Imaging Inflammation in Atherosclerosis with CXCR4-Directed [68Ga]PentixaFor PET/MRI-Compared with [18F]FDG PET/MRI

Expanding horizons in theragnostics: from oncology to multidisciplinary applications

Theragnostics is the integration of treatment and diagnosis, involving a drug or technology that combines diagnostic imaging with targeted therapy. This approach utilizes imaging to identify specific biological targets, which are then used to deliver therapeutic effects for the benefit of patients. The effectiveness and potential of theragnostics in improving patient outcomes are supported by significant clinical trials and technological innovations. Theragnostics has demonstrated its capacity to deliver targeted and real-time interventions, making it adaptable to diverse clinical domains. Its applications range from visualizing and eradicating tumors to addressing complex neurological disorders and cardiovascular diseases. The integration of nanomaterials and advancements in molecular biology further enhance the capabilities of theragnostics, promising a future where treatments are highly personalized, and diseases are understood and managed at a molecular level previously unattainable. Our comprehensive overview focuses on the current advancements in theragnostics applications across different disease domains. We highlight the role of molecular imaging technologies, such as PET/CT scans, in early diagnosis and treatment. Additionally, we explore the potential of chemokines as molecular imaging targets in systemic inflammatory diseases and central nervous system pathologies. In conclusion, the progression of theragnostics represents a transformative phase in medical practice, providing new avenues for precise treatment and improved patient outcomes. Its multidisciplinary nature and continuous innovation have the potential to profoundly impact the future of medical research and clinical practice, as well as revolutionizing the treatment and management of a wide array of diseases.

Emerging PET radiotracers for vascular imaging

Imaging plays an important role in the clinical management of patients with large-vessel vasculitis (LVV), both to confirm the diagnosis at the time of initial presentation and to identify disease relapses in individuals with established disease. The big advantage of PET imaging over other non-invasive imaging modalities is the ability to employ targeted radionuclide probes to localize and track cellular pathways, providing in vivo assessments of disease activity. While 18F-fluorodeoxyglucose (FDG) has good diagnostic accuracy for LVV, this tracer is taken up by all glucose metabolizing cells in the vessel wall and so non-specific arterial uptake that is often unrelated to inflammatory disease activity can occur in patients despite a good clinical response to treatment. Advances in PET imaging technology and methods such as delayed imaging protocols and quantitative parametric imaging have the potential to improve the diagnostic accuracy of 18F-FDG in LVV. However, there is nevertheless a real clinical need for new PET tracers that target specific immune cells and inflammatory processes to inform about underlying disease pathology and guide individualized treatments for LVV. Many emerging PET tracers developed initially for oncology or atherosclerosis imaging could provide useful measures of disease activity in LVV, including tracers targeted to receptors on monocytes/macrophages, T and B lymphocytes and other inflammatory cells implicated in the pathogenesis of the disease. This focused review will discuss several of the most promising emerging PET radionuclide tracers for imaging vascular inflammation.

C-X-C motif chemokine receptor 4-directed PET signal in the arterial tree is not consistently linked to calcified plaque burden and cardiovascular risk

Purpose: To establish the extent, distribution and frequency of in-vivo vessel wall [68Ga]Ga-PentixaFor uptake and to determine its relationship with calcified atherosclerotic plaque burden (CAP) and cardiovascular risk factors (CVRF). Methods: 65 oncological patients undergoing [68Ga]Ga-PentixaFor PET/CT were assessed. Radiotracer uptake (target-to-background ratio [TBR]) and CAP burden (including number of CAP sites, calcification circumference and thickness) in seven major vessel segments per patient were determined. We then investigated associations of vessel wall uptake with CAP burden, cardiovascular risk (CVRF and European Society of Cardiology [ESC] SCORE2/SCORE2-OP risk chart) and image noise (determined by coefficient of variation [CoV] from unaffected liver parenchyma). Results: We identified 1292 sites of high focal [68Ga]Ga-PentixaFor uptake (PentixaFor+ sites) in the vessel wall in 65/65 (100%) patients, with concomitant calcification in 385/1292 (29.8%) sites. There were no significant associations between vessel wall uptake and CAP burden (number of PentixaFor+ sites: r ≤ 0.18, P ≥ 0.14; PentixaFor+ TBR: r ≤ 0.08, P ≥ 0.54). The number of PentixaFor+ sites showed a moderate correlation with cardiovascular risk (ESC SCORE2/SCORE2-OP, r = 0.30; number of CVRF, r = 0.26; P = 0.04, respectively), but failed to reach significance for PentixaFor+ TBR (r ≤ 0.18, P ≥ 0.22). In univariable regression analysis, body mass index (odds ratio [OR] 1.08, 95%-confidence interval [CI] 1.02-1.14) and CoV (OR, 1.07; CI, 1.05-1.10) were linked to TBR and the number of PentixaFor+ sites (P < 0.01, respectively), while injected activity was only associated with the latter imaging parameter (OR, 0.99; CI, 0.98-1.00; P = 0.04). In multivariable regression, injected activity (OR, 1.00; CI, 0.99-1.00) and CoV (OR, 1.06; CI, 1.06-1.07) remained significantly associated with the number of PentixaFor+ sites (P < 0.01, respectively). CoV, however, was the only parameter significantly linked to PentixaFor+ TBR on multivariable analysis (OR, 1.02; CI, 1.01-1.03; P < 0.01). Conclusion: On a visual and quantitative level, high focal [68Ga]Ga-PentixaFor uptake in the arterial tree was not consistently linked to vessel wall calcification or cardiovascular risk. Image noise, however, may account for a substantial portion of apparent vessel wall uptake.

