A 3D HIDAC-PET camera with sub-millimetre resolution for imaging small animals

A HIDAC-PET camera consisting essentially of 5 million 0.5mm gas avalanching detectors has been constructed for small-animal imaging. The particular HIDAC advantage - a high 3D spatial resolution - has been improved to 0.95mm fwhm and to 0.7mm fwhm when reconstructing with 3D-OSEM methods incorporating resolution recovery. A depth-of-interaction resolution of 2.5mm is implicit, due to the laminar construction. Scatter-corrected sensitivity, at 8.9cps/kBq (i.e. 0.9%) from a central point source, or 7.2cps/kBq (543cps/kBq/cm(3)) from a distributed (40mm diameter, 60mm long) source is now much higher than previous, and other, work. A field-of-view of 100mm (adjustable to 200mm) diameter by 210mm axially permits whole-body imaging of small animals, containing typically 4MBqs of activity, at 40kcps of which 16% are random coincidences, with a typical scatter fraction of 44%. Throughout the field-of-view there are no positional distortions and relative quantitation is uniform to +/-3.5%, but some variation of spatial resolution is found. The performance demonstrates that HIDAC technology is quite appropriate for small-animal PET cameras.