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Kyriakou I, Tremi I, Georgakilas AG, Emfietzoglou D. Microdosimetric investigation of the radiation quality of low-medium energy electrons using Geant4-DNA. Appl Radiat Isot 2021; 172:109654. [PMID: 33676082 DOI: 10.1016/j.apradiso.2021.109654] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 02/17/2021] [Accepted: 02/20/2021] [Indexed: 02/06/2023]
Abstract
The increasing clinical use of low-energy photon and electron sources (below few tens of keV) has raised concerns on the adequacy of the existing approximation of an energy-independent radiobiological effectiveness. In this work, the variation of the quality factor (Q) and relative biological effectiveness (RBE) of electrons over the low-medium energy range (0.1 keV-1 MeV) is examined using several microdosimetry-based Monte Carlo methodologies with input data obtained from Geant4-DNA track-structure simulations. The sensitivity of the results to the different methodologies, Geant4-DNA physics models, and target sizes is examined. Calculations of Q and RBE are based on the ICRU Report 40 recommendations, the Kellerer-Hahn approximation, the site version of the theory of dual radiation action (TDRA), the microdosimetric kinetic model (MKM) of cell survival, and the calculated yield of DNA double strand breaks (DSB). The stochastic energy deposition spectra needed as input in the above approaches have been calculated for nanometer spherical volumes using the different electron physics models of Geant4-DNA. Results are normalized at 100 keV electrons which is here considered the reference radiation. It is shown that in the energy range ~50 keV-1 MeV, the calculated Q and RBE are approximately unity (to within 1-2%) irrespective of the methodology, Geant4-DNA physics model, and target size. At lower energies, Q and RBE become energy-dependent reaching a maximum value of ~1.5-2.5 between ~200 and 700 eV. The detailed variation of Q and RBE at low energies depends mostly upon the adopted methodology and target size, and less so upon the Geant4-DNA physics model. Overall, the DSB yield predicts the highest RBE values (with RBEmax≈2.5) whereas the MKM the lowest RBE values (with RBEmax≈1.5). The ICRU Report 40, Kellerer-Hahn, and TDRA methods are in excellent agreement (to within 1-2%) over the whole energy range predicting a Qmax≈2. In conclusion, the approximation Q=RBE=1 was found to be valid only above ~50 keV whereas at lower energies both Q and RBE become strongly energy-dependent. It is envisioned that the present work will contribute towards establishing robust methodologies to determine theoretically the energy-dependence of radiation quality of individual electrons which may then be used in subsequent calculations involving practical electron and photon radiation sources.
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Affiliation(s)
- Ioanna Kyriakou
- Medical Physics Laboratory, University of Ioannina Medical School, 45110, Ioannina, Greece.
| | - Ioanna Tremi
- DNA Damage Laboratory, Physics Department, School of Applied Mathematical and Physical Sciences, National Technical University of Athens (NTUA), Zografou, Athens, Greece
| | - Alexandros G Georgakilas
- DNA Damage Laboratory, Physics Department, School of Applied Mathematical and Physical Sciences, National Technical University of Athens (NTUA), Zografou, Athens, Greece
| | - Dimitris Emfietzoglou
- Medical Physics Laboratory, University of Ioannina Medical School, 45110, Ioannina, Greece
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Koo BY, Lee KS. Reduction of scattered radiation dose by X-ray shielding during mammography. Radiat Phys Chem Oxf Engl 1993 2020. [DOI: 10.1016/j.radphyschem.2020.109111] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Oliver PAK, Thomson RM. Investigating energy deposition in glandular tissues for mammography using multiscale Monte Carlo simulations. Med Phys 2019; 46:1426-1436. [PMID: 30657190 DOI: 10.1002/mp.13372] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Revised: 11/29/2018] [Accepted: 12/22/2018] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To investigate energy deposition in glandular tissues of the breast on macro- and microscopic length scales in the context of mammography. METHODS Multiscale mammography models of breasts are developed, which include segmented, voxelized macroscopic tissue structure as well as nine regions of interest (ROIs) embedded throughout the breast tissue containing explicitly-modelled cells. Using a 30 kVp Mo/Mo spectrum, Monte Carlo (MC) techniques are used to calculate dose to ∼mm voxels containing glandular and/or adipose tissues, as well as energy deposition on cellular length scales. ROIs consist of at least 1000 mammary epithelial cells and ∼200 adipocytes; specific energy (energy imparted per unit mass; stochastic analogue of the absorbed dose) is calculated within mammary epithelial cell nuclei. RESULTS Macroscopic dose distributions within segmented breast tissue demonstrate considerable variation in energy deposition depending on depth and tissue structure. Doses to voxels containing glandular tissue vary between ∼0.1 and ∼4 times the mean glandular dose (MGD, averaged over the entire breast). Considering microscopic length scales, mean specific energies for mammary epithelial cell nuclei are ∼30% higher than the corresponding glandular voxel dose. Additionally, due to the stochastic nature of radiation, there is considerable variation in energy deposition throughout a cell population within a ROI: for a typical glandular voxel dose of 4 mGy, the standard deviation of the specific energy for mammary epithelial cell nuclei is 85% relative to the mean. Thus, for a glandular voxel dose of 4 mGy at the centre of the breast, corresponding mammary epithelial cell nuclei will receive specific energies up to ∼9 mGy (considering the upper end of the 1σ standard deviation of the specific energy), while a ROI located 2 cm closer to the radiation source will receive specific energies up to ∼40 mGy. Energy deposition within mammary epithelial cell nuclei is sensitive to cell model details including cellular elemental compositions and nucleus size, underlining the importance of realistic cellular models. CONCLUSIONS There is considerable variation in energy deposition on both macro- and microscopic length scales for mammography, with glandular voxel doses and corresponding cell nuclei specific energies many times higher than the MGD in parts of the breast. These results should be considered for radiation-induced cancer risk evaluation in mammography which has traditionally focused on a single metric such as the MGD.
