Euromedim 2006 :1st European Conference on Molecular Imaging Technology

Preliminary evaluation of the tomographic performance of the MediSPECT small animal imaging system

11 May 2006, 14:00

1h

Palais du Pharo, Marseille

poster • Status of animal and clinical PET, SPECT and CT (biomedical and technical) Poster session : Imaging systems, Molecular Imaging

Speaker

Dr Maria Cristina Montesi (Dipartimento di Scienze Fisiche, Università di Napoli Federico II, and INFN, Sezione di Napoli, I-80126 Napoli, Italy)

Description

We report on the tests of a prototype (MediSPECT) for SPECT imaging on small animals with a small field of view (FOV) and high spatial resolution. MediSPECT is a SPECT imaging system based on a 1-mm thick CdTe pixel detector bump-bonded to the Medipix2 CMOS readout circuit operating in single-photon counting developed by the European Medipix2 collaboration. The CdTe detector has 256x256 square pixels, 55 micron by side, for a sensitive area 14 mm x 14 mm. In its present version, this system has a single detector head mounted on a rotating gantry. A detailed description of MediSPECT is reported in a companion work presented at this conference. For preliminary testing and calibration of the acquisition equipment and image reconstruction algorithms, 90 projections of a gamma-ray point source (403 kBq Cd-109) through a single pinhole (diameter 0.75 mm; radius of rotation about 2.5 cm; focal length about 4.5 cm) were acquired in a step-and-shoot mode. A sensitivity of 4 cps/MBq (at 22 keV) was measured. Capillaries 800 micron in diameter were arranged in a Y shape to form a more complex phantom (45 projections, about 1 mCi I-125). Images were reconstructed with a custom algorithm implementing OSEM. Given the high resolution that the system seeks to ultimately achieve, the code incorporates center of rotation correction. Results show successful image reconstruction of these simple phantoms. In the near future, we expect to be able to image more complex phantoms as a preliminary step to further validate the methods so far developed for the long-term goal of high- resolution (<~300 micron) in vivo imaging over a small field of view with single as well as multiple pinhole optics.