Current PET Research Articles

The Influence of Pet Owners’ Empathy on Perceptions of Dog and Cat Distress Vocalizations and Caregiving Behaviors

ABSTRACT Although vocal communication between humans and domestic animals is common, there has been limited research on how humans perceive the emotional content of animal vocalizations. This study investigated the relationship between pet ownership and sensitivity to negative emotion in dog and cat distress vocalizations (n = 237; 57% pet owners). Empathy toward animals and empathy toward humans were explored as possible mediators. The links between pet owners’ levels of sensitivity to animal distress vocalizations, empathy toward animals, and pet attachment and the care they provided to their pets were also examined. The findings revealed that current pet owners perceived both dog and cat distress vocalizations to be sadder than current non-pet owners. The link between pet ownership and sensitivity to dog (but not cat) distress vocalizations was fully mediated by empathy toward animals, but not mediated by empathy toward humans. Sensitivity to negative emotion in distress vocalizations was not a strong indicator of the level of care provided to dogs and cats. On the other hand, higher levels of empathy toward animals and pet attachment might be better indicators of humans providing more stimulating and enriched lives for their pets.

Evaluation of Characteristics Associated with Self-Identified Cat or Dog Preference in Pet Owners and Correlation of Preference with Pet Interactions and Care: An Exploratory Study.

Dog and cat preference has been associated with a few factors, like owner personality traits, but data regarding other aspects of preference ontogeny and the impact of preferences on pet wellbeing have yet to be examined. In this exploratory study, several of these characteristics, such as exposure to pets when young and as adults and current pet interactions and diet were analyzed from internet survey data. We found that more people identified as dog people (63.3%) versus cat people (36.7%) and preference for dogs remained consistent from childhood to adulthood compared with cats. In individuals who changed species preference, a lack of childhood exposure to cats (47.2%) was significantly associated with the group that changed preferences from dogs to cats from childhood to adulthood, compared with dog ownership as a child in the group that changed preferences from cats to dogs (24.4%). The number of cats and dogs in the home directly correlated with species preference (p < 0.001). Dwelling location was also significantly associated with species preference, with cat people being more likely to live in an urban area and dog people in a rural area (p = 0.002). More time was spent in both active and passive interactions with pets of the preferred species. Cats owned by cat people were more likely to be fed prescription diets compared with cats owned by dog people (p < 0.001). Interestingly, dog people were more likely to feed both their cats (p = 0.012) and dogs (p < 0.001) a raw diet compared with cat people. Additional research is needed to understand the development and impact of owner species preferences on pets to identify risks of suboptimal wellbeing.

Evaluation of Clinical Variables Affecting Myocardial Glucose Uptake in Cardiac FDG PET.

Cardiac 2-deoxy-2-[F-18]fluoro-D-glucose positron emission tomography (FDG PET) is widely used to assess myocardial viability in patients with ischemic heart disease. While sufficient glucose uptake is a prerequisite for accurate interpretation of cardiac viability, there are a lack of data on which clinical variables have the most significant impact on myocardial glucose metabolism. Therefore, this study was designed to evaluate several clinical variables that could affect myocardial glucose metabolism. A total of 214 consecutive cases were retrospectively enrolled in this study. All subjects received 250 mg of acipimox and underwent glucose loading as preparation for cardiac FDG PET/CT. Three-dimensional regions of interest (ROIs) were drawn on PET/CT fusion images. Myocardial glucose uptake ratio (MGUR = SUVmax of LV myocardium/SUVmean of liver) was then calculated. Multiple clinical variables including body mass index (BMI), blood glucose levels at different times, administered insulin dosage, lipid profiles, and ejection fraction were measured and analyzed for correlation with myocardial glucose uptake. After dichotomizing the subjects based on a BMI of 25, each group's MGUR was compared. Myocardial uptake showed significant correlations with BMI (r = -0.162, p = 0.018), HbA1c (r = -0.150, p = 0.030), and triglyceride levels (r = -0.137, p = 0.046). No other clinical variables showed a significant correlation with myocardial glucose uptake. After multiple linear regression analysis, BMI (p = 0.032) and HbA1c (p = 0.050) showed a correlation with MGUR. In group analysis, after dividing patients based on BMI, the obese group showed significantly lower myocardial uptake than the non-obese group (3.8 ± 1.9 vs. 4.4 ± 2.1, p = 0.031). Among several clinical variables, BMI and HbA1c levels were related to myocardial glucose uptake. A prospective study would be needed to examine whether a protocol that additionally considers BMI and HbA1c levels is necessary for the current cardiac FDG PET protocol.

