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21
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Scandurra D, Lawford CE. A dosimetry technique for measuring kilovoltage cone-beam CT dose on a linear accelerator using radiotherapy equipment. J Appl Clin Med Phys 2014; 15:4658. [PMID: 25207398 PMCID: PMC5875512 DOI: 10.1120/jacmp.v15i4.4658] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Revised: 04/02/2014] [Accepted: 03/26/2014] [Indexed: 11/23/2022] Open
Abstract
This work develops a technique for kilovoltage cone‐beam CT (CBCT) dosimetry that incorporates both point dose and integral dose in the form of dose length product, and uses readily available radiotherapy equipment. The dose from imaging protocols for a range of imaging parameters and treatment sites was evaluated. Conventional CT dosimetry using 100 mm long pencil chambers has been shown to be inadequate for the large fields in CBCT and has been replaced in this work by a combination of point dose and integral dose. Absolute dose measurements were made with a small volume ion chamber at the central slice of a radiotherapy phantom. Beam profiles were measured using a linear diode array large enough to capture the entire imaging field. These profiles were normalized to absolute dose to form dose line integrals, which were then weighted with radial depth to form the DLPCBCT. This metric is analogous to the standard dose length product (DLP), but derived differently to suit the unique properties of CBCT. Imaging protocols for head and neck, chest, and prostate sites delivered absolute doses of 0.9, 2.2, and 2.9 cGy to the center of the phantom, and DLPCBCT of 28.2, 665.1, and 565.3 mGy.cm, respectively. Results are displayed as dose per 100 mAs and as a function of key imaging parameters such as kVp, mAs, and collimator selection in a summary table. DLPCBCT was found to correlate closely with the dimension of the imaging region and provided a good indication of integral dose. It is important to assess integral dose when determining radiation doses to patients using CBCT. By incorporating measured beam profiles and DLP, this technique provides a CBCT dosimetry in radiotherapy phantoms and allows the prediction of imaging dose for new CBCT protocols. PACS number: 87.57.uq
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Affiliation(s)
- Daniel Scandurra
- Department of Radiation Oncology Olivia Newton-John Cancer and Wellness Centre.
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Nelson AP, Ding GX. An alternative approach to account for patient organ doses from imaging guidance procedures. Radiother Oncol 2014; 112:112-8. [DOI: 10.1016/j.radonc.2014.05.019] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Revised: 05/05/2014] [Accepted: 05/24/2014] [Indexed: 11/16/2022]
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Giaddui T, Cui Y, Galvin J, Yu Y, Xiao Y. Comparative dose evaluations between XVI and OBI cone beam CT systems using Gafchromic XRQA2 film and nanoDot optical stimulated luminescence dosimeters. Med Phys 2014; 40:062102. [PMID: 23718600 DOI: 10.1118/1.4803466] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To investigate the effect of energy (kVp) and filters (no filter, half Bowtie, and full Bowtie) on the dose response curves of the Gafchromic XRQA2 film and nanoDot optical stimulated luminescence dosimeters (OSLDs) in CBCT dose fields. To measure surface and internal doses received during x-ray volume imager (XVI) (Version R4.5) and on board imager (OBI) (Version 1.5) CBCT imaging protocols using these two types of dosimeters. METHODS Gafchromic XRQA2 film and nanoDot OSLD dose response curves were generated at different kV imaging settings used by XVI (software version R4.5) and OBI (software version 1.5) CBCT systems. The settings for the XVI system were: 100 kVp∕F0 (no filter), 120 kVp∕F0, and 120 kVp∕F1 (Bowtie filter), and for the OBI system were: 100 kVp∕full fan, 125 kVp∕full fan, and 125 kVp∕half fan. XRQA2 film was calibrated in air to air kerma levels between 0 and 11 cGy and scanned using reflection scanning mode with the Epson Expression 10000 XL flat-bed document scanner. NanoDot OSLDs were calibrated on phantom to surface dose levels between 0 and 14 cGy and read using the inLight(TM) MicroStar reader. Both dosimeters were used to measure in field surface and internal doses in a male Alderson Rando Phantom. RESULTS