Bennet Hensen

Kidney Transplantation: Multiparametric Functional Magnetic Resonance Imaging for Assessment of Renal Allograft Pathophysiology in Mice.

ObjectivesThe aims of this experimental study were to investigate renal allograft pathophysiology by multiparametric functional magnetic resonance imaging (MRI) and to directly correlate MRI parameters with renal histopathology in mouse models of allogenic and isogenic kidney transplantation (ktx). Materials and MethodsAllograft rejection was induced by transplantation of C57BL/6 (B6) donor kidneys into BALB/c recipients (allogenic ktx). B6 mice that received B6 kidneys served as controls (isogenic ktx). Three weeks after ktx, MRI was performed using a 7-T small-animal scanner. Flow sensitive alternating inversion recovery echoplanar imaging arterial spin labeling, multiecho turbo spin echo, and diffusion-weighted imaging sequences were acquired. Maps of renal perfusion, T2 and T1 relaxation times, and apparent diffusion coefficients were calculated. Histological changes in the kidney were evaluated according to Banff criteria. Renal cell infiltrates and fibrosis were quantified by immunohistochemistry. Differences between groups were assessed using the Mann-Whitney U test, and the correlation of MRI parameters with renal histopathology was determined by Spearman correlation analysis. ResultsAfter allogenic, but not isogenic, ktx, animals developed acute allograft rejection. Allogenic grafts were infiltrated by macrophages and T-lymphocytes and exhibited marked renal fibrosis. Magnetic resonance imaging revealed stronger impairment of renal perfusion (56 ± 7 vs 293 ± 44 mL/[min × 100 g]; P < 0.01) and more pronounced increases in T2 (60.1 ± 2.0 vs 45.7 ± 1.2 milliseconds, P < 0.01) and T1 relaxation times (1938 ± 53 vs 1350 ± 27 milliseconds, P < 0.01) in allogenic than in isogenic kidneys. Apparent diffusion coefficient was reduced to 1.39 ± 0.14 × 10−3 mm2/s in kidneys with an acute rejection and was 1.83 ± 0.05 × 10−3 mm2/s in isogenic kidneys without rejection (P < 0.05). Magnetic resonance imaging parameters significantly correlated with the amount of cellular infiltration and renal fibrosis observed histologically. ConclusionsFunctional MRI allows detection of acute renal allograft rejection after allogenic ktx in mice. Functional MRI parameters correlate with cell infiltrates and fibrosis. Thus, MRI may be used noninvasively and longitudinally to investigate mechanisms of renal allograft rejection and evaluate novel therapeutic strategies in experimental studies.

C5AR2 Deficiency Shows Enhanced Regeneration Capacity after Renal Ischemia Reperfusion Injury via AKT and FGF Dependent Mechanisms

Background Ischemia reperfusion injury (IRI) contributes to acute kidney injury (AKI) and to delayed graft function which can be up to 50% due to prolonged cold ischemia time kidney transplantation. A hallmark of IRI is activation of the comeplement system but so far, there is little known about the different roles of the two C5a receptors (C5aR1 versus C5aR2). In this study C5aR1 and C5aR2 deficient mice were investigated used in the renal IRI model and different pathological responses were by longitudinal monitoring. Methods Unilateral IRI of 45 min was done in C5aR1, C5aR2 -/- and wild type mice (WT). Renal morphology, inflammation, regeneration and renal fibrosis were investigated by immunohistochemistry and qPCR. To measure renal perfusion functional magnetic resonance imaging (MRI) was done at day 1, 7 and 21. Renal tissue was processed for high content antibody microarrays and differential total protein and phospho protein expression was analyzed. Based on the proteomics results AKT and p-AKT protein expression in the tissue was investigated by Western blotting. Results Extensive renal fibrosis was detected in WT mice within 3 weeks after IRI whereas C5aR deficienct mice showed partial protection. Especially, C5aR2 deficient mice showed enhanced tubular proliferation measured by Ki-67 expression and improved renal perfusion over time. Macrophage infiltration was attenuated in C5aR2 -/- mice and the transcript of the anti-inflammatory cytokine IL-10 was significantly up-regulated. Moreover, proteomics revealed significantly enhanced phosphorylation of the pro-angiogenic FGF1 in C5aR2-/- IRI kidneys at d1. In addition, total AKT protein and consecutively also phospho-AKT was significantly higher in C5aR2-/- compared to the other mouse strains. Conclusion C5aR2 deficient mice have enhanced p-FGF and p-AKT levels after IRI which might have contributed to improved regeneration of peritubular capillaries, tubular epithelial cells and better renal perfusion.

