Single Session

[Schedule Grid]

TPM-A - Medical Health Physics 2

Woodrow Wilson A   14:30 - 16:45

Chair(s): Thomas Morgan and Andy Miller
TPM-A.1   14:30  Radiation Safety Perspectives from the Oversight of an Ambulance-Based Computed Tomography Unit and a Van Equipped with Dental X-ray Units JM Gutierrez*, UTHealth Houston

Abstract: In 2014, the UTHealth Houston McGovern Medical School deployed the first ambulance based mobile stroke unit in the United States equipped with a head computed tomography unit. Research and clinical care have revealed the treatment within the very first hours of symptom onset is key for ischemic stroke with recanalization of occluded arteries by thrombolysis with alteplase. Essentially, quick response is critical for improved patient outcomes. Computed tomography is one of the diagnostic tools to determine if this treatment path is appropriate. In 2023, the original ambulance based mobile stroke unit has been replaced. Additionally, the UTHealth Houston School of Dentistry expanded diagnostic dental care to underserved communities in 2002 with the mobile dental van equipped in 2003 with a dental radiographic unit. In late 2022, after 20 years of operation, the mobile dental van has been replaced with a state of the art new mobile dental van equipped with dental radiographic units to continue to provide dental care to underserved communities. This presentation will provide an overview from the radiation safety professional's perspective regarding x-ray registration permitting, routine safety surveillance, and regulatory inspections for these vehicles and the associated radiation producing devices. A summary and snapshots of the radiation safety support necessary for the safe operation of these vehicles will be shared both for the original vehicles and the new units recently brought into operation.

TPM-A.2   14:45  The Effects of Mobile Radiation Shielding on Scatter Radiation in the Cardiac Catheterization Laboratory DL Smith*, UAB ; E Caffrey, UAB; C Wilson, UAB

Abstract: The radiation dose measurements for staff members involved in cardiac catheterization laboratory (cath lab) procedures are generally among the highest in an entire hospital setting. Secondary radiation exposure in fluoroscopically guided intervention suites comes from leakage radiation of the x-ray tube and scattered radiation from the patient’s tissue in the primary beam. 0.5mm lead or lead equivalent aprons are currently the standard for radiation protection from this occupational exposure, but thinner lead aprons may provide adequate protection. Despite the widespread nature of this practice, lead or lead equivalent aprons are proven to contribute to back injuries among cath lab staff; lead or lead equivalent aprons also contribute to nonuniform dose distributions. The cause of these nonuniformities includes nonuniform radiation fields, differential shielding of different body parts from the radiation, and scattered radiation produced within the irradiated individual. Research has shown that mobile lead-lined barriers are acceptable for whole-body radiation protection, including the head and eyes. This research aims to determine the effect of a mobile radiation shielding system on scatter radiation from a patient. This will be conducted using an anthropomorphic phantom to create natural scatter radiation with and without the Rampart M1128 mobile radiation shield in place with the fluoroscopic tube at an upright angle and at a 30-degree left and right position to mimic practical fluoroscopic usage. Using a grid system, an ion chamber will be used to measure exposure rates at different locations in the cath lab. The results could be used to determine if the reduction of scatter radiation by the mobile radiation shield meets ALARA standards without using lead or lead equivalent aprons.

TPM-A.3   15:00  To inventory or not to inventory – protective apron integrity assessment process and documentation GM Sturchio*, Mayo Clinic ; JL Coder, Mayo Clinic

Abstract: The use of protective aprons in the diagnostic and interventional X-ray environment is a primary radiation protection intervention to mitigate personnel radiation exposure and to ensure that occupational radiation dose is as low as reasonably achievable. The routine assessment of protective apron integrity is necessary to ensure optimal radiation protection of staff, as well as provide comfort to the staff that the protective aprons are effective. This presentation details our annual process in evaluating protective apron integrity – from the initial contact with stakeholders, through the evaluation procedure including pass/fail criteria, and how we document successful passage of the evaluation. We present the derivation of our “tear area” rejection criterion underscoring the opportunity for site specific values to influence decisionmaking. We highlight the advantages of using readily visible colored tags to document successful passage of the integrity check both to the end user and the auditor. We examine the need for maintaining an inventory of protective aprons (within the framework of our process) from a radiation protection perspective and find it wanting. In addition, we discuss how the protective apron integrity assessment process is interwoven into our radiation safety training, radiation source permitting, and radiation source auditing programs (aka, safety management system).

