Small animal optical multispectral Cerenkov tomography

A novel pre-clinical imaging modality called Cerenkov luminescence imaging (CLI) has been recently introduced for small animals in vivo imaging. CLI is based on the detection of optical Cerenkov radiation generated by beta particles as they travel into the animal tissues with energy greater than Cerenkov threshold. The main goal of this work is the development of a novel optical image reconstruction method called multi spectral Cerenkov luminescence tomography (msCLT). The starting point of the msCLT reconstruction scheme is a set of 2D planar images acquired using several narrow bandpass filters. Because of the different tissues absorption at different wavelengths this provide distinctive information content that can be used for image reconstruction. More precisely the msCLT algorithm is based on a regularized iterative non-negative scheme in order to find the unknown source intensity solution, the theoretical Cerenkov emission spectrum was also included in the algorithm. In order to investigate the performances of the msCLT approach in vitro and in vivo imaging using ³²P-ATP were performed by using the IVIS 200 (Caliper, a PerkinElmer company). A set of spatial resolution measurements were performed using a small capillary source placed between several slices of chicken breast at different depths. The spatial resolution obtained from the msCLT reconstructed images of the capillary showed that the FWHM is 1.5 mm for a source placed at 6 mm depth. In order to investigate the in vivo performances of the msCLT reconstruction method, a control nude mice injected with 10 MBq of 32P-ATP were imaged. Whole body MRI was acquired to provide an anatomical localization of the Cerenkov emission. msCLT reconstructed images co-registered with MRI images showed that the Cerenkov emission regions matches well with anatomical regions, such as the brain, heart and abdomen. These results were also confirmed by ex vivo imaging of organs such as intestine, brain, heart and ribs.