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Affiliation(s)
- Patricia A K Oliver
- Carleton Laboratory for Radiotherapy Physics, Physics Dept., Carleton University, Ottawa, ON, K1S 5B6, Canada
| | - Rowan M Thomson
- Carleton Laboratory for Radiotherapy Physics, Physics Dept., Carleton University, Ottawa, ON, K1S 5B6, Canada
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Bellamy M, Puskin J, Hertel N, Eckerman K. An empirical method for deriving RBE values associated with electrons, photons and radionuclides. RADIATION PROTECTION DOSIMETRY 2015; 167:664-670. [PMID: 25636403 DOI: 10.1093/rpd/ncu358] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2014] [Accepted: 11/19/2014] [Indexed: 06/04/2023]
Abstract
There is substantial evidence to justify using relative biological effectiveness (RBE) values of >1 for low-energy electrons and photons. But, in the field of radiation protection, radiation associated with low linear energy transfer has been assigned a radiation weighting factor wR of 1. This value may be suitable for radiation protection but, for risk considerations, it is important to evaluate the potential elevated biological effectiveness of radiation to improve the quality of risk estimates. RBE values between 2 and 3 for tritium are implied by several experimental measurements. Additionally, elevated RBE values have been found for other similar low-energy radiation sources. In this work, RBE values are derived for electrons based upon the fractional deposition of absorbed dose of energies less than a few kiloelectron volts. Using this empirical method, RBE values were also derived for monoenergetic photons and 1070 radionuclides from ICRP Publication 107 for which photons and electrons are the primary emissions.
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Affiliation(s)
- M Bellamy
- Oak Ridge National Laboratory, Center for Radiation Protection Knowledge, PO Box 2008, Oak Ridge, TN 37831-6153, USA
| | - J Puskin
- Center for Science and Technology, Radiation Protection Division, ORIA (6608J), EPA, Washington, DC 20460, USA
| | - N Hertel
- Oak Ridge National Laboratory, Center for Radiation Protection Knowledge, PO Box 2008, Oak Ridge, TN 37831-6153, USA
| | - K Eckerman
- Oak Ridge National Laboratory, Center for Radiation Protection Knowledge, PO Box 2008, Oak Ridge, TN 37831-6153, USA
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Mills CE, Thome C, Koff D, Andrews DW, Boreham DR. The Relative Biological Effectiveness of Low-Dose Mammography Quality X Rays in the Human Breast MCF-10A Cell Line. Radiat Res 2015; 183:42-51. [DOI: 10.1667/rr13821.1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Hauge IHR, Pedersen K, Olerud HM, Hole EO, Hofvind S. The risk of radiation-induced breast cancers due to biennial mammographic screening in women aged 50-69 years is minimal. Acta Radiol 2014; 55:1174-9. [PMID: 24311702 DOI: 10.1177/0284185113514051] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND The main aim of mammographic screening is to reduce the mortality from breast cancer. However, use of ionizing radiation is considered a potential harm due to the possible risk of inducing cancer in healthy women. PURPOSE To estimate the potential number of radiation-induced breast cancers, radiation-induced breast cancer deaths, and lives saved due to implementation of organized mammographic screening as performed in Norway. MATERIAL AND METHODS We used a previously published excess absolute risk model which assumes a linear no-threshold dose-response. The estimates were calculated for 100,000 women aged 50-69 years, a screening interval of 2 years, and with an assumed follow-up until the age of 85 or 105 years. Radiation doses of 0.7, 2.5, and 5.7 mGy per screening examination, a latency time of 5 or 10 years, and a dose and dose-rate effectiveness factor (DDREF) of 1 or 2 were applied. RESULTS The total lifetime risk of radiation-induced breast cancers per 100,000 women was 10 (95% CI: 4-25) if the women were followed from the ages of 50 to 85 years, for a dose of 2.5 mGy, a latency time of 10 years, and a DDREF of 1. For the same parameter values the number of radiation-induced breast cancer death was 1 (95% CI: 0-2). The assumed number of lives saved is approximately 350. CONCLUSION The risk of radiation-induced breast cancer and breast cancer death due to mammographic screening is minimal. Women should not be discouraged from attending screening due to fear of radiation-induced breast cancer death.
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Affiliation(s)
- Ingrid Helen Ryste Hauge
- Norwegian Radiation Protection Authority, Østerås, Norway
- Department of Physics, University of Oslo, Oslo, Norway
- Oslo and Akershus University College of Applied Sciences, Faculty of Health Sciences, Department of Radiography and Dental Technology, Oslo, Norway
| | | | - Hilde Merete Olerud
- Norwegian Radiation Protection Authority, Østerås, Norway
- Department of Physics, University of Oslo, Oslo, Norway
| | | | - Solveig Hofvind
- Oslo and Akershus University College of Applied Sciences, Faculty of Health Sciences, Department of Radiography and Dental Technology, Oslo, Norway
- Cancer Registry of Norway, Oslo, Norway
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Wang B, Li D, Kovalchuk O. p53 Ser15 phosphorylation and histone modifications contribute to IR-induced miR-34a transcription in mammary epithelial cells. Cell Cycle 2013; 12:2073-83. [PMID: 23759592 DOI: 10.4161/cc.25135] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Previous studies have demonstrated that miR-34a is a direct transcriptional target of tumor suppressor p53 and plays a crucial role in p53-mediated biological processes, such as cell cycle arrest, apoptosis and senescence. However, the role of p53 phosphorylation at Ser15 and histone modifications in ionizing radiation (IR)-induced miR-34a transcription in human mammary epithelial cells remains unknown. The present study showed that IR triggers miR-34a induction in rat mammary gland tissue and human mammary epithelial cells in a dose- and time-dependent fashion. Gene copy number and CpG methylation exhibit no effect on IR-inducible miR-34a expression, while the levels of phosphorylated p53 at Ser15 are markedly elevated in human mammary epithelial cells 96 h post-IR, which correlates with IR-inducible miR-34a transcription and the p38 MAPK pathway. Conversely, suppression of p38 MAPK with SB239063 inhibits IR-induced p53 phosphorylation at Ser15 and miR-34a expression in a dose-dependent manner. Our study found that wild-type p53 is enriched at miR-34a promoter, and luciferase activity of miR-34a promoter reporter is attenuated by either mutant p53 (Ser15Ala) or mutant miR-34a promoter. Furthermore, IR also triggers phosphorylation, tri-methylation and acetylation of histone H3 and acetylation of histone H4, which correlates with IR-inducible miR-34a transcription, while SAHA potentiates IR-inducible miR-34a expression. Moreover, acetyl-histone H3 is significantly enriched at miR-34a promoter in IR-exposed HMEC cells. Yet, we show that there is no correlation between IR-inducible miR-34a expression and IR-induced rapid and transient G 2/M arrest. In sum, our novel data for the first time demonstrate that IR-induced p53 Ser15 phosphorylation via p38 MAPK is essential for its functional regulation of IR-inducible miR-34a transcription in human mammary epithelial cells, and that histone modifications may also play a key role in IR-inducible miR-34a expression.
