1
|
Kunert P, Schlattl H, Trinkl S, Honorio da Silva E, Reichert D, Giussani A. 3D printing of realistic body phantoms: Comparison of measured and simulated organ doses on the example of a CT scan on a pregnant woman. Med Phys 2024. [PMID: 39298691 DOI: 10.1002/mp.17420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 08/22/2024] [Accepted: 08/24/2024] [Indexed: 09/22/2024] Open
Abstract
BACKGROUND Medical examinations or treatment of pregnant women using ionizing radiation are sometimes unavoidable. In such cases, the risk of harm to the embryo and fetus after exposure to ionizing radiation must be carefully estimated. However, no commercially available anthropomorphic body phantoms of pregnant women are available for dose measurements. A promising possibility for the production of body phantoms for patient groups that are not adequately represented by the phantoms of reference persons is 3D printing. However, this approach is still in the evaluation phase. PURPOSE To print the abdomen of a woman in the late stage of pregnancy and compare the dose distribution measured using thermoluminescence dosimeters (TLDs) in the printed phantom for two different computed tomography (CT) protocols with the corresponding results of Monte Carlo simulations on voxel models of the pregnant woman. MATERIALS AND METHODS The physical phantom was produced through multi-material extrusion printing using different print materials identified in previous studies to simulate homogeneous soft tissues and the mean compositions of maternal and fetal bones. The 3D printed abdomen was combined with a conventionally produced anthropomorphic female phantom to obtain a whole-body phantom of a pregnant woman. Dose values resulting from two different CT scans acquired at tube voltages of 80 and 120 kV were measured using TLDs positioned in the physical phantom and cross-validated with the results of Monte Carlo simulations performed for two different voxel models. The first was a voxelized model of the produced phantom itself and the second a realistic digital model of a pregnant woman. Representative CT values of the materials used in the printed phantom were determined from the acquired CT images. RESULTS The CT values of maternal and fetal tissue structures in the phantom are comparable to CT values of real human tissues. The difference between most organ doses measured in the 3D printed phantom and simulated in the voxel models was below 20% and equivalent within the measurement uncertainties. Only the dose to the fetal head was up to 50% higher and not equivalent for the realistic model and the 80 kV-protocol. As expected, the agreement was better for the voxelized than for the realistic model. For both models a slight energy dependence was observed, with larger deviations for the 80-kV protocol especially for organs located in the pelvic region. CONCLUSION Individualized physical body phantoms, such as that of a pregnant woman, can be produced using 3D printing. The good agreement between measured and simulated doses to the fetus cross-validates both dosimetric methods. Therefore, this study demonstrates the suitability of 3D printing phantoms for patients not adequately represented by commercially available body phantoms of reference persons.
Collapse
Affiliation(s)
- Patrizia Kunert
- Department of Medical and Occupational Radiation Protection, Federal Office for Radiation Protection, Oberschleißheim, Germany
| | - Helmut Schlattl
- Department of Medical and Occupational Radiation Protection, Federal Office for Radiation Protection, Oberschleißheim, Germany
| | - Sebastian Trinkl
- Department of Medical and Occupational Radiation Protection, Federal Office for Radiation Protection, Oberschleißheim, Germany
| | - Edilaine Honorio da Silva
- Department of Medical and Occupational Radiation Protection, Federal Office for Radiation Protection, Oberschleißheim, Germany
| | - Detlef Reichert
- Department of Physics, Martin-Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Augusto Giussani
- Department of Medical and Occupational Radiation Protection, Federal Office for Radiation Protection, Oberschleißheim, Germany
| |
Collapse
|
2
|
Paydar R, Tahmasebzadeh A, Maziyar A, Reiazi R, Kermanshahi M, Anijdan SM. Pediatric effective dose assessment for routine computed tomography examinations in Tehran, Iran. JOURNAL OF MEDICAL SIGNALS & SENSORS 2022; 12:227-232. [PMID: 36120406 PMCID: PMC9480506 DOI: 10.4103/jmss.jmss_115_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2021] [Revised: 03/17/2022] [Accepted: 04/19/2022] [Indexed: 11/30/2022]
Abstract
Background: The purpose of this study is to evaluate the effective dose (ED) for computed tomography (CT) examination in different age groups and medical exposure in pediatric imaging centers in Tehran, Iran. Methods: Imaging data were collected from 532 pediatric patients from four age groups subjected to three prevalent procedures. National Cancer Institute CT (NCICT) software was used to calculate the ED value. Results: The mean ED values were 1.60, 4.16, and 10.56 mSv for patients' procedures of head, chest, and abdomen–pelvis, respectively. This study showed a significant difference of ED value among five pediatric medical imaging centers (P < 0.05). In head, chest, and abdomen–pelvis exams, a reduction in ED was evident with decreasing patients' age. Conclusion: As there were significant differences among ED values in five pediatric medical imaging centers, optimizing this value is necessary to decrease this variation. For head CT in infants and also abdomen–pelvis, further reduction in radiation exposure is required.
Collapse
|
3
|
Thierry-Chef I, Ferro G, Le Cornet L, Dabin J, Istad TS, Jahnen A, Lee C, Maccia C, Malchair F, Olerud HM, Harbron RW, Figuerola J, Hermen J, Moissonnier M, Bernier MO, Bosch de Basea MB, Byrnes G, Cardis E, Hauptmann M, Journy N, Kesminiene A, Meulepas JM, Pokora R, Simon SL. Dose Estimation for the European Epidemiological Study on Pediatric Computed Tomography (EPI-CT). Radiat Res 2021; 196:74-99. [PMID: 33914893 DOI: 10.1667/rade-20-00231.1] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Accepted: 03/26/2021] [Indexed: 11/03/2022]
Abstract
Within the European Epidemiological Study to Quantify Risks for Paediatric Computerized Tomography (EPI-CT study), a cohort was assembled comprising nearly one million children, adolescents and young adults who received over 1.4 million computed tomography (CT) examinations before 22 years of age in nine European countries from the late 1970s to 2014. Here we describe the methods used for, and the results of, organ dose estimations from CT scanning for the EPI-CT cohort members. Data on CT machine settings were obtained from national surveys, questionnaire data, and the Digital Imaging and Communications in Medicine (DICOM) headers of 437,249 individual CT scans. Exposure characteristics were reconstructed for patients within specific age groups who received scans of the same body region, based on categories of machines with common technology used over the time period in each of the 276 participating hospitals. A carefully designed method for assessing uncertainty combined with the National Cancer Institute Dosimetry System for CT (NCICT, a CT organ dose calculator), was employed to estimate absorbed dose to individual organs for each CT scan received. The two-dimensional Monte Carlo sampling method, which maintains a separation of shared and unshared error, allowed us to characterize uncertainty both on individual doses as well as for the entire cohort dose distribution. Provided here are summaries of estimated doses from CT imaging per scan and per examination, as well as the overall distribution of estimated doses in the cohort. Doses are provided for five selected tissues (active bone marrow, brain, eye lens, thyroid and female breasts), by body region (i.e., head, chest, abdomen/pelvis), patient age, and time period (1977-1990, 1991-2000, 2001-2014). Relatively high doses were received by the brain from head CTs in the early 1990s, with individual mean doses (mean of 200 simulated values) of up to 66 mGy per scan. Optimization strategies implemented since the late 1990s have resulted in an overall decrease in doses over time, especially at young ages. In chest CTs, active bone marrow doses dropped from over 15 mGy prior to 1991 to approximately 5 mGy per scan after 2001. Our findings illustrate patterns of age-specific doses and their temporal changes, and provide suitable dose estimates for radiation-induced risk estimation in epidemiological studies.
