Phantom-based investigation of block sequential regularised expectation maximisation (BSREM) reconstruction for zirconium-89 PET-CT for varied count levels.

Background: Zirconium-89 (Zr-89) PET tracers have become increasingly significant in the field of nuclear medicine due to their 3-day physical half-life, allowing for the study of dynamic biological processes over relatively long timeframes. To date there has been limited publication of studies focused on optimisation of acquisition parameters for Zr-89 PET. This paper outlines a short phantom study investigating the optimal beta regularization parameter for quantitation and noise in block sequential regularised expectation maximisation (BSREM) also known as Bayesian penalized likelihood (BPL) reconstruction, for varying image noise characteristics (acquisition duration).

Sequential deep learning image enhancement models improve diagnostic confidence, lesion detectability, and image reconstruction time in PET.

Background: Investigate the potential benefits of sequential deployment of two deep learning (DL) algorithms namely DL-Enhancement (DLE) and DL-based time-of-flight (ToF) (DLT). DLE aims to enhance the rapidly reconstructed ordered-subset-expectation-maximisation algorithm (OSEM) images towards block-sequential-regularised-expectation-maximisation (BSREM) images, whereas DLT aims to improve the quality of BSREM images reconstructed without ToF. As the algorithms differ in their purpose, sequential application may allow benefits from each to be combined.

Deep learning-based time-of-flight (ToF) image enhancement of non-ToF PET scans.

Purpose: To improve the quantitative accuracy and diagnostic confidence of PET images reconstructed without time-of-flight (ToF) using deep learning models trained for ToF image enhancement (DL-ToF).

Methods: A total of 273 [F]-FDG PET scans were used, including data from 6 centres equipped with GE Discovery MI ToF scanners. PET data were reconstructed using the block-sequential-regularised-expectation-maximisation (BSREM) algorithm with and without ToF.

Effects of Respiratory Motion on Y-90 PET Dosimetry for SIRT.

Respiratory motion degrades the quantification accuracy of PET imaging by blurring the radioactivity distribution. In the case of post-SIRT PET-CT verification imaging, respiratory motion can lead to inaccuracies in dosimetric measures. Using an anthropomorphic phantom filled with Y at a range of clinically relevant activities, together with a respiratory motion platform performing realistic motions (10-15 mm amplitude), we assessed the impact of respiratory motion on PET-derived post-SIRT dosimetry.

Advances in PET/CT Technology: An Update.

This article reviews the current evolution and future directions in PET/CT technology focusing on three areas: time of flight, image reconstruction, and data-driven gating. Image reconstruction is considered with advances in point spread function modelling, Bayesian penalised likelihood reconstruction, and artificial intelligence approaches. Data-driven gating is examined with reference to respiratory motion, cardiac motion, and head motion.

Image enhancement of whole-body oncology [F]-FDG PET scans using deep neural networks to reduce noise.

Purpose: To enhance the image quality of oncology [F]-FDG PET scans acquired in shorter times and reconstructed by faster algorithms using deep neural networks.

Methods: List-mode data from 277 [F]-FDG PET/CT scans, from six centres using GE Discovery PET/CT scanners, were split into ¾-, ½- and ¼-duration scans. Full-duration datasets were reconstructed using the convergent block sequential regularised expectation maximisation (BSREM) algorithm.

Data-Driven Respiratory Gating Outperforms Device-Based Gating for Clinical F-FDG PET/CT.

A data-driven method for respiratory gating in PET has recently been commercially developed. We sought to compare the performance of the algorithm with an external, device-based system for oncologic F-FDG PET/CT imaging. In total, 144 whole-body F-FDG PET/CT examinations were acquired, with a respiratory gating waveform recorded by an external, device-based respiratory gating system.

An interbacterial toxin inhibits target cell growth by synthesizing (p)ppApp.

Bacteria have evolved sophisticated mechanisms to inhibit the growth of competitors. One such mechanism involves type VI secretion systems, which bacteria can use to inject antibacterial toxins directly into neighbouring cells. Many of these toxins target the integrity of the cell envelope, but the full range of growth inhibitory mechanisms remains unknown.

Evaluation of data-driven respiratory gating waveforms for clinical PET imaging.

Background: We aimed to evaluate the clinical robustness of a commercially developed data-driven respiratory gating algorithm based on principal component analysis, for use in routine PET imaging.

Methods: One hundred fifty-seven adult FDG PET examinations comprising a total of 1149 acquired bed positions were used for the assessment. These data are representative of FDG scans currently performed at our institution.

Single Inflammatory Trigger Leads to Neuroinflammation in LRRK2 Rodent Model without Degeneration of Dopaminergic Neurons.

Background: Leucine-rich repeat kinase 2 (LRRK2) mutations are the most common genetic risk factor for Parkinson's disease (PD). While the corresponding pathogenic mechanisms remain largely unknown, LRRK2 has been implicated in the immune system.

Objective: To assess whether LRRK2 mutations alter the sensitivity to a single peripheral inflammatory trigger, with ultimate impact on dopaminergic integrity, using a longitudinal imaging-based study design.