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Affiliation(s)
- Bo Wang
- Department of Biological Sciences, University of Lethbridge, Lethbridge, AB Canada
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O'Connor MK, Li H, Rhodes DJ, Hruska CB, Clancy CB, Vetter RJ. Comparison of radiation exposure and associated radiation-induced cancer risks from mammography and molecular imaging of the breast. Med Phys 2011; 37:6187-98. [PMID: 21302775 DOI: 10.1118/1.3512759] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Recent studies have raised concerns about exposure to low-dose ionizing radiation from medical imaging procedures. Little has been published regarding the relative exposure and risks associated with breast imaging techniques such as breast specific gamma imaging (BSGI), molecular breast imaging (MBI), or positron emission mammography (PEM). The purpose of this article was to estimate and compare the risks of radiation-induced cancer from mammography and techniques such as PEM, BSGI, and MBI in a screening environment. METHODS The authors used a common scheme for all estimates of cancer incidence and mortality based on the excess absolute risk model from the BEIR VII report. The lifetime attributable risk model was used to estimate the lifetime risk of radiation-induced breast cancer incidence and mortality. All estimates of cancer incidence and mortality were based on a population of 100 000 females followed from birth to age 80 and adjusted for the fraction that survives to various ages between 0 and 80. Assuming annual screening from ages 40 to 80 and from ages 50 to 80, the cumulative cancer incidence and mortality attributed to digital mammography, screen-film mammography, MBI, BSGI, and PEM was calculated. The corresponding cancer incidence and mortality from natural background radiation was calculated as a useful reference. Assuming a 15%-32% reduction in mortality from screening, the benefit/risk ratio for the different imaging modalities was evaluated. RESULTS Using conventional doses of 925 MBq Tc-99m sestamibi for MBI and BSGI and 370 MBq F-18 FDG for PEM, the cumulative cancer incidence and mortality were found to be 15-30 times higher than digital mammography. The benefit/risk ratio for annual digital mammography was >50:1 for both the 40-80 and 50-80 screening groups, but dropped to 3:1 for the 40-49 age group. If the primary use of MBI, BSGI, and PEM is in women with dense breast tissue, then the administered doses need to be in the range 75-150 MBq for Tc-99m sestamibi and 35 MBq-70 MBq for F-18 FDG in order to obtain benefit/risk ratios comparable to those of mammography in these age groups. These dose ranges should be achievable with enhancements to current technology while maintaining a reasonable examination time. CONCLUSIONS The results of the dose estimates in this study clearly indicate that if molecular imaging techniques are to be of value in screening for breast cancer, then the administered doses need to be substantially reduced to better match the effective doses of mammography.
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Up-regulated proteins in the fluid bathing the tumour cell microenvironment as potential serological markers for early detection of cancer of the breast. Mol Oncol 2009; 4:65-89. [PMID: 20005186 DOI: 10.1016/j.molonc.2009.11.003] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2009] [Revised: 11/13/2009] [Accepted: 11/13/2009] [Indexed: 12/29/2022] Open
Abstract
Breast cancer is by far the most common diagnosed form of cancer and the leading cause of cancer death in women today. Clinically useful biomarkers for early detection of breast cancer could lead to a significant reduction in mortality. Here we describe a detailed analysis using gel-based proteomics in combination with mass spectrometry and immunohistochemistry (IHC) of the tumour interstitial fluids (TIF) and normal interstitial fluids (NIF) collected from 69 prospective breast cancer patients. The goal of this study was to identify abundant cancer up-regulated proteins that are externalised by cells in the tumour microenvironment of most if not all these lesions. To this end, we applied a phased biomarker discovery research strategy to the analysis of these samples rather than comparing all samples among each other, with inherent inter and intra-sample variability problems. To this end, we chose to use samples derived from a single tumour/benign tissue pair (patient 46, triple negative tumour), for which we had well-matched samples in terms of epithelial cell numbers, to generate the initial dataset. In this first phase we found 110 proteins that were up-regulated by a factor of 2 or more in the TIF, some of which were confirmed by IHC. In the second phase, we carried out a systematic computer assisted analysis of the 2D gels of the remaining 68 TIF samples in order to identify TIF 46 up-regulated proteins that were deregulated in 90% or more of all the available TIFs, thus representing common breast cancer markers. This second phase singled out a set of 26 breast cancer markers, most of which were also identified by a complementary analysis using LC-MS/MS. The expression of calreticulin, cellular retinoic acid-binding protein II, chloride intracellular channel protein 1, EF-1-beta, galectin 1, peroxiredoxin-2, platelet-derived endothelial cell growth factor, protein disulfide isomerase and ubiquitin carboxyl-terminal hydrolase 5 were further validated using a tissue microarray containing 70 malignant breast carcinomas of various grades of atypia. A significant number of these proteins have already been detected in the blood/plasma/secretome by others. The next steps, which include biomarker prioritization based on the hierarchal evaluation of these markers, antibody and antigen development, assay development, analytical validation, and preliminary testing in the blood of healthy and breast cancer patients, are discussed.
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Hamrita B, Chahed K, Trimeche M, Guillier CL, Hammann P, Chaïeb A, Korbi S, Chouchane L. Proteomics-based identification of α1-antitrypsin and haptoglobin precursors as novel serum markers in infiltrating ductal breast carcinomas. Clin Chim Acta 2009; 404:111-8. [DOI: 10.1016/j.cca.2009.03.033] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Revised: 03/09/2009] [Accepted: 03/09/2009] [Indexed: 01/03/2023]
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Hunter N, Muirhead CR. Review of relative biological effectiveness dependence on linear energy transfer for low-LET radiations. JOURNAL OF RADIOLOGICAL PROTECTION : OFFICIAL JOURNAL OF THE SOCIETY FOR RADIOLOGICAL PROTECTION 2009; 29:5-21. [PMID: 19225189 DOI: 10.1088/0952-4746/29/1/r01] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Information on Japanese A-bomb survivors exposed to gamma radiation has been used to estimate cancer risks for the whole range of photon (x-rays) and electron energies which are commonly encountered by radiation workers in the work place or by patients and workers in diagnostic radiology. However, there is some uncertainty regarding the radiation effectiveness of various low-linear energy transfer (low-LET) radiations (x-rays, gamma radiation and electrons). In this paper we review information on the effectiveness of low-LET radiations on the basis of epidemiological and in vitro radiobiological studies. Data from various experimental studies for chromosome aberrations and cell transformation in human lymphocytes and from epidemiological studies of the Japanese A-bomb survivors, patients medically exposed to radiation for diagnostic and therapeutic procedures, and occupational exposures of nuclear workers are considered. On the basis of in vitro cellular radiobiology, there is considerable evidence that the relative biological effectiveness (RBE) of high-energy low-LET radiation (gamma radiation, electrons) is less than that of low-energy low-LET radiation (x-rays, betas). This is a factor of about 3 to 4 for 29 kVp x-rays (e.g. as in diagnostic radiation exposures of the female breast) and for tritium beta-rays (encountered in parts of the nuclear industry) relative to Co-60 gamma radiation and 2-5 MeV gamma-rays (as received by the Japanese A-bomb survivors). In epidemiological studies, although for thyroid and breast cancer there appears to be a small tendency for the excess relative risks to decrease as the radiation energy increases for low-LET radiations, it is not statistically feasible to draw any conclusion regarding an underlying dependence of cancer risk on LET for the nominally low-LET radiations.
