101
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Lee WH, Nguyen PK, Fleischmann D, Wu JC. DNA damage-associated biomarkers in studying individual sensitivity to low-dose radiation from cardiovascular imaging. Eur Heart J 2016; 37:3075-3080. [PMID: 27272147 PMCID: PMC6279211 DOI: 10.1093/eurheartj/ehw206] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2015] [Revised: 04/10/2016] [Accepted: 05/04/2016] [Indexed: 12/29/2022] Open
Affiliation(s)
- Won Hee Lee
- Department of Medicine, Division of Cardiology
- Department of Radiology
- Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Patricia K Nguyen
- Department of Medicine, Division of Cardiology
- Department of Radiology
- Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Dominik Fleischmann
- Department of Radiology
- Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Joseph C Wu
- Department of Medicine, Division of Cardiology
- Department of Radiology
- Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA 94305, USA
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102
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Owens C, Li BK, Thomas KE, Irwin MS. Surveillance imaging and radiation exposure in the detection of relapsed neuroblastoma. Pediatr Blood Cancer 2016; 63:1786-93. [PMID: 27304424 DOI: 10.1002/pbc.26099] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Revised: 05/10/2016] [Accepted: 05/16/2016] [Indexed: 01/10/2023]
Abstract
BACKGROUND More than half of children with high-risk neuroblastoma (NB) will experience recurrence. Radiologic imaging is used for initial staging and during therapy to assess response. However, the role of surveillance imaging in the detection of relapse has not been well studied. Surveillance potentially results in high cumulative exposure to ionizing radiation, which may be associated with an increased risk of developing second malignancies. PROCEDURE We reviewed NB cases at our institution between 2000 and 2011. We calculated radiation exposure due to imaging (during diagnosis, treatment, and posttherapy surveillance) using cumulative effective dose (CED) estimates and determined whether cross-sectional imaging identified recurrences. RESULTS Fifty of 183 patients with NB experienced a recurrence. The median time from diagnosis to relapse was 1.20 years (range: 0.18-6.66 years). Most patients had evidence of metastases and only 4 of 50 patients presented with isolated primary tumor site recurrences. The mean CED prior to relapse was 125.2 mSv (range: 24.5-259.7), 64% of which was from computed tomography (CT) scans. Thirty-seven of 50 patients had clinically evident or measurable disease detected by X-ray (XR), ultrasound (US), or urinary catecholamines (UCats), and the addition of metaiodobenzylguanidine (MIBG) scans identified eight additional recurrences. Thus, cross-sectional imaging (CT/MRI, where MRI is magnetic resonance imaging) was only required to identify 10% (5/50) of cases. CONCLUSION Relapsed disease was detected in most patients by symptoms/exam, MIBG scan, UCats, and/or XR/US, supporting reduced use of CT imaging in posttherapy surveillance, thereby decreasing cumulative radiation dose. Refinement of surveillance imaging may be further guided by risk stratification, disease sites, and potentially biomolecular markers.
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Affiliation(s)
- Cormac Owens
- Division of Haematology-Oncology, Department of Paediatrics, Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada.,Department of Paediatric Haematology-Oncology, Our Lady's Children's Hospital, Dublin, Ireland
| | - Bryan K Li
- Division of Haematology-Oncology, Department of Paediatrics, Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada
| | - Karen E Thomas
- Department of Diagnostic Imaging, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Meredith S Irwin
- Division of Haematology-Oncology, Department of Paediatrics, Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada
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103
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Tootell A, McEntee M, Szczepura K, Hogg P. Effective Dose and Effective Risk from Post-Single Photon Emission Computed Tomography Imaging of the Lumbar Spine. J Med Imaging Radiat Sci 2016; 47:267-275. [PMID: 31047291 DOI: 10.1016/j.jmir.2016.04.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Revised: 04/20/2016] [Accepted: 04/25/2016] [Indexed: 10/21/2022]
Abstract
PURPOSE Planar bone scans play an important role in the staging and monitoring of malignancy and metastases. Metastases in the lumbar spine are associated with significant morbidity; therefore, accurate diagnosis is essential. Supplementary imaging after planar bone scans is often required to characterize lesions; however, this is associated with additional radiation dose. This article provides information on the comparative effective dose and effective risk from supplementary lumbar spine radiographs, low-dose computed tomography (LDCT), and diagnostic CT (DCT). METHOD Organ dose was measured in a phantom using thermoluminescent dosimeters. Effective dose and effective risk were calculated for radiographs, LDCT, and DCT imaging of the lumbar spine. RESULTS Radiation dose was 0.56 mSv for the anteroposterior and lateral lumbar spine radiographs, 0.80 mSv for LDCT, and 3.78 mSv for DCT. Additional imaging resulted in an increase in effective dose of 12.28%, 17.54%, and 82.89% for radiographs, LDCT, and DCT, respectively. Risk of cancer induction decreased as age increased. The difference in risk between the modalities also decreased. Males had a statistically significant higher risk than female patients (P = .023), attributed to the sensitive organs being closer to the exposed area. CONCLUSIONS Effective dose for LDCT is comparable with radiographs of the lumbar spine. With the known benefits of image fusion, it is recommended that LDCT replace radiograph imaging for characterization of lumbar spine lesions identified on planar bone scans. DCT is associated with significantly higher effective dose than LDCT. Effective risk is also higher, and the difference is more marked in younger female patients.
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Affiliation(s)
- Andrew Tootell
- Directorate of Radiography, Centre for Health Sciences Research, University of Salford, Salford, UK.
| | - Mark McEntee
- Faculty of Health Sciences, The University of Sydney, Sydney, New South Wales, Australia
| | - Katy Szczepura
- Directorate of Radiography, Centre for Health Sciences Research, University of Salford, Salford, UK
| | - Peter Hogg
- Directorate of Radiography, Centre for Health Sciences Research, University of Salford, Salford, UK
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104
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Mahesh M, Morin RL. CT Scans and Cancer Risks—A Practical Middle Path. J Am Coll Radiol 2016; 13:828-30. [DOI: 10.1016/j.jacr.2016.04.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Accepted: 04/09/2016] [Indexed: 11/26/2022]
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105
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Mattsson S. NEED FOR INDIVIDUAL CANCER RISK ESTIMATES IN X-RAY AND NUCLEAR MEDICINE IMAGING. RADIATION PROTECTION DOSIMETRY 2016; 169:11-16. [PMID: 26994092 DOI: 10.1093/rpd/ncw034] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
To facilitate the justification of an X-ray or nuclear medicine investigation and for informing patients, it is desirable that the individual patient's radiation dose and potential cancer risk can be prospectively assessed and documented. The current dose-reporting is based on effective dose, which ignores body size and does not reflect the strong dependence of risk on the age at exposure. Risk estimations should better be done through individual organ dose assessments, which need careful exposure characterisation as well as anatomical description of the individual patient. In nuclear medicine, reference biokinetic models should also be replaced with models describing individual physiological states and biokinetics. There is a need to adjust population-based cancer risk estimates to the possible risk of leukaemia and solid tumours for the individual depending on age and gender. The article summarises reasons for individual cancer risk estimates and gives examples of methods and results of such estimates.
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Affiliation(s)
- Sören Mattsson
- Medical Radiation Physics Malmö, Department of Translational Medicine, Lund University, Malmö, Sweden
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106
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Harrison JD, Balonov M, Martin CJ, Ortiz Lopez P, Menzel HG, Simmonds JR, Smith-Bindman R, Wakeford R. Use of effective dose. Ann ICRP 2016; 45:215-224. [PMID: 26980800 DOI: 10.1177/0146645316634566] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
International Commission on Radiological Protection (ICRP) Publication 103 provided a detailed explanation of the purpose and use of effective dose and equivalent dose to individual organs and tissues. Effective dose has proven to be a valuable and robust quantity for use in the implementation of protection principles. However, questions have arisen regarding practical applications, and a Task Group has been set up to consider issues of concern. This paper focusses on two key proposals developed by the Task Group that are under consideration by ICRP: (1) confusion will be avoided if equivalent dose is no longer used as a protection quantity, but regarded as an intermediate step in the calculation of effective dose. It would be more appropriate for limits for the avoidance of deterministic effects to the hands and feet, lens of the eye, and skin, to be set in terms of the quantity, absorbed dose (Gy) rather than equivalent dose (Sv). (2) Effective dose is in widespread use in medical practice as a measure of risk, thereby going beyond its intended purpose. While doses incurred at low levels of exposure may be measured or assessed with reasonable reliability, health effects have not been demonstrated reliably at such levels but are inferred. However, bearing in mind the uncertainties associated with risk projection to low doses or low dose rates, it may be considered reasonable to use effective dose as a rough indicator of possible risk, with the additional consideration of variation in risk with age, sex and population group.
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Affiliation(s)
- J D Harrison
- Oxford Brookes University, Faculty of Health and Life Sciences, Oxford OX3 0BP, UK
| | - M Balonov
- St. Petersburg Institute of Radiation Hygiene, Russia
| | | | | | - H-G Menzel
- European Organisation for Nuclear Research, Switzerland
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107
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Martin CJ, Abuhaimed A, Sankaralingam M, Metwaly M, Gentle DJ. Organ doses can be estimated from the computed tomography (CT) dose index for cone-beam CT on radiotherapy equipment. JOURNAL OF RADIOLOGICAL PROTECTION : OFFICIAL JOURNAL OF THE SOCIETY FOR RADIOLOGICAL PROTECTION 2016; 36:215-229. [PMID: 26975735 DOI: 10.1088/0952-4746/36/2/215] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Cone beam computed tomography (CBCT) systems are fitted to radiotherapy linear accelerators and used for patient positioning prior to treatment by image guided radiotherapy (IGRT). Radiotherapists' and radiographers' knowledge of doses to organs from CBCT imaging is limited. The weighted CT dose index for a reference beam of width 20 mm (CTDIw,ref) is displayed on Varian CBCT imaging equipment known as an On-Board Imager (OBI) linked to the Truebeam linear accelerator. This has the potential to provide an indication of organ doses. This knowledge would be helpful for guidance of radiotherapy clinicians preparing treatments. Monte Carlo simulations of imaging protocols for head, thorax and pelvic scans have been performed using EGSnrc/BEAMnrc, EGSnrc/DOSXYZnrc, and ICRP reference computational male and female phantoms to derive the mean absorbed doses to organs and tissues, which have been compared with values for the CTDIw,ref displayed on the CBCT scanner console. Substantial variations in dose were observed between male and female phantoms. Nevertheless, the CTDIw,ref gave doses within ±21% for the stomach and liver in thorax scans and 2 × CTDIw,ref can be used as a measure of doses to breast, lung and oesophagus. The CTDIw,ref could provide indications of doses to the brain for head scans, and the colon for pelvic scans. It is proposed that knowledge of the link between CTDIw for CBCT should be promoted and included in the training of radiotherapy staff.