Collapse
Affiliation(s)
- Isabelle Thierry-Chef
- International Agency for Research on Cancer, Lyon, France
- Barcelona Institute for Global Health (ISGlobal), Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
- Ciber Epidemiología y Salud Pública (CIBERESP), Madrid, Spain
| | - Gilles Ferro
- International Agency for Research on Cancer, Lyon, France
| | - Lucian Le Cornet
- Institute of Medical Biostatistics, Epidemiology and Informatics, University Medical Center Mainz, Mainz, Germany
- German Cancer Research Center, Heidelberg, Germany
| | - Jérémie Dabin
- Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium
| | - Tore S Istad
- Norwegian Radiation and Nuclear Safety Authority, NO-0213 Oslo, Norway
| | - Andreas Jahnen
- Luxembourg Institute of Science and Technology, Esch-sur-Alzette, Luxembourg
| | - Choonsik Lee
- Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Rockville, Maryland
| | | | | | - Hilde M Olerud
- University of South-Eastern Norway, Faculty of Health and Social Sciences, Kongsberg, Norway
| | - Richard W Harbron
- Institute of Health and Society, Newcastle University (UNEW), Newcastle upon Tyne, United Kingdom
- NIHR Health Protection Research Unit in Chemical and Radiation Threats and Hazards, Newcastle University, United Kingdom
- Barcelona Institute for Global Health (ISGlobal), Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
- Ciber Epidemiología y Salud Pública (CIBERESP), Madrid, Spain
| | - Jordi Figuerola
- Barcelona Institute for Global Health (ISGlobal), Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
- Ciber Epidemiología y Salud Pública (CIBERESP), Madrid, Spain
| | - Johannes Hermen
- Luxembourg Institute of Science and Technology, Esch-sur-Alzette, Luxembourg
| | | | - Marie-Odile Bernier
- Institut de Radioprotection et de Sûreté Nucléaire, Laboratoire d'épidémiologie des Rayonnements Ionisants, Fontenay-aux-Roses, France
| | - Magda Bosch Bosch de Basea
- Barcelona Institute for Global Health (ISGlobal), Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
- Ciber Epidemiología y Salud Pública (CIBERESP), Madrid, Spain
| | - Graham Byrnes
- International Agency for Research on Cancer, Lyon, France
| | - Elisabeth Cardis
- Barcelona Institute for Global Health (ISGlobal), Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
- Ciber Epidemiología y Salud Pública (CIBERESP), Madrid, Spain
| | - Michael Hauptmann
- Department of Epidemiology and Biostatistics, Netherlands Cancer Institute, Amsterdam, the Netherlands
- Institute of BiostatisTics and Registry Research, Medical University Brandenburg Theodor Fontane, Neuruppin, Germany
| | - Neige Journy
- Institut de Radioprotection et de Sûreté Nucléaire, Laboratoire d'épidémiologie des Rayonnements Ionisants, Fontenay-aux-Roses, France
- French National Institute of Health and Medical Research (Inserm) Unit 1018, Centre for Research in Epidemiology and Population Health (CESP), Cancer and Radiations Group, Gustave Roussy, Villejuif, France
| | | | - Johanna M Meulepas
- Department of Epidemiology and Biostatistics, Netherlands Cancer Institute, Amsterdam, the Netherlands
| | - Roman Pokora
- Institute of Medical Biostatistics, Epidemiology and Informatics, University Medical Center Mainz, Mainz, Germany
| | - Steven L Simon
- Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Rockville, Maryland
| |
Collapse
|
4
|
Eder H, Schlattl H. Shielding effectiveness of X-ray protective garment. Phys Med 2021; 82:343-350. [PMID: 33765649 DOI: 10.1016/j.ejmp.2021.01.081] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 01/26/2021] [Accepted: 01/29/2021] [Indexed: 11/28/2022] Open
Abstract
PURPOSE Certification of the X-ray shielding garment is based on attenuation testing on flat material samples. We investigated the difference of shielding effectiveness compared to realistic use when the garment is worn on the body of a staff person. METHODS Attenuation factors of X-ray protective aprons have been evaluated for several clinical scenarios with Monte Carlo (MC) calculations based on the ICRP female reference model and an experimental setup. The MC calculated attenuation factors refer to the effective dose E, whereas the measured attenuation factors refer to the personal dose equivalent Hp(10). The calculated/measured factors were compared to the attenuation factors of the identical materials measured under the conditions of the standard IEC 61331-1 that is currently in use for the type testing of X-ray protective aprons. RESULTS As a result, for example, at a common tube voltage of 80 kV, the real attenuation factors of a 0.35 mm Pb apron worn by a 3-dimensional body were 38% to 76% higher than when measured under IEC conditions on flat samples. The MC-calculated organ doses show the maximum contribution to E being within the operatoŕs abdomen/pelvis region. CONCLUSIONS With our findings, personal X-ray protective garments could be improved in effectiveness.
Collapse
Affiliation(s)
- H Eder
- Formerly Bavarian Environment Agency, priv. Am Stadtpark 43, D-81243 München, Germany.
| | - H Schlattl
- Helmholtz Zentrum München, Deutsches Forschungszentrum für Gesundheit und Umwelt (GmbH), Ingolstädter Landstraße 1, D-85764 Neuherberg, Germany.
| |
Collapse
|
5
|
Fehrmann ML, Schegerer A, Werncke T, Schlattl H. COMPARISON OF EXPERIMENTAL AND NUMERICAL METHODS OF PATIENT DOSE ESTIMATIONS IN CT USING ANTHROPOMORPHIC MODELS. RADIATION PROTECTION DOSIMETRY 2020; 190:71-83. [PMID: 32744624 DOI: 10.1093/raddos/ncaa070] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 02/20/2020] [Accepted: 04/05/2020] [Indexed: 06/11/2023]
Abstract
The common methods for patient dose estimations in computed tomography (CT) are thermoluminescence dosemeter (TLD) measurements or the usage of software packages based on Monte Carlo simulations like CT-Expo or the newer CTVoxDos, which uses the ICRP Reference Adult Male (ICRP 110). Organ (OD) and effective doses of a CT protocol of the upper abdomen are compared. Compared to CTVoxDos, ODs inferred by TLD measurement using an anthropomorphic phantom differ by $\mathbf{(19\pm 16)\,\%}$ inside the primary radiation field, $\mathbf{(14\pm 2)\,\%}$ for partially primary irradiated organs and $\mathbf{(34\pm 38)\,\%}$ in the scattered radiation field. ODs estimated by CT-Expo show a mean deviation of $\mathbf{(16\pm 9)\,\%}$ (primary irradiated) and $\mathbf{(28\pm 31)\,\%}$ (scatter irradiated) from ODs estimated by CTVoxDos.
