Abstract
BackgroundThe Siemens high-resolution research tomograph (HRRT - a dedicated brain PET scanner) is to this day one of the highest resolution PET scanners; thus, it can serve as useful benchmark when evaluating performance of newer scanners. Here, we report results from a cross-validation study between the HRRT and the whole-body GE SIGNA PET/MR focusing on brain imaging.Phantom data were acquired to determine recovery coefficients (RCs), % background variability (%BG), and image voxel noise (%). Cross-validation studies were performed with six healthy volunteers using [11C]DTBZ, [11C]raclopride, and [18F]FDG. Line profiles, regional time-activity curves, regional non-displaceable binding potentials (BPND) for [11C]DTBZ and [11C]raclopride scans, and radioactivity ratios for [18F]FDG scans were calculated and compared between the HRRT and the SIGNA PET/MR.ResultsPhantom data showed that the PET/MR images reconstructed with an ordered subset expectation maximization (OSEM) algorithm with time-of-flight (TOF) and TOF + point spread function (PSF) + filter revealed similar RCs for the hot spheres compared to those obtained on the HRRT reconstructed with an ordinary Poisson-OSEM algorithm with PSF and PSF + filter. The PET/MR TOF + PSF reconstruction revealed the highest RCs for all hot spheres. Image voxel noise of the PET/MR system was significantly lower. Line profiles revealed excellent spatial agreement between the two systems. BPND values revealed variability of less than 10% for the [11C]DTBZ scans and 19% for [11C]raclopride (based on one subject only). Mean [18F]FDG ratios to pons showed less than 12% differences.ConclusionsThese results demonstrated comparable performances of the two systems in terms of RCs with lower voxel-level noise (%) present in the PET/MR system. Comparison of in vivo human data confirmed the comparability of the two systems. The whole-body GE SIGNA PET/MR system is well suited for high-resolution brain imaging as no significant performance degradation was found compared to that of the reference standard HRRT.
Highlights
The Siemens high-resolution research tomograph (HRRT - a dedicated brain Positron emission tomography (PET) scanner) is to this day one of the highest resolution PET scanners; it can serve as useful benchmark when evaluating performance of newer scanners
2.5 filter the highest Recovery coefficient (RC) for all hot spheres of the contrast phantom scanned on the PET/magnetic resonance (MR) were obtained from the TOF + point spread function (PSF) reconstruction, while the lowest RCs were obtained by applying post-filtering without PSF correction (Fig. 2a)
For the contrast phantom scanned on the High-resolution research tomograph (HRRT) (Fig. 2c), similar RCs were obtained from the PSF reconstruction with and without filter for all spheres except for the smallest one (PSF: 54.4%; PSF + filter: 49.5%)
Summary
The Siemens high-resolution research tomograph (HRRT - a dedicated brain PET scanner) is to this day one of the highest resolution PET scanners; it can serve as useful benchmark when evaluating performance of newer scanners. The high resolution research tomograph (HRRT, CTI PET Systems, Knoxville, TN, USA), introduced in the late 1990s/early 2000s, is to this day arguably one of the highest resolution PET scanners for human brain imaging [6]. Even though in most cases dedicated brain PET scanners would be preferred for cost, and potentially better sensitivity and resolution performance, the choice is generally practically limited to whole-body hybrid systems, i.e., whole-body PET systems in combination with computed tomography (CT) or magnetic resonance (MR) imaging, as standalone dedicated PET systems such as the HRRT are no longer available or common. The PET detectors are integrated in the MR bore allowing whole-body simultaneous acquisition of PET and MR [8] with high PET detection stability [9]
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