(1) Background: Following the in vivo biodistribution of platelets can contribute to a better un-derstanding of their physiological and pathological roles, and nuclear imaging methods, such as single photon emission tomography (SPECT), provide an excellent method for that. SPECT imaging needs stable labeling of the platelets with a radioisotope. (2) Methods: In this study, we report a new method to label platelets with 99mTc, the most frequently used isotope for SPECT in clinical applications. The proposed radiolabeling procedure uses a membrane-binding peptide, duramycin. (3) Results: Our results show that duramycin does not cause significant platelet activation and radiolabeling can be carried out with a procedure utilizing a simple labeling step followed by a size-exclusion chromatography-based purification step. 4) Conclusions: The performed small animal SPECT/CT in vivo imaging investigations revealed good in vivo stability of the labeling, which paves the way for further application of 99mTc-HYNIC-Duramycin in platelet imaging.

Imaging-based biomarkers have developed as an effective tool in neurology, providing vital understandings of the structural, functional, and molecular changes associated with neurological disorders. Imaging techniques such as magnetic resonance imaging (MRI), positron emission tomography (PET), single-photon emission computed tomography (SPECT), and computed tomography (CT) have been widely employed to record disease-related alterations in the brain. These techniques provide a wide range of biomarkers, such as functional connectivity patterns, volumetric measurements, molecular imaging agents, and perfusion parameters, enabling the correct identification of neurological disorders. These biomarkers have proven useful in early diagnosis, disease progression tracking, therapy response prediction, and surgical planning. This review emphasizes the various obstacles and limitations that are associated with imaging-based biomarkers. Technical constraints, standardization obstacles, ethical concerns, regulatory challenges, and cost-effectiveness concerns all offer substantial barriers to wider use. It is vital to overcome these challenges if imaging biomarkers are to be successfully integrated into routine clinical practice. Imaging technology advancements like high-resolution imaging, multimodal imaging, and artificial intelligence-based analysis hold immense promise for imaging-based biomarkers in the future. While more study and standardization are needed, their ongoing development and integration into clinical practice have the potential to revolutionize the diagnosis, treatment, and management of neurological disorders, resulting in better patient care and outcomes.

Non-invasive radionuclide imaging of human epidermal growth factor receptor type 2 (HER2) expression in breast, gastroesopha-geal and ovarian cancers may stratify patients for treatment using HER2-targeted therapeutics. Designed ankyrin repeat proteins (DARPins) are a promising type of targeting probes for radionuclide imaging. In clinical studies, the DARPin [99mTc]Tc-(HE)3-G3, labeled using a peptide-based chelator His-Glu-His-Glu-His-Glu ((HE)3), provided clear imaging of HER2 expressing breast cancer 2-4 h after injection. The goal of this study was to evaluate if the use of cysteine-containing peptide-based chelators Glu-Glu-Glu-Cys (E3C), Gly-Gly-Gly-Cys (G3C), and Gly-Gly-Gly-Ser-Cys connected via a (Gly-Gly-Gly-Ser)3-linker (designated as G3-(G3S)3C) would further improve the contrast of imaging using 99mTc-labeled derivatives of G3. The labeling of the new variants of G3 provided a radiochemical yield over 95%. Labeled G3 variants bound specifically to human HER2-expressing cancer cell lines with affinity in the range 1.9-5 nM. Biodistribution of [99mTc]Tc-G3-G3C, [99mTc]Tc-G3-(G3S)3C, and [99mTc]Tc-G3-E3C in mice was compared with the biodistribution of [99mTc]Tc-(HE)3-G3. It was found that the novel variants provide specific accumulation in HER2-expressing human xenografts and enable discrimination between tumors with high and low HER2 expression. However, [99mTc]Tc-(HE)3-G3 provided better contrast between tumors and the most frequent metastatic sites of HER2-expressing cancers and is therefore more suitable for clinical applications.

Abstract : Aims: Regeneration of myocardial tissue and improvement of myocardial activity after ischemia is one of the major fields of interest in cardiovascular research. We have developed a novel experimental rat model, and used it to examine the effect of mesenchymal stem cell transplantation (MSCT) on myocardial ischemia evaluated by single photon emission computed tomography (SPECT/CT) and immunohistochemistry. Methods and results: Forty adult female Wistar rats underwent open thoracotomy with (n=30) or without (n=10) surgical ligation of the left anterior descending coronary artery (LAD), to create myocardial ischemia, which was confirmed with ECG. Myocardial viability was evaluated via SPECT/CT at 7 days before as well as at 7 and 14 days post-surgery. At day 0, 15 animals received homologous stem cells injected at the ischemic myocardium area. SPECT/CT evaluation confirmed the reduction of functional myocardial cells of the left ventricle one week post-infarction. Regeneration of the ischemic myocardium fifteen days post infarction was recorded, only in animals submitted to stem cell transplantation. Findings were also confirmed by histology and immunohistochemical analysis, with significant higher expression of GATA4 and Nkx2,5. Conclusion: The positive effect of mesenchymal stem cells transplantation in the ischemic myocardium was recorded. The application of SPECT- CT qualitative and quantitative evaluation of myocardial function may lead to a new approach in experimentation with an anticipated significant impact in the ongoing cardiovascular laboratory research. In clinical perspective, MSCT may be beneficial when accompanied with myocardial revascularization procedures.