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Affiliation(s)
- Colin J Martin
- Department of Clinical Physics, University of Glasgow, Glasgow, UK
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108
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Saltybaeva N, Martini K, Frauenfelder T, Alkadhi H. Organ Dose and Attributable Cancer Risk in Lung Cancer Screening with Low-Dose Computed Tomography. PLoS One 2016; 11:e0155722. [PMID: 27203720 PMCID: PMC4874690 DOI: 10.1371/journal.pone.0155722] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Accepted: 05/03/2016] [Indexed: 12/18/2022] Open
Abstract
Purpose Lung cancer screening with CT has been recently recommended for decreasing lung cancer mortality. The radiation dose of CT, however, must be kept as low as reasonably achievable for reducing potential stochastic risks from ionizing radiation. The purpose of this study was to calculate individual patients’ lung doses and to estimate cancer risks in low-dose CT (LDCT) in comparison with a standard dose CT (SDCT) protocol. Materials and Methods This study included 47 adult patients (mean age 63.0 ± 5.7 years) undergoing chest CT on a third-generation dual-source scanner. 23/47 patients (49%) had a non-enhanced chest SDCT, 24 patients (51%) underwent LDCT at 100 kVp with spectral shaping at a dose equivalent to a chest x-ray. 3D-dose distributions were obtained from Monte Carlo simulations for each patient, taking into account their body size and individual CT protocol. Based on the dose distributions, patient-specific lung doses were calculated and relative cancer risk was estimated according to BEIR VII recommendations. Results As compared to SDCT, the LDCT protocol allowed for significant organ dose and cancer risk reductions (p<0.001). On average, lung dose was reduced from 7.7 mGy to 0.3 mGy when using LDCT, which was associated with lowering of the cancer risk from 8.6 to 0.35 per 100’000 cases. A strong linear correlation between lung dose and patient effective diameter was found for both protocols (R2 = 0.72 and R2 = 0.75 for SDCT and LDCT, respectively). Conclusion Use of a LDCT protocol for chest CT with a dose equivalent to a chest x-ray allows for significant lung dose and cancer risk reduction from ionizing radiation.
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Affiliation(s)
- Natalia Saltybaeva
- Institute for Diagnostic and Interventional Radiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
- * E-mail:
| | - Katharina Martini
- Institute for Diagnostic and Interventional Radiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Thomas Frauenfelder
- Institute for Diagnostic and Interventional Radiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Hatem Alkadhi
- Institute for Diagnostic and Interventional Radiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
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109
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Costa PR, Yoshimura EM, Nersissian DY, Melo CS. Correlation between effective dose and radiological risk: general concepts. Radiol Bras 2016; 49:176-81. [PMID: 27403018 PMCID: PMC4938448 DOI: 10.1590/0100-3984.2014.0097] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Accepted: 05/12/2015] [Indexed: 11/21/2022] Open
Abstract
The present review aims to offer an educational approach related to the limitations in the use of the effective dose mgnitude as a tool for the quantification of doses resulting from diagnostic applications of ionizing radiation. We present a critical analysis of the quantities accepted and currently used for dosimetric evaluation in diagnostic imaging procedures, based on studies published in the literature. It is highlighted the use of these quantities to evaluate the risk attributed to the procedure and to calculate the effective dose, as well as to determine its correct use and interpretation.
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Affiliation(s)
- Paulo Roberto Costa
- PhD, Professor at the Instituto de Física da
Universidade de São Paulo (IFUSP), São Paulo, SP, Brazil
| | - Elisabeth Mateus Yoshimura
- PhD, Full Professor at the Instituto de Física da
Universidade de São Paulo (IFUSP), São Paulo, SP, Brazil
| | | | - Camila Souza Melo
- Specialist in Physics of Diagnostic Radiology, Physicist
at the Instituto de Física da Universidade de São Paulo (IFUSP),
São Paulo, SP, Brazil
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110
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Alshamari M, Geijer M, Norrman E, Lidén M, Krauss W, Wilamowski F, Geijer H. Low dose CT of the lumbar spine compared with radiography: a study on image quality with implications for clinical practice. Acta Radiol 2016. [PMID: 26221055 DOI: 10.1177/0284185115595667] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Lumbar spine radiography is often performed instead of CT for radiation dose concerns. PURPOSE To compare image quality and diagnostic information from low dose lumbar spine CT at an effective dose of about 1 mSv with lumbar spine radiography. MATERIAL AND METHODS Fifty-one patients were examined by both methods. Five reviewers scored all examinations on eight image quality criteria using a five-graded scale and also assessed three common pathologic changes. RESULTS Low dose CT scored better than radiography on the following: sharp reproduction of disc profile and vertebral end-plates (odds ratio [OR], 1.8; 95% confidence interval [CI], 1.3-2.5), intervertebral foramina and pedicles (OR, 4.3; 95% CI, 3.1-5.9), intervertebral joints (OR, 139; 95% CI, 59-326), spinous and transverse processes (OR, 7.0; 95% CI, 4.3-11.2), sacro-iliac joints (OR, 4.2; 95% CI, 3.2-5.7), reproduction of the adjacent soft tissues (OR, 2.9; 95% CI, 2.1-4.0), and absence of any obscuring superimposed gastrointestinal gas and contents (OR, 188; 95% CI, 66-539). Radiography scored better on sharp reproduction of cortical and trabecular bone (OR, 0.3; 95% CI, 0.2-0.4). The reviewers visualized disk degeneration, spondylosis/diffuse idiopathic skeletal hyperostosis (DISH) and intervertebral joint osteoarthritis more clearly and were more certain with low dose CT. Mean time to review low dose CT was 204 s (95% CI, 194-214 s.), radiography 152 s (95% CI, 146-158 s.). The effective dose for low dose CT was 1.0-1.1 mSv, for radiography 0.7 mSv. CONCLUSION Low dose lumbar spine CT at about 1 mSv has superior image quality to lumbar spine radiography with more anatomical and diagnostic information.
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Affiliation(s)
- Muhammed Alshamari
- Department of Radiology, Faculty of Medicine and Health, Örebro University, Örebro, Sweden
| | - Mats Geijer
- Department of Medical Imaging and Physiology, Skåne University Hospital, Lund, Lund University, Sweden
| | - Eva Norrman
- Department of Medical Physics, Faculty of Medicine and Health, Örebro University, Örebro, Sweden
| | - Mats Lidén
- Department of Radiology, Faculty of Medicine and Health, Örebro University, Örebro, Sweden
| | - Wolfgang Krauss
- Department of Radiology, Faculty of Medicine and Health, Örebro University, Örebro, Sweden
| | - Franciszek Wilamowski
- Department of Radiology, Faculty of Medicine and Health, Örebro University, Örebro, Sweden
| | - Håkan Geijer
- Department of Radiology, Faculty of Medicine and Health, Örebro University, Örebro, Sweden
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111
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Grüning T, Mingo RE, Gosling MG, Farrell SL, Drake BE, Loader RJ, Riordan RD. Diagnosing venous thromboembolism in pregnancy. Br J Radiol 2016; 89:20160021. [PMID: 27055494 DOI: 10.1259/bjr.20160021] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVE We report the imaging outcomes of all pregnant patients referred for suspected thromboembolism over a 43-month period. METHODS We identified 168 patients who underwent ventilation/perfusion (VQ) single-photon emission CT (SPECT), CT pulmonary angiography (CTPA) or a Doppler ultrasound scan of the lower legs, as well as a control group of 89 non-pregnant age- and sex-matched patients who underwent VQ SPECT during the same period. Imaging outcomes were recorded, and radiation doses were calculated for individual patients. RESULTS VQ SPECT and CTPA were equally likely to diagnose pulmonary embolism (PE) in about one patient out of every seven patients investigated. One in three CTPA scans was of suboptimal quality. A Doppler ultrasound examination of the legs will find deep venous thrombosis much less often, in about 1 patient out of every 15 patients investigated. The prevalence of PE in pregnant patients (as diagnosed by VQ SPECT) was similar to that in the non-pregnant, age- and sex-matched control group. The effective dose and the absorbed radiation dose to the maternal breast were lower with VQ SPECT. The foetal dose is comparable for both VQ SPECT and CTPA. CONCLUSION VQ SPECT and CTPA provide a similar diagnostic yield for diagnosing PE during pregnancy, but VQ SPECT does so with a lower radiation dose to the mother (effective dose and breast dose). ADVANCES IN KNOWLEDGE Ours is the first report of the diagnostic performance of VQ SPECT, rather than planar VQ scans, in pregnancy in a routine clinical setting.
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Affiliation(s)
- Thomas Grüning
- 1 Department of Nuclear Medicine, Derriford Hospital, Plymouth, UK
| | - Rebecca E Mingo
- 1 Department of Nuclear Medicine, Derriford Hospital, Plymouth, UK
| | - Matthew G Gosling
- 2 Department of Clinical and Radiation Physics, Derriford Hospital, Plymouth, UK
| | - Sally L Farrell
- 1 Department of Nuclear Medicine, Derriford Hospital, Plymouth, UK
| | - Brent E Drake
- 1 Department of Nuclear Medicine, Derriford Hospital, Plymouth, UK
| | - Robert J Loader
- 2 Department of Clinical and Radiation Physics, Derriford Hospital, Plymouth, UK
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112
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Cumulative radiation exposure and estimated lifetime cancer risk in multiple-injury adult patients undergoing repeated or multiple CTs. Eur J Trauma Emerg Surg 2016; 44:19-27. [DOI: 10.1007/s00068-016-0665-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 03/14/2016] [Indexed: 10/22/2022]
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113
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Sookpeng S, Martin CJ, Gentle DJ. Influence of CT automatic tube current modulation on uncertainty in effective dose. RADIATION PROTECTION DOSIMETRY 2016; 168:46-54. [PMID: 25628455 DOI: 10.1093/rpd/ncu374] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 12/29/2014] [Indexed: 06/04/2023]
Abstract
Computed tomography (CT) scanners are equipped with automatic tube current modulation (ATCM) systems that adjust the current to compensate for variations in patient attenuation. CT dosimetry variables are not defined for ATCM situations and, thus, only the averaged values are displayed and analysed. The patient effective dose (E), which is derived from a weighted sum of organ equivalent doses, will be modified by the ATCM. Values for E for chest-abdomen-pelvis CT scans have been calculated using the ImPACT spreadsheet for patients on five CT scanners. Values for E resulting from the z-axis modulation under ATCM have been compared with results assessed using the same effective mAs values with constant tube currents. Mean values for E under ATCM were within ±10 % of those for fixed tube currents for all scanners. Cumulative dose distributions under ATCM have been simulated for two patient scans using single-slice dose profiles measured in elliptical and cylindrical phantoms on one scanner. Contributions to the effective dose from organs in the upper thorax under ATCM are 30-35 % lower for superficial tissues (e.g. breast) and 15-20 % lower for deeper organs (e.g. lungs). The effect on doses to organs in the abdomen depends on body shape, and they can be 10-22 % higher for larger patients. Results indicate that scan dosimetry parameters, dose-length product and effective mAs averaged over the whole scan can provide an assessment in terms of E that is sufficiently accurate to quantify relative risk for routine patient exposures under ATCM.
