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Neuroinflammation and immunoregulation in glioblastoma and brain metastases: Recent developments in imaging approaches.
Roesler, R, Dini, SA, Isolan, GR
Clinical and experimental immunology. 2021;(3):314-324
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Abstract
Brain tumors and brain metastases induce changes in brain tissue remodeling that lead to immunosuppression and trigger an inflammatory response within the tumor microenvironment. These immune and inflammatory changes can influence invasion and metastasis. Other neuroinflammatory and necrotic lesions may occur in patients with brain cancer or brain metastases as sequelae from treatment with radiotherapy. Glioblastoma (GBM) is the most aggressive primary malignant brain cancer in adults. Imaging methods such as positron emission tomography (PET) and different magnetic resonance imaging (MRI) techniques are highly valuable for the diagnosis and therapeutic evaluation of GBM and other malignant brain tumors. However, differentiating between tumor tissue and inflamed brain tissue with imaging protocols remains a challenge. Here, we review recent advances in imaging methods that have helped to improve the specificity of primary tumor diagnosis versus evaluation of inflamed and necrotic brain lesions. We also comment on advances in differentiating metastasis from neuroinflammation processes. Recent advances include the radiosynthesis of 18 F-FIMP, an L-type amino acid transporter 1 (LAT1)-specific PET probe that allows clearer differentiation between tumor tissue and inflammation compared to previous probes, and the combination of different advanced imaging protocols with the inclusion of radiomics and machine learning algorithms.
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[Proposal for a Guideline of Risk Reduction and Sensitivity Optimization in Imaging Tests for People with Diabetes].
Donato, S, Simões, H, Donato, P
Acta medica portuguesa. 2021;(5):388-394
Abstract
Diabetes is a very common chronic disease in the Portuguese population, with an estimated prevalence of 13.6% in the adults. Doubts often arise regarding the best preparation and the risks associated with doing imaging tests in these patients. In this article we intend to review the main precautions in imaging tests in people with diabetes and to suggest a guideline to reduce the risks and optimize the sensitivity of these tests in this population. The main topics addressed in this article are the need to suspend metformin after the administration of endovascular iodinated contrast due to the risk of lactic acidosis, the precautions in insulin-treated patients or those taking medicines with a higher risk of hypoglycemia when performing imaging tests that require fasting, and the influence of hyperglycemia and of anti-diabetic therapy on the sensitivity of PET-FDG. With this review and the presentation of a guideline, we intend to demystify and simplify the management of individuals with diabetes who are undergoing imaging tests.
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Advanced imaging techniques for neuro-oncologic tumor diagnosis, with an emphasis on PET-MRI imaging of malignant brain tumors.
Overcast, WB, Davis, KM, Ho, CY, Hutchins, GD, Green, MA, Graner, BD, Veronesi, MC
Current oncology reports. 2021;(3):34
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Abstract
PURPOSE OF REVIEW This review will explore the latest in advanced imaging techniques, with a focus on the complementary nature of multiparametric, multimodality imaging using magnetic resonance imaging (MRI) and positron emission tomography (PET). RECENT FINDINGS Advanced MRI techniques including perfusion-weighted imaging (PWI), MR spectroscopy (MRS), diffusion-weighted imaging (DWI), and MR chemical exchange saturation transfer (CEST) offer significant advantages over conventional MR imaging when evaluating tumor extent, predicting grade, and assessing treatment response. PET performed in addition to advanced MRI provides complementary information regarding tumor metabolic properties, particularly when performed simultaneously. 18F-fluoroethyltyrosine (FET) PET improves the specificity of tumor diagnosis and evaluation of post-treatment changes. Incorporation of radiogenomics and machine learning methods further improve advanced imaging. The complementary nature of combining advanced imaging techniques across modalities for brain tumor imaging and incorporating technologies such as radiogenomics has the potential to reshape the landscape in neuro-oncology.
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Value of 18F-FDG-PET to predict PD-L1 expression and outcomes of PD-1 inhibition therapy in human cancers.
