New-Generation 0.55 T MRI of the Knee-Initial Clinical Experience and Comparison With 3 T MRI.

OBJECTIVES: The aim of this study was to compare the detection rate of and reader confidence in 0.55 T knee magnetic resonance imaging (MRI) findings with 3 T knee MRI in patients with acute trauma and knee pain. MATERIALS AND METHODS: In this prospective study, 0.55 T and 3 T knee MRI of 25 symptomatic patients (11 women; median age, 38 years) with suspected internal derangement of the knee was obtained in 1 setting. On the 0.55 T system, a commercially available deep learning image reconstruction algorithm was used (Deep Resolve Gain and Deep Resolve Sharp; Siemens Healthineers), which was not available on the 3 T system. Two board-certified radiologists reviewed all images independently and graded image quality parameters, noted MRI findings and their respective reporting confidence level for the presence or absence, as well as graded the bone, cartilage, meniscus, ligament, and tendon lesions. Image quality and reader confidence levels were compared ( P < 0.05 = significant), and clinical findings were correlated between 0.55 T and 3 T MRI by calculation of the intraclass correlation coefficient (ICC). RESULTS: Image quality was rated higher at 3 T compared with 0.55 T studies (each P ≤ 0.017). Agreement between 0.55 T and 3 T MRI for the detection and grading of bone marrow edema and fractures, ligament and tendon lesions, high-grade meniscus and cartilage lesions, Baker cysts, and joint effusions was perfect for both readers. Overall identification and grading of cartilage and meniscal lesions showed good agreement between high- and low-field MRI (each ICC > 0.76), with lower agreement for low-grade cartilage (ICC = 0.77) and meniscus lesions (ICC = 0.49). There was no difference in readers' confidence levels for reporting lesions of bone, ligaments, tendons, Baker cysts, and joint effusions between 0.55 T and 3 T (each P > 0.157). Reader reporting confidence was higher for cartilage and meniscal lesions at 3 T (each P < 0.041). CONCLUSIONS: New-generation 0.55 T knee MRI, with deep learning-aided image reconstruction, allows for reliable detection and grading of joint lesions in symptomatic patients, but it showed limited accuracy and reader confidence for low-grade cartilage and meniscal lesions in comparison with 3 T MRI.

TotalSegmentator: Robust Segmentation of 104 Anatomic Structures in CT Images.

Purpose: To present a deep learning segmentation model that can automatically and robustly segment all major anatomic structures on body CT images. Materials and Methods: In this retrospective study, 1204 CT examinations (from 2012, 2016, and 2020) were used to segment 104 anatomic structures (27 organs, 59 bones, 10 muscles, and eight vessels) relevant for use cases such as organ volumetry, disease characterization, and surgical or radiation therapy planning. The CT images were randomly sampled from routine clinical studies and thus represent a real-world dataset (different ages, abnormalities, scanners, body parts, sequences, and sites). The authors trained an nnU-Net segmentation algorithm on this dataset and calculated Dice similarity coefficients to evaluate the model's performance. The trained algorithm was applied to a second dataset of 4004 whole-body CT examinations to investigate age-dependent volume and attenuation changes. Results: The proposed model showed a high Dice score (0.943) on the test set, which included a wide range of clinical data with major abnormalities. The model significantly outperformed another publicly available segmentation model on a separate dataset (Dice score, 0.932 vs 0.871; P < .001). The aging study demonstrated significant correlations between age and volume and mean attenuation for a variety of organ groups (eg, age and aortic volume [rs = 0.64; P < .001]; age and mean attenuation of the autochthonous dorsal musculature [rs = -0.74; P < .001]). Conclusion: The developed model enables robust and accurate segmentation of 104 anatomic structures. The annotated dataset (https://doi.org/10.5281/zenodo.6802613) and toolkit (https://www.github.com/wasserth/TotalSegmentator) are publicly available.Keywords: CT, Segmentation, Neural Networks Supplemental material is available for this article. © RSNA, 2023See also commentary by Sebro and Mongan in this issue.

Structural and functional retinal alterations in patients with paranoid schizophrenia.