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Affiliation(s)
- Nezahat Hunter
- Health Protection Agency, Radiation Protection Division, Oxford, UK.
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Kennedy DA, Lee T, Seely D. A Comparative Review of Thermography as a Breast Cancer Screening Technique. Integr Cancer Ther 2009; 8:9-16. [DOI: 10.1177/1534735408326171] [Citation(s) in RCA: 180] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Breast cancer is the most frequently diagnosed cancer of women in North America. Despite advances in treatment that have reduced mortality, breast cancer remains the second leading cause of cancer induced death. Several well established tools are used to screen for breast cancer including clinical breast exams, mammograms, and ultrasound. Thermography was first introduced as a screening tool in 1956 and was initially well accepted. However, after a 1977 study found thermography to lag behind other screening tools, the medical community lost interest in this diagnostic approach. This review discusses each screening tool with a focus brought to thermography. No single tool provides excellent predictability; however, a combination that incorporates thermography may boost both sensitivity and specificity. In light of technological advances and maturation of the thermographic industry, additional research is required to confirm the potential of this technology to provide an effective non-invasive, low risk adjunctive tool for the early detection of breast cancer.
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Affiliation(s)
- Deborah A. Kennedy
- Department of Research and Clinical Epidemiology, The Canadian College of Naturopathic Medicine, Toronto, Ontario, Canada
| | - Tanya Lee
- Department of Research and Clinical Epidemiology, The Canadian College of Naturopathic Medicine, Toronto, Ontario, Canada
| | - Dugald Seely
- Department of Research and Clinical Epidemiology, The Canadian College of Naturopathic Medicine, Toronto, Ontario, Canada,
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Leonard BE, Leonard VF. Mammogram and diagnostic X-rays--evidence of protective Bystander, Adaptive Response (AR) radio-protection and AR retention at high dose levels. Int J Radiat Biol 2009; 84:885-99. [PMID: 19016137 DOI: 10.1080/09553000802460115] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
PURPOSE The recently published dose response data by Dr Redpath's research group for low energy (30 kVp) mammography X-rays, displaying Adaptive Response (AR) radio-protective behavior, is significant for millions of American women that undergo annual breast cancer screening. We here, using the recently developed Microdose Model that encompasses the Bystander Effect (BE) and AR behavior, examine the data for BE, AR and high radiation domination by the priming radiations high dose Direct Damage. RESULTS The dose response is divided into three regions, Bystander Effect Region, Adaptive Response Region and Direct Damage Region (with possible retention of the AR protection). The Bystander Effect Region is below the microdose Specific Energy deposition for single photon induced charged particle traversals through the cell nucleus (the microdose Specific Energy Deposition per Traversal value = < z1 > = 0.638 cGy per Hit). Strong evidence is shown that a protective BE of about 50% occurs at a very low dose of 0.054 cGy, the BE is depleted reverting the response back to nearly the zero dose control value at 0.27 cGy, a 42% AR protection then is developed at 1.08 cGy and then the Direct Damage increasingly begins to dominate in the range from 5.4-21.6 cGy. Using the precise Method of Maximum Likelihood Estimator (MLE), the high dose Direct Damage Region is examined. We show that to the dose of 21.6 cGy the AR protection is retained in spite of the significant Direct Damage. We apply the same MLE analysis to the Redpath data for 137Cs gammas and find that the AR protection is completely dissipated at high Direct Damage inducing doses of 100 cGy. CONCLUSIONS The model shows that a protective BE of about 50% occurs at a low factor of 12 below single tracks traversals where less than 10% of the cell nuclei have been hit. Poisson distributed single tracks activates the 42% AR protection. The AR protection is retained at high dose but one needs to understand why 137Cs does not. Other Redpath group AR data sets for 137Cs, 232 MeV protons, and brachytherapy 125I photons did not reveal BE since the lowest data points were above the < z1 > for the radiations, but diagnostic X-rays do.
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Affiliation(s)
- Bobby E Leonard
- International Academy of Hi-Tech Services, Inc., Severna Park, Maryland 21146, USA.
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Leonard BE. "Protective bystander effects simulated with the state-vector model"--HeLa x skin exposure to Cs not protective bystander response but mammogram and diagnostic X-rays are. Dose Response 2008; 6:272-82. [PMID: 18846260 DOI: 10.2203/dose-response.07-031.leonard] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
The recent Dose Response journal article "Protective Bystander Effects Simulated with the State-Vector Model" (Schollnberger and Eckl 2007) identified the suppressive (below natural occurring, zero primer dose, spontaneous level) dose response for HeLa x skin exposure to (137)Cs gamma rays (Redpath et al 2001) as a protective Bystander Effect (BE) behavior. I had previously analyzed the Redpath et al (2001) data with a Microdose Model and conclusively showed that the suppressive response was from Adaptive Response (AR) radio-protection (Leonard 2005, 2007a). The significance of my microdose analysis has been that low LET radiation induced single (i.e. only one) charged particle traversals through a cell can initiate a Poisson distributed activation of AR radio-protection. The purpose of this correspondence is to clarify the distinctions relative to the BE and the AR behaviors for the Redpath groups (137)Cs data, show conversely however that the Redpath group data for mammography (Ko et al 2004) and diagnostic (Redpath et al 2003) X-rays do conclusively reflect protective bystander behavior and also herein emphasize the need for radio-biologist to apply microdosimetry in planning and analyzing their experiments for BE and AR. Whether we are adamantly pro-LNT, adamantly anti-LNT or, like most of us, just simple scientists searching for the truth in radio-biology, it is important that we accurately identify our results, especially when related to the LNT hypothesis controversy.