Collapse
Affiliation(s)
- M L Fehrmann
- Institute of Radiation Medicine, Helmholtz Zentrum München-German Research Center for Environmental Health, 85764 Neuherberg, Germany
- Lehrstuhl für Experimentelle Physik IV, Technische Universität Dortmund, 44227 Dortmund, Germany
| | - A Schegerer
- Medizinischer und beruflicher Strahlenschutz, Bundesamt für Strahlenschutz, 85764 Neuherberg, Germany
- Hirslanden AG, 8152 Glattpark, Switzerland
| | - T Werncke
- Institut für Diagnostische und Interventionelle Radiologie, Medizinische Hochschule Hannover, 30625 Hannover, Germany
| | - H Schlattl
- Institute of Radiation Medicine, Helmholtz Zentrum München-German Research Center for Environmental Health, 85764 Neuherberg, Germany
| |
Collapse
|
6
|
Gao Y, Mahmood U, Liu T, Quinn B, Gollub MJ, Xu XG, Dauer LT. Patient-Specific Organ and Effective Dose Estimates in Adult Oncologic CT. AJR Am J Roentgenol 2020; 214:738-746. [PMID: 31414882 PMCID: PMC7393764 DOI: 10.2214/ajr.19.21197] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVE. Patient-specific organ and effective dose provides essential information for CT protocol optimization. However, such information is not readily available in the scan records. The purpose of this study was to develop a method to obtain accurate examination- and patient-specific organ and effective dose estimates by use of available scan data and patient body size information for a large cohort of patients. MATERIALS AND METHODS. The data were randomly collected for 1200 patients who underwent CT in a 2-year period. Physical characteristics of the patients and CT technique were processed as inputs for the dose estimator. Organ and effective doses were estimated by use of the inputs and computational human phantoms matched to patients on the basis of sex and effective diameter. Size-based ratios were applied to correct for patient-phantom body size differences. RESULTS. Patients received a mean of 59.9 mGy to the lens of the eye per brain scan, 10.1 mGy to the thyroid per chest scan, 17.5 mGy to the liver per abdomen and pelvis scan, and 19.0 mGy to the liver per body scan. A factor of 2 difference in dose estimates was observed between patients of various habitus. CONCLUSION. Examination- and patient-specific organ and effective doses were estimated for 1200 adult oncology patients undergoing CT. The dose conversion factors calculated facilitate rapid organ and effective dose estimation in clinics. Compared with nonspecific dose estimation methods, patient dose estimations with data specific to the patient and examination can differ by a factor of 2.
Collapse
Affiliation(s)
- Yiming Gao
- Department of Medical Physics, Box 84, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
| | - Usman Mahmood
- Department of Medical Physics, Box 84, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
| | - Tianyu Liu
- Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - Brian Quinn
- Department of Medical Physics, Box 84, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
| | - Marc J. Gollub
- Department of Radiology, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
| | - X. George Xu
- Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - Lawrence T. Dauer
- Department of Medical Physics, Box 84, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
- Department of Radiology, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
| |
Collapse
|
7
|
Muhammad N, Karim M, Hassan H, Kamarudin M, Wong J, Ibahim M. Estimation of effective dose and organ cancer risk from paediatric computed tomography thorax – Abdomen - Pelvis examinations. Radiat Phys Chem Oxf Engl 1993 2019. [DOI: 10.1016/j.radphyschem.2019.108438] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
8
|
Papadimitroulas P, Balomenos A, Kopsinis Y, Loudos G, Alexakos C, Karnabatidis D, Kagadis GC, Kostou T, Chatzipapas K, Visvikis D, Mountris KA, Jaouen V, Katsanos K, Diamantopoulos A, Apostolopoulos D. A Review on Personalized Pediatric Dosimetry Applications Using Advanced Computational Tools. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2019. [DOI: 10.1109/trpms.2018.2876562] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
9
|
Kostou T, Papadimitroulas P, Papaconstadopoulos P, Devic S, Seuntjens J, Kagadis GC. Size-specific dose estimations for pediatric chest, abdomen/pelvis and head CT scans with the use of GATE. Phys Med 2019; 65:181-190. [PMID: 31494372 DOI: 10.1016/j.ejmp.2019.08.020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 07/24/2019] [Accepted: 08/29/2019] [Indexed: 01/17/2023] Open
Abstract
PURPOSE The purpose of this study is to create an organ dose database for pediatric individuals undergoing chest, abdomen/pelvis, and head computed tomography (CT) examinations, and to report the differences in absorbed organ doses, when anatomical differences exist for pediatric patients. METHODS The GATE Monte Carlo (MC) toolkit was used to model the GE BrightSpeed Elite CT model. The simulated scanner model was validated with the standard Computed Tomography Dose Index (CTDI) head phantom. Twelve computational models (2.1-14 years old) were used. First, contributions to effective dose and absorbed doses per CTDIvol and per 100 mAs were estimated for all organs. Then, doses per CTDIvol were correlated with patient model weight for the organs inside the scan range for chest and abdomen/pelvis protocols. Finally, effective doses per dose-length product (DLP) were estimated and compared with the conventional conversion k-factors. RESULTS The system was validated against experimental CTDIw measurements. The doses per CTDIvol and per 100 mAs for selected organs were estimated. The magnitude of the dependency between the dose and the anatomical characteristics was calculated with the coefficient of determination at 0.5-0.7 for the internal scan organs for chest and abdomen/pelvis protocols. Finally, effective doses per DLP were compared with already published data, showing discrepancies between 13 and 29% and were correlated strongly with the total weight (R2 > 0.8) for the chest and abdomen protocols. CONCLUSIONS Big differences in absorbed doses are reported even for patients of similar age or same gender, when anatomical differences exist on internal organs of the body.
Collapse
Affiliation(s)
- Theodora Kostou
- University of Patras, Department of Medical Physics, Patras, Greece
| | | | | | - Slobodan Devic
- McGill University, Department of Medical Physics, Montreal, Canada
| | - Jan Seuntjens
- McGill University, Department of Medical Physics, Montreal, Canada
| | - George C Kagadis
- University of Patras, Department of Medical Physics, Patras, Greece.
| |
Collapse
|
10
|
Hassan AI, Skalej M, Schlattl H, Hoeschen C. Determination and verification of the x-ray spectrum of a CT scanner. J Med Imaging (Bellingham) 2018; 5:013506. [PMID: 29430476 DOI: 10.1117/1.jmi.5.1.013506] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Accepted: 01/10/2018] [Indexed: 11/14/2022] Open
Abstract
The accuracy of Monte Carlo (MC) simulations in estimating the computed tomography radiation dose is highly dependent on the proprietary x-ray source information. To address this, this study develops a method to precisely estimate the x-ray spectrum and bowtie (BT) filter thickness of the x-ray source based on physical measurements and calculations. The static x-ray source of the CT localizer radiograph was assessed to measure the total filtration at the isocenter for the x-ray spectrum characterization and the BT profile (air-kerma values as a function of fan angle). With these values, the utilized BT filter in the localizer radiograph was assessed by integrating the measured air kerma in a full 360-deg cycle. The consistency observed between the integrated BT filter profiles and the directly measured profiles pointed to the similarity in the utilized BT filter in terms of thickness and material between the static and rotating x-ray geometries. Subsequently, the measured air kerma was used to calculate the BT filter thickness and was verified using MC simulations by comparing the calculated and measured air-kerma values, where a very good agreement was observed. This would allow a more accurate computed tomography simulation and facilitate the estimation of the dose delivered to the patients.
