TAM-A - Medical Health Physics 1 Woodrow Wilson A 08:00 - 12:00
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| Chair(s): Thomas Morgan and Andy Miller
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TAM-A.1
08:00 Misplaced Iridium-192 Seeds at NCAMC, Recovery and Aftershocks, 14NOV08 to 22MAY09 AP Miaullis*, Self
Abstract: The names (including the duty station) have been changed in this abstract and the presentation to protect the innocent and otherwise. On Monday (10NOV08) a patient in Ward 65 of No Comment Army Medical Center (NCAMC) had eight nylon ribbons with 56 Iridium-192 (Ir-192) seeds (with a total activity of 2.9 GBq, 77.8 mCi) placed into eight individual afterloading catheters, externally placed on her shoulder under a bandage. The dose rate was 50 cGy/hr (50 R/hr) with an intended dose of 45 Gy (4,500 R) to be removed in 90 hours. On Friday (14NOV08), three of the strands were missing off the patient. This presentation covers the comedy of errors involved with finding the three strands and the legal and social impact of this event. The end result message is that as a health physicist, we all end up making mistakes, and we all should recover and learn from those mistakes.
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TAM-A.2
08:15 ALARA Planning in Medical Health Physics for Patient Safety TL Morgan*, Versant Medical Physics
Abstract: The traditional role of radiation protection professionals is to assure that radiation doses are maintained ALARA. In the clinical environment this typically means monitoring employee doses, training workers in radiation safety, investigating medical events and recommending remediation measures, and surveying facilities to ensure doses to the public do not exceed regulatory limits.
What is missing from these efforts is a focus on patient safety. This presentation will advocate for radiation protection professionals to consider efforts to ensure patient doses are maintained ALARA as well. Discussion will include using the principles of operational risk management to identify and categorize radiation hazards, assessing the risks, and crafting remediation strategies. Included in these efforts is an emphasis on seeking out and engaging the medical professionals who prescribe and administer radiation to patients and education of both these professionals and senior management on the tools available for ALARA planning. Also included will be a discussion of the importance of training practitioners in patient dose management and bench marking radiation doses.
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TAM-A.3
08:30 DHA Unusual Occurrences – The Intersection Between Clinical and Operational Radiation Safety CA Dufford*, Defense Health Agency
Abstract: The Defense Health Agency (DHA) Radiation Safety Program (RSP) encompasses ionizing and non-ionizing radiation programs, including medical, research, and laboratory applications. The RSP developed the unusual occurrences (UO) program to ensure compliance with federal reporting requirements, collect data on incidents and vulnerabilities, and most importantly to identify and apply lessons learned to safeguard patients, staff, and facilities. Although the program includes typical radiation safety reportable events, such as lost or damaged sources, staff exposures, and contamination, sixty five percent (65%) of the events reported in 2022 directly impacted patients and their care. In many cases the causes and contributing factors dealt more with clinical practices than traditional radiation safety concerns. In attempt to better address these vulnerabilities, a the RSP developed a working relationship with the DHA Patient Safety Program. The DHA RSP shares UO data with Patient Safety while Patient Safety shares data from the Joint Patient Safety Reporting Program they administer. This presentation is an overview of the relationship between these two programs and their areas of responsibility, actions and efforts taken so far to enhance the safety of DHA operations, and future opportunities to pursue. The presenter will share experiences and lessons learned from addressing vulnerabilities, which blur the line between radiation safety and clinical safety programs.
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TAM-A.4
08:45 Quantitative Analysis of the Impact of Automatically Generated Normal Tissue Contours on Knowledge-Based Planning Model Quality SC Arnold*, UAB Health Physics
; JM Harms, UAB Rad Oncology; CE Cardenas, UAB Rad Oncology; EA Caffrey, UAB Health Physics; CA Wilson, UAB Health Physics
Abstract: While radiotherapy has become one of the primary standards of treatment for cancer in areas such as the brain, treatment plans are limited by the time it takes physicians to contour CT images used for dose distribution calculations. Automation of the contouring process can not only improve the rate of plan formation but establish a standard of care. With the development and implementation of knowledge-based planning (KBP) in radiation oncology, information derived from treatment plans provide machine learning models with years of experience to assess and create future treatment plans. Since KBP model quality rely on contouring from training plans, it is crucial to assess the impact contour quality has on the model-generated plan quality. Understanding contour impact on model development can lead to more consistent, higher quality, and more optimal outcomes for the future. The brain was selected as the target disease site and 125 manual physician treatment plans were selected. Scans of the disease site then underwent autocontouring through a deep learning clinical model. Protective margins were then implemented for both the brainstem and spinal cord. Both the manual and deep learning contours were then added to the RapidPlan tool for model training. It is hypothesized that utilization of autocontouring will provide a more accurate model allowing for higher quality of care with higher consistency between cases. Both the manual and autocontour models will be compared based on quality and consistency. While KBP and deep learning show promising potential and are already implemented in clinical settings, evaluation of treatment model training and refinement is required to further refine plan quality. Given the success of RapidPlan model plans, further development of the model would include seeking to reduce the number of manual cases needed to train KBP models.