Evaluation of principal component analysis-based data-driven respiratory gating for positron emission tomography.

Objective: Respiratory motion can degrade PET image quality and lead to inaccurate quantification of lesion uptake. Such motion can be mitigated via respiratory gating. Our objective was to evaluate a data-driven gating (DDG) technique that is being developed commercially for clinical PET/CT.

Phantom and clinical evaluation of the effect of full Monte Carlo collimator modelling in post-SIRT yttrium-90 Bremsstrahlung SPECT imaging.

Background: Post-therapy SPECT/CT imaging of Y microspheres delivered to hepatic malignancies is difficult, owing to the continuous, high-energy Bremsstrahlung spectrum emitted by Y. This study aimed to evaluate the utility of a commercially available software package (HybridRecon, Hermes Medical Solutions AB) which incorporates full Monte Carlo collimator modelling. Analysis of image quality was performed on both phantom and clinical images in order to ultimately provide a recommendation of an optimum reconstruction for post-therapy Y microsphere SPECT/CT imaging.

[11C]PBR28 PET imaging is sensitive to neuroinflammation in the aged rat.

Neuroinflammation in the aging rat brain was investigated using [(11)C]PBR28 microPET (positron emission tomography) imaging. Normal rats were studied alongside LRRK2 p.G2019S transgenic rats; this mutation increases the risk of Parkinson's disease in humans.

The discovery of I-BET726 (GSK1324726A), a potent tetrahydroquinoline ApoA1 up-regulator and selective BET bromodomain inhibitor.

Through their function as epigenetic readers of the histone code, the BET family of bromodomain-containing proteins regulate expression of multiple genes of therapeutic relevance, including those involved in tumor cell growth and inflammation. BET bromodomain inhibitors have profound antiproliferative and anti-inflammatory effects which translate into efficacy in oncology and inflammation models, and the first compounds have now progressed into clinical trials. The exciting biology of the BETs has led to great interest in the discovery of novel inhibitor classes.

Commentary: an eye on PET quantification.

Positron emission tomography (PET) is generally considered to be a quantitative imaging modality, allowing assessment of regional differences in radiotracer accumulation and the derivation of quantitative physiological information. Due to the increasing complexity of PET technology, the quantitative accuracy of PET images has to be continually reassessed if PET is to maintain its quantitative reputation. In this commentary, we discuss the results from a recent inter-scanner study in which the quantitative outcome measures from human studies were compared for three different radiotracers.

Behavioral deficits and striatal DA signaling in LRRK2 p.G2019S transgenic rats: a multimodal investigation including PET neuroimaging.

Background: A major risk-factor for developing Parkinson's disease (PD) is genetic variability in leucine-rich repeat kinase 2 (LRRK2), most notably the p.G2019S mutation. Examination of the effects of this mutation is necessary to determine the etiology of PD and to guide therapeutic development.

Performance assessment of a preclinical PET scanner with pinhole collimation by comparison to a coincidence-based small-animal PET scanner.

Unlabelled: PET imaging of rodents is increasingly used in preclinical research, but its utility is limited by spatial resolution and signal-to-noise ratio of the images. A recently developed preclinical PET system uses a clustered-pinhole collimator, enabling high-resolution, simultaneous imaging of PET and SPECT tracers. Pinhole collimation strongly departs from traditional electronic collimation achieved via coincidence detection in PET.

Measuring dopaminergic function in the 6-OHDA-lesioned rat: a comparison of PET and microdialysis.

Background: [18 F]fluorodopa (FDOPA) positron emission tomography (PET) allows assessment of levodopa (LDOPA) metabolism and is widely used to study Parkinson's disease. We examined how [18 F]FDOPA PET-derived kinetic parameters relate the dopamine (DA) and DA metabolite content of extracellular fluid measured by microdialysis to aid in the interpretation of data from both techniques.

Methods: [18 F]FDOPA PET imaging and microdialysis measurements were performed in unilaterally 6-hydroxydopamine-lesioned rats (n = 8) and normal control rats (n = 3).

In-vivo measurement of LDOPA uptake, dopamine reserve and turnover in the rat brain using [18F]FDOPA PET.

Longitudinal measurements of dopamine (DA) uptake and turnover in transgenic rodents may be critical when developing disease-modifying therapies for Parkinson's disease (PD). We demonstrate methodology for such measurements using [(18)F]fluoro-3,4-dihydroxyphenyl-L-alanine ([(18)F]FDOPA) positron emission tomography (PET). The method was applied to 6-hydroxydopamine lesioned rats, providing the first PET-derived estimates of DA turnover for this species.

Optimization of the injected activity in dynamic 3D PET: a generalized approach using patient-specific NECs as demonstrated by a series of 15O-H2O scans.

Unlabelled: The magnitude of the injected activity (A(0)) has a direct impact on the statistical quality of PET images. This study aimed to develop a generalized method for maximizing the statistical quality of dynamic PET images by optimizing A(0).

Methods: Patient-specific noise-equivalent counts (PS-NECs) were used as a metric of the statistical quality of each time frame of a dynamic PET image.