Collapse
Affiliation(s)
- Ahmad Ibrahim Hassan
- Otto von Guericke Universität Magdeburg, Universitätsklinikum Magdeburg A.ö.R., Institut für Neuroradiologie, Magdeburg, Deutschland, Germany.,Otto von Guericke Universität, Institut für Medizintechnik, Fakultät für Elektrotechnik und Informationstechnik Universitätsplatz, Magdeburg, Deutschland, Germany
| | - Martin Skalej
- Otto von Guericke Universität Magdeburg, Universitätsklinikum Magdeburg A.ö.R., Institut für Neuroradiologie, Magdeburg, Deutschland, Germany
| | - Helmut Schlattl
- Institute of Radiation Protection, Helmholtz Zentrum München-German Research Center for Environmental Health, Neuherberg, Deutschland, Germany
| | - Christoph Hoeschen
- Otto von Guericke Universität, Institut für Medizintechnik, Fakultät für Elektrotechnik und Informationstechnik Universitätsplatz, Magdeburg, Deutschland, Germany
| |
Collapse
|
11
|
Gao Y, Quinn B, Pandit-Taskar N, Behr G, Mahmood U, Long D, Xu XG, St Germain J, Dauer LT. Patient-specific organ and effective dose estimates in pediatric oncology computed tomography. Phys Med 2018; 45:146-155. [PMID: 29472080 PMCID: PMC5828028 DOI: 10.1016/j.ejmp.2017.12.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 11/27/2017] [Accepted: 12/15/2017] [Indexed: 12/26/2022] Open
Abstract
PURPOSE Estimate organ and effective doses from computed tomography scans of pediatric oncologic patients using patient-specific information. MATERIALS AND METHODS With IRB approval patient-specific scan parameters and patient size obtained from DICOM images and vendor-provided dose monitoring application were obtained for a cross-sectional study of 1250 pediatric patients from 0 through 20 y-olds who underwent head, chest, abdomen-pelvis, or chest-abdomen-pelvis CT scans. Patients were categorized by age. Organ doses and effective doses were estimated using VirtualDose™ CT based on patient-specific information, tube current modulation (TCM), and age-specific realistic phantoms. CTDIvol, DLP, and dose results were compared with those reported in the literature. RESULTS CTDIvol and DLP varied widely as patient size varied. The 75th percentiles of CTDIvol and DLP were no greater than in the literature with the exception of head scans of 16-20 y-olds and of abdomen-pelvis scans of larger patients. Eye lens dose from a head scan was up to 69 mGy. Mean organ doses agreed with other studies at maximal difference of 38% for chest and 41% for abdomen-pelvis scans. Mean effective dose was generally higher for older patients. The highest effective doses were estimated for the 16-20 y-olds as: head 3.3 mSv, chest 4.1 mSv, abdomen-pelvis 10.0 mSv, chest-abdomen-pelvis 14.0 mSv. CONCLUSION Patient-specific organ and effective doses have been estimated for pediatric oncologic patients from <1 through 20 y-olds. The effect of TCM was successfully accounted for in the estimates. Output parameters varied with patient size. CTDIvol and DLP results are useful for future protocol optimization.
Collapse
Affiliation(s)
- Yiming Gao
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA.
| | - Brian Quinn
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA.
| | - Neeta Pandit-Taskar
- Department of Radiology, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA.
| | - Gerald Behr
- Department of Radiology, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA.
| | - Usman Mahmood
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA.
| | - Daniel Long
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA.
| | - X George Xu
- Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.
| | - Jean St Germain
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA.
| | - Lawrence T Dauer
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA; Department of Radiology, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA.
| |
Collapse
|
12
|
Stepusin EJ, Long DJ, Ficarrotta KR, Hintenlang DE, Bolch WE. Physical validation of a Monte Carlo-based, phantom-derived approach to computed tomography organ dosimetry under tube current modulation. Med Phys 2017; 44:5423-5432. [PMID: 28688151 PMCID: PMC6343853 DOI: 10.1002/mp.12461] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 06/26/2017] [Accepted: 06/30/2017] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To physically validate the accuracy of a Monte Carlo-based, phantom-derived methodology for computed tomography (CT) dosimetry that utilizes organ doses from precomputed axial scans and that accounts for tube current modulation (TCM). METHODS The output of a Toshiba Aquilion ONE CT scanner was modeled, based on physical measurement, in the Monte Carlo radiation transport code MCNPX (v2.70). CT examinations were taken of two anthropomorphic phantoms representing pediatric and adult patients (15-yr-old female and adult male) at various energies, in which physical organ dose measurements were made using optically stimulated luminescence dosimeters (OSLDs). These exams (chest-abdomen-pelvis) were modeled using organ dose data obtained from the computationally equivalent phantom of each anthropomorphic phantom. TCM was accounted for by weighting all organ dose contributions by both the relative attenuation of the phantom and the image-derived mA value (from the DICOM header) at the same z-extent (cranial-caudal direction) of the axial dose data. RESULTS The root mean squares of percent difference in organ dose when comparing the physical organ dose measurements to the computational estimates were 21.2, 12.1, and 15.1% for the uniform (no attenuation weighting), weighted (computationally derived), and image-based methodologies, respectively. CONCLUSIONS Overall, these data suggest that the Monte Carlo-based dosimetry presented in this work is viable for CT dosimetry. Additionally, for CT exams with TCM, local attenuation weighting of organ dose contributions from precomputed axial dosimetry libraries increases organ dose accuracy.