Dose response curves of XRQA2 film and nanoDot OSLDs at different XVI and OBI CBCT settings were reported. For XVI system, the surface dose ranged between 0.02 cGy in head region during fast head and neck scan and 4.99 cGy in the chest region during symmetry scan. On the other hand, the internal dose ranged between 0.02 cGy in the head region during fast head and neck scan and 3.17 cGy in the chest region during chest M20 scan. The average (internal and external) dose ranged between 0.05 cGy in the head region during fast head and neck scan and 2.41 cGy in the chest region during chest M20 scan. For OBI system, the surface dose ranged between 0.19 cGy in head region during head scan and 4.55 cGy in the pelvis region during spot light scan. However, the internal dose ranged between 0.47 cGy in the head region during head scan and 5.55 cGy in the pelvis region during spot light scan. The average (internal and external) dose ranged between 0.45 cGy in the head region during head scan and 3.59 cGy in the pelvis region during spot light scan. Both Gafchromic XRQA2 film and nanoDot OSLDs gave close estimation of dose (within uncertainties) in many cases. Though, discrepancies of up to 20%-30% were observed in some cases. CONCLUSIONS Dose response curves of Gafchromic XRQA2 film and nanoDot OSLDs indicated that the dose responses of these two dosimeters were different even at the same photon energy when different filters were used. Uncertainty levels of both dosimetry systems were below 6% at doses above 1 cGy. Both dosimetry systems gave almost similar estimation of doses (within uncertainties) in many cases, with exceptions of some cases when the discrepancy was around 20%-30%. New versions of the CBCT systems (investigated in this study) resulted in lower imaging doses compared with doses reported on earlier versions in previous studies.
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Affiliation(s)
- Tawfik Giaddui
- Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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24
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Thing RS, Bernchou U, Mainegra-Hing E, Brink C. Patient-specific scatter correction in clinical cone beam computed tomography imaging made possible by the combination of Monte Carlo simulations and a ray tracing algorithm. Acta Oncol 2013; 52:1477-83. [PMID: 23879648 DOI: 10.3109/0284186x.2013.813641] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE Cone beam computed tomography (CBCT) image quality is limited by scattered photons. Monte Carlo (MC) simulations provide the ability of predicting the patient-specific scatter contamination in clinical CBCT imaging. Lengthy simulations prevent MC-based scatter correction from being fully implemented in a clinical setting. This study investigates the combination of using fast MC simulations to predict scatter distributions with a ray tracing algorithm to allow calibration between simulated and clinical CBCT images. MATERIAL AND METHODS An EGSnrc-based user code (egs_cbct), was used to perform MC simulations of an Elekta XVI CBCT imaging system. A 60 keV x-ray source was used, and air kerma scored at the detector plane. Several variance reduction techniques (VRTs) were used to increase the scatter calculation efficiency. Three patient phantoms based on CT scans were simulated, namely a brain, a thorax and a pelvis scan. A ray tracing algorithm was used to calculate the detector signal due to primary photons. A total of 288 projections were simulated, one for each thread on the computer cluster used for the investigation. RESULTS Scatter distributions for the brain, thorax and pelvis scan were simulated within 2% statistical uncertainty in two hours per scan. Within the same time, the ray tracing algorithm provided the primary signal for each of the projections. Thus, all the data needed for MC-based scatter correction in clinical CBCT imaging was obtained within two hours per patient, using a full simulation of the clinical CBCT geometry. CONCLUSIONS This study shows that use of MC-based scatter corrections in CBCT imaging has a great potential to improve CBCT image quality. By use of powerful VRTs to predict scatter distributions and a ray tracing algorithm to calculate the primary signal, it is possible to obtain the necessary data for patient specific MC scatter correction within two hours per patient.