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Mestres M, Caballín MR, Barrios L, Ribas M, Barquinero JF. RBE of X Rays of Different Energies: A Cytogenetic Evaluation by FISH. Radiat Res 2008; 170:93-100. [DOI: 10.1667/rr1280.1] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2007] [Accepted: 02/27/2008] [Indexed: 11/03/2022]
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Leonard BE. Common sense about the linear no-threshold controversy-give the general public a break. Radiat Res 2008; 169:245-6; author reply 246-7. [PMID: 18220465 DOI: 10.1667/rr1123.1b] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2007] [Indexed: 11/03/2022]
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Leonard BE. A review: Development of a microdose model for analysis of adaptive response and bystander dose response behavior. Dose Response 2008; 6:113-83. [PMID: 18648579 DOI: 10.2203/dose-response.07-027.leonard] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Prior work has provided incremental phases to a microdosimetry modeling program to describe the dose response behavior of the radio-protective adaptive response effect. We have here consolidated these prior works (Leonard 2000, 2005, 2007a, 2007b, 2007c) to provide a composite, comprehensive Microdose Model that is also herein modified to include the bystander effect. The nomenclature for the model is also standardized for the benefit of the experimental cellular radio-biologist. It extends the prior work to explicitly encompass separately the analysis of experimental data that is 1.) only dose dependent and reflecting only adaptive response radio-protection, 2.) both dose and dose-rate dependent data and reflecting only adaptive response radio-protection for spontaneous and challenge dose damage, 3.) only dose dependent data and reflecting both bystander deleterious damage and adaptive response radio-protection (AR-BE model). The Appendix cites the various applications of the model. Here we have used the Microdose Model to analyze the, much more human risk significant, Elmore et al (2006) data for the dose and dose rate influence on the adaptive response radio-protective behavior of HeLa x Skin cells for naturally occurring, spontaneous chromosome damage from a Brachytherapy type (125)I photon radiation source. We have also applied the AR-BE Microdose Model to the Chromosome inversion data of Hooker et al (2004) reflecting both low LET bystander and adaptive response effects. The micro-beam facility data of Miller et al (1999), Nagasawa and Little (1999) and Zhou et al (2003) is also examined. For the Zhou et al (2003) data, we use the AR-BE model to estimate the threshold for adaptive response reduction of the bystander effect. The mammogram and diagnostic X-ray induction of AR and protective BE are observed. We show that bystander damage is reduced in the similar manner as spontaneous and challenge dose damage as shown by the Azzam et al (1996) data. We cite primary unresolved questions regarding adaptive response behavior and bystander behavior. The five features of major significance provided by the Microdose Model so far are 1. Single Specific Energy Hits initiate Adaptive Response. 2. Mammogram and diagnostic X-rays induce a protective Bystander Effect as well as Adaptive Response radio-protection. 3. For mammogram X-rays the Adaptive Response protection is retained at high primer dose levels. 4. The dose range of the AR protection depends on the value of the Specific Energy per Hit, 1 >. 5. Alpha particle induced deleterious Bystander damage is modulated by low LET radiation.
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Affiliation(s)
- Bobby E Leonard
- International Academy, 693 Wellerburn Road, Severna Park, MD 21146, USA.
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Ma H, Hill CK, Bernstein L, Ursin G. Low-dose medical radiation exposure and breast cancer risk in women under age 50 years overall and by estrogen and progesterone receptor status: results from a case-control and a case-case comparison. Breast Cancer Res Treat 2007; 109:77-90. [PMID: 17616809 DOI: 10.1007/s10549-007-9625-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2007] [Accepted: 05/16/2007] [Indexed: 11/30/2022]
Abstract
Although moderate to high-dose ionizing radiation exposure is an established risk factor for breast cancer, the effect of low-dose radiation exposure has not been clarified by epidemiological data. We evaluated the effect of low-dose radiation from medical procedures on risk of breast cancer overall and by joint estrogen and progesterone receptor (ER/PR) status in 1,742 population-based case patients aged 20-49 years and 441 control subjects identified from neighbourhoods of case patients in Los Angeles County. After excluding radiation exposures in the 5 years prior to case's diagnosis or control's initial household contact date we found an elevated breast cancer risk among women who reported having had multiple chest X-rays (Ptrend=0.0007) or 7 or more mammograms (odds ratio [OR]=1.80, 95% confidence interval [CI]=0.95-3.42). Risk was also increased among women who received dental X-rays without lead apron protection before age 20 years (OR=1.81, 95% CI=1.13-2.90). Women, who had their first exposure to these medical radiation procedures during childhood, had a greater increase in risk than those who were first exposed at older ages. Although not statistically significantly different, risk estimates were somewhat stronger for nulliparous than for parous women. We found no effect modification by ER/PR status. In conclusion, our findings support the hypothesis that low-dose ionizing radiation, and particularly exposures during childhood, increase breast cancer risk.
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Affiliation(s)
- Huiyan Ma
- Institute for Health Promotion and Disease Prevention Research, Keck School of Medicine, University of Southern California, 1000 South Fremont Avenue, Unit 8, Alhambra, CA 91803, USA.
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19
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Lee CI, Flaster HV, Haims AH, Monico EP, Forman HP. Diagnostic CT Scans: Institutional Informed Consent Guidelines and Practices at Academic Medical Centers. AJR Am J Roentgenol 2006; 187:282-7. [PMID: 16861528 DOI: 10.2214/ajr.05.0813] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
OBJECTIVE The purpose of this article is to characterize current informed consent practices for diagnostic CT scans at U.S. academic medical centers. MATERIALS AND METHODS We surveyed 113 radiology chairpersons associated with U.S. academic medical centers using a survey approved by our institutional review board. The need for informed consent for this study was waived. Chairpersons were asked if their institutions have guidelines for nonemergent CT scans (by whom; oral and/or written), if patients are informed of the purpose of their scans (by whom), what specific risks are outlined (allergic reaction, radiation risk and dose, others; by whom), and if patients are informed of alternatives to CT. RESULTS The study response rate was 81% (91/113). Of the respondents, two thirds (60/90) currently have guidelines for informed consent regarding CT scans. Radiology technologists were most likely to inform patients about CT (38/60, 63%) and possible risks (52/91, 57%), whereas ordering physicians were most likely to inform patients about CT's purpose (37/66, 56%). Fifty-two percent (30/58) of sites provided verbal information and 5% (3/58) provided information in written form. Possible allergic reaction to dye was explained at 84% (76/91) of sites, and possible radiation risk was explained at 15% (14/91) of sites. Nine percent (8/88) of sites informed patients of alternatives to CT. CONCLUSION Radiology technologists are more likely to inform patients about CT and associated risks than their physician counterparts. Although most academic medical centers currently have guidelines for informed consent regarding CT, only a minority of institutions inform patients about possible radiation risks and alternatives to CT.
