A microCT scanner prototype

We have built a micro-CT scanner prototype for non-invasive morphological studies on small animals. The main components are a microfocus X-ray source with focal spot size of 30 μm and a X-ray detector composed by a CsI(Tl) scintillator coupled to a CCD. In a preliminary version of the prototype the source-detector system is kept fixed, and the object to be analyzed is placed on a rotating support. The main goal of this research project is to develop a micro-CT scanner to be integrated with the YAP-(S)PET scanner, in order to realize a multimodal PET/SPECT/CT tomograph. The performances of other readout systems (CMOS, single photon counting) for applications in small animals and mammography are also under investigation.

The microCT scanner prototype.

Phantom and organic specimen results with the CsI(Tl)+CCD detector

Images of phantoms and postmortem small animals have been reconstructed to evaluate the system performances. Using the edge method with a uniform PMMA cylindrical phantom, we obtain a spatial resolution of 14 lp/mm at 10% MTF, with cubic voxel size of 23.4³ μm³. The image COV varies between 10% for pixel size of 42 μm and 1% for pixel size of 500 μm, with a slice thickness of 23 μm and a dose of ~1.5 Gy.

Scanner performance measured following the method defined in the standard ASTM E1695-95, using a uniform PMMA cylindrical phantom. The scanning parameters are: 40 kVp, 418 mAs (over 1000 angles), cubic voxel size of 23.4³ μm³. The estimated dose in the FoV is ~1.5 Gy.

The scanning speed is strongly limited by the low photon fluence imposed by the source in use (witch has a maximum power of 10 W), so we are not yet able to perform in-vivo studies on small animals. We have carried out morphological studies on organic specimen; the images below refers to an anchovy and were acquired with an estimated dose of ~60 mGy.

Volumetric reconstruction of an anchovy. The scanning parameters are: 60 kVp, 31 mAs, cubic voxel of 92³ μm³. The estimated dose is ~60 mGy.

Literature

D.Panetta, E.Cicalini, N.Belcari, G.Baldazzi, A.Del Guerra, "A High Spatial Resolution CT Scanner Prototype for Small Animal Imaging", Biomedizinische Technik - Medical Physics vol.1, suppl.vol.1, pagg. 754-755, Proc. 14th International Conference of Medical Physics, Nuremberg, Germany, September 14-17, 2005.

"Standard Test Method for Measurements of Computed Tomography (CT) System Performances", ASTM, Designation: E1695-95, May 1995.