Underwood, James Kyle

Abstract Background Alpha‐emitting radionuclides enable precise cancer therapy through high linear energy transfer and limited tissue penetration, damaging tumor cells while sparing healthy tissue. Diffusing Alpha‐emitters Radiation Therapy (Alpha DaRT) features Ra‐224 sources that are implanted directly into the tumor and emit alpha particles during radioactive decay. Alpha DaRT has demonstrated efficacy and safety in preclinical and early clinical trials across multiple tumor types, including skin, head and neck, and pancreatic cancers. Purpose Reliable and efficient methods for verifying Alpha DaRT source activity prior to treatment can help support accurate and consistent radiation delivery. The direct measurement of alpha particles from sources within an Alpha DaRT applicator is impractical due to their short range; however, gamma emissions from the Ra‐224 sources can be used to infer radioactivity. This study established a protocol for verifying the source activity within Ra‐224 Alpha DaRT applicators using a reentrant well‐type ionization chamber, providing users with a practical method for detecting errors in source manufacturing or certificate paperwork without compromising applicator sterility. Methods Ra‐224 Alpha DaRT sources in sterile packaging (Flex and Needle applicators with 1–4 sources) were assessed. Source energy spectra and activities were verified using a high‐purity germanium (HPGe) radiation detector. Calibration factors (kBq/pA) were established using an IVB1000 well‐type ionization chamber with measurements conducted by placing single applicator sterile packages into the chamber with sources centered in the chamber's sweet spot and corrected for temperature, pressure, and leakage current. Quality assurance was performed on 26 Flex applicators using the established calibrations before the first clinical procedure. Results HPGe measurements agreed with vendor‐stated activities. The average calibration coefficient using the IVB1000 chamber was 233 ± 3 kBq/pA for Flex and 597 ± 7 kBq/pA for Needle applicators. Calibration coefficients were consistent across two IVB1000 chambers. Source number dependence was observed, with calibration factors increasing by 1.7% ± 0.7% per source (Needle) and 2.7% ± 0.6% per source (Flex). Measurement repeatability was 3.3%. Applying the calibration to 26 Flex applicators before the first patient treatment yielded a 1.1 ± 5.8% (range: −7.5% to 11.4%) difference relative to the vendor's stated activity. Conclusion A reentrant well‐type ionization chamber is suitable for pre‐treatment quality assurance of Ra‐224 Alpha DaRT applicators, enabling verification of the vendor‐stated activity while maintaining sterility within sealed packaging.

After implementing a process for flagging readmitted radiopharmaceutical therapy patients, it was discovered that major assumptions for these patients were not correct, specifically the magnitude of patients and the location of the readmissions. Data collected from May to December 2024 revealed 501 post-therapy patient encounters out of 1,139 administrations. Analysis showed varying return rates across different radiopharmaceuticals and departments, highlighting the need for updated radiation safety response. Results indicated that most encounters occurred in outpatient settings, with contamination above action levels found in 61% of responses. The study underscores the importance of continuous assessment and collaboration among stakeholders to adapt to new radiopharmaceutical therapies and ensure effective radiation safety practices.

The radiopharmaceutical therapy field is experiencing a surge of novel treatments and expanded uses for existing treatments, broadening the range of patients that can be treated. This expansion presents new challenges for managing patient release due to new patient populations with additional comorbidities, increasing the incidence of patients requiring care shortly after administration. This paper outlines the challenges and potential solutions for managing readmitted radiopharmaceutical therapy patients. It discusses the importance of having radiation protection policies and procedures in place for staff who may be unfamiliar with radiation. The paper also highlights the need for just-in-time training and radiation monitoring equipment for care staff, as well as the development of a notification system within the electronic health record to ensure staff can safely care for these patients. Preparing for these eventualities is essential for implementing a radiopharmaceutical therapy program that is ready for the expansion of existing and novel treatments.

In radiation safety programs, particularly in large healthcare systems, personal dosimetry is often issued conservatively, leading to unnecessary monitoring of individuals with minimal exposure risk. This study describes a structured approach implemented at Mayo Clinic to evaluate the necessity and exchange frequency of dosimeters using two years of retrospective radiation dose data. Personnel were grouped based on job type and workplace conditions, then dosimetry data was analyzed at the 50th percentile, 95th percentile, and maximum levels against conservative thresholds. Regulatory requirements and managerial input were incorporated throughout the decision-making process. From 2020 to 2024, this method resulted in the reduction of dosimeter frequency for 82 individuals and complete removal for 1,067: reducing dosimeter issuance by 4,912 each year. The approach enabled a more efficient use of resources, allowing radiation safety efforts to be directed toward higher-risk groups and activities without compromising compliance or worker protection. This model provides a conservative, scalable framework for optimizing dosimetry programs in healthcare and potentially other radiation-using industries.

Abstract Many medical facilities across the United States use ionizing-radiation-producing machines and radioactive materials for diagnostic and therapeutic purposes on a regular basis. While institutions are required to ensure full-term fetal doses are below the regulatory limit, clear guidance on how pre-declaration fetal doses should be estimated is not available. This paper provides a process that can be used to estimate the pre-declaration fetal dose and provides a predictive screening tool for licensees to use to recommend workload adjustments prior to actual fetal dosimetry results that could exceed the institutions derived investigation levels. The evaluation process presented herein serves as a guide for medical licensees when performing fetal dose evaluations for declared pregnant workers.

Abstract Lutetium Dotatate radiopharmaceutical therapy (Lutathera) was approved by the United States Food and Drug Administration in 2018 and is used to treat somatostatin receptor positive neuroendocrine tumors. With all new radiopharmaceutical therapies, the radiation exposure to members of the public from the patient who received the therapy must be within regulatory limits and safe. If the patient will expose members of the public to too much radiation, the therapy must be performed on an inpatient basis. This paper shows that the administration of Lutathera can be done on an outpatient basis and provides safety and travel restrictions that should be communicated to the patient prior to leaving. The guidance presented herein serves as a basis for medical institutions looking to use Lutathera to treat patients.