'My pet can't come with me': Pets as a barrier against moving into supported accommodation.

To determine the impact of pet ownership on older people's decision to move to supported accommodation. Online survey. Older Australians who were current or past pet owners were invited to complete an online survey, with 193 participants providing valid data. Almost two-thirds of the respondents who said they did not intend to move in the foreseeable future (n = 85) said their pet was an important reason. When asked to rate which factors would be hardest to come to terms with if they had to move because they needed more assistance in future, three groups emerged: the first group (37%) thought the impact on their pet of moving would not be difficult and the pet was not an important reason for staying in their current home. The second group (36%) were the opposite; they believed there would be a negative impact on their pet if they moved and the pet was an important reason for them to stay. The final group (27%) thought their pet was not an important reason to stay in their current location but if they did have to move, the impact on the pet would be quite difficult. No one fell into the category of identifying that their pet was an important reason to stay but having to move would have no impact on the animal. Many older people think about their pets when making a decision to move house, including considering whether a move to supported accommodation will be difficult for their pet. A perceived absence of pet-friendly supported accommodation may be contributing to sub-optimal decision-making by older people.

반려동물 사료 표시제도의 법률적 쟁점과 과제

Driven by the increasing number of pets and households that have pets, the pet food market is undergoing substantial growth. With the surge in pet guardianship, pet food consumption has increased, which has been accompanied by a growing interest in various functional pet food types. Despite the variety available, a notable issue exists concerning the primary labeling of pet food. This study investigates the current status and major issues within the pet food labeling system and proposes improvements.&#x0D; The labeling system for pet food is governed by the Control of Livestock and Fish Feed Act in conjunction with livestock feed regulations. This dual oversight presents challenges in providing precise information to pet food consumers through the labeling system. Currently, there are no established standards for differentiating pet food product names, specifying recommended feeding amounts, highlighting nutritional functions, or verifying pet food labeling. Additionally, a robust review system and review board dedicated to overseeing pet food labeling are absent.&#x0D; To foster the growth of the pet food industry, a revision of the current pet food labeling system is imperative. The proposed revision involves the following: First, reorganizing the classification system. The existing feed classification system of formulated feed and straight feed (mixed straight feed) should transition to a labeling classification system based on the intended purpose of the feed. Second, there is a need to regulate the contents of pet food, including product names and nutritional ingredients. Mandatory display of product names and the regulation of their use are essential components of this revision. Third, empirical standards and the establishment of a review advisory board to authenticate pet food labeling are needed. Regulations on the contents and procedures for labeling and advertising on efficacy and effectiveness should be established, grounded in a minimum scientific evidence threshold. Furthermore, there have been calls for the formation of an advisory or review committee composed of experts, which underscores the need for the establishment of a system to facilitate this.

Multi-organ comparison and quantification parameters of [18F]THK-5317 uptake in preclinical mouse models of tau pathology

