The second generation HRRT - a multi-centre scanner performance investigation

The high resolution research tomograph (HRRT) is one of the most complex existing positron emission tomographs: it is the only human size scanner capable of decoding the depth of the γ-ray interaction in the crystal, using a lutetium LSO/LYSO phoswich detector arrangement. In this study we determined basic scanner hardware characteristics, such as scanner data acquisition stability, and their variability across eleven centres. In addition a subset of the NEMA NU-2001 standards measurements was performed. We found (i) significant variability in the DOI decoding results between centres, (ii) a trend toward an increasing number of detected true coincident events as a function of elapsed time from scanner calibration likely due to a shifting energy spectrum, (iii) a count-rate dependent layer identification, (iv) scatter fraction ranging from ∼ 42% to 54% where the variability was partly related to the shifting of the energy spectrum, (v) sensitivity ranging from ∼5.5% to 6.5% across centres, (vi) resolution of ∼(2.5 mm)³, fairly consistent across centres, (vii) image quality which is very comparable to other scanners.