Room: Exhibit Hall | Forum 3
Purpose: to assess the performance of a miniature and radio transparent detector for online monitoring of radiation doses delivered to small animals in pre-clinical research. We evaluated the dose accuracy, the impact of detector placement close to the irradiated region on the quality of the positioning and the ability of the detector to detect meaningful deviation from planned dose.
Methods: A cohort of 20 mice was treated as part of an IRB approved study on radiation induced skin toxicity and wound healing. For this protocol, each mouse was to receive a skin dose of 45 Gy. A miniature plastic scintillation detector (0.5 mm diameter) was built for in vivo measurement. The detector was introduced in the treated region between a layer of bolus material and the skin for half of the treated mice. The signal readout was performed with a spectrometer to facilitate the decoupling of the scintillation signal from the Cherenkov stem effect.
Results: In vivo dose measurements were, on average, 1.7% lower than the planned dose. In one case, the measured dose was off by 11%, but in all other cases the measured dose was within 4% of the planned dose. After review of the outlier, it was found that important air gaps were present in that particular setup and the treated isocenter was farther away from the skin than planned. By comparing mouse with and without in vivo detector, no statistically significant degradation of the positioning accuracy was found. Finally, detection of unplanned treatment interruption was also demonstrated.
Conclusion: We've developed a miniature, radio transparent detector device for online monitoring of small animals. We've shown that this can be an easy and unobtrusive method to guarantee that the planned dose is actually delivered to animals used in pre-clinical studies.
Funding Support, Disclosures, and Conflict of Interest: Supported in part by the Canadian Institute of Health Research (CIHR)