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TAM-A.5
09:00 Density Override SL Reed*, University of Alabama at Birmingham
; KM Blue, University of Alabama at Birmingham; A Alexandrian, University of Alabama at Birmingham; E Caffrey, University of Alabama at Birmingham; C Wilson, University of Alabama at Birmingham
Abstract: High-density objects such as prosthetics, cardiac implanted devices, or surgical clips can create artifacts in computed tomography (CT) images used for radiotherapy planning, which can lead to regions of inaccurate CT information. These artifacts can impact the accuracy of dose calculations for radiotherapy treatment plans and may require large amounts of time to manually override. Previous research shows that larger ranges of CT numbers can impact the accuracy of dose calculations, and that different dose calculation algorithms handle artifacts in CT images differently. Manual correction of voxels affected by high-density objects in CT scans is the standard solution used by radiotherapy physicists. However, due to the time-consuming nature of manually overriding each scan some physicists prefer to ignore these objects entirely and assign a CT number of 0, which corresponds to water, possibly leading to inaccurate dose calculations. In this study, small and large surgical clips made of titanium (density = 4.5 grams/cubic centimeter) and tantalum (density = 16.6 grams/cubic centimeter) will be placed in a tissue equivalent bolus and have their dose measured using radiochromatic film. These measurements will be compared to dose calculations made by Anisotropic Analytical Algorithm (AAA) and AcurosXB (AXB) under various conditions. This presentation will cover the preliminary findings and proposed procedure for full assessment of the issue. This study aims to inform policies and practices on how to manage artifacts caused by these high-density objects and to identify the areas where manual overrides may be necessary.
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TAM-A.6
09:15 Radiotherapy Dose Calculation Algorithm Sensitivity to High Density Artifacts KM Blue*, The University of Alabama at Birmingham
; SL Reed, The University of Alabama at Birmingham; A Alexandrian, The University of Alabama at Birmingham; E Caffrey, The University of Alabama at Birmingham; C Wilson, The University of Alabama at Birmingham
Abstract: Radiotherapy planning can be adversely affected by inaccurate dose calculations due to the presence of high-density objects. High-density objects, such as surgical clips, produce artifacts in CT images which can result in errors in dose calculations. Manual correction of voxels containing incorrect information is recommended to prevent calculation errors, but this process can be cumbersome and sometimes results in planners compromising with crude corrections to save time. In addition, different dose calculation algorithms have shown sensitivity around regions where high-density objects and their artifacts reside. In this study we aim to determine the significance of density overrides for high-density objects and the artifacts they cause in radiotherapy treatment plans. To evaluate the impact of density overrides on calculations, a phantom was put together consisting of two plastic slabs, a water equivalent bolus, and a medium tantalum surgical clip which was inserted inside the bolus. The phantom was scanned using a CT scanner with a 0.9 mm slice thickness and 0.45 mm overlap slice to minimize voxel averaging differences at the location of the clip. A radiotherapy plan was created using a virtual tumor emulating a 1 cm diameter soft tissue tumor with the surgical clip at the center. Calculations were made using Anisotropic Analytical Algorithm (AAA) and AcurosXB (AXB) dose calculation algorithms. The differences between the two calculations were quantified for a plan in which 800 cGy was to be delivered to the target uniformly. Preliminary calculations show that max doses within the surgical clip calculated by AAA and AXB were 820.2 cGy (102.5%) and 1069.1 cGy (133.6%) respectively. In regions outside the surgical clip but within the target region, max doses reported by AAA and AXB were 815.7 cGy (102.0%) and 994.9 cGy (124.4%) respectively. We found that 0.07 cc of the AXB calculation, or 13.5% of the target volume, contained doses higher than the maximum dose reported by AAA. While current results are not conclusive enough to provide guidance for clinical radiotherapy practice, they provide a basis for future work to investigate variations in the setup, such as target size, phantom materials, and size of high-density objects. The findings from this study may help to improve the accuracy of radiotherapy treatment planning in the future.
