Four regioisomers of [68Ga]Ga-TMoS-DAZA, a PET/CT radio tracer for liver function imaging, were studied as candidates of potentially improved hepatobiliary biokinetics. Liver uptake and biliary clearance behavior were compared using an in ovo model based on ostrich eggs for PET/CT imaging and ex vivo biodistribution analysis. The tracer lipophilicity was evaluated via logD determination. The experiments showed remarkable differences between the four tracers concerning their maximum liver uptake, percentage of tracer cleared via the biliary tract and their respective logD values.

To evaluate the clinical feasibility and potential utility of dynamic [68Ga]Ga-TEoS-DAZA PET/CT for the detection and localisation of bile leaks in patients after hepatobiliary surgery in a small, single-centre feasibility series. Ten patients with clinically suspected postoperative bile leakage and prior inconclusive imaging underwent [68Ga]Ga-TEoS-DAZA PET/CT between September 2024 and February 2026. Imaging was performed following intravenous administration of [68Ga]Ga-TEoS-DAZA (mean activity 214 ± 27 MBq). Dynamic PET acquisition was conducted for 60 min. Findings were analysed and classified according to the Nagano system where applicable, and their contribution to subsequent clinical management was assessed. [68Ga]Ga-TEoS-DAZA PET/CT enabled localisation of bile leaks in 9 of 10 patients (90

Preclinical imaging has recently been expanded through the use of ostrich embryos as an alternative in vivo model. In ovo experiments represent a promising substitute for conventional rodent-based animal testing. For artifact-free dynamic nuclear medicine imaging, reliable immobilization of embryos is essential. Although previous studies have demonstrated the feasibility of isoflurane anesthesia, the kinetics and uptake mechanisms of isoflurane in ostrich embryos remain insufficiently characterized. The aim of this study was to characterize gas exchange dynamics in ostrich eggs and to quantify isoflurane uptake using two complementary approaches: indirect consumption measurements in a closed system and direct quantification by serial blood sampling. Fourteen ostrich eggs, including seven fertilized and seven unfertilized specimens, were analyzed at developmental stages up to day 37 of incubation. Gas exchange was assessed in a sealed container using a clinical anesthesia gas monitoring system to measure oxygen consumption and carbon dioxide excretion. Isoflurane uptake was evaluated during exposure to concentrations of 2%, 4%, or 6%. In a separate experimental series, serial blood samples were collected during and after exposure to the same concentrations to determine systemic uptake. Fertilized embryos showed progressive increases in metabolic activity, with a maximal oxygen consumption and carbon dioxide excretion of 116 mL/h/kg and 93 mL/h/kg on day 37. Indirect measurements demonstrated isoflurane uptake rates of up to 1.1 mL/min at 6%, with proportionally lower values at 4% and 2%. Blood analyses confirmed systemic absorption, peak concentrations of 160 µg/mL, and detectable residual levels for up to 120 min after exposure. These findings refine in ovo imaging.

Animal models are utilized in the investigation of a variety of research questions in nuclear medicine. Radiopharmaceutics are usually tested in mouse, rat or chick chorioallantoic membrane (CAM) models and visualisation of their biodistribution is performed using dedicated small-animal PET/CT scanners. However, the limited availability of such scanners represents a significant bottleneck in preclinical imaging. To address this limitation, we explored an alternative animal model compatible with clinical imaging systems. The ostrich chorioallantoic membrane (CAM) was utilized as a platform for tumor xenografts, enabling imaging with a standard human PET/CT scanner. Growth conditions for tumor formation were established using human glioblastoma (U87) and breast cancer (MDA-MB-231) cell lines. Tumor visualization was achieved using 18F-fluorodeoxyglucose (18F-FDG), a widely used clinical PET tracer, and its pharmacodynamic behavior was assessed. Our findings demonstrate that the ostrich CAM tumor model is a feasible and efficient system for the rapid evaluation of diagnostic tracers. Importantly, tracer uptake and kinetics can be reliably assessed using a clinical PET/CT scanner. This approach highlights the potential of the ostrich embryonic model as a versatile and accessible preclinical platform for nuclear medicine research.

