TY - JOUR A1 - Toyama, Yoshitaka A1 - Werner, Rudolf A. A1 - Ruiz-Bedoya, Camilo A. A1 - Ordonez, Alvaro A. A1 - Takase, Kei A1 - Lapa, Constantin A1 - Jain, Sanjay K. A1 - Pomper, Martin G. A1 - Rowe, Steven P. A1 - Higuchi, Takahiro T1 - Current and future perspectives on functional molecular imaging in nephro-urology: theranostics on the horizon JF - Theranostics N2 - In recent years, a paradigm shift from single-photon-emitting radionuclide radiotracers toward positron-emission tomography (PET) radiotracers has occurred in nuclear oncology. Although PET-based molecular imaging of the kidneys is still in its infancy, such a trend has emerged in the field of functional renal radionuclide imaging. Potentially allowing for precise and thorough evaluation of renal radiotracer urodynamics, PET radionuclide imaging has numerous advantages including precise anatomical co-registration with CT images and dynamic three-dimensional imaging capability. In addition, relative to scintigraphic approaches, PET can allow for significantly reduced scan time enabling high-throughput in a busy PET practice and further reduces radiation exposure, which may have a clinical impact in pediatric populations. In recent years, multiple renal PET radiotracers labeled with C-11, Ga-68, and F-18 have been utilized in clinical studies. Beyond providing a precise non-invasive read-out of renal function, such radiotracers may also be used to assess renal inflammation. This manuscript will provide an overview of renal molecular PET imaging and will highlight the transformation of conventional scintigraphy of the kidneys toward novel, high-resolution PET imaging for assessing renal function. In addition, future applications will be introduced, e.g. by transferring the concept of molecular image-guided diagnostics and therapy (theranostics) to the field of nephrology. KW - glomerular filtration rate KW - renal KW - kidney KW - renal function KW - positron emission tomography KW - nephrology KW - urology KW - molecular imaging KW - theranostics Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-260090 VL - 11 IS - 12 ER - TY - JOUR A1 - Matsusaka, Yohji A1 - Werner, Rudolf A. A1 - Arias-Loza, Paula A1 - Nose, Naoko A1 - Sasaki, Takanori A1 - Chen, Xinyu A1 - Lapa, Constantin A1 - Higuchi, Takahiro T1 - Performance Evaluation of a Preclinical SPECT Scanner with a Collimator Designed for Medium-Sized Animals JF - Molecular Imaging N2 - Background. Equipped with two stationary detectors, a large bore collimator for medium-sized animals has been recently introduced for dedicated preclinical single-photon emission computed tomography (SPECT) imaging. We aimed to evaluate the basic performance of the system using phantoms and healthy rabbits. Methods. A general-purpose medium-sized animal (GP-MSA) collimator with 135 mm bore diameter and thirty-three holes of 2.5 mm diameter was installed on an ultrahigh-resolution scanner equipped with two large stationary detectors (U-SPECT5-E/CT). The sensitivity and uniformity were investigated using a point source and a cylinder phantom containing 99mTc-pertechnetate, respectively. Uniformity (in %) was derived using volumes of interest (VOIs) on images of the cylinder phantom and calculated as , with lower values of % indicating superior performance. The spatial resolution and contrast-to-noise ratios (CNRs) were evaluated with images of a hot-rod Derenzo phantom using different activity concentrations. Feasibility of in vivo SPECT imaging was finally confirmed by rabbit imaging with the most commonly used clinical myocardial perfusion SPECT agent [99mTc]Tc-sestamibi (dynamic acquisition with a scan time of 5 min). Results. In the performance evaluation, a sensitivity of 790 cps/MBq, a spatial resolution with the hot-rod phantom of 2.5 mm, and a uniformity of 39.2% were achieved. The CNRs of the rod size 2.5 mm were 1.37, 1.24, 1.20, and 