The application of molecular imaging to advance translational research in chronic inflammation

Development of a nomogram based on pericoronary adipose tissue histogram parameters to differentially diagnose acute coronary syndrome

PURPOSE

To develop a nomogram based on pericoronary adipose tissue (PCAT) histogram parameters to identify patients with acute coronary syndrome (ACS).

MATERIALS AND METHODS

This study retrospectively enrolled 114 and 383 eligible patients with ACS and stable coronary artery disease (CAD), respectively, and divided them into training and testing cohorts in a 7:3 ratio. A blinded radiologist obtained PCAT histogram parameters from the right coronary artery's proximal segment using fully automated software and compared clinical characteristics and PCAT histogram parameters between the two patient groups. The binary logistic regression included significant parameters (P < 0.05), and a nomogram was constructed.

RESULTS

In both the training and testing cohorts, the mean, 10th percentile, 90th percentile, median, and minimum values of PCAT were higher, and the interquartile range, skewness, and variance values of PCAT were lower in patients with ACS than in those with stable CAD (P ≤ 0.001). The mean (OR = 4.007), median (OR = 0.576), minimum (OR = 0.893), skewness (OR = 85,158.806) and variance (OR = 1.013) values of PCAT were independent risk factors for ACS and stable CAD in the training cohort. The nomogram was constructed using the five variables mentioned above with area under the curve values of 0.903 and 0.897, respectively, while the calibration and decision curves showed the nomogram's good clinical efficacy for the training and testing cohorts.

CONCLUSIONS

The constructed nomogram had good discrimination and accuracy and can be a noninvasive tool to intuitively and individually distinguish between ACS and stable CAD.

Is there an association between coronary artery inflammation and coronary atherosclerotic burden?

Background

As for the coronary artery inflammation and coronary atherosclerotic burden, which are used to assess the risk of adverse cardiac events in patients, it is unclear whether there is any certain correlation between them. Therefore, the purpose of this study was to explore the potential relationship between coronary artery inflammation and coronary atherosclerotic burden.

Methods

A total of 346 eligible patients underwent assessment of computed tomography (CT) attenuation values of pericoronary adipose tissue (PCAT) in the right coronary artery and Agatston coronary artery calcium (CAC) based on coronary CT angiography. These measurements were utilized to evaluate coronary inflammation and atherosclerotic burden, respectively. Patients with a CAC score of 0 were categorized into groups based on the presence or absence of coronary artery disease (CAD). CAC scores of 10, 100, and 400 were chosen as cutoff values to compare differences in PCAT attenuation values across different CAC scores.

Results

When comparing all CAD patients to non-CAD patients, a significantly higher PCAT attenuation was observed in CAD patients (-87.54±9.39 vs. -93.45±7.42 HU, P=0.000). The PCAT attenuation in CAD patients with a CAC score of 0 was significantly higher than that in patients with a CAC score greater than 0 and in non-CAD patients with a CAC score of 0 (-82.63±8.70 vs. -90.38±8.59 vs. -93.45±7.42 HU, P=0.000). The PCAT attenuation values did not exhibit significant differences among different CAC scores (all P>0.05); however, it was highest in CAD patients with a CAC score of 0 (P<0.05). Body mass index, hyperlipidemia, hypertension, and PCAT attenuation were identified as independent risk factors in both CAD patients with a CAC score of 0 and patients with a CAC score greater than 0 (all P<0.05).

Conclusions

The results of this study suggest that a direct relationship between coronary inflammation and coronary atherosclerotic burden is not evident. Nonetheless, it is noteworthy that coronary inflammation was most pronounced in CAD patients with a CAC score of 0, while CAC score did not demonstrate an association with inflammation.

PET/MR imaging of inflammation in atherosclerosis

Myocardial infarction, stroke, mental disorders, neurodegenerative processes, autoimmune diseases, cancer and the human immunodeficiency virus impact the haematopoietic system, which through immunity and inflammation may aggravate pre-existing atherosclerosis. The interplay between the haematopoietic system and its modulation of atherosclerosis has been studied by imaging the cardiovascular system and the activation of haematopoietic organs via scanners integrating positron emission tomography and resonance imaging (PET/MRI). In this Perspective, we review the applicability of integrated whole-body PET/MRI for the study of immune-mediated phenomena associated with haematopoietic activity and cardiovascular disease, and discuss the translational opportunities and challenges of the technology.

Updates in the Impact of Chronic Systemic Inflammation on Vascular Inflammation by Positron Emission Tomography (PET)

PURPOSE OF REVIEW

In this review, we focus on the clinical and epidemiological studies pertaining to systemic and vascular inflammation by positron emission tomography (PET) in patients with chronic inflammatory conditions such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), human immunodeficiency virus (HIV), and psoriasis to highlight the importance of chronic systemic inflammation on vascular inflammation by PET in these disease states.