Introduction: Current small-animal PET instrumentation provides sufficient resolution, sensitivity, and quantitative accurate information on the radiotracer distribution within the whole body. However, most preclinical imaging studies focus on the disease-related organ of interest and do not use the total body information provided by small-animal PET. In this study, we investigated the distribution of [18F]THK-5317 (also referred to as (S)-[18F]THK-5117), a radiotracer initially developed to visualize tau deposits in the brain, in two transgenic mouse models of tau overexpression and littermate controls at different ages and of both sexes. We compared multiple quantitative parameters of radiotracer uptake in multiple organs of mice to investigate sex, age, or strain-related differences.Methods: After intravenous administration, 60-min dynamic PET scans were acquired, followed by venous blood sampling, organ harvesting, and metabolite analysis by radio-thin-layer chromatography.Results: Blood pharmacokinetics and metabolism of [18F]THK-5317 significantly differed between males and females across all strains. Sex-related differences in organ VTs were identified from two-way ANOVA analysis. Organ-to-blood concentration ratios correlated well with organ VTs in all investigated organs.Conclusion: Following our workflow, a straightforward multiple-organ analysis of [18F]THK-5317 uptake in mice was easily achievable. From the derived quantitative parameters, the organ-to-blood values correlate best with the calculated VTs. Given the active incorporation of 3R principles into preclinical quantitative imaging, we propose that this workflow might be suitable to select novel radiotracer candidates before more complex kinetic models, comprising invasive methods such as full arterial blood sampling, for radiotracer quantification are applied.

Factors Associated with Children’s Humane Attitudes toward Animals

Abstract Various studies have suggested a range of different factors associated with children’s attitudes toward animals; however, in Chile, it is an area that has not been studied. The current study administered the Intermediate Attitude Scale (IAS, which measures attitudes toward the humane treatment of animals) to 286 children in third and fourth grade and analyzed its association with the following variables: type of school, grade, gender, current pet ownership, the recognition accuracy of dog facial expressions, and human-directed empathy. The association between the IAS and potential factors was measured through linear mixed models. Children with higher human-directed empathy scores, fourth-grade children, and children who were more accurate in recognizing the happiness emotion on the dog’s face were associated with more positive attitudes toward the humane treatment of animals. These findings contribute to the growing literature regarding the importance of positive attitudes toward animals and their connection to human-directed empathy.

List-mode quantitative joint reconstruction of activity and attenuation maps in Time-of-Flight PET

Quantitative PET imaging requires accurate determination of patient-specific attenuation maps, which remains challenging on hybrid PET/MRI systems owing to the lack of a direct relationship between MR image intensity and attenuation coefficients. The aim of the present study is to develop a list-mode based algorithm for accurate and robust attenuation correction of PET data using time-of-flight (TOF) emission information. We analyze and address the challenges of list-mode emission-based maximum-likelihood joint estimation of activity and attenuation (LM-MLAA) in state-of-the-art PET imaging. The proposed method exploits a rapid on-the-fly system matrix calculation algorithm based on elliptic integrals while updating the attenuation map from accumulating list-mode coincidences to achieve accelerated image reconstruction. The scattering compensation is incorporated inside it using an iterative approach in such that the current estimation of attenuation map used on a course grid sampling scattering points to make an estimate of scattering. The performance of the proposed LM-MLAA approach was evaluated on Monte Carlo simulations of a phantom at different time resolutions. The contrast and noise for hot and cold regions on reconstructed images at different time resolutions were analysed. The estimated attenuation map exhibits resilience against noise, effectively eliminates high-frequency cross-talk even in the absence of prior information on attenuation coefficients, and enables discrimination among different anatomical regions in the reconstructed image. The error in the mean estimated attenuation coefficients after 50 iterations was ∼ 2% in water and ∼ -14% in Teflon regions for TOF resolutions corresponding to those of most current commercial PET systems (∼ 500 ps). The proposed LM-MLAA framework can be used for joint reconstruction of activity and attenuation maps from list-mode emission data as standalone or a complementary approach to existing in multimodality imaging such as PET/MRI, where direct measurement attenuation maps is not possible.