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Affiliation(s)
- Christoph I Lee
- Department of Diagnostic Radiology, Yale University School of Medicine 333 Cedar Street, TE-2, New Haven, CT 06510, USA
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20
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Abstract
The major health risk associated with low photon energy imaging is thought to be the induction of cancer as a consequence of the radiation exposure and this is the focus of this paper. Low photon energy imaging typically involves exposure to a low dose (<50 mGy) of low linear energy transfer (LET) radiation delivered at high dose-rate. Since epidemiologic data cannot provide an accurate assessment of risk at the doses used in imaging, risk estimates are currently made by fitting a linear response to intermediate and high dose data for cancer induction in radiation-exposed human populations. This method assumes a linear no-threshold (LNT) response and implies that no dose of radiation is safe. This assumption is not borne out by many laboratory studies of cancer-related endpoints that would suggest that the risk at low doses is much less than would be estimated from linear extrapolation from intermediate to high doses. It is also well recognised that the dose-response from many epidemiologic studies could equally well be fit by threshold models. Through the study of radiation-induced neoplastic transformation in vitro J-shaped dose-response curves for a variety of low LET radiations, including those used in low photon energy imaging, have been demonstrated. The relative risks calculated from this data compare remarkably well with those for breast cancer and leukemia incidence in radiation-exposed populations. From this it is concluded that the LNT hypothesis is likely to overestimate the risk of cancer induction by low photon energy imaging, at least for certain tumors.
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Affiliation(s)
- J L Redpath
- Department of Radiation Oncology, School of Medicine, University of California Irvine, Irvine, CA 92697, USA.
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Reniers B, Verhaegen F. The microdosimetry of low-energy photons in radiotherapy. RADIATION PROTECTION DOSIMETRY 2006; 122:401-3. [PMID: 17287204 DOI: 10.1093/rpd/ncl488] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Low energy photons are more and more in use in clinical practice, for treatment in radiotherapy as well as for imaging purposes. Their relative biological effectiveness is however still debated. In this paper, some microdosimetric parameters have been calculated for different sources: (125)I, (103)Pd, (131)Cs, an electronic brachytherapy source and various clinical mammography X-ray qualities. These parameters have been used to deduce the quality factors as defined in ICRU 40.
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Affiliation(s)
- B Reniers
- Hôpital Maisonneuve-Rosemont, Montréal, Quebec, Canada.
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Delis H, Spyrou G, Panayiotakis G, Tzanakos G. DOSIS: a Monte Carlo simulation program for dose related studies in mammography. Eur J Radiol 2005; 54:371-6. [PMID: 15899338 DOI: 10.1016/j.ejrad.2004.07.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2004] [Revised: 07/27/2004] [Accepted: 07/29/2004] [Indexed: 11/18/2022]
Abstract
Dosimetric studies in mammography are addressed by means of a Monte Carlo simulation program. The core of this program (DOSIS: dosimetry simulation studies) is a simulation model developed using FORTRAN 90, enriched with a graphical user interface developed in MS Visual Basic. User defined mammographic technique parameters affecting breast dose are imported to the simulation model and the produced results are provided by means of both absolute (surface dose, exposure at detector plane) and relative quantities (percentage depth dose, isodose curves). The program functionality has been demonstrated in the evaluation of various mammographic examination techniques. Specifically, the influence of tube voltage and filtration on the surface dose and the exposure at detector plane has been studied utilizing a water phantom. Increase of tube voltage from 25 to 30 kVp for a Mo/Mo system resulted in a 42% decrease of the surface dose for a thick breast (6 cm), without changing the exposure at the detector plane. Use of 1.02 mm Al filter for a W anode system operating at 30 kVp resulted in a 19.1% decrease of the surface dose delivered to a 5 cm water equivalent breast. Overall, W/Al systems appear to have improved dosimetric performance, resulting up to a 65% decrease of surface dose compared to Mo/Mo systems, for identical exposures at the detector plane and breast thicknesses.
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Affiliation(s)
- H Delis
- Department of Medical Physics, School of Medicine, University of Patras, 26500 Patras, Greece
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Abstract
Most Americans clearly believe that routine screening mammography is beneficial. Given its widespread acceptance, it is useful to consider what the downsides of mammography screening are so that patients are fully informed in the decisions they make. This article lists some less well-recognized risks of mammography, such as false negatives and their accompanying false reassurance, as well as the direct and indirect costs to women and society. Three important downsides-radiation hazard, overdiagnosis of breast cancer, and the paradoxical increase in breast cancer mortality observed in screened women compared to controls age 40-49 years-are addressed. The article also considers the reasons that women are poorly informed about the downsides of mammography. There is, however, agreement that early diagnosis and treatment are important, and that new methods to reduce breast cancer deaths must be sought.
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Affiliation(s)
- Cornelia J Baines
- Department of Public Health Sciences, University of Toronto, Toronto, Ontario, Canada.
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Ko SJ, Liao XY, Molloi S, Elmore E, Redpath JL. Neoplastic TransformationIn Vitroafter Exposure to Low Doses of Mammographic-Energy X Rays: Quantitative and Mechanistic Aspects. Radiat Res 2004; 162:646-54. [PMID: 15548114 DOI: 10.1667/rr3277] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The induction of neoplastic transformation in vitro after exposure of HeLa x skin fibroblast hybrid cells to low doses of mammography-energy (28 kVp) X rays has been studied. The data indicate no evidence of an increase in transformation frequency over the range 0.05 to 22 cGy, and doses in the range 0.05 to 1.1 cGy may result in suppression of transformation frequencies to levels below that seen spontaneously. This finding is not consistent with a linear, no-threshold dose- response curve. The dose range at which possible suppression is evident includes doses typically experienced in mammographic examination of the human breast. Experiments are described that attempt to elucidate any possible role of bystander effects in modulating this low-dose radiation response. Not unexpectedly, inhibition of gap junction intercellular communication (GJIC) with the inhibitor lindane did not result in any significant alteration of transformation frequencies seen at doses of 0.27 or 5.4 cGy in these subconfluent cultures. Furthermore, no evidence of a bystander effect associated with factors secreted into the extracellular medium was seen in medium transfer experiments. Thus, in this system and under the experimental conditions used, bystander effects would not appear to be playing a major role in modulating the shape of the dose-response curve.