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Affiliation(s)
- S Sookpeng
- Department of Radiological Technology, Faculty of Allied Health Sciences, Naresuan University, Phitsanulok 65000, Thailand
| | - C J Martin
- Department of Clinical Physics, University of Glasgow, Glasgow G12 8QQ, UK
| | - D J Gentle
- Health Physics, Gartnavel Royal Hospital, 1055 Great Western Road, Glasgow G12 0XH, UK
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114
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Hoogeveen RC, Martens EP, van der Stelt PF, Berkhout WER. Assessment of Random Error in Phantom Dosimetry with the Use of Error Simulation in Statistical Software. BIOMED RESEARCH INTERNATIONAL 2015; 2015:596858. [PMID: 26881200 PMCID: PMC4736220 DOI: 10.1155/2015/596858] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/04/2015] [Accepted: 12/14/2015] [Indexed: 11/30/2022]
Abstract
OBJECTIVE To investigate if software simulation is practical for quantifying random error (RE) in phantom dosimetry. MATERIALS AND METHODS We applied software error simulation to an existing dosimetry study. The specifications and the measurement values of this study were brought into the software (R version 3.0.2) together with the algorithm of the calculation of the effective dose (E). Four sources of RE were specified: (1) the calibration factor; (2) the background radiation correction; (3) the read-out process of the dosimeters; and (4) the fluctuation of the X-ray generator. RESULTS The amount of RE introduced by these sources was calculated on the basis of the experimental values and the mathematical rules of error propagation. The software repeated the calculations of E multiple times (n = 10,000) while attributing the applicable RE to the experimental values. A distribution of E emerged as a confidence interval around an expected value. CONCLUSIONS Credible confidence intervals around E in phantom dose studies can be calculated by using software modelling of the experiment. With credible confidence intervals, the statistical significance of differences between protocols can be substantiated or rejected. This modelling software can also be used for a power analysis when planning phantom dose experiments.
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Affiliation(s)
- R. C. Hoogeveen
- Department of Oral and Maxillofacial Radiology, Academic Center for Dentistry Amsterdam (ACTA), Gustav Mahlerlaan 3004, 1081 LA Amsterdam, Netherlands
| | - E. P. Martens
- Statisticor, Statistical Research Office, Dorpsstraat 90, 2831 AT Gouderak, Netherlands
| | - P. F. van der Stelt
- Department of Oral and Maxillofacial Radiology, Academic Center for Dentistry Amsterdam (ACTA), Gustav Mahlerlaan 3004, 1081 LA Amsterdam, Netherlands
| | - W. E. R. Berkhout
- Department of Oral and Maxillofacial Radiology, Academic Center for Dentistry Amsterdam (ACTA), Gustav Mahlerlaan 3004, 1081 LA Amsterdam, Netherlands
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115
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Strindberg JE, Hol C, Torgersen G, Møystad A, Nilsson M, Näsström K, Hellén-Halme K. Comparison of Swedish and Norwegian Use of Cone-Beam Computed Tomography: a Questionnaire Study. EJOURNAL OF ORAL MAXILLOFACIAL RESEARCH 2015; 6:e2. [PMID: 26904179 PMCID: PMC4761432 DOI: 10.5037/jomr.2015.6402] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 12/23/2015] [Indexed: 12/19/2022]
Abstract
Objectives Cone-beam computed tomography in dentistry can be used in some countries by other dentists than specialists in radiology. The frequency of buying cone-beam computed tomography to examine patients is rapidly growing, thus knowledge of how to use it is very important. The aim was to compare the outcome of an investigation on the use of cone-beam computed tomography in Sweden with a previous Norwegian study, regarding specifically technical aspects. Material and Methods The questionnaire contained 45 questions, including 35 comparable questions to Norwegian clinics one year previous. Results were based on inter-comparison of the outcome from each of the two questionnaire studies. Results Responses rate was 71% in Sweden. There, most of cone-beam computed tomography (CBCT) examinations performed by dental nurses, while in Norway by specialists. More than two-thirds of the CBCT units had a scout image function, regularly used in both Sweden (79%) and Norway (75%). In Sweden 4% and in Norway 41% of the respondents did not wait for the report from the radiographic specialist before initiating treatment. Conclusions The bilateral comparison showed an overall similarity between the two countries. The survey gave explicit and important knowledge of the need for education and training of the whole team, since radiation dose to the patient could vary a lot for the same kind of radiographic examination. It is essential to establish quality assurance protocols with defined responsibilities in the team in order to maintain high diagnostic accuracy for all examinations when using cone-beam computed tomography for patient examinations.
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Affiliation(s)
- Jerker Edén Strindberg
- Division of Image and Functional Odontology, Department of Dental Medicine, Karolinska Institute, StockholmSweden.; Department of Hospital Physics, Danderyd Hospital, StockholmSweden
| | - Caroline Hol
- Oral Health Centre of Expertise in Southern Norway, Arendal Norway
| | - Gerald Torgersen
- Department of Maxillofacial Radiology, Institute of Clinical Odontology, Faculty of Dentistry, University of Oslo, Oslo, Norway
| | - Anne Møystad
- Department of Maxillofacial Radiology, Institute of Clinical Odontology, Faculty of Dentistry, University of Oslo, Oslo, Norway
| | - Mats Nilsson
- Division of Image and Functional Odontology, Department of Dental Medicine, Karolinska Institute, StockholmSweden.; Department of Hospital Physics, Danderyd Hospital, StockholmSweden
| | - Karin Näsström
- Division of Image and Functional Odontology, Department of Dental Medicine, Karolinska Institute, StockholmSweden.; Department of Hospital Physics, Danderyd Hospital, StockholmSweden
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Matsunaga Y, Kawaguchi A, Kobayashi K, Kobayashi M, Asada Y, Minami K, Suzuki S, Chida K. Effective radiation doses of CT examinations in Japan: a nationwide questionnaire-based study. Br J Radiol 2015; 89:20150671. [PMID: 26647804 PMCID: PMC4985214 DOI: 10.1259/bjr.20150671] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Revised: 11/28/2015] [Accepted: 12/07/2015] [Indexed: 02/01/2023] Open
Abstract
OBJECTIVE The aims of this study were to estimate the effective radiation doses from CT examinations of both adults and children in Japan and to study the impact of various scan parameters on the effective doses. METHODS A questionnaire, which contained detailed questions on the CT scan parameters employed, was distributed to 3000 facilities throughout Japan. For each scanner protocol, the effective doses for head (non-helical and helical), chest and upper abdomen acquisitions were estimated using ImPACT CT Patient Dosimetry Calculator software v. 1.0.4 (St George's Hospital, London, UK). RESULTS The mean effective doses for chest and abdominal examinations using 80-110 kV were significantly lower than those using 120 kV. However, there was no statistically significant difference in the mean effective doses for head scans between facilities employing 80-110 kV and 120 kV. In chest and abdominal examinations, the mean effective doses using CT scanners from Western manufacturers [Siemens (Forchheim, Germany), Philips (Eindhoven, Netherlands) and GE Medical Systems (Milwaukee, WI)] were significantly lower than those of examinations using Japanese scanners [Hitachi (Kashiwa, Japan) and Toshiba (Otawara, Tochigi, Japan)], except for in paediatric chest examinations. CONCLUSION The mean effective doses for adult head, chest and abdominal CT examinations were 2.9, 7.7 and 10.0 mSv, respectively, whereas the corresponding mean effective doses for paediatric examinations were 2.6, 7.1 and 7.7 mSv, respectively. ADVANCES IN KNOWLEDGE Facilities using CT scanners by Western manufacturers commonly adopt low-tube-voltage techniques, and low-tube-voltage CT may be useful for reducing the radiation doses to the patients, particularly for the body region.
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Affiliation(s)
- Yuta Matsunaga
- Department of Imaging, Nagoya Kyoritsu Hospital, Nagoya, Japan
- Graduate School of Medicine, Tohoku University, Sendai, Japan
| | - Ai Kawaguchi
- Graduate School of Medicine, Tohoku University, Sendai, Japan
- Department of Radiology, Toyota Memorial Hospital, Toyota, Japan
| | - Kenichi Kobayashi
- Department of Radiology, Fujita Health University Hospital, Toyoake, Japan
| | | | - Yasuki Asada
- School of Health Sciences, Fujita Health University, Toyoake, Japan
| | - Kazuyuki Minami
- School of Health Sciences, Fujita Health University, Toyoake, Japan
| | - Shoichi Suzuki
- School of Health Sciences, Fujita Health University, Toyoake, Japan
| | - Koichi Chida
- Graduate School of Medicine, Tohoku University, Sendai, Japan
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Shrimpton PC, Jansen JTM, Harrison JD. Updated estimates of typical effective doses for common CT examinations in the UK following the 2011 national review. Br J Radiol 2015; 89:20150346. [PMID: 26544160 PMCID: PMC4985946 DOI: 10.1259/bjr.20150346] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Revised: 10/23/2015] [Accepted: 11/04/2015] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVE To investigate the impact of evolving International Commission on Radiological Protection (ICRP) recommendations concerning calculation of effective dose (E) and compare updated typical UK values for common CT examinations with previous data. METHODS Monte Carlo simulations have provided normalized organ doses relating to 15 CT scanner models and 5 virtual reference adults. Series of representative E/dose-length product (DLP) coefficients were derived for common examinations on the separate bases of not only older stylized mathematical phantoms and voxel phantoms presently recommended by ICRP, but also the 1977, 1990 and 2007 formulations for E. Updated E/DLP coefficients were applied to typical values of DLP from the 2011 UK survey. RESULTS Changes in ICRP recommendations that have arisen from improving evidence on stochastic risk, influence values of E by up to a factor two for CT examinations of the head and neck, although differences for the trunk typically amount to ±10%. Adoption of the voxel rather than the mathematical phantoms used previously can lead to further changes in E by a few tens of percent. Updated typical values of E for UK CT examinations range from 2 to 20 mSv. Increases by 20-400% since 2003 arise not only from increases by 30-160% in typical values of DLP, but also increases by 30-90% in relation to E/DLP coefficients for examinations of the trunk. CONCLUSION Values of E, including updated typical data for UK CT, should be compared with caution in relation to their purpose and underlying factors concerning their calculation. ADVANCES IN KNOWLEDGE Updated E/DLP coefficients and typical values of E for UK CT, and an appreciation of factors influencing these data.
