Total-body positron emission tomography: a tool for systemic, quantitative evaluation of the inflammatory burden of psoriatic arthritis.

Objectives: To test the hypothesis that recently-developed total body-positron emission tomography (TB-PET) imaging with integrated computed tomography (CT) will enable low-dose, quantitative, domain-specific evaluation of the total inflammatory burden of psoriatic arthritis (PsA), and associate with established outcome measures of the clinical domains of PsA.

Methods: Seventy-one adult participants (40 with PsA, 16 with rheumatoid arthritis (RA), and 15 with osteoarthritis (OA)) underwent 20-min TB-PET/CT scans using [18F]FDG, a glucose analogue radiotracer. [18F]FDG uptake was assessed qualitatively and quantitatively.

Role of Total Body PET/CT in Inflammatory Disorders.

Inflammatory disorders historically have been difficult to monitor with conventional PET imaging due to limitations including radiation exposure, lack of validated imaging biomarkers, low spatial resolution, and long acquisition durations. However, the recent development of long-axial field-of-view (LAFOV) PET/CT scanners may allow utilization of novel noninvasive biomarkers to diagnose, predict outcomes, and monitor therapeutic response of inflammatory conditions. LAFOV PET scanners can image most of the human body (if not the entire body) simultaneously in one bed position, with improved signal collection efficiency compared to conventional PET scanners.

Feasibility of PET-enabled dual-energy CT imaging: First physical phantom and initial patient study results.

Purpose: Dual-energy (DE) CT enables material decomposition by using two different x-ray energies and may be combined with PET for improved multimodality imaging. However, this increases radiation dose and may require a hardware upgrade due to the added second x-ray CT scan. The recently proposed PET-enabled DECT method allows dual-energy imaging using a conventional PET/CT scanner without the need to change scanner hardware or increase radiation exposure.

Quantitative Total-Body Imaging of Blood Flow with High Temporal Resolution Early Dynamic F-Fluorodeoxyglucose PET Kinetic Modeling.

Unlabelled: Quantitative total-body PET imaging of blood flow can be performed with freely diffusible flow radiotracers such as O-water and C-butanol, but their short half-lives necessitate close access to a cyclotron. Past efforts to measure blood flow with the widely available radiotracer F-fluorodeoxyglucose (FDG) were limited to tissues with high F-FDG extraction fraction. In this study, we developed an early-dynamic F-FDG PET method with high temporal resolution kinetic modeling to assess total-body blood flow based on deriving the vascular transit time of F-FDG and conducted a pilot comparison study against a C-butanol reference.

The role of brown adipose tissue in branched-chain amino acid clearance in people.

Brown adipose tissue (BAT) in rodents appears to be an important tissue for the clearance of plasma branched-chain amino acids (BCAAs) contributing to improved metabolic health. However, the role of human BAT in plasma BCAA clearance is poorly understood. Here, we evaluate patients with prostate cancer who underwent positron emission tomography-computed tomography imaging after an injection of F-fluciclovine (L-leucine analog).

Refining penalty parameter selection in whole-body PET image reconstruction for lung cancer patients using the cross-validation log-likelihood method.

Penalty parameters in penalized likelihood positron emission tomography (PET) reconstruction are typically determined empirically. The cross-validation log-likelihood (CVLL) method has been introduced to optimize these parameters by maximizing a CVLL function, which assesses the likelihood of reconstructed images using one subset of a list-mode dataset based on another subset. This study aims to validate the efficacy of the CVLL method in whole-body imaging for cancer patients using a conventional clinical PET scanner.

Quantitative PET imaging and modeling of molecular blood-brain barrier permeability.

Blood-brain barrier (BBB) disruption is involved in the pathogenesis and progression of many neurological and systemic diseases. Non-invasive assessment of BBB permeability in humans has mainly been performed with dynamic contrast-enhanced magnetic resonance imaging, evaluating the BBB as a structural barrier. Here, we developed a novel non-invasive positron emission tomography (PET) method in humans to measure the BBB permeability of molecular radiotracers that cross the BBB through different transport mechanisms.

Total-Body Parametric Imaging Using Relative Patlak Plot.