Collapse
Affiliation(s)
- Elliott J. Stepusin
- J Crayton Pruitt Family Department of Biomedical EngineeringUniversity of FloridaGainesvilleFL32611‐6131USA
| | - Daniel J. Long
- Department of Medical PhysicsMemorial Sloan Kettering Cancer Center1275 York AvenueNew YorkNY10065USA
| | - Kayla R. Ficarrotta
- J Crayton Pruitt Family Department of Biomedical EngineeringUniversity of FloridaGainesvilleFL32611‐6131USA
- Present address:
Department of Chemical & Biomedical EngineeringUniversity of South FloridaTampaFL33620USA
| | - David E. Hintenlang
- J Crayton Pruitt Family Department of Biomedical EngineeringUniversity of FloridaGainesvilleFL32611‐6131USA
- Present address:
Department of RadiologyOhio State UniversityWexner Medical Center Suite 450ColumbusOH43210USA
| | - Wesley E. Bolch
- J Crayton Pruitt Family Department of Biomedical EngineeringUniversity of FloridaGainesvilleFL32611‐6131USA
| |
Collapse
|
13
|
McMillan K, Bostani M, Cagnon CH, Yu L, Leng S, McCollough CH, McNitt-Gray MF. Estimating patient dose from CT exams that use automatic exposure control: Development and validation of methods to accurately estimate tube current values. Med Phys 2017; 44:4262-4275. [PMID: 28477342 DOI: 10.1002/mp.12314] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Revised: 04/04/2017] [Accepted: 04/09/2017] [Indexed: 02/05/2023] Open
Abstract
PURPOSE The vast majority of body CT exams are performed with automatic exposure control (AEC), which adapts the mean tube current to the patient size and modulates the tube current either angularly, longitudinally or both. However, most radiation dose estimation tools are based on fixed tube current scans. Accurate estimates of patient dose from AEC scans require knowledge of the tube current values, which is usually unavailable. The purpose of this work was to develop and validate methods to accurately estimate the tube current values prescribed by one manufacturer's AEC system to enable accurate estimates of patient dose. METHODS Methods were developed that took into account available patient attenuation information, user selected image quality reference parameters and x-ray system limits to estimate tube current values for patient scans. Methods consistent with AAPM Report 220 were developed that used patient attenuation data that were: (a) supplied by the manufacturer in the CT localizer radiograph and (b) based on a simulated CT localizer radiograph derived from image data. For comparison, actual tube current values were extracted from the projection data of each patient. Validation of each approach was based on data collected from 40 pediatric and adult patients who received clinically indicated chest (n = 20) and abdomen/pelvis (n = 20) scans on a 64 slice multidetector row CT (Sensation 64, Siemens Healthcare, Forchheim, Germany). For each patient dataset, the following were collected with Institutional Review Board (IRB) approval: (a) projection data containing actual tube current values at each projection view, (b) CT localizer radiograph (topogram) and (c) reconstructed image data. Tube current values were estimated based on the actual topogram (actual-topo) as well as the simulated topogram based on image data (sim-topo). Each of these was compared to the actual tube current values from the patient scan. In addition, to assess the accuracy of each method in estimating patient organ doses, Monte Carlo simulations were performed by creating voxelized models of each patient, identifying key organs and incorporating tube current values into the simulations to estimate dose to the lungs and breasts (females only) for chest scans and the liver, kidney, and spleen for abdomen/pelvis scans. Organ doses from simulations using the actual tube current values were compared to those using each of the estimated tube current values (actual-topo and sim-topo). RESULTS When compared to the actual tube current values, the average error for tube current values estimated from the actual topogram (actual-topo) and simulated topogram (sim-topo) was 3.9% and 5.8% respectively. For Monte Carlo simulations of chest CT exams using the actual tube current values and estimated tube current values (based on the actual-topo and sim-topo methods), the average differences for lung and breast doses ranged from 3.4% to 6.6%. For abdomen/pelvis exams, the average differences for liver, kidney, and spleen doses ranged from 4.2% to 5.3%. CONCLUSIONS Strong agreement between organ doses estimated using actual and estimated tube current values provides validation of both methods for estimating tube current values based on data provided in the topogram or simulated from image data.
Collapse
Affiliation(s)
- Kyle McMillan
- Biomedical Physics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.,Department of Radiology, Mayo Clinic, Rochester, MN, 55905, USA
| | - Maryam Bostani
- Biomedical Physics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.,Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA
| | - Christopher H Cagnon
- Biomedical Physics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.,Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA
| | - Lifeng Yu
- Department of Radiology, Mayo Clinic, Rochester, MN, 55905, USA
| | - Shuai Leng
- Department of Radiology, Mayo Clinic, Rochester, MN, 55905, USA
| | | | - Michael F McNitt-Gray
- Biomedical Physics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.,Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA
| |
Collapse
|
14
|
Bostani M, McMillan K, Lu P, Kim GHJ, Cody D, Arbique G, Greenberg SB, DeMarco JJ, Cagnon CH, McNitt‐Gray MF. Estimating organ doses from tube current modulated CT examinations using a generalized linear model. Med Phys 2017; 44:1500-1513. [PMID: 28112399 PMCID: PMC6192538 DOI: 10.1002/mp.12119] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 12/19/2016] [Accepted: 01/15/2017] [Indexed: 12/16/2022] Open
Abstract
PURPOSE Currently, available Computed Tomography dose metrics are mostly based on fixed tube current Monte Carlo (MC) simulations and/or physical measurements such as the size specific dose estimate (SSDE). In addition to not being able to account for Tube Current Modulation (TCM), these dose metrics do not represent actual patient dose. The purpose of this study was to generate and evaluate a dose estimation model based on the Generalized Linear Model (GLM), which extends the ability to estimate organ dose from tube current modulated examinations by incorporating regional descriptors of patient size, scanner output, and other scan-specific variables as needed. METHODS The collection of a total of 332 patient CT scans at four different institutions was approved by each institution's IRB and used to generate and test organ dose estimation models. The patient population consisted of pediatric and adult patients and included thoracic and abdomen/pelvis scans. The scans were performed on three different CT scanner systems. Manual segmentation of organs, depending on the examined anatomy, was performed on each patient's image series. In addition to the collected images, detailed TCM data were collected for all patients scanned on Siemens CT scanners, while for all GE and Toshiba patients, data representing z-axis-only TCM, extracted from the DICOM header of the images, were used for TCM simulations. A validated MC dosimetry package was used to perform detailed simulation of CT examinations on all 332 patient models to estimate dose to each segmented organ (lungs, breasts, liver, spleen, and kidneys), denoted as reference organ dose values. Approximately 60% of the data were used to train a dose estimation model, while the remaining 40% was used to evaluate performance. Two different methodologies were explored using GLM to generate a dose estimation model: (a) using the conventional exponential relationship between normalized organ dose and size with regional water equivalent diameter (WED) and regional CTDIvol as variables and (b) using the same exponential relationship with the addition of categorical variables such as scanner model and organ to provide a more complete estimate of factors that may affect organ dose. Finally, estimates from generated models were compared to those obtained from SSDE and ImPACT. RESULTS The Generalized Linear Model yielded organ dose estimates that were significantly closer to the MC reference organ dose values than were organ doses estimated via SSDE or ImPACT. Moreover, the GLM estimates were better than those of SSDE or ImPACT irrespective of whether or not categorical variables were used in the model. While the improvement associated with a categorical variable was substantial in estimating breast dose, the improvement was minor for other organs. CONCLUSIONS The GLM approach extends the current CT dose estimation methods by allowing the use of additional variables to more accurately estimate organ dose from TCM scans. Thus, this approach may be able to overcome the limitations of current CT dose metrics to provide more accurate estimates of patient dose, in particular, dose to organs with considerable variability across the population.
