(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.

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.

The lung epithelium regulates gas exchange and is the first line of defense against airborne toxicants and microbial infections. Disruption of the integrity of lung epithelium results in altered permeability and severely impacts normal lung functions. To develop biomarkers of potential harm (BoPH) for assessing adverse health effects of cigarette smoking, we have evaluated lung barrier function. In a single-center, ambulatory, clinical study we measured lung permeability, as the half-life (T1/2) of inhaled 99mTC-DTPA, in 17 subjects consisting of 6 Smokers (SMK), 5 Moist Snuff Consumers (MSC), and 6 Non-Tobacco Consumers (NTC) at three weekly test visits. Smokers, relative to MSC and NTC, exhibited significantly faster clearance of the inhaled probe (shorter T1/2), indicating increased lung permeability. NTC and MSC had comparable clearance times of the inhaled probe (longer T1/2). Least squares regression modeling showed that the variability of the test was minimal and was not significant. Prediction profiling showed that the repeatability of the lung permeability test was robust and was able to differentiate the tobacco product use groups in this study. Thus, altered lung barrier function may serve as a BoPH for assessing the effects of tobacco use.

In this presented case, a 77 years old woman suffering from ongoing knee pain underwent a bone scan using 99mTc-hydroxydiphosphonate (HDP) in suspicious for bone infection. An incidental finding from this scan revealed diffuse cardiac uptake, necessitating further diagnostic procedures to exclude the possibility of cardiac amyloidosis. In the subsequent 99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid (DPD) scan and SPECT images, no perceptible cardiac uptake was observed at all. Upon retrospective review of the patient’s medical records, she had received 1000mg of ferric carboxymaltose for iron-deficient anemia, the day before the 99mTc-HDP bone scan. Therefore, it is assumed that the diffuse and temporary cardiac activity was due to the transient iron overload. We present and share this bone scan images in order to avoid possible future misinterpretation of cardiac amyloidosis.

The aim of this study was to investigate the possible role of 99mTc-sestamibi in the regulation of cancer cell proliferation and apoptosis. To this end, Te in vivo values of 99mTc-sestamibi uptake have been associated to the in-situ expression of both Ki67 and caspase-3. For in vitro investiga-tions BT-474 cells were incubated with three different concentration of 99mTc-sestamibi: 10µg/ml –1µg/ml – 0,1µg/ml. Expression of caspase-3 and Ki67, as well as the ultrastructure of cancer cells, were evaluated at T0 and after 24, 48, 72 and 120 hours after 99mTc-sestamibi incubation. Ex vivo data strengthened the known association between the sestamibi uptake and the Ki67 expression. Linear regression analysis showed a significant association between the sestamibi uptake and the number of apoptotic cells evaluated as caspase-3 positive breast cancer cells. As concern the in vitro data, a significant decrease of the proliferation index was observed in breast cancer cells incubated with high concentration of 99mTc-sestamibi (10µg/ml). Amazingly, a significant increase in caspase-3 positive cells in cultures incubated with 10µg/ml 99mTc-sestamibi was observed. This study suggested the possible role of sestamibi in the regulation of pathophysiological process involved in breast cancer.

Like 18F-FDG, 99mTc-1-thio-D-glucose (99mTc-TG) also binds to GLUT receptors. The aim of this Phase I study was to evaluate the safety, biodistribution and dosimetry of 99mTc-TG. Twelve lym-phoma patients were injected with 729±102 MBq 99mTc-TG. Whole-body planar imaging was per-formed in 10 patients at 2, 4, 6 and 24 h after injection. In all 12 patients SPECT/CT (at 2 h) and SPECT (at 4 and 6 h) imaging was performed. Vital signs and possible side effects were monitored during imaging and up to 7 days after injection. 99mTc-TG injections were well tolerated and no side effects or alterations in blood and urine analyses data were observed. The highest absorbed dose was in the kidneys and urinary bladder wall, followed by the adrenals, prostate, bone mar-row, lungs, myocardium, ovaries, uterus, liver and gall bladder wall. 99mTc-TG SPECT/CT re-vealed foci of high activity uptake in the lymph nodes of all nine patients with known nodal le-sions. Extranodal lesions were detected in all nine cases. In one patient, a lesion in the humerus head, which was not detected by CT, was visualized using 99mTc-TG. Potentially, 99mTc-TG SPECT can be considered as an additional diagnostic method for imaging GLUT receptors in lymphoma patients.