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Affiliation(s)
- Paul C Shrimpton
- Public Health England, Centre for Radiation, Chemical and Environmental Hazards, Chilton, UK
| | - Jan T M Jansen
- Public Health England, Centre for Radiation, Chemical and Environmental Hazards, Chilton, UK
| | - John D Harrison
- Public Health England, Centre for Radiation, Chemical and Environmental Hazards, Chilton, UK
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Size-Specific Dose Estimates for Evaluation of Individual Patient Dose in CT Protocol for Renal Colic. AJR Am J Roentgenol 2015; 205:100-5. [PMID: 26102387 DOI: 10.2214/ajr.14.13573] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
OBJECTIVE The purpose of this study is to retrospectively evaluate size-specific dose estimates of a renal-colic CT protocol and to assess the quality and diagnostic value of obtained images. MATERIALS AND METHODS The study population included 82 consecutive adult patients with acute renal colic undergoing CT with a reduced radiation dose (noise index, 59.1). The control group included 82 consecutive patients who underwent clinically indicated CT examination of the abdomen and pelvis with a routine-dose CT protocol (noise index, 22.0). The size-specific dose estimate was calculated with volume CT dose index and patient effective diameter. Subjective image quality analysis was based on visibility of the ureter. Ureters were tracked from the renal pelvis to the vesicoureteral junction. Objective image quality was based on the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR). RESULTS The size-specific dose estimates in the renal-colic group were 2.7 times lower than those in the control group. A linear relationship between patient size and size-specific dose estimate was noted. In the smallest patient, the conversion factor for the size-specific dose estimate calculation was 1.65. Overall image quality was better for the control patients, but there was no statistically significant difference in ureter visibility. The SNR was higher for the control group, whereas no difference in CNR was found. CONCLUSION Small patients need the biggest correction for body size and require special attention in radiation dose estimation. We suggest the modification of scanning parameters on the basis of size-specific dose estimate to decrease patient dose in large patients.
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Ludlow JB, Timothy R, Walker C, Hunter R, Benavides E, Samuelson DB, Scheske MJ. Effective dose of dental CBCT-a meta analysis of published data and additional data for nine CBCT units. Dentomaxillofac Radiol 2015; 44:20140197. [PMID: 25224586 DOI: 10.1259/dmfr.20140197] [Citation(s) in RCA: 273] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
OBJECTIVES This article analyses dose measurement and effective dose estimation of dental CBCT examinations. Challenges to accurate calculation of dose are discussed and the use of dose-height product (DHP) as an alternative to dose-area product (DAP) is explored. METHODS The English literature on effective dose was reviewed. Data from these studies together with additional data for nine CBCT units were analysed. Descriptive statistics, ANOVA and paired analysis are used to characterize the data. RESULTS PubMed and EMBASE searches yielded 519 and 743 publications, respectively, which were reduced to 20 following review. Reported adult effective doses for any protocol ranged from 46 to 1073 µSv for large fields of view (FOVs), 9-560 µSv for medium FOVs and 5-652 µSv for small FOVs. Child effective doses from any protocol ranged from 13 to 769 µSv for large or medium FOVs and 7-521 µSv for small FOVs. Effective doses from standard or default exposure protocols were available for 167 adult and 52 child exposures. Mean adult effective doses grouped by FOV size were 212 µSv (large), 177 µSv (medium) and 84 µSv (small). Mean child doses were 175 µSv (combined large and medium) and 103 µSv (small). Large differences were seen between different CBCT units. Additional low-dose and high-definition protocols available for many units extend the range of doses. DHP was found to reduce average absolute error for calculation of dose by 45% in comparison with DAP. CONCLUSIONS Large exposure ranges make CBCT doses difficult to generalize. Use of DHP as a metric for estimating effective dose warrants further investigation.
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Affiliation(s)
- J B Ludlow
- 1 North Carolina Oral Health Institute, Koury Oral Health Sciences, Chapel Hill, NC, USA
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Lee E, Goo HW, Lee JY. Age- and gender-specific estimates of cumulative CT dose over 5 years using real radiation dose tracking data in children. Pediatr Radiol 2015; 45:1282-92. [PMID: 25801905 DOI: 10.1007/s00247-015-3331-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 01/23/2015] [Accepted: 02/24/2015] [Indexed: 10/24/2022]
Abstract
BACKGROUND It is necessary to develop a mechanism to estimate and analyze cumulative radiation risks from multiple CT exams in various clinical scenarios in children. OBJECTIVE To identify major contributors to high cumulative CT dose estimates using actual dose-length product values collected for 5 years in children. MATERIALS AND METHODS Between August 2006 and July 2011 we reviewed 26,937 CT exams in 13,803 children. Among them, we included 931 children (median age 3.5 years, age range 0 days-15 years; M:F = 533:398) who had 5,339 CT exams. Each child underwent at least three CT scans and had accessible radiation dose reports. Dose-length product values were automatically extracted from DICOM files and we used recently updated conversion factors for age, gender, anatomical region and tube voltage to estimate CT radiation dose. We tracked the calculated CT dose estimates to obtain a 5-year cumulative value for each child. The study population was divided into three groups according to the cumulative CT dose estimates: high, ≥30 mSv; moderate, 10-30 mSv; and low, <10 mSv. We reviewed clinical data and CT protocols to identify major contributors to high and moderate cumulative CT dose estimates. RESULTS Median cumulative CT dose estimate was 5.4 mSv (range 0.5-71.1 mSv), and median number of CT scans was 4 (range 3-36). High cumulative CT dose estimates were most common in children with malignant tumors (57.9%, 11/19). High frequency of CT scans was attributed to high cumulative CT dose estimates in children with ventriculoperitoneal shunt (35 in 1 child) and malignant tumors (range 18-49). Moreover, high-dose CT protocols, such as multiphase abdomen CT (median 4.7 mSv) contributed to high cumulative CT dose estimates even in children with a low number of CT scans. CONCLUSION Disease group, number of CT scans, and high-dose CT protocols are major contributors to higher cumulative CT dose estimates in children.
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Affiliation(s)
- Eunsol Lee
- Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, 88, Olympic-ro 43-gil, Songpa-gu, Seoul, 138-736, Korea
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Hoogeveen RC, Sanderink GCH, van der Stelt PF, Berkhout WER. Reducing an already low dental diagnostic X-ray dose: does it make sense? Comparison of three cost-utility analysis methods used to assess two dental dose-reduction measures. Dentomaxillofac Radiol 2015; 44:20150158. [PMID: 26119214 PMCID: PMC5083903 DOI: 10.1259/dmfr.20150158] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2015] [Revised: 06/11/2015] [Accepted: 06/24/2015] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVES To find a method that is suitable for providing an objective assessment of the cost effectiveness of a dose-reducing measure used for diagnostic dental X-ray exposures. METHODS Three cost-utility analysis (CUA) methods were evaluated by comparing their assessments of two dose-reduction measures, a rectangular collimator and the combination of two devices that reduce the radiation dose received during orthodontic lateral cephalography. The following CUA methods were used: (1) the alpha value (AV), a monetary valuation of dose reduction used in the nuclear industry; (2) the value of a statistical life for valuation of the reduction in stochastic adverse effects; and (3) the time-for-time method, based on the postulate that risk reduction is effective when the number of years of life gained is more than the years that an average worker must work to earn the costs of the risk-reducing measure. The CUA methods were used to determine the minimum number of uses that was required for the dose-reducing device to be cost effective. The methods were assessed for coherence (are comparable results achieved for comparable countries?) and adaptability (can the method be adjusted for age and gender of specific patient groups?). RESULTS The performance of the time-for-time method was superior to the other methods. Both types of dose-reduction devices tested were assessed as cost effective after a realistic number of uses with all three methods except low AVs. CONCLUSIONS CUA for the methods of X-ray dose reduction can be performed to determine if investment in low dose reduction is cost effective. The time-for-time method proved to be a coherent and versatile method for performing CUA.
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Affiliation(s)
- R C Hoogeveen
- Academic Center for Dentistry Amsterdam ACTA, Department of Oral and
Maxillofacial Radiology, Amsterdam, Netherlands
| | - G C H Sanderink
- Academic Center for Dentistry Amsterdam ACTA, Department of Oral and
Maxillofacial Radiology, Amsterdam, Netherlands
| | - P F van der Stelt
- Academic Center for Dentistry Amsterdam ACTA, Department of Oral and
Maxillofacial Radiology, Amsterdam, Netherlands
| | - W E R Berkhout
- Academic Center for Dentistry Amsterdam ACTA, Department of Oral and
Maxillofacial Radiology, Amsterdam, Netherlands
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Pauwels R. Cone beam CT for dental and maxillofacial imaging: dose matters. RADIATION PROTECTION DOSIMETRY 2015; 165:156-161. [PMID: 25805884 DOI: 10.1093/rpd/ncv057] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The widespread use of cone-beam CT (CBCT) in dentistry has led to increasing concern regarding justification and optimisation of CBCT exposures. When used as a substitute to multidetector CT (MDCT), CBCT can lead to significant dose reduction; however, low-dose protocols of current-generation MDCTs show that there is an overlap between CBCT and MDCT doses. More importantly, although the 3D information provided by CBCT can often lead to improved diagnosis and treatment compared with 2D radiographs, a routine or excessive use of CBCT would lead to a substantial increase of the collective patient dose. The potential use of CBCT for paediatric patients (e.g. developmental disorders, trauma and orthodontic treatment planning) further increases concern regarding its proper application. This paper provides an overview of justification and optimisation issues in dental and maxillofacial CBCT. The radiation dose in CBCT will be briefly reviewed. The European Commission's Evidence Based Guidelines prepared by the SEDENTEXCT Project Consortium will be summarised, and (in)appropriate use of CBCT will be illustrated for various dental applications.
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Affiliation(s)
- Ruben Pauwels
- Department of Radiology, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand
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Balonov M, Golikov V, Kalnitsky S, Zvonova I, Chipiga L, Sarycheva S, Shatskiy I, Vodovatov A. Russian practical guidance on radiological support for justification of X-ray and nuclear medicine examinations. RADIATION PROTECTION DOSIMETRY 2015; 165:39-42. [PMID: 25862538 DOI: 10.1093/rpd/ncv127] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
An important part of the justification process is assessment of the radiation risks caused by exposure of a patient during examination. The authors developed official national methodology both for medical doctors and sanitary inspectors called 'assessment of radiation risks of patients undergoing diagnostic examinations with the use of ionizing radiation'. The document addresses patients of various age groups and a wide spectrum of modern X-ray and nuclear medicine examinations. International scale of risk categorisation was implemented by the use of effective dose with account for age dependence of radiation risk. The survey of effective doses in radiology, including CT, mammography, and intervention radiology, and nuclear medicine, including single-photon emission tomography and positron emission tomography, for patients of various age groups from several regions of Russia was used for the risk assessment. The output of the methodology is a series of tables for each diagnostic technology with lists of examinations for three age groups (children/adolescents, adults and seniors) corresponding to various radiation risk categories.