Walk-through flat panel total-body PET: a patient-centered design for high throughput imaging at lower cost using DOI-capable high-resolution monolithic detectors

PurposeLong axial field-of-view (LAFOV) systems have a much higher sensitivity than standard axial field-of-view (SAFOV) PET systems for imaging the torso or full body, which allows faster and/or lower dose imaging. Despite its very high sensitivity, current total-body PET (TB-PET) throughput is limited by patient handling (positioning on the bed) and often a shortage of available personnel. This factor, combined with high system costs, makes it hard to justify the implementation of these systems for many academic and nearly all routine nuclear medicine departments. We, therefore, propose a novel, cost-effective, dual flat panel TB-PET system for patients in upright standing positions to avoid the time-consuming positioning on a PET-CT table; the walk-through (WT) TB-PET. We describe a patient-centered, flat panel PET design that offers very efficient patient throughput and uses monolithic detectors (with BGO or LYSO) with depth-of-interaction (DOI) capabilities and high intrinsic spatial resolution. We compare system sensitivity, component costs, and patient throughput of the proposed WT-TB-PET to a SAFOV (= 26 cm) and a LAFOV (= 106 cm) LSO PET systems.MethodsPatient width, height (= top head to start of thighs) and depth (= distance from the bed to front of patient) were derived from 40 randomly selected PET-CT scans to define the design dimensions of the WT-TB-PET. We compare this new PET system to the commercially available Siemens Biograph Vision 600 (SAFOV) and Siemens Quadra (LAFOV) PET-CT in terms of component costs, system sensitivity, and patient throughput. System cost comparison was based on estimating the cost of the two main components in the PET system (Silicon Photomultipliers (SiPMs) and scintillators). Sensitivity values were determined using Gate Monte Carlo simulations. Patient throughput times (including CT and scout scan, patient positioning on bed and transfer) were recorded for 1 day on a Siemens Vision 600 PET. These timing values were then used to estimate the expected patient throughput (assuming an equal patient radiotracer injected activity to patients and considering differences in system sensitivity and time-of-flight information) for WT-TB-PET, SAFOV and LAFOV PET.ResultsThe WT-TB-PET is composed of two flat panels; each is 70 cm wide and 106 cm high, with a 50-cm gap between both panels. These design dimensions were justified by the patient sizes measured from the 40 random PET-CT scans. Each panel consists of 14 × 20 monolithic BGO detector blocks that are 50 × 50 × 16 mm in size and are coupled to a readout with 6 × 6 mm SiPMs arrays. For the WT-TB-PET, the detector surface is reduced by a factor of 1.9 and the scintillator volume by a factor of 2.2 compared to LAFOV PET systems, while demonstrating comparable sensitivity and much better uniform spatial resolution (< 2 mm in all directions over the FOV). The estimated component cost for the WT-TB-PET is 3.3 × lower than that of a 106 cm LAFOV system and only 20% higher than the PET component costs of a SAFOV. The estimated maximum number of patients scanned on a standard 8-h working day increases from 28 (for SAFOV) to 53–60 (for LAFOV in limited/full acceptance) to 87 (for the WT-TB-PET). By scanning faster (more patients), the amount of ordered activity per patient can be reduced drastically: the WT-TB-PET requires 66% less ordered activity per patient than a SAFOV.ConclusionsWe propose a monolithic BGO or LYSO-based WT-TB-PET system with DOI measurements that departs from the classical patient positioning on a table and allows patients to stand upright between two flat panels. The WT-TB-PET system provides a solution to achieve a much lower cost TB-PET approaching the cost of a SAFOV system. High patient throughput is increased by fast patient positioning between two vertical flat panel detectors of high sensitivity. High spatial resolution (< 2 mm) uniform over the FOV is obtained by using DOI-capable monolithic scintillators.

Monte Carlo simulation of the system performance of a long axial field-of-view PET based on monolithic LYSO detectors