Update on Positron Emission Tomography/Magnetic Resonance Imaging: Cancer and Inflammation Imaging in the Clinic

Hybrid PET/MRI is highly valuable, having made significant strides in overcoming technical challenges and offering unique advantages such as reduced radiation, precise data coregistration, and motion correction. Growing evidence highlights the value of PET/MRI in broad clinical aspects, including inflammatory and oncological imaging in adults, pregnant women, and pediatrics, potentially surpassing PET/CT. This newly integrated solution may be preferred over PET/CT in many clinical conditions. However, further technological advancements are required to facilitate its broader adoption as a routine diagnostic modality.

Imaging findings and clinical relevance of 68Ga-Pentixafor PET in atherosclerosis: a systematic review

OBJECTIVE

We aimed to perform a qualitative synthesis of evidence on the role of 68Ga-Pentixafor PET in atherosclerosis.

METHODS

A systematic search of the PubMed and Embase databases for studies reporting the evaluation of atherosclerotic lesions by 68Ga-Pentixafor PET was performed with a search time frame from database creation to 2022-12-26. The diagnostic test evaluation tool QUADAS-2 was used to evaluate the quality of the included literature and to perform descriptive analyses of relevant outcome indicators.

RESULTS

A total of 6 studies with 280 patients were included. One study reported only imaging outcome metrics, while the other five studies reported imaging outcome metrics and clinical correlation metrics. For imaging outcomes, three studies reported imaging results for 68Ga-Pentixafor PET only, and the other three studies reported imaging results for comparative analysis of 68Ga-Pentixafor PET with 18F-FDG PET. For clinical correlation, three studies reported the correlation between tracer uptake and cardiovascular risk factors, one study reported the correlation between tracer uptake and plaque calcification, and one study reported the correlation between all three: tracer uptake, cardiovascular risk factors, and plaque calcification.

CONCLUSION

68Ga-Pentixafor PET has a good imaging effect on atherosclerotic lesions, and it is a promising imaging modality that may replace 18F-FDG PET for atherosclerosis imaging in the future. In patients with atherosclerosis, there is a clear clinical correlation between cardiovascular risk factors, tracer uptake, and plaque calcification.

Implant Imaging: Perspectives of Nuclear Imaging in Implant, Biomaterial, and Stem Cell Research

Until now, very few efforts have been made to specifically trace, monitor, and visualize implantations, artificial organs, and bioengineered scaffolds for tissue engineering in vivo. While mainly X-Ray, CT, and MRI methods have been used for this purpose, the applications of more sensitive, quantitative, specific, radiotracer-based nuclear imaging techniques remain a challenge. As the need for biomaterials increases, so does the need for research tools to evaluate host responses. PET (positron emission tomography) and SPECT (single photon emission computer tomography) techniques are promising tools for the clinical translation of such regenerative medicine and tissue engineering efforts. These tracer-based methods offer unique and inevitable support, providing specific, quantitative, visual, non-invasive feedback on implanted biomaterials, devices, or transplanted cells. PET and SPECT can improve and accelerate these studies through biocompatibility, inertivity, and immune-response evaluations over long investigational periods at high sensitivities with low limits of detection. The wide range of radiopharmaceuticals, the newly developed specific bacteria, and the inflammation of specific or fibrosis-specific tracers as well as labeled individual nanomaterials can represent new, valuable tools for implant research. This review aims to summarize the opportunities of nuclear-imaging-supported implant research, including bone, fibrosis, bacteria, nanoparticle, and cell imaging, as well as the latest cutting-edge pretargeting methods.

Emerging Nuclear Medicine Imaging of Atherosclerotic Plaque Formation

Atherosclerosis is a chronic widespread cardiovascular disease and a major predisposing factor for cardiovascular events, among which there are myocardial infarction and ischemic stroke. Atherosclerotic plaque formation is a process that involves different mechanisms, of which inflammation is the most common. Plenty of radiopharmaceuticals were developed to elucidate the process of plaque formation at different stages, some of which were highly specific for atherosclerotic plaque. This review summarizes the current nuclear medicine imaging landscape of preclinical and small-scale clinical studies of these specific RPs, which are not as widespread as labeled FDG, sodium fluoride, and choline. These include oxidation-specific epitope imaging, macrophage, and other cell receptors visualization, neoangiogenesis, and macrophage death imaging. It is shown that specific radiopharmaceuticals have strength in pathophysiologically sound imaging of the atherosclerotic plaques at different stages, but this also may induce problems with the signal registration for low-volume plaques in the vascular wall.