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Affiliation(s)
- M Balonov
- Research Institute of Radiation Hygiene, Mira St. 8, St. Petersburg 197046, Russian Federation
| | - V Golikov
- Research Institute of Radiation Hygiene, Mira St. 8, St. Petersburg 197046, Russian Federation
| | - S Kalnitsky
- Research Institute of Radiation Hygiene, Mira St. 8, St. Petersburg 197046, Russian Federation
| | - I Zvonova
- Research Institute of Radiation Hygiene, Mira St. 8, St. Petersburg 197046, Russian Federation
| | - L Chipiga
- Research Institute of Radiation Hygiene, Mira St. 8, St. Petersburg 197046, Russian Federation
| | - S Sarycheva
- Research Institute of Radiation Hygiene, Mira St. 8, St. Petersburg 197046, Russian Federation
| | - I Shatskiy
- Research Institute of Radiation Hygiene, Mira St. 8, St. Petersburg 197046, Russian Federation
| | - A Vodovatov
- Research Institute of Radiation Hygiene, Mira St. 8, St. Petersburg 197046, Russian Federation
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Xie T, Lee C, Bolch WE, Zaidi H. Assessment of radiation dose in nuclear cardiovascular imaging using realistic computational models. Med Phys 2015; 42:2955-66. [PMID: 26127049 PMCID: PMC5148206 DOI: 10.1118/1.4921364] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Revised: 04/24/2015] [Accepted: 05/08/2015] [Indexed: 12/26/2022] Open
Abstract
PURPOSE Nuclear cardiology plays an important role in clinical assessment and has enormous impact on the management of a variety of cardiovascular diseases. Pediatric patients at different age groups are exposed to a spectrum of radiation dose levels and associated cancer risks different from those of adults in diagnostic nuclear medicine procedures. Therefore, comprehensive radiation dosimetry evaluations for commonly used myocardial perfusion imaging (MPI) and viability radiotracers in target population (children and adults) at different age groups are highly desired. METHODS Using Monte Carlo calculations and biological effects of ionizing radiation VII model, we calculate the S-values for a number of radionuclides (Tl-201, Tc-99m, I-123, C-11, N-13, O-15, F-18, and Rb-82) and estimate the absorbed dose and effective dose for 12 MPI radiotracers in computational models including the newborn, 1-, 5-, 10-, 15-yr-old, and adult male and female computational phantoms. RESULTS For most organs, (201)Tl produces the highest absorbed dose whereas (82)Rb and (15)O-water produce the lowest absorbed dose. For the newborn baby and adult patient, the effective dose of (82)Rb is 48% and 77% lower than that of (99m)Tc-tetrofosmin (rest), respectively. CONCLUSIONS (82)Rb results in lower effective dose in adults compared to (99m)Tc-labeled tracers. However, this advantage is less apparent in children. The produced dosimetric databases for various radiotracers used in cardiovascular imaging, using new generation of computational models, can be used for risk-benefit assessment of a spectrum of patient population in clinical nuclear cardiology practice.
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Affiliation(s)
- Tianwu Xie
- Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva 4 CH-1211, Switzerland
| | - Choonsik Lee
- Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institute of Health, Bethesda, Maryland 20852
| | - Wesley E Bolch
- Departments of Nuclear & Radiological and Biomedical Engineering, University of Florida, Gainesville, Florida 32611
| | - Habib Zaidi
- Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva 4 CH-1211, Switzerland; Geneva Neuroscience Center, Geneva University, Geneva CH-1205, Switzerland; and Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen 9700 RB, Netherlands
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Abstract
This paper does not necessarily reflect the views of the International Commission on Radiological Protection. The protection quantity 'effective dose' was developed by the International Commission on Radiological Protection (ICRP) for use in the radiological protection of workers and the public. In this context, it is used as a risk-adjusted dosimetric quantity to optimise protection, comparing received or planned doses with constraints, reference levels, and limits expressed in the same quantity. Considering exposures incurred during medical procedures, effective dose can be of practical value for comparing: doses from different diagnostic examinations and interventional procedures; the use of similar technologies and procedures in different hospitals and countries; and the use of different technologies for the same medical examination, provided that the representative patients or patient populations for which the effective doses are derived are similar with regard to age and sex. However, as stated in ICRP Publication 103, '… risk assessment for medical diagnosis and treatment… is best evaluated using appropriate risk values for the individual tissues at risk and for the age and sex distribution of the individuals undergoing the medical procedures'. This topic was explored in a session of the First ICRP Symposium with arguments for and against the use of a new quantity referred to as 'effective risk', and examination of variations in estimated risk for different diagnostic procedures according to the age and sex of the exposed individuals. This paper restates the primary purposes of effective dose, and summarises estimates of variation in individual risk from medical procedures. The authors support the judicious use of effective dose as an indicator of possible risk, but caution against the use of effective risk as compared with the calculation of scientific best estimates of risk with consideration of associated uncertainties.
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Affiliation(s)
- J Harrison
- Public Health England, Centre for Radiation, Chemical and Environmental Hazards, Chilton, Didcot, Oxon OX11 0RQ, UK
| | - P O Lopez
- International Atomic Energy Agency, Vienna
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How to Appropriately Calculate Effective Dose for CT Using Either Size-Specific Dose Estimates or Dose-Length Product. AJR Am J Roentgenol 2015; 204:953-8. [DOI: 10.2214/ajr.14.13317] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Kornerup JS, Brodin P, Birk Christensen C, Björk-Eriksson T, Kiil-Berthelsen A, Borgwardt L, Munck Af Rosenschöld P. Use of PET/CT instead of CT-only when planning for radiation therapy does not notably increase life years lost in children being treated for cancer. Pediatr Radiol 2015; 45:570-81. [PMID: 25378209 DOI: 10.1007/s00247-014-3197-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Revised: 07/03/2014] [Accepted: 08/13/2014] [Indexed: 01/09/2023]
Abstract
BACKGROUND PET/CT may be more helpful than CT alone for radiation therapy planning, but the added risk due to higher doses of ionizing radiation is unknown. OBJECTIVE To estimate the risk of cancer induction and mortality attributable to the [F-18]2-fluoro-2-deoxyglucose (FDG) PET and CT scans used for radiation therapy planning in children with cancer, and compare to the risks attributable to the cancer treatment. MATERIALS AND METHODS Organ doses and effective doses were estimated for 40 children (2-18 years old) who had been scanned using PET/CT as part of radiation therapy planning. The risk of inducing secondary cancer was estimated using the models in BEIR VII. The prognosis of an induced cancer was taken into account and the reduction in life expectancy, in terms of life years lost, was estimated for the diagnostics and compared to the life years lost attributable to the therapy. Multivariate linear regression was performed to find predictors for a high contribution to life years lost from the radiation therapy planning diagnostics. RESULTS The mean contribution from PET to the effective dose from one PET/CT scan was 24% (range: 7-64%). The average proportion of life years lost attributable to the nuclear medicine dose component from one PET/CT scan was 15% (range: 3-41%). The ratio of life years lost from the radiation therapy planning PET/CT scans and that of the cancer treatment was on average 0.02 (range: 0.01-0.09). Female gender was associated with increased life years lost from the scans (P < 0.001). CONCLUSION Using FDG-PET/CT instead of CT only when defining the target volumes for radiation therapy of children with cancer does not notably increase the number of life years lost attributable to diagnostic examinations.
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Affiliation(s)
- Josefine S Kornerup
- Section of Radiotherapy, Department of Oncology, Rigshospitalet, Blegdamsvej 9, 2100, Copenhagen, Denmark,
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Liu H, Gao Y, Ding A, Caracappa PF, Xu XG. The profound effects of patient arm positioning on organ doses from CT procedures calculated using Monte Carlo simulations and deformable phantoms. RADIATION PROTECTION DOSIMETRY 2015; 164:368-375. [PMID: 25227436 PMCID: PMC4405194 DOI: 10.1093/rpd/ncu284] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Revised: 07/15/2014] [Accepted: 08/17/2014] [Indexed: 06/03/2023]
Abstract
The purpose of this study was to evaluate the organ dose differences caused by the arms-raised and arms-lowered postures for multidetector computed tomography procedures. Organ doses were calculated using computational phantoms and Monte Carlo simulations. The arm position in two previously developed adult male and female human phantoms was adjusted to represent 'raised' and 'lowered' postures using advanced BREP-based mesh surface geometries. Organ doses from routine computed tomography (CT) scan protocols, including the chest, abdomen-pelvis, and chest-abdomen-pelvis scans, were simulated at various tube voltages and reported in the unit of mGy per 100 mAs. The CT scanner model was based on previously tested work. The differences in organ dose per unit tube current between raised and lowered arm postures were studied. Furthermore, the differences due to the tube current modulation (TCM) for these two different postures and their impact on organ doses were also investigated. For a given scan parameter, a patient having lowered arms received smaller doses to organs located within the chest, abdomen or pelvis when compared with the patient having raised arms. As expected, this is caused by the attenuation of the primary X rays by the arms. However, the skin doses and bone surface doses in the patient having lowered arms were found to be 3.97-32.12% larger than those in a patient having raised arms due to the fact that more skin and spongiosa were covered in the scan range when the arms are lowered. This study also found that dose differences become smaller with the increase in tube voltage for most of organs or tissues except the skin. For example, the liver dose differences decreased from -15.01 to -11.33% whereas the skin dose differences increased from 21.53 to 25.24% with tube voltage increased from 80 to 140 kVp. With TCM applied, the organ doses of all the listed organs in patient having lowered arms are larger due to the additional tube current necessary to overcome the presence of the arms while maintaining sufficient image quality Arm position affects the dose to internal organs from CT scans by as much as 25.3%. The presence of arms in the scan range results in a dose increase for the skin and bone surface, but a dose decrease for organs located in the torso. Considering the use of TCM, which is common in many clinics, the patient having lowered arms may receive 50% higher radiation dose to most of the organs because of the increased tube current. The use of higher tube voltage might narrow such dose differences between patients of these two postures due to the greater penetration of higher-energy X rays. Therefore, when calculating or reporting patient doses from CT scans, it is prudent to select an appropriate phantom that accurately represents the patient posture.