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TAM-A.7
09:30 BREAK
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TAM-A.8
10:00 Establishing a Safe And Effective Radioligand Therapy Program for the Treatment of PSMA-Positive Prostate Metastases With Lutetium-177 (Pluvicto) CM Anderko*, West Physics and Thomas Jefferson University Hospital
; DM Howard, West Physics and Thomas Jefferson University Hospital; JA Berg, Thomas Jefferson University Hospital; S Wan, Thomas Jefferson University Hospital; AM Free, Thomas Jefferson University Hospital; JW DiNome, Thomas Jefferson University Hospital; EL Gingold, Thomas Jefferson University Hospital; ML MacCallum, West Physics and Thomas Jefferson University Hospital
Abstract: Lutetium-177 Vipivotide Tetraxetan (Pluvicto) was FDA-approved for the treatment of PSMA-positive prostate metastases on 3/23/22. With a backlog of patients expected to be eligible for this therapy, our center mobilized a team to begin a fast-track journey to make this therapy available to referring physicians. The complexities of the process were quickly realized, including the need for a multidisciplinary team, identification of treatment space, challenging workflow and logistics, technical obstacles, aggressive timelines, and increased capacity demands for staff. The planning team worked diligently to overcome the challenges and establish a pathway for the first patient treatment to occur within 5 months. Keys to a successful and timely launch included adapting an existing infusion room to accommodate Pluvicto administrations, developing a communications plan to link team members, and purchase of simple tools to facilitate dose assay, delivery, contamination and external exposure controls, and radioactive waste management. Continual program adjustments were made and implemented when inefficiencies in workflow were identified. Our center has since performed over 70 successful Pluvicto treatments within a five-month period with no significant radiation or patient safety issues. This presentation will review the strategies used to expedite Pluvicto implementation and the vision for expansion to a Theranostics Center of Excellence.
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TAM-A.9
10:15 Sharing Lessons from Lutetium-177 Therapies at a Cancer Clinic LA Chang*, Inova Health Systems - Radiation Oncology
; MA Taylor, Inova Health Systems - Radiation Oncology; J Fan, Inova Health Systems - Radiation Oncology; D Gregg, Inova Health Systems - Nuclear Medicine; N Patel, Inova Health Systems - Nuclear Medicine; MS Alcock, Inova Health Systems - Radiation Oncology; B Hinchcliffe, Yale-New Haven Hospital; P Patel, Houston Methodist Hospital; D Kim, Inova Health Systems - Radiation Oncology; MJ Eblan, Inova Health Systems - Radiation Oncology
Abstract: Lutetium-177 treatments in cancer clinics and hospitals are becoming more prevalent, especially with the FDA approval of Pluvicto in spring 2022. In winter 2022, Cappon et al published a very informative open paper in the Health Physics Journal, “Clinical Best Practices for radiation Safety During Lutetium-177 Therapy”. In this presentation, we seek to complement the information found in Cappon et al’s paper with experiences from our multidisciplinary team of health and medical physicists, nurses, nuclear medicine technologists, and radiation oncologists performing Lutathera infusions.
We will delve into details on topics including but not limited to: use of shielding for nuclear medicine and nursing staff, considerations for choice of delivery methods, potential catheter use, choice of survey instrument and its location for 5-minute recordings during the infusion, calculation of release criteria, spill management to include clean up, and waste storage. For example, we experimented with various portable lead shield locations to determine the optimal balance between staff and public shielding and the hindrance to perform clinical tasks. It was found that using a Ludlum 26-1 was preferable to a Fluke 451P ion chamber for infusion recordings. With guidance from NRC Reg Guide 8.39, we calculated release criteria for Lu-177 therapies to be approximately 9 mR/hr at 1 m. For clean-up of minor spills, we found 409 de-waxing cleaner to be effective. We found that none of our staff involved in routine therapies has received any significant radiation exposure.
Lessons taken from our Lutathera and Xofigo programs will be presented as our clinic prepares for the introduction of Pluvicto procedures. It is our intention that the presentation will help generate a discussion among existing Lutetium-177 radiopharmacy programs as well as help guide programs that are just getting started.
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TAM-A.10
10:30 Managing Radiation Safety Issues with 177Lu Theranostic Agents JP Ring*, Beth Israel Deaconess Medical Center
; AJ Parker, Beth Israel Deaconess Medical Center; C Stenstrom, Beth Israel Deaconess Medical Center; G Barletta, Beth Israel Deaconess Medical Center; S Griffin, Beth Israel Deaconess Medical Center; S Whitmarsh, Beth Israel Deaconess Medical Center; J Jozokos, Beth Israel Deaconess Medical Center
Abstract: With the increased use of higher radioactivity therapeutic agents such as Lutathera and PSMA (177Lu), there is potential that extravasations / infiltrations may lead to injection site issues and skin exposures to both the patient and staff. A quality management program involving physicians and nuclear medicine, nursing and radiation safety staff can help to minimize unintended events and optimize the patient experience.