Initial Experience with Digital Patient Briefing in Computed Tomography

PURPOSE  To assess digital patient briefing as an alternative to conventional paper documentation. MATERIALS AND METHODS  502 patients with a planned computed tomography (CT) examination were selected for digital patient briefing using the E-ConsentPro software from Thieme Compliance on an iPad by Apple (Cupertino, California, USA). For the analysis, three age groups were formed. The time required for the patient briefing, the number of open questions as well as the time needed for discussion with physicians were determined. Students t-test was performed to assess statistical significance. RESULTS  There was no significant difference between patient age and briefing time which was about 20 minutes on average. The number of open or unclear questions increased with patient age. While patients younger than 30 years of age had about 2 open questions, patients over 30 and 60 years had about 4 and 5 questions, respectively. The total time needed for discussion with physicians was less than 2 minutes on average. A significant difference in the time required for discussion with physicians could not be observed between the individual age groups. CONCLUSION  Tablet-based digital briefing allows the storage of patient documents with reasonable time and effort. Furthermore, it minimizes the risk of data loss. KEY POINTS   · Tablet-based digital patient briefing in computed tomography can be performed with reasonable time and effort.. · The time required for tablet-based patient briefing is independent of patient age.. · The cost-benefit analysis presents a significant improvement in digital patient briefing compared to the paper-based process.. CITATION FORMAT · Alikhani B, Hensen B, Grosser A et al. Initial Experience with Digital Patient Briefing in Computed Tomography. Fortschr Röntgenstr 2019; 191: 540 - 546.

Percutaneous MR-guided interventions using an optical Moiré Phase tracking system: Initial results

The aim of this study was the development and evaluation of a real-time guidance support using optical Moiré Phase Tracking (MPT) for magnetic resonance (MR) guided percutaneous interventions. A gradient echo sequence, capable of real-time position updates by the MPT system, was modified to enable needle guidance based on four rigidly attached MPT markers at the back of a needle. Two perpendicular imaging planes were automatically aligned along the calibrated needle and centered at its tip. For user guidance, additional information about the needle trajectory and the tip to target distance were added as image overlay. Both, images and guiding information were displayed on the in-room monitor to facilitate MR guided interventions. The guidance support was evaluated by four experienced interventional radiologists and four novices targeting rubber O-rings embedded in a custom-made phantom on a 3T wide-bore MRI system (80 punctures). The skin to target time, user error, system error and total error were analyzed. The mean skin to target time was 146s±68s with no statistically significant difference between experts and novices. A low mean user error (0.91mm±0.43mm), system error (0.53mm±0.27mm) and total error (0.99mm±0.47mm) was reached in all directions. No statistically significant difference in user error, system error and total error could be found between experts and novices. The presented tracking and image guidance system combined with the user interface offers continuous and interactive control of the imaging plane while puncturing in the magnet enabling accurate real-time feedback for both, experienced and non-experienced users.

Enhanced activation of interleukin-10, heme oxygenase-1, and AKT in C5aR2-deficient mice is associated with protection from ischemia reperfusion injury–induced inflammation and fibrosis

Severe ischemia reperfusion injury (IRI) results in rapid complement activation, acute kidney injury and progressive renal fibrosis. Little is known about the roles of the C5aR1 and C5aR2 complement receptors in IRI. In this study C5aR1-/- and C5aR2-/- mice were compared to the wild type in a renal IRI model leading to renal fibrosis. C5a receptor expression, kidney morphology, inflammation, and fibrosis were measured in different mouse strains one, seven and 21 days after IRI. Renal perfusion was evaluated by functional magnetic resonance imaging. Protein abundance and phosphorylation were assessed with high content antibody microarrays and Western blotting. C5aR1 and C5aR2 were increased in damaged tubuli and even more in infiltrating leukocytes after IRI in kidneys of wild-type mice. C5aR1-/- and C5aR2-/- animals developed less IRI-induced inflammation and showed better renal perfusion than wild-type mice following IRI. C5aR2-/- mice, in particular, had enhanced tubular and capillary regeneration with less renal fibrosis. Anti-inflammatory IL-10 and the survival/growth kinase AKT levels were especially high in kidneys of C5aR2-/- mice following IRI. LPS caused bone marrow-derived macrophages from C5aR2-/- mice to release IL-10 and to express the stress response enzyme heme oxygenase-1. Thus, C5aR1 and C5aR2 have overlapping actions in which the kidneys of C5aR2-/- mice regenerate better than those in C5aR1-/- mice following IRI. This is mediated, at least in part, by differential production of IL-10, heme oxygenase-1 and AKT.

Projector-based augmented reality system for interventional visualization inside MRI scanners

Navigation support in interventional magnetic resonance imaging (MRI) is separated from the operating field, which makes it difficult to interpret positions and orientations and to coordinate the necessary hand movements.

Concepts for augmented reality visualisation to support needle guidance inside the MRI

During MRI-guided interventions, navigation support is often separated from the operating field on displays, which impedes the interpretation of positions and orientations of instruments inside the patients body as well as hand–eye coordination. To overcome these issues projector-based augmented reality can be used to support needle guidance inside the MRI bore directly in the operating field. The authors present two visualisation concepts for needle navigation aids which were compared in an accuracy and usability study with eight participants, four of whom were experienced radiologists. The results show that both concepts are equally accurate (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}

Wireless video transmission into the MRI magnet room: implementation and evaluation at 1.5T, 3T and 7T

2.0 \pm 0.6

Sarcopenia as a marker for prediction of long-term survival following radical cystectomy.

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Touchless interaction with software in interventional radiology and surgery: a systematic literature review.

1.7 \pm 0.5\, {\rm mm}