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Affiliation(s)
- Haikuan Liu
- Institute of Radiation Medicine, Fudan University, Shanghai 200032, China Nuclear Engineering Program, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - Yiming Gao
- Nuclear Engineering Program, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - Aiping Ding
- Nuclear Engineering Program, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - Peter F Caracappa
- Nuclear Engineering Program, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - X George Xu
- Nuclear Engineering Program, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
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Fahey FH, Bom HHS, Chiti A, Choi YY, Huang G, Lassmann M, Laurin N, Mut F, Nuñez-Miller R, O'Keeffe D, Pradhan P, Scott AM, Song S, Soni N, Uchiyama M, Vargas L. Standardization of administered activities in pediatric nuclear medicine: a report of the first nuclear medicine global initiative project, part 1-statement of the issue and a review of available resources. J Nucl Med 2015; 56:646-51. [PMID: 25766899 DOI: 10.2967/jnumed.114.152249] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Accepted: 02/03/2015] [Indexed: 01/04/2023] Open
Abstract
The Nuclear Medicine Global Initiative (NMGI) was formed in 2012 and consists of 13 international organizations with direct involvement in nuclear medicine. The underlying objectives of the NMGI were to promote human health by advancing the field of nuclear medicine and molecular imaging, encourage global collaboration in education, and harmonize procedure guidelines and other policies that ultimately lead to improvements in quality and safety in the field throughout the world. For its first project, the NMGI decided to consider the issues involved in the standardization of administered activities in pediatric nuclear medicine. This article presents part 1 of the final report of this initial project of the NMGI. It provides a review of the value of pediatric nuclear medicine, the current understanding of the carcinogenic risk of radiation as it pertains to the administration of radiopharmaceuticals in children, and the application of dosimetric models in children. A listing of pertinent educational and reference resources available in print and online is also provided. The forthcoming part 2 report will discuss current standards for administered activities in children and adolescents that have been developed by various organizations and an evaluation of the current practice of pediatric nuclear medicine specifically with regard to administered activities as determined by an international survey of nuclear medicine clinics and centers. Lastly, the part 2 report will recommend a path forward toward global standardization of the administration of radiopharmaceuticals in children.
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Affiliation(s)
- Frederic H Fahey
- Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | | | | | | | - Gang Huang
- Renji Hospital, School of Medicine, Shanghai Jiaotong University, Shanghai, China
| | | | - Norman Laurin
- Centre Hospitalier Affilié Universitaire Régional de Trois-Rivières, Quebec, Canada
| | - Fernando Mut
- Spanish Association Hospital, Montevideo, Uruguay
| | | | | | - Prasanta Pradhan
- Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India
| | - Andrew M Scott
- Austin Hospital and Ludwig Institute for Cancer Research, Melbourne, Australia
| | - Shaoli Song
- Renji Hospital, School of Medicine, Shanghai Jiaotong University, Shanghai, China
| | - Nischal Soni
- Department of Nuclear Medicine, Inkosi Albert Luthuli Central Hospital, DurbanKwaZulu Natal, South Africa
| | - Mayuki Uchiyama
- Department of Radiology, The Jikei University School of Medicine, Minato, Tokyo, Japan; and
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131
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Januzis N, Nguyen G, Hoang JK, Lowry C, Yoshizumi TT. A novel method of estimating effective dose from the point dose method: a case study--parathyroid CT scans. Phys Med Biol 2015; 60:1763-73. [PMID: 25658032 DOI: 10.1088/0031-9155/60/5/1763] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The purpose of this study was to validate a novel approach of applying a partial volume correction factor (PVCF) using a limited number of MOSFET detectors in the effective dose (E) calculation. The results of the proposed PVCF method were compared to the results from both the point dose (PD) method and a commercial CT dose estimation software (CT-Expo). To measure organ doses, an adult female anthropomorphic phantom was loaded with 20 MOSFET detectors and was scanned using the non-contrast and 2 phase contrast-enhanced parathyroid imaging protocols on a 64-slice multi-detector computed tomography scanner. E was computed by three methods: the PD method, the PVCF method, and the CT-Expo method. The E (in mSv) for the PD method, the PVCF method, and CT-Expo method was 2.6 ± 0.2, 1.3 ± 0.1, and 1.1 for the non-contrast scan, 21.9 ± 0.4, 13.9 ± 0.2, and 14.6 for the 1st phase of the contrast-enhanced scan, and 15.5 ± 0.3, 9.8 ± 0.1, and 10.4 for the 2nd phase of the contrast-enhanced scan, respectively. The E with the PD method differed from the PVCF method by 66.7% for the non-contrast scan, by 44.9% and by 45.5% respectively for the 1st and 2nd phases of the contrast-enhanced scan. The E with PVCF was comparable to the results from the CT-Expo method with percent differences of 15.8%, 5.0%, and 6.3% for the non-contrast scan and the 1st and 2nd phases of the contrast-enhanced scan, respectively. To conclude, the PVCF method estimated E within 16% difference as compared to 50-70% in the PD method. In addition, the results demonstrate that E can be estimated accurately from a limited number of detectors.
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Affiliation(s)
- Natalie Januzis
- Medical Physics Graduate Program, Duke University, Durham NC 27705, USA. Duke Radiation Dosimetry Laboratory, Duke University Medical Center, Durham, NC 27705, USA
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132
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Uselmann AJ, Thomadsen BR. On effective dose for radiotherapy based on doses to nontarget organs and tissues. Med Phys 2015; 42:977-82. [DOI: 10.1118/1.4906190] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
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Hoogeveen RC, Rottke D, van der Stelt PF, Berkhout WER. Dose reduction in orthodontic lateral cephalography: dosimetric evaluation of a novel cephalographic thyroid protector (CTP) and anatomical cranial collimation (ACC). Dentomaxillofac Radiol 2015; 44:20140260. [PMID: 25564885 PMCID: PMC4628428 DOI: 10.1259/dmfr.20140260] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2014] [Revised: 12/19/2014] [Accepted: 01/06/2015] [Indexed: 01/15/2023] Open
Abstract
OBJECTIVES To test the dose-reducing capabilities of a novel thyroid protection device and a recently introduced cranial collimator to be used in orthodontic lateral cephalography. METHODS Cephalographic thyroid protector (CTP) was designed to shield the thyroid while leaving the cervical vertebrae depicted. Using a RANDO(®) head phantom (The Phantom Laboratory, Salem, NY) equipped with dosemeters and a Proline XC (Planmeca, Helsinki, Finland) cephalograph, lateral cephalograms were taken, and the effective dose (ED) was calculated for four protocols: (1) without shielding; (2) with CTP; (3) with CTP and anatomical cranial collimator (ACC); and (4) with a thyroid collar (TC). RESULTS The ED for the respective protocols was (1) 8.51; (2) 5.39; (3) 3.50; and (4) 4.97 µSv. The organ dose for the thyroid was reduced from 30.17 to 4.50 µSv in Protocols 2 and 3 and to 3.33 µSv in Protocol 4. CONCLUSIONS The use of just the CTP (Protocol 2) resulted in a 36.8% reduction of the ED of a lateral cephalogram. This was comparable to the classical TC (Protocol 4). A 58.8% reduction of the ED was obtained when combining CTP and ACC (Protocol 3). The dose to the radiosensitive thyroid gland was reduced by 85% in Protocols 2 and 3 and by 89% in Protocol 4.
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Affiliation(s)
- R C Hoogeveen
- Section of Oral and Maxillofacial Radiology, Academic Center for Dentistry Amsterdam ACTA, Amsterdam, Netherlands
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134
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Kalender WA, Saltybaeva N, Kolditz D, Hupfer M, Beister M, Schmidt B. Generating and using patient-specific whole-body models for organ dose estimates in CT with increased accuracy: Feasibility and validation. Phys Med 2014; 30:925-33. [DOI: 10.1016/j.ejmp.2014.09.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 08/07/2014] [Accepted: 09/09/2014] [Indexed: 11/24/2022] Open
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135
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Trattner S, Cheng B, Pieniazek RL, Hoffmann U, Douglas PS, Einstein AJ. Sample size requirements for estimating effective dose from computed tomography using solid-state metal-oxide-semiconductor field-effect transistor dosimetry. Med Phys 2014; 41:042102. [PMID: 24694150 DOI: 10.1118/1.4868693] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Effective dose (ED) is a widely used metric for comparing ionizing radiation burden between different imaging modalities, scanners, and scan protocols. In computed tomography (CT), ED can be estimated by performing scans on an anthropomorphic phantom in which metal-oxide-semiconductor field-effect transistor (MOSFET) solid-state dosimeters have been placed to enable organ dose measurements. Here a statistical framework is established to determine the sample size (number of scans) needed for estimating ED to a desired precision and confidence, for a particular scanner and scan protocol, subject to practical limitations. METHODS The statistical scheme involves solving equations which minimize the sample size required for estimating ED to desired precision and confidence. It is subject to a constrained variation of the estimated ED and solved using the Lagrange multiplier method. The scheme incorporates measurement variation introduced both by MOSFET calibration, and by variation in MOSFET readings between repeated CT scans. Sample size requirements are illustrated on cardiac, chest, and abdomen-pelvis CT scans performed on a 320-row scanner and chest CT performed on a 16-row scanner. RESULTS Sample sizes for estimating ED vary considerably between scanners and protocols. Sample size increases as the required precision or confidence is higher and also as the anticipated ED is lower. For example, for a helical chest protocol, for 95% confidence and 5% precision for the ED, 30 measurements are required on the 320-row scanner and 11 on the 16-row scanner when the anticipated ED is 4 mSv; these sample sizes are 5 and 2, respectively, when the anticipated ED is 10 mSv. CONCLUSIONS Applying the suggested scheme, it was found that even at modest sample sizes, it is feasible to estimate ED with high precision and a high degree of confidence. As CT technology develops enabling ED to be lowered, more MOSFET measurements are needed to estimate ED with the same precision and confidence.
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Affiliation(s)
- Sigal Trattner
- Department of Medicine, Division of Cardiology, Columbia University Medical Center and New York-Presbyterian Hospital, New York, New York 10032
| | - Bin Cheng
- Department of Biostatistics, Columbia University Mailman School of Public Health, New York, New York 10032
| | - Radoslaw L Pieniazek
- Center for Radiological Research, Columbia University Medical Center and New York-Presbyterian Hospital, New York, New York 10032
| | - Udo Hoffmann
- Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114
| | - Pamela S Douglas
- Department of Medicine, Division of Cardiology, Duke University, Durham, North Carolina 27715
| | - Andrew J Einstein
- Department of Medicine, Division of Cardiology, Columbia University Medical Center and New York-Presbyterian Hospital, New York, New York and Department of Radiology, Columbia University Medical Center and New York-Presbyterian Hospital, New York, New York
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136
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An overview of measuring and modelling dose and risk from ionising radiation for medical exposures. Radiography (Lond) 2014. [DOI: 10.1016/j.radi.2014.05.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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137
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From 'Image Gently' to image intelligently: a personalized perspective on diagnostic radiation risk. Pediatr Radiol 2014; 44 Suppl 3:444-9. [PMID: 25304703 DOI: 10.1007/s00247-014-3037-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Revised: 03/14/2014] [Accepted: 05/07/2014] [Indexed: 12/11/2022]
Abstract
The risk of ionizing radiation from diagnostic imaging has been a popular topic in the radiology literature and lay press. Communicating the magnitude of risk to patients and caregivers is problematic because of the uncertainty in estimates derived principally from epidemiological studies of large populations, and alternative approaches are needed to provide a scientific basis for personalized risk estimates. The underlying patient disease and life expectancy greatly influence risk projections. Research into the biological mechanisms of radiation-induced DNA damage and repair challenges the linear no-threshold dose-response assumption and reveals that individuals vary in sensitivity to radiation. Studies of decision-making psychology show that individuals are highly susceptible to irrational biases when judging risks. Truly informed medical decision-making that respects patient autonomy requires appropriate framing of radiation risks in perspective with other risks and with the benefits of imaging. To follow the principles of personalized medicine and treat patients according to their specific phenotypic and personality profiles, diagnostic imaging should optimally be tailored not only to patient size, body region and clinical indication, but also to underlying disease conditions, radio-sensitivity and risk perception and preferences that vary among individuals.
