PET evaluation of myocardial perfusion function after percutaneous coronary intervention in patients with chronic total occlusion: a systematic review and meta-analysis

Objective. The benefit of percutaneous coronary intervention (PCI) in chronic complete coronary artery occlusion (CTO) remains controversial. PCI is currently indicated only for symptom and myocardial ischemia abolition, but large chronically occluded vessels with extensive afferent myocardial territories may benefit most from this procedure. The noninvasive evaluation of myocardial perfusion is critical before and after revascularization, and positron emission tomography (PET) can determine absolute myocardial perfusion. Here, we aimed to explore and compare myocardial perfusion in CTO territories and their remote associated areas before and after PCI. Design. We searched for relevant articles published before November 28, 2022, in the Cochrane Library and PubMed. We calculated 95% confidence intervals (CIs) and standardized mean differences (SMDs) for parameters related to myocardial perfusion in CTO territories and remote areas in CTO patients before and after PCI. Results. We included five studies published between 2017 and 2022, with a total of 592 patients. Stress myocardial blood flow (MBF) was increased in CTO territories after PCI when compared to pre-PCI (mean difference [MD]: 1.70, 95% confidence interval [CI] 1.33-2.08, p < 0.001). Coronary flow reserve (CFR) in CTO regions was also higher after PCI (MD 1.37,95% [CI]1.13-1.61, p < 0.001). Stress MBF in remote regions was also increased after PCI (MD 0.27,95% [CI]0.99 ∼ 0.45, p = 0.004), as was CFR in remote regions (MD 0.32,95% [CI] 0.14-0.5, p = 0.001). Conclusions. According to our pooled analysis of current literature, there was an increase in stress MBF and CFR in both CTOs and remote regions after PCI, suggesting that patients with CTO have widespread recovery of blood perfusion after the procedure. These results provide evidence that patients with CTO arteries and high ischemic burdens would indeed benefit from CTO-PCI. Future research on the correlation of ischemia burden reduction with hard clinical endpoints would contribute to a clearer demarcation of the role of CTO PCI with prognostic potential.

The effects of the β1-adrenergic receptor antagonist bisoprolol administration on mirabegron-stimulated human brown adipose tissue thermogenesis

AIM

Pharmacological stimulation of human brown adipose tissue (BAT) has been hindered by ineffective activation or undesirable off-target effects. Oral administration of the maximal allowable dose of mirabegron (200 mg), a β3-adrenergic receptor (β3-AR) agonist, has been effective in stimulating BAT thermogenesis and whole-body energy expenditure. However, this has been accompanied by undesirable cardiovascular effects. Therefore, we hypothesized that combining mirabegron with a β1-AR antagonist could suppress these unwanted effects and increase the stimulation of the β3-AR and β2-AR in BAT.

METHODS

We performed a randomized crossover trial (NCT04823442) in 8 lean men. Mirabegron (200 mg) was administered orally with or without the β1-AR antagonist bisoprolol (10 mg). Dynamic [11C]-acetate and 2-deoxy-2-[18F]fluoro-d-glucose PET/CT scans were performed sequentially after oral administration of mirabegron ± bisoprolol.

RESULTS

Compared to room temperature, mirabegron alone increased BAT oxidative metabolism (0.84 ± 0.46 vs. 1.79 ± 0.91 min-1, p = 0.0433), but not when combined with bisoprolol. The metabolic rate of glucose in BAT, measured using [18F]FDG PET, was significantly higher with mirabegron than mirabegron with bisoprolol (24 ± 10 vs. 16 ± 8 nmol/g/min, p = 0.0284). Bisoprolol inhibited the mirabegron-induced increase in systolic blood pressure and heart rate.

CONCLUSION

The administration of bisoprolol decreases the adverse cardiovascular effects of mirabegron. However, the provided dose also blunted the mirabegron-stimulated increase in BAT lipolysis, thermogenesis, and glucose uptake. The attenuation in BAT blood flow induced by the large dose of bisoprolol may have limited BAT thermogenesis.

Brown adipose tissue metabolism in women is dependent on ovarian status

In rodents, loss of estradiol (E2) reduces brown adipose tissue (BAT) metabolic activity. Whether E2 impacts BAT activity in women is not known. BAT oxidative metabolism was measured in premenopausal (n = 27; 35 ± 9 yr; body mass index = 26.0 ± 5.3 kg/m2) and postmenopausal (n = 25; 51 ± 8 yr; body mass index = 28.0 ± 5.0 kg/m2) women at room temperature and during acute cold exposure using [11C]acetate with positron emission tomography coupled with computed tomograph. BAT glucose uptake was also measured during acute cold exposure using 2-deoxy-2-[18F]fluoro-d-glucose. To isolate the effects of ovarian hormones from biological aging, measurements were repeated in a subset of premenopausal women (n = 8; 40 ± 4 yr; BMI = 28.0 ± 7.2 kg/m2) after 6 mo of gonadotropin-releasing hormone agonist therapy to suppress ovarian hormones. At room temperature, there was no difference in BAT oxidative metabolism between premenopausal (0.56 ± 0.31 min-1) and postmenopausal women (0.63 ± 0.28 min-1). During cold exposure, BAT oxidative metabolism (1.28 ± 0.85 vs. 0.91 ± 0.63 min-1, P = 0.03) and net BAT glucose uptake (84.4 ± 82.5 vs. 29.7 ± 31.4 nmol·g-1·min-1, P < 0.01) were higher in premenopausal than postmenopausal women. In premenopausal women who underwent gonadotropin-releasing hormone agonist, cold-stimulated BAT oxidative metabolism was reduced to a similar level (from 1.36 ± 0.66 min-1 to 0.91 ± 0.41 min-1) to that observed in postmenopausal women (0.91 ± 0.63 min-1). These results provide the first evidence in humans that reproductive hormones are associated with BAT oxidative metabolism and suggest that BAT may be a target to attenuate age-related reduction in energy expenditure and maintain metabolic health in postmenopausal women.NEW & NOTEWORTHY In rodents, loss of estrogen reduces brown adipose tissue (BAT) activity. Whether this is true in humans is not known. We found that BAT oxidative metabolism and glucose uptake were lower in postmenopausal compared to premenopausal women. In premenopausal women who underwent ovarian suppression to reduce circulating estrogen, BAT oxidative metabolism was reduced to postmenopausal levels. Thus the loss of ovarian function in women leads to a reduction in BAT metabolic activity independent of age.

Measurement of Cerebral Glucose Metabolism in the Visual Cortex Predicts the Prognosis of Hemianopia

BACKGROUND AND OBJECTIVE

Homonymous hemianopia caused by cerebrovascular disease may improve over time. This study investigated whether functional neuroimaging can predict the prognosis of hemianopia due to cerebral infarction.

METHODS

We studied 19 patients (10 men and 9 women) with homonymous hemianopia and compared them with 34 healthy subjects (20 men and 14 women). Cerebral glucose metabolism was measured by 18F-fluorodeoxyglucose positron emission tomography (FDG-PET), 1 to 6 months after the onset. Bilateral regions of interest (ROIs) were selected from the posterior and, anterior striate cortices, extrastriate cortex, and thalamus. Furthermore, semi-quantitative data on cerebral glucose metabolism were obtained for ROIs and compared with the data obtained for homologous regions in the contralateral hemisphere by calculating the ipsilateral/contralateral (I/C) ratio.

RESULTS

The I/C ratio for the cerebral glucose metabolism in the posterior striate cortex was high (>0.750) in 8 patients, and the central visual field of these patients improved or showed macular sparing. The I/C ratio for cerebral glucose metabolism in the anterior striate cortex was high (>0.830) in 7 patients, and the peripheral visual field of these patients improved. However, no improvement was observed in 9 patients with a low I/C ratio for cerebral glucose metabolism in both the posterior and anterior striate cortices.

CONCLUSION

Measurement of cerebral glucose metabolism in the striate cortex is useful for estimating visual field prognosis. Furthermore, FDG-PET is useful in predicting the prognosis of hemianopia.

Economic and healthcare resource utilization assessments of pet imaging in coronary artery disease diagnosis: a systematic review and discussion of opportunities for future economic evaluations

Aims: This systematic literature review (SLR) consolidated economic and healthcare resource utilization (HCRU) evidence for positron emission tomography (PET) and single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) to inform future economic evaluations.Materials and Methods: An electronic search was conducted in MEDLINE, Embase, and Cochrane databases from 2012-2022. Economic and HCRU studies in adults who underwent PET- or SPECT-MPI for coronary artery disease (CAD) diagnosis were eligible. A qualitative methodological assessment of existing economic evaluations, HCRU, and downstream cardiac outcomes was completed. Exploratory meta-analyses of clinical outcomes were performed.Results: The search yielded 13,439 results, with 71 records included. Economic evaluations and comparative clinical trials were limited in number and outcome types (HCRU, downstream cardiac outcomes, and diagnostic performance) assessed. No studies included all outcome types and only one economic evaluation linked diagnostic performance to HCRU. The meta-analyses of comparative studies demonstrated significantly higher rates of early- and late-invasive coronary angiography and revascularization for PET- compared to SPECT-MPI; however, the rate of repeat testing was lower with PET-MPI. The rate of acute myocardial infarction was lower, albeit non-significant with PET- vs. SPECT-MPI.Limitations and Conclusions: This SLR identified economic and HCRU evaluations following PET- and SPECT-MPI for CAD diagnosis and determined that existing studies do not capture all pertinent outcome parameters or link diagnostic performance to downstream HCRU and cardiac outcomes, thus, resulting in simplified assessments of CAD burden. A limitation of this work relates to heterogeneity in study designs, patient populations, and follow-up times of existing studies. Resultingly, it was challenging to pool data in meta-analyses. Overall, this work provides a foundation for the development of comprehensive economic models for PET- and SPECT-MPI in CAD diagnosis, which should link diagnostic outcomes to HCRU and downstream cardiac events to capture the full CAD scope.

