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

A HIDAC-PET camera consisting essentially of 5 million 0.5 mm gas avalanching detectors has been constructed for small-animal imaging. The particular HIDAC advantage-a high 3D spatial resolution”has been improved to 0.95 mm fwhm and to 0.7 mm fwhm when reconstructing with 3D-OSEM methods incorporating resolution recovery. A depth-of-interaction resolution of 2.5 mm is implicit, due to the laminar construction. Scatter-corrected absolute sensitivity, at 8.9 cps/kBq (i.e. 0.9%) from a central point source, or 7.2 cps/kBq from a distributed (60 mm diameter, 70 mm long) source is now much higher than previous work. A field-of-view of 100 mm (adjustable to 200 mm) diameter by 200 mm axially permits whole-body imaging of small animals, containing typically 4 MBqs of activity, at 40 kcps of which 16% are random coincidences, with a maximum 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