Anatomically-guided deconvolution of PET using directional total variation regularization

Abstract. Positron emission tomography (PET) provides quantitative functional imaging of biomarkers unavailable in other modalities, however, images are of relatively low resolution compared to modalities such as magnetic resonance imaging (MRI). A typical approach is to reconstruct to a higher resolution and regularize using a structural image, but there are practical limitations to this approach. Alternatively, post-reconstruction approaches involve image-based correction, but typically rely on a segmentation which may be difficult or even ambiguous to find, depending on the anatomical region or deformities. Here, we perform super-resolution by utilising iterative deconvolution, regularized by minimizing shared directional total variation (dTV) with an anatomical MRI image. We present results on synthetic and clinical data. For the former, PET acquisitions were simulated using an analytic PET simulation. The Gaussian blurring model parameters for deconvolution were optimized on a simplistic phantom simulation with a total variation prior. This model was then applied to deconvolve realistic synthetic data using dTV, which was synthesized to include PET-unique lesions. The model was also applied to a single 18F-florbetaben study acquired over 10 minutes. Gray matter-white matter contrast increased using dTV compared with baseline, however, where an accurate segmentation is available, traditional partial volume correction techniques are superior. Hence, dTV-regularised deconvolution can perform PVC and super-resolution in situations where a reliable segmentation cannot be achieved. With appropriate hyper-parameter selection, dTV deconvolution can preserve PET-unique features. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement KT acknowledges support from the UK EPSRC grants Computational Collaborative Project in Synergistic PET/MR Reconstruction (CCP PETMR) EP/M022587/1 and its associated Software Flagship project EP/P022200/1; the Computational Collaborative Project in Synergistic Reconstruction for Biomedical Imaging (CCP SyneRBI) EP/T026693/1. EPap and EPas acknowledge support from the UK EPSRC grants A Reconstruction Toolkit for Multichannel CT (EP/P02226X/1), CCPi: Collaborative Computational Project in Tomographic Imaging (EP/M022498/1 and EP/T026677/1). CD acknowledges support from EPSRC grant PET++: Improving Localization, Diagnosis and Quantification in Clinical and Medical PET Imaging with Randomized Optimization: (EP/S026045/1). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The QIMR Berghofer Medical Research Institute-Human Research Ethics Committee of QIMR Berghofer Medical Research Institute gave ethical approval for this work (P2193). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All non-human data produced in the present study are available upon reasonable request to the authors