0.85 for activity concentration of 29.2, 1.0, 0.5, and 0.1 MBq/mL, respectively. Dynamic SPECT imaging in rabbits allowed to visualize most of the thorax and to generate time-activity curves of the left myocardial wall and ventricular cavity. Conclusion. Preclinical U-SPECT5-E/CT equipped with a large bore collimator demonstrated adequate sensitivity and resolution for in vivo rabbit imaging. Along with its unique features of SPECT molecular functional imaging is a superior collimator technology that is applicable to medium-sized animal models and thus may promote translational research for diagnostic purposes and development of novel therapeutics. KW - SPECT Scanner KW - medium-sized animals KW - performance Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-300713 VL - 2022 ER - TY - JOUR A1 - Werner, Rudolf A. A1 - Chen, Xinyu A1 - Hirano, Mitsuru A1 - Rowe, Steven P. A1 - Lapa, Constantin A1 - Javadi, Mehrbod S. A1 - Higuchi, Takahiro T1 - SPECT vs. PET in Cardiac Innervation Imaging: Clash of the Titans JF - Clinical and Translational Imaging N2 - Purpose: We aim to provide an overview of the conventional single photon emission computed tomography (SPECT) and emerging positron emission tomography (PET) catecholamine analogue tracers for assessing myocardial nerve integrity, in particular focusing on \(^{18}\)F-labeled tracers. Results: Increasingly, the cardiac sympathetic nervous system (SNS) is being studied by non-invasive molecular imaging approaches. Forming the backbone of myocardial SNS imaging, the norepinephrine (NE) transporter at the sympathetic nerve terminal plays a crucial role for visualizing denervated myocardium: in particular, the single-photon-emitting NE analogue \(^{123}\)I-meta-Iodobenzylguanidine (\(^{123}\)I-mIBG) has demonstrated favorable results in the identification of patients at a high risk for cardiac death. However, cardiac neuronal PET agents offer several advantages inlcuding improved spatio-temporal resolution and intrinsic quantifiability. Compared to their \(^{11}\)C-labeled counterparts with a short half-life (20.4 min), novel \(^{18}\)F-labeled PET imaging agents to assess myocardial nerve integrity have the potential to revolutionize the field of SNS molecular imaging: The longer half-life of \(^{18}\)F (109.8 min) allows for more flexibility in the study design and delivery from central cyclotron facilities to smaller hospitals may lead to further cost reduction. A great deal of progress has been made by the first in-human studies of such \(^{18}\)F-labeled SNS imaging agents. Moreover, dedicated animal platforms open avenues for further insights into the handling of radiolabeled catecholamine analogues at the sympathetic nerve terminal. Conclusions: \(^{18}\)F-labeled imaging agents demonstrate key properties for mapping cardiac sympathetic nerve integrity and might outperform current SPECT-based or \(^{11}\)C-labeled tracers in the long run. KW - single photon emission computed tomography: sympathetic nerve KW - Positronen-Emissions-Tomografie KW - 18F-LMI1195 KW - 11C-hydroxyephedrine KW - 123I-metaiodobenzylguanidine KW - positron emission tomography Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-163628 SN - 2281-5872 ER - TY - JOUR A1 - Nose, Naoko A1 - Werner, Rudolf A. A1 - Ueda, Yuichiro A1 - Günther, Katharina A1 - Lapa, Constantin A1 - Javadi, Mehrbod S. A1 - Fukushima, Kazuhito A1 - Edenhofer, Frank A1 - Higuchi, Takahiro T1 - Metabolic substrate shift in human induced pluripotent stem cells during cardiac differentiation: Functional assessment using in vitro radionuclide uptake assay JF - International Journal of Cardiology N2 - BACKGROUND: Recent developments in cellular reprogramming technology enable the production of virtually unlimited numbers of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM). Although hiPSC-CM share various characteristic hallmarks with endogenous