Ophthalmological methods have increasingly raised the interest of neuropsychiatric specialists. While the integrity of the retinal cell functions can be evaluated with the electroretinogram (ERG), optical coherence tomography (OCT) allows a structural investigation of retinal layer thicknesses. Previous studies indicate possible functional and structural retinal alterations in patients with schizophrenia. Twenty-five patients with paranoid schizophrenia and 25 healthy controls (HC) matched for age, sex, and smoking status participated in this study. Both, ERG and OCT were applied to obtain further insights into functional and structural retinal alterations. A significantly reduced a-wave amplitude and thickness of the corresponding para- and perifoveal outer nuclear layer (ONL) was detected in patients with paranoid schizophrenia with a positive correlation between both measurement parameters. Amplitude and peak time of the photopic negative response (PhNR) and thickness of the parafoveal ganglion cell layer (GCL) were decreased in patients with schizophrenia compared to HC. Our results show both structural and functional retinal differences between patients with paranoid schizophrenia and HC. We therefore recommend the comprehensive assessment of the visual system of patients with schizophrenia, especially to further investigate the effect of antipsychotic medication, the duration of illness, or other factors such as inflammatory or neurodegenerative processes. Moreover, longitudinal studies are required to investigate whether the functional alterations precede the structural changes.

Quantification and reduction of cross-vendor variation in multicenter DWI MR imaging: results of the Cancer Core Europe imaging task force.

OBJECTIVES: In the Cancer Core Europe Consortium (CCE), standardized biomarkers are required for therapy monitoring oncologic multicenter clinical trials. Multiparametric functional MRI and particularly diffusion-weighted MRI offer evident advantages for noninvasive characterization of tumor viability compared to CT and RECIST. A quantification of the inter- and intraindividual variation occurring in this setting using different hardware is missing. In this study, the MRI protocol including DWI was standardized and the residual variability of measurement parameters quantified. METHODS: Phantom and volunteer measurements (single-shot T2w and DW-EPI) were performed at the seven CCE sites using the MR hardware produced by three different vendors. Repeated measurements were performed at the sites and across the sites including a traveling volunteer, comparing qualitative and quantitative ROI-based results including an explorative radiomics analysis. RESULTS: For DWI/ADC phantom measurements using a central post-processing algorithm, the maximum deviation could be decreased to 2%. However, there is no significant difference compared to a decentralized ADC value calculation at the respective MRI devices. In volunteers, the measurement variation in 2 repeated scans did not exceed 11% for ADC and is below 20% for single-shot T2w in systematic liver ROIs. The measurement variation between sites amounted to 20% for ADC and < 25% for single-shot T2w. Explorative radiomics classification experiments yield better results for ADC than for single-shot T2w. CONCLUSION: Harmonization of MR acquisition and post-processing parameters results in acceptable standard deviations for MR/DW imaging. MRI could be the tool in oncologic multicenter trials to overcome the limitations of RECIST-based response evaluation. KEY POINTS: • Harmonizing acquisition parameters and post-processing homogenization, standardized protocols result in acceptable standard deviations for multicenter MR-DWI studies. • Total measurement variation does not to exceed 11% for ADC in repeated measurements in repeated MR acquisitions, and below 20% for an identical volunteer travelling between sites. • Radiomic classification experiments were able to identify stable features allowing for reliable discrimination of different physiological tissue samples, even when using heterogeneous imaging data.

The Discriminative Power and Stability of Radiomics Features With Computed Tomography Variations: Task-Based Analysis in an Anthropomorphic 3D-Printed CT Phantom.

OBJECTIVES: The aims of this study were to determine the stability of radiomics features against computed tomography (CT) parameter variations and to study their discriminative power concerning tissue classification using a 3D-printed CT phantom based on real patient data. MATERIALS AND METHODS: A radiopaque 3D phantom was developed using real patient data and a potassium iodide solution paper-printing technique. Normal liver tissue and 3 lesion types (benign cyst, hemangioma, and metastasis) were manually annotated in the phantom. The stability and discriminative power of 86 radiomics features were assessed in measurements taken from 240 CT series with 8 parameter variations of reconstruction algorithms, reconstruction kernels, slice thickness, and slice spacing. Pairwise parameter group and pairwise tissue class comparisons were performed using Wilcoxon signed rank tests. RESULTS: In total, 19,264 feature stability tests and 8256 discriminative power tests were performed. The 8 CT parameter variation pairwise group comparisons had statistically significant differences on average in 78/86 radiomics features. On the other hand, 84% of the univariate radiomics feature tests had a successful and statistically significant differentiation of the 4 classes of liver tissue. The 86 radiomics features were ranked according to the cumulative sum of successful stability and discriminative power tests. CONCLUSIONS: The differences in radiomics feature values obtained from different types of liver tissue are generally greater than the intraclass differences resulting from CT parameter variations.

Joint Imaging Platform for Federated Clinical Data Analytics.

