Evaluation of carotid plaque inflammation in patients with active rheumatoid arthritis using (18)F-fluorodeoxyglucose PET-CT and MRI: a pilot study

A responsive nanoplatform with molecular and structural imaging capacity for assisting accurate diagnosis of early rheumatoid arthritis

Accurate early diagnosis of rheumatoid arthritis (RA) and prompt implementation of appropriate treatment approaches are crucial. In the clinic, magnetic resonance imaging (MRI) has been recommended for implementation to aid in the precise and early diagnosis of RA. However, they are still limited by issues regarding specificity and their ability to capture comprehensive information about the pathological features. Herein, a responsive multifunctional nanoplatform with targeting capabilities (hMnO2-IR@BSA-PEG-FA) is constructed through integrating a RA microenvironment-responsive MRI contrast agent with activatable near-infrared (NIR) fluorescence imaging, aiming to simultaneously acquire comprehensive pathological features of RA from both structural and molecular imaging perspectives. Moreover, taking advantage of its targeting function to synovial microphages, hMnO2-IR@BSA-PEG-FA demonstrated a remarkable capability to accumulate effectively at the synovial tissue. Additionally, hMnO2 responded to the mild acidity and reactive oxygen species (ROS) in the RA microenvironment, leading to the controlled release of Mn2+ ions and IR780, which separately caused special MRI contrast enhancement of synovial tissues and sensitively demonstrated the presence of ROS and weakly acid microenvironment by NIR imaging. Consequently, hMnO2-IR@BSA-PEG-FA is expected to serve as a promising nanoplatform, offering valuable assistance in the precise diagnosis of early-stage RA by specially providing comprehensive information about the pathological features.

Cardiovascular complications of rheumatoid arthritis

PURPOSE OF REVIEW

Rheumatoid arthritis (RA) patients remain at higher cardiovascular (CV) risk compared to non-RA patients, driven by accelerated atherosclerosis, leading to plaque rupture and acute CV events (CVE), including heart failure (HF). It has been hypothesized that chronic inflammation is the main driving force behind such outcomes. We summarize the current evidence supporting this hypothesis, focusing on arterial disease and myocardial disease.

RECENT FINDINGS

RA patients demonstrate higher prevalence of subclinical atherosclerosis (high risk plaque and arterial inflammation) compared to non-RA patients, with RA disease activity correlating independently with CVE and death. Nonischemic HF with preserved ejection fraction (HFpEF) is more common in RA compared to non-RA, with subclinical myocardial structural and functional alterations also more prevalent in RA. HFpEF and myocardial remodeling and dysfunction bear a strong and independent association with inflammatory correlates.

SUMMARY

All of this suggests that inflammation contributes to enhanced risk of CVE in RA. A more accurate and specific CV risk stratification tool for RA, incorporating biomarkers or imaging, is needed. Likewise, more prospective studies outlining the trajectory from preclinical to clinical HF, incorporating biomarkers and imaging, are also needed.

Imaging in inflammatory arthritis: progress towards precision medicine

Imaging techniques such as ultrasonography and MRI have gained ground in the diagnosis and management of inflammatory arthritis, as these imaging modalities allow a sensitive assessment of musculoskeletal inflammation and damage. However, these techniques cannot discriminate between disease subsets and are currently unable to deliver an accurate prediction of disease progression and therapeutic response in individual patients. This major shortcoming of today's technology hinders a targeted and personalized patient management approach. Technological advances in the areas of high-resolution imaging (for example, high-resolution peripheral quantitative computed tomography and ultra-high field MRI), functional and molecular-based imaging (such as chemical exchange saturation transfer MRI, positron emission tomography, fluorescence optical imaging, optoacoustic imaging and contrast-enhanced ultrasonography) and artificial intelligence-based data analysis could help to tackle these challenges. These new imaging approaches offer detailed anatomical delineation and an in vivo and non-invasive evaluation of the immunometabolic status of inflammatory reactions, thereby facilitating an in-depth characterization of inflammation. By means of these developments, the aim of earlier diagnosis, enhanced monitoring and, ultimately, a personalized treatment strategy looms closer.

