Room: Karl Dean Ballroom A1
Purpose: To advance image-guidance for soft tissue targets, our group developed a multi-projection, multi-spectral bioluminescence tomography(BLT) to guide SARRP irradiation. Our new developments include multi-projection bioluminescence images(BLIs) registration, surface flux correction, and in vivo time-resolved signal calibration. Our system and calibration methods are expected to provide new quantitative imaging modality for pre-clinical radiation research.
Methods: Our system consists of an optical assembly, a mobile cart and a moveable mouse bed(Fig 1). The bed allows animal imaged in BLT system and transferred to SARRP for CBCT and irradiation. A 3-mirror-filter system is adopted to acquire multi-projection BLIs at 590-650nm by rotating mirrors. A geometrical registration method based on pinhole camera model was developed to register the 2D BLIs, at any projection, to the 3D animal surface generated from the CBCT image. An analytical method using diffusion approximation was developed to correct the surface signal/flux measurement dependence on the imaging perspective relative to the camera location. Because in vivo bioluminescence signal changed overtime, unfiltered imaging and extra- and interpolation method were used to correct the signal. The calibrated, multi-projection BLIs were used with eigenvector expansion algorithm to complete BLT reconstruction. Phantom and glioblastoma(GBM) mouse model are used to validate the localization accuracy of the system.
Results: The geometrical registration accuracy is within 0.4mm(Fig 2). Our surface flux calibration method can accurately correct the surface data within 6% accuracy in pre-selected data range(Fig 3). We have characterized in vivo signal variation to correct the contribution of the multi-spectral BLIs taken at different time points(Fig 4). Our initial result shows that our system can reconstruct approximated GBM volume at 0.4mm localization accuracy(Fig 5) by comparing the center of mass between BLT and contrast-CBCT target volume.
Conclusion: We expect our BLT-SARRP system will provide a novel molecular optical guidance modality for pre-clinical radiation study.
Funding Support, Disclosures, and Conflict of Interest: Drs. Wong and Iordachita receive royalty payment from a licensing agreement between Xstrahl Ltd. and Johns Hopkins University.