PURPOSE: Image analysis is one of the most promising applications of artificial intelligence (AI) in health care, potentially improving prediction, diagnosis, and treatment of diseases. Although scientific advances in this area critically depend on the accessibility of large-volume and high-quality data, sharing data between institutions faces various ethical and legal constraints as well as organizational and technical obstacles. METHODS: The Joint Imaging Platform (JIP) of the German Cancer Consortium (DKTK) addresses these issues by providing federated data analysis technology in a secure and compliant way. Using the JIP, medical image data remain in the originator institutions, but analysis and AI algorithms are shared and jointly used. Common standards and interfaces to local systems ensure permanent data sovereignty of participating institutions. RESULTS: The JIP is established in the radiology and nuclear medicine departments of 10 university hospitals in Germany (DKTK partner sites). In multiple complementary use cases, we show that the platform fulfills all relevant requirements to serve as a foundation for multicenter medical imaging trials and research on large cohorts, including the harmonization and integration of data, interactive analysis, automatic analysis, federated machine learning, and extensibility and maintenance processes, which are elementary for the sustainability of such a platform. CONCLUSION: The results demonstrate the feasibility of using the JIP as a federated data analytics platform in heterogeneous clinical information technology and software landscapes, solving an important bottleneck for the application of AI to large-scale clinical imaging data.

Analysis of user behavior on the website of a university eye hospital in Germany.

Medical information websites are usually targeted toward patients, physicians, and medical students. Most of the latest studies researched the usability of such websites. However, reports on user numbers and behavior are rare.The goal of our study is to analyze the utility of a website of a large tertiary referral center in ophthalmology in terms of various target audiences (patients, applicants, medical students, referring ophthalmologists).The web access data from our institutional website was assessed with Google Analytics. Data collection started in 2016.From 2016 to 2018, we counted a total of 763,942 page views. The overall number of users dropped from 81,572 to 67,740. This drop's onset correlates with a change in the website structure. All target audience pages received constant traffic from 2016 to 2019, with the patients' and doctors' sites attracting the most traffic. The pages for medical students and job applicants, although not viewed often, revealed a long session duration.Our website is used by all our target audiences. The behavior and the user numbers of each target group differ. Changes to a website's structure can influence the number of users and their behavior. It is not possible to make a direct comparison to other institutions' websites as there are so few similar reports available. By adding more parameters to the analytics profile in a prospective setting, more detailed analyses of user behavior may be possible in the future.

Temperature and concentration calibration of aqueous polyvinylpyrrolidone (PVP) solutions for isotropic diffusion MRI phantoms.

To use the "apparent diffusion coefficient" (Dapp) as a quantitative imaging parameter, well-suited test fluids are essential. In this study, the previously proposed aqueous solutions of polyvinylpyrrolidone (PVP) were examined and temperature calibrations were obtained. For example, at a temperature of 20°C, Dapp ranged from 1.594 (95% CI: 1.593, 1.595) µm2/ms to 0.3326 (95% CI: 0. 3304, 0.3348) µm2/ms for PVP-concentrations ranging from 10% (w/w) to 50% (w/w) using K30 polymer lengths. The temperature dependence of Dapp was found to be so strong that a negligence seems not advisable. The temperature dependence is descriptively modelled by an exponential function exp(c2 (T - 20°C)) and the determined c2 values are reported, which can be used for temperature calibration. For example, we find the value 0.02952 K-1 for 30% (w/w) PVP-concentration and K30 polymer length. In general, aqueous PVP solutions were found to be suitable to produce easily applicable and reliable Dapp-phantoms.

Individual Differences in Scotopic Visual Acuity and Contrast Sensitivity: Genetic and Non-Genetic Influences.

Despite the large amount of variation found in the night (scotopic) vision capabilities of healthy volunteers, little effort has been made to characterize this variation and factors, genetic and non-genetic, that influence it. In the largest population of healthy observers measured for scotopic visual acuity (VA) and contrast sensitivity (CS) to date, we quantified the effect of a range of variables on visual performance. We found that young volunteers with excellent photopic vision exhibit great variation in their scotopic VA and CS, and this variation is reliable from one testing session to the next. We additionally identified that factors such as Circadian preference, iris color, astigmatism, depression, sex and education have no significant impact on scotopic visual function. We confirmed previous work showing that the amount of time spent on the vision test influences performance and that laser eye surgery results in worse scotopic vision. We also showed a significant effect of intelligence and photopic visual performance on scotopic VA and CS, but all of these variables collectively explain <30% of the variation in scotopic vision. The wide variation seen in young healthy volunteers with excellent photopic vision, the high test-retest agreement, and the vast majority of the variation in scotopic vision remaining unexplained by obvious non-genetic factors suggests a strong genetic component. Our preliminary genome-wide association study (GWAS) of 106 participants ruled out any common genetic variants of very large effect and paves the way for future, larger genetic studies of scotopic vision.

