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ZusammenfassungDie hybride Bildgebung in Form der SPECT/CT oder PET/CT bietet einen relevanten diagnostischen Vorteil durch die Kombination anatomischer mit funktioneller Bildgebung. Hierdurch wird neben der Möglichkeit der präzisen morphologischen Zuordnung funktioneller Prozesse auch eine Verbesserung der Bildgüte erzielt. Zur Sicherstellung einer einwandfreien Funktionsweise und konstant hohen Qualität der hybriden Bildgebung kommt der Qualitätssicherung an hybriden Systemen eine besondere Bedeutung zu. Hier gilt es, die Anforderungen an die einzelnen Komponenten zu beachten, wie auch die Anforderungen, die aus der Kombination beider Komponenten entstehen. Für alle 3 Teile (Computertomografie, nuklearmedizinscher Teil und hybride Bildgebung) gelten entsprechende regulatorische Grundlagen. Diese sind im folgenden Übersichtsartikel zusammengestellt. Darüber hinaus wird ein Überblick über die Prüfverfahren zur Abnahmeprüfung der Teilkomponenten sowie über die Konstanzprüfungen vermittelt. Es werden jedoch keine konkreten Erläuterungen zur Durchführung der einzelnen Prüfungen gegeben.

Purpose Tracer kinetic modeling of tissue time activity curves and the individual input function based on arterial blood sampling and metabolite correction is the gold standard for quantitative characterization of microglia activation by PET with the translocator protein (TSPO) ligand 18F-GE-180. This study tested simplified methods for quantification of 18F-GE-180 PET. Methods Dynamic 18F-GE-180 PET with arterial blood sampling and metabolite correction was performed in five healthy volunteers and 20 liver-transplanted patients. Population-based input function templates were generated by averaging individual input functions normalized to the total area under the input function using a leave-one-out approach. Individual population-based input functions were obtained by scaling the input function template with the individual parent activity concentration of 18F-GE-180 in arterial plasma in a blood sample drawn at 27.5 min or by the individual administered tracer activity, respectively. The total 18F-GE-180 distribution volume (VT) was estimated in 12 regions-of-interest (ROIs) by the invasive Logan plot using the measured or the population-based input functions. Late ROI-to-whole-blood and ROI-to-cerebellum ratio were also computed. Results Correlation with the reference VT (with individually measured input function) was very high for VT with the population-based input function scaled with the blood sample and for the ROI-to-whole-blood ratio (Pearson correlation coefficient = 0.989 ± 0.006 and 0.970 ± 0.005). The correlation was only moderate for VT with the population-based input function scaled with tracer activity dose and for the ROI-to-cerebellum ratio (0.653 ± 0.074 and 0.384 ± 0.177). Reference VT, population-based VT with scaling by the blood sample, and ROI-to-whole-blood ratio were sensitive to the TSPO gene polymorphism. Population-based VT with scaling to the administered tracer activity and the ROI-to-cerebellum ratio failed to detect a polymorphism effect. Conclusion These results support the use of a population-based input function scaled with a single blood sample or the ROI-to-whole-blood ratio at a late time point for simplified quantitative analysis of 18F-GE-180 PET.

