TY - JOUR A1 - Gruschwitz, Philipp A1 - Hartung, Viktor A1 - Ergün, Süleyman A1 - Peter, Dominik A1 - Lichthardt, Sven A1 - Huflage, Henner A1 - Hendel, Robin A1 - Pannenbecker, Pauline A1 - Augustin, Anne Marie A1 - Kunz, Andreas Steven A1 - Feldle, Philipp A1 - Bley, Thorsten Alexander A1 - Grunz, Jan-Peter T1 - Comparison of ultrahigh and standard resolution photon-counting CT angiography of the femoral arteries in a continuously perfused in vitro model JF - European Radiology Experimental N2 - Background With the emergence of photon-counting CT, ultrahigh-resolution (UHR) imaging can be performed without dose penalty. This study aims to directly compare the image quality of UHR and standard resolution (SR) scan mode in femoral artery angiographies. Methods After establishing continuous extracorporeal perfusion in four fresh-frozen cadaveric specimens, photon-counting CT angiographies were performed with a radiation dose of 5 mGy and tube voltage of 120 kV in both SR and UHR mode. Images were reconstructed with dedicated convolution kernels (soft: Body-vascular (Bv)48; sharp: Bv60; ultrasharp: Bv76). Six radiologists evaluated the image quality by means of a pairwise forced-choice comparison tool. Kendall’s concordance coefficient (W) was calculated to quantify interrater agreement. Image quality was further assessed by measuring intraluminal attenuation and image noise as well as by calculating signal-to-noise ratio (SNR) and contrast-to-noise ratios (CNR). Results UHR yielded lower noise than SR for identical reconstructions with kernels ≥ Bv60 (p < 0.001). UHR scans exhibited lower intraluminal attenuation compared to SR (Bv60: 406.4 ± 25.1 versus 418.1 ± 30.1 HU; p < 0.001). Irrespective of scan mode, SNR and CNR decreased while noise increased with sharper kernels but UHR scans were objectively superior to SR nonetheless (Bv60: SNR 25.9 ± 6.4 versus 20.9 ± 5.3; CNR 22.7 ± 5.8 versus 18.4 ± 4.8; p < 0.001). Notably, UHR scans were preferred in subjective assessment when images were reconstructed with the ultrasharp Bv76 kernel, whereas SR was rated superior for Bv60. Interrater agreement was high (W = 0.935). Conclusions Combinations of UHR scan mode and ultrasharp convolution kernel are able to exploit the full image quality potential in photon-counting CT angiography of the femoral arteries. Relevance statement The UHR scan mode offers improved image quality and may increase diagnostic accuracy in CT angiography of the peripheral arterial runoff when optimized reconstruction parameters are chosen. Key points • UHR photon-counting CT improves image quality in combination with ultrasharp convolution kernels. • UHR datasets display lower image noise compared with identically reconstructed standard resolution scans. • Scans in UHR mode show decreased intraluminal attenuation compared with standard resolution imaging. KW - CT angiography KW - femoral arteries KW - photon-counting computed tomography (CT) KW - small pixel effect KW - ultrahigh resolution Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-357905 VL - 7 ER - TY - JOUR A1 - Gruschwitz, Philipp A1 - Hartung, Viktor A1 - Kleefeldt, Florian A1 - Peter, Dominik A1 - Lichthardt, Sven A1 - Huflage, Henner A1 - Grunz, Jan-Peter A1 - Augustin, Anne Marie A1 - Ergün, Süleyman A1 - Bley, Thorsten Alexander A1 - Petritsch, Bernhard T1 - Continuous extracorporeal femoral perfusion model for intravascular ultrasound, computed tomography and digital subtraction angiography JF - PLoS One N2 - Objectives We developed a novel human cadaveric perfusion model with continuous extracorporeal femoral perfusion suitable for performing intra-individual comparison studies, training of interventional procedures and preclinical testing of endovascular devices. Objective of this study was to introduce the techniques and evaluate the feasibility for realistic computed tomography angiography (CTA), digital subtraction angiography (DSA) including vascular interventions, and intravascular ultrasound (IVUS). Methods The establishment of the extracorporeal perfusion was attempted using one formalin-fixed and five fresh-frozen human cadavers. In all specimens, the common femoral and popliteal arteries were prepared, introducer sheaths inserted, and perfusion established by a peristaltic pump. Subsequently, we performed CTA and bilateral DSA in five cadavers and IVUS on both legs of four donors. Examination time without unintentional interruption was measured both with and without non-contrast planning CT. Percutaneous transluminal angioplasty and stenting was performed by two interventional radiologists on nine extremities (five donors) using a broad spectrum of different intravascular devices. Results The perfusion of the upper leg arteries was successfully established in all fresh-frozen but not in the formalin-fixed cadaver. The experimental setup generated a stable circulation in each procedure (ten upper legs) for a period of more than six hours. Images acquired with CT, DSA and IVUS offered a realistic impression and enabled the sufficient visualization of all examined vessel segments. Arterial cannulating, percutaneous transluminal angioplasty as well as stent deployment were feasible in a way that is comparable to a vascular intervention in vivo. The perfusion model allowed for introduction and testing of previously not used devices. Conclusions The continuous femoral perfusion model can be established with moderate effort, works stable, and is utilizable for medical imaging of the peripheral arterial system using CTA, DSA and IVUS. Therefore, it appears suitable