cardiomyocytes, it remains a question as to what extent metabolic characteristics are equivalent to mature mammalian cardiomyocytes. Here we set out to functionally characterize the metabolic status of hiPSC-CM in vitro by employing a radionuclide tracer uptake assay. MATERIAL AND METHODS: Cardiac differentiation of hiPSC was induced using a combination of well-orchestrated extrinsic stimuli such as WNT activation (by CHIR99021) and BMP signalling followed by WNT inhibition and lactate based cardiomyocyte enrichment. For characterization of metabolic substrates, dual tracer uptake studies were performed with \(^{18}\)F‑2‑fluoro‑2‑deoxy‑d‑glucose (\(^{18}\)F-FDG) and \(^{125}\)I‑β‑methyl‑iodophenyl‑pentadecanoic acid (\(^{125}\)I-BMIPP) as transport markers of glucose and fatty acids, respectively. RESULTS: After cardiac differentiation of hiPSCs, in vitro tracer uptake assays confirmed metabolic substrate shift from glucose to fatty acids that was comparable to those observed in native isolated human cardiomyocytes. Immunostaining further confirmed expression of fatty acid transport and binding proteins on hiPSC-CM. CONCLUSIONS: During in vitro cardiac maturation, we observed a metabolic shift to fatty acids, which are known as a main energy source of mammalian hearts, suggesting hi-PSC-CM as a potential functional phenotype to investigate alteration of cardiac metabolism in cardiac diseases. Results also highlight the use of available clinical nuclear medicine tracers as functional assays in stem cell research for improved generation of autologous differentiated cells for numerous biomedical applications. KW - tracer KW - Stammzelle KW - induced pluripotent stem cells KW - cardiomyocytes KW - fatty acid KW - stem cell therapy KW - hiPSC-CM Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-170699 VL - 269 ER - TY - JOUR A1 - Serfling, Sebastian E. A1 - Lapa, Constantin A1 - Dreher, Niklas A1 - Hartrampf, Philipp E. A1 - Rowe, Steven P. A1 - Higuchi, Takahiro A1 - Schirbel, Andreas A1 - Weich, Alexander A1 - Hahner, Stefanie A1 - Fassnacht, Martin A1 - Buck, Andreas K. A1 - Werner, Rudolf A. T1 - Impact of tumor burden on normal organ distribution in patients imaged with CXCR4-targeted [\(^{68}\)Ga]Ga-PentixaFor PET/CT JF - Molecular Imaging and Biology N2 - Background CXCR4-directed positron emission tomography/computed tomography (PET/CT) has been used as a diagnostic tool in patients with solid tumors. We aimed to determine a potential correlation between tumor burden and radiotracer accumulation in normal organs. Methods Ninety patients with histologically proven solid cancers underwent CXCR4-targeted [\(^{68}\)Ga]Ga-PentixaFor PET/CT. Volumes of interest (VOIs) were placed in normal organs (heart, liver, spleen, bone marrow, and kidneys) and tumor lesions. Mean standardized uptake values (SUV\(_{mean}\)) for normal organs were determined. For CXCR4-positive tumor burden, maximum SUV (SUV\(_{max}\)), tumor volume (TV), and fractional tumor activity (FTA, defined as SUV\(_{mean}\) x TV), were calculated. We used a Spearman's rank correlation coefficient (ρ) to derive correlative indices between normal organ uptake and tumor burden. Results Median SUV\(_{mean}\) in unaffected organs was 5.2 for the spleen (range, 2.44 – 10.55), 3.27 for the kidneys (range, 1.52 – 17.4), followed by bone marrow (1.76, range, 0.84 – 3.98), heart (1.66, range, 0.88 – 2.89), and liver (1.28, range, 0.73 – 2.45). No significant correlation between SUV\(_{max}\) in tumor lesions (ρ ≤ 0.189, P ≥ 0.07), TV (ρ ≥ -0.204, P ≥ 0.06) or FTA (ρ ≥ -0.142, P ≥ 0.18) with the investigated organs was found. Conclusions In patients with solid tumors imaged with [\(^{68}\)Ga]Ga-PentixaFor PET/CT, no relevant tumor sink effect was noted. This observation may be of relevance for therapies with radioactive and non-radioactive CXCR4-directed drugs, as with increasing tumor