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Affiliation(s)
- S J Ko
- Department of Radiation Oncology, University of California Irvine, Irvine, California 92697, USA
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25
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Heyes GJ, Mill AJ. The neoplastic transformation potential of mammography X rays and atomic bomb spectrum radiation. Radiat Res 2004; 162:120-7. [PMID: 15387138 DOI: 10.1667/rr3212] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Considerable controversy currently exists regarding the biological effectiveness of 29 kVp X rays which are used for mammography screening. This issue must be resolved to enable proper evaluation of radiation risks from breast screening. Here a definitive assessment of the biological effectiveness of 29 kVp X rays compared to the quality of radiation to which the atomic bomb survivors were exposed is presented for the first time. The standard radiation sources used were (a) an atomic bomb simulation spectrum and (b) 2.2 MeV electrons from a strontium-90/yttrium-90 (90Sr/90Y) radioactive source. The biological end point used was neoplastic transformation in vitro in CGL1 (HeLa x human fibroblast hybrid) cells. No significant difference was observed for the biological effectiveness of the two high-energy sources for neoplastic transformation. A limiting relative biological effectiveness (RBE(M)) of 4.42 +/- 2.02 was observed for neoplastic transformation by 29 kVp X rays compared to these two sources. This compares with values of 4.67 +/- 3.93 calculated from previously published data and 3.58 +/- 1.77 when the reference radiation was 200 and 220 kVp X rays. This suggests that the risks associated with mammography screening may be approximately five times higher than previously assumed and that the risk-benefit relationship of mammography exposures may need to be re-examined.
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Affiliation(s)
- G J Heyes
- Radiation Biophysics Group, School of Physics and Astronomy, The University of Birmingham, Birmingham B15 2TT, United Kingdom.
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Abstract
OBJECTIVES To highlight areas where persons who undergo BRCA1/2 mutation testing may benefit from psychosocial or behavioral support and intervention. DATA SOURCES Published scientific literature, cal, and research experiences. CONCLUSION Key psychosocial areas that deserve attention by clinicians and researchers include: indeterminate or inconclusive test results, selection of risk management strategies in unaffected BRCA1/2 mutation carriers, and genetic testing in minority communities. IMPLICATIONS FOR NURSING PRACTICE By addressing the psychosocial issues faced by patients undergoing genetic testing for cancer, nurses have the potential to maximize opportunities for prevention, early detection, and healthy coping.
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Affiliation(s)
- Susan Thomas Vadaparampil
- H. Lee Moffitt Cancer Center & Research Institute, Department of Interdisciplinary Oncology, Health Outcomes and Behavior Program, Tampa, FL, USA
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Verhaegen F, Reniers B. Microdosimetric Analysis of Various Mammography Spectra: Lineal Energy Distributions and Ionization Cluster Analysis. Radiat Res 2004; 162:592-9. [PMID: 15624315 DOI: 10.1667/rr3246] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
In view of recent recommendations on the frequency and the starting age of mammography screening in healthy women, it is desirable to quantify the enhanced relative biological effectiveness (RBE) of mammography X rays compared to hard X rays. While there is little doubt that the former are more potent in inducing biological damage than the latter, the magnitude of the effect is still hotly debated in the literature. We used Monte Carlo simulations and track structure analysis in micrometer and nanometer volumes to investigate differences in distributions of lineal energy and ionization clusters for a range of mammography X-ray qualities. Dose-averaged lineal energies, (yD), in breast tissue for various mammography qualities were found to result in quality factors about 40% higher than unity. Among the various mammography qualities studied, the popular molybdenum/molybdenum target/filter combination was found to have the highest (yD) in 1-microm spheres (about 5.0 keV/microm near the entrance surface of breast tissue). In 10-nm radius spheres, the mean ionization cluster order was found to be about 35% higher in mammography X rays compared to 300 keV electrons (roughly representing 60Co or 192Ir photon radiation). In even smaller spheres (2 nm radius), no significant differences were observed for the mean ionization cluster order between mammography X rays and 300 keV electrons. We conclude that the potential of mammography X rays to induce biological damage is probably not much higher than a factor of two compared to hard X rays.
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Affiliation(s)
- F Verhaegen
- Medical Physics Department, McGill University, 1650 Cedar Avenue, Montreal, Quebec, H3G 1A4, Canada.
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28
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Abstract
The main risks and other adverse consequences from screening mammography include discomfort from breast compression, patient recall for additional imaging, and false positive biopsies. Although these risks affect a larger number of women than those who benefit from screening, the risks are less consequential than the life-sparing benefits from early detection. Radiation risk, even for multiple screenings, is negligible at current mammography doses. Anxiety before screening or resulting from supplementary imaging work-up, short-term follow-up, cyst aspiration, and biopsy has not dampened the enthusiasm of most women for the value of early detection.
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Affiliation(s)
- Stephen A Feig
- Department of Radiology, The Mount Sinai Hospital, 1 Gustave L. Levy Place, New York, NY 10029-6574, USA.
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29
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Brenner DJ. Radiation risks potentially associated with low-dose CT screening of adult smokers for lung cancer. Radiology 2004; 231:440-5. [PMID: 15128988 DOI: 10.1148/radiol.2312030880] [Citation(s) in RCA: 294] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
PURPOSE To estimate the radiation-related lung cancer risks associated with annual low-dose computed tomographic (CT) lung screening in adult smokers and former smokers, and to establish a baseline risk that the potential benefits of such screening should exceed. MATERIALS AND METHODS The estimated lung radiation dose from low-dose CT lung examinations corresponds to a dose range for which there is direct evidence of increased cancer risk in atomic bomb survivors. Estimated dose-, sex-, and smoking status-dependent excess relative risks of lung cancer were derived from cancer incidence data for atomic bomb survivors and used to calculate the excess lung cancer risks associated with a single CT lung examination at a given age in a U.S. population. From these, the overall radiation risks associated with annual CT lung screening were estimated. RESULTS A 50-year-old female smoker who undergoes annual CT lung screening until age 75 would incur an estimated radiation-related lung cancer risk of 0.85%, in addition to her otherwise expected lung cancer risk of approximately 17%. The radiation-associated cancer risk to other organs would be far lower. If 50% of all current and former smokers in the U.S. population aged 50-75 years received annual CT screening, the estimated number of lung cancers associated with radiation from screening would be approximately 36,000, a 1.8% (95% credibility interval: 0.5%, 5.5%) increase over the otherwise expected number. CONCLUSION Given the estimated upper limit of a 5.5% increase in lung cancer risk attributable to annual CT-related radiation exposure, a mortality benefit of considerably more than 5% may be necessary to outweigh the potential radiation risks.
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Affiliation(s)
- David J Brenner
- Center for Radiological Research, Columbia University, 630 W 168th St, New York, NY 10032, USA.