A cross-scanner and cross-tracer deep learning method for the recovery of standard-dose imaging quality from low-dose PET

PURPOSE

A critical bottleneck for the credibility of artificial intelligence (AI) is replicating the results in the diversity of clinical practice. We aimed to develop an AI that can be independently applied to recover high-quality imaging from low-dose scans on different scanners and tracers.

METHODS

Brain [18F]FDG PET imaging of 237 patients scanned with one scanner was used for the development of AI technology. The developed algorithm was then tested on [18F]FDG PET images of 45 patients scanned with three different scanners, [18F]FET PET images of 18 patients scanned with two different scanners, as well as [18F]Florbetapir images of 10 patients. A conditional generative adversarial network (GAN) was customized for cross-scanner and cross-tracer optimization. Three nuclear medicine physicians independently assessed the utility of the results in a clinical setting.

RESULTS

The improvement achieved by AI recovery significantly correlated with the baseline image quality indicated by structural similarity index measurement (SSIM) (r = -0.71, p < 0.05) and normalized dose acquisition (r = -0.60, p < 0.05). Our cross-scanner and cross-tracer AI methodology showed utility based on both physical and clinical image assessment (p < 0.05).

CONCLUSION

The deep learning development for extensible application on unknown scanners and tracers may improve the trustworthiness and clinical acceptability of AI-based dose reduction.

Development of a deep learning method for CT-free correction for an ultra-long axial field of view PET scanner

INTRODUCTION

The possibility of low-dose positron emission tomography (PET) imaging using high sensitivity long axial field of view (FOV) PET/computed tomography (CT) scanners makes CT a critical radiation burden in clinical applications. Artificial intelligence has shown the potential to generate PET images from non-corrected PET images. Our aim in this work is to develop a CT-free correction for a long axial FOV PET scanner.

METHODS

Whole body PET images of 165 patients scanned with a digital regular FOV PET scanner (Biograph Vision 600 (Siemens Healthineers) in Shanghai and Bern) was included for the development and testing of the deep learning methods. Furthermore, the developed algorithm was tested on data of 7 patients scanned with a long axial FOV scanner (Biograph Vision Quadra, Siemens Healthineers). A 2D generative adversarial network (GAN) was developed featuring a residual dense block, which enables the model to fully exploit hierarchical features from all network layers. The normalized root mean squared error (NRMSE) and peak signal-to-noise ratio (PSNR), were calculated to evaluate the results generated by deep learning.

RESULTS

The preliminary results showed that, the developed deep learning method achieved an average NRMSE of 0.4±0.3% and PSNR of 51.4±6.4 for the test on Biograph Vision, and an average NRMSE of 0.5±0.4% and PSNR of 47.9±9.4 for the validation on Biograph Vision Quadra, after applied transfer learning.

CONCLUSION

The developed deep learning method shows the potential for CT-free AI-correction for a long axial FOV PET scanner. Work in progress includes clinical assessment of PET images by independent nuclear medicine physicians. Training and fine-tuning with more datasets will be performed to further consolidate the development.

Arterial wall inflammation in rheumatoid arthritis is reduced by anti-inflammatory treatment

BACKGROUND

Rheumatoid arthritis (RA) patients have an increased risk of cardiovascular disease (CVD), partly due to an increased prevalence of cardiovascular risk factors, but also due to chronic systemic inflammation inducing atherosclerotic changes of the arterial wall. The aim of this study was to determine whether anti-inflammatory therapy for the treatment of RA has favorable effects on arterial wall inflammation in RA patients.

METHODS

Arterial wall inflammation before and after 6 months of anti-inflammatory treatment was assessed in 49 early and established RA patients using 18F-fluorodeoxyglucose-positron emission tomography with computed tomography (18F-FDG-PET/CT). Arterial 18F-FDG uptake was quantified as maximum standardized uptake value (SUVmax) in the thoracic aorta, abdominal aorta, carotid, iliac and femoral arteries. Early RA patients (n = 26) were treated with conventional synthetic disease modifying anti-rheumatic drugs with or without corticosteroids, whereas established RA patients (n = 23) were treated with adalimumab.