(1) Background: To comparatively analyze the uptake of hepatocellular carcinoma (HCC) on pre-therapeutic imaging modalities, the arterial phase multi-detector computed tomography (MDCT), the parenchymal phase C-arm computed tomography (CACT), the Technetium99m-macroaggregates of human serum albumin single-photon emission computed tomography/computed tomography (SPECT/CT), and the correlation to the post-therapeutic Yttrium90 positron emission tomography/computed tomography (PET/CT) in patients with selective internal radiation therapy (SIRT). (2) Methods: Between September 2013 and December 2016, 104 SIRT procedures were performed at our institution in 74 patients with HCC not suitable for curative surgery or ablation. Twenty-two patients underwent an identical sequence of pre-therapeutic MDCT, CACT, SPECT/CT, and post-therapeutic PET/CT with a standardized diagnostic and therapeutic protocol. In these 22 patients, 25 SIRT procedures were evaluated. The uptake of the HCC was assessed using tumor-background ratio (TBR). Therefore, regions of interest were placed on the tumor and the adjacent liver tissue on MDCT (TBRMDCT), CACT (TBRCACT), SPECT/CT (TBRSPECT/CT), and PET/CT (TBRPET/CT). Comparisons were made with the Friedman test and the Nemenyi post-hoc test. Correlations were analyzed using Spearman’s Rho and the Benjamini–Hochberg method. The level of significance was p &lt, 0.05. (3) Results: TBR on MDCT (1.4 ± 0.3) was significantly smaller than on CACT (1.9 ± 0.6) and both were significantly smaller compared to SPECT/CT (4.6 ± 2.0) (pFriedman-Test &lt, 0.001, pTBRMDCT/TBRCACT = 0.012, pTBRMDCT/TBRSPECT/CT &lt, 0.001, pTBRCACT/TBRSPECT/CT &lt, 0.001). There was no significant correlation of TBR on MDCT with PET/CT (rTBRMDCT/TBRPET/CT = 0.116, p = 0.534). In contrast, TBR on CACT correlated to TBR on SPECT/CT (rTBRCACT/TBRSPECT/CT = 0.489, p = 0.004) and tended to correlate to TBR on PET/CT (rTBRCACT/TBRPET/CT =0.365, p = 0.043). TBR on SPECT/CT correlated to TBR on PET/CT (rTBRSPECT/CT/TBRPET/CT= 0.706, p &lt, 0.001) (4) Conclusion: The uptake assessment on CACT was in agreement with SPECT/CT and might be consistent with PET/CT. In contrast, MDCT was not comparable to CACT and SPECT/CT, and had no correlation with PET/CT due to the different application techniques. This emphasizes the value of the CACT, which has the potential to improve the dosimetric assessment of the tumor and liver uptake for SIRT.

The chemokine receptor CXCR4 is a promising target for molecular imaging of CXCR4+ cell types, e.g. inflammatory cells, in cardiovascular diseases. We speculated that a specific CXCR4 ligand, [68Ga]pentixafor, along with novel techniques for motion correction, would facilitate the in vivo characterization of CXCR4 expression in small culprit and nonculprit coronary atherosclerotic lesions after acute myocardial infarction by motion-corrected targeted PET/CT. CXCR4 expression was analysed ex vivo in separately obtained arterial wall specimens. [68Ga]Pentixafor PET/CT was performed in 37 patients after stent-based reperfusion for a first acute ST-segment elevation myocardial infarction. List-mode PET data were reconstructed to five different datasets using cardiac and/or respiratory gating. Guided by CT for localization, the PET signals of culprit and various groups of nonculprit coronary lesions were analysed and compared. Ex vivo, CXCR4 was upregulated in atherosclerotic lesions, and mainly colocalized with CD68+ inflammatory cells. In vivo, elevated CXCR4 expression was detected in culprit and nonculprit lesions, and the strongest CXCR4 PET signal (median SUVmax 1.96; interquartile range, IQR, 1.55–2.31) was observed in culprit coronary artery lesions. Stented nonculprit lesions (median SUVmax 1.45, IQR 1.23–1.88; P = 0.048) and hot spots in naive remote coronary segments (median SUVmax 1.34, IQR 1.23–1.74; P = 0.0005) showed significantly lower levels of CXCR4 expression. Dual cardiac/respiratory gating provided the strongest CXCR4 PET signal and the highest lesion detectability. We demonstrated the basic feasibility of motion-corrected targeted PET/CT imaging of CXCR4 expression in coronary artery lesions, which was triggered by vessel wall inflammation but also by stent-induced injury. This novel methodology may serve as a platform for future diagnostic and therapeutic clinical studies targeting the biology of coronary atherosclerotic plaque.

Aims High-energy resolution and sensitivity of novel cadmium-zinc-telluride (CZT) detector equipped SPECT systems facilitate simultaneous imaging of multiple isotopes and may enhance the detection of molecular/cellular signals. This may refine the detection of endocarditis. This study was designed to determine the feasibility and diagnostic accuracy of simultaneous imaging of inflammation with 111In-labeled white blood cells (WBCs) and myocardial perfusion with 99mTc-sestamibi, for localization of WBCs relative to the valve plane in suspected endocarditis. Methods and results A dedicated cardiac CZT camera (Discovery 530c, GE Healthcare) was employed. Anthropomorphic thorax phantom studies were followed by clinical studies in 34 patients with suspected infection of native valves ( n = 12) or implants ( n = 22). Simultaneous 111In-WBC/99mTc perfusion imaging was performed, and compared with standard 111In-WBC planar scintigraphy and SPECT-CT. Phantom studies ruled out significant radioisotope crosstalk. Downscatter on 99mTc images was not observed for 111In activity as high as 2.5*99mTc activity. In patients, image quality was superior for CZT imaging vs. conventional SPECT-CT and planar scintigraphy ( P < 0.01). Cadmium-zinc-telluride dual isotope imaging improved reader confidence for detection of inflammatory foci. Diagnostic accuracy based on surgery or Duke Criteria during follow-up was highest for CZT imaging ( P < 0.001). Conclusion Novel CZT SPECT technology improves the accuracy of molecular/cellular cardiac imaging. Simultaneous multi-isotope imaging with 111In and 99mTc is feasible and aids in the workup of suspected endocarditis.

