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PET-Guided Selective Dose Escalation for a Small Animal Tumor Model


C Bass

C Bass1*, M Axente2,J He1,S Gobalakrishnan1, J Zweit1, G Hugo1, A Pugachev1, (1) Virginia Commonwealth University, Richmond, VA, (2) Stanford Hospitals and Clinics, Stanford, CA,

WE-E-108-11 Wednesday 2:00PM - 3:50PM Room: 108

Purpose:
To develop methods for pre-clinical validation of PET image-guided selective dose escalation in IMRT treatment using the Small Animal Radiation Research Platform (SARRP, Xstrahl).

Methods:
Nude mice bearing subcutaneous FaDu human head and neck tumor xenografts were imaged with 18F-FDG using a Siemens Inveon PET/CT. The PET image was used to create an image-guided radiation treatment plan treating the entirety of the tumor with a 10Gy uniform radiation dose while sparing as much normal tissue as possible using a 15mm collimator. A dose escalation of 10 Gy was planned to treat the volume of highest FDG uptake within the tumor. To ensure localized dose distribution, the boost was to be delivered using dynamic arc techniques with a 5mm collimator. The isocenters for both fields were recorded on the planning PET image. The following day, the animals were anaesthetized, positioned in the SARRP irradiator, and imaged using on-board cone-beam to obtain an image in the treatment position. The planning CT was then deformably registered to the treatment CT using the BRAINSFit b-spline algorithm in SLICER 3D. Finally, the transform was applied to the planning PET and isocenters for the treatment fields were transferred to the treatment CT while the animal was still under anesthesia. The animal was then irradiated according to the original PET/CT-guided treatment plan.

Results:
SARRP allows for selective dose escalation treatments to small animal tumor models. In this study a subcutaneously grown tumor of 12mm in diameter was irradiated to 10Gy. The volume of the tumor characterized by increased FDG uptake received an additional 10Gy in the form of a 5mm-diameter boost delivered with non-coplanar arc field.

Conclusion:
The Small Animal Radiation Research Platform (SARRP) combined with a dedicated small animal PET/CT scanner enables pre-clinical validation of PET image-guided selective dose escalation in IMRT treatment.

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