RESULTS

In RA patients, overall SUVmax was over time reduced by 4% (difference -0.06, 95%CI -0.12 to -0.01, p = 0.02), with largest reductions in carotid (-8%, p = 0.001) and femoral arteries (-7%, p = 0.005). There was no difference in arterial wall inflammation change between early and established RA patients (SUVmax difference 0.003, 95%CI -0.11 to 0.12, p = 0.95). Change in arterial wall inflammation significantly correlated with change in serological inflammatory markers (erythrocyte sedimentation rate and C-reactive protein).

CONCLUSION

Arterial wall inflammation in RA patients is reduced by anti-inflammatory treatment and this reduction correlates with reductions of serological inflammatory markers. These results suggest that anti-inflammatory treatment of RA has favorable effects on the risk of cardiovascular events in RA patients.

Carotid atherosclerosis biomarkers in cardiovascular diseases prevention: A systematic review and bibliometric analysis

PURPOSE

While carotid atherosclerosis (CA) biomarkers are valuable surrogates for cardiovascular events, their inadequate utility is highlighted by clinical practice. We performed an interdisciplinary systematic review and bibliometric analysis to identify the knowledge gaps and offer directions for future research.

METHODS

We applied a comprehensive search strategy to construct a representative dataset of the bibliographic records of CA from 1997 to 2018. A total of 31,793 retrieved articles and 407,473 cited references were included in the analysis. The co-word network and co-citation network were derived to describe the major disciplines and topics of CA research. Milestones detected by burst analysis were reviewed to delineate the evolutionary patterns and emerging trends of research on CA biomarkers.

RESULTS

CA is a multidisciplinary field of study which could be divided into 3 communities: the primary prevention of CVD, the secondary prevention of CVD and imaging techniques to characterize carotid atherosclerosis. The evolution of a CA biomarker may go through 3 stages: the conceptualization stage, the validation stage and the reclassification stage. Measurements that include different CA plaque features, rather than separately, have shown greater value for cardiovascular risk or clinical decision-making.

CONCLUSIONS

Although wide variability exists in the evolutionary stages of CA biomarkers, combined evaluation of CA plaque imaging features shows potential value to improve risk prediction and clinical decision-making for CVD prevention.

Basic Science of PET Imaging for Inflammatory Diseases

FDG-PET/CT has recently emerged as a useful tool for the evaluation of inflammatory diseases too, in addition to that of malignant diseases. The imaging is based on active glucose utilization by inflammatory tissue. Autoradiography studies have demonstrated high FDG uptake in macrophages, granulocytes, fibroblasts, and granulation tissue. Especially, activated macrophages are responsible for the elevated FDG uptake in some types of inflammation. According to one study, after activation by lipopolysaccharide of cultured macrophages, the [¹⁴C]2DG uptake by the cells doubled, reaching the level seen in glioblastoma cells. In activated macrophages, increase in the expression of total GLUT1 and redistributions from the intracellular compartments toward the cell surface have been reported. In one rheumatoid arthritis model, following stimulation by hypoxia or TNF-α, the highest elevation of the [³H]FDG uptake was observed in the fibroblasts, followed by that in macrophages and neutrophils. As the fundamental mechanism of elevated glucose uptake in both cancer cells and inflammatory cells, activation of glucose metabolism as an adaptive response to a hypoxic environment has been reported, with transcription factor HIF-1α playing a key role. Inflammatory cells and cancer cells seem to share the same molecular mechanism of elevated glucose metabolism, lending support to the notion of usefulness of FDGPET/CT for the evaluation of inflammatory diseases, besides cancer.

