Real-World and Regulatory Perspectives of Artificial Intelligence in Cardiovascular Imaging

Recent progress in digital health data recording, advances in computing power, and methodological approaches that extract information from data as artificial intelligence are expected to have a disruptive impact on technology in medicine. One of the potential benefits is the ability to extract new and essential insights from the vast amount of data generated during health care delivery every day. Cardiovascular imaging is boosted by new intelligent automatic methods to manage, process, segment, and analyze petabytes of image data exceeding historical manual capacities. Algorithms that learn from data raise new challenges for regulatory bodies. Partially autonomous behavior and adaptive modifications and a lack of transparency in deriving evidence from complex data pose considerable problems. Controlling new technologies requires new controlling techniques and ongoing regulatory research. All stakeholders must participate in the quest to find a fair balance between innovation and regulation. The regulatory approach to artificial intelligence must be risk-based and resilient. A focus on unknown emerging risks demands continuous surveillance and clinical evaluation during the total product life cycle. Since learning algorithms are data-driven, high-quality data is fundamental for good machine learning practice. Mining, processing, validation, governance, and data control must account for bias, error, inappropriate use, drifts, and shifts, particularly in real-world data. Regulators worldwide are tackling twenty-first century challenges raised by “learning” medical devices. Ethical concerns and regulatory approaches are presented. The paper concludes with a discussion on the future of responsible artificial intelligence

Estimation of central blood pressure waveform from femoral blood pressure waveform by blind sources separation

BackgroundCentral blood pressure (cBP) is a better indicator of cardiovascular morbidity and mortality than peripheral BP (pBP). However, direct cBP measurement requires invasive techniques and indirect cBP measurement is based on rigid and empirical transfer functions applied to pBP. Thus, development of a personalized and well-validated method for non-invasive derivation of cBP from pBP is necessary to facilitate the clinical routine. The purpose of the present study was to develop a novel blind source separation tool to separate a single recording of pBP into their pressure waveforms composing its dynamics, to identify the compounds that lead to pressure waveform distortion at the periphery, and to estimate the cBP. The approach is patient-specific and extracts the underlying blind pressure waveforms in pBP without additional brachial cuff calibration or any a priori assumption on the arterial model.MethodsThe intra-arterial femoral BPfe and intra-aortic pressure BPao were anonymized digital recordings from previous routine cardiac catheterizations of eight patients at the German Heart Centre Berlin. The underlying pressure waveforms in BPfe were extracted by the single-channel independent component analysis (SCICA). The accuracy of the SCICA model to estimate the whole cBP waveform was evaluated by the mean absolute error (MAE), the root mean square error (RMSE), the relative RMSE (RRMSE), and the intraclass correlation coefficient (ICC). The agreement between the intra-aortic and estimated parameters including systolic (SBP), diastolic (DBP), mean arterial pressure (MAP), and pulse pressure (PP) was evaluated by the regression and Bland–Altman analyses.ResultsThe SCICA tool estimated the cBP waveform non-invasively from the intra-arterial BPfe with an MAE of 0.159 ± 1.629, an RMSE of 5.153 ± 0.957 mmHg, an RRMSE of 5.424 ± 1.304%, and an ICC of 0.94, as well as two waveforms contributing to morphological distortion at the femoral artery. The regression analysis showed a strong linear trend between the estimated and intra-aortic SBP, DBP, MAP, and PP with high coefficient of determination R2 of 0.98, 0.99, 0.99, and 0.97 respectively. The Bland–Altman plots demonstrated good agreement between estimated and intra-aortic parameters with a mean error and a standard deviation of difference of −0.54 ± 2.42 mmHg [95% confidence interval (CI): −5.28 to 4.20] for SBP, −1.97 ± 1.62 mmHg (95% CI: −5.14 to 1.20) for DBP, −1.49 ± 1.40 mmHg (95% CI: −4.25 to 1.26) for MAP, and 1.43 ± 2.79 mmHg (95% CI: −4.03 to 6.90) for PP.ConclusionsThe SCICA approach is a powerful tool that identifies sources contributing to morphological distortion at peripheral arteries and estimates cBP