Approach to the patient: Concept and application of targeted radiotherapy in the paraganglioma patient

Paragangliomas can metastasize, posing potential challenges in both symptomatic management and disease control. Systemic targeted radiotherapies using 131I-MIBG and 177Lu-DOTATATE are a mainstay in the treatment of metastatic paragangliomas. This clinical scenario and discussion aim to enhance physicians' knowledge of the stepwise approach to treat these patients with paraganglioma targeted radiotherapies. It comprehensively discusses current approaches to selecting paraganglioma patients for targeted radiotherapies and how to choose between the two radiotherapies based on specific patient and tumor characteristics, when either therapy is feasible, or one is superior to another one. The safety, efficacy, toxicity profiles, and optimization of these radiotherapies are also discussed, along with other therapeutic options including radiotherapies, available for patients besides these two therapies. As conclusion, perspectives in radiotherapies of paraganglioma patients are outlined since they hold near future promising approaches that can improve patient outcomes.

Tumor-Targeted Perfluorinated Micelles as Efficient Theranostic Agents Combining Positron Emission Tomography and Radiosensitization

We report the synthesis of biocompatible perfluorinated micelles designed to improve radiotherapeutic efficacy in a radioresistant tumor environment. In vitro and in vivo behaviors of perfluorinated micelles were assessed at both cellular and tissular levels. The micellar platform offers key advantages as theranostic tool: (i) small size, allowing deep tissue penetration; (ii) oxygen transport to hypoxic tissues; (iii) negligible toxicity in the absence of ionizing radiation; (iv) internalization into cancer cells; (v) potent radiosensitizing effect; and (vi) excellent tumor-targeting properties, as monitored by positron emission tomography. We have demonstrated strong in vitro radiosensitizing effects of the micelle and in vivo tumor targeting, making this nanometric carrier a promising tool for the potentiation of focused radiotherapy.

Development of Pyridothiophene Compounds for PET Imaging of α-Synuclein

Aggregated α-synuclein (α-syn) protein is a pathological hallmark of Parkinson's disease (PD) and Lewy body dementia (LBD). Development of positron emission tomography (PET) radiotracers to image α-syn aggregates has been a longstanding goal. This work explores the suitability of a pyridothiophene scaffold for α-syn PET radiotracers, where 47 derivatives of a potent pyridothiophene (asyn-44; Kd=1.85 nM) were synthesized and screened against [3H]asyn-44 in competitive binding assays using post-mortem PD brain homogenates. Equilibrium inhibition constant (Ki) values of the most potent compounds were determined, of which three had Ki's in the lower nanomolar range (12-15 nM). An autoradiography study confirmed that [3H]asyn-44 is promising for imaging brain sections from multiple system atrophy and PD donors. Fluorine-18 labelled asyn-44 was synthesized in 6±2 % radiochemical yield (decay-corrected, n=5) with a molar activity of 263±121 GBq/μmol. Preliminary PET imaging of [18F]asyn-44 in rats showed high initial brain uptake (>1.5 standardized uptake value (SUV)), moderate washout (~0.4 SUV at 60 min), and low variability. Radiometabolite analysis showed 60-80 % parent tracer in the brain after 30 and 60 mins. While [18F]asyn-44 displayed good in vitro properties and acceptable brain uptake, troublesome radiometabolites precluded further PET imaging studies. The synthesis and in vitro evaluation of additional pyridothiophene derivatives are underway, with the goal of attaining improved affinity and metabolic stability.

Customizable Porphyrin Platform Enables Folate Receptor PET Imaging Using Copper-64

Folate receptors including folate receptor α (FRα) are overexpressed in up to 90% of ovarian cancers. Ovarian cancers overexpressing FRα often exhibit high degrees of drug resistance and poor outcomes. A porphyrin chassis has been developed that is readily customizable according to the desired targeting properties. Thus, compound O5 includes a free base porphyrin, two water-solubilizing groups that project above and below the macrocycle plane, and a folate targeting moiety. Compound O5 was synthesized (>95% purity) and exhibited aqueous solubility of at least 0.48 mM (1 mg/mL). Radiolabeling of O5 with 64Cu in HEPES buffer at 37 °C gave a molar activity of 1000 μCi/μg (88 MBq/nmol). [64Cu]Cu-O5 was stable in human serum for 24 h. Cell uptake studies showed 535 ± 12% bound/mg [64Cu]Cu-O5 in FRα-positive IGROV1 cells when incubated at 0.04 nM. Subcellular fractionation showed that most radioactivity was associated with the cytoplasmic (39.4 ± 2.7%) and chromatin-bound nuclear (53.0 ± 4.2%) fractions. In mice bearing IGROV1 xenografts, PET imaging studies showed clear tumor uptake of [64Cu]Cu-O5 from 1 to 24 h post injection with a low degree of liver uptake. The tumor standardized uptake value at 24 h post injection was 0.34 ± 0.16 versus 0.06 ± 0.07 in the blocking group. In summary, [64Cu]Cu-O5 was synthesized at high molar activity, was stable in serum, exhibited high binding to FRα-overexpressing cells with high nuclear translocation, and gave uptake that was clearly visible in mouse tumor xenografts.

Influence of Body Mass Index on Radiation Exposure Across Imaging Modalities in the Evaluation of Chest Pain

BACKGROUND

Essential to a patient-centered approach to imaging individuals with chest pain is knowledge of differences in radiation effective dose across imaging modalities. Body mass index (BMI) is an important and underappreciated predictor of effective dose. This study evaluated the impact of BMI on estimated radiation exposure across imaging modalities.

METHODS AND RESULTS

This was a retrospective analysis of patients with concern for cardiac ischemia undergoing positron emission tomography (PET)/computed tomography (CT), cadmium zinc telluride single-photon emission CT (SPECT) myocardial perfusion imaging, or coronary CT angiography (CCTA) using state-of-the-art imaging modalities and optimal radiation-sparing protocols. Radiation exposure was calculated across BMI categories based on established cardiac imaging-specific conversion factors. Among 9046 patients (mean±SD age, 64.3±13.1 years; 55% men; mean±SD BMI, 30.6±6.9 kg/m2), 4787 were imaged with PET/CT, 3092 were imaged with SPECT/CT, and 1167 were imaged with CCTA. Median (interquartile range) radiation effective doses were 4.4 (3.9-4.9) mSv for PET/CT, 4.9 (4.0-6.3) mSv for SPECT/CT, and 6.9 (4.0-11.2) mSv for CCTA. Patients at a BMI <20 kg/m2 had similar radiation effective dose with all 3 imaging modalities, whereas those with BMI ≥20 kg/m2 had the lowest effective dose with PET/CT. Radiation effective dose and variability increased dramatically with CCTA as BMI increased, and was 10 times higher in patients with BMI >45 kg/m2 compared with <20 kg/m2 (median, 26.9 versus 2.6 mSv). After multivariable adjustment, PET/CT offered the lowest effective dose, followed by SPECT/CT, and then CCTA (P<0.001).

CONCLUSIONS

Although median radiation exposure is modest across state-of-the-art PET/CT, SPECT/CT, and CCTA systems using optimal radiation-sparing protocols, there are significant variations across modalities based on BMI. These data are important for making patient-centered decisions for ischemic testing.

Symmetric and Profound Monoaminergic Degeneration in Parkinson's Disease with Premotor REM Sleep Behavior Disorder

Background

Rapid eye movement sleep behavior disorder (RBD) may precede or follow motor symptoms in Parkinson's disease (PD). While over 70% of idiopathic RBD cases phenoconvert within a decade, a small subset develops PD after a more extended period or remains nonconverted. These heterogeneous manifestations of RBD in PD prompt subtype investigations. Premotor RBD may signify "body-first" PD with bottom-up, symmetric synucleinopathy propagation.

Objective

Explore brainstem and nigrostriatal monoaminergic degeneration pattern differences based on premotor RBD presence and duration in de novo PD patients.

Methods

In a cross-sectional analysis of de novo PD patients (n = 150) undergoing FP-CIT PET and RBD Single-Question Screen, the cohort was categorized into groups with and without premotor RBD (PDRBD +/-), with further classification of PDRBD + based on a 10-year duration of premotor RBD. Analysis of FP-CIT binding in the striatum and pons, striatal asymmetry, and striatum-to-pons ratios compared patterns of nigrostriatal and brainstem monoaminergic degeneration.

Results

PDRBD + exhibited more severe and symmetrical striatal dopaminergic denervation compared to PDRBD-, with the difference in severity accentuated in the least-affected hemisphere. The PDRBD +<10Y subgroup displayed the most prominent striatal symmetry, supporting a more homogeneous "body-first" subtype. Pontine uptakes remained lower in PDRBD + even after adjusting for striatal uptake, suggesting early degeneration of pontine monoaminergic nuclei.

Conclusions

Premotor RBD in PD is associated with severe, symmetrical nigrostriatal and brainstem monoaminergic degeneration, especially in cases with PD onset within 10 years of RBD. This supports the concept of a "widespread, bottom-up" pathophysiological mechanism associated with premotor RBD in PD.