Standard Patlak plot is widely used to describe FDG kinetics for dynamic PET imaging. Whole-body Patlak parametric imaging remains constrained due to the need for a full-time input function. Here, we demonstrate the Relative Patlak (RP) plot, which eliminates the need for the early-time input function, for total-body parametric imaging and its application to clinical 20-min scan acquired in list-mode.

Cloud-based serverless computing enables accelerated monte carlo simulations for nuclear medicine imaging.

This study investigates the potential of cloud-based serverless computing to accelerate Monte Carlo (MC) simulations for nuclear medicine imaging tasks. MC simulations can pose a high computational burden-even when executed on modern multi-core computing servers. Cloud computing allows simulation tasks to be highly parallelized and considerably accelerated.

Performance Characteristics of the NeuroEXPLORER, a Next-Generation Human Brain PET/CT Imager.

The collaboration of Yale, the University of California, Davis, and United Imaging Healthcare has successfully developed the NeuroEXPLORER, a dedicated human brain PET imager with high spatial resolution, high sensitivity, and a built-in 3-dimensional camera for markerless continuous motion tracking. It has high depth-of-interaction and time-of-flight resolutions, along with a 52.4-cm transverse field of view (FOV) and an extended axial FOV (49.

Dose Reduction in Pediatric Oncology Patients with Delayed Total-Body [F]FDG PET/CT.

Our aim was to define a lower limit of reduced injected activity in delayed [F]FDG total-body (TB) PET/CT in pediatric oncology patients. In this single-center prospective study, children were scanned for 20 min with TB PET/CT, 120 min after intravenous administration of a 4.07 ± 0.

Optimization-derived blood input function using a kernel method and its evaluation with total-body PET for brain parametric imaging.

Unlabelled: Dynamic PET allows quantification of physiological parameters through tracer kinetic modeling. For dynamic imaging of brain or head and neck cancer on conventional PET scanners with a short axial field of view, the image-derived input function (ID-IF) from intracranial blood vessels such as the carotid artery (CA) suffers from severe partial volume effects. Alternatively, optimization-derived input function (OD-IF) by the simultaneous estimation (SIME) method does not rely on an ID-IF but derives the input function directly from the data.

High-Temporal-Resolution Kinetic Modeling of Lung Tumors with Dual-Blood Input Function Using Total-Body Dynamic PET.

The lungs are supplied by both the pulmonary arteries carrying deoxygenated blood originating from the right ventricle and the bronchial arteries carrying oxygenated blood downstream from the left ventricle. However, this effect of dual blood supply has never been investigated using PET, partially because the temporal resolution of conventional dynamic PET scans is limited. The advent of PET scanners with a long axial field of view, such as the uEXPLORER total-body PET/CT system, permits dynamic imaging with high temporal resolution (HTR).

Super-resolution reconstruction of -ray CT images for PET-enabled dual-energy CT imaging.

Dual-energy computed tomography (DECT) enables material decomposition for tissues and produces additional information for PET/CT imaging to potentially improve the characterization of diseases. PET-enabled DECT (PDECT) allows the generation of PET and DECT images simultaneously with a conventional PET/CT scanner without the need for a second x-ray CT scan. In PDECT, high-energy -ray CT (GCT) images at 511 keV are obtained from time-of-flight (TOF) PET data and are combined with the existing x-ray CT images to form DECT imaging.

Feasibility of PET-enabled dual-energy CT imaging: First physical phantom and initial patient results.

X-ray computed tomography (CT) in PET/CT is commonly operated with a single energy, resulting in a limitation of lacking tissue composition information. Dual-energy (DE) spectral CT enables material decomposition by using two different x-ray energies and may be combined with PET for improved multimodality imaging, but would either require hardware upgrade or increase radiation dose due to the added second x-ray CT scan. Recently proposed PET-enabled DECT method allows dual-energy spectral imaging using a conventional PET/CT scanner without the need for a second x-ray CT scan.

Development of a Monte Carlo-based scatter correction method for total-body PET using the uEXPLORER PET/CT scanner.