for research studies, developing skills in interventional procedures and testing of new or unfamiliar vascular devices. KW - continuous extracorporeal femoral perfusion model KW - novel human cadaveric perfusion model KW - computed tomography angiography (CTA) KW - digital subtraction angiography (DSA) KW - intravascular ultrasound (IVUS) Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-350136 SN - 1932-6203 VL - 18 IS - 5 ER - TY - THES A1 - Peter, Dominik T1 - Reorganisation der Zellkontakte der Endothelbarriere bei der Stabilisierung durch cAMP und Rac1 T1 - Reorganization of Intercellular Junctions in Stabilization of Endothelial Barrier Functions by cAMP and Rac1 N2 - Zwischen Blutkompartiment und umliegenden Interstitium besteht eine Barriere, die durch eine einzelne Schicht aus Endothelzellen gebildet wird. Essentiell für diese Barriere, deren Funktion in der Begrenzung des Austausches von Flüssigkeit und gelösten Stoffen liegt, sind interzelluläre Junktionen, welche die Endothelzellen miteinander verbinden. Durch eine gestörte Funktion und Regulation der Endothelbarriere entstehen beim Menschen verschiedene Pathologien wie zum Beispiel Ödeme, hämorrhagischer Schlaganfall und vaskuläre Malformationen. Es ist bekannt, dass cAMP die Endothelbarriere zum Teil durch Aktivierung der kleinen GTPase Rac1 stabilisiert. Trotz der großen medizinischen Relevanz dieses Signalweges, sind die damit einhergehenden Effekte auf die interzellulären Kontakte auf ultrastruktureller Ebene weitgehend unbekannt. In mikrovaskulären Endothelzellkulturen kam es ähnlich wie in intakten Mikrogefäßen zur Stärkung der Barrierefunktion. So resultierte sowohl nach Behandlung mit Forskolin und Rolipram (F/R), welche zur Steigerung der intrazellulären cAMP-Spiegel führen, als auch nach Zugabe von 8-(4-chlorophenylthio)-2´-O-methyladenosin-3´,5´-cyclic monophosphorothioate (O-Me-cAMP), einem selektiven Aktivator des cAMP nachgeschalteten Epac/Rap1-Signalweges, ein Anstieg des TER; außerdem konnte durch beide Substanzen (F/R und O-Me-cAMP) die Aktivierung von Rac1 induziert werden. Desweiteren wurde eine verstärkte Intensität und Linearisierung des Immunfluoreszenzsignals der Zelljunktionsproteine VE-Cadherin und Claudin5 entlang der Zellgrenzen beobachtet. In der ultrastrukturellen Analyse der interzellulären Kontaktzonen-Architektur zeigte sich unter F/R- oder O-Me-cAMP-Exposition ein signifikanter Anstieg an komplexen Interdigitationen. Diese komplexen Strukturen waren dadurch charakterisiert, dass sich die Membranen benachbarter Zellen, die durch zahlreiche endotheliale Junktionen stabilisiert wurden, über vergleichsweise lange Distanzen eng aneinanderlegten, so dass ein deutlich verlängerter Interzellularspalt resultierte. Die Inhibition der Rac1-Aktivierung durch NSC-23766 verminderte die Barrierefunktion und blockierte effektiv die O-Me-cAMP-vermittelte Barrierestabilisierung und Reorganisation der Kontaktzone einschließlich der Junktionsproteine. Demgegenüber konnte die F/R-vermittelte Barrierestabilisierung durch NSC-23766 nicht beeinträchtigt werden. Parallel dazu durchgeführte Experimente mit makrovaskulären Endothelien zeigten, dass es in diesem Zelltyp unter Bedingungen erhöhter cAMP-Konzentrationen weder zur Rac1-Aktivierung noch zur Barrierestärkung oder Kontaktzonen-Reorganisation kam. Diese Ergebnisse deuten darauf hin, dass in mikrovaskulären Endothelien Rac1-vermittelte Änderungen der Kontaktzonen-Morphologie zur cAMP-induzierten Barrierestabilisierung beitragen. N2 - Evidence exists that cAMP stabilizes the endothelial barrier in part via activation of the small GTPase Rac1. However, despite the high medical relevance of this signaling pathway, the mechanistic effects on intercellular contacts on the ultrastructural level are largely unknown. In microvascular endothelial cell monolayers, in which increased cAMP strengthened barrier properties similar to intact microvessels in vivo, both forskolin and rolipram (F/R) to increase cAMP and 8-(4-chlorophenylthio)-2´-O-methyladenosine-3´,5´-cyclic monophosphorothioate (O-Me-cAMP) to stimulate exchange protein directly activated by cAMP/Ras proximate-1 (Epac/Rap1) signaling enhanced transendothelial electrical resistance (TER) and induced activation of Rac1. Concurrently, augmented immunofluorescence intensity and linearization of signals at cell borders were observed for intercellular junction proteins VE-cadherin and claudin5. Ultrastructural analysis of the intercellular contact zone morphology documented that exposure to F/R or O-Me-cAMP led to a significant increase in the proportion of contacts displaying complex interdigitations of cell borders in which membranes of neighboring cells were closely apposed over comparatively long distances and which were stabilized by numerous intercellular junctions. Interference with Rac1 activation by NSC-23766 completely abolished both barrier stabilization and contact zone reorganization in response to O-Me-cAMP whereas F/R-mediated barrier enhancement was not affected by NSC-23766. In parallel experiments using macrovascular endothelium, increased cAMP failed to induce Rac1 activation, barrier enhancement and contact zone reorganization. These results indicate that in microvascular endothelium Rac1-mediated alterations in contact zone architecture contributes to cAMP-induced barrier stabilization. KW - Endothelbarriere KW - Endothelial barrier functions KW - Adhärens-/ Occludensjunktionen KW - cAMP KW - Rho GTPase KW - Rac1 KW - Epac KW - adherens tight junctions Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-97787 ER -