Design, Synthesis, and Evaluation of [18F]BIBD-300 as a Positron Emission Tomography Tracer for Poly(ADP-Ribose) Polymerase-1

Compounds 8a-j were designed to adjust the mode of interaction and lipophilicity of FTT by scaffold hopping and changing the length of the alkoxy groups. Compounds 8a, 8d, 8g, and BIBD-300 were screened for high-affinity PARP-1 through enzyme inhibition assays and are worthy of further evaluation. PET imaging of MCF-7 subcutaneous tumors with moderate expression of PARP-1 showed that compared to [18F]FTT, [18F]8a, [18F]8d, and [18F]8g exhibited greater nonspecific uptake, a lower target-to-nontarget ratio, and severe defluorination, while [18F]BIBD-300 exhibited lower nonspecific uptake and a greater target-to-nontarget ratio. PET imaging of 22Rv1 subcutaneous tumors, which highly express PARP-1, confirmed that the uptake of [18F]BIBD-300 in normal organs, such as the liver, muscle, and bone, was lower than that of [18F]FTT, and the ratio of tumor-to-muscle and tumor-to-liver [18F]BIBD-300 was greater than that of [18F]FTT. The biodistribution results in mice with MCF-7 and 22Rv1 subcutaneous tumors further validated the results of PET imaging. Unlike [18F]FTT, which mainly relies on hepatobiliary clearance, [18F]BIBD-300, which has lower lipophilicity, undergoes a partial shift from hepatobiliary to renal clearance, providing the possibility for [18F]BIBD-300 to indicate liver cancer. The difference in the PET imaging results for [18F]FTT, [18F]BIBD-300, and [18F]8j in 22Rv1 mice and the corresponding molecular docking results further confirmed that subtle structural modifications in lipophilicity greatly optimize the properties of the tracer. Cell uptake experiments also demonstrated that [18F]BIBD-300 has a high affinity for PARP-1. Metabolized and unmetabolized [18F]FTT and [18F]BIBD-300 were detected in the brain, indicating that they could not accurately quantify the amount of PARP-1 in the brain. However, PET imaging of glioma showed that both [18F]FTT and [18F]BIBD-300 could accurately localize both in situ to C6 and U87MG tumors. Based on its potential advantages in the diagnosis of breast cancer, prostate cancer, and glioma, as well as liver cancer, [18F]BIBD-300 is a new option for an excellent PARP-1 tracer.

The Importance of PET Imaging to Understanding Whole-Body Cortisol Metabolism in Alzheimer's Disease

Excess cortisol is associated with more severe cognitive decline, Alzheimer's disease, and related dementia phenotypes. The intracellular enzyme 11β-HSD1 regenerates active cortisol from inactive cortisone. In this current issue, high regional brain occupancy of Xanamemtrademark, determined by [11C]TARACT PET imaging of 11β-HSD1, in cognitively normal individuals and mild cognitive impartment/Alzheimer's disease (AD) patients is presented. In the future, comprehensive kinetic modeling using arterial sampling for occupancy studies, and whole-body PET imaging of 11β-HSD1 enzyme levels, in combination with stable isotope studies of cortisol metabolism, can provide broad insight into enzyme levels and activity in AD and other relevant diseases.

In vivo MRI and PET imaging in a translational ILD mouse model expressing non-resolving fibrosis and bronchiectasis-like pathology after repeated systemic exposure to bleomycin

Drug-induced interstitial lung disease (ILD) is crucial to detect early to achieve the best treatment outcome. Optimally, non-invasive imaging biomarkers can be used for early detection of disease progression and treatment follow-up. Therefore, reliable in vivo models are warranted in new imaging biomarker development to accelerate better-targeted treatment options. Single-dose bleomycin models have, for a long time, served as a reference model in fibrosis and lung injury research. Here, we aimed to use a clinically more relevant animal model by systemic exposure to bleomycin and assessing disease progression over time by combined magnetic resonance imaging (MRI) and positron emission tomography (PET) imaging.

Methods

C57BL/6 mice received bleomycin (i.p. 35iU/kg) or saline as control twice per week for 4 weeks. Mice were monitored until 2 weeks after cessation of bleomycin administration (w4 + 1 and w4 + 2), referred to as the resting period. MRI scans were performed in weeks 3 and 4 and during the resting weeks. [18F]FDG-PET was performed at the last week of dosing (w4) and 2 weeks after the last dosing (w4 + 2). Lung tissue sections were stained with Masson's trichrome and evaluated by modified Ashcroft scoring. Lung volume and lesion volumes were assessed using MRI, as well as 3D mapping of the central airways.

Results and discussion

Bleomycin-challenged mice showed increased lung weights (p < 0.05), while total lung volume was unchanged (w4 and onward). Histology analysis demonstrated fibrotic lesions emanating from the distal parts of the lung. Fibrosis progression was visualized by MRI with significantly increased high signal in bleomycin-exposed lungs compared to controls (p < 0.05). In addition, a significant increase in central airway diameter (p < 0.01) was displayed in bleomycin-exposed animals compared to controls and further continued to dilate as the disease progressed, comparing the bleomycin groups over time (p < 0.05-0.001). Lung [18F]FDG uptake was significantly elevated in bleomycin-exposed mice compared to controls (p < 0.05).

Conclusion

Non-invasive imaging displayed progressing lesions in the lungs of bleomycin-exposed mice, using two distinct MRI sequences and [18F]FDG-PET. With observed fibrosis progression emanating from distal lung areas, dilation of the central airways was evident. Taken together, this chronic bleomycin-exposure model is translationally more relevant for studying lung injury in ILD and particularly in the context of DIILD.

Advances in the Development of Positron Emission Tomography Tracers for Improved Detection of Differentiated Thyroid Cancer

Thyroid cancer poses a significant challenge in clinical management, necessitating precise diagnostic tools and treatment strategies for optimal patient outcomes. This review explores the evolving field of radiotracers in the diagnosis and management of thyroid cancer, focusing on prostate-specific membrane antigen (PSMA)-based radiotracers, fibroblast activation protein inhibitor (FAPI)-based radiotracers, Arg-Gly-Asp (RGD)-based radiotracers, and 18F-tetrafluoroborate (18F-TFB). PSMA-based radiotracers, initially developed for prostate cancer imaging, have shown promise in detecting thyroid cancer lesions; however, their detection rate is lower than 18F-FDG PET/CT. FAPI-based radiotracers, targeting fibroblast activation protein highly expressed in tumors, offer potential in the detection of lymph nodes and radioiodine-resistant metastases. RGD-based radiotracers, binding to integrin αvβ3 found on tumor cells and angiogenic blood vessels, demonstrate diagnostic accuracy in detecting radioiodine-resistant thyroid cancer metastases. 18F-TFB emerges as a promising PET tracer for imaging of lymph node metastases and recurrent DTC, offering advantages over traditional methods. Overall, these radiotracers show promise in enhancing diagnostic accuracy, patient stratification, and treatment selection in differentiated thyroid cancer, warranting further research and clinical validation. Given the promising staging capabilities of 18F-TFB and the efficacy of FAP-targeting tracers in advanced, potentially dedifferentiated cases, continued investigation in these domains is justified.

Social relationships, amyloid burden, and dementia: The ARIC-PET study

INTRODUCTION

This study aimed to assess whether social relationships in mid-life reduce the risk of dementia related to amyloid burden.

METHODS

Participants in the Atherosclerosis Risk in Communities (ARIC) study were assessed for social support and isolation (visit 2; 1990-1992). A composite measure, "social relationships," was generated. Brain amyloid was evaluated with florbetapir positron emission tomography (PET); (visit 5; 2012-2014). Incident dementia cases were identified following visit 5 through 2019 using ongoing surveillance. Relative contributions of mid-life social relationships and elevated brain amyloid to incident dementia were evaluated with Cox regression models.

RESULTS

Among 310 participants without dementia, strong mid-life social relationships were associated independently with lower dementia risk. Elevated late-life brain amyloid was associated with greater dementia risk.

DISCUSSION

Although mid-life social relationships did not moderate the relationship between amyloid burden and dementia, these findings affirm the importance of strong social relationships as a potentially protective factor against dementia.

Category Switching Test: A Brief Amyloid-β-Sensitive Assessment Tool for Mild Cognitive Impairment

The Category Switching Test (CaST) is a verbal fluency test with active semantic category switching. This study aimed to explore the association between CaST performance and brain amyloid-β (Aβ) burden in patients with mild cognitive impairment (MCI) and the neurofunctional mechanisms. A total of 112 participants with MCI underwent Florbetapir positron emission tomography, resting-state functional magnetic resonance imaging, and a neuropsychological test battery. The high Aβ burden group had worse CaST performance than the low-burden group. CaST score and left middle temporal gyrus fractional amplitude of low-frequency fluctuations (fALFF) related inversely to the global Florbetapir standardized uptake value rate. Functional connectivity between the left middle temporal gyrus and frontal lobe decreased widely and correlated with CaST score in the high Aβ burden group. Thus, CaST score and left middle temporal gyrus fALFF were valuable in discriminating high Aβ burden. CaST might be useful in screening for MCI with high Aβ burden.

Incremental value of amyloid PET in a tertiary memory clinic setting in China

INTRODUCTION

The objective of this study is to investigate the incremental value of amyloid positron emission tomography (Aβ-PET) in a tertiary memory clinic setting in China.

METHODS

A total of 1073 patients were offered Aβ-PET using 18F-florbetapir. The neurologists determined a suspected etiology (Alzheimer's disease [AD] or non-AD) with a percentage estimate of their confidence and medication prescription both before and after receiving the Aβ-PET results.

RESULTS

After disclosure of the Aβ-PET results, etiological diagnoses changed in 19.3% of patients, and diagnostic confidence increased from 69.3% to 85.6%. Amyloid PET results led to a change of treatment plan in 36.5% of patients. Compared to the late-onset group, the early-onset group had a more frequent change in diagnoses and a higher increase in diagnostic confidence.

DISCUSSION

Aβ-PET has significant impacts on the changes of diagnoses and management in Chinese population. Early-onset cases are more likely to benefit from Aβ-PET than late-onset cases.

HIGHLIGHTS

Amyloid PET contributes to diagnostic changes and its confidence in Chinese patients. Amyloid PET leads to a change of treatment plans in Chinese patients. Early-onset cases are more likely to benefit from amyloid PET than late-onset cases.