burden, the dose to normal organs may remain unchanged. KW - CXCR4 KW - C-X-C motif chemokine receptor 4 KW - PET KW - [68Ga]PentixaFor KW - [177Lu]/[90Y]PentixaTher KW - theranostics KW - endoradiotherapy Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-324622 VL - 24 IS - 4 ER - TY - JOUR A1 - Weich, Alexander A1 - Higuchi, Takahiro A1 - Bundschuh, Ralph A. A1 - Lapa, Constantin A1 - Serfling, Sebastian E. A1 - Rowe, Steven P. A1 - Pomper, Martin G. A1 - Herrmann, Ken A1 - Buck, Andreas K. A1 - Derlin, Thorsten A1 - Werner, Rudolf A. T1 - Training on reporting and data system (RADS) for somatostatin-receptor targeted molecular imaging can reduce the test anxiety of inexperienced readers JF - Molecular Imaging and Biology N2 - Purpose For somatostatin receptor (SSTR)-positron emission tomography/computed tomography (PET/CT), a standardized framework termed SSTR-reporting and data system (RADS) has been proposed. We aimed to elucidate the impact of a RADS-focused training on reader’s anxiety to report on SSTR-PET/CT, the motivational beliefs in learning such a system, whether it increases reader’s confidence, and its implementation in clinical routine. Procedures A 3-day training course focusing on SSTR-RADS was conducted. Self-report questionnaires were handed out prior to the course (Pre) and thereafter (Post). The impact of the training on the following categories was evaluated: (1) test anxiety to report on SSTR-PET/CT, (2) motivational beliefs, (3) increase in reader’s confidence, and (4) clinical implementation. To assess the effect size of the course, Cohen’s d was calculated (small, d = 0.20; large effect, d = 0.80). Results Of 22 participants, Pre and Post were returned by 21/22 (95.5%). In total, 14/21 (66.7%) were considered inexperienced (IR, < 1 year experience in reading SSTR-PET/CTs) and 7/21 (33.3%) as experienced readers (ER, > 1 year). Applying SSTR-RADS, a large decrease in anxiety to report on SSTR-PET/CT was noted for IR (d =  − 0.74, P = 0.02), but not for ER (d = 0.11, P = 0.78). For the other three categories motivational beliefs, reader’s confidence, and clinical implementation, agreement rates were already high prior to the training and persisted throughout the course (P ≥ 0.21). Conclusions A framework-focused reader training can reduce anxiety to report on SSTR-PET/CTs, in particular for inexperienced readers. This may allow for a more widespread adoption of this system, e.g., in multicenter trials for better intra- and interindividual comparison of scan results. KW - PET/CT KW - neuroendocrine tumor KW - PRRT KW - peptide receptor radionuclide therapy KW - reporting and data system KW - SSTR-RADS KW - RADS Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-324645 VL - 24 IS - 4 ER - TY - JOUR A1 - Marquardt, André A1 - Hartrampf, Philipp A1 - Kollmannsberger, Philip A1 - Solimando, Antonio G. A1 - Meierjohann, Svenja A1 - Kübler, Hubert A1 - Bargou, Ralf A1 - Schilling, Bastian A1 - Serfling, Sebastian E. A1 - Buck, Andreas A1 - Werner, Rudolf A. A1 - Lapa, Constantin A1 - Krebs, Markus T1 - Predicting microenvironment in CXCR4- and FAP-positive solid tumors — a pan-cancer machine learning workflow for theranostic target structures JF - Cancers N2 - (1) Background: C-X-C Motif Chemokine Receptor 4 (CXCR4) and Fibroblast Activation Protein Alpha (FAP) are promising theranostic targets. However, it is unclear whether CXCR4 and FAP positivity mark distinct microenvironments, especially in solid tumors. (2) Methods: Using Random Forest (RF) analysis, we searched for entity-independent mRNA and microRNA signatures related to CXCR4 and FAP overexpression in our pan-cancer cohort from The Cancer Genome Atlas (TCGA) database — representing n = 9242 specimens from 29 tumor entities. CXCR4- and FAP-positive samples were assessed via StringDB cluster analysis, EnrichR, Metascape, and Gene Set Enrichment Analysis (GSEA). Findings