A combined dose calculation and verification method for a small animal precision irradiator based on onboard imaging

Med Phys. 2012 Jul;39(7):4155-66. doi: 10.1118/1.4725710.


Purpose: Novel small animal precision microirradiators (micro-IR) are becoming available for preclinical use and are often equipped with onboard imaging (OBI) devices. We investigated the use of OBI as a means to infer the accuracy of the delivered treatment plan.

Methods: Monte Carlo modeling of the micro-IR including an elliptical Gaussian electron beam incident on the x-ray tube was used to score dose and to continue photon transport to the plane of the OBI device. A model of the OBI detector response was used to generate simulated onboard images. Experimental OBI was performed at 225 kVp, gain∕offset and scatter-glare were corrected. Simulated and experimentally obtained onboard images of phantoms and a mouse specimen were compared for a range of photon beam sizes from 2.5 cm down to 0.1 cm.

Results: Simulated OBI can be used in small animal radiotherapy to determine if a treatment plan was delivered according to the prescription within an uncertainty of 5% for beams as small as 4 mm in diameter. For collimated beams smaller than 4 mm, beam profile differences remain primarily in the penumbra region of the smallest beams, which may be tolerable for specific preclinical micro-IR investigations.

Conclusions: Comparing simulated to acquired OBI during small animal treatment radiotherapy represents a useful treatment delivery tool.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't
  • Validation Study

MeSH terms

  • Animals
  • Equipment Design
  • Equipment Failure Analysis
  • Film Dosimetry / instrumentation*
  • Film Dosimetry / veterinary*
  • Mice
  • Radiometry / instrumentation*
  • Radiotherapy Dosage
  • Radiotherapy, Conformal / instrumentation*
  • Radiotherapy, Conformal / veterinary*
  • Reproducibility of Results
  • Sensitivity and Specificity