The aim of this study was to investigate the dynamic biodistribution of [68Ga]Ga-TEoS-DAZA, a functional liver PET tracer, in 2 preclinical models (ostrich embryos and mice) and in a healthy human liver donor to identify similarities and differences among the 3 species, which are relevant in translational nuclear medicine. Furthermore, the molecular pathway and metabolism of [68Ga]Ga-TEoS-DAZA was investigated. Methods: The dynamic biodistribution of [68Ga]Ga-TEoS-DAZA was determined via PET/CT in ostrich embryos, in healthy mice (C57BL/6), and in a healthy human liver donor. Hepatocyte transporter binding studies were performed in transfected HEK293t cells. Metabolite analysis was performed in samples from ostrich embryos and a healthy liver donor. Blocking studies against cyclosporine A were performed in ostrich embryos. Results: The biodistribution of [68Ga]Ga-TEoS-DAZA was comparable in ostrich embryos, healthy mice (C57BL/6), and the healthy donor. In all 3 species, the tracer showed specific uptake in liver tissue (30-40 %IA at time of peak) and subsequent biliary excretion, whereas less than 5 %IA activity was excreted renally. The hepatic transit time in mice was significantly faster than in ostrich embryos and human, with mice exhibiting a much shorter time-to-peak (1.7 min) than the other 2 species (15-21 min) and rapid clearance of the tracer from the liver into the intestines. [68Ga]Ga-TEoS-DAZA is a substrate for OATP1B3, with tracer uptake into the liver being hampered in the presence of cyclosporine A. Tissue samples revealed an as yet unknown radiometabolite of [68Ga]Ga-TEoS-DAZA, indicating hepatic metabolism. Conclusion: [68Ga]Ga-TEoS-DAZA was shown to be a suitable hepatobiliary tracer using both mice and ostrich embryos as preclinical models; however, there were limits in translatability in both models because of a distinctly faster hepatic uptake and biliary excretion (mice) or a slower biliary excretion (ostrich embryo) compared with that in the human.

Background/Objectives: Biliary complications are common after liver transplantation (LT), with bile leaks representing a major cause of morbidity. Conventional imaging modalities such as ultrasound, CT, MRCP, and endoscopic techniques may fail to localize peripheral or complex leaks. This study aimed to evaluate the feasibility of [68Ga]Ga-TEoS-DAZA-PET/CT for non-invasive localization of bile leaks after LT. Methods: Five male patients (mean age 53.2 years) with suspected bile leakage and inconclusive prior imaging underwent [68Ga]Ga-TEoS-DAZA-PET/CT. The tracer was synthesized under GMP conditions and administered at a mean activity of 204 ± 42 MBq. Dynamic PET/CT imaging was performed for 60 min, and findings were classified according to the Nagano classification. Results: Bile leaks were detected and anatomically localized in all five patients. Sites included the liver resection surface, central bile ducts, bilioenteric anastomosis, and biliary drainage exit. PET/CT findings guided revision surgery in one case and endoscopic treatment in three, while one patient improved without intervention. No adverse effects occurred. Conclusions: [68Ga]Ga-TEoS-DAZA-PET/CT is a feasible and safe imaging technique for the anatomical localization of bile leaks following LT. Its antegrade visualization of biliary flow, high spatial and temporal resolution, and lack of contraindications make it a promising complementary modality when conventional imaging is inconclusive or not feasible. Larger studies are warranted to validate its diagnostic value and clinical utility in postoperative and post-traumatic biliary injuries.

