Citations

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.

Abstract In recent years, various tracking technologies that work independently of imaging systems have been proposed to automate, simplify, and enhance various tasks in the brachytherapy treatment workflow. These tasks, critical to the overall accuracy of the therapeutic dose delivery, include applicator, catheter and needle insertion guidance, and reconstruction as well as transfer tube connection in afterloading technique. Task Group 317 was established as a joint American Association of Physicists in Medicine (AAPM) and European Society for Radiotherapy and Oncology (ESTRO) committee to review: the current state‐of‐the‐art scientific literature as it pertains to tracking technology in the field of brachytherapy; the benefits and issues related to the use of the technology for automated reconstruction of brachytherapy implants, quality control (QC) tasks such as channel path and tip reconstruction, and real‐time guidance tasks; their limitations, in particular in the clinical environment and, finally, to develop recommendations related to commissioning, quality assurance (QA) and clinical use. The Task Group has looked in detail at key tracking technologies in advanced brachytherapy applications: infrared, electromagnetic, fiber optic shape sensing (fiber Bragg grating), and active radiofrequency coil tracking. For each, the performance and accuracy in well‐controlled conditions as well as in clinically relevant environments are provided. Guidelines for clinical implementations, including target accuracy and performance needed for critical tasks, are summarized. Risk‐based analysis is discussed in the context of an electromagnetic‐based tracking system used as part of a clinical trial. The report concludes with the essential elements of an effective quality management program dedicated to the advanced features enabled by the above‐described technology.