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Affiliation(s)
- Rune S Thing
- Institute of Clinical Research, University of Southern Denmark , Odense , Denmark
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25
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Ding GX, Malcolm AW. An optically stimulated luminescence dosimeter for measuring patient exposure from imaging guidance procedures. Phys Med Biol 2013; 58:5885-97. [DOI: 10.1088/0031-9155/58/17/5885] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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26
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Ding GX, Munro P. Radiation exposure to patients from image guidance procedures and techniques to reduce the imaging dose. Radiother Oncol 2013; 108:91-8. [PMID: 23830468 DOI: 10.1016/j.radonc.2013.05.034] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Revised: 04/08/2013] [Accepted: 05/09/2013] [Indexed: 11/25/2022]
Abstract
PURPOSE To compare imaging doses from MV images, kV radiographs, and kV-CBCT and describe methods to reduce the dose to patient's organs using existing on-board imaging devices. METHOD AND MATERIALS Monte Carlo techniques were used to simulate kV X-ray sources. The kV image doses to a variety of patient anatomies were calculated by using the simulated realistic sources to deposit dose in patient CT images. For MV imaging, the doses for the same patients were calculated using a commercial treatment planning system. RESULTS Portal imaging results in the largest dose to anatomic structures, followed by Varian OBI CBCT, Varian TrueBeam CBCT and then kV radiographs. The imaging doses for the 50% volume from the DVHs, D50, to the eyes for representative head images are 4.3-4.8cGy; 0.05-0.06cGy; 0.04-0.05cGy; and, 0.12cGy; D50 to the bladder for representative pelvis images are 3.3cGy; 1.6cGy; 1.0cGy; and, 0.07cGy; while D50 to the heart for representative thorax images are 3.5cGy; 0.42cGy; 0.2cGy; and, 0.07cGy; when using portal imaging, OBI kV-CBCT scans, TrueBeam kV-CBCT scans and kV radiographs, respectively. The orientation of the kV beam can affect organ dose. For example, D50 to the eyes can be reduced from 0.12cGy using AP and right lateral radiographs to 0.008-0.017cGy when using PA and right lateral radiographs. In addition, organ exposures can be further reduced to 15-70% of their original values with the use of a full-fan, bow-tie filter for kV radiographs. In contrast, organ doses increase by a factor of ∼2-4 if bow-tie filters are not used during kV-CBCT acquisitions. CONCLUSION Current on-board kV imaging devices result in much lower imaging doses compared to MV imagers even taking into account of higher bone dose from kV X-rays. And a variety of approaches are available to significantly reduce the image doses.
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Affiliation(s)
- George X Ding
- Department of Radiation Oncology, Vanderbilt University School of Medicine, Nashville 37232-5671, USA.
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Sykes JR, Lindsay R, Iball G, Thwaites DI. Dosimetry of CBCT: methods, doses and clinical consequences. ACTA ACUST UNITED AC 2013. [DOI: 10.1088/1742-6596/444/1/012017] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Investigation of the dose distribution for a cone beam CT system dedicated to breast imaging. Phys Med 2013; 29:379-87. [DOI: 10.1016/j.ejmp.2012.06.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2011] [Revised: 04/21/2012] [Accepted: 06/09/2012] [Indexed: 11/17/2022] Open
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Alaei P, Spezi E. Commissioning kilovoltage cone-beam CT beams in a radiation therapy treatment planning system. J Appl Clin Med Phys 2012; 13:3971. [PMID: 23149789 PMCID: PMC5718524 DOI: 10.1120/jacmp.v13i6.3971] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Revised: 05/15/2012] [Accepted: 06/18/2012] [Indexed: 11/23/2022] Open
Abstract
The feasibility of accounting of the dose from kilovoltage cone‐beam CT in treatment planning has been discussed previously for a single cone‐beam CT (CBCT) beam from one manufacturer. Modeling the beams and computing the dose from the full set of beams produced by a kilovoltage cone‐beam CT system requires extensive beam data collection and verification, and is the purpose of this work. The beams generated by Elekta X‐ray volume imaging (XVI) kilovoltage CBCT (kV CBCT) system for various cassettes and filters have been modeled in the Philips Pinnacle treatment planning system (TPS) and used to compute dose to stack and anthropomorphic phantoms. The results were then compared to measurements made using thermoluminescent dosimeters (TLDs) and Monte Carlo (MC) simulations. The agreement between modeled and measured depth‐dose and cross profiles is within 2% at depths beyond 1 cm for depth‐dose curves, and for regions within the beam (excluding penumbra) for cross profiles. The agreements between TPS‐calculated doses, TLD measurements, and Monte Carlo simulations are generally within 5% in the stack phantom and 10% in the anthropomorphic phantom, with larger variations observed for some of the measurement/calculation points. Dose computation using modeled beams is reasonably accurate, except for regions that include bony anatomy. Inclusion of this dose in treatment plans can lead to more accurate dose prediction, especially when the doses to organs at risk are of importance. PACS numbers: 87.55.D, 87.55.K, 87.56.bd
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Affiliation(s)
- Parham Alaei
- Department of Radiation Oncology, University of Minnesota, Minneapolis, MN 55455, USA.