Collapse
Affiliation(s)
- Maryam Bostani
- Departments of Biomedical Physics and RadiologyDavid Geffen School of MedicineUniversity of California Los AngelesLos AngelesCA90024USA
| | - Kyle McMillan
- Department of RadiologyMayo ClinicCT Clinical Innovation CenterRochesterMN55905USA
| | - Peiyun Lu
- Departments of Biomedical Physics and RadiologyDavid Geffen School of MedicineUniversity of California Los AngelesLos AngelesCA90024USA
| | - Grace Hyun J. Kim
- Departments of Biomedical Physics and RadiologyDavid Geffen School of MedicineUniversity of California Los AngelesLos AngelesCA90024USA
| | - Dianna Cody
- Department of Imaging PhysicsUniversity of TexasMD Anderson Cancer CenterHoustonTX77030USA
| | | | - S. Bruce Greenberg
- Department of RadiologyArkansas Children's HospitalLittle RockAR72202USA
| | - John J. DeMarco
- Department of Radiation OncologyCedars‐Sinai Medical CenterLos AngelesCA90048USA
- Present address:
Department of Radiation OncologyDavid Geffen School of Medicine at UCLA
| | - Chris H. Cagnon
- Departments of Biomedical Physics and RadiologyDavid Geffen School of MedicineUniversity of California Los AngelesLos AngelesCA90024USA
| | - Michael F. McNitt‐Gray
- Departments of Biomedical Physics and RadiologyDavid Geffen School of MedicineUniversity of California Los AngelesLos AngelesCA90024USA
| |
Collapse
|
15
|
Sanders J, Tian X, Segars WP, Boone J, Samei E. Automated, patient-specific estimation of regional imparted energy and dose from tube current modulated computed tomography exams across 13 protocols. J Med Imaging (Bellingham) 2017; 4:013503. [PMID: 28149922 DOI: 10.1117/1.jmi.4.1.013503] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 12/29/2016] [Indexed: 11/14/2022] Open
Abstract
Currently, computed tomography (CT) dosimetry relies on surrogates for dose, such as CT dose index and size-specific dose estimates, rather than dose per se. Organ dose is considered as the gold standard for radiation dosimetry. However, organ dose estimation requires precise knowledge of organ locations. Regional imparted energy and dose can also be used to quantify radiation burden and are beneficial because they do not require knowledge of organ size or location. This work investigated an automated technique to retrospectively estimate the imparted energy from tube current-modulated (TCM) CT exams across 13 protocols. Monte Carlo simulations of various head and body TCM CT examinations across various tube potentials and TCM strengths were performed on 58 adult computational extended cardiac-torso phantoms to develop relationships between scanned mass and imparted energy normalized by dose length product. Results from the Monte Carlo simulations indicate that normalized imparted energy increases with increasing both scanned mass and tube potential, but it is relatively unaffected by the strength of the TCM. The automated algorithm was tested on 40 clinical datasets with a 98% success rate.
Collapse
Affiliation(s)
- Jeremiah Sanders
- Duke University, Medical Physics Graduate Program, 2424 Erwin Road, Suite 101, Durham, North Carolina 27705, United States; Duke University, Clinical Imaging Physics Group, 2424 Erwin Road, Suite 302, Durham, North Carolina 27705, United States; Duke University, Carl E. Ravin Advanced Imaging Laboratories, 2424 Erwin Road, Suite 302, Durham, North Carolina 27705, United States
| | - Xiaoyu Tian
- Duke University, Carl E. Ravin Advanced Imaging Laboratories, 2424 Erwin Road, Suite 302, Durham, North Carolina 27705, United States; Duke University, Department of Biomedical Engineering, 101 Science Drive, Campus Box 90281, Durham, North Carolina 27708, United States
| | - William Paul Segars
- Duke University, Medical Physics Graduate Program, 2424 Erwin Road, Suite 101, Durham, North Carolina 27705, United States; Duke University, Carl E. Ravin Advanced Imaging Laboratories, 2424 Erwin Road, Suite 302, Durham, North Carolina 27705, United States; Duke University, Department of Radiology, 2301 Erwin Road, Box 3808, Durham, North Carolina 27710, United States
| | - John Boone
- University of California Davis , Departments of Radiology and Biomedical Engineering, Engineering, 451 Health Sciences Drive, GBSF Room 2303, Davis, California 95616, United States
| | - Ehsan Samei
- Duke University, Medical Physics Graduate Program, 2424 Erwin Road, Suite 101, Durham, North Carolina 27705, United States; Duke University, Clinical Imaging Physics Group, 2424 Erwin Road, Suite 302, Durham, North Carolina 27705, United States; Duke University, Carl E. Ravin Advanced Imaging Laboratories, 2424 Erwin Road, Suite 302, Durham, North Carolina 27705, United States; Duke University, Department of Biomedical Engineering, 101 Science Drive, Campus Box 90281, Durham, North Carolina 27708, United States; Duke University, Department of Radiology, 2301 Erwin Road, Box 3808, Durham, North Carolina 27710, United States; Duke University, Departments of Physics and Electrical and Computer Engineering, 2424 Erwin Road, Suite 302, Durham, North Carolina 27705, United States
| |
Collapse
|
16
|
Akhlaghi P, Hakimabad HM, Motavalli LR. Evaluation of dose conversion coefficients for an eight-year-old Iranian male phantom undergoing computed tomography. RADIATION AND ENVIRONMENTAL BIOPHYSICS 2015; 54:465-474. [PMID: 26082027 DOI: 10.1007/s00411-015-0607-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2014] [Accepted: 06/06/2015] [Indexed: 06/04/2023]
Abstract
In order to construct a library of Iranian pediatric voxel phantoms for radiological protection and dosimetry applications, an Iranian eight-year-old phantom was constructed from a series of CT images. Organ and effective dose conversion coefficients to this phantom were calculated for head, chest, abdominopelvis and chest-abdomen-pelvis scans at tube voltages of 80, 100 and 120 kVp. To validate the results, the organ and effective dose conversion coefficients obtained were compared with those of the University of Florida eight-year-old voxel female phantom as a function of examination type and anatomical scan area. For a detailed study, depth distributions of organs together with the thickness of surrounding tissues located in the beam path, which are shielding the internal organs, were determined for these two voxel phantoms. The relation between the anatomical differences and the level of delivered dose was investigated and the discrepancies among the results justified.