Ostrich eggs have recently attracted interest as an alternative model in preclinical nuclear medicine imaging. The ability to be used in clinical PET/CT (positron emission tomography/computed tomography) systems and their ethical profile are advantageous over conventional rodent models and other avian systems. Nevertheless, concerns regarding radiation exposure during repeated CT (computed tomography) imaging of developing embryos remain inadequately addressed. This study aimed to characterize the attenuation impact of eggshells in ostrich eggs and to evaluate the potential for organ-specific dose assessment. A representative ostrich egg was selected from a cohort of 168 eggs and used to construct a dimensionally matched 3D-printed phantom. Organ weights of 83 embryos were documented on development day (DD) 37 to provide a basis for future organ-level dosimetric modeling. Thermoluminescence dosimeters (TLDs) were positioned along the z-axis within both the egg and phantom, and CT dose distributions were measured using a clinical PET/CT system. The mean absorbed dose in the real egg was 16.3 ± 2.0

A 50-year-old man with a history of a gunshot wound to the skull base in 1997 presented with new secretion from a retroauricular skin defect and clinical signs of a cerebrospinal fluid (CSF) leak. MRI was contraindicated due to retained metallic foreign bodies. [64Cu]Cu-DOTA PET/CT cisternography revealed progressive extravasation of CSF tracer from the posterior fossa toward a mastoid defect, consistent with a CSF leak, but no fistula to the skin. Intraoperative findings confirmed the leak and identified a cholesteatoma within the bullet tract. This case illustrates the complexity of temporal bone gunshot injuries and highlights the diagnostic utility of PET/CT cisternography in detecting CSF leaks.

Ziel/Aim: [68Ga]Ga-TEoS-DAZA und [68Ga]Ga-BP-IDA wurden hinsichtlich ihrer Eignung als PET-Tracer für die Leberfunktionsquantifizierung und die Gallenwegsdarstellung untersucht. Die Leberbildgebung mit PET bietet eine Alternative zur hepatobiliären MRT, respektive zur SPECT. Die dargelegten Untersuchungen der Tracer zielen darauf ab, erste klinische Nachweise für hepatobiliäre PET/CT zu erbringen.

N,1,4-Tri(4-ethoxy-2-hydroxybenzyl)-1,4-diazepan-6-amine (TEoS-DAZA), a novel radiopharmaceutical precursor for a liver-specific 68Ga-based diagnostic radiopharmaceutical, was tested for toxicity in rats to ensure its safe applicability and to fulfil the preclinical requirements in preparation of a clinical study. The study was performed according to EMA draft Guideline on the non-clinical requirements for radiopharmaceuticals, as well as to the so-called microdosing approach of the ICH guideline M3 (R2). This randomized study was conducted using Wistar rats. The test item was administered intravenously at three different dose levels, the vehicle solution was administered to a separate group as control. Toxicity assessment included a 24 h observation period in three dose groups, and a 14-day recovery period in the high dose group. Animals were monitored regarding clinical behaviour, bodyweight, food and water consumption, additionally undergoing modified IRWIN, grip-strength and beam-walking tests. Following euthanisation, extensive haematological and clinical biochemical parameters were analysed. Necropsy and histopathology were performed. There was no evidence to any test-item related adversities at any dose level. No delayed effects were identified in any animal at the end of the recovery phase. Some small, albeit significant changes in haematology and clinical biochemistry could not be related to the test item administration. The NOAEL of TEoS-DAZA was determined at 1.4 mg/kg bodyweight. Administration of a thousandfold clinical dose of TEoS-DAZA in rats did not cause any observable adverse events. An injectable solution of [68Ga]Ga-TEoS-DAZA containing 100 µg of the precursor is safe for clinical application to humans from the pharmacological point of view. Subsequent dosimetry studies need to be undertaken to reveal any radiation related toxicity.

The aim of this study was to investigate the preclinical biodistribution and molecular pathway of [68Ga]Ga-BP-IDA and to evaluate its clinical suitability for quantitative monitoring of liver function during transarterial radioembolization (TARE) therapy of a hepatocellular carcinoma (HCC). [68Ga]Ga-BP-IDA undergoes hepatobiliary clearance, with uptake into hepatocytes via OATP1B1 and OATP1B3. [68Ga]Ga-BP-IDA exhibits demetallation in vivo but is nevertheless suitable for clinical application due to its rapid uptake into functional liver tissue. In a clinical case [68Ga]Ga-BP-IDA PET/CT allowed for differentiation of functional liver mass from cancerous tissue and enabled monitoring the effect on liver and tumor volume as well as on residual liver function after TARE therapy. Following TARE treatment, a reduction of the hepatic uptake rate was observed in both non-cancerous liver lobes, but was more pronounced in the right lobe, indicating a correlation to the higher non-targeted radiation dose from the TARE treatment in this lobe. [68Ga]Ga-BP-IDA PET/CT thus revealed additional information on liver function impairment which was not represented by CT-based volumetry alone. [68Ga]Ga-BP-IDA PET/CT is a suitable tool for planning and monitoring TARE therapy of primary liver tumors and may complement the limits of volumetry-based methods with functional information about the liver.