Through a cooperative effort, we identified potential complications and drew on the collective expertise across the Medical Center to reduce the risk of extravasations / infiltrations and skin exposures. An IV competency program was established for Nuclear Medicine Technologists under the direction of the Nursing Program to ensure staff is highly attuned to misplaced IV’s and the potential for extravasations / infiltrations. The competency program is matched with a post procedure survey of the administration site to identify potential extravasations. Criteria were established to refer the patient to a Nuclear Medicine Physician to investigate potential of an extravasation.
When administering 200 mCi of 177Lu to a patient, skin dose and contamination present are a potential concern especially for incontinent PSMA patients. Depending upon the frequency of incontinent pad exchange, it is not unreasonable to calculate a skin dose from pad use in excess of 2 Gy for one treatment. Over the course of treatment, it is possible that an incontinent PSMA patient could experience erythema. PSMA excretion models indicate a rapid release in the first few hours. To address this exposure concern, these patients are held for two hours post administration with frequent pad exchanges to reduce the exposure. Patients are released with instructions for frequent pad changes and showers to reduce skin exposures.
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TAM-A.11
10:45 Growing Need for a Standardized Response to Radiopharmaceutical Extravasations MR Drelich*, University of Alabama at Birmingham
Abstract: Extravasations are medical occurrences where an injected or infused pharmaceutical are deposited into the soft tissue near the injection site, rather than into the bloodstream. With radiopharmaceuticals, extravasations can result in potentially large radiation doses to skin and tissue. The current rate of extravasations in clinical settings is estimated to be between 0.1-6%. In the interest of patient safety, a clearer understanding of the dosimetry and differences in extravasation scenarios to simplify dose estimation is needed. Similarly, the NRC is considering modifying regulations to include extravasations as reportable medical events rather than to continue considering them as patient interventions. Several papers have used the Fano Theorem for dose estimations, but the estimates have also shown inconsistencies between estimating dose for the skin versus tissue. Currently, dose estimates would indicate that deterministic effects are probable, but rarely are observed. There is currently no one-size-fits-all solution for dose calculations for extravasations. To be fully prepared to meet the potential for 24-hour reporting requirements for medical events, a standard should be developed. This research aims to review and compare existing literature to determine the best practices for radiation safety programs’ response to extravasation events. Methods of dose calculations include the use of publicly available software such as IDAC, modified versions of VARSKIN+, Monte-Carlo methods, and use of the Fano Theorem. More work is still needed for accurate determination of the effective half-life of extravasated radiopharmaceuticals and reliably determining the fraction of extravasated material. Extravasation scenarios vary widely and there are questions regarding the regulatory need to determine skin dose versus tissue dose and whether this regulation is truly needed for patient safety if deterministic effects are generally not observed and stochastic effects are not sufficiently studied.
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TAM-A.12
11:00 Physician Privileging for Medical Laser Use DH Elder*, UCHealth
Abstract: There are a wide variety of laser types and wavelengths in use at healthcare facilities. The interaction between the laser radiation and the tissue is strongly dependent on the wavelength. However, many facilities grant physicians privileges for “Use of Laser” or similarly generic laser privileges. For those procedures, the laser privilege is often a core privilege that requires no documentation of training or experience. The Joint Commission Standards and the Centers for Medicare and Medicaid Services have standards regarding the evaluation of qualifications and competencies that indicate that the current processes at many facilities are not sufficient. The requirements for laser privileges have been changed at UCHealth facilities to ensure there is documentation of training and experience with each laser type that is used by a provider. Periodic audits are performed to ensure that providers have privileges for the lasers used.
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TAM-A.13
11:15 Dose Estimates to Workers From Y-90 Excluding Fluoroscopy During Microspheres Treatments A Miller*, Cleveland Clinic
; R Banks, Cleveland Clinic; S Rayadurgam, Cleveland Clinic; P Rowland, Cleveland Clinic
Abstract: During Y-90 microsphere treatments, workers receive occupational dose from fluoroscopy use and from the Y-90 microspheres. The dosimeters in use by the workers integrates the doses received from both sources during the wear period. The occupational dose received from the fluoroscopy use on each patient is highly variable and dominates the occupational exposure for the physician. The occupational dose received from the Y-90 sources is estimated by dose rate measurements and time/motion studies to provide a tool to provide customizable dose estimates for each user based on their tasks. This information can be used to better educate staff members in the interventional radiology suite who work with these patients.
