David A. Schauer

National Council on Radiation Protection and Measurements Report Shows Substantial Medical Exposure Increase

Americans were exposed to more than seven times as much ionizing radiation from diagnostic medical procedures in 2006 than they were in the early 1980s.

Dose Reconstruction for the Million Worker Study: Status and Guidelines

The primary aim of the epidemiologic study of one million U.S. radiation workers and veterans [the Million Worker Study (MWS)] is to provide scientifically valid information on the level of radiation risk when exposures are received gradually over time and not within seconds, as was the case for Japanese atomic bomb survivors. The primary outcome of the epidemiologic study is cancer mortality, but other causes of death such as cardiovascular disease and cerebrovascular disease will be evaluated. The success of the study is tied to the validity of the dose reconstruction approaches to provide realistic estimates of organ-specific radiation absorbed doses that are as accurate and precise as possible and to properly evaluate their accompanying uncertainties. The dosimetry aspects for the MWS are challenging in that they address diverse exposure scenarios for diverse occupational groups being studied over a period of up to 70 y. The dosimetric issues differ among the varied exposed populations that are considered: atomic veterans, U.S. Department of Energy workers exposed to both penetrating radiation and intakes of radionuclides, nuclear power plant workers, medical radiation workers, and industrial radiographers. While a major source of radiation exposure to the study population comes from external gamma- or x-ray sources, for some of the study groups, there is a meaningful component of radionuclide intakes that requires internal radiation dosimetry assessments. Scientific Committee 6-9 has been established by the National Council on Radiation Protection and Measurements (NCRP) to produce a report on the comprehensive organ dose assessment (including uncertainty analysis) for the MWS. The NCRP dosimetry report will cover the specifics of practical dose reconstruction for the ongoing epidemiologic studies with uncertainty analysis discussions and will be a specific application of the guidance provided in NCRP Report Nos. 158, 163, 164, and 171. The main role of the Committee is to provide guidelines to the various groups of dosimetrists involved in the MWS to ensure that certain dosimetry criteria are considered: calculation of annual absorbed doses in the organs of interest, separation of low and high linear-energy transfer components, evaluation of uncertainties, and quality assurance and quality control. It is recognized that the MWS and its approaches to dosimetry are a work in progress and that there will be flexibility and changes in direction as new information is obtained with regard to both dosimetry and the epidemiologic features of the study components. This paper focuses on the description of the various components of the MWS, the available dosimetry results, and the challenges that have been encountered. It is expected that the Committee will complete its report in 2016.

Applications of Justification and Optimization in Medical Imaging: Examples of Clinical Guidance for Computed Tomography Use in Emergency Medicine

Availability, reliability, and technical improvements have led to continued expansion of computed tomography (CT) imaging. During a CT scan, there is substantially more exposure to ionizing radiation than with conventional radiography. This has led to questions and critical conclusions about whether the continuous growth of CT scans should be subjected to review and potentially restraints or, at a minimum, closer investigation. This is particularly pertinent to populations in emergency departments, such as children and patients who receive repeated CT scans for benign diagnoses. During the last several decades, among national medical specialty organizations, the American College of Emergency Physicians and the American College of Radiology have each formed membership working groups to consider value, access, and expedience and to promote broad acceptance of CT protocols and procedures within their disciplines. Those efforts have had positive effects on the use criteria for CT by other physician groups, health insurance carriers, regulators, and legislators.

Does Security Screening with Backscatter X-Rays Do More Good than Harm?

The summation of trivial average risks over large populations or time periods into a single value produces a distorted image of risk, completely out of perspective with risks accepted every day, both voluntarily and involuntarily.

Optimizing radiation use during fluoroscopic procedures: proceedings from a multidisciplinary consensus panel.