Gd(III)-Gold Nanoconjugates Provide Remarkable Cell Labeling for High Field Magnetic Resonance Imaging

In vivo cell tracking is vital for understanding migrating cell populations, particularly cancer and immune cells. Magnetic resonance (MR) imaging for long-term tracking of transplanted cells in live organisms requires cells to effectively internalize Gd(III) contrast agents (CAs). Clinical Gd(III)-based CAs require high dosing concentrations and extended incubation times for cellular internalization. To combat this, we have devised a series of Gd(III)-gold nanoconjugates (Gd@AuNPs) with varied chelate structure and nanoparticle-chelate linker length, with the goal of labeling and imaging breast cancer cells. These new Gd@AuNPs demonstrate significantly enhanced labeling compared to previous Gd(III)-gold-DNA nanoconstructs. Variations in Gd(III) loading, surface packing, and cell uptake were observed among four different Gd@AuNP formulations suggesting that linker length and surface charge play an important role in cell labeling. The best performing Gd@AuNPs afforded 23.6 ± 3.6 fmol of Gd(III) per cell at an incubation concentration of 27.5 μM-this efficiency of Gd(III) payload delivery (Gd(III)/cell normalized to dose) exceeds that of previous Gd(III)-Au conjugates and most other Gd(III)-nanoparticle formulations. Further, Gd@AuNPs were well-tolerated in vivo in terms of biodistribution and clearance, and supports future cell tracking applications in whole-animal models.

Biomarkers to guide clinical therapeutics in rheumatology?

PURPOSE OF REVIEW

The use of biomarkers in rheumatology can help identify disease risk, improve diagnosis and prognosis, target therapy, assess response to treatment, and further our understanding of the underlying pathogenesis of disease. Here, we discuss the recent advances in biomarkers for rheumatic disorders, existing impediments to progress in this field, and the potential of biomarkers to enable precision medicine and thereby transform rheumatology.

RECENT FINDINGS

Although significant challenges remain, progress continues to be made in biomarker discovery and development for rheumatic diseases. The use of next-generation technologies, including large-scale sequencing, proteomic technologies, metabolomic technologies, mass cytometry, and other single-cell analysis and multianalyte analysis technologies, has yielded a slew of new candidate biomarkers. Nevertheless, these biomarkers still require rigorous validation and have yet to make their way into clinical practice and therapeutic development. This review focuses on advances in the biomarker field in the last 12 months as well as the challenges that remain.

SUMMARY

Better biomarkers, ideally mechanistic ones, are needed to guide clinical decision making in rheumatology. Although the use of next-generation techniques for biomarker discovery is making headway, it is imperative that the roadblocks in our search for new biomarkers are overcome to enable identification of biomarkers with greater diagnostic and predictive utility. Identification of biomarkers with robust diagnostic and predictive utility would enable precision medicine in rheumatology.

Combined PET/MRI: from Status Quo to Status Go. Summary Report of the Fifth International Workshop on PET/MR Imaging; February 15-19, 2016; Tübingen, Germany

This article provides a collaborative perspective of the discussions and conclusions from the fifth international workshop of combined positron emission tomorgraphy (PET)/magnetic resonance imaging (MRI) that was held in Tübingen, Germany, from February 15 to 19, 2016. Specifically, we summarise the second part of the workshop made up of invited presentations from active researchers in the field of PET/MRI and associated fields augmented by round table discussions and dialogue boards with specific topics. This year, this included practical advice as to possible approaches to moving PET/MRI into clinical routine, the use of PET/MRI in brain receptor imaging, in assessing cardiovascular diseases, cancer, infection, and inflammatory diseases. To address perceived challenges still remaining to innovatively integrate PET and MRI system technologies, a dedicated round table session brought together key representatives from industry and academia who were engaged with either the conceptualisation or early adoption of hybrid PET/MRI systems. Discussions during the workshop highlighted that emerging unique applications of PET/MRI such as the ability to provide multi-parametric quantitative and visual information which will enable not only overall disease detection but also disease characterisation would eventually be regarded as compelling arguments for the adoption of PET/MR. However, as indicated by previous workshops, evidence in favour of this observation is only growing slowly, mainly due to the ongoing inability to pool data cohorts from independent trials as well as different systems and sites. The participants emphasised that moving from status quo to status go entails the need to adopt standardised imaging procedures and the readiness to act together prospectively across multiple PET/MRI sites and vendors.