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TAM-A.14
11:30 Effect of Tube Housing Leakage from X-ray Imaging System Tube Housing on Patient Dose PC Steege*, University of Wisconsin - Madison
; JP Gainor, Egg Medical; RF Wilson, University of Minnesota - Twin Cities
Abstract: We previously demonstrated that radiation leakage from the x-ray tube housing of C-arm fluoroscopy units used for interventional procedures (such as cardiac stents, interventional radiology) can significantly increase scatter radiation from the patient. In this study, we assessed the role of the tube housing leakage in increasing the patient radiation dose. To investigate this, we created a grid 50 cm by 80 cm on the x-ray table and obtained x-ray dose measurements taken at each point. A validated leaded-glass sphere was used as a scatter target while under fluoroscopy. An additional shield was designed and fabricated to reduce the leakage radiation from the tube housing. The shield was created with 1 mm lead on the walls and 2 mm lead on the top and an aperture in the top for the primary beam. The primary beam was identified and considered to contribute the dose in a 10 cm by 10 cm square centered on the tube housing and the remaining dose was leakage from the x-ray tube housing outside the primary beam. By comparing x-ray doses with and without the added shield, it was determined that 9.5 ± 0.3% (mean ± detector error, p < 0.1) of the dose received was outside the primary beam. In addition, the dose values to various organs outside the imaging field in the patient’s body (estimated by position from the primary beam, assuming cardiac imaging) were calculated by averaging the dose rates of the grid points corresponding to the organ. The dose rate outside the primary beam to the lungs was found to be an average of 1581.5 ± 52.2 μSv/hr (mean ± SD, p > 0.01). This dose was reduced by 9.7 ± 0.3% (mean ± SD, p > 0.01) to 1440.9 ± 47.5 μSv/hr with the addition of the tube housing shield. More significantly, the average dose rate to the red bone marrow of the spine was found to be 2480.6 ± 81.6 μSv/hr (mean ± SD, p > 0.01). When the tube housing shield was put in place, this dose was reduced by 8.9 ± 0.3% (mean ± SD, p > 0.01) to 2239.9 ± 73.9 μSv/hr. With almost 10% of the patient’s dose being unreported from sources outside the primary beam, a significant amount of patient x-ray dose is not being accounted for. The results of this study raise concerns about how the dose to the patient is reported and may require further study into the long-term effects for the patient.
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TAM-A.15
11:45 Dosimetry for a new in vivo X-ray Fluorescence Measurement System CJ Burgos, Purdue University
; TR Grier, Purdue University; M Khan, Purdue University; MG Weisskopf, Harvard T.H. Chan School of Public Health; KM Taylor, United States Army Research Institute of Environmental Medicine; AJ Specht*, Purdue University
Abstract: Lead is a ubiquitous toxin with deleterious effects throughout the body and upon exposure is usually stored with bone. Metal exposures are typically measured in vivo using x-ray fluorescence (XRF) where a small radiation dose is delivered to the subject. We are developing a new K-shell technique for lead-in-bone utilizing a 140 kV x-ray tube (Moxtek 140G). In this study, we optimized the beam energy distribution and dosimetry using shielding and filters from the initial tungsten anode. We used CdZnTe detectors to measure the energy distribution of the beam and a RadEye B20 compact multipurpose contamination meter to assess and optimize radiation dosimetry. Beam energy was optimized by using thick high-density Molybdenum and aluminum filter shifting the beam energy up and removing low dose x-rays that were unnecessary to our goals. Dosimetry and shielding were measured both for the operator and the measured individual receiving the bone measurement. We recorded measurements of radiation dose through air, bone, and bone and soft tissue mediums from various geometries to characterize the x-ray beam and the resulting scatter. In air, measurements ranged from 30.49 mrem/h at the source to 0.14 mrem/h 60 cm away. Measuring the deep dose resulted in a dose of 12.59 to 0.55 mrem/h at 10 mm. Our 10-minute lead-in-bone measurement delivers at most a dose of 0.02 mrem (0.02 Sv) to the operator and 2 mrem (2 Sv) to the subject—much less than a dose delivered by a standard chest x-ray. In summary, the radiation dose received by our new KXRF system poses little to no risk to any persons involved and the beam energy is optimized for measurements of the K-shell of lead and cadmium for in vivo measurements.
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