Prognostic Impact of Visceral Adipose Tissue Imaging Parameters in Patients with Cholangiocarcinoma after Surgical Resection

Visceral adiposity is known to be related to poor prognosis in patients with cholangiocarcinoma; however, the prognostic significance of the qualitative features of adipose tissue in cholangiocarcinoma has yet to be well defined. This study investigated the prognostic impact of adipose tissue imaging parameters reflecting the quantity and qualitative characteristics of subcutaneous (SAT) and visceral (VAT) adipose tissue on recurrence-free survival (RFS) and overall survival (OS) in 94 patients undergoing resection of cholangiocarcinoma. The area, mean computed tomography (CT) attenuation, and mean 2-deoxy-2-[18F]fluoro-D-glucose (FDG) uptake of SAT and VAT on positron emission tomography (PET)/CT for staging work-up were measured, and the relationship of these adipose tissue imaging parameters with clinicopathological factors and survival was assessed. TNM stage, histologic grade, lymphovascular invasion, and the size of cholangiocarcinoma showed positive correlations with adipose tissue imaging parameters. Multivariate survival analysis demonstrated that the visceral-to-subcutaneous adipose tissue area ratio (VSR) (p = 0.024; hazard ratio, 1.718) and mean FDG uptake of VAT (p = 0.033; hazard ratio, 9.781) were significant predictors for RFS, but all of the adipose tissue imaging parameters failed to show statistical significance for predicting OS. In addition to visceral adiposity, FDG uptake of VAT might be a promising prognostic parameter for predicting RFS in patients with cholangiocarcinoma.

Sensitive Positron Emission Tomography Imaging of PD-L1 Expression in Human Breast and Lung Carcinoma Xenografts Using the Radiometalated Peptide Ga-68-TRAP-WL12

Noninvasive imaging of the immune checkpoint protein programmed death ligand 1 (PD-L1; synonyms: CD274, B7-H1) holds great promise to improve patient selection and, thus, response rates for immune checkpoint therapy (ICT) with monoclonal antibodies targeting the PD1/PD-L1 axis. The PD-L1 specific peptide WL12 (cyclo(AcY-(NMe)A-N-P-H-L-Hyp-W-S-W(Me)-(NMe)Nle-(NMe)Nle-O-C)-G-NH2) was functionalized with the Gallium-68 chelator TRAP by means of click chemistry (CuAAC). The resulting conjugate TRAP-WL12 was labeled with Gallium-68 within 16 min, with approximately 90% radiochemical yield and 99% radiochemical purity, affording Ga-68-TRAP-WL12 with molar activities typically exceeding 100 MBq/nmol. This radiotracer was characterized by positron emission tomography (PET) imaging and ex vivo biodistribution in murine xenografts of nontransfected PD-L1 expressing tumor cell lines, MDA-MB-231 (human breast carcinoma), and H2009 (human lung adenocarcinoma). It showed a favorable biodistribution profile with rapid renal clearance and low background (tumor-to-blood ratio = 26.6, 3 h p.i.). Conjugation of the Ga-68-TRAP moiety to WL12 successfully mitigated the nonspecific uptake of this peptide in organs, particularly the liver. This was demonstrated by comparing Ga-68-TRAP-WL12 with the archetypical Ga-68-DOTA-WL12, for which tumor-to-liver ratios of 1.4 and 0.5, respectively, were found. Although immunohistochemistry (IHC) revealed a low PD-L1 expression in MDA-MB-213 and H2009 xenografts that corresponds well to the clinical situation, PET showed high tumor uptakes (6.6 and 7.3% injected activity per gram of tissue (iA/g), respectively) for Ga-68-TRAP-WL12. Thus, this tracer has the potential for routine clinical PD-L1 PET imaging because it detects even very low PD-L1 expression densities with high sensitivity and may open an avenue to replace PD-L1 IHC of biopsies as the standard means to select potential responders for ICT.

Efficient image reconstruction for a small animal PET system with dual-layer-offset detector design

BACKGROUND

A compact PET/SPECT/CT system Inliview-3000B has been developed to provide multi-modality information on small animals for biomedical research. Its PET subsystem employed a dual-layer-offset detector design for depth-of-interaction capability and higher detection efficiency, but the irregular design caused some difficulties in calculating the normalization factors and the sensitivity map. Besides, the relatively larger (2 mm) crystal cross-section size also posed a challenge to high-resolution image reconstruction.

PURPOSE

We present an efficient image reconstruction method to achieve high imaging performance for the PET subsystem of Inliview-3000B.

METHODS

List mode reconstruction with efficient system modeling was used for the PET imaging. We adopt an on-the-fly multi-ray tracing method with random crystal sampling to model the solid angle, crystal penetration and object attenuation effect, and modify the system response model during each iteration to improve the reconstruction performance and computational efficiency. We estimate crystal efficiency with a novel iterative approach that combines measured cylinder phantom data with simulated line-of-response (LOR)-based factors for normalization correction before reconstruction. Since it is necessary to calculate normalization factors and the sensitivity map, we stack the two crystal layers together and extend the conventional data organization method here to index all useful LORs. Simulations and experiments were performed to demonstrate the feasibility and advantage of the proposed method.

RESULTS

Simulation results showed that the iterative algorithm for crystal efficiency estimation could achieve good accuracy. NEMA image quality phantom studies have demonstrated the superiority of random sampling, which is able to achieve good imaging performance with much less computation than traditional uniform sampling. In the spatial resolution evaluation based on the mini-Derenzo phantom, 1.1 mm hot rods could be identified with the proposed reconstruction method. Reconstruction of double mice and a rat showed good spatial resolution and a high signal-to-noise ratio, and organs with higher uptake could be recognized well.

CONCLUSION

The results validated the superiority of introducing randomness into reconstruction, and demonstrated its reliability for high-performance imaging. The Inliview-3000B PET subsystem with the proposed image reconstruction can provide rich and detailed information on small animals for preclinical research.

The CONFIRM trial protocol: the utility of prostate-specific membrane antigen positron emission tomography/computed tomography in active surveillance for prostate cancer

OBJECTIVES

Primary objectives: To determine the additive value of prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) in the risk stratification of men with newly diagnosed prostate cancer (PCa) who would have otherwise been deemed suitable for active surveillance (AS). Specifically, we aim to determine if PSMA PET/CT can detect a cohort of men on AS that are in fact high risk and likely to experience unfavourable outcomes should they remain on their current treatment pathway.

SECONDARY OBJECTIVES

to determine the additive value of PSMA PET/CT to repeat multiparametric magnetic resonance imaging (mpMRI) of the prostate and explore whether a confirmatory biopsy may be avoided in men with a negative PSMA PET/CT and a negative repeat mpMRI of the prostate (Prostate Imaging-Reporting and Data System score of <3). Furthermore, to develop a nomogram combining clinical, imaging and biomarker data to predict the likelihood of failure on AS in men with high-risk features. Also, a blood sample will be taken to perform a Prostate Health Index test at the time of confirmatory biopsy. Furthermore, a portion of this blood will be stored at a biobank for up to 5 years if a follow-up study on molecular biomarkers and genetic assays in this cohort of men is indicated, based on the results from the CONFIRM trial.

PATIENTS AND METHODS

The CONFIRM trial is a prospective, multicentre, pre-test/post-test, cohort study across Victoria, Australia, involving men with newly diagnosed low-risk PCa with high-risk features, considered suitable for AS and undergoing confirmatory biopsy. The trial's goal is to provide high-quality evidence to establish whether PSMA PET/CT has a role in risk-stratifying men deemed suitable for AS despite having high-risk feature(s).

RESULTS

The CONFIRM trial will measure the proportion of men deemed unsuitable for ongoing AS based on pathological upgrading and multidisciplinary team recommendation due to PSMA PET/CT scan and PSMA-targeted confirmatory biopsy. Additionally, the positive and negative predictive values, sensitivity, and specificity of PSMA PET/CT will be calculated in isolation and combined with repeat mpMRI of the prostate.

CONCLUSIONS

This trial will provide robust prospective data to determine if PSMA-PET/CT and standard of care (prostate biopsy ± repeat mpMRI) can improve diagnostic certainty in men undergoing confirmatory biopsy for low-grade PCa with high-risk features.

Suboptimal self-reported sleep efficiency and duration are associated with faster accumulation of brain amyloid beta in cognitively unimpaired older adults

INTRODUCTION

This study investigated whether self-reported sleep quality is associated with brain amyloid beta (Aβ) accumulation.

METHODS

Linear mixed effect model analyses were conducted for 189 cognitively unimpaired (CU) older adults (mean ± standard deviation 74.0 ± 6.2; 53.2% female), with baseline self-reported sleep data, and positron emission tomography-determined brain Aβ measured over a minimum of three time points (range 33.3-72.7 months). Analyses included random slopes and intercepts, interaction for apolipoprotein E (APOE) ε4 allele status, and time, adjusting for sex and baseline age.

RESULTS

Sleep duration <6 hours, in APOE ε4 carriers, and sleep efficiency <65%, in the whole sample and APOE ε4 non-carriers, is associated with faster accumulation of brain Aβ.

DISCUSSION

These findings suggest a role for self-reported suboptimal sleep efficiency and duration in the accumulation of Alzheimer's disease (AD) neuropathology in CU individuals. Additionally, poor sleep efficiency represents a potential route via which individuals at lower genetic risk may progress to preclinical AD.

Highlights

In cognitively unimpaired older adults self-report sleep is associated with brain amyloid beta (Aβ) accumulation.Across sleep characteristics, this relationship differs by apolipoprotein E (APOE) genotype.Sleep duration <6 hours is associated with faster brain Aβ accumulation in APOE ε4 carriers.Sleep efficiency < 65% is associated with faster brain Aβ accumulation in APOE ε4 non-carriers.Personalized sleep interventions should be studied for potential to slow Aβ accumulation.

(18)F-fluorodeoxyglucose uptake by positron emission tomography in patients with IPAH and CTEPH

Pulmonary arterial hypertension (PAH) is driven by pathologies associated with increased metabolism such as pulmonary revascularization, vasoconstriction and smooth muscle cell proliferation in pulmonary artery wall. 18-fluorodeoxyglucose positron emission tomography (18FDG-PET) is an imaging technique sensitive to glucose metabolism and might be considered as a non-invasive method for diagnosis due to significant role of inflammation in idiopathic pulmonary artery hypertension (IPAH) and chronic thromboembolic pulmonary hypertension (CTEPH). The present study aimed to investigate the role of PET/CT imaging of patients with IPAH and CTEPH as an alternative diagnosis method. Demographic characteristics, FDG uptake in lungs, pulmonary artery and right ventricle (RV) of 17 patients (10 IPAH, 7 CTEPH), and 30 controls were evaluated. PET scanning, 6-min walk test, pro-BNP level, right heart catheterization of patients were performed both at the onsert and after 6-month PAH specific treatment. IPAH and CTEPH patients had significantly higher left lung FDG (p = 0.006), right lung FDG (p = 0.004), right atrial (RA) FDG (p < 0.001) and RV FDG (p < 0.001) uptakes than controls. Positive correlation was detected between the RV FDG uptake and the mean pulmonary artery pressure (mPAP) (r = 0.7, p = 0.012) and between the RA FDG uptake and the right atrial pressure (RAP) (r = 0.5, p = 0.02). Increased RV FDG and RA FDG uptakes predicts the presence of pulmonary hypertension and correlates with mPAP and RAP, respectively, which are important indicators in the prognosis of PAH. Further studies are required whether FDG PET imaging can be used to diagnose or predict the prognosis of pulmonary hypertension.