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Stock M, Palm A, Altendorfer A, Steiner E, Georg D. IGRT induced dose burden for a variety of imaging protocols at two different anatomical sites. Radiother Oncol 2012; 102:355-63. [DOI: 10.1016/j.radonc.2011.10.005] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Revised: 09/23/2011] [Accepted: 10/16/2011] [Indexed: 10/15/2022]
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Spezi E, Downes P, Jarvis R, Radu E, Staffurth J. Patient-specific three-dimensional concomitant dose from cone beam computed tomography exposure in image-guided radiotherapy. Int J Radiat Oncol Biol Phys 2011; 83:419-26. [PMID: 22027261 DOI: 10.1016/j.ijrobp.2011.06.1972] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2010] [Revised: 05/24/2011] [Accepted: 06/10/2011] [Indexed: 12/31/2022]
Abstract
PURPOSE The purpose of the present study was to quantify the concomitant dose received by patients undergoing cone beam computed tomography (CBCT) scanning in different clinical scenarios as a part of image-guided radiotherapy (IGRT) procedures. METHODS AND MATERIALS We calculated the three-dimensional concomitant dose received as a result of CBCT scans in 6 patients representing different clinical scenarios: two pelvis, two head and neck, and two chest. We assessed the effect that a daily on-line IGRT strategy would have on the patient dose distribution, assuming 40 CBCT scans throughout the treatment course. The additional dose to the planning target volume margin region was also estimated. RESULTS In the pelvis, a single CBCT scan delivered a mean dose to the femoral heads of 2-6 cGy and the rectum of 1-2 cGy. An additional dose to the planning target volume was within 1-3 cGy. In the chest, the mean dose to the planning target volume varied from 2.5 to 5 cGy. The lung and spinal cord planning organ at risk volume received ≤4 cGy and ≤5 cGy, respectively. In the head and neck, a single CBCT scan delivered a mean dose of 0.3 cGy, with bony structures receiving 0.5-0.8 cGy. The femoral heads received an additional dose of 1.5-2.5 Gy. A reduction of 20-30% in the mean dose to the organs at risk was achieved using bowtie filtration. In the head and neck, the dose to the eyes and brainstem was eliminated by decreasing the craniocaudal field size. CONCLUSIONS The additional dose from on-line IGRT procedures can be clinically relevant. The organ dose can be significantly reduced with the use of appropriate patient-specific settings. The concomitant dose from CBCT should be accounted for and the acquisition settings optimized for optimal IGRT strategies on a patient basis.
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Affiliation(s)
- Emiliano Spezi
- Department of Medical Physics, Velindre Cancer Centre, Cardiff, United Kingdom.