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138
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Westra SJ. The communication of the radiation risk from CT in relation to its clinical benefit in the era of personalized medicine: part 1: the radiation risk from CT. Pediatr Radiol 2014; 44 Suppl 3:515-8. [PMID: 25304714 DOI: 10.1007/s00247-014-3139-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Revised: 04/29/2014] [Accepted: 07/18/2014] [Indexed: 11/25/2022]
Abstract
The theory of radiation carcinogenesis has been debated for decades. Most estimates of the radiation risks from CT have been based on extrapolations from the lifespan follow-up study of atomic bomb survivors and on follow-up studies after therapeutic radiation, using the linear no-threshold theory. Based on this, many population-based projections of induction of future cancers by CT have been published that should not be used to estimate the risk to an individual because of their large margin of error. This has changed recently with the publication of three large international cohort follow-up studies, which link observed cancers to CT scans received in childhood. A fourth ongoing multi-country study in Europe is expected to have enough statistical power to address the limitations of the prior studies. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) report released in 2013 specifically addresses variability in response of the pediatric population exposed to ionizing radiation. Most authorities now conclude that there is enough evidence to link future cancers to the radiation exposure from a single CT scan in childhood but that cancer risk estimates for individuals must be based on the specifics of exposure, age at exposure and absorbed dose to certain tissues. Generalizations are not appropriate, and the communication of the CT risk to individuals should be conducted within the framework of personalized medicine.
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Affiliation(s)
- Sjirk J Westra
- Division of Pediatric Radiology, Massachusetts General Hospital, 34 Fruit St., White 246A, Boston, MA, 02114, USA,
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139
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Lopez-Rendon X, Zhang G, Bosmans H, Oyen R, Zanca F. Implementing the complete beam hardening effect of the bowtie filter versus scaling beam intensities: effects on dosimetric applications in computed tomography. J Med Imaging (Bellingham) 2014; 1:033507. [PMID: 26158059 PMCID: PMC4478776 DOI: 10.1117/1.jmi.1.3.033507] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Accepted: 11/25/2014] [Indexed: 11/14/2022] Open
Abstract
The bowtie filter is an essential element of computed tomography scanners. Implementation of this filter in a Monte Carlo dosimetry platform can be based on Turner's method, which describes how to measure the filter thickness and relate the x-ray beam as a function of bowtie angle to the central beam. In that application, the beam hardening is accounted for by means of weighting factors that are associated to the photons according to their position (fan angle) and energy. We assessed an alternative approximation in which the photon spectrum is given a fan angle-dependent scaling factor. The aim of our investigation was to evaluate the effects on dose accuracy estimation when using the gold standard bowtie filter method versus a beam scaling approximation method. In particular, we wanted to assess the percentage dose differences between the two methods for several water thicknesses representative for different patients of different body mass index. The largest percentage differences were found for the thickest part of the bowtie filter and increased with patient size.
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Affiliation(s)
- Xochitl Lopez-Rendon
- Katholieke Universiteit Leuven, Division of Medical Physics and Quality Assessment, Department of Imaging and Pathology, Herestraat 49 P.O. Box 7003, 3000 Leuven, Belgium
| | - Guozhi Zhang
- University Hospitals Leuven, Department of Radiology, Herestraat 49, Leuven 3000, Belgium
| | - Hilde Bosmans
- Katholieke Universiteit Leuven, Division of Medical Physics and Quality Assessment, Department of Imaging and Pathology, Herestraat 49 P.O. Box 7003, 3000 Leuven, Belgium
- University Hospitals Leuven, Department of Radiology, Herestraat 49, Leuven 3000, Belgium
| | - Raymond Oyen
- Katholieke Universiteit Leuven, Division of Medical Physics and Quality Assessment, Department of Imaging and Pathology, Herestraat 49 P.O. Box 7003, 3000 Leuven, Belgium
- University Hospitals Leuven, Department of Radiology, Herestraat 49, Leuven 3000, Belgium
| | - Federica Zanca
- Katholieke Universiteit Leuven, Division of Medical Physics and Quality Assessment, Department of Imaging and Pathology, Herestraat 49 P.O. Box 7003, 3000 Leuven, Belgium
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140
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Strauss KJ. Dose indices: everybody wants a number. Pediatr Radiol 2014; 44 Suppl 3:450-9. [PMID: 25304704 DOI: 10.1007/s00247-014-3104-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 05/27/2014] [Accepted: 06/19/2014] [Indexed: 11/24/2022]
Abstract
This paper discusses the merits and weaknesses of the standard terms that have been developed to quantify CT dose: CT dose indices (CTDI), dose length product (DLP) and effective dose. The difference between the measured CTDIvol and the CTDIvol displayed on the CT scanner illustrates a clinical dilemma. Displayed CTDIvol represents the radiation dose delivered to a plastic phantom, which is significantly different from the dose delivered to the patient, depending on the size of the patient. Although effective dose is simple to calculate for an individual patient, it was never intended for this purpose. The need for a simple, appropriate method to estimate pediatric patient doses led to the development of the size-specific dose estimate (SSDE), the newest CT dose index. Here I compare SSDE and its merits to the use of effective dose to estimate patient dose. The discussion concludes with a few sample calculations and basic clinical applications of SSDE to better quantify pediatric patient dose from CT scans.
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Affiliation(s)
- Keith J Strauss
- Department of Radiology, Cincinnati Children's Hospital Medical Center, MLC 50311, 3333 Burnet Ave., Cincinnati, OH, 45229-3026, USA,
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141
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The clinical efficacy of effective dose. JOURNAL OF RADIOTHERAPY IN PRACTICE 2014. [DOI: 10.1017/s1460396914000156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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142
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Homolka P, Leithner R, Billinger J, Gruber M. Ergebnisse der Österreichischen CT-Dosisstudie 2010: Effektive Dosen der häufigsten CT-Untersuchungen und Unterschiede zwischen Anwendern. Z Med Phys 2014; 24:224-30. [DOI: 10.1016/j.zemedi.2013.12.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2013] [Revised: 12/12/2013] [Accepted: 12/12/2013] [Indexed: 11/29/2022]
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143
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Barnaoui S, Rehel JL, Baysson H, Boudjemline Y, Girodon B, Bernier MO, Bonnet D, Aubert B. Local reference levels and organ doses from pediatric cardiac interventional procedures. Pediatr Cardiol 2014; 35:1037-45. [PMID: 24651982 DOI: 10.1007/s00246-014-0895-5] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Accepted: 02/28/2014] [Indexed: 10/25/2022]
Abstract
Interventional cardiology (IC) procedures can be responsible for relatively high radiation doses compared to conventional radiology especially for young patients. The aim of this study was to assess current exposure levels in a French reference centre of pediatric IC. Dosimetric data including dose area product (DAP), fluoroscopy time (FT) and number of cine frame (NF) were analysed taking into account patient weight. Doses to the lungs, esophagus, breast and thyroid were evaluated using anthropomorphic phantoms and thermoluminescent dosimeters. Finally, effective doses (E) were calculated using DAP and conversion factors calculated with PCXMC 2.0 software. 801 IC procedures performed between 2010 and 2011 were analysed. Large variations were observed for DAP, FT and NF values for a given procedure and a given weight group. The assessment of organ doses showed high levels of dose to the lungs and esophagus especially in new-born babies. For diagnostic procedures, E varied from 0.3 to 23 mSv with a mean value of 4.8 mSv and for therapeutic procedures, values ranged from 0.1 to 48.4 mSv with a mean value of 7.3 mSv. The highest values were recorded for angioplasty procedures (mean 13 mSv, range 0.6-48.4 mSv). The increasing use of IC in pediatric population stresses the need of setting up reference levels and keeping doses to children as low as possible.
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Affiliation(s)
- S Barnaoui
- Medical Radiation Protection Expertise Unit, Institute of Radioprotection and Nuclear Safety, Fontenay-aux-Roses, France
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144
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Pauwels R, Cockmartin L, Ivanauskaité D, Urbonienė A, Gavala S, Donta C, Tsiklakis K, Jacobs R, Bosmans H, Bogaerts R, Horner K. Estimating cancer risk from dental cone-beam CT exposures based on skin dosimetry. Phys Med Biol 2014; 59:3877-91. [DOI: 10.1088/0031-9155/59/14/3877] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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145
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Johnson JN, Hornik CP, Li JS, Benjamin DK, Yoshizumi TT, Reiman RE, Frush DP, Hill KD. Cumulative radiation exposure and cancer risk estimation in children with heart disease. Circulation 2014; 130:161-7. [PMID: 24914037 DOI: 10.1161/circulationaha.113.005425] [Citation(s) in RCA: 167] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
BACKGROUND Children with heart disease are frequently exposed to imaging examinations that use ionizing radiation. Although radiation exposure is potentially carcinogenic, there are limited data on cumulative exposure and the associated cancer risk. We evaluated the cumulative effective dose of radiation from all radiation examinations to estimate the lifetime attributable risk of cancer in children with heart disease. METHODS AND RESULTS Children ≤6 years of age who had previously undergone 1 of 7 primary surgical procedures for heart disease at a single institution between 2005 and 2010 were eligible for the study. Exposure to radiation-producing examinations was tabulated, and cumulative effective dose was calculated in millisieverts. These data were used to estimate lifetime attributable risk of cancer above baseline using the approach of the Committee on Biological Effects of Ionizing Radiation VII. The cohort included 337 children exposed to 13 932 radiation examinations. Conventional radiographs represented 92% of examinations, whereas cardiac catheterization and computed tomography accounted for 81% of cumulative exposure. Overall median cumulative effective dose was 2.7 mSv (range, 0.1-76.9 mSv), and the associated lifetime attributable risk of cancer was 0.07% (range, 0.001%-6.5%). Median lifetime attributable risk of cancer ranged widely depending on surgical complexity (0.006%-1.6% for the 7 surgical cohorts) and was twice as high in females per unit exposure (0.04% versus 0.02% per 1-mSv effective dose for females versus males, respectively; P<0.001). CONCLUSIONS Overall radiation exposures in children with heart disease are relatively low; however, select cohorts receive significant exposure. Cancer risk estimation highlights the need to limit radiation dose, particularly for high-exposure modalities.
