Molecular Imaging最新文献

Immunologic thrombocytopenic purpura (ITP) is a condition that affects four to 18 per 100 000 children every year. In most cases, spontaneous remission occurs, but splenectomy may be proposed. Exploring the site of platelet sequestration can help to better predict potential poor responders to splenectomy, but ¹¹¹In-radiolabeled platelet scintigraphy (IPS) can be difficult to perform in children with very few platelets. A 12-year-old boy suffering from refractory ITP was referred for evaluation of platelet survival and sequestration and consideration of splenectomy. His platelet count consistently remained below 10 000/mm³. An exceptional procedure was set up to use homologous platelets to perform the IPS. Splenectomy was ruled out based on the results of ¹¹¹In-radiolabeled homologous platelet scintigraphy. The attending pediatrician intensified medical treatments, resulting in a significant improvement in platelet count. This increase in platelet levels allowed for ¹¹¹In-radiolabeled autologous platelet scintigraphy, which confirmed the absence of splenic sequestration. This allowed us to reject splenectomy in this child. Homologous IPS could help clinicians to choose splenectomy as a treatment option for ITP in children with a very low platelet count, and its use should be promoted after failed thrombopoietin receptor agonist (TPO-RA) treatment. More systematic studies are needed to confirm the predictive response to splenectomy of homologous IPS.

Objective: 2-Deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) is widely used for noninvasive imaging of atherosclerosis. However, knowledge about metabolic processes underlying [¹⁸F]FDG uptake is mostly derived from in vitro cell culture studies, which cannot recapitulate the complexities of the plaque microenvironment. Here, we sought to address this gap by in situ mapping of the activity of selected major dehydrogenases involved in glucose metabolism in atherosclerotic plaques.

Methods: In situ activity of lactate dehydrogenase (LDH), glucose-6-phosphate dehydrogenase (G6PD), succinate dehydrogenase (SDH), and isocitrate dehydrogenase (IDH) was assessed in plaques from murine aortic root and brachiocephalic arteries and human carotid arteries. High-resolution 2-deoxy-D-[1,2-³H]glucose ([³H]2-deoxyglucose) autoradiography of murine brachiocephalic plaques was performed.

Results: LDH activity was heterogeneous throughout the plaques with the highest activity in medial smooth muscle cells (SMCs). G6PD activity was mostly confined to the medial layer and to a lesser extent to SMCs along the fibrous cap. SDH and IDH activities were minimal in plaques. Plaque regions with increased [³H]2-deoxyglucose uptake were associated with a modestly higher LDH, but not G6PD, activity.

Conclusions: Our study reveals a novel aspect of the metabolic heterogeneity of the atherosclerotic plaques, enhancing our understanding of the complex immunometabolic biology that underlies [¹⁸F]FDG uptake in atherosclerosis.

Background: Labeled antibodies are excellent imaging agents in oncology to non-invasively visualize cancer-related antigens expression levels. However, tumor tracer uptake (TTU) of specific antibodies in-vivo may be inferior to non-specific IgG in some cases.

Objectives: To explore factors affecting labeled antibody visualization by PD-L1 specific and non-specific imaging of nude mouse tumors.

Methods: TTU was observed in RKO model on Cerenkov luminescence (CL) and near-infrared fluorescence (NIRF) imaging of radionuclide ¹³¹I or NIRF dyes labeled Atezolizumab and IgG. A mixture of NIRF dyes labeled Atezolizumab and ¹³¹I-labeled IgG was injected, and TTU was observed in the RKO and HCT8 model by NIRF/CL dual-modality in-situ imaging. TTU were observed by ¹³¹I-labeled Atezolizumab and IgG in-vitro distribution.

Results: Labeled IgG concentrated more in tumors than Atezolizumab. NIRF/CL imaging in 24 to 168 h showed that TTU gradually decreased over time, which decreased more slowly on CL imaging compared to NIRF imaging. The distribution data in-vitro showed that TTU of ¹³¹I-labeled IgG was higher than that of ¹³¹I-labeled Atezolizumab at any time point.

Conclusion: Non-specific IgG may not be suitable as a control for Atezolizumab in comparing tumor PD-L1 expression in nude mice via labeled antibody optical imaging under certain circumstances.

Objective: To investigate the performance of diffusion-tensor imaging (DTI) and hydrogen proton magnetic resonance spectroscopy (¹H-MRS) parameters in predicting the immunohistochemistry (IHC) biomarkers of glioma.