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Spezi E, Volken W, Frei D, Fix MK. A virtual source model for Kilo-voltage cone beam CT: Source characteristics and model validation. Med Phys 2011; 38:5254-63. [DOI: 10.1118/1.3626574] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Zhang G, Pauwels R, Marshall N, Shaheen E, Nuyts J, Jacobs R, Bosmans H. Development and validation of a hybrid simulation technique for cone beam CT: application to an oral imaging system. Phys Med Biol 2011; 56:5823-43. [PMID: 21846936 DOI: 10.1088/0031-9155/56/18/004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
This paper proposes a hybrid technique to simulate the complete chain of an oral cone beam computed tomography (CBCT) system for the study of both radiation dose and image quality. The model was developed around a 3D Accuitomo 170 unit (J Morita, Japan) with a tube potential range of 60-90 kV. The Monte Carlo technique was adopted to simulate the x-ray generation, filtration and collimation. Exact dimensions of the bow-tie filter were estimated iteratively using experimentally acquired flood images. Non-flat radiation fields for different exposure settings were mediated via 'phase spaces'. Primary projection images were obtained by ray tracing at discrete energies and were fused according to the two-dimensional energy modulation templates derived from the phase space. Coarse Monte Carlo simulations were performed for scatter projections and the resulting noisy images were smoothed by Richardson-Lucy fitting. Resolution and noise characteristics of the flat panel detector were included using the measured modulation transfer function (MTF) and the noise power spectrum (NPS), respectively. The Monte Carlo dose calculation was calibrated in terms of kerma free-in-air about the isocenter, using an ionization chamber, and was subsequently validated by comparison against the measured air kerma in water at various positions of a cylindrical water phantom. The resulting dose discrepancies were found <10% for most cases. Intensity profiles of the experimentally acquired and simulated projection images of the water phantom showed comparable fractional increase over the common area as changing from a small to a large field of view, suggesting that the scatter was accurately accounted. Image validation was conducted using two small phantoms and the built-in quality assurance protocol of the system. The reconstructed simulated images showed high resemblance on contrast resolution, noise appearance and artifact pattern in comparison to experimentally acquired images, with <5% difference for voxel values of the aluminum and air insert regions and <3% difference for voxel uniformity across the homogeneous PMMA region. The detector simulation by use of the MTF and NPS data exhibited a big influence on noise and the sharpness of the resulting images. The hybrid simulation technique is flexible and has wide applicability to CBCT systems.
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Affiliation(s)
- G Zhang
- Department of Radiology, University Hospitals Leuven, Herestraat 49, Leuven 3000, Belgium.
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Validation of a Monte Carlo simulation for dose assessment in dental cone beam CT examinations. Phys Med 2011; 28:200-9. [PMID: 21807542 DOI: 10.1016/j.ejmp.2011.06.047] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2011] [Revised: 06/02/2011] [Accepted: 06/28/2011] [Indexed: 11/22/2022] Open
Abstract
A Monte Carlo (MC) simulation for calculating absorbed dose has been developed and applied for dental applications with an i-CAT cone beam CT (CBCT) system. To validate the method a comparison was made between calculated and measured dose values for two different clinical protocols. Measurements with a pencil CT chamber were performed free-in-air and in a CT dose head phantom; measurements were also performed with a transmission ionization chamber. In addition for each protocol a total number of 58 thermoluminescence dosemeters (TLD) were packed in groups and placed at 16 representative anatomical locations of an anthropomorphic phantom (Remab system) to assess absorbed doses. To simulate X-ray exposure, a software application based on the EGS4 package was applied. Dose quantities were calculated for different voxelized models representing the CT ionization and transmission chambers, the TLDs, and the phantoms as well. The dose quantities evaluated in the comparison were the accumulated dose averaged along the rotation axis (D(i)), the volume average dose,D(vol) for the dosimetric phantom, the dose area product (DAP) and the absorbed dose for the TLDs. Absolute differences between measured and simulated outcomes were ≤ 2.1% for free-in-air doses; ≤ 6.2% in the 5 cavities of the CT dose head phantom; ≤ 13% for TLDs inside the primary beam. Such differences were considered acceptable in all cases and confirmed the validity of the MC program for different geometries. In conclusion, the devised MC simulation program can be a robust tool to optimize protocols and estimate patient doses for CBCT units in dental, oral and maxillofacial radiology.