ISCEV Standard for full-field clinical electroretinography (2015 update).

This document, from the International Society for Clinical Electrophysiology of Vision (ISCEV), presents an updated and revised ISCEV Standard for full-field clinical electroretinography (ffERG or simply ERG). The parameters for Standard flash stimuli have been revised to accommodate a variety of light sources including gas discharge lamps and light emitting diodes. This ISCEV Standard for clinical ERGs specifies six responses based on the adaptation state of the eye and the flash strength: (1) Dark-adapted 0.01 ERG (rod ERG); (2) Dark-adapted 3 ERG (combined rod-cone standard flash ERG); (3) Dark-adapted 3 oscillatory potentials; (4) Dark-adapted 10 ERG (strong flash ERG); (5) Light-adapted 3 ERG (standard flash "cone" ERG); and (6) Light-adapted 30 Hz flicker ERG. ISCEV encourages the use of additional ERG protocols for testing beyond this minimum standard for clinical ERGs.

Contrast sensitivity with bifocal intraocular lenses is halved, as measured with the Freiburg Vision Test (FrACT), yet patients are happy.

BACKGROUND: As the desire for spectacle independence following cataract surgery grows, so does interest in the implantation of multifocal intraocular lenses. However, glare phenomena, reduced intermediate vision and loss of image quality are known problems associated with this new generation of lenses. We compared the functional results achieved by the implantation of the diffractive-refractive Acri.LISA 366D lenses to those achieved from implanting monofocal Acri.Smart 46LC lenses. METHODS: In a retrospective data analysis we followed ten patients who received bifocal intraocular lenses (Acri.LISA 366D) and ten patients who received monofocal intraocular lenses (Acri.Smart 46LC). Lenses were always implanted in both eyes. In each group we assessed visual acuity and contrast sensitivity with the Freiburg Vison Test (FrACT) at multiple distances ranging from 0.5 to 5 m. Additionally, we assessed near vision with the Birkhaeuser charts. We also evaluated photopic phenomena and patient satisfaction using a standardised questionnaire. One patient in the Acri.LISA group and six patients in the control group missed the recommended follow-up visits. RESULTS: We found good uncorrected distance and near visual acuity. Only three of nine patients wore glasses occasionally. Although their contrast sensitivity decreased by a factor of two compared to the control group, patients did not complain about visual disturbances. Patient satisfaction was predominantly high following Acri.LISA 366D implantation. CONCLUSIONS: With the Acri.LISA 366D, patients demonstrate excellent near and distance vision, albeit with reduced contrast sensitivity. Acri Lisa is a viable option in patients that do not want to depend on spectacles.

Safety and efficacy of subretinal visual implants in humans: methodological aspects.

BACKGROUND: Replacing the function of visual pathway neurons by electronic implants is a novel approach presently explored by various groups in basic research and clinical trials. The novelty raises unexplored methodological aspects of clinical trial design that may require adaptation and validation. METHODS: We present procedures of efficacy and safety testing for subretinal visual implants in humans, as developed during our pilot trial 2005 to 2009 and multi-centre clinical trial since 2010. RESULTS: Planning such a trial requires appropriate inclusion and exclusion criteria. For subretinal electronic visual implants, patients with photoreceptor degeneration are the target patient group, whereas presence of additional diseases affecting clear optic media or the visual pathway must be excluded. Because sham surgery is not possible, a masked study design with implant power ON versus OFF is necessary. Prior to the efficacy testing by psychophysical tests, the implant's technical characteristics have to be controlled via electroretinography (ERG). Moreover the testing methods require adaptation to the particular technology. We recommend standardised tasks first to determine the light perception thresholds, light localisation and movement detection, followed by grating acuity and vision acuity test via Landolt C rings. A laboratory setup for assessing essential activities of daily living is presented. Subjective visual experiences with the implant in a natural environment, as well as questionnaires and psychological counselling are further important aspects. CONCLUSIONS: A clinical trial protocol for artificial vision in humans, which leads a patient from blindness to the state of very low vision is a challenge and cannot be defined completely prior to the study. Available tests of visual function may not be sufficiently suited for efficacy testing of artificial vision devices. A protocol based on experience with subretinal visual implants in 22 patients is presented that has been found adequate to monitor safety and efficacy.

