National Council on Radiation Protection and Measurements, Bethesda, MD
The author declare no conflicts of interest.
Supplemental Digital Content is available in the HTML and PDF versions of this article on the journal’s Web site ( www.health-physics.com).
(Manuscript accepted 29 August 2013)
Questions for Dr. Dauer
For the lens of the eye dose estimation, what percent reduction would you recommend following use of drop-down shielding and leaded glasses?
Seethornton and Dauer (2010) for a detailed review of lens dose reduction factors that depend upon orientation and type of procedure. According to NCRP Report No.168 (NCRP 2010), the use of leaded glasses alone can provide a reduction factor of ∼3–10, while suspended shields provide reductions of >25. In Thornton et al. above, suspended shields resulted in lens doses being routinely undetectable above background.
Do you have any advice on pregnant radiopharmaceutical workers?
Encourage workers to declare pregnancy, such as a woman who is an occupational radiation worker and has voluntarily informed her employer, in writing, of her pregnancy and the estimated conception date (USNRC 2013a). This will enable the employer, in conjunction with the radiation safety officer and supervisors, to evaluate historical dosimetry records and current work practices to ensure that the limits as noted in 10 CFR Part 20.1208 (USNRC 2013b) can be met. In many cases, “as low as reasonably achievable” (ALARA) optimization techniques (e.g., workload, distance, shielding) can be used as-needed in reducing dose to the embryo/fetus.
Can you show your radiochemical extremity/whole-body dose on a per megabecquerel of production? I would like to compare to my facility, and this seems like the “fairest” way
Good suggestion. We are pulling together 2 y worth of information and hope to publish such results within the next year.
How do you know your interventional radiology/interventional cardiology medical doctors are actually wearing their dosimeters for your data analysis? What percent of medical workers don’t wear badges some or all of the time because of fear that they will exceed limits and have to stop working?
We audit for compliance. Our interventional radiology/interventional cardiology medical doctors actually wear their dosimeters when they are in their fluoro/angio suites.
NCRP Report No.168 (NCRP 2010) has excellent recommendations with regard to auditing compliance. At any point in time, there are expected ranges of occupational dose for different job assignments. Doses to individuals outside of the expected dose ranges (either above OR below) should be investigated, as would sudden changes in an individual’s dosimeter readings.
This is an issue with adequacy of dosimeter wearing by interventional vascular/interventional cardiology staff. If most actually receive 30–50 mSv y−1 (lens of the eye dose), would 20 mSv y−1 create an operational “problem” in medical practice?
For our practice, the average lens dose equivalent (LDE) was 11 mSv y−1, and the median LDE was 7 mSv y−1. Therefore, most of our staff will likely be <20 mSv y−1 (International Commission on Radiological Protection limit). However, it is true that about 25% of our staff currently receive >20 mSv y−1 based on the current dosimetric methodology, whereby we assign LDE based on collar badge readings (NCRP 2010) for more information on LDE methods. Note that no “credit” has currently been incorporated for leaded glasses or other lens of the eye protection methods. This is something that needs to be evaluated further as well as additional optimization procedures (Dauer et al 2010; Thornton and Dauer 2010).
What specific safety procedures have been implemented for 89Zr?
Additional shielding for vials/syringes, reassessment of patient injection/resting area shielding adequacy, and as noted in the presentation, an activity level of 185 MBq requiring patient instructions.
QUESTIONS FOR JAMES BRINK
What goes into the decision to do or not to do computed tomography?
The decision to do computed tomography (CT) should be based primarily on the medical need. For indicated studies, the potential benefits greatly outweigh the potential risks. Zondervan et al. (2013) compared the mortality status among 22,000 CT scan patients between 18–35 y of age and found their mortality from their underlying medical conditions greatly exceeded their potential risk of fatal cancer induction from the ionizing radiation associated with their imaging procedures. Even for appropriate screening examinations such as CT colonography, Brenner and Georgsson (2005) concluded that the lifetime risk of colorectal cancer is 5–6%, whereas the potential risk of radiation-induced cancer from CT colonography is 0.14% for a 50-y-old individual, the age at which conventional colonoscopy is recommended (Brenner and Georgsson 2005). Thus, the potential benefit greatly outweighs the risk for this imaging application.
Should advanced nurse practitioners or physician assistants be permitted to prescribe diagnostic exams that use ionizing radiation?
Nurse practitioners and physician assistants are licensed, independent practitioners with the same ordering privileges for imaging examinations as physicians. In general, their training in the benefits and risks of diagnostic testing is sufficient to warrant these privileges.
What kind of patient dose controls exist for “virtual physical” centers, where people may get computed tomography “screenings” without their physician determining the exam is medically necessary? How does, or does not, this complement examinations in a medical setting, or are the scans having to be repeated? The concern is that it seems patient dose is not a consideration if the patient desires a scan and has the ability to pay for it. I do not mean this to be offensive—the growth of “couture” computed tomography/magnetic resonance imaging centers has increased rapidly and is targeted at the consumer as a means of “preventive detection.”
Whole-body computed tomography screening has been strongly renounced by several organizations, including the American College of Radiology and the U.S. Food and Drug Administration. I am not aware that this practice is on the rise, and I believe that the public is generally aware of the risks of this practice.
Introduction of Second Malignant Neoplasms and Cardiovascular Disease (Video 1:53, http://links.lww.com/HP/A32).
Brenner DJ, Georgsson MA . Mass screening with CT colonography: should the radiation exposure be of concern? Gastroenterol. 129: 328–337; 2005; .
Dauer LT, Thornton RH, Solomon SB, St Germain J . Unprotected operator eye lens doses in oncologic interventional radiology are clinically significant: estimation from patient kerma-area product data. J Vascular Intervent Radiol. 21: 1859–1861; 2010; .
Thornton RH, Dauer LT . Comparing strategies for IR eye protection in the interventional radiology suite. J Vascular Intervent Radiol. 21: 1703–1707; 2010; .
U.S. Nuclear Regulatory Commission. Standards for protection against radiation. Definitions. Washington, DC: U.S. Government Printing Office; 2013a; .
U.S. Nuclear Regulatory Commission; 10 CFR Part 20.1003
U.S. Nuclear Regulatory Commission. Standards for protection against radiation. Dose equivalent to an embryo/fetus. Washington, DC: U.S. Government Printing Office; 2013b; .
U.S. Nuclear Regulatory Commission; 10 CFR Part 20.1208
Zonderva RL, Hahn PF, Sadow CA, Liu B, Lee SI . Body CT scanning in young adults: examination indications, patient outcomes, and risk of radiation-induced cancer. Radiol. 267: 460–469; 2013; .