Tau accumulation and atrophy predict amyloid independent cognitive decline in aging

INTRODUCTION

Amyloid beta (Aβ) and tau pathology are cross-sectionally associated with atrophy and cognitive decline in aging and Alzheimer's disease (AD).

METHODS

We investigated relationships between concurrent longitudinal measures of Aβ (Pittsburgh compound B [PiB] positron emission tomography [PET]), tau (flortaucipir [FTP] PET), atrophy (structural magnetic resonance imaging), episodic memory (EM), and non-memory (NM) in 78 cognitively healthy older adults (OA).

RESULTS

Entorhinal FTP change was correlated with EM decline regardless of Aβ, but meta-temporal FTP and global PiB change were only associated with EM and NM decline in Aβ+ OA. Voxel-wise analyses revealed significant associations between temporal lobe FTP change and EM decline in all groups. PiB and FTP change were not associated with structural change, suggesting a functional or microstructural mechanism linking these measures to cognitive decline.

DISCUSSION

Our results show that longitudinal Aβ is linked to cognitive decline only in the presence of elevated Aβ, but longitudinal temporal lobe tau is associated with memory decline regardless of Aβ status.

HIGHLIGHTS

Entorhinal tau change was associated with memory decline in older adults (OA), regardless of amyloid beta (Aβ). Greater meta-region of interest (ROI) tau change correlated with memory decline in Aβ+ OA. Voxel-wise temporal tau change correlated with memory decline, regardless of Aβ. Meta-ROI tau and global amyloid change correlated with non-memory change in Aβ+ OA. Tau and amyloid accumulation were not associated with structural change in OA.

Real-world experience with 11C-methionine positron emission tomography in the management of acromegaly

BACKGROUND

L-[methyl-11C]-methionine-positron emission tomography (Met-PET) is a potentially important imaging adjunct in the diagnostic workup of pituitary adenomas, including somatotroph tumors. Met-PET can identify residual or occult disease and make definitive therapies accessible to a subgroup of patients who would otherwise require lifelong medical therapy. However, existing data on its use are still limited to small case series. Here, we report the largest single-center experience (n = 61) in acromegaly.

METHODS

A total of 189 cases of acromegaly were referred to our national Met-PET service in the last 12 years. For this analysis, we have reviewed outcomes in those 61 patients managed exclusively by our multidisciplinary team (single center, single surgeon). Referral indications were as follows: indeterminate magnetic resonance imaging (MRI; n = 38, 62.3%), occult residual (n = 14, 23.0%), (radio-)surgical planning (n = 6, 9.8%), and occult de novo tumor (n = 3, 4.9%).

RESULTS

A total of 33/61 patients (54.1%) underwent PET-guided surgery. Twenty-four of 33 patients (72.7%) achieved complete biochemical remission following (re-)surgery. Insulin-like growth factor 1 levels were reduced to <2 × upper limit of normal (ULN) in 6 of the remaining 9 cases, 3 of whom achieved levels of <1.1 × ULN compared with mean preoperative levels of 2.4 × ULN (SD 0.8) for n = 9. Only 3 patients developed single new hormonal deficits (gonadotropic/thyrotropic insufficiency). There were no neurovascular complications after surgery.

CONCLUSION

In patients with persistent/recurrent acromegaly or occult tumors, Met-PET can facilitate further targeted intervention (surgery/radiosurgery). This led to complete remission in most cases (24/33) or significant improvement with comparatively low risk of complications. L-[methyl-11C]-methionine-positron emission tomography should therefore be considered in all patients who are potential candidates for further surgical intervention but present no clear target on MRI.

Measurement of the12C(p,n)12N reaction cross section below 150 MeV

Objective. Proton therapy currently faces challenges from clinical complications on organs-at-risk due to range uncertainties. To address this issue, positron emission tomography (PET) of the proton-induced11C and15O activity has been used to provide feedback on the proton range. However, this approach is not instantaneous due to the relatively long half-lives of these nuclides. An alternative nuclide,12N (half-life 11 ms), shows promise for real-timein vivoproton range verification. Development of12N imaging requires better knowledge of its production reaction cross section.Approach. The12C(p,n)12N reaction cross section was measured by detecting positron activity of graphite targets irradiated with 66.5, 120, and 150 MeV protons. A pulsed beam delivery with 0.7-2 × 108protons per pulse was used. The positron activity was measured during the beam-off periods using a dual-head Siemens Biograph mCT PET scanner. The12N production was determined from activity time histograms.Main results. The cross section was calculated for 11 energies, ranging from 23.5 to 147 MeV, using information on the experimental setup and beam delivery. Through a comprehensive uncertainty propagation analysis, a statistical uncertainty of 2.6%-5.8% and a systematic uncertainty of 3.3%-4.6% were achieved. Additionally, a comparison between measured and simulated scanner sensitivity showed a scaling factor of 1.25 (±3%). Despite this, there was an improvement in the precision of the cross section measurement compared to values reported by the only previous study.Significance. Short-lived12N imaging is promising for real-timein vivoverification of the proton range to reduce clinical complications in proton therapy. The verification procedure requires experimental knowledge of the12N production cross section for proton energies of clinical importance, to be incorporated in a Monte Carlo framework for12N imaging prediction. This study is the first to achieve a precise measurement of the12C(p,n)12N nuclear cross section for such proton energies.

The prognostic value of visual and automatic coronary calcium -scoring from low dose CT-[15O]-water PET

PURPOSE

Firstly, to validate automatically and visually scored coronary artery calcium (CAC) on low dose CT (LDCT) scans with a dedicated calcium scoring CT (CSCT) scan. Secondly, to assess the added value of CAC scored from LDCT scans acquired during [15O]-water-PET myocardial perfusion imaging (MPI) on prediction of major adverse cardiac events (MACE).

METHODS

572 consecutive patients with suspected coronary artery disease, who underwent [15O]-water-PET MPI with LDCT and a dedicated CSCT scan were included. In the reference CSCT scans, manual CAC scoring was performed, while LDCT scans were scored visually and automatically using deep learning approach. Subsequently, based on CAC score results from CSCT and LDCT scans, each patient's scan was assigned to one out of five cardiovascular risk groups (0; 1-100; 101-400; 401-1000; >1000) and the agreement in risk group classification between CSCT and LDCT scans was investigated. MACE was defined as a composite of all-cause death, nonfatal myocardial infarction, coronary revascularization, and unstable angina.

RESULTS

The agreement in risk group classification between reference CSCT manual scoring and visual/automatic LDCT scoring from LDCT was 0.66 (95% CI: 0.62-0.70) and 0.58 (95% CI: 0.53-0.62), respectively. Based on visual and automatic CAC scoring from LDCT scans, patients with CAC>100 and CAC>400, respectively, were at increased risk of MACE, independently of ischemic information from the [15O]-water-PET scan.

CONCLUSIONS

There is a moderate agreement in risk classification between visual and automatic CAC scoring from LDCT and reference CSCT scans. Visual and automatic CAC scoring from LDCT scans improve identification of patients at higher risk of MACE.

Peptidoglycan-Targeted [18F]3,3,3-Trifluoro-d-alanine Tracer for Imaging Bacterial Infection

Imaging is increasingly used to detect and monitor bacterial infection. Both anatomic (X-rays, computed tomography, ultrasound, and MRI) and nuclear medicine ([111In]-WBC SPECT, [18F]FDG PET) techniques are used in clinical practice but lack specificity for the causative microorganisms themselves. To meet this challenge, many groups have developed imaging methods that target pathogen-specific metabolism, including PET tracers integrated into the bacterial cell wall. We have previously reported the d-amino acid derived PET radiotracers d-methyl-[11C]-methionine, d-[3-11C]-alanine, and d-[3-11C]-alanine-d-alanine, which showed robust bacterial accumulation in vitro and in vivo. Given the clinical importance of radionuclide half-life, in the current study, we developed [18F]3,3,3-trifluoro-d-alanine (d-[18F]-CF3-ala), a fluorine-18 labeled tracer. We tested the hypothesis that d-[18F]-CF3-ala would be incorporated into bacterial peptidoglycan given its structural similarity to d-alanine itself. NMR analysis showed that the fluorine-19 parent amino acid d-[19F]-CF3-ala was stable in human and mouse serum. d-[19F]-CF3-ala was also a poor substrate for d-amino acid oxidase, the enzyme largely responsible for mammalian d-amino acid metabolism and a likely contributor to background signals using d-amino acid derived PET tracers. In addition, d-[19F]-CF3-ala showed robust incorporation into Escherichia coli peptidoglycan, as detected by HPLC/mass spectrometry. Based on these promising results, we developed a radiosynthesis of d-[18F]-CF3-ala via displacement of a bromo-precursor with [18F]fluoride followed by chiral stationary phase HPLC. Unexpectedly, the accumulation of d-[18F]-CF3-ala by bacteria in vitro was highest for Gram-negative pathogens in particular E. coli. In a murine model of acute bacterial infection, d-[18F]-CF3-ala could distinguish live from heat-killed E. coli, with low background signals. These results indicate the viability of [18F]-modified d-amino acids for infection imaging and indicate that improved specificity for bacterial metabolism can improve tracer performance.