Collapse
Affiliation(s)
- Parisa Akhlaghi
- Physics Department, Faculty of Science, Ferdowsi University of Mashhad, Azadi Sq., 91775-1436, Mashhad, Iran
| | - Hashem Miri Hakimabad
- Physics Department, Faculty of Science, Ferdowsi University of Mashhad, Azadi Sq., 91775-1436, Mashhad, Iran.
| | - Laleh Rafat Motavalli
- Physics Department, Faculty of Science, Ferdowsi University of Mashhad, Azadi Sq., 91775-1436, Mashhad, Iran
| |
Collapse
|
17
|
Schmidt R, Wulff J, Zink K. GMctdospp: Description and validation of a CT dose calculation system. Med Phys 2015; 42:4260-70. [PMID: 26133624 DOI: 10.1118/1.4922391] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
PURPOSE To develop a Monte Carlo (MC)-based computed tomography (CT) dose estimation method with a graphical user interface with options to define almost arbitrary simulation scenarios, to make calculations sufficiently fast for comfortable handling, and to make the software free of charge for general availability to the scientific community. METHODS A framework called GMctdospp was developed to calculate phantom and patient doses with the MC method based on the EGSnrc system. A CT scanner was modeled for testing and was adapted to half-value layer, beam-shaping filter, z-profile, and tube-current modulation (TCM). To validate the implemented variance reduction techniques, depth-dose and cross-profile calculations of a static beam were compared against DOSXYZnrc/EGSnrc. Measurements for beam energies of 80 and 120 kVp at several positions of a CT dose-index (CTDI) standard phantom were compared against calculations of the created CT model. Finally, the efficiency of the adapted code was benchmarked against EGSnrc defaults. RESULTS The CT scanner could be modeled accurately. The developed TCM scheme was confirmed by the dose measurement. A comparison of calculations to DOSXYZnrc showed no systematic differences. Measurements in a CTDI phantom could be reproduced within 2% average, with a maximal difference of about 6%. Efficiency improvements of about six orders of magnitude were observed for larger organ structures of a chest-examination protocol in a voxelized phantom. In these cases, simulations took 25 s to achieve a statistical uncertainty of ∼0.5%. CONCLUSIONS A fast dose-calculation system for phantoms and patients in a CT examination was developed, successfully validated, and benchmarked. Influences of scan protocols, protection method, and other issues can be easily examined with the developed framework.
Collapse
Affiliation(s)
- Ralph Schmidt
- Institut für Medizinische Physik und Strahlenschutz-IMPS, University of Applied Sciences Gießen, Gießen 35390, Germany
| | - Jörg Wulff
- Institut für Medizinische Physik und Strahlenschutz-IMPS, University of Applied Sciences Gießen, Gießen 35390, Germany
| | - Klemens Zink
- Institut für Medizinische Physik und Strahlenschutz-IMPS, University of Applied Sciences Gießen, Gießen 35390, Germany and Department of Radiotherapy and Radiation Oncology, University Medical Center Giessen and Marburg, Marburg 35043, Germany
| |
Collapse
|
18
|
Barrett HH, Myers KJ, Hoeschen C, Kupinski MA, Little MP. Task-based measures of image quality and their relation to radiation dose and patient risk. Phys Med Biol 2015; 60:R1-75. [PMID: 25564960 PMCID: PMC4318357 DOI: 10.1088/0031-9155/60/2/r1] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The theory of task-based assessment of image quality is reviewed in the context of imaging with ionizing radiation, and objective figures of merit (FOMs) for image quality are summarized. The variation of the FOMs with the task, the observer and especially with the mean number of photons recorded in the image is discussed. Then various standard methods for specifying radiation dose are reviewed and related to the mean number of photons in the image and hence to image quality. Current knowledge of the relation between local radiation dose and the risk of various adverse effects is summarized, and some graphical depictions of the tradeoffs between image quality and risk are introduced. Then various dose-reduction strategies are discussed in terms of their effect on task-based measures of image quality.
Collapse
Affiliation(s)
- Harrison H. Barrett
- College of Optical Sciences, University of Arizona, Tucson, AZ
- Center for Gamma-Ray Imaging, Department of Medical Imaging, University of Arizona, Tucson, AZ
| | - Kyle J. Myers
- Division of Imaging and Applied Mathematics, Office of Scientific and Engineering Laboratories, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, MD
| | - Christoph Hoeschen
- Department of Electrical Engineering and Information Technology, Otto-von-Guericke University, Magdeburg, Germany
- Research unit Medical Radiation Physics and Diagnostics, Helmholtz Zentrum München, Oberschleissheim, Germany
| | - Matthew A. Kupinski
- College of Optical Sciences, University of Arizona, Tucson, AZ
- Center for Gamma-Ray Imaging, Department of Medical Imaging, University of Arizona, Tucson, AZ
| | - Mark P. Little
- Division of Cancer Epidemiology and Genetics, Radiation Epidemiology Branch, National Cancer Institute, Bethesda, MD
| |
Collapse
|
19
|
The reduction in Monte Carlo calculated organ doses from CT with tube current modulation using WILLIAM, a voxel model of seven year-old anatomy. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2014; 37:743-52. [PMID: 25412887 DOI: 10.1007/s13246-014-0314-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Accepted: 11/10/2014] [Indexed: 10/24/2022]
Abstract
The construction of a voxel model of seven year-old male anatomy from a low resolution whole body CT scan acquired with a PET-CT scanner is described. The model is referred to as WILLIAM. The model was used to compare the Monte Carlo calculated relative organ doses with and without tube current modulation from simulated CAP and chest CT examinations. Tube current modulation was simulated in both the angular (x-y plane) and axial (along the z axis) senses. For organs that are located wholly within the scanned anatomy, significant relative dose reductions of approximately 43 to 62 % were calculated when tube current modulation was simulated compared to Monte Carlo calculations that did not include tube current modulation. Organs located outside of the directly irradiated anatomy, experienced a decrease in their relative dose of between 33 and 38 % when tube current modulation was simulated.
Collapse
|
20
|
Halm BM, Franke AA, Lai JF, Turner HC, Brenner DJ, Zohrabian VM, DiMauro R. γ-H2AX foci are increased in lymphocytes in vivo in young children 1 h after very low-dose X-irradiation: a pilot study. Pediatr Radiol 2014; 44:1310-7. [PMID: 24756254 PMCID: PMC4175172 DOI: 10.1007/s00247-014-2983-3] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Revised: 12/30/2013] [Accepted: 03/23/2014] [Indexed: 01/21/2023]
Abstract
BACKGROUND Computed tomography (CT) is an imaging modality involving ionizing radiation. The presence of γ-H2AX foci after low to moderate ionizing radiation exposure has been demonstrated; however it is unknown whether very low ionizing radiation exposure doses from CT exams can induce γ-H2AX formation in vivo in young children. OBJECTIVE To test whether very low ionizing radiation doses from CT exams can induce lymphocytic γ-H2AX foci (phosphorylated histones used as a marker of DNA damage) formation in vivo in young children. MATERIALS AND METHODS Parents of participating children signed a consent form. Blood samples from three children (ages 3-21 months) undergoing CT exams involving very low blood ionizing radiation exposure doses (blood doses of 0.22-1.22 mGy) were collected immediately before and 1 h post CT exams. Isolated lymphocytes were quantified for γ-H2AX foci by a technician blinded to the radiation status and dose of the patients. Paired t-tests and regression analyses were performed with significance levels set at P < 0.05. RESULTS We observed a dose-dependent increase in γ-H2AX foci post-CT exams (P = 0.046) among the three children. Ionizing radiation exposure doses led to a linear increase of foci per cell in post-CT samples (102% between lowest and highest dose). CONCLUSION We found a significant induction of γ-H2AX foci in lymphocytes from post-CT samples of three very young children. When possible, CT exams should be limited or avoided by possibly applying non-ionizing radiation exposure techniques such as US or MRI.