James R. Duncan, MD, PhD, Stephen Balter, PhD, Gary J. Becker, MD, Jeffrey Brady, MD, MPH, James A. Brink, MD, Dorothy Bulas, MD, Mythreyi B. Chatfield, PhD, Simon Choi, PhD, MPH, Bairbre L. Connolly, MB, Robert G. Dixon, MD, Joel E. Gray, PhD, Stephen T. Kee, MD, Donald L. Miller, MD, Donald W. Robinson, LTC, MD, Mark J. Sands, MD, David A. Schauer, DSc, Joseph R. Steele, MD, Mandie Street, RT, Raymond H. Thornton, MD, and Robert A. Wise, MD

Dose coefficients for ICRP reference pediatric phantoms exposed to idealised external gamma fields

Organ and effective dose coefficients have been calculated for the International Commission on Radiological Protection (ICRP) reference pediatric phantoms externally exposed to mono-energetic photon radiation (x- and gamma-rays) from 0.01 to 20 MeV. Calculations used Monte Carlo radiation transport techniques. Organ dose coefficients, i.e., organ absorbed dose per unit air kerma (Gy/Gy), were calculated for 28 organs and tissues including the active marrow (or red bone marrow) for 10 phantoms (newborn, 1 year, 5 year, 10 year, and 15 year old male and female). Radiation exposure was simulated for 33 photon mono-energies (0.01-20 MeV) in six irradiation geometries: antero-posterior (AP), postero-anterior, right lateral, left lateral, rotational, and isotropic. Organ dose coefficients for different ages closely agree in AP geometry as illustrated by a small coefficient of variation (COV) (the ratio of the standard deviation to the mean) of 4.4% for the lungs. The small COVs shown for the effective dose and AP irradiation geometry reflect that most of the radiosensitive organs are located in the front part of the human body. In contrast, we observed differences in organ dose coefficients across the ages of the phantoms for lateral irradiation geometries. We also observed variation in dose coefficients across different irradiation geometries, where the COV ranges from 18% (newborn male) to 38% (15 year old male) across idealised whole body irradiation geometries for the major organs (active marrow, colon, lung, stomach wall, and breast) at the energy of 0.1 MeV. Effective dose coefficients were also derived for applicable situations, e.g., radiation protection or risk projection. Our results are the first comprehensive set of organ and effective dose coefficients applicable to children and adolescents based on the newly adopted ICRP pediatric phantom series. Our tabulated organ and effective dose coefficients for these next-generation phantoms should provide more accurate estimates of organ doses in children than earlier dosimetric models allowed.

Neutron Metrology in the United States—Where We’ve Been, Where We Are Now and What We Need to Do Moving Forward

Neutron metrology in the United States must be based on traceability to standards maintained by the National Institute of Standards and Technology (NIST). This article reviews the history of NISTs neutron-metrology efforts, the loss of those capabilities, and attempts to restore them. Recommendations are made to ensure that neutron dosimetry performed in the United States meets the requirements set forth by the International Standards Organization and other international and national authorities.

Warren Keith Sinclair (1924 to 2014).

DR.WARREN K. Sinclair, a giant in the field of radiation proand two brothers. He was a 1941 graduate of Otago Boys’ tection, science and medicine, passed away on 14May 2014 at 90 y of age, following a stroke the preceding day. Warren was one of the founding fathers of modern radiation protection, an outstanding teacher, a superb radiation physicist, and a good friend and colleague. Our world is smaller with his passing, but we are all better and grateful for his rich life, leadership, and friendship. Warren Sinclair was born on 9March 1924 in Dunedin, New Zealand. He was one of six children, with three sisters High School in Dunedin. Warren was an accomplished rugby player during his high school and university days. During 1943, while a student at the University of Otago, he served in the New Zealand Army and manned an antiaircraft battery near Christchurch Harbor waiting to fend off the Japanese, who never came. His first professional job was for the New Zealand Government after earning his B.Sc. in 1944, but he was sent back to Otago University the next year by Ernie Marsden (a colleague of Ernest Rutherford) to study for his M.S. in physics. After graduating with first class honors in physics in 1945, Warren was appointed the first hospital physicist in New Zealand in his hometown of Dunedin. After working in radiotherapy physics with Dr. Peter Jerram (radiotherapist), he