Gucy2f zebrafish knockdown--a model for Gucy2d-related leber congenital amaurosis.

Mutations in retinal-specific guanylate cyclase (Gucy2d) are associated with Leber congenital amaurosis-1 (LCA1). Zebrafish offer unique advantages relative to rodents, including their excellent color vision, precocious retinal development, robust visual testing strategies, low cost, relatively easy transgenesis and shortened experimental times. In this study we will demonstrate the feasibility of using gene-targeting in the zebrafish as a model for the photoreceptor-specific GUCY2D-related LCA1, by reporting the visual phenotype and retinal histology resulting from Gucy2f knockdown. Gucy2f zebrafish LCA-orthologous cDNA was identified and isolated by PCR amplification. Its expression pattern was determined by whole-mount in-situ hybridization and its function was studied by gene knockdown using two different morpholino-modified oligos (MO), one that blocks translation of Gucy2f and one that blocks splicing of Gucy2f. Visual function was assessed with an optomotor assay on 6-days-post-fertilization larvae, and by analyzing changes in retinal histology. Gucy2f knockdown resulted in significantly lower vision as measured by the optomotor response compared with uninjected and control MO-injected zebrafish larvae. Histological changes in the Gucy2f-knockdown larvae included loss and shortening of cone and rod outer segments. A zebrafish model of Gucy2f-related LCA1 displays early visual dysfunction and photoreceptor layer dystrophy. This study serves as proof of concept for the use of zebrafish as a simple, inexpensive model with excellent vision on which further study of LCA-related genes is possible.

A primer on common statistical errors in clinical ophthalmology.

Although biomedical statistics is part of any scientific curriculum, a review of the current scientific literature indicates that statistical data analysis is an area that frequently needs improvement. To address this, we here cover some of the most common problems in statistical analysis, with an emphasis on an intuitive, tutorial approach rather than a rigorous, proof-based one. The topics covered in this manuscript are whether to enter eyes or patients into the analysis, issues related to multiple testing, pitfalls surrounding the correlation coefficient (causation, insensitivity to patterns, range confounding, unsuitability for method comparisons), and when to use standard deviation (SD) versus standard error of the mean (SEM) "antennas" on graphs.

[Problems of pain measurement and pain therapy in the elderly]. / Problemfelder in der Schmerzmessung und Schmerztherapie im Alter.

Due to complex physical and psychological changes in aging, pain measurement and therapeutic treatment of older and geriatric patients present a special challenge. Nevertheless, even for this category of patients, good treatment results are achievable if age-related particulars and problems are consistently heeded and accounted for. That includes adverse sensory and cognitive effects as much as multimorbidity and the polypharmacy that is frequently related to it. An essential prerequisite for adequate pain therapeutic care in elderly patients is consistent pain measurement. While numerical and verbal scales have also proven their usefulness for patients in advanced age who are not cognitively impaired, instruments must be applied for older people with communicative and/or cognitive restrictions with which the observed behavior of those involved can be surveyed in a multidimensional way.

Vergence position of rest: spontaneous variability.

BACKGROUND: We determined the vergence position of rest (horizontal component) in two sessions, 1 to 6 weeks apart. Each session contained 8 trials. Twenty observers with normal eyes looked through Risley prisms that allowed a continuous modulation of their strength. We asked the observers to look at a fully fusionable picture, and to adjust the prisms such that viewing appeared most relaxing. The viewing distances were 400 cm and 50 cm. RESULTS: The standard deviation among the 8 trials of each session, averaged over the two sessions, the viewing distances of 400 cm and 50 cm, and the 20 observers, was + or -1.4 prism dioptres (cm/m). From the first session to the second, many observers changed the preferred prism significantly. At a viewing distance of 400 cm, 10 of 20 observers changed their preferred prism by more than 1.0 prism diopter, up to 3.3 prism diopters. At a viewing distance of 50 cm, 11 of 20 observers changed their preferred prism by more than 1.0 prism diopter, up to 5.1 prism diopters. CONCLUSIONS: The prismatic strength estimated as being most relaxing can be very variable. Before considering a prescription, the practitioner should determine whether the preferred prismatic strength remains reasonably stable. To ascertain this consistency, more than one session seems to be necessary.

Electrophysiological evaluation of retinal photoreceptor function after repeated bevacizumab injections.

