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A Multi-Institutional End-To-End Dosimetry Mail Audit for Orthovoltage Small Animal Irradiators

M Gronberg1*, R Tailor2, S Smith3, S Kry4, D Followill5, S Stojadinovic6, J Niedzielski7, P Lindsay8, S Krishnan9, J Aguirre10, T Fujimoto11, C Taniguchi12, R Howell13, (1) The University of Texas MD Anderson Cancer Center, Houston, TX, (2) The University of Texas MD Anderson Cancer Center, Houston, TX, (3) The University of Texas MD Anderson Cancer Center, Houston, TX, (4) The University of Texas MD Anderson Cancer Center, Houston, TX, (5) The University of Texas MD Anderson Cancer Center, Houston, TX, (6) The University of Texas Southwestern Medical Center, (7) The University of Texas MD Anderson Cancer Center, Houston, TX, (8) Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, ON, CA, (9) Mayo Clinic Jacksonville, Jacksonville, FL, (10) The University of Texas MD Anderson Cancer Center, Houston, TX, (11) The University Of Texas MD Anderson Cancer Center, (12) The University Of Texas MD Anderson Cancer Center, (13) The University of Texas MD Anderson Cancer Center, Houston, TX

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: Studies performed using orthovoltage small animal irradiators may not be reproducible or comparable, as there is a lack of dosimetric standardization among these irradiators. The purpose of this study was to develop a mailable, independent peer review system to verify dose delivery among institutions using X-RAD 225kV irradiators.

Methods: A robust mouse phantom was designed with dimensions similar to those of typical laboratory mice (85(L)mm, 25(W)mm, 20(H)mm). Two phantoms were machined from high-impact polystyrene; one accommodated three TLD and the other an Exradin A1SL ionization chamber for cross-comparison with the TLD. The TLD response was characterized in the small animal irradiator using anterior-posterior and posterior-anterior beams of 225kV. The dose rate in the mouse phantom for each beam orientation was determined by multiplying the measured TG-61 dose rate with the ratio of the ionization chamber readings in-phantom to in-air. To characterize the TLD response, a known dose was delivered to the TLD mouse phantom. Lastly, an uncertainty analysis for the developed mail audit was performed, and the system was mailed to four academic institutions with well-established small animal irradiation programs to verify their small animal dosimetry.

Results: The average TLD energy correction factor (compared to Co-60) in the mouse phantom was 0.821±0.006. The developed system had an estimated total uncertainty (1-sigma) of 2.1%. The mail audit study indicated that four institutions were able to deliver a radiation dose to the mouse phantom within ±7% of the target dose. Differences between the measured and stated doses ranged from -7% to +4%. Our mail audit results agreed best with institutions using Monte Carlo-based treatment planning.

Conclusion: An end-to-end dosimetry mail audit for orthovoltage small animal irradiators gave consistent results among well-established small animal irradiation programs. The developed system has the potential to greatly improve dosimetric standardization in preclinical small animal studies.

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Keywords

Quality Assurance, X Rays, TLDs

Taxonomy

TH- Small Animal RT: Quality Assurance

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