This study presents and evaluates a robust Monte Carlo-based scatter correction (SC) method for long axial field of view (FOV) and total-body positron emission tomography (PET) using the uEXPLORER total-body PET/CT scanner.Our algorithm utilizes the Monte Carlo (MC) tool SimSET to compute SC factors in between individual image reconstruction iterations within our in-house list-mode and time-of-flight-based image reconstruction framework. We also introduced a unique scatter scaling technique at the detector block-level for optimal estimation of the scatter contribution in each line of response.

Practical Considerations for Total-Body PET Acquisition and Imaging.

The world's first total-body PET/CT system has been in routine clinical and research use at UC Davis since 2019. The uEXPLORER total-body PET scanner has been designed with an axial field-of-view long enough to completely encompass most human subjects (194 cm or 76 inches long), allowing for a 15-68-fold gain in the PET signal collection efficiency over conventional PET scanners. A high-sensitivity PET scanner that can image the entire subject with a single bed position comes with new benefits and challenges to consider for efficient and practical use.

Supplemental Transmission Aided Attenuation Correction for Quantitative Cardiac PET.

Quantitative PET attenuation correction (AC) for cardiac PET/CT and PET/MR is a challenging problem. We propose and evaluate an AC approach that uses coincidences from a relatively weak and physically fixed sparse external source, in combination with that from the patient, to reconstruct μ -maps based on physics principles alone. The low 30 cm3 volume of the source makes it easy to fill and place, and the method does not use prior image data or attenuation map assumptions.

First-in-human immunoPET imaging of COVID-19 convalescent patients using dynamic total-body PET and a CD8-targeted minibody.

With most of the T cells residing in the tissue, not the blood, developing noninvasive methods for in vivo quantification of their biodistribution and kinetics is important for studying their role in immune response and memory. This study presents the first use of dynamic positron emission tomography (PET) and kinetic modeling for in vivo measurement of CD8 T cell biodistribution in humans. A Zr-labeled CD8-targeted minibody (Zr-Df-Crefmirlimab) was used with total-body PET in healthy individuals ( = 3) and coronavirus disease 2019 (COVID-19) convalescent patients ( = 5).

Numerical investigation reveals challenges in measuring the contrast recovery coefficients in PET.

Contrast recovery coefficient (CRC) is essential for image quality (IQ) assessment in positron emission tomography (PET), typically measured according to the National Electrical Manufacturers Association (NEMA) NU 2 standard. This study quantifies systematic uncertainties of the CRC measurement by a numerical investigation of the effects from scanner-independent parameters like voxel size, region-of-interest (ROI) misplacement, and sphere position on the underlying image grid.CRC measurements with 2D and 3D ROIs were performed on computer-generated images of a NEMA IQ-like phantom, using voxel sizes of 1-4 mm for sphere diameters of 5-40 mm-first in absence of noise and blurring, then with simulated spatial resolution and image noise with varying noise levels.

Total-Body Perfusion Imaging with [C]-Butanol.

Tissue perfusion can be affected by physiology or disease. With the advent of total-body PET, quantitative measurement of perfusion across the entire body is possible. [C]-butanol is a perfusion tracer with a superior extraction fraction compared with [O]-water and [N]-ammonia.

Total-Body Multiparametric PET Quantification of F-FDG Delivery and Metabolism in the Study of Coronavirus Disease 2019 Recovery.

Conventional whole-body static F-FDG PET imaging provides a semiquantitative evaluation of overall glucose metabolism without insight into the specific transport and metabolic steps. Here we demonstrate the ability of total-body multiparametric F-FDG PET to quantitatively evaluate glucose metabolism using macroparametric quantification and assess specific glucose delivery and phosphorylation processes using microparametric quantification for studying recovery from coronavirus disease 2019 (COVID-19). The study included 13 healthy subjects and 12 recovering COVID-19 subjects within 8 wk of confirmed diagnosis.

Fully Automated, Fast Motion Correction of Dynamic Whole-Body and Total-Body PET/CT Imaging Studies.

We introduce the Fast Algorithm for Motion Correction (FALCON) software, which allows correction of both rigid and nonlinear motion artifacts in dynamic whole-body (WB) images, irrespective of the PET/CT system or the tracer. Motion was corrected using affine alignment followed by a diffeomorphic approach to account for nonrigid deformations. In both steps, images were registered using multiscale image alignment.