model and simulation in cardiac imaging

Die Wandschubspannung (WSS) ist ein zentraler Risikofaktor für Lokalisation und Entwicklung atherosklerotischer Veränderungen in den Herzkranzgefäßen. Dieser Risikofaktor ist in den Herzkranzgefäßen bis dato nicht direkt messbar, kann aber über Simulationsmodellstudien bewertet werden. Hierfür sind relativ aufwändige Strömungssimulationsstudien in 3-D Rekonstruktionen von Herzkranzgefäßen erforderlich. Entwicklungen der letzten Jahrzehnte in der 3-D Rekonstruktion und der Rechenleistung eröffnen die Perspektive eines Transfers der Beurteilung dieses Risikofaktors in die klinische Medizin (bench- to–bedside). Von besonderem Interesse ist hier der Blick auf ganze Koronarbäume und die Früherkennung und Verlaufsbeurteilung diffuser und früher Veränderungen der Geometrie und der Strömung. Der Autor war an der Entwicklung der 3-D Rekonstruktion am DHZB beteiligt und hat die Methode klinisch validiert und in einer Verlaufsstudie das klinische Potential der 3-D QCA zeigen können. An unterschiedlichen Modellen und stratifizierten Stichproben hat der Autor Kriterien und Verfahren entwickelt, die zur Beurteilung der WSS im Hinblick auf klinische Fragestellungen bzgl. der Früherkennung und Verlaufsbeurteilung diffuser und früher Veränderungen der Geometrie und der Strömung geeignet sind. Durch die rasante Entwicklung der Computertomographie, der Rotationsangiographie und der kardialen Magnetresonanztomographie hat sich die Entwicklung der 3-D Rekonstruktion weitgehend in die F&E; -Abteilungen der Großgerätehersteller und ihrer Softwarelieferanten verlagert. Kommerziell erhältliche Software erlaubt eine effiziente Konstruktion von koronaren 3-D Modellen aus Routinedaten. Entwicklungen auf dem Sektor der nicht invasiven kardialen Bildgebung (Rotationsangiographie, CT und MRT) werden neue Geometriedatenquellen für Flusssimulationsstudien erschließen. Die zunehmende Rechenleistung der Hardware und die Entwicklung auf dem Softwaresektor werden dazu führen, dass Flusssimulationen genau wie virtuelle Endoskopie als professionelle Anwendertools unmittelbar dem Arzt zur Verfügung stehen und den Risikofaktor WSS für die klinische Medizin bereitstellen.Wall shear stress (WSS) is a crucial risk factor concerning localisation and progression of atherosclerotic inflammation and remodeling in coronary arteries. Direct measurement of this risk factor is not feasible hitherto. It may be assessed computational simulation of fluid dynamics (CFD), however. This approach requires computationally demanding studies in three-dimensional (3-D) reconstructions of coronary arteries. Recent progress in computational power and commercial 3-D reconstruction software promises a transfer of the assessment of this risk factor from bench to bedside. A comprehensive vision of the entire vascular tree and the detection of early disease and diffuse progress are of particular interest. The author was involved in the development of 3-D reconstruction at he DHZB and performed clinical validation of the method. He was able to demonstrate the clinical potential of 3-D QCA The author developed criteria and methods for assessment of features of WSS distribution in different models and stratified samples, which target clinical issues regarding detection and evaluation of progression of early and/or diffuse changes in shape remodeling and blood flow. The rapid development of computed tomography, rotational angiography and cardiac magnetic resonance imaging caused a shift of the development of 3-D reconstruction from university to industry. Currently commercially available software allows efficient construction of 3-D models from routine cardiac image data. Further advances in non-invasive cardiac imaging will provide new sources of data on vascular shape for CFD. Hardware memory and speed will further increase and foster software development. As a result flow simulation and virtual endoscopy will be professional application tools. Thus the assessment of the risk factor wall shear stress will be available in clinical practice in future

In-vivo coronary flow profiling based on biplane angiograms: influence of geometric simplifications on the three-dimensional reconstruction and wall shear stress calculation

Abstract Background Clinical studies suggest that local wall shear stress (WSS) patterns modulate the site and the progression of atherosclerotic lesions. Computational fluid dynamics (CFD) methods based on in-vivo three-dimensional vessel reconstructions have recently been shown to provide prognostically relevant WSS data. This approach is, however, complex and time-consuming. Methodological simplifications are desirable in porting this approach from bench to bedside. The impact of such simplifications on the accuracy of geometry and wall shear stress calculations has to be investigated. Methods We investigated the influence of two methods of lumen reconstruction, assuming circular versus elliptical cross-sections and using different resolutions for the cross-section reconstructions along the vessel axis. Three right coronary arteries were used, of which one represented a normal coronary artery, one with "obstructive", and one with "dilated" coronary atherosclerosis. The vessel volume reconstruction was performed with three-dimensional (3D) data from a previously validated 3D angiographic reconstruction of vessel cross-sections and vessel axis. Results The difference between the two vessel volumes calculated using the two evaluated methods is less than 1 %. The difference, of the calculated pressure loss, was between 2.5% and 8.5% for the evaluated methods. The distributions of the WSS histograms were nearly identical and strongly cross-correlated (0.91–0.95). The good agreement of the results was confirmed by a Chi-square test. Conclusion A simplified approach to the reconstruction of coronary vessel lumina, using circular cross-sections and a reduced axial resolution of about 0.8 mm along the vessel axis, yields sufficiently accurate calculations of WSS.</p

Overlapping Stents for Treatment of a Dissecting Carotid Artery Aneurysm

l l Purpose: To report the increased efficacy of oversized, overlapping stents to treat an in-ternal carotid artery (ICA) dissecting aneurysm. Case Report: A 55-year-old woman presented with reduced consciousness, aphasia, and right-sided hemiplegia owing to an infarction of the left middle cerebral artery territory documented by computed tomography. Digital subtraction angiography disclosed an ex-tracranial dissection of the left ICA with a pseudoaneurysm. Two self-expanding Wallstents were placed, bridging the dissected segment and overlapping at the level of the aneurysm neck. Immediate arteriography showed remarkably reduced filling of the pseudoaneurysm. Serial arteriograms performed 6 days and 9 and 20 months after stenting documented the disappearance of the pseudoaneurysm without appreciable intimal hyperplasia of the ves-sel wall. Conclusions: Reducing stent porosity by overlapping the devices causes significant he-modynamic changes inside the aneurysm sac, accelerating intra-aneurysmal thrombosis. J Endovasc Ther 2001;8:566–570 Key words: internal carotid artery, pseudoaneurysm, cerebral infarction, Wallstent, aneurysm sac thrombosis l l Wide-necked arterial aneurysms of the extra-cranial carotid artery are difficult to treat sur-gically if located close to the base of the skull. Coil embolization may not be successful, par-ticularly in large aneurysms. The application of metallic stents has shown increasing prom-ise for endovascular treatment of dissecting aneurysms in the extracranial and, more re-cently, the intracranial carotid territories.1–6 Depending on local hemodynamics, complete aneurysm occlusion by stent placement is Address for correspondence and reprints: Goetz Benndorf