Single scan parameterization of space-variant point spread functions in image space via a printed array: the impact for two PET/CT scanners

Abstract

A bstractIncorporation of a resolution model during statistical image reconstruction often produces images of improved resolution and signal-to-noise ratio (SNR). A novel and practical methodology to rapidly and accurately determine the overall emission and detection blurring component of the system matrix using a printed point source array within a custom-made Perspex phantom is presented. The array was scanned at different positions and orientations within the field of view (FOV) to examine the feasibility of extrapolating the measured point source blurring to other locations in the FOV and the robustness of measurements from a single point source array scan. We measured the spatially-variant image based blurring on two PET/CT scanners, the B-Hi-Rez and the TruePoint TrueV. These measured spatiallyvariant kernels and the spatially-invariant kernel at the FOV centre were then incorporated within an ordinary Poisson ordered subsets expectation maximization (OP-OSEM) algorithm and compared to resolution modelling. Comparisons were based on a point source array, the NEMA IEC image quality phantom, the Cologne resolution phantom and 2 clinical studies (carbon-11 labelled anti-sense oligonucleotide [ 11 C]-ASO and fluorine-18 labelled fluoro-L-thymidine [ 18 F]-FLT). Robust and accurate measurements of spatially-variant image blurring were successfully obtained from a single scan. Spatially-variant resolution modelling resulted in notable resolution improvements away from the centre of the FOV. Comparison between spatiallyvariant image-space methods and the projection-space approach (the first such report, using a range of studies for two distinct PET/CT systems) demonstrated very similar performance with our image-based implementation producing slightly better contrast recovery (CR) for the same level of image roughness (IR). These results demonstrate that image-based resolution modelling within reconstruction is a valid alternative to projection based modelling, and that, when using the proposed practical methodology, the necessary resolution measurements can be obtained from a single scan. This approach avoids the relatively time-consuming and involved procedures previously proposed in the literature.

Resolution modeling in PET imaging: Theory, practice, benefits, and pitfalls

“…Further generalizations by (i) Rahmim et al, 67 (ii) Rapisarda et al, 62 (iii) Cloquet et al, 49 and (iv) Kotasidis et al 61 used space-varying blurring kernels [as estimated from (i)-(iii) regular line or point sources or (iv) simultaneously printed 68,69 point sources]. This included additional inclusion of (i)-(v) anisotropicity, (ii)-(iii) asymmetry, and (iii)-(iv) non-Gaussianity to better model the PSF.…”

A 5D computational phantom for pharmacokinetic simulation studies in dynamic emission tomography

“…The generated projection data were reconstructed using in-house developed image reconstruction software capable of reconstructing data from the Biograph 6 HiRez PET/CT [36]. Data from were reconstructed using an ordinary…”

Full field spatially-variant image-based resolution modelling reconstruction for the HRRT

“…[5]). Alternatively, the system response function can be obtained via physical point source measurements across the entire FOV [6,7].…”

“…Refs. [7,10]) or (iii) using a combination of projection and image space modelling [11]. Although all these approaches pose different advantages and disadvantages, in practice, as shown by Ref.…”

“…Although all these approaches pose different advantages and disadvantages, in practice, as shown by Ref. [7], there are only minor differences in terms of resolution recovery.…”