Bevacizumab (Avastin, Genentech) was one of the first anti-VEGF substances used to treat macular edema or choroidal neovascularization in patients with vascular ocular pathologies. However, only few studies evaluate the safety of intravitreal bevacizumab injections in regard to retinal photoreceptor function. We evaluated retinal function after repeated (2-3) monthly injections of bevacizumab in a prospective case series of 10 patients with various retinal diseases. Study endpoints were visual acuity (VA) using ETDRS charts and 3 full-field electroretinography sessions with a flash intensity range of 0.0005-2 cds/m(2). V-log-I b-wave amplitudes were fitted by a Naka-Rushton model. No significant changes in scotopic or photopic ERG measures were observed between baseline ERG and last follow-up ERG. Individual patients showed transient alterations of ERG measures on the first follow-up visit. Mean visual acuity was stable over the time course of the study (logMAR = 0.42 at baseline and logMAR = 0.48 at last follow-up). In conclusion, three monthly repeated injections of bevacizumab do not affect mid-term electrophysiological retinal function. Transient alterations in ERG readings of individual patients 1 week after intravitreal bevacizumab injection may be attributed to short-term disruption of the retinal equilibrium through the trauma of injection. Evaluation of patients receiving more than three injections of anti-VEGF substances should be the focus of future studies.

Dose-response relationship in inferior oblique muscle recession.

BACKGROUND: Recession of the inferior oblique muscle is a widely applied operation in the treatment of strabismus sursoadductorius. In this retrospective study, the dose-response relationship of this procedure was determined in order to improve surgical outcomes. In particular, the effect of an additional anteroposition of the operated muscle was analysed, as well as differences between short and long term results. METHODS: This retrospective study included 37 patients. Inclusion criteria were unilateral strabismus sursoadductorius and normal retinal correspondence. Exclusion criteria comprised previous ocular muscle surgery and any ocular or orbital disease. Nineteen patients had received an additional anteroposition of the muscle. Patients were examined at a tangent screen pre-operatively and 1 day post-operatively (short-term effect). Sixteen patients underwent an additional examination 3 months post-operatively (long-term effect). Changes of vertical, torsional and horizontal deviations, measured in different positions of gaze, were related to the surgical dose in order to calculate the dose-response relationship by linear regression analysis. RESULTS: Surgery always reduced preoperative deviations. The short-term vertical dose-response without/with anteroposition was 0.6 degrees /0.5 degrees per mm in primary gaze and 1.2 degrees /1.1 degrees per mm in adduction. The short-term torsional dose-response without/with anteroposition was 0.8 degrees /0.5 degrees per mm in primary gaze. Three months later, the vertical effect had remained constant, whereas the torsional effect had decreased to 0.6 degrees /0.1 degrees per mm. Variance was high, e.g. the standard deviation of the short-term effect for the vertical deviation in adduction was 2.5 degrees . CONCLUSIONS: Despite the large variation of effects, a dose-response relationship could be established, facilitating surgical planning. Large vertical deviations with small excyclodeviation are an indication for additional anteropositioning. The torsional effect of inferior oblique muscle recessions can diminish over time.

PI 3-kinase pathway is responsible for antiapoptotic effects of atrial natriuretic peptide in rat liver transplantation.

AIM: To investigate the in vivo effect of atrial natriuretic peptide (ANP) and its signaling pathway during orthotopic rat liver transplantation. METHODS: Rats were infused with NaCl, ANP (5 microg/kg), wortmannin (WM, 16 microg/kg), or a combination of both for 20 min. Livers were stored in UW solution (4 degrees C) for 24 h, transplanted and reperfused. Apoptosis was examined by caspase-3 activity and TUNEL staining. Phosphorylation of Akt and Bad was visualized by Western blotting and phospho-Akt-localization by confocal microscopy. RESULTS: ANP-pretreatment decreased caspase-3 activity and TUNEL-positive cells after cold ischemia, indicating antiapoptotic effects of ANP in vivo. The antiapoptotic signaling of ANP was most likely caused by phosphorylation of Akt and Bad, since pretreatment with PI 3-kinase inhibitor WM abrogated the ANP-induced reduction of caspase-3 activity. Interestingly, analysis of liver tissue by confocal microscopy showed translocation of phosphorylated Akt to the plasma membrane of hepatocytes evoked by ANP. CONCLUSION: ANP activates the PI-3-kinase pathway in the liver in vivo leading to phosphorylation of Bad, an event triggering antiapoptotic signaling cascade in ischemic liver.