Case report: A 17-year-old male with primary pulmonary osteosarcoma

Primary pulmonary osteosarcoma is one of the extraskeletal osteosarcomas originating from the lung with an extremely low incidence and highly invasive potential. Here we report a case of primary pulmonary osteosarcoma treated in our hospital with a literature review. The patient, a 17-year-old male, had a cough and hemoptysis for 20 days. Computed tomography (CT) and positron emission tomography (PET)/CT were performed in our hospital. According to pathological examination after surgery, the tumor was diagnosed as a high-grade sarcoma with remarkable osteogenesis and necrosis. Based on radiological and histological examinations, a diagnosis of primary pulmonary osteosarcoma originating was considered. The patient underwent surgery and adjuvant chemotherapy. This patient has been under consecutive follow-up for nearly 8 years, showing no signs of recurrence or distant metastasis. Primary pulmonary osteosarcoma is a rare lung malignancy that shows rapid progression, nonspecific symptoms and inapparent signs at an early stage. The diagnosis of primary pulmonary osteosarcoma highly relies on imaging and histological examinations, among which chest CT is the predominant method to check this disease.

18F-Labeled PET Tracers Specific for Adenosine A2A Receptor: Design, Synthesis, and Biological Evaluation

By modifying the structures of targeted A2AR antagonists and tracers, novel compounds 3, 7a, 9, 12c, and BIBD-399 were designed and synthesized. In vitro inhibition experiments demonstrated that 3, 12c, and BIBD-399 have high affinity for A2AR. [18F]3 and [18F]BIBD-399 were successfully synthesized. In terms of biological distribution, the brain uptake of [18F]MNI-444 exhibits greater than that of [18F]3 and [18F]BIBD-399. PET imaging shows that [18F]3 is off-target in the brain, while [18F]BIBD-399 and [18F]MNI-444 can be specifically imaged in regions with high A2AR expression. Differently, [18F]BIBD-399 could quickly reach equilibrium in the targeted region within 10 min after administration, while [18F]MNI-444 shows a slowly increasing trend within 2 h of administration. [18F]BIBD-399 is mainly metabolized by the liver and kidney, and there is no obvious defluorination in vivo. Additional in vitro autoradiography showed that the striatal signals of [18F]BIBD-399 and [18F]MNI-444 were inhibited by the A2AR antagonist SCH442416 but not by the A1R antagonist DPCPX, demonstrating the high A2AR binding specificity of [18F]BIBD-399. Molecular docking further confirms the high affinity of MNI-444 and BIBD-399 for A2AR. Further tMCAo imaging showed that [18F]BIBD-399 can sensitively distinguish between infarcted and noninfarcted sides, a capability not observed with [18F]MNI-444. Given its pharmacokinetic properties and the ability to identify lesion regions, [18F]BIBD-399 has potential advantages in monitoring A2AR changes, meriting further clinical investigation.

Renal Cortical Glucose Uptake Is Decreased in Insulin Resistance and Correlates Inversely With Serum Free-fatty Acids

CONTEXT

Studies on human renal metabolism are scanty. Nowadays, functional imaging allows the characterization of renal metabolism in a noninvasive manner. We have recently demonstrated that fluorodeoxyglucose F18 (18F FDG) positron emission tomography can be used to analyze renal glucose uptake (GU) rates, and that the renal cortex is an insulin-sensitive tissue.

OBJECTIVE

To confirm that renal GU is decreased in people with obesity and to test whether circulating metabolites are related to renal GU.

DESIGN, SETTING AND PARTICIPANTS

Eighteen people with obesity and 18 nonobese controls were studied with [18F]FDG positron emission tomography during insulin clamp. Renal scans were obtained ∼60 minutes after [18F]FDG injection. Renal GU was measured using fractional uptake rate and after correcting for residual intratubular [18F]FDG. Circulating metabolites were measured using high-throughput proton nuclear magnetic resonance metabolomics.

RESULTS

Cortical GU was higher in healthy nonobese controls compared with people with obesity (4.7 [3.4-5.6] vs 3.1 [2.2-4.3], P = .004, respectively), and it associated positively with the degree of insulin sensitivity (M value) (r = 0.42, P = .01). Moreover, cortical GU was inversely associated with circulating β-OH-butyrate (r = -0.58, P = .009), acetoacetate (r = -0.48, P = .008), citrate (r = -0.44, P = .01), and free fatty acids (r = -0.68, P < .0001), even when accounting for the M value. On the contrary, medullary GU was not associated with any clinical parameters.

CONCLUSION

These data confirm differences in renal cortical GU between people with obesity and healthy nonobese controls. Moreover, the negative correlations between renal cortex GU and free fatty acids, ketone bodies, and citrate are suggestive of substrate competition in the renal cortex.

The detection instrumentation and geometric design of clinical PET scanner: towards better performance and broader clinical applications

Positron emission tomography (PET) is a powerful medical imaging modality used in nuclear medicine to diagnose and monitor various clinical diseases in patients. It is more sensitive and produces a highly quantitative mapping of the three-dimensional biodistribution of positron-emitting radiotracers inside the human body. The underlying technology is constantly evolving, and recent advances in detection instrumentation and PET scanner design have significantly improved the medical diagnosis capabilities of this imaging modality, making it more efficient and opening the way to broader, innovative, and promising clinical applications. Some significant achievements related to detection instrumentation include introducing new scintillators and photodetectors as well as developing innovative detector designs and coupling configurations. Other advances in scanner design include moving towards a cylindrical geometry, 3D acquisition mode, and the trend towards a wider axial field of view and a shorter diameter. Further research on PET camera instrumentation and design will be required to advance this technology by improving its performance and extending its clinical applications while optimising radiation dose, image acquisition time, and manufacturing cost. This article comprehensively reviews the various parameters of detection instrumentation and PET system design. Firstly, an overview of the historical innovation of the PET system has been presented, focusing on instrumental technology. Secondly, we have characterised the main performance parameters of current clinical PET and detailed recent instrumental innovations and trends that affect these performances and clinical practice. Finally, prospects for this medical imaging modality are presented and discussed. This overview of the PET system's instrumental parameters enables us to draw solid conclusions on achieving the best possible performance for the different needs of different clinical applications.

Striatal and Extrastriatal Monoaminergic Disruption in Progressive Supranuclear Palsy

BACKGROUND

As a biomarker targeting vesicular monoamine transporter 2 (VMAT2), 18 F-9-fluoropropyldihydrotetrabenazine (18 F-FP-DTBZ) positron emission tomography (PET) is highly accurate in diagnosing Parkinson's disease (PD) and assessing its severity. However, evidence is insufficient in patients with progressive supranuclear palsy (PSP).

OBJECTIVE

We evaluated the striatal and extrastriatal monoaminergic disruption of PSP and differences in patterns between patients with PSP, PD, and healthy controls (HCs) using 18 F-FP-DTBZ PET, as well as its correlations with the clinical characteristics of PSP.

METHODS

We recruited 58 patients with PSP, 23 age- and duration-matched patients with PD, as well as 17 HCs. Patients were scanned using 18 F-FP-DTBZ PET/computed tomography, and images were spatially normalized and analyzed based on the volume of interest.

RESULTS

VMAT2 binding differed significantly in the striatum and substantia nigra among the groups (P < 0.001). A more severe disruption in the caudate was noted in the PSP group (P < 0.001) than in the PD group. However, no differences were found in the nucleus accumbens, hippocampus, amygdala, or raphe between the PD and PSP groups. Within the PSP group, striatal VMAT2 binding was significantly associated with the fall/postural stability subscore of the PSP Rating Scale, especially in the putamen. Furthermore, VMAT2 binding was correlated with Mini-Mental State Examination or Montreal Cognitive Assessment in the hippocampus.

CONCLUSIONS

Caudate disruptions showed prominent differences among the groups. VAMT2 binding in the striatum and hippocampus reflects the severity of fall/postural stability and cognition, respectively. © 2024 International Parkinson and Movement Disorder Society.

Imaging quantitative changes in blood-brain barrier permeability using [18F]2-fluoro-2-deoxy-sorbitol ([18F]FDS) PET in relation to glial cell recruitment in a mouse model of endotoxemia

The quantitative relationship between the disruption of the blood-brain barrier (BBB) and the recruitment of glial cells was explored in a mouse model of endotoxemia. [18F]2-Fluoro-2-deoxy-sorbitol ([18F]FDS) PET imaging was used as a paracellular marker for quantitative monitoring of BBB permeability after i.v injection of increasing doses of lipopolysaccharide (LPS) or vehicle (saline, n = 5). The brain distribution of [18F]FDS (VT, mL.cm-3) was estimated using kinetic modeling. LPS dose-dependently increased the brain VT of [18F]FDS after injection of LPS 4 mg/kg (5.2 ± 2.4-fold, n = 4, p < 0.01) or 5 mg/kg (9.0 ± 9.1-fold, n = 4, p < 0.01) but not 3 mg/kg (p > 0.05, n = 7). In 12 individuals belonging to the different groups, changes in BBB permeability were compared with expression of markers of astrocyte (GFAP) and microglial cell (CD11b) using ex vivo immunohistochemistry. Increased expression of CD11b and GFAP expression was observed in mice injected with 3 mg/kg of LPS, which did not increase with higher LPS doses. Quantitative [18F]FDS PET imaging can capture different levels of BBB permeability in vivo. A biphasic effect was observed with the lowest dose of LPS that triggered neuroinflammation without disruptive changes in BBB permeability, and higher LPS doses that increased BBB permeability without additional recruitment of glial cells.