Kaira, K, Kuji, I, Kagamu, H
Cancer imaging : the official publication of the International Cancer Imaging Society. 2021;(1):11
Abstract
Anti-programmed cell death-1 (PD-1)/programmed death ligand-1 (PD-L1) antibodies are administered in varied human cancer types. The expression of PD-L1 within tumor cells has been identified as a predictive marker, although assessing its expression has benefitted only patients with non-small cell lung cancer (NSCLC) or head and neck cancer. Whereas, more than 75% of the patients with NSCLC showing partial response to PD-1 blockade therapy experienced long-term survival for more than 5-years Thus, identifying the responders to PD-1 blockade at early phase after its initiation is of clinical importance. The 2-deoxy-2-[fluorine-18] fluoro-D-glucose (18F-FDG) on positron emission tomography (PET) can evaluate any tumor shrinkage by assessing the metabolic tumor volume at an earlier phase than conventional modalities such as computed tomography (CT). While several reports describe the correlation of PD-L1 expression with 18F-FDG uptake rate in the tumor cells, it remains to be delineated whether this rate determined by the glucose metabolism and hypoxia is associated with the status of immune microenvironment, including the expression of PD-L1. Moreover, details of the relationship between expression of PD-L1 and 18F-FDG uptake is still unclear. Therefore, we reviewed the clinical significance of 18F-FDG uptake on PET as a predictor of the efficacy of PD-1 blockade therapy, by correlating with the expression of PD-L1, in patients with several neoplasms.
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Ramatroban-Based Analogues Containing Fluorine Group as Potential 18F-Labeled Positron Emission Tomography (PET) G-Protein Coupled Receptor 44 (GPR44) Tracers.
Huang, LA, Huang, KX, Tu, J, Kandeel, F, Li, J
Molecules (Basel, Switzerland). 2021;(5)
Abstract
Diabetes remains one of the fastest growing chronic diseases and is a leading source of morbidity and accelerated mortality in the world. Loss of beta cell mass (BCM) and decreased sensitivity to insulin underlie diabetes pathogenesis. Yet, the ability to safely and directly assess BCM in individuals with diabetes does not exist. Measures such as blood glucose provide only a crude indirect picture of beta cell health. PET imaging could, in theory, allow for safe, direct, and precise characterization of BCM. However, identification of beta cell-specific radiolabeled tracers remains elusive. G-protein coupled receptor 44 (GPR44) is a transmembrane protein that was characterized in 2012 as highly beta cell-specific within the insulin-positive islets of Langerhans. Accordingly, radiolabeling of existing GPR44 antagonists could be a viable method to accelerate PET tracer development. The present study aims to evaluate and summarize published analogues of the GPR44 antagonist ramatroban to develop 18F-labeled PET tracers for BCM analysis. The 77 corresponding ramatroban analogues containing a fluorine nuclide were characterized for properties including binding affinity, selectivity, and pharmacokinetic and metabolic profile, and 32 compounds with favorable properties were identified. This review illustrates the potential of GPR44 analogues for the development of PET tracers.
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18F-Sodium Fluoride PET: History, Technical Feasibility, Mechanism of Action, Normal Biodistribution, and Diagnostic Performance in Bone Metastasis Detection Compared with Other Imaging Modalities.
Ahuja, K, Sotoudeh, H, Galgano, SJ, Singh, R, Gupta, N, Gaddamanugu, S, Choudhary, G
Journal of nuclear medicine technology. 2020;(1):9-16
Abstract
The skeleton is the third most common site for metastasis overall, after the lungs and liver. Accurate diagnosis of osseous metastasis is critical for initial staging, treatment planning, restaging, treatment monitoring, and survival prediction. Currently, 99mTc-methylene diphosphonate whole-body scanning is the cornerstone of imaging to detect osseous metastasis. Although 18F-sodium fluoride (18F-NaF) was one of the oldest medical tracers for this purpose, it was replaced by other tracers because of their better physical properties, until recently. Continued development of PET scanners has opened a new era for 18F-NaF, and given its higher sensitivity, there have been increasing applications in imaging. In this review, we will discuss the history, technical aspects, radiobiology, and biodistribution of this tracer. Finally, we compare the accuracy of 18F-NaF PET with other conventional imaging methods for detection of osseous metastasis.