Dose calibrators are one of the most important and most frequently used instruments for the determination of activities in nuclear medicine. For guaranteeing a constant quality of the dose calibrators' measurements, constancy checks including the examination of the system linearity have to be performed regularly, usually measured using 99mTc. The 99mTc eluate extracted from a 99Mo/99mTc generator is contaminated with molybdenum. Not accounting for the molybdenum impurity might lead to an exceed of the tolerance limit of 5% deviation to the reference value for this constancy check. The reason for this effect is the contamination of the 99mTc eluate with 99Mo, whose impact depends on both the amount of the impurity and on the total measurement time (high start activities).In this work, the influence of the molybdenum impurity on the results of the constancy check of the system linearity was investigated and maximum start activities for certain impurities were determined providing that the deviation to the reference values is below 5%.Provided that certain boundary conditions are observed, a correction of the results with respect to the molybdenum contamination is not necessary.

The sudden success of Hans Jonas's The Imperative of Responsibility (in the German original Das Prinzip Verantwortung, published in 1984) came as a surprise to the author himself and to the German intellectual and philosophical community at large. Within a decade this book, in which Jonas developed a theory of ethics for the technological age, had to be reprinted nine times. The author's name and the book's title found their way into countless speeches and addresses given at forums as diverse as ecological groups in remote villages to the Bundestag, the federal parliament in Bonn. This infusion of philosophical thought into public discourse itself was surprising, because a tradition of exchange between philosophical thought and public affairs had practically ceased to exist. Not since the time of Johann Gottlieb Fichte, whose 1807 and 1808 Reden an die deutsche Nation (Speeches to the German Nation) helped to promote national feeling against Napoleonic oppression, and Georg Friedrich Wilhelm Hegel, whose Nuremberg School Lectures of 1812 to 1816 informed the structuring of the German educational system, had the work of philosophers so influenced public life. In our own times, as an exception to the rule, Carl-Friedrich von Weizsacker, the elder brother of the former Bundesprasident Richard von Weizsacker, served for some years in the late seventies as adviser to the social-liberal government of Chancellor Helmut Schmidt. He had by then come close to acquiring the reputation of being a praeceptor Germaniae, a person whose name was never mentioned without the decorating description "the physicist and philosopher." As a physicist he had explained the operation of the nuclear fusion reaction cycle as the source of energy production in the sun; as a philosopher he had published and lectured at Hamburg University on the philosophy of nature. Weizsacker later became director of the Max Planck Institute for Research into Future Developments and World Problems and had some influence with moderate statements on the debate over nuclear energy. But even he never attained the degree of attention received by Hans Jonas during the 1980s. Timing, Approach, and Style The reasons for Jonas's truly spectacular popularity were not always philosophical in kind. He appeared on the German scene at the right moment and with the right approach. At the end of the seventies there was a vague but widespread feeling that the cultural revolution that had started in 1968 had ended in disappointment. The "principle of hope" expounded by the neomarxist philosopher Ernst Bloch had itself proved to be only a temporarily inspiring utopia, one which faded away under the realization that "the new man" was still not at hand and was unlikely ever to emerge. In contrast, Jonas described real dangers rather than engendering unfounded hopes. Although these dangers had already been foreseen by a number of prophets of the ecological movement, Jonas developed the theory and defined the problem with precision: an explosion of technology driven by human intellect and boundless economic enterprise in a limited world. He was able to explain by philosophical deduction why the present generation ought to preserve the conditions of life for the generations to come. Although the need to think of future generations had become a piety of public rhetoric by that time, no cogent answer had been formulated in response to the question of why present generations should be responsible for the unborn, who have neither been historically represented nor been subjects with personal rights in civil legislation. Did former generations--for instance, by voting for Hitler--care for the present one? Jonas avoided a short-term mentality of that kind and provided a well-founded answer with his concept of an ethics for the preservation of being (das Seiende) based on nothing other than because it is. Polemicizing against Bloch's "principle of hope," he proclaimed his "imperative of responsibility. …