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Pawlowski JM, Ding GX. A new approach to account for the medium-dependent effect in model-based dose calculations for kilovoltage x-rays. Phys Med Biol 2011; 56:3919-34. [DOI: 10.1088/0031-9155/56/13/011] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Kouznetsov A, Tambasco M. A hybrid approach for rapid, accurate, and direct kilovoltage radiation dose calculations in CT voxel space. Med Phys 2011; 38:1378-88. [DOI: 10.1118/1.3555038] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Ding GX, Coffey CW. Beam characteristics and radiation output of a kilovoltage cone-beam CT. Phys Med Biol 2010; 55:5231-48. [DOI: 10.1088/0031-9155/55/17/022] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Downes P, Jarvis R, Radu E, Kawrakow I, Spezi E. Monte Carlo simulation and patient dosimetry for a kilovoltage cone-beam CT unit. Med Phys 2009; 36:4156-67. [PMID: 19810489 DOI: 10.1118/1.3196182] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The purpose of this work is to characterize the x-ray volume imager (XVI), the cone-beam computed tomography (CBCT) unit mounted on the Elekta Synergy linac, with F1 bowtie filter and to calculate the three-dimensional dose delivered to patients using volumetric acquisition. METHODS The XVI is modeled in detail using a new Monte Carlo (MC) code, BEAMPP, under development at the National Research Council Canada. In this investigation, a new component module is developed to accurately model the unit's bowtie filter used in conjunction with the available beam collimators at the clinical energy of 120 kV. The modeling is compared against percentage depth dose (PDD) and profile measurements. Kilovoltage radiation beams' phase space files are also analyzed. The authors also describe a method for the absolute dose calibration of the MC model of the CBCT unit when used in a clinical volumetric acquisition mode. Finally, they calculate three-dimensional patient dose from CBCT image acquisition in three clinical cases of interest: Pelvis, lung, and head and neck. RESULTS The agreement between measurement and MC is shown to be very good: Within +/- 2% for the PDD and within +/- 3.5% inside the radiation field for all the collimators with the F1 bowtie filter. A full account of the absolute calibration method is given and dose calculation is validated against ion chamber measurements in different locations of a plastic phantom. Calculations and experiments agree within +/- 2% or better in both at the center and the periphery of the phantom, with worst agreement of 4.5% at the surface of the phantom and for one specific combination of collimator and filter. Patient dose from CBCT scan reveals that dose to tissue is between 2 and 2.5 cGy for a pelvis or a lung full acquisition. For H&N dose to tissue is 5 cGy, with the unit presets used in this work. Dose to bony structures can be two to three times higher than dose to tissue. CONCLUSIONS The XVI CBCT unit has been fully modeled including the F1 bowtie filter. Absolute dose distribution from the unit has been successfully validated. Full MC patient dose calculation has shown that the three-dimensional dose distribution from CBCT is complex. Patient dose from CBCT exposure cannot be completely accounted for by using a numerical factor as an estimate of the dose at the center of the body. Furthermore, additional dose to bone should be taken into account when adopting any IGRT strategy and weighed vs the unquestionable benefits of the technique in order to optimize treatment. Full three-dimensional dose calculation is recommended if patient dose from CBCT is to be integrated in any adaptive planning strategy.
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Affiliation(s)
- P Downes
- Department of Medical Physics, Velindre Cancer Centre, Velindre Road, Cardiff CF14 2TL, United Kingdom
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Chow JCL. Cone-beam CT dosimetry for the positional variation in isocenter: A Monte Carlo study. Med Phys 2009; 36:3512-20. [DOI: 10.1118/1.3166934] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Wulff J, Ubrich F, Zink K. Comment on “Monte Carlo simulation of an x-ray volume imaging cone beam CT unit” [Med. Phys. 36, 127-136 (2009)]. Med Phys 2009; 36:1039; author reply 1040. [DOI: 10.1118/1.3078699] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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