Collapse
Affiliation(s)
- Brunhild M Halm
- University of Hawaii Cancer Center, 1236 Lauhala St., Honolulu, HI, 96813, USA,
| | | | | | | | | | | | | |
Collapse
|
21
|
Measurement-based model of a wide-bore CT scanner for Monte Carlo dosimetric calculations with GMCTdospp software. Phys Med 2014; 30:816-21. [PMID: 25028213 DOI: 10.1016/j.ejmp.2014.06.045] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Revised: 06/24/2014] [Accepted: 06/26/2014] [Indexed: 11/23/2022] Open
Abstract
The aim of this work was to create a model of a wide-bore Siemens Somatom Sensation Open CT scanner for use with GMCTdospp, which is an EGSnrc-based software tool dedicated for Monte Carlo calculations of dose in CT examinations. The method was based on matching spectrum and filtration to half value layer and dose profile, and thus was similar to the method of Turner et al. (Med. Phys. 36, pp. 2154-2164). Input data on unfiltered beam spectra were taken from two sources: the TASMIP model and IPEM Report 78. Two sources of HVL data were also used, namely measurements and documentation. Dose profile along the fan-beam was measured with Gafchromic RTQA-1010 (QA+) film. Two-component model of filtration was assumed: bow-tie filter made of aluminum with 0.5 mm thickness on central axis, and flat filter made of one of four materials: aluminum, graphite, lead, or titanium. Good agreement between calculations and measurements was obtained for models based on the measured values of HVL. Doses calculated with GMCTdospp differed from the doses measured with pencil ion chamber placed in PMMA phantom by less than 5%, and root mean square difference for four tube potentials and three positions in the phantom did not exceed 2.5%. The differences for models based on HVL values from documentation exceeded 10%. Models based on TASMIP spectra and IPEM78 spectra performed equally well.
Collapse
|
22
|
Cassola VF, Kramer R, de Melo Lima VJ, de Oliveira Lira CAB, Khoury HJ, Vieira JW, Robson Brown K. Development of newborn and 1-year-old reference phantoms based on polygon mesh surfaces. JOURNAL OF RADIOLOGICAL PROTECTION : OFFICIAL JOURNAL OF THE SOCIETY FOR RADIOLOGICAL PROTECTION 2013; 33:669-691. [PMID: 23822973 DOI: 10.1088/0952-4746/33/3/669] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The purpose of this study is the development of paediatric reference phantoms for newborn and 1-year-old infants to be used for the calculation of organ and tissue equivalent doses in radiation protection. The study proposes a method for developing anatomically highly sophisticated paediatric phantoms without using medical images. The newborn and 1-year-old hermaphrodite phantoms presented here were developed using three-dimensional (3D) modelling software applied to anatomical information taken from atlases, textbooks and images provided by the Department of Anatomy of the Federal University of Pernambuco, Brazil. The method uses polygon mesh surfaces to model body contours, the shape of organs as well as their positions and orientations in the human body. Organ and tissue masses agree with corresponding data given by the International Commission on Radiological Protection for newborn and 1-year-old reference children. Bones were segmented into cortical bone, spongiosa, medullary marrow and cartilage to allow for the use of μCT images of trabecular bone for skeletal dosimetry. Anatomical results show 3D images of the phantoms' surfaces, organs and skeletons, as well as tables with organ and tissue masses or skeletal tissue volumes. Dosimetric results present comparisons of organ and tissue absorbed doses or specific absorbed fractions between the newborn and 1-year-old phantoms and corresponding data for other paediatric stylised or voxel phantoms. Most differences were found to be below 10%.
Collapse
Affiliation(s)
- V F Cassola
- Department of Nuclear Energy, Federal University of Pernambuco, Avenida Professor Luiz Freire 1000, CEP 50740-540, Recife, Pernambuco, Brazil
| | | | | | | | | | | | | |
Collapse
|
23
|
Khatonabadi M, Kim HJ, Lu P, McMillan KL, Cagnon CH, DeMarco JJ, McNitt-Gray MF. The feasibility of a regional CTDIvol to estimate organ dose from tube current modulated CT exams. Med Phys 2013; 40:051903. [PMID: 23635273 PMCID: PMC4108725 DOI: 10.1118/1.4798561] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Revised: 02/26/2013] [Accepted: 03/14/2013] [Indexed: 12/11/2022] Open
Abstract
PURPOSE In AAPM Task Group 204, the size-specific dose estimate (SSDE) was developed by providing size adjustment factors which are applied to the Computed Tomography (CT) standardized dose metric, CTDI(vol). However, that work focused on fixed tube current scans and did not specifically address tube current modulation (TCM) scans, which are currently the majority of clinical scans performed. The purpose of this study was to extend the SSDE concept to account for TCM by investigating the feasibility of using anatomic and organ specific regions of scanner output to improve accuracy of dose estimates. METHODS Thirty-nine adult abdomen/pelvis and 32 chest scans from clinically indicated CT exams acquired on a multidetector CT using TCM were obtained with Institutional Review Board approval for generating voxelized models. Along with image data, raw projection data were obtained to extract TCM functions for use in Monte Carlo simulations. Patient size was calculated using the effective diameter described in TG 204. In addition, the scanner-reported CTDI(vo)l (CTDI(vol),global) was obtained for each patient, which is based on the average tube current across the entire scan. For the abdomen/pelvis scans, liver, spleen, and kidneys were manually segmented from the patient datasets; for the chest scans, lungs and for female models only, glandular breast tissue were segmented. For each patient organ doses were estimated using Monte Carlo Methods. To investigate the utility of regional measures of scanner output, regional and organ anatomic boundaries were identified from image data and used to calculate regional and organ-specific average tube current values. From these regional and organ-specific averages, CTDI(vol) values, referred to as regional and organ-specific CTDI(vol), were calculated for each patient. Using an approach similar to TG 204, all CTDI(vol) values were used to normalize simulated organ doses; and the ability of each normalized dose to correlate with patient size was investigated. RESULTS For all five organs, the correlations with patient size increased when organ doses were normalized by regional and organ-specific CTDI(vol) values. For example, when estimating dose to the liver, CTDI(vol),global yielded a R(2) value of 0.26, which improved to 0.77 and 0.86, when using the regional and organ-specific CTDI(vol) for abdomen and liver, respectively. For breast dose, the global CTDI(vol) yielded a R(2) value of 0.08, which improved to 0.58 and 0.83, when using the regional and organ-specific CTDI(vol) for chest and breasts, respectively. The R(2) values also increased once the thoracic models were separated for the analysis into females and males, indicating differences between genders in this region not explained by a simple measure of effective diameter. CONCLUSIONS This work demonstrated the utility of regional and organ-specific CTDI(vol) as normalization factors when using TCM. It was demonstrated that CTDI(vol),global is not an effective normalization factor in TCM exams where attenuation (and therefore tube current) varies considerably throughout the scan, such as abdomen/pelvis and even thorax. These exams can be more accurately assessed for dose using regional CTDI(vol) descriptors that account for local variations in scanner output present when TCM is employed.
Collapse
Affiliation(s)
- Maryam Khatonabadi
- Department of Biomedical Physics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California 90024, USA.
| | | | | | | | | | | | | |
Collapse
|