TPM-A.4   15:15  Bulk vs. Unit-Dose Packaging of [F-18]FDG: Impact on Occupational Radiation Dose for Production and Imaging Personnel SM Moerlein*, Washington University in St. Louis ; J Lake, Washington University in St. Louis; M Amurao, Washington University in St. Louis; ML Nickels, Washington University in St. Louis

Abstract: Problem: [F-18]FDG is a cyclotron-produced radiopharmaceutical widely used for positron-emission tomography (PET) imaging. Initially, [F-18]FDG was produced in the cyclotron facility and transported in a shielded bulk vial to the imaging facility, where nuclear medicine imaging staff would withdraw individual patient doses (17 mCi) throughout the workday. To improve patient safety, it was decided to dispense individual patient doses in the cyclotron facility, and transport the shielded doses to the imaging facility. Our hypothesis is that the workflow change affected the occupational dose to production and imaging personnel differently. Production personnel are expected to have lower occupational doses if bulk packages of [F-18]FDG dosages are used, whereas imaging personnel are expected to have lower occupational doses if unit doses of [F-18]FDG are provided. Work conducted: We have examined the extremity and whole-body doses of employees involved with [F-18]FDG dose dispensing and those involved in [F-18]FDG imaging. Historical monthly whole-body and extremity (right/left ring) Landauer badge readings were compiled for 9 relevant cyclotron staff and 6 relevant nuclear medicine imaging staff. Data for up to 6 months was examined for the two groups before and after workflow change. Results: Although variability between individuals in each group was large, the occupational doses for the production group tended to be increased by the change to unit dosing, and doses to the imaging group tended to be decreased by the change. Variability of occupational doses in the production group was higher than the imaging group, an affect attributed to the different roles of staff involved in the dose dispensing and transport processes. Confounders to these results are the observation times, overlapping doses due to non-[F-18]FDG activities in each group, and turnover of staff during the observation interval. Conclusion: Change in the workflow with radioactive drugs may induce changes in individual occupational doses, and should be carefully evaluated. Adherence to ALARA may require the addition of dispensing staff to decrease individual doses, or investment in dose-drawing equipment to manage occupational doses.

TPM-A.5   15:30  BREAK

TPM-A.6   16:00  Radiation Protection Considerations for Cancer Patients with End-stage Renal Disease Receiving I-131 Treatment M Louis*, Georgia Institute of Technology ; EM Mate-Kole, Georgia Institute of Technology; L Aziz, Georgia Institute of Technology; SA Dewji, Georgia Institute of Technology

