HRRT and Advance scanner comparison using a steady-state scan approach

Objectives With the Siemens HRRT scanner, it is possible to acquire PET images with a higher resolution (< 2mm) than with the clinical GE Advance scanner. For many purposes, it is essential that the acquired HRRT images is quantitative correct. A bolus-infusion approach is optimal for examination of this as both scans can be performed under steady-state conditions.

Methods Using a bolus-infusion scheme (Pinborg, 2003), altanserin tracer images of the 5HT-2A receptor distribution in the brain have been acquired under steady-state conditions for two normal healthy volunteers. First, the subjects were scanned at the Advance scanner (40 min) and afterwards at the HRRT scanner (30 min). The HRRT scans were reconstructed using the new iterative PSF reconstruction with attenuation map improvements (Surry, Comtat, 2008). A Gaussian filter with a FWHM of 10 mm was used to match HRRT images to Advance scanner resolution. Regions of interests were delineated (Svarer, 2004) and these were used for extraction of mean regional values. Scatter plots of the Advance (X axis) and HRRT (Y axis) regional values were generated and the slope of a fitted line was found.

Results The slopes for the original HRRT images were (1.13 and 1.11) and for the resolution matched HRRT images (1.05 and 0.99). For the resolution matched images, the slope is very close to the expected value of 1. The original HRRT images show a higher contrast between high and low binding areas.

Conclusions Using this very stable bolus-infusion approach, it has been possible to compare scans from the HRRT and Advance scanner. As shown, there is a nice correlation between extracted regional values from the two scanners. Three more subjects will be included to confirm this.