were validated via correlation analyses in n = 1541 tumor samples. TIMER2.0 analyzed the association of CXCR4 / FAP expression and infiltration levels of immune-related cells. (3) Results: We identified entity-independent CXCR4 and FAP gene signatures representative for the majority of solid cancers. While CXCR4 positivity marked an immune-related microenvironment, FAP overexpression highlighted an angiogenesis-associated niche. TIMER2.0 analysis confirmed characteristic infiltration levels of CD8+ cells for CXCR4-positive tumors and endothelial cells for FAP-positive tumors. (4) Conclusions: CXCR4- and FAP-directed PET imaging could provide a non-invasive decision aid for entity-agnostic treatment of microenvironment in solid malignancies. Moreover, this machine learning workflow can easily be transferred towards other theranostic targets. KW - machine learning KW - tumor microenvironment KW - immune infiltration KW - angiogenesis KW - mRNA KW - miRNA KW - transcriptome Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-305036 SN - 2072-6694 VL - 15 IS - 2 ER - TY - JOUR A1 - Tutov, Anna A1 - Chen, Xinyu A1 - Werner, Rudolf A. A1 - Mühlig, Saskia A1 - Zimmermann, Thomas A1 - Nose, Naoko A1 - Koshino, Kazuhiro A1 - Lapa, Constantin A1 - Decker, Michael A1 - Higuchi, Takahiro T1 - Rationalizing the binding modes of PET radiotracers targeting the norepinephrine transporter JF - Pharmaceutics N2 - Purpose: A new PET radiotracer \(^{18}\)F-AF78 showing great potential for clinical application has been reported recently. It belongs to a new generation of phenethylguanidine-based norepinephrine transporter (NET)-targeting radiotracers. Although many efforts have been made to develop NET inhibitors as antidepressants, systemic investigations of the structure–activity relationships (SARs) of NET-targeting radiotracers have rarely been performed. Methods: Without changing the phenethylguanidine pharmacophore and 3-fluoropropyl moiety that is crucial for easy labeling, six new analogs of \(^{18}\)F-AF78 with different meta-substituents on the benzene-ring were synthesized and evaluated in a competitive cellular uptake assay and in in vivo animal experiments in rats. Computational modeling of these tracers was established to quantitatively rationalize the interaction between the radiotracers and NET. Results: Using non-radiolabeled reference compounds, a competitive cellular uptake assay showed a decrease in NET-transporting affinity from meta-fluorine to iodine (0.42 and 6.51 µM, respectively), with meta-OH being the least active (22.67 µM). Furthermore, in vivo animal studies with radioisotopes showed that heart-to-blood ratios agreed with the cellular experiments, with AF78(F) exhibiting the highest cardiac uptake. This result correlates positively with the electronegativity rather than the atomic radius of the meta-substituent. Computational modeling studies revealed a crucial influence of halogen substituents on the radiotracer–NET interaction, whereby a T-shaped π–π stacking interaction between the benzene-ring of the tracer and the amino acid residues surrounding the NET binding site made major contributions to the different affinities, in accordance with the pharmacological data. Conclusion: The SARs were characterized by in vitro and in vivo evaluation, and computational modeling quantitatively rationalized the interaction between radiotracers and the NET binding site. These findings pave the way for further evaluation in different species and underline the potential of AF78(F) for clinical application, e.g., cardiac innervation imaging or molecular imaging of neuroendocrine tumors. KW - positron emission tomography KW - norepinephrine transporter KW - sympathetic nervous system KW - structure–activity relationships KW - T-shaped π–π stacking Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-303949 SN - 1999-4923 VL - 15 IS - 2 ER -