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Affiliation(s)
- Jason N Johnson
- From the Division of Pediatric Cardiology (J.N.J., C.P.H., J.S.L., K.D.H.) and Division of Radiology (T. T. Y., R.E.R., D.P.F.), Department of Pediatrics, Duke University Medical Center, Durham, NC; and Duke Clinical Research Institute, Durham, NC (J.S.L., D.K.B., K.D.H.)
| | - Christoph P Hornik
- From the Division of Pediatric Cardiology (J.N.J., C.P.H., J.S.L., K.D.H.) and Division of Radiology (T. T. Y., R.E.R., D.P.F.), Department of Pediatrics, Duke University Medical Center, Durham, NC; and Duke Clinical Research Institute, Durham, NC (J.S.L., D.K.B., K.D.H.)
| | - Jennifer S Li
- From the Division of Pediatric Cardiology (J.N.J., C.P.H., J.S.L., K.D.H.) and Division of Radiology (T. T. Y., R.E.R., D.P.F.), Department of Pediatrics, Duke University Medical Center, Durham, NC; and Duke Clinical Research Institute, Durham, NC (J.S.L., D.K.B., K.D.H.)
| | - Daniel K Benjamin
- From the Division of Pediatric Cardiology (J.N.J., C.P.H., J.S.L., K.D.H.) and Division of Radiology (T. T. Y., R.E.R., D.P.F.), Department of Pediatrics, Duke University Medical Center, Durham, NC; and Duke Clinical Research Institute, Durham, NC (J.S.L., D.K.B., K.D.H.)
| | - Terry T Yoshizumi
- From the Division of Pediatric Cardiology (J.N.J., C.P.H., J.S.L., K.D.H.) and Division of Radiology (T. T. Y., R.E.R., D.P.F.), Department of Pediatrics, Duke University Medical Center, Durham, NC; and Duke Clinical Research Institute, Durham, NC (J.S.L., D.K.B., K.D.H.)
| | - Robert E Reiman
- From the Division of Pediatric Cardiology (J.N.J., C.P.H., J.S.L., K.D.H.) and Division of Radiology (T. T. Y., R.E.R., D.P.F.), Department of Pediatrics, Duke University Medical Center, Durham, NC; and Duke Clinical Research Institute, Durham, NC (J.S.L., D.K.B., K.D.H.)
| | - Donald P Frush
- From the Division of Pediatric Cardiology (J.N.J., C.P.H., J.S.L., K.D.H.) and Division of Radiology (T. T. Y., R.E.R., D.P.F.), Department of Pediatrics, Duke University Medical Center, Durham, NC; and Duke Clinical Research Institute, Durham, NC (J.S.L., D.K.B., K.D.H.)
| | - Kevin D Hill
- From the Division of Pediatric Cardiology (J.N.J., C.P.H., J.S.L., K.D.H.) and Division of Radiology (T. T. Y., R.E.R., D.P.F.), Department of Pediatrics, Duke University Medical Center, Durham, NC; and Duke Clinical Research Institute, Durham, NC (J.S.L., D.K.B., K.D.H.).
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146
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Pursnani A, Lee A, Mayrhofer T, Panagia M, Sharma U, Abbara S, Hoffmann U, Ghoshhajra BB. Feasibility of a radiation dose conserving CT protocol for myocardial function assessment. Br J Radiol 2014; 87:20130755. [PMID: 24884727 DOI: 10.1259/bjr.20130755] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVE Assessment of myocardial function can be performed at higher noise levels than necessary for coronary arterial evaluation. We evaluated image quality and radiation exposure of a dose-conserving function-only acquisition vs retrospectively electrocardiogram(ECG)-gated coronary CTA with automatic tube current modulation. METHODS Of 26 patients who underwent clinically indicated coronary CTA for coronary and function evaluation, 13 (Group I) underwent prospectively ECG-triggered coronary CTA, followed by low-dose retrospectively ECG-gated scan for function (128-slice dual-source, 80 kVp; reference tube current, 100 mA; 8-mm-thick multiplanar reformatted reconstructions) performed either immediately (n = 6) or after 5- to 10-min delay for infarct assessment (n = 7). 13 corresponding controls (Group II) underwent retrospectively ECG-gated protocols (automatic tube potential selection with CARE kV/CARE Dose 4D; Siemens Healthcare, Forchheim, Germany) with aggressive dose modulation. Image quality assessment was performed on the six Group I subjects who underwent early post-contrast dedicated function scan and corresponding controls. Radiation exposure was based on dose-length product. RESULTS Contrast-to-noise ratio (CNR) was preserved throughout the cardiac cycle in Group I and varied according to dose modulation in Group II. Visual image quality indices were similar during end systole but were better in Group II at end diastole. Although the total radiation exposure was equivalent in Group I and Group II (284 vs 280 mGy cm), the median radiation exposure associated with only the dedicated function scan was 138 mGy cm (interquartile range, 116-203 mGy cm). CONCLUSION A low-dose retrospective ECG-gated protocol permits assessment of myocardial function at a median radiation exposure of 138 mGy cm and offers more consistent multiphase CNR vs traditional ECG-modulation protocols. This is useful for pure functional evaluation or as an adjunct to single-phase scan modes. ADVANCES IN KNOWLEDGE Radiation exposure can be limited with a tailored myocardial function CT protocol while maintaining preserved images.
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Affiliation(s)
- A Pursnani
- Cardiac MR PET CT Program, Division of Cardiology and Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
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Prioritizing examination-centered over patient-centered dose reduction: a hazard of institutional "benchmarking". AJR Am J Roentgenol 2014; 202:1062-8. [PMID: 24758661 DOI: 10.2214/ajr.13.11235] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
OBJECTIVE The purpose of this article is to evaluate whether examination-specific radiation dose metrics reliably measure an institution's success in reducing cancer risks. MATERIALS AND METHODS We projected health benefits from dose-reduction programs in a hypothetical institution that sought to decrease exposures from abdominopelvic CT. Using modeling techniques to project radiation-induced cancer risks and tertiary center data to inform the institution's abdominopelvic CT age distribution, we compared a program in which effective doses were reduced equally (from 10 to 7 mSv) across all scans with programs in which dose reduction was age dependent. For each program, we projected lethal cancers averted, life expectancy gained, and average institutional dose achieved. Markov Chain Monte Carlo methods were used to estimate uncertainty in projections. RESULTS The analysis's age distribution drew from 20,979 CT scans; 39% were from patients 65 years old and older. To illustrate trends yielded, if all patients in the hypothetical institution underwent 7-mSv (instead of 10-mSv) scans, we projected the maximum number of lethal cancers averted to be seven per 100,000 patients, and maximum life expectancy gained to be 0.26 days per patient, when averaged over the institution's population. When restricting dose reduction (from 10 to 7 mSv) to patients younger than 65 years, benefits were slightly lower (five lethal cancers averted per 100,000 patients and 0.22 days per patient gained); however, the average institutional dose was substantially higher (8.2 mSv). Although dose reduction in patients 65 years old and older accounted for only 16% of possible institutional life expectancy gains, this patient group contributed disproportionately (39%) to the institution's average dose. CONCLUSION Institutional examination-specific dose metrics can be misleading, because the least-benefited patients may contribute disproportionately toward "improved" averages.
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Don't let radiation scare trump patient care: 10 ways you can harm your patients by fear of radiation-induced cancer from diagnostic imaging. Thorax 2014; 69:782-4. [DOI: 10.1136/thoraxjnl-2014-205499] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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Sabarudin A, Mustafa Z, Nassir KM, Hamid HA, Sun Z. Radiation dose reduction in thoracic and abdomen-pelvic CT using tube current modulation: a phantom study. J Appl Clin Med Phys 2014; 16:5135. [PMID: 25679153 PMCID: PMC5689995 DOI: 10.1120/jacmp.v16i1.5135] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Revised: 09/12/2014] [Accepted: 09/08/2014] [Indexed: 11/23/2022] Open
Abstract
This phantom study was designed to compare the radiation dose in thoracic and abdomen-pelvic CT scans with and without use of tube current modulation (TCM). Effective dose (ED) and size-specific dose estimation (SSDE) were calculated with the absorbed doses measured at selective radiosensitive organs using a thermoluminescence dosimeter-100 (TLD-100). When compared to protocols without TCM, the ED and SSDE were reduced significantly with use of TCM for both the thoracic and abdomen-pelvic CT. With use of TCM, the ED was 6.50 ± 0.29 mSv for thoracic and 6.01 ± 0.20 mSv for the abdomen-pelvic CT protocols. However without use of TCM, the ED was 20.07 ± 0.24 mSv and 17.30 ± 0.41 mSv for the thoracic and abdomen-pelvic CT protocols, respectively. The corresponding SSDE was 10.18 ± 0.48 mGy and 11.96 ± 0.27 mGy for the thoracic and abdomen-pelvic CT protocols with TCM, and 31.56 ± 0.43 mGy and 33.23 ± 0.05 mGy for thoracic and abdomen-pelvic CT protocols without TCM, respectively. The highest absorbed dose was measured at the breast with 8.58 ± 0.12 mGy in the TCM protocols and 51.52 ± 14.72 mGy in the protocols without TCM during thoracic CT. In the abdomen-pelvic CT, the absorbed dose was highest at the skin with 9.30 ± 1.28mGy and 29.99 ± 2.23 mGy in protocols with and without use of TCM, respectively. In conclusion, the TCM technique results in significant dose reduction; thus it is to be highly recommended in routine thoracic and abdomen-pelvic CT.
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Affiliation(s)
- Akmal Sabarudin
- Diagnostic Imaging & Radiotherapy Program School of Diagnostic & Applied Health Sciences Faculty of Health Sciences Universiti Kebangsaan Malaysia 50300 Kuala Lumpur, Malaysia..
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Elbakri IA. Estimation of dose-area product-to-effective dose conversion factors for neonatal radiography using PCXMC. RADIATION PROTECTION DOSIMETRY 2014; 158:43-50. [PMID: 23896417 DOI: 10.1093/rpd/nct192] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Dose-area product-to-effective dose (E) conversion factors for chest, abdomen and abdomen-chest neonatal radiographs were computed. Seven patient models in the Monte Carlo software, PCXMC, were defined, representing neonates ranging in weight from 0.5 to 6.0 kg. Conversion factors for a tube potential range of 50-80 kVp at two beam filtrations (3.0 mm Al and 3.0 mm Al+0.1 mm Cu) were calculated. For 133 neonatal radiographs, effective dose values determined using these conversion factors were compared with those obtained from PCXMC simulations customised for each radiograph. For a 3.0-kg newborn irradiated at 60 kVp/3.0 mm Al beam filtration, the conversion factors were 2.58, 1.90 and 1.91 μSv (mGy cm(2))(-1) for chest, chest-abdomen and abdomen radiographs, respectively. Average dose difference between the conversion factors and customised dose calculations was 16 %. Disagreement in effective dose was most strongly correlated with under-collimation in the lateral direction.
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Affiliation(s)
- Idris A Elbakri
- Division of Medical Physics, CancerCare Manitoba, 675 McDermot Ave, Winnipeg, MB, Canada R3E 0V9
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