BackgroundIn light of the milestones achieved in PET design so far, further sensitivity improvements aim to optimise factors such as the dose, throughput, and detection of small lesions. While several longer axial field-of-view (aFOV) PET systems based on pixelated detectors have been installed, continuous monolithic scintillation detectors recently gained increased attention due to their depth of interaction capability and superior intrinsic resolution. As a result, the aim of this work is to present and evaluate the performance of two long aFOV, monolithic LYSO-based PET scanner designs.MethodsGeant4 Application for Tomographic Emission (GATE) v9.1 was used to perform the simulations. Scanner designs A and B have an aFOV of 36.2 cm (7 rings) and 72.6 cm (14 rings), respectively, with 40 detector modules per ring each and a bore diameter of 70 cm. Each module is a 50 × 50 × 16 mm3 monolithic LYSO crystal. Sensitivity, noise equivalent count rate (NECR), scatter fraction, spatial resolution, and image quality tests were performed based on NEMA NU-2018 standards.ResultsThe sensitivity of design A was calculated to be 29.2 kcps/MBq at the centre and 27 kcps/MBq at 10 cm radial offset; similarly, the sensitivity of design B was found to be 106.8 kcps/MBq and 98.3 kcps/MBq at 10 cm radial offset. NECR peaks were reached at activity concentrations beyond the range of activities used for clinical studies. In terms of spatial resolution, the values for the point sources were below 2 mm for the radial, tangential, and axial full width half maximum. The contrast recovery coefficient ranged from 53% for design B and 4:1 contrast ratio to 90% for design A and 8:1 ratio, with a reasonably low background variability.ConclusionsLonger aFOV PET designs using monolithic LYSO have superior spatial resolution compared to current pixelated total-body PET (TB-PET) scanners. These systems combine high sensitivity with improved contrast recovery.

Guinea pig nutrition: what do we know?

Background: The nutritional requirements of pet guinea pigs are not particularly well understood, with much of the current information based on laboratory animal work and conditions which may not be directly transferable to pets. As such, both owners and veterinarians alike have limited resources available, potentially resulting in adverse effects on welfare caused by incorrect diets.Aim of the article: This article reviews what is currently known about pet guinea pig nutritional requirements. Wild guinea pig diets are discussed and current pet guinea pig owner feeding habits outlined. The article also looks at the potential adverse effects of an incorrect diet on guinea pigs and their welfare; some of this information is currently unknown, so it is discussed whether extrapolations are possible from other species. This article is a useful overview for all veterinary staff treating pet guinea pigs and giving dietary advice to owners in veterinary practice.

Concomitant Campylobacteriosis in a Puppy and in Its Caregiver: A One Health Perspective Paradigm in Human-Pet Relationship

We report a case of laboratory-confirmed Campylobacter (C). jejuni and C. upsaliensis symptomatic infection in a puppy, a French Bouledogue, female, 6 months of age, fed a raw, unbalanced, poultry-based diet (RPD), (48.1 CP, 33% EE, 0.3% Ca, 0.5% Phos, 0.5 Ca/P, on a dry-matter basis), and in its owner. Soon after adoption, the pet and the caregiver showed severe gastrointestinal signs and needed hospitalization. Fecal PCR assays, selective cultures, and antibiotic susceptibility testing were performed, and multi-drug resistant C. jejuni and C. upsaliensis were isolated from the feces of both. The same bacteria were also identified by FISH in the dog colonic biopsies collected during endoscopy. The puppy was prescribed a complete commercial diet for growing dogs, (30.00% CP, 21.00% EE, 1.2% Ca; 1% Phos; as fed) and treated with ciprofloxacin. The dog and the man healed uneventfully and tested negative for further fecal PCR analyses. This report focuses on dog nutritional management and explores the potential routes of exposure, with emphasis on emerging outbreaks related to current pet food fads. Our data support the One Health approach, where veterinarians, physicians, and owners are challenged to build effective stewardship to prevent the spread of zoonoses.

PET Imaging of Neuro-Inflammation with Tracers Targeting the Translocator Protein (TSPO), a Systematic Review: From Bench to Bedside

Parkinson's disease is the second most common neurodegenerative disorder, affecting 2-3% of the population of patients >65 years. Although the standard diagnosis of PD is clinical, neuroimaging plays a key role in the evaluation of patients who present symptoms related to neurodegenerative disorders. MRI, DAT-SPECT, and PET with [18F]-FDG are routinely used in the diagnosis and focus on the investigation of morphological changes, nigrostriatal degeneration or shifts in glucose metabolism in patients with parkinsonian syndromes. The aim of this study is to review the current PET radiotracers targeting TSPO, a transmembrane protein that is overexpressed by microglia in another pathophysiological process associated with neurodegenerative disorders known as neuroinflammation. To the best of our knowledge, neuroinflammation is present not only in PD but in many other neurodegenerative disorders, including AD, DLB, and MSA, as well as atypical parkinsonian syndromes. Therefore, in this study, specific patterns of microglial activation in PD and the differences in distribution volumes of these radiotracers in patients with PD as compared to other neurodegenerative disorders are reviewed.