In-ovo imaging using ostrich eggs has been described as an alternative to animal testing using rodents. This approach is not considered an animal experiment and it does not require small-animal imaging devices as ostrich eggs provide good image quality on regular CT, MRI or PET used in humans. The aims of this study were 1) to describe methods of radiopharmaceutical injection, 2) to explore normal biodistribution of F-18-FDG during a 60-min list-mode-PET/CT examination and 3) to compare biodistribution in-ovo to existing literature considering chicken and rodents. Vessel access was successful in 54/78 ostrich eggs. Highest FDG-uptake was observed in epiphyseal plates (0.36 ± 0.06 IA%/g; range 0.29-0.48 IA%/g) and brain (0.25 ± 0.05 IA%/g; range 0.21-0.36 IA%/g). In-vivo activity distribution on PET and ex-vivo activity distribution (well counter) showed comparable results (Spearman's Rho range 0.795-0.882). No significant differences were observed regarding previous isoflurane exposure. Normal biodistribution of F-18-FDG in ostrich embryos using a standard PET/CT system for humans was mainly found as expected with highest uptake in epiphyseal plates and brain which is comparable to results on rodents and chicken embryos. Isoflurane anesthesia did not reveal significant differences regarding organ uptake. The results of this normal distribution study allow for interpretation of future disease models (inflammation, tumor) in ostrich embryos using F-18-FDG as radiopharmaceutical.

TO THE EDITOR: Recently, PET of the cerebrospinal fluid (CSF) space with [68Ga]Ga-DOTA has been proposed as a fast and convenient approach for verification of spinal CSF leaks ([1][1]). PET-based radiocisternography with [68Ga]Ga-ethylenediaminetetraacetic acid, [55Co]Co-

1,4-Diazepane-6-amine (DAZA) can be alkylated with three 2-hydroxybenzyl pendant arms, resulting in hexadentate chelators suitable for coordination of radiometals like 68Ga. These chelators, N,1,4-tri(alkoxy-2-hydroxybenzyl)-DAZA, can be produced via a one-pot synthesis, with the first step being a carbonyl amine condensation of DAZA with two respective 4-alkoxy-2-hydroxybenzaldehydes, followed by reductive amination with sodium borohydride. While the first step of this reaction is predictable, the subsequent reductive amination can result in either mono-, di- or tri(alkoxy-hydroxybenzyl)-DAZA compounds. Seeking to identify dependencies that might allow a specific reaction control towards the formation of either of the three possible products, and particularly towards the favoured trialkylated DAZA compounds, a variety of synthesis trials were performed. Additionally, computational methods were employed to evaluate the underlying reaction mechanism. Synthesis trials verified that the trialkylated DAZA compounds are formed via direct reductive amination of the dialkylated DAZA compounds. Subsequently, a synthetic method was established, leading to an increase in the percentage of the trialkylated DAZA compounds, which allowed the successful isolation of those hexadentate chelators. Additionally, an alternative pathway proceeding via aminal C–N bond insertion of an attacking third carbonyl moiety was evaluated by means of quantum chemical calculations but so far remains entirely hypothetical.