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Aortic valve stenosis-multimodality assessment with PET/CT and PET/MRI.
Tzolos, E, Andrews, JP, Dweck, MR
The British journal of radiology. 2020;(1113):20190688
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Abstract
Aortic valve disease is the most common form of heart valve disease in developed countries and a growing healthcare burden with an ageing population. Transthoracic and transoesophageal echocardiography remains central to the diagnosis and surveillance of patients with aortic stenosis, providing gold standard assessments of valve haemodynamics and myocardial performance. However, other multimodality imaging techniques are being explored for the assessment of aortic stenosis, including combined PET/CT and PET/MR. Both approaches provide unique information with respect to disease activity in the valve alongside more conventional anatomic assessments of the valve and myocardium in this condition. This review investigates the emerging use of PET/CT and PET/MR to assess patients with aortic stenosis, examining how the complementary data provided by each modality may be used for research applications and potentially in future clinical practice.
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Vulnerable plaque imaging using 18F-sodium fluoride positron emission tomography.
Kwiecinski, J, Slomka, PJ, Dweck, MR, Newby, DE, Berman, DS
The British journal of radiology. 2020;(1113):20190797
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Abstract
Positron emission tomography (PET) with 18F-sodium fluoride (18F-NaF) has emerged as a promising non-invasive imaging modality to identify high-risk and ruptured atherosclerotic plaques. By visualizing microcalcification, 18F-NaF PET holds clinical promise in refining how we evaluate coronary artery disease, shifting our focus from assessing disease burden to atherosclerosis activity. In this review, we provide an overview of studies that have utilized 18F-NaF PET for imaging atherosclerosis. We discuss the associations between traditional coronary artery disease measures (risk factors) and 18F-NaF plaque activity. We also present the data on the histological validation as well as show how 18F-NaF uptake is associated with plaque morphology on intravascular and CT imaging. Finally, we discuss the technical challenges associated with 18F-NaF coronary PET highlighting recent advances in this area.
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Current Landscape and Emerging Fields of PET Imaging in Patients with Brain Tumors.
Werner, JM, Lohmann, P, Fink, GR, Langen, KJ, Galldiks, N
Molecules (Basel, Switzerland). 2020;(6)
Abstract
The number of positron-emission tomography (PET) tracers used to evaluate patients with brain tumors has increased substantially over the last years. For the management of patients with brain tumors, the most important indications are the delineation of tumor extent (e.g., for planning of resection or radiotherapy), the assessment of treatment response to systemic treatment options such as alkylating chemotherapy, and the differentiation of treatment-related changes (e.g., pseudoprogression or radiation necrosis) from tumor progression. Furthermore, newer PET imaging approaches aim to address the need for noninvasive assessment of tumoral immune cell infiltration and response to immunotherapies (e.g., T-cell imaging). This review summarizes the clinical value of the landscape of tracers that have been used in recent years for the above-mentioned indications and also provides an overview of promising newer tracers for this group of patients.
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Selectivity of probes for PET imaging of dopamine D3 receptors.
Doot, RK, Dubroff, JG, Labban, KJ, Mach, RH
Neuroscience letters. 2019;:18-25
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Abstract
Dopamine D3 receptors have key roles in behavioral reward, addiction, Parkinson's disease, and schizophrenia, and there is interest in studying their role in these disorders using PET. However, current PET radiotracers for studying D3 receptors in humans all bind to both D2 and D3 due to similarities between the two receptors. Selective D2 and D3 radioligands would aid investigation of the differences between D2 and D3 circuitry in the central nervous system. While there are currently in vitro measures of ligand D3/D2 selectivity, there is a need for an in vivo PET measure of D3/D2 selectivity. This review discusses current PET imaging of dopamine D2/D3 receptors and proposes methodology for quantitating in vivo selectivity of probes for PET imaging of dopamine D3 receptors.