Cholinergic changes in Lewy body disease: implications for presentation, progression and subtypes

Cholinergic degeneration is significant in Lewy body disease, including Parkinson's disease, dementia with Lewy bodies, and isolated REM sleep behavior disorder. Extensive research has demonstrated cholinergic alterations in the central nervous system of these disorders. More recently, studies have revealed cholinergic denervation in organs that receive parasympathetic denervation. This enables a comprehensive review of cholinergic changes in Lewy body disease, encompassing both central and peripheral regions, various disease stages, and diagnostic categories. Across studies, brain regions affected in Lewy body dementia show equal or greater levels of cholinergic impairment compared to the brain regions affected in Lewy body disease without dementia. This observation suggests a continuum of cholinergic alterations between these disorders. Patients without dementia exhibit relative sparing of limbic regions, whereas occipital and superior temporal regions appear to be affected to a similar extent in patients with and without dementia. This implies that posterior cholinergic cell groups in the basal forebrain are affected in the early stages of Lewy body disorders, while more anterior regions are typically affected later in the disease progression. The topographical changes observed in patients affected by comorbid Alzheimer pathology may reflect a combination of changes seen in pure forms of Lewy body disease and those seen in Alzheimer's disease. This suggests that Alzheimer co-pathology is important to understand cholinergic degeneration in Lewy body disease. Thalamic cholinergic innervation is more affected in Lewy body patients with dementia compared to those without dementia, and this may contribute to the distinct clinical presentations observed in these groups. In patients with Alzheimer's disease, the thalamus is variably affected, suggesting a different sequential involvement of cholinergic cell groups in Alzheimer's disease compared to Lewy body disease. Patients with isolated REM sleep behavior disorder demonstrate cholinergic denervation in abdominal organs that receive parasympathetic innervation from the dorsal motor nucleus of the vagus, similar to patients who experienced this sleep disorder in their prodrome. This implies that REM sleep behavior disorder is important for understanding peripheral cholinergic changes in both prodromal and manifest phases of Lewy body disease. In conclusion, cholinergic changes in Lewy body disease carry implications for understanding phenotypes and the influence of Alzheimer co-pathology, delineating subtypes and pathological spreading routes, and for developing tailored treatments targeting the cholinergic system.

Nuclear imaging to visualize periodontal inflammation: Findings of a randomized controlled trial

OBJECTIVE

To investigate non-surgical periodontal therapy by 18F-fluorodeoxyglucose (2-[18 F]FDG) uptake using positron emission tomography (PET) integrated with computed tomography (CT).

SUBJECTS

Eighty-five patients with peripheral artery disease and severe periodontitis-randomized into three groups receiving therapy with (PT1; n = 29) or without (PT2; n = 28) systemic antibiotics or no treatment (controls: n = 28)-underwent nuclear imaging at baseline and at 3 months.

RESULTS

Clinical inflammation (periodontal inflamed surface area; PISA) did not significantly differ across the groups at baseline (p = 0.395) but was significantly reduced at 3 months (p < 0.001), and significantly more so in the PT1/PT2 groups than in the control group (p < 0.001/=0.025) and in the PT1 than in the P2 group (p = 0.001). Radiotracer uptake was measured in both jaws using maximum and mean 'standardized uptake values' (SUVmax , SUVmean ) and 'target-to-background ratios' (TBRmax , TBRmean ). At 3 months, reductions were relatively small in absolute numbers and fell short of revealing correlations with PISA or significant differences across the groups. Still, they were very consistent in both treatment groups, whereas reductions were not consistently seen in the control group.

CONCLUSIONS

2-[18 F]FDG PET/CT scans did reflect the clinical effects of periodontal treatment very consistently but, for reasons yet to be clarified, less closely than expected.

Longitudinal associations of serum biomarkers with early cognitive, amyloid and grey matter changes

Blood-based biomarkers have been extensively evaluated for their diagnostic potential in Alzheimer's disease. However, their relative prognostic and monitoring capabilities for cognitive decline, amyloid-β (Aβ) accumulation and grey matter loss in cognitively unimpaired elderly require further investigation over extended time periods. This prospective cohort study in cognitively unimpaired elderly [n = 185, mean age (range) = 69 (53-84) years, 48% female] examined the prognostic and monitoring capabilities of glial fibrillary acidic protein (GFAP), neurofilament light (NfL), Aβ1-42/Aβ1-40 and phosphorylated tau (pTau)181 through their quantification in serum. All participants underwent baseline Aβ-PET, MRI and blood sampling as well as 2-yearly cognitive testing. A subset additionally underwent Aβ-PET (n = 109), MRI (n = 106) and blood sampling (n = 110) during follow-up [median time interval (range) = 6.1 (1.3-11.0) years]. Matching plasma measurements were available for Aβ1-42/Aβ1-40 and pTau181 (both n = 140). Linear mixed-effects models showed that high serum GFAP and NfL predicted future cognitive decline in memory (βGFAP×Time = -0.021, PFDR = 0.007 and βNfL×Time = -0.031, PFDR = 0.002) and language (βGFAP×Time = -0.021, PFDR = 0.002 and βNfL×Time = -0.018, PFDR = 0.03) domains. Low serum Aβ1-42/Aβ1-40 equally but independently predicted memory decline (βAβ1-42/Aβ1-40×Time = -0.024, PFDR = 0.02). Whole-brain voxelwise analyses revealed that low Aβ1-42/Aβ1-40 predicted Aβ accumulation within the precuneus and frontal regions, high GFAP and NfL predicted grey matter loss within hippocampal regions and low Aβ1-42/Aβ1-40 predicted grey matter loss in lateral temporal regions. Serum GFAP, NfL and pTau181 increased over time, while Aβ1-42/Aβ1-40 decreased only in Aβ-PET-negative elderly. NfL increases associated with declining memory (βNfLchange×Time = -0.030, PFDR = 0.006) and language (βNfLchange×Time = -0.021, PFDR = 0.02) function and serum Aβ1-42/Aβ1-40 decreases associated with declining language function (βAβ1-42/Aβ1-40×Time = -0.020, PFDR = 0.04). GFAP increases associated with Aβ accumulation within the precuneus and NfL increases associated with grey matter loss. Baseline and longitudinal serum pTau181 only associated with Aβ accumulation in restricted occipital regions. In head-to-head comparisons, serum outperformed plasma Aβ1-42/Aβ1-40 (ΔAUC = 0.10, PDeLong, FDR = 0.04), while both plasma and serum pTau181 demonstrated poor performance to detect asymptomatic Aβ-PET positivity (AUC = 0.55 and 0.63, respectively). However, when measured with a more phospho-specific assay, plasma pTau181 detected Aβ-positivity with high performance (AUC = 0.82, PDeLong, FDR < 0.007). In conclusion, serum GFAP, NfL and Aβ1-42/Aβ1-40 are valuable prognostic and/or monitoring tools in asymptomatic stages providing complementary information in a time- and pathology-dependent manner.

Parenchymal CSF fraction is a measure of brain glymphatic clearance and positively associated with amyloid beta deposition on PET

INTRODUCTION

Mapping of microscopic changes in the perivascular space (PVS) of the cerebral cortex, beyond magnetic resonance-visible PVS in white matter, may enhance our ability to diagnose Alzheimer's disease (AD) early.

METHODS

We used the cerebrospinal fluid (CSF) water fraction (CSFF), a magnetic resonance imaging-based biomarker, to characterize brain parenchymal CSF water, reflecting microscopic PVS in parenchyma. We measured CSFF and amyloid beta (Aβ) using 11 C Pittsburgh compound B positron emission tomography to investigate their relationship at both the subject and voxel levels.

RESULTS

Our research has demonstrated a positive correlation between the parenchymal CSFF, a non-invasive imaging biomarker indicative of parenchymal glymphatic clearance, and Aβ deposition, observed at both individual and voxel-based assessments in the posterior cingulate cortex.

DISCUSSION

This study shows that an increased parenchymal CSFF is associated with Aβ deposition, suggesting that CSFF could serve as a biomarker for brain glymphatic clearance, which can be used to detect early fluid changes in PVS predisposing individuals to the development of AD.

HIGHLIGHTS

Cerebrospinal fluid fraction (CSFF) could be a biomarker of parenchymal perivascular space. CSFF is positively associated with amyloid beta (Aβ) deposition at subject level. CSFF in an Aβ+ region is higher than in an Aβ- region in the posterior cingulate cortex. Correspondence is found between Aβ deposition and glymphatic clearance deficits measured by CSFF.

Tracers and Imaging of Fatty Acid and Energy Metabolism of Human Adipose Tissues

White adipose tissue and brown adipose tissue (WAT and BAT) regulate fatty acid metabolism and control lipid fluxes to other organs. Dysfunction of these key metabolic processes contributes to organ insulin resistance and inflammation leading to chronic diseases such as type 2 diabetes, metabolic dysfunction-associated steatohepatitis, and cardiovascular diseases. Metabolic tracers combined with molecular imaging methods are powerful tools for the investigation of these pathogenic mechanisms. Herein, I review some of the positron emission tomography and magnetic resonance imaging methods combined with stable isotopic metabolic tracers to investigate fatty acid and energy metabolism, focusing on human WAT and BAT metabolism. I will discuss the complementary strengths offered by these methods for human investigations and current gaps in the field.

Positron emission computed tomography targeting urokinase plasminogen activator receptor (uPAR) in cancer: a systematic review

INTRODUCTION

To provide an overview of the available literature data on clinical applications of positron emission tomography (PET) targeting the urokinase-type plasminogen activator receptor in oncology.

METHODS

A literature search was conducted in PubMed, Web of Science and Scopus databases up to June 2023. The results were presented according to the PRISMA guidelines. The quality of the studies was assessed using the Critical Appraisal Skill Program checklist.

RESULTS

Seven papers were selected for final analysis, involving 266 patients with solid tumors who underwent PET with uPAR-ligands. Thematic areas identified include feasibility studies (n = 2) on the safety, pharmacokinetics, and dosimetry of uPAR-targeting radiopharmaceuticals; uPAR-directed imaging in head and neck cancer (n = 2); uPAR PET in prostate cancer (n = 2); and the investigation of uPAR in neuroendocrine neoplasms (n = 1). Six of the seven studies used the radiopharmaceutical [68Ga]Ga-NOTA-AE105 while one study used [64Cu]Cu-DOTA-AE105. The studies showed protocol homogeneity, with static PET imaging at 20 minutes. The quality assessment revealed limitations such as small cohorts and the fact that all studies were performed by a single research group.