Methods: Patients with glioma confirmed by pathology from March 2015 to September 2019 were analyzed, the preoperative DTI and ¹H-MRS images were collected, apparent diffusion coefficient (ADC) and fractional anisotropy (FA), in the lesion area were measured, the relative values relative ADC (rADC) and relative FA (rFA) were obtained by the ratio of them in the lesion area to the contralateral normal area. The peak of each metabolite in the lesion area of ¹H-MRS image: N-acetylaspartate (NAA), choline (Cho), and creatine (Cr), and metabolite ratio: NAA/Cho, NAA/(Cho + Cr) were selected and calculated. The preoperative IHC data were collected including CD34, Ki-67, p53, S-100, syn, vimentin, NeuN, Nestin, and glial fibrillary acidic protein.

Results: One predicting parameter of DTI was screened, the rADC of the Ki-67 positive group was lower than that of the negative group. Two parameters of ¹H-MRS were found to have significant reference values for glioma grades, the NAA and Cr decreased as the grade of glioma increased, moreover, Ki-67 Li was negatively correlated with NAA and Cr.

Conclusion: NAA and Cr have potential application value in predicting glioma grades and tumor proliferation activity. Only rADC has predictive value for Ki-67 expression among DTI parameters.

Chimeric antigen receptor (CAR)-T cell-based immunotherapy has emerged as a path-breaking strategy for certain hematological malignancies. Assessment of the response to CAR-T therapy using quantitative imaging techniques such as positron emission tomography/computed tomography (PET/CT) has been broadly investigated. However, the definitive role of PET/CT in CAR-T therapy remains to be established. [¹⁸F]FDG PET/CT has demonstrated high sensitivity and specificity for differentiating patients with a partial and complete response after CAR-T therapy in lymphoma. The early therapeutic response and immune-related adverse effects such as cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome can also be detected on [¹⁸F]FDG PET images. In otherwise asymptomatic lymphoma patients with partial response following CAR-T therapy, the only positive findings could be abnormal PET/CT results. In multiple myeloma, a negative [¹⁸F]FDG PET/CT after receiving B-cell maturation antigen-directed CAR-T therapy has been associated with a favorable prognosis. In leukemia, [¹⁸F]FDG PET/CT can detect extramedullary metastases and treatment responses after therapy. Hence, PET/CT is a valuable imaging tool for patients undergoing CAR-T therapy for pretreatment evaluation, monitoring treatment response, assessing safety, and guiding therapeutic strategies. Developing guidelines with standardized cutoff values for various PET parameters and tumor cell-specific tracers may improve the efficacy and safety of CAR-T therapy.

This meeting report summarizes a consultants meeting that was held at International Atomic Energy Agency Headquarters, Vienna, in July 2022 to provide an update on the development of multimodality imaging by combining nuclear medicine imaging agents with other nonradioactive molecular probes and/or biomedical imaging techniques.

[¹⁸F]SynVesT-1 is a PET radiopharmaceutical that binds to the synaptic vesicle protein 2A (SV2A) and serves as a biomarker of synaptic density with widespread clinical research applications in psychiatry and neurodegeneration. The initial goal of this study was to concurrently conduct PET imaging studies with [¹⁸F]SynVesT-1 at our laboratories. However, the data in the first two human PET studies had anomalous biodistribution despite the injected product meeting all specifications during the prerelease quality control protocols. Further investigation, including imaging in rats as well as proton and carbon 2D-NMR spectroscopic studies, led to the discovery that a derivative of the precursor had been received from the manufacturer. Hence, we report our investigation and the first-in-human study of [¹⁸F]SDM-4MP3, a structural variant of [¹⁸F]SynVesT-1, which does not have the requisite characteristics as a PET radiopharmaceutical for imaging SV2A in the central nervous system.

Amyotrophic lateral sclerosis (ALS) is a disease leading to progressive motor degeneration and ultimately death. It is a complex disease that can take a significantly long time to be diagnosed, as other similar pathological conditions must be ruled out for a definite diagnosis of ALS. Noninvasive imaging of ALS has shed light on disease pathology and altered biochemistry in the ALS brain. Other than magnetic resonance imaging (MRI), two types of functional imaging, positron emission tomography (PET) and single photon emission computed tomography (SPECT), have provided valuable data about what happens in the brain of ALS patients compared to healthy controls. PET imaging has revealed a specific pattern of brain metabolism through [¹⁸F]FDG, while other radiotracers have uncovered neuroinflammation, changes in neuronal density, and protein aggregation. SPECT imaging has shown a general decrease in regional cerebral blood flow (rCBF) in ALS patients. This educational review summarizes the current state of ALS imaging with various PET and SPECT radiopharmaceuticals to better understand the pathophysiology of ALS.