Abstract: Evaluation of the current patient release guidelines, as given in U.S. Nuclear Regulatory Commission (NRC) Regulatory Guide 8.39 Rev. 1, for end-stage renal disease (ESRD) patients receiving radioiodine (RAI) ablative therapy has yet to be addressed. In clinical practice, many clinicians have resorted to individualized RAI therapy using patient-specific dosimetry, necessitating biokinetic modeling for patient release considerations in patients with comorbidities. In this study, a biokinetic model for I-131 in ESRD patients on dialysis has been developed, improving on traditional simplified compartmental models, reflective of kinetics from multi-compartment models with updated transfer coefficients modified to reflect the different physiological functions of compartments. To determine a comparison via the NRC Reg. Guide 5 mSv criteria, effective dose rate coefficients were computed by combining updated biokinetic model with a Monte-Carlo radiation transport calculation of stylized computational hermaphroditic phantoms. The computed dose coefficients from ESRD patients were then compared to the dose rates generated for point-source models of NRC Reg Guide 8.39 Rev. 1 (and the proposed methodology in Rev. 2). From the results obtained, the baseline models of Rev. 1 and Rev. 2 depicted overestimation of the effective dose rate to an exposed individual for the time immediately post-administration, and both models overestimated the total dose to the maximally exposed individual. However, the application of various patient specific modifying factors to the Rev. 2 model resulted in an overestimation by only a factor of 1.25. Overall, the results produced with the patient-specific modifications provide improved convergence with the dose rate coefficients computed in this study for ESRD patients. The study thus demonstrates the utility and impact of incorporating realistic biokinetic models for consideration in developing patient release guidelines for radionuclide therapies.

TPM-A.7   16:15  The Effects of the 2009 Molybdenum-99/ Technetium-99m shortage: Is it Time to Move On? AD Miller*, University Alabama Birmingham ; E Caffrey, University Alabama Birmingham; C Wilson, University Alabama Birmingham

Abstract: In 2009, we experienced a global Molybdenum-99 (Mo-99)/ Technetium-99m (Tc-99m) shortage, due to the unexpected closure of the National Research Universal reactor (NRU) in Chalk River, Ontario. This shortage came shortly after the unforeseen 2008 temporary shut-down of the High Flux Reactor (HFR) in the Netherlands. Both reactors required immediate brief cessations for necessary repairs. The closure of both reactors, within months of each other, affected medical diagnostic imaging tremendously. Governing nuclear agencies, such as the Organization for Economic Co-operations and Development (OECD) and the International Atomic Energy Agency (IAEA) sought to limit the reoccurrence of another shortage by implementing nonnegotiable quality control and quality assurance guidelines for nuclear facilities. The overall goal was to minimize the effects of provisional reactor closures. Fast forward less than fifteen years, the 2022 Belgian Reactor 2 (BR2) mechanical failure resulted in yet another Mo-99/Tc-99m shortage. The closure of the BR2, although planned, resulted in an abrupt shortage. Luckily, this shortage did not last long. It was well managed, and the effects were much less than those in 2009. So why mention it? Technetium-99m is an indispensable isotope used for a large majority of diagnostic medical imaging procedures (Filzen et al., 2016). Even the smallest amount of time without this isotope will result in a global restriction of adequate healthcare. Therefore, it is essential to ensure the preservation and production of Mo-99/Tc-99m by reducing the probability of a shortage, whether short-lived or not. This review examines the effectiveness of the efforts made by governing nuclear agencies in 2010 to determine if they are likely to be sufficient to prevent future shortages, all from the unique perspective of a certified nuclear medicine technologist.

TPM-A.8   16:30  Participating In The Cesium Irradiator Replacement Project In A Post Pandemic World SH King*, Penn State Hershey Medical Center

Abstract: The Cesium Irradiator Replacement Project (CIRP) with The Department of Energy’s National Nuclear Security Administration (NNSA) provides incentives to remove a radioisotope irradiator and replace it with an X-ray irradiator. In this discussion, the CIRP program was used to remove a cesium blood irradiator in a medical center setting. There are a number of steps and milestones that must be performed before the unit can be removed. Getting a consensus on moving the radioisotope irradiator out of your facility is key. Financial considerations must be considered and budgeting timelines met. Logistics surrounding the removal must be thoroughly researched. Paperwork, emails and documents need to be filed together logically. Training with the new unit and ensuring dose consistency is a service that could be provided by a Health Physics/ Radiation Safety department. An overview of the process will be provided including thoughts on how to pre-plan prior to contacting NNSA. Finally, performing the benefit analysis calculation regarding using a radioisotope vs. x-ray irradiator can be complicated in a post pandemic world. Real life experience will be discussed with some issues presented.

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