Evaluation of PET Mainstream Scattering Correction Methods

Current mainstream PET scattering correction methods are introduced and evaluated horizontally, and finally, the existing problems and development direction of scattering correction are discussed. Based on NeuWise Pro PET/CT products of Neusoft Medical System Co. Ltd. , the simulation experiment is carried out to evaluate the influence of radionuclide distribution out of FOV (field of view) on the scattering estimation accuracy of each method. The scattering events produced by radionuclide out of FOV have an obvious impact on the spatial distribution of scattering, which should be considered in the model. The scattering estimation accuracy of Monte Carlo method is higher than single scatter simulation (SSS). Clinically, if the activity of the adjacent parts out of the FOV is high, such as brain, liver, kidney and bladder, it is likely to lead to the deviation of scattering estimation. Considering the Monte Carlo scattering estimation of the distribution of radionuclide out of FOV, it's helpful to improve the accuracy of scattering distribution estimation.

NiftyPAD - Novel Python Package for Quantitative Analysis of Dynamic PET Data

Current PET datasets are becoming larger, thereby increasing the demand for fast and reproducible processing pipelines. This paper presents a freely available, open source, Python-based software package called NiftyPAD, for versatile analyses of static, full or dual-time window dynamic brain PET data. The key novelties of NiftyPAD are the analyses of dual-time window scans with reference input processing, pharmacokinetic modelling with shortened PET acquisitions through the incorporation of arterial spin labelling (ASL)-derived relative perfusion measures, as well as optional PET data-based motion correction. Results obtained with NiftyPAD were compared with the well-established software packages PPET and QModeling for a range of kinetic models. Clinical data from eight subjects scanned with four different amyloid tracers were used to validate the computational performance. NiftyPAD achieved R^2>0.999 correlation with PPET, with absolute difference sim 10^{-2} for linearised Logan and MRTM2 methods, and R^2>0.999999 correlation with QModeling, with absolute difference sim 10^{-4} for basis function based SRTM and SRTM2 models. For the recently published SRTM ASL method, which is unavailable in existing software packages, high correlations with negligible bias were observed with the full scan SRTM in terms of non-displaceable binding potential (R^2=0.96), indicating reliable model implementation in NiftyPAD. Together, these findings illustrate that NiftyPAD is versatile, flexible, and produces comparable results with established software packages for quantification of dynamic PET data. It is freely available (https://github.com/AMYPAD/NiftyPAD), and allows for multi-platform usage. The modular setup makes adding new functionalities easy, and the package is lightweight with minimal dependencies, making it easy to use and integrate into existing processing pipelines.

Developing early vulnerable area aggregates for PET detection of beta‐amyloid based on young and middle‐aged adults from the Framingham Heart Study

