Small Animal Conformal Radiotherapy

We have modified a 120 kVp GE microCT scanner to allow it to deliver conformal radiation beams to small animals, in a manner similar to clinical radiotherapy. To accomplish this, a microCT-compatible variable-aperture collimator and 2D motion stage have been developed. Preliminary evaluation of this system has demonstrated that we can achieve dose rates as high as 3 Gy/minute and beam sizes as small as 1 mm, with beam penetration suitable for small animal targets. By using a series of radially convergent beams, therapeutic radiation doses may be delivered to confined tissue volumes while sparing surrounding normal tissues. MicroCT images of live subjects can be acquired on this system at spatial resolutions down to 50 um, which may then be used to plan radiation treatments using software described below. Monte Carlo models of this system have been constructed to facilitate accurate dosimetric simulations. By developing an inherently image-guided radiotherapy system, we can merge images from multiple modalities for use in planning and evaluating radiation therapies. This unit is now operational and is being applied as a tool to study tumor radiobiology.

Current research projects in this area include:

  • Design of device control software for micro-CT based radiotherapy
  • Development of Monte Carlo simulation methods for small animal kilovoltage radiotherapy
  • Development of inverse planning methods
  • Engineering and evaluation of immobilization methods for small animal multimodal imaging and therapy
  • Investigation of intensity-modulation methods

Recent publications:

Iris-type variable aperture collimator, allowing creation of pseudocircular beam profiles of 1 to 60 mm

Two-dimensional translation stage, allowing positioning of an arbitrary point at the beam isocenter

Treatment of a Myc-driven spontaneous lung tumor

Treatment of a luciferase-expressing cutaneous teratoma, and monitoring of treatment response