RECENT FINDINGS

Recent clinical and translation advancements have demonstrated the durable relationship between chronic systemic inflammation and cardiovascular disease (CVD). In chronic inflammatory states, this relationship is robustly evident in the form of increased vascular inflammation, yet traditional risk estimates often underestimate the subclinical cardiovascular risk conferred by chronic inflammation. PET has emerged as a novel, non-invasive imaging modality capable of both quantifying the degree of systemic and vascular inflammation and detecting residual inflammation prior to cardiovascular events. We begin by demonstrating the role of inflammation in the pathogenesis of atherosclerosis, discussing how PET has been utilized to measure systemic and vascular inflammation and their effect on subclinical atherosclerosis, and finally reviewing recent applications of PET in constructing improved risk stratification for patients at high risk for stroke and CVD.

Advances in Radiopharmaceutical Sciences for Vascular Inflammation Imaging: Focus on Clinical Applications

Biomedical imaging technologies offer identification of several anatomic and molecular features of disease pathogenesis. Molecular imaging techniques to assess cellular processes in vivo have been useful in advancing our understanding of several vascular inflammatory diseases. For the non-invasive molecular imaging of vascular inflammation, nuclear medicine constitutes one of the best imaging modalities, thanks to its high sensitivity for the detection of probes in tissues. 2-[¹⁸F]fluoro-2-deoxy-d-glucose ([¹⁸F]FDG) is currently the most widely used radiopharmaceutical for molecular imaging of vascular inflammatory diseases such as atherosclerosis and large-vessel vasculitis. The combination of [¹⁸F]FDG and positron emission tomography (PET) imaging has become a powerful tool to identify and monitor non-invasively inflammatory activities over time but suffers from several limitations including a lack of specificity and avid background in different localizations. The use of novel radiotracers may help to better understand the underlying pathophysiological processes and overcome some limitations of [¹⁸F]FDG PET for the imaging of vascular inflammation. This review examines how [¹⁸F]FDG PET has given us deeper insight into the role of inflammation in different vascular pathologies progression and discusses perspectives for alternative radiopharmaceuticals that could provide a more specific and simple identification of pathologies where vascular inflammation is implicated. Use of these novel PET tracers could lead to a better understanding of underlying disease mechanisms and help inform the identification and stratification of patients for newly emerging immune-modulatory therapies. Future research is needed to realize the true clinical translational value of PET imaging in vascular inflammatory diseases.

Biomarkers of subclinical atherosclerosis in patients with psoriasis

Psoriasis is linked with increased risk of cardiovascular disease (CVD) that is underestimated by traditional risk stratification. We conducted a large-scale plasma proteomic analysis by use of a proximity extension assay in 85 patients with a history of moderate-to-severe psoriasis with or without established atherosclerotic CVD. Differentially expressed proteins associated with CVD were correlated with subclinical atherosclerotic markers including vascular inflammation determined by 18F-fluorodeoxyglucose positron emission tomography/computed tomography, carotid intima-media thickness (CIMT), carotid artery plaques, and coronary artery calcium score (CCS) in the patients without CVD and statin treatment. We also examined the association between the neutrophil-to-lymphocyte ratio (NLR) and subclinical atherosclerosis. In unadjusted analyses, growth differentiation factor-15 (GDF-15) levels and NLR were increased, while tumor necrosis factor (TNF)-related activation-inducing ligand (TRANCE) and TNF-related apoptosis-induced ligand (TRAIL) levels were decreased in patients with established CVD compared to those without CVD. Among patients with psoriasis without CVD and statin treatment, GDF-15 levels were negatively associated with vascular inflammation in the ascending aorta and entire aorta, and positively associated with CIMT and CCS. NLR was positively associated with vascular inflammation in the carotid arteries. Our data suggest that circulating GDF-15 levels and NLR might serve as biomarkers of subclinical atherosclerosis in patients with psoriasis.

Association between Vascular Inflammation and Inflammation in Adipose Tissue, Spleen, and Bone Marrow in Patients with Psoriasis

Psoriasis is associated with atherosclerotic cardiovascular disease (CVD) with significant overlap of inflammatory pathways. A link between vascular inflammation and inflammation in multiple adipose tissue types, spleen, and bone marrow may exist. Therefore, we investigated these associations using ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG-PET/CT) in patients with psoriasis (n = 83) where half had established CVD. Carotid ultrasound imaging was also performed. Inflammation was measured by FDG uptake in the aorta, visceral- (VAT), subcutaneous- (SAT), and pericardial (PAT) adipose tissues, and spleen and bone marrow, respectively. Vascular inflammation was associated with FDG uptakes in all adipose tissues, including VAT (β = 0.26; p < 0.001), SAT (β = 0.28; p < 0.001), PAT (β = 0.24; p < 0.001), spleen (β = 1.35; p = 0.001), and bone marrow (β = 1.14; p < 0.001). Adjustments for age, sex, body mass index, and high sensitivity C-reactive protein did not change the results. These associations were generally preserved in the patients without prior CVD. No associations were observed between vascular inflammation and carotid intima-media thickness or presence of carotid plaques, respectively. The results suggest an inflammatory link between vascular and adipose tissues, spleen, and bone marrow in patients with psoriasis.