CONCLUSIONS

uPAR-PET appears to be a promising imaging tool in well-selected oncological settings, but it needs to be validated by multicentre collaboration.

Brain PET imaging using 11C-flumazenil and 11C-buprenorphine does not support the hypothesis of a mutual interaction between buprenorphine and benzodiazepines at the neuroreceptor level

Among opioids, buprenorphine presents a favorable safety profile with a limited risk of respiratory depression. However, fatalities have been reported when buprenorphine is combined to a benzodiazepine. Potentiation of buprenorphine interaction with opioid receptors (ORs) with benzodiazepines, and/or vice versa, is hypothesized to explain this drug-drug interaction (DDI). The mutual DDI between buprenorphine and benzodiazepines was investigated at the neuroreceptor level in nonhuman primates (n = 4 individuals) using brain PET imaging and kinetic modelling. The binding potential (BPND) of benzodiazepine receptor (BzR) was assessed using 11C-flumazenil PET imaging before and after administration of buprenorphine (0.2 mg, i.v.). Moreover, the brain kinetics and receptor binding of buprenorphine were investigated in the same individuals using 11C-buprenorphine PET imaging before and after administration of diazepam (10 mg, i.v.). Outcome parameters were compared using a two-way ANOVA. Buprenorphine did not impact the plasma nor brain kinetics of 11C-flumazenil. 11C-flumazenil BPND was unchanged following buprenorphine exposure, in any brain region (p > 0.05). Similarly, diazepam did not impact the plasma or brain kinetics of 11C-buprenorphine. 11C-buprenorphine volume of distribution (VT) was unchanged following diazepam exposure, in any brain region (p > 0.05). To conclude, our PET imaging findings do not support a neuropharmacokinetic or neuroreceptor-related mechanism of the buprenorphine/benzodiazepine interaction.

Effects of the active amyloid beta immunotherapy CAD106 on PET measurements of amyloid plaque deposition in cognitively unimpaired APOE ε4 homozygotes

INTRODUCTION

Alzheimer's Prevention Initiative Generation Study 1 evaluated amyloid beta (Aβ) active immunotherapy (vaccine) CAD106 and BACE-1 inhibitor umibecestat in cognitively unimpaired 60- to 75-year-old participants at genetic risk for Alzheimer's disease (AD). The study was reduced in size and terminated early. Results from the CAD106 cohort are presented.

METHODS

Sixty-five apolipoprotein E ε4 homozygotes with/without amyloid deposition received intramuscular CAD106 450 μg (n = 42) or placebo (n = 23) at baseline; Weeks 1, 7, 13; and quarterly; 51 of them had follow-up Aβ positron emission tomography (PET) scans at 18 to 24 months.

RESULTS

CAD106 induced measurable serum Aβ immunoglobulin G titers in 41/42 participants, slower rates of Aβ plaque accumulation (mean [standard deviation] annualized change from baseline in amyloid PET Centiloid: -0.91[5.65] for CAD106 versus 8.36 [6.68] for placebo; P < 0.001), and three amyloid-related imaging abnormality cases (one symptomatic).

DISCUSSION

Despite early termination, these findings support the potential value of conducting larger prevention trials of Aβ active immunotherapies in individuals at risk for AD.

HIGHLIGHTS

This was the first amyloid-lowering prevention trial in persons at genetic risk of late-onset Alzheimer's disease (AD). Active immunotherapy targeting amyloid (CAD106) was tested in this prevention trial. CAD106 significantly slowed down amyloid plaque deposition in apolipoprotein E homozygotes. CAD106 was generally safe and well tolerated, with only three amyloid-related imaging abnormality cases (one symptomatic). Such an approach deserves further evaluation in larger AD prevention trials.

Image Translation for Estimating Two-Dimensional Axial Amyloid-Beta PET From Structural MRI

BACKGROUND

Amyloid-beta and brain atrophy are hallmarks for Alzheimer's Disease that can be targeted with positron emission tomography (PET) and MRI, respectively. MRI is cheaper, less-invasive, and more available than PET. There is a known relationship between amyloid-beta and brain atrophy, meaning PET images could be inferred from MRI.

PURPOSE

To build an image translation model using a Conditional Generative Adversarial Network able to synthesize Amyloid-beta PET images from structural MRI.

STUDY TYPE

Retrospective.

POPULATION

Eight hundred eighty-two adults (348 males/534 females) with different stages of cognitive decline (control, mild cognitive impairment, moderate cognitive impairment, and severe cognitive impairment). Five hundred fifty-two subjects for model training and 331 for testing (80%:20%).

FIELD STRENGTH/SEQUENCE

3 T, T1-weighted structural (T1w).

ASSESSMENT

The testing cohort was used to evaluate the performance of the model using the Structural Similarity Index Measure (SSIM) and Peak Signal-to-Noise Ratio (PSNR), comparing the likeness of the overall synthetic PET images created from structural MRI with the overall true PET images. SSIM was computed in the overall image to include the luminance, contrast, and structural similarity components. Experienced observers reviewed the images for quality, performance and tried to determine if they could tell the difference between real and synthetic images.

STATISTICAL TESTS

Pixel wise Pearson correlation was significant, and had an R2 greater than 0.96 in example images. From blinded readings, a Pearson Chi-squared test showed that there was no significant difference between the real and synthetic images by the observers (P = 0.68).

RESULTS

A high degree of likeness across the evaluation set, which had a mean SSIM = 0.905 and PSNR = 2.685. The two observers were not able to determine the difference between the real and synthetic images, with accuracies of 54% and 46%, respectively.

CONCLUSION

Amyloid-beta PET images can be synthesized from structural MRI with a high degree of similarity to the real PET images.

EVIDENCE LEVEL

3 TECHNICAL EFFICACY: Stage 1.

Prevalence and Prognostic Importance of Abnormal Positron Emission Tomography Among Asymptomatic Patients With Diabetes Mellitus

BACKGROUND

Ischemia and reduced global myocardial blood flow reserve (MBFR) are associated with high cardiovascular risk among symptomatic patients with diabetes mellitus (DM).

OBJECTIVES

This study aimed to assess the prevalence and prognostic importance of silent ischemia and reduced MBFR among asymptomatic patients with DM.

METHODS

This study included 2,730 consecutive patients with DM, without known coronary artery disease (CAD) or cardiomyopathy, who underwent rubidium-82 rest/stress positron emission tomography (PET) myocardial perfusion imaging (MPI) from 2010 to 2016. These patients were followed up for all-cause mortality (n = 461) for a median follow-up of 3 years. Patients were considered asymptomatic if neither chest pain nor dyspnea was elicited. Rates of ischemia, reduced MBFR, and coronary microvascular dysfunction on PET were assessed in both groups. Cox regression was used to define the independent association of abnormal MPI markers with mortality.

RESULTS

One-quarter of patients with DM (23.7%; n = 647) were asymptomatic; ischemia was present in 30.5% (n = 197), reduced MBFR in 62.3% (n = 361), and coronary microvascular dysfunction in 32.7% (n = 200). In adjusted analyses, reduced MBFR (HR per 0.1 unit decrease in MBFR: 1.08 [95% CI: 1.03-1.12]; P = 0.001) and reduced ejection fraction (HR per 5% decrease: 1.10 [95% CI: 1.01-1.18]; P = 0.02) were independently prognostic of mortality among asymptomatic patients, but ischemia was not. This was comparable to DM patients with symptoms. Insulin use and older age were significant predictors of reduced MBFR among asymptomatic patients with DM.

CONCLUSIONS

In both symptomatic and asymptomatic patients with DM, impairment in MBFR is common and associated with greater mortality risk.

Sarcoidosis With Multiple Bone Lesions Mimicking Advanced Lung Cancer With Multiple Bone Metastases

Bone lesions in sarcoidosis are more common than previously known. A 59-year-old female with a history of sarcoidosis was referred due to suspected lung cancer. 18F-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) revealed numerous bone lesions in addition to abnormal uptake by pulmonary nodules and mediastinal lymph nodes, which mimicked metastatic advanced lung cancer. Biopsy of bone lesions detected epithelioid cell granuloma consistent with bone sarcoidosis. Moreover, prednisolone treatment was tried to exclude malignant disease. One month after prednisolone administration, bone lesions and other abnormal uptake disappeared on PET/CT. Bone sarcoidosis is often asymptomatic and is discovered incidentally as multiple lesions that may require differentiation from malignant disease. Biopsy of bone lesions and administration of corticosteroids may be useful for accurate diagnosis.

Radiosynthesis and whole-body distribution in mice of a 18 F-labeled azepino[4,3-b]indole-1-one derivative with multimodal activity for the treatment of Alzheimer's disease

Recently, the azepino[4,3-b]indole-1-one derivative 1 showed in vitro nanomolar inhibition against butyrylcholinesterase (BChE), the ChE isoform that plays a role in the progression and pathophysiology of Alzheimer's disease (AD), and protects against N-methyl- d-aspartate-induced neuronal toxicity. Three 9-R-substituted (R = F, Br, OMe) congeners were investigated. The 9-F derivative (2a) was found more potent as BChE inhibitors (half-maximal inhibitory concentration value = 21 nM) than 2b (9-Br) and 2c (9-OMe), achieving a residence time (38 s), assessed by surface plasmon resonance, threefold higher than that of 1. To progress in featuring the in vivo pharmacological characterization of 2a, herein the 18 F-labeled congener 2a was synthesized, by applying the aromatic 18 F-fluorination method, and its whole-body distribution in healthy mice, including brain penetration, was evaluated through positron emission tomography imaging. [18 F]2a exhibited a rapid and high brain uptake (3.35 ± 0.26% ID g-1 at 0.95 ± 0.15 min after injection), followed by a rapid clearance (t1/2  = 6.50 ± 0.93 min), showing good blood-brain barrier crossing. After a transient liver accumulation of [18 F]2a, the intestinal and urinary excretion was quantified. Finally, ex vivo pharmacological experiments in mice showed that the unlabeled 2a affects the transmitters' neurochemistry, which might be favorable to reverse cognition impairment in mild-to-moderate AD-related dementias.