Euromedim 2006 :1st European Conference on Molecular Imaging Technology

Whole body small animal examination with a diffuse optical tomography instrument.

10 May 2006, 15:15

15m

Palais du Pharo, Marseille

oral S3_S4 others modalities Other Modalities

Speaker

Dr Anne Koenig (LETI - CEA Recherche Technologique)

Description

Three dimensional Optical Diffusion Tomography allows in vivo studies of tumour life without any stress or damage for the animal. We present hereafter theoretical and experimental results obtained with the system developed in our laboratory on phantoms and mice. The experimental set-up consists of a laser source (690nm) coupled to a motorized stage, a CCD camera and a tank to receive the animal. The excitation and emission wavelengths of the system and the fluorophore are chosen to optimize transmission through the whole animal (leaver, lungs …). The acquisition geometry is considered as infinite in (x, y) directions and of thickness z varying from 10 to 15mm. For mice acquisitions, this is achieved by immersing them in an index matching medium. Reconstruction is performed through an ART algorithm based upon a fine description of material-light interaction taking into account diffusion as well as absorption phenomena. A first study on phantoms was conducted to evaluate depth resolution: two glass capillary tubes filled with Cy5 (diameter=1 mm, Length=20 mm) separated in z by various distances (axis to axis) are immersed in a diffusing medium. A depth resolution of 4mm is achieved on simulation and of 4,5mm on experimentation. A second study is performed on mice. 4 healthy mice and 13 lung metastasis bearing mice (mammary murine tumour) are imaged at different stages of the tumour development: 12, 13, or 14 days after the primary implantation. Acquisitions are made 3 hours after intravenous injection of 150 microgramme Transferine/Alexa 750. The reconstruction of the fluorophores concentration for a healthy mouse shows roughly nothing in the lungs. They are slightly visible on the volume slices showing very little fluorescence. Only a few markers concentrate in the lungs. The same reconstruction done for mice bearing tumours shows, on the contrary an accumulation of fluorophores in the lungs. A control study has been conducted on two mice bearing a 14 days old tumour that are non-injected with Transferine/Alexa 750. In this case, the reconstruction area does not present any fluorescence. These first results show our system performances for reconstructing whole body mice in slab geometry even in the area of the lungs. Detection and localization of the fluorophore fixations are presented according to the stage of the tumour development. Our results show that the system is able to separate healthy from cancerous mice. We have compared these results to the FRI signal observed on lungs of dissected mice.