Background: Inflammation is an important mechanism in atherosclerosis and plaque formation. C-reactive protein (CRP) is a common inflammatory biomarker associated with the risk of coro-nary heart disease. We investigated the relationship of CRP with findings from myocardial per-fusion imaging (MPI). Methods: In this retrospective study, 102 consecutive patients (mean age 71 years, 68% males) that underwent MPI (for diagnostic reasons or quantification of myocardial ischemia) and CRP determination (upper limit: 6mg/L) within 1 month from MPI, were included. Patients had no infection or recent acute coronary syndrome. Results: the median CRP level was 4mg/L (2,10) among the study population. Patients with raised CRP had higher summed stress score (SSS) (P = 0.006) and summed rest score (SRS) (P = 0.001) and higher risk for SSS > 3 (OR 9.25, 95% CI 2.03-42.13, P = 0.001) compared to those with low CRP. The association of SSS and SRS with CRP levels was more evident in patients over 70 years (P = 0.027 and P = 0.005 respectively). No significant difference in summed difference score was shown. The two groups had no difference in other risk factors (p > 0.05 for all comparisons). Conclusion: A high level of CRP was associated with the presence and extent of stress-induced myocardial ischemia in MPI.

Uveal melanoma is the most common primary intraocular malignancy in adults characterized by insidious onset and poor prognosis strongly associated with tumor size and the presence of distant metastases, most commonly in the liver. Contrary to most tumor identification, biopsy followed by pathological exam is not recommended in ophthalmic oncology. Therefore, early and non-invasive diagnosis is essential to enhance patients’ chances for early treatment possibilities. We reviewed imaging modalities currently used in the diagnosis of uveal melanoma, i.e., fundus imaging, ultrasonography (US), optical coherence tomography (OCT), single-photon emission computed tomography (SPECT), positron emission tomography/computed tomography (PET/CT), magnetic resonance imaging (MRI), fundus fluorescein angiography (FFA), indocyanine green angiography (ICGA), fundus autofluorescence (FAF). The principle of imaging techniques was briefly explained, along with their role in the diagnostic process and a summary of their advantages and limitations. Further, the experimental data and the advancements in imaging modalities were searched. We described their innovations, showed current usage and research, and explained the possibilities of utilizing them to diagnose uveal melanoma and their potential application in personalized medicine such as theranostics.

Inflammatory Bowel Disease (IBD) is characterized by chronic remitting and relapsing inflammation of the lower gastrointestinal tract. The etiology underlying IBD remains unknown but is thought to involve a hypersensitive immune response to environmental antigen, including the microbiota. Diagnosis and monitoring of disease is heavily reliant on endoscopy, which is invasive and does not provide information regarding specific mediators. This review describes recent developments in imaging of IBD with a focus on PET and SPECT imaging of inflammatory mediators, and how this may be applied to the microbiota.

Prostate-specific membrane antigen (PSMA) is a well validated prostate cancer marker, but reported PSMA-targeted tracers derived from the Lys-urea-Glu pharmacophore including the clinically validated [99mTc]Tc-EDDA/HYNIC-iPSMA have high off-target uptake in kidneys, spleen and salivary glands. In this study, we synthesized and evaluated three novel 99mTc-labeled PSMA-targeted tracers and investigated if the tracers derived from the Lys-urea-Aad pharmacophore could have minimized uptake in off-target organs/tissues. In vitro competition binding assays showed that compared with HYNIC-iPSMA, the three novel ligands had slightly weaker PSMA binding affinity (average Ki = 3.11 vs 8.96 - 11.6 nM). Imaging and ex vivo biodistribution studies in LNCaP tumor-bearing mice showed that [99mTc]Tc-EDDA/HYNIC-iPSMA and the three novel tracers successfully visualized LNCaP tumor xenografts in SPECT images and were excreted mainly via the renal pathway. The average tumor uptake at 1 h post-injection varied from 5.40 to 18.8 %ID/g, and the tracers derived from the Lys-urea-Aad pharmacophore had much lower uptake in spleen and salivary glands. Compared with the clinical tracer [99mTc]Tc-EDDA/HYNIC-iPSMA, the Lys-urea-Aad derived [99mTc]Tc-EDDA-KL01127 had lower background uptake and superior tumor-to-background contrast ratios, and is therefore promising for clinical translation to detect prostate cancer lesions with SPECT.

Present work investigates, in photon energy domains of specific interest for medical imaging, the effect of the escape of X-ray fluorescence from the scintillator materials on the energy resolution of scintillation detector itself. Monolithic as well as pixelated crystals differently sized are considered, in the case of the NaI because it is the gold standard in the field. The volumetric ratio is introduced, as a figure of merit, taking into account, alongside the surface-to-volume ratio, the geometric shape, the elemental composition and also the mean-free-path for the given scintillator and energy. The inter-crystal XRF escape is finally suggested to be considered among the effects producing image blurring in segmented scintillatros due to the spread of events between the primary pixel and the first neighbors ones.

Inflammation involves the activation of innate immune cells and is believed to play an important role in the development and progression of both infectious and non-infectious diseases such as neurodegeneration, rheumatoid arthritis or cancer. Inflammation in the brain is marked by the upregulation of the translocator protein (TSPO) in microglia. Moreover, high TSPO levels are found, for example in macrophages during rheumatoid arthritis and in malignant tumor cells compared to its relatively low physiological expression. The same applies for cycloxygenase-2 (COX-2), which is constitutively expressed in the kidney, brain, thymus and gastrointestinal tract, but induced in microglia, macrophages and synoviocytes during inflammation. This puts TSPO and COX-2 in the spotlight as important targets for the diagnosis of inflammation. Imaging modalities, such as positron emission tomography and single-photon emission tomography, can be used to localize inflammatory processes and to track their progression over time. They could also enable to monitor the efficacy of therapy and predict its outcome. This review focuses on the current development of PET and SPECT tracers not only for the detection of neuroinflammation, but also for emerging diagnostic measures in infectious and other non-infectious diseases like rheumatic arthritis, cancer, cardiac inflammation and in lung diseases.