Introducing the Joint Aapm/Iroc Houston Ionization Chamber Registry to Host TG-51 Reference Dosimetry Data
Abstract
Purpose
To provide AAPM members with a centralized, authoritative, and continuously updated web-based resource for obtaining beam quality conversion factors, kQ, and other data needed to realize absorbed dose measurements using the AAPM TG-51 protocol.
Methods
The AAPM appointed the Ionization Chamber Registry Working Group (WGICR), composed of calibration laboratory metrologists, detector manufacturers, and leaders in reference dosimetry, along with members of IROC Houston, to develop an AAPM policy document and procedures for inclusion of chambers on the ionization chamber registry (ICR). The ICR integrates two primary functions: (1) a curated, quality-controlled compilation of published kQ data consistent with AAPM dosimetry protocols (TG‑51 and its Addenda), and (2) a transparent, standardized process for evaluation of reference-class performance and verification of the accuracy of kQ data for new ionization chambers. Continuous quality control is required for the chambers on the ICR, which allows updates to data, e.g., following chamber redesign or manufacturing changes, and allows removal of detectors that no longer demonstrate reference-class performance.
Results
The ICR currently includes kQ data for MV photon and MeV electron beams, with planned expansion to MR-linacs, kV x‑ray and proton modalities. Each dataset undergoes review by multiple experts to ensure reference-class performance and consistency with TG‑51 methodologies. The ICR framework reduces the need for frequent protocol revisions, enhances data transparency, and promotes harmonization of reference dosimetry methodology across institutions.
Conclusion
The ICR website is live and can be accessed via the main IROC Houston landing page. It provides a single, reliable source for validated kQ data that is consistent with, but supersedes the data provided in published reports. Feedback is sought from AAPM members. The launch of the ICR marks a significant advancement in global dosimetry standardization.