Daphnee Villoing*, R Craig Yoder, Christopher Passmore, Marie-Odile Bernier, Martha Linet, Cari M Kitahara. Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Rockville, MD, USA Minor Outlying Islands; Consultant, Weddington, NC, USA Minor Outlying Islands; Landauer, Inc., Glenwood, IL, USA Minor Outlying Islands; Institut de Radioprotection et de Sureté Nucléaire, Fontenay-aux-roses, France

Daphnee Villoing*, R Craig Yoder, Christopher Passmore, Marie-Odile Bernier, Martha Linet, Cari M Kitahara. Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Rockville, MD, USA Minor Outlying Islands; Consultant, Weddington, NC, USA Minor Outlying Islands; Landauer, Inc., Glenwood, IL, USA Minor Outlying Islands; Institut de Radioprotection et de Sureté Nucléaire, Fontenay-aux-roses, France

Background The reconstruction of lifetime radiation doses for medical workers presents special challenges not commonly encountered for the other worker cohorts comprising the Million Worker Study. Methods The selection of approximately 175,000 medical radiation workers relies on using estimates of lifetime and annual personal monitoring results collected since 1977. Approaches have been created to adjust the monitoring results so that mean organ absorbed doses can be estimated. Results Changes in medical technology and practices have altered the radiation exposure environments to which a worker may have been exposed during their career. Other temporal factors include shifts in regulatory requirements that influenced the conduct of radiation monitoring and the changes in the measured dose quantities. Conclusions The use of leaded aprons during exposure to lower energy X rays encountered in fluoroscopically based radiology adds complexity to account for the shielding of the organs located in the torso when dosimeters were worn over leaded aprons. Estimating doses to unshielded tissues such as the brain and lens of the eye become less challenging when dosimeters are worn at the collar above the apron. The absence of leaded aprons in the higher energy photon settings lead to a more straightforward process of relating dosimeter results to mean organ doses.

Purpose To summarize occupational badge doses recorded for a sample of U.S. nuclear medicine technologists. Materials and Methods Nine large U.S. medical institutions identified 208 former and current nuclear medicine technologists certified after 1979 and linked these individuals to historic badge dose records maintained by a commercial dosimetry company (Landauer), yielding a total of 2618 annual dose records. The distributions of annual and cumulative occupational doses were described by using summary statistics. Results Between 1992 and 2015, the median annual personal dose equivalent per nuclear medicine technologist was 2.18 mSv (interquartile range [IQR], 1.25-3.47 mSv; mean, 2.69 mSv). Median annual personal dose equivalents remained relatively constant over this period (range, 1.40-3.30 mSv), while maximum values generally increased over time (from 8.00 mSv in 1992 to 13.9 mSv in 2015). The median cumulative personal dose equivalent was 32.9 mSv (IQR, 18.1-65.5 mSv; mean, 51.4 mSv) for 45 technologists who had complete information and remained employed through 2015. Conclusion Occupational radiation doses were well below the established occupational limits and were consistent with those observed for nuclear medicine technologists worldwide and were greater than those observed for nuclear and general medical workers in the United States These results should be informative for radiation monitoring and safety efforts in nuclear medicine departments. © RSNA, 2018 Online supplemental material is available for this article.

This work investigates the applicability of using data from personal monitoring dosimeters to assess photon energies to which medical workers were exposed. Such determinations would be important for retrospective assessments of organ doses to be used in occupational radiation epidemiology studies, particularly in the absence of work history or other information regarding the energy of the radiation source. Monthly personal dose equivalents and filter ratios under two different metallic filters contained in the Luxel+® dosimeter were collected from Landauer, Inc. from 19 nuclear medicine (NM) technologists employed by three medical institutions, the institution A only performing traditional NM imaging (primarily using 99mTc) and institutions B and C also performing positron emission tomography (PET, using 18F). Calibration data of the Luxel+® dosimeter for various xray spectra were used to establish ranges of filter ratios from 1.1 to 1.6 for 99mTc and below 1.1 for 18F. Median filter ratios were 1.33 (Interquartile range (IQR), 0.15) for institution A, 1.08 (IQR, 0.16) for institution B, and 1.08 (IQR, 0.14) for institution C. The distributions of these filter ratios were statistically-significantly different between the institution A only performing traditional NM imaging and institutions B and C also performing PET imaging. In this proof-of-concept study, filter ratios from personal monitoring dosimeters were used to assess differences in photon energies to which NM technologists were exposed. Dosimeters from technologists only performing traditional NM procedures mostly showed Al/Cu filter ratios above 1.2, those likely performing only PET in a particular month had filter ratios below 1.1, and those which showed filter ratios between 1.1 and 1.2 likely came from technologists rotating between traditional NM and PET imaging in the same month. These results suggest that it is possible to distinguish technologists who only worked with higher-energy procedures versus those who only worked with other types of NM procedures.

Nuclear medicine techniques developed in the second half of the 20th century have become very sophisticated and have been used extensively in the diagnosis and treatment of disease. A surge of new dedicated radiopharmaceuticals and increased demand has led to a growing interest regarding increasing radiation exposure and possible associated health risks to the nuclear medicine technologists who perform these procedures. However, to date, very limited information has been provided on radiation doses received by nuclear medicine technologists. In this study, we collected annual and lifetime badge dose information for United States technologists certified in nuclear medicine between 1979 and 2015. Nine large US medical institutions from several geographical locations contributed information on 208 nuclear medicine technologists, linked to historical badge dose records maintained by a major commercial dosimetry company, yielding 2618 total dose records. The mean and median annual badge doses per technologist were 2.7 and 2.2 mSv, respectively, and more than 3% of the annual doses exceeded 10 mSv. The mean annual doses substantially increased around the year 2000, consistent with the expanded use of Positron Emission Tomography (PET). Mean and median lifetime doses of 51.4 and 32.9 mSv could be established for 45 technologists. Doses in this sample of nuclear medicine technologists were higher than expected, compared with previously published values for nuclear workers or radiologic technologists. These results suggest that nuclear medicine technologists may be one of the most highly-exposed radiation worker populations currently.

This paper describes the development of a new type of personal radiation dosimeter that combines the excellent features of optically stimulated luminescence (OSL) with the convenience of Panasonic type readers. The specification required for the badge in world-wide application is first discussed. The dosemeter is a Panasonic type dosemeter with OSL detectors replacing the thermoluminescence dosemeters (TLDs). The readers are modified, principally by using a LED array as the light source. Thus, we have been able to use an extensively tried and tested system with the minimum of modifications. The readers are computer controlled and can recognise the type of badge being read and the sensitivity of the OSL detectors. Two different badges have been developmened to meet the requirements for the American and European markets. The model 1 badge comprises an open window and filters of plastic, copper and lead. A linear algorithm is being developed for this badge. The model 2 badge comprises an open window and filters of plastic, copper and aluminium. The algorithm developed for this badge is function-based (branching). A full programme of type testing the badges has been undertaken. The newly developed system will enable us to expand the service options available to our customers. These will range from full service (supply of badges periodically to customers, receipt and readout through to record keeping) through to supply of equipment, badges and support so that customers can run their own in house service using OSL technology badges.