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The high-resolution oncologic transformable PET (HOTPET) camera can operate in several modes including a whole-body mode and a brain mode. In the whole-body mode, the HOTPET camera has a transverse field-of-view (FOV) of 60 cm and an axial FOV of 13 cm. In the brain mode, it has a transverse FOV of 39 cm and an axial FOV of 21 cm. We compared the performance of the two modes of the HOTPET camera for detecting small brain lesions ( <; 10mm). We also generated data for a whole-body PET camera with crystals twice the average size of the HOTPET's crystals by rebinning HOTPET body mode data for comparison with HOTPET data. The purpose of this work was to investigate the effective gain in lesion detection by using a dedicated brain PET camera with high sensitivity and high spatial resolution over a whole-body PET camera. To accomplish this, we scanned a Hoffman brain phantom with three small, spherical lesion inserts for several lesion activity contrasts in both modes of the HOTPET camera. The inner diameters of the lesion inserts were 3.95 mm, 4.95 mm, and 7.86 mm. The ratio of the activity concentration in the lesions to the activity in the background (gray matter regions) ranged from 1 to 20. Images of the lesion inserts were reconstructed and they were compared by visual inspection and also by measuring the contrast of lesions and studying their radial profiles. On visual inspection, the 7.86-mm lesion with a lesion-to-background activity ratio of 2 or higher was clearly identifiable in both modes of the HOTPET camera. The 4.95-mm lesion was observable with a lesion-to-background activity ratio of 4 or higher in the HOTPET brain mode, 5.5 or higher in the HOTPET whole-body mode, and 8 or higher for the rebinned whole-body data. The 3.95-mm lesion was observable with a lesion-to-background activity ratio of 8 or higher in the brain mode and of 11 (16) or higher in the HOTPET (rebinned) whole-body mode. This study demonstrated the potential advantage of the brain - ode of the HOTPET camera over the whole-body mode, and especially over the rebinned data generated for a whole-body PET camera with larger crystals, for detecting small brain lesions ( <; 7 mm).
Date of Publication: June 2011