Fertilized bird eggs are an alternative model to conventional animal testing. In recent studies, a preclinical imaging model based on large ostrich eggs was introduced in a clinical research centre using imaging systems designed for humans, thus bypassing the need for dedicated small animal imaging systems. Ostrich eggs are only laid during the season with increased daylength, which limits its year-round availability. The current study focuses on large emu eggs instead of ostrich eggs and aims at investigating its suitability for preclinical imaging research. Physiological development of emu embryos was observed by serial weightings and serial CT scans until developmental day (DD) 46. Differences between fertilized a non-fertilized eggs were analysed. In fertilized eggs, the embryo was identified on CT scans as early as DD 13. As expected, CT scans showed continuous embryonal development and growth over time, comparable to ostriches. Neither the eggs' volume and weight nor the weight loss nor the radiodensity provided significant differences between fertilized and non-fertilized eggs. Despite inferior incubation success in emus compared to ostriches, suitability of emu eggs for artificial incubation and subsequent research was confirmed. Hence, emu eggs represent an alternative model for preclinical imaging and allow a year-round use for research purposes if combined with ostrich eggs.

In-ovo imaging using avian eggs has been described as a potential alternative to animal testing using rodents. However, imaging studies are hampered by embryonal motion producing artifacts. This study aims at systematically comparing isoflurane, desflurane and sevoflurane in three different concentrations in ostrich embryos. Biomagnetic signals of ostrich embryos were recorded analyzing cardiac action and motion. Ten groups comprising eight ostrich embryos each were investigated: Control, isoflurane (2%, 4%, and 6%), desflurane (6%, 12%, and 18%) and sevoflurane (3%, 5%, and 8%). Each ostrich egg was exposed to the same narcotic gas and concentration on development day (DD) 31 and 34. Narcotic gas exposure was upheld for 90 min and embryos were monitored for additional 75 min. Toxicity was evaluated by verifying embryo viability 24 h after the experiments. Initial heart rate of mean 148 beats/min (DD 31) and 136 beats/min (DD 34) decreased over time by 44–48 beats/minute. No significant differences were observed between groups. All narcotic gases led to distinct movement reduction after mean 8 min. Embryos exposed to desflurane 6% showed residual movements. Isoflurane 6% and sevoflurane 8% produced motion-free time intervals of mean 70 min after discontinuation of narcotic gas exposure. Only one embryo death occurred after narcotic gas exposure with desflurane 6%. This study shows that isoflurane, desflurane and sevoflurane are suitable for ostrich embryo immobilization, which is a prerequisite for motion-artifact free imaging. Application of isoflurane 6% and sevoflurane 8% is a) safe as no embryonal deaths occurred after exposure and b) effective as immobilization was observed for approx. 70 min after the end of narcotic gas exposure. These results should be interpreted with caution regarding transferability to other avian species as differences in embryo size and incubation duration exist.

Ziel/Aim The purpose of this project was the development of a PET tracer for splenic imaging, its radiopharmaceutical validation, and application in selected patients in whom unclear constellations of findings could not be resolved with established imaging methods.

Several scintigraphic techniques have been supplemented or replaced by PET/CT methods because of their superior sensitivity, high resolution, and absolute activity quantification capability. The purpose of this project was the development of a PET tracer for splenic imaging, its radiopharmaceutical validation, and its application in selected patients in whom unclear constellations of findings could not be resolved with established imaging methods. Heat-damaged red blood cells (RBCs) were labeled with [68Ga]gallium-oxine, which was produced from [68Ga]gallium and 8-Hydroxyquinoline (oxine) on an automated synthesizer. Ten patients underwent [68Ga]gallium-oxine-RBC-PET/CT for the classification of eleven unclear lesions (3 intra-, 8 extrapancreatic). [68Ga]gallium-oxine and [68Ga]gallium-oxine-labeled RBCs could be synthesized reproducibly and reliably. The products met GMP quality standards. The tracer showed high accumulation in splenic tissue. Of the 11 lesions evaluated by PET/CT, 3 were correctly classified as non-splenic, 6 as splenic, 1 as equivocal, and 1 lesion as a splenic hypoplasia. All lesions classified as non-splenic were malignant, and all lesions classified as splenic did not show malignant features during follow-up. PET/CT imaging of the spleen with [68Ga]gallium-oxine-labeled, heat-damaged RBCs is feasible and allowed differentiation of splenic from non-splenic tissues, and the diagnosis of splenic anomalies.