AbstractBackgroundAs Alzheimer’s clinical trials shift earlier and earlier in the disease process, current global PET measures of beta‐amyloid (Aβ) positivity may be insufficient for detecting the earliest Aβ deposits. Regional PET measures may better detect the earliest deposits. Previous efforts to identify early‐accumulating regions have inferred which regions may be most vulnerable based on older adults. Our aim was to identify early vulnerable areas by looking earlier in the lifespan.Method235 clinically‐normal adults ages 33‐74 from the Framingham Heart Study (FHS) underwent one time‐point of dynamic Pittsburgh Compound B (PIB) PET (Tab.1). PIB was regionally quantified in Desikan regions using distribution volume ratio (DVR, cerebellar reference). Linear and quadratic (Age + Age2) models were run to determine association of age with region of interest (ROI) PIB DVR, and ROIs with significantly increasing DVRs were selected for the generation of candidate early vulnerable area (EVA) aggregates. Multiple aggregate EVA DVRs (EVA2‐EVA11) were generated by sequential addition of regions in rank order of descending Age2 estimate. EVA positivity was derived from both full‐sample GMM and &lt;45 sample mean+2SD thresholds. Finally, EVA aggregates were tested using an independent cohort of older adults from the Harvard Aging Brain Study (HABS) that were imaged under an identical protocol (n=250, ages 50‐92), computing sensitivity and specificity of each aggregate at baseline to predict progression to global PIB positivity 3 years later.ResultOf 35 Desikan regions each evaluated on the left and right, 11 emerged as quadratic age relationships (p&lt;0.05; Fig.1) and were used to generate EVA aggregates (Fig.2). Independent validation in baseline global PIB‐ individuals from HABS indicated EVA9 and EVA10 best predicted future accumulation (Fig.3). GMM‐based thresholds provided excellent specificity (SP=1.0) but weak sensitivity (SE=0.41) to predict progression to global PIB positivity 3 years later, while the more liberal mean+2SD thresholds improved sensitivity but decreased specificity (SE=0.88, SP=0.88).ConclusionUtilizing lifespan data from FHS, we identified a set of early vulnerable regions that are predictive of future accumulation in an independent sample of older adults. These findings are potentially useful in identifying the earliest deposits of Aβ for use in clinical trial design.

Alzheimer brains: increased soluble amyloid peptides, but decreased lipid rafts

AbstractBackgroundPET imaging studies of AD patients show progressive increases of fibrillar Aβ‐ amyloid. Because current PET ligands underestimate non‐fibrillar forms, we assayed soluble Aβ in AD and controls. To identify mechanisms responsible for soluble Aβ in AD brains, we examined lipid rafts (LR), where APP is enzymatically processed. Frontal cortex was compared with cerebellum, which has minimal AD pathology.MethodPostmortem samples (N=48) were age‐and sex matched for Braak scores. Soluble Aβ was extracted from homogenates of full thickness frontal cortex by isotonic buffer and mild detergent (RIPA; 1% NP40) and centrifuged (10,000g/1h). Supernates were assayed by dot blots with antibodies for Aβ40 and Aβ42 (Biolegend, San Diego, CA). Aβ was assayed as relative fluorescent units per gm brain. LR fractions were isolated from these same brains by kit (Invent Biotechnologies; LR‐039), validated by ultracentrifugal fractionation.ResultCompared with cognitively normal controls (Braak 0‐1), elevations of soluble Aβ40 and Aβ42 were similar for intermediate and later stage AD (Braak 2‐3 and 4‐6). Clinical grade AD had greater increase of soluble Aβ40 (+400%) than Aβ42 (+50%) (p&lt;0.05). LR raft yield per gram AD frontal cortex was 20% below controls (p&lt;0.05), while cerebellar LR did not differ by Braak score. The composition of LR had a similar pattern, with 35% AD decreases of total protein and cholesterol (p&lt;0.05); cerebellar LR again did not differ by Braak score. However, LR 4‐HNE, a marker of oxidative damage, was similarly increased in AD cortex and AD cerebellum.ConclusionThe extensive overlap of soluble Aβ levels in controls with AD contrasts with the PET findings on fibrillar Aβ. These findings further support fibrillar Aβ as a biomarker for AD treatments and show the need for more detailed postmortem analysis of diverse soluble and insoluble Aβ aggregates in relation to PET. The decreased LR in AD frontal cortex is consistent with its extensive neuronal loss, in contrast to the cerebellum. Further studies will examine LR enzymes of APP processing as a source of the increased soluble Aβ in AD, and subcellular clearance processes, which may be impaired in association with the oxidative damage indicated by increased 4‐HNE.

A semi-monolithic detector providing intrinsic DOI-encoding and sub-200ps CRT TOF-capabilities for clinical PET applications.

