Physical performance of adaptive axial FOV PET scanners with a sparse detector block rings or a checkerboard configuration

Abstract

Objective: Using Monte-Carlo simulations, we evaluated the physical performance of a hypothetical state-of-the-art clinical PET scanner with adaptive axial field-of-view (AFOV) based on the validated GATE model of the Siemens Biograph VisionTM PET/CT scanner. Approach: Vision consists of 16 compact PET rings, each consisting of 152 mini-blocks of 5 × 5 Lutetium Oxyorthosilicate crystals (3.2 × 3.2 × 20 mm3). The Vision 25.6 cm AFOV was extended by adopting (i) a sparse mini-block ring (SBR) configuration of 49.6 cm AFOV, with all mini-block rings interleaved with 16 mm axial gaps, or (ii) a sparse mini-block checkerboard (SCB) configuration of 51.2 cm AFOV, with all mini-blocks interleaved with gaps of 16 mm (transaxial) × 16 mm (axial) width in checkerboard pattern. For sparse configurations, a “limited” continuous bed motion (limited-CBM) acquisition was employed to extend AFOVs by 2.9 cm. Spatial resolution, sensitivity, image quality (IQ), NECR and scatter fraction were assessed per NEMA NU2-2012. Main Results: All IQ phantom spheres were distinguishable with all configurations. SBR and SCB percent contrast recovery (% CR) and background variability (% BV) were similar (p-value>0.05). Compared to Vision, SBR and SCB %CRs were similar (p-values>0.05). However, SBR and SCB %BVs were deteriorated by 30% and 26% respectively (p-values<0.05). SBR, SCB and Vision exhibited system sensitivities of 16.6, 16.8, and 15.8 kcps/MBq, NECRs of 311 kcps @35 kBq/cc, 266 kcps @25.8 kBq/cc, and 260 kcps @27.8 kBq/cc, and scatter fractions of 31.2%, 32.4%, and 32.6%, respectively. SBR and SCB exhibited a smoother sensitivity reduction and noise enhancement rate from AFOV center to its edges. SBR and SCB attained comparable spatial resolution in all directions (p-value>0.05), yet, up to 1.5 mm worse than Vision (p-values<0.05). Significance: The proposed sparse configurations may offer a clinically adoptable solution for cost-effective adaptive AFOV PET with either highly-sensitive or long-AFOV acquisitions.

The detection instrumentation and geometric design of clinical PET scanner: towards better performance and broader clinical applications

“…It is also possible to efficiently obtain a large amount of PET data encompassing the entire thorax in a single breath-hold. This approach effectively mitigates motion artefacts caused by breathing and improves PET-CT registration and PET quantification accuracy [181]. In addition, this reduction in acquisition time makes it more comfortable for patients suffering pain during the examination with minimal motion artefacts.…”

The potential of a medium-cost long axial FOV PET system for nuclear medicine departments

“…2. A sparse long axial FOV PET design of about 1-1.4 m, but with ~ 50% reduced manufacturing cost, by eliminating ~ 50% of the detector elements or blocks This design concept delivers large system sensitivity gains in body imaging, about 4 × less than a fully populated 1-m axial FOV TB-PET system, but still 4 × higher than a standard 25-cm axial FOV scanner [13][14][15][16][17]. Regarding peak axial slice sensitivity, a gain reduced by 2 times relative to a full 100 cm but still 2 times higher than a full 25-cm axial FOV PET system is expected.…”

“…Furthermore, thanks to the above sensitivity performance specifications, the sparse configuration attains the smallest axial variance in axial slice sensitivity between the centers and the edges of the axial FOV, thus resulting in the smallest axial noise variance in the reconstructed images, compared to a full 100-cm-long TB-PET system. Studies have shown that the introduction of a relatively large number of small axial gaps uniformly distributed between the existing detector elements or blocks can result in artifact-less reconstructed images of nearly doubling the axial FOV, similar NEMA contrast recovery and only a slightly elevated background image noise [13][14][15][16][17]. These results are a consequence of sparse detector designs taking advantage of the redundancy of data used in the 3D reconstruction.…”

Investigation of Novel Preclinical Total Body PET Designed With J-PET Technology: A Simulation Study

“…All the mentioned facts motivate the investigation to find a cost-effective solution to reduce the final construction cost of TB PET [7]. One of the recently suggested solutions is the sparse detector configuration [18,19]. In the proposed sparse geometry, there are intervals between detectors leading to large AFOV with less number of scintillation crystals and electronics.…”