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Relative biological effectiveness (RBE), quality factor (Q), and radiation weighting factor (w(R)). A report of the International Commission on Radiological Protection. Ann ICRP 2004; 33:1-117. [PMID: 14614921 DOI: 10.1016/s0146-6453(03)00024-1] [Citation(s) in RCA: 165] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The effect of ionising radiation is influenced by the dose, the dose rate, and the quality of the radiation. Before 1990, dose-equivalent quantities were defined in terms of a quality factor, Q(L), that was applied to the absorbed dose at a point in order to take into account the differences in the effects of different types of radiation. In its 1990 recommendations, the ICRP introduced a modified concept. For radiological protection purposes, the absorbed dose is averaged over an organ or tissue, T, and this absorbed dose average is weighted for the radiation quality in terms of the radiation weighting factor, w(R), for the type and energy of radiation incident on the body. The resulting weighted dose is designated as the organ- or tissue-equivalent dose, H(T). The sum of the organ-equivalent doses weighted by the ICRP organ-weighting factors, w(T), is termed the effective dose, E. Measurements can be performed in terms of the operational quantities, ambient dose equivalent, and personal dose equivalent. These quantities continue to be defined in terms of the absorbed dose at the reference point weighted by Q(L). The values for w(R) and Q(L) in the 1990 recommendations were based on a review of the biological and other information available, but the underlying relative biological effectiveness (RBE) values and the choice of w(R) values were not elaborated in detail. Since 1990, there have been substantial developments in biological and dosimetric knowledge that justify a re-appraisal of w(R) values and how they may be derived. This re-appraisal is the principal objective of the present report. The report discusses in some detail the values of RBE with regard to stochastic effects, which are central to the selection of w(R) and Q(L). Those factors and the dose-equivalent quantities are restricted to the dose range of interest to radiation protection, i.e. to the general magnitude of the dose limits. In special circumstances where one deals with higher doses that can cause deterministic effects, the relevant RBE values are applied to obtain a weighted dose. The question of RBE values for deterministic effects and how they should be used is also treated in the report, but it is an issue that will demand further investigations. This report is one of a set of documents being developed by ICRP Committees in order to advise the ICRP on the formulation of its next Recommendations for Radiological Protection. Thus, while the report suggests some future modifications, the w(R) values given in the 1990 recommendations are still valid at this time. The report provides a scientific background and suggests how the ICRP might proceed with the derivation of w(R) values ahead of its forthcoming recommendations.
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Schmid E, Krumrey M, Ulm G, Roos H, Regulla D. The Maximum Low-Dose RBE of 17.4 and 40 keV Monochromatic X Rays for the Induction of Dicentric Chromosomes in Human Peripheral Lymphocytes. Radiat Res 2003; 160:499-504. [PMID: 14565834 DOI: 10.1667/rr3070] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Schmid et al. recently reported on the maximum low-dose RBE for mammography X rays (29 kV) for the induction of dicentrics in human lymphocytes. To obtain additional information on the RBE for this radiation quality, experiments with monochromatized synchrotron radiation were performed. Monochromatic 17.4 keV X rays were chosen for comparison with the diagnostic mammography X-ray spectrum to evaluate the spectral influence, while monochromatic 40 keV X rays represent a higher-energy reference radiation, within the experiment. The induction of dicentric chromosomes in human lymphocytes from one blood donor irradiated in vitro with 17.4 keV and 40 keV monochromatic X rays resulted in alpha coefficients of (3.44 +/- 0.87) x 10(-2) Gy(-1) and (2.37 +/- 0.93) x 10(-2) Gy(-1), respectively. These biological effects are only about half of the alpha coefficients reported earlier for exposure of blood from the same donor with the broad energy spectra of 29 kV X rays (mean energy of 17.4 keV) and 60 kV X rays (mean energy of 48 keV). A similar behavior is evident in terms of RBEM. Relative to weakly filtered 220 kV X rays, the RBEM for 17.4 and 40 keV monochromatic X rays is 0.86 +/- 0.23 and 0.59 +/- 0.24, respectively, which is in contrast to the RBEM of 1.64 +/- 0.27 for 29 kV X rays and 1.10 +/- 0.19 for 60 kV X rays. It is evident that the monochromatic radiations are less effective in inducing dicentric chromosomes than broad-spectrum X rays with the corresponding mean energy value. Therefore, it can be assumed that, for these X-ray qualities with broad energy spectra, a large fraction of the effects should be attributed predominantly to photons with energies well below the mean energy.
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Affiliation(s)
- E Schmid
- Institute of Radiobiology, GSF-National Research Center for Environment and Health, 85764 Neuherberg, Germany.
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Baines CJ. Mammography Screening: Are Women Really Giving Informed Consent? J Natl Cancer Inst 2003; 95:1508-11. [PMID: 14559870 DOI: 10.1093/jnci/djg026] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Cornelia J Baines
- Department of Public Health Sciences, University of Toronto, 12 Queen's Park Crescent W, Rm. 401C, Toronto, Ontario, Canada M5S 1A8.
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Kellerer AM, Chen J. Comparative microdosimetry of photoelectrons and Compton electrons: an analysis in terms of generalized proximity functions. Radiat Res 2003; 160:324-33. [PMID: 12926991 DOI: 10.1667/rr3036] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
A current discussion on mammography screening is focused on claims of high relative biological effectiveness (RBE) of mammography X rays compared to conventional 200 kV X rays. An earlier assessment in terms of the electron spectra of these radiations has led to the conclusion that the RBE is bound to be less than 2, regardless of specific model assumptions and the microdosimetric properties of electrons. The present study extends this result in terms of the microdosimetric proximity function, t(x), for electrons, which is essentially the spatial auto-correlation function of energy within particle tracks. If pairs of DNA lesions, e.g. chromosome breaks or deletions, bring about the observed damage, the value t(x) determines for a specified radiation the relative frequency of pairs of lesions a distance x apart. The effectiveness of the radiation is thus proportional to an average of the values of t(x) over the distances, x, for which lesions can combine. The analysis suggests that 15 keV electrons can have a low-dose relative biological effectiveness (RBE(M)) of 1.6 relative to 40 keV electrons if the interaction distances do not exceed about 1 micro m. An extension of the concept, the reduced proximity function, t(delta)(x), permits the inclusion of models with an energy threshold, such as delta = 100 eV, 500 eV or 2 keV, for the formation of each of the DNA lesions. This makes it possible to assess the potential impact of the Auger electrons which accompany most photoelectrons, but only a minority of the Compton electrons. It is found that the Auger electrons could make photoelectrons substantially more effective than Compton electrons at energies below 10 keV but not at energies above 15 keV. The conclusions obtained for the RBE of 15 keV electrons relative to 40 keV electrons will be roughly representative of the RBE of mammography X rays relative to conventional 200 kV X rays.
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