Current clinical positron emission tomography (PET) systems utilize detectors where the scintillator typically contains single elements of 3-6-mm width and about 20-mm height. While providing good time-of-flight performance, this design limits the spatial resolution and causes radial astigmatism as the depth-of-interaction (DOI) remains unknown. We propose an alternative, aiming to combine the advantages of current detectors with the DOI capabilities shown for monolithic concepts, based on semi-monolithic scintillators (slabs). Here, the optical photons spread along one dimension enabling DOI-encoding with a still small readout area beneficial for timing performance. An array of eight monolithic LYSO slabs of dimensions 3.9×32×19mm3 was read out by a 64-channel photosensor containing digital SiPMs (DPC3200-22-44, Philips Digital Photon Counting). The position estimation in the detector's monolithic and DOI direction was based on a calibration with a fan beam collimator and the machine learning technique gradient tree boosting (GTB). We achieved a positioning performance in terms of mean absolute error (MAE) of 1.44mm for the monolithic direction and 2.12mm for DOI considering a wide energy window of 300-700keV. The energy resolution was determined to be 11.3%, applying a positional-dependent energy calibration. We established both an analytical and machine-learning-based timing calibration approach and applied them for a first-photon trigger. The analytical timing calibration corrects for electronic and optical time skews leading to 240ps coincidence resolving time (CRT) for a pair of slab-detectors. The CRT was significantly improved by utilizing GTB to predict the time difference based on specific training data and applied on top of the analytical calibration. We achieved 209ps for the wide energy window and 198ps for a narrow selection around the photopeak (411-561keV). To maintain the detector's sensitivity, no filters were applied to the data during processing. Overall, the semi-monolithic detector provides attractive performance characteristics. Especially, a good CRT can be achieved while introducing DOI capabilities to the detector, making the concept suitable for clinical PET scanners.

Alzheimer's Disease Prediction Algorithm Based on Group Convolution and a Joint Loss Function.

Alzheimer's disease (AD) can effectively predict by 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) of the brain, but current PET images still suffer from indistinct lesion features, low signal-to-noise ratios, and severe artefacts, resulting in poor prediction accuracy for patients with mild cognitive impairment (MCI) and unclear lesion features. In this paper, an AD prediction algorithm based on group convolution and a joint loss function is proposed. First, a group convolutional backbone network based on ResNet18 is designed to extract lesion features from multiple channels, which makes the expression ability of the network improved to a great extent. Then, a hybrid attention mechanism is presented, which enables the network to focus on target regions and learn feature weights, so as to enhance the network's learning ability of the lesion regions that are relevant to disease diagnosis. Finally, a joint loss function, that avoids the overfitting phenomenon, increases the generalization of the model, and improves prediction accuracy by adding a regularization loss function to the conventional cross-entropy function, is proposed. Experiments conducted on the public Alzheimer's Disease Neuroimaging Initiative (ADNI) dataset show that the algorithm we proposed gives a prediction accuracy improvement of 2.4% over that of the current AD prediction algorithm, thus proving the effectiveness and availability of the new algorithm.

Breast PET/MRI Hybrid Imaging and Targeted Tracers.

The recent introduction of hybrid positron emission tomography/magnetic resonance imaging (PET/MRI) as a promising imaging modality for breast cancer assessment has prompted fervent research activity on its clinical applications. The current knowledge regarding the possible clinical applications of hybrid PET/MRI is constantly evolving, thanks to the development and clinical availability of hybrid scanners, the development of new PET tracers and the rise of artificial intelligence (AI) techniques. In this state-of-the-art review on the use of hybrid breast PET/MRI, the most promising advanced MRI techniques (diffusion-weighted imaging, dynamic contrast-enhanced MRI, magnetic resonance spectroscopy, and chemical exchange saturation transfer) are discussed. Current and experimental PET tracers (18 F-FDG, 18 F-NaF, choline, 18 F-FES, 18 F-FES, 89 Zr-trastuzumab, choline derivatives, 18 F-FLT, and 68 Ga-FAPI-46) are described in order to provide an overview on their molecular mechanisms of action and corresponding clinical applications. New perspectives represented by the use of radiomics and AI techniques are discussed. Furthermore, the current strengths and limitations of hybrid PET/MRI in the real world are highlighted. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 2.