An interlaboratory comparison of dosimetry for a multi-institutional radiobiological research project: Observations, problems, solutions and lessons learned

Abstract

Purpose: An interlaboratory comparison of radiation dosimetry was conducted to determine the accuracy of doses being used experimentally for animal exposures within a large multi-institutional research project. The background and approach to this effort are described and discussed in terms of basic findings, problems and solutions.

Methods: Dosimetry tests were carried out utilizing optically stimulated luminescence (OSL) dosimeters embedded midline into mouse carcasses and thermal luminescence dosimeters (TLD) embedded midline into acrylic phantoms.

Results: The effort demonstrated that the majority (4/7) of the laboratories was able to deliver sufficiently accurate exposures having maximum dosing errors of ≤5%. Comparable rates of 'dosimetric compliance' were noted between OSL- and TLD-based tests. Data analysis showed a highly linear relationship between 'measured' and 'target' doses, with errors falling largely between 0 and 20%. Outliers were most notable for OSL-based tests, while multiple tests by 'non-compliant' laboratories using orthovoltage X-rays contributed heavily to the wide variation in dosing errors.

Conclusions: For the dosimetrically non-compliant laboratories, the relatively high rates of dosing errors were problematic, potentially compromising the quality of ongoing radiobiological research. This dosimetry effort proved to be instructive in establishing rigorous reviews of basic dosimetry protocols ensuring that dosing errors were minimized.

Keywords: Dosimetry; OSL/TLD dosimeters; animal models; dose-response curve; haematology; ionizing; radiation.

Figure 1

Two basic dosimetry testing approaches, in turn two phases, have been employed for the RERF/NIAID-funded project: Phase 1, OSL dosimeters embedded surgically into mouse carcasses; Phase 2, TLD dosimeters embedded into plastic mouse phantoms.

Figure 2

Key elements and logistics of the dosimetry testing for Phase 1

Figure 3

Key elements and logistics of the dosimetry testing for Phase 2

Figure 4

Phase 1 OSL-based testing: Measured doses relative to 1 & 4 Gy target doses for each participating laboratory. (Plotted doses are averages of measured doses with standard deviations generally ≤ 0.05, except for SDs of 1 Gy Lab #3 value of 0.20 and 4 Gy Lab #7 value of 0.54).

Figure 5

Phase 1 OSL-based testing: Dose errors (% errors) relative to 1 & 4 Gy target doses for each participating laboratory. (Plotted doses are averages of measured % errors with standard deviations generally ≤ 5.0, except for SDs of 1 Gy values for Lab #1 of 5.8, Lab #3 of 20.4 & 10.8).

Figure 6

Phase 1 OSL-based testing: Measured doses (left panel) and dosing errors (right panel) relative to all other target doses tested (0.5, 2, 5, 7, 8, & 10 Gy) for each participating laboratory. (Plotted doses are averages of measured doses with standard deviations generally ≤ 0.05, except for SDs of Lab #2 at 10 Gy of 0.20, Lab #5 at 7 Gy of 0.15, and Lab #6 at 8 Gy of 0.09: plotted % errors are average values with standard deviations generally ≤ 5.0, except for SDs of Lab #1 at 0.5 Gy of 9.1/17.2 and at 2.0 Gy of 11.3).

Figure 7

Phase 2 TLD-based testing: Measured doses relative to 1 & 4 Gy target doses for each participating laboratory. (Plotted doses are averages of measured doses with standard deviations generally ≤ 0.05, except for SDs of 1 Gy Lab #3 value of 1.99 and 4 Gy Lab #1 value of 0.55, Lab #3 of 1.05 and Lab #7 of 0.06).

Figure 8

Phase 2 TLD-based testing: Dose errors relative to 1 & 4 Gy target doses for each participating laboratory. (Plotted doses are averages of measured % errors with standard deviations generally ≤ 5.0, except for SDs of 4 Gy value for Lab #1 of 13.9).

Figure 9

Combined OSL- and TLD-based tests: Relationship between measured radiation doses and related target doses.

Figure 10

Combined OSL- and TLD-based tests: Extent of dosing errors (% errors) over full range of testing measurements.