Y. Gao, M. Weiß, and W. Nahm. Reduction of Uncertainty in Bolus Transit Time Measurement in Quantitative Fluorescence Angiography. In Current Directions in Biomedical Engineering, vol. 9(1) , pp. 619-622, 2023
Abstract:
During cerebral revascularization surgeries, blood flow values help surgeons to monitor the quality of the pro- cedure, e.g., to avoid cerebral hyperperfusion syndrome due to excessively enhanced perfusion. The state-of-the-art technique is the ultrasonic flow probe that has to be placed around the blood vessel. This causes contact between probe and vessel, which, in the worst case, leads to rupture. The recently devel- oped intraoperative indocyanine green (ICG) Quantitative Flu- orescence Angiography (QFA) is an alternative technique that overcomes this risk. However, it has been shown by the devel- oper that the calculated flow has deviations. After determining the bolus transit time as the most sensitive parameter in flow calculation, we propose a new two-step uncertainty reduction method for flow calculation. The first step is to generate more data in each measurement that results in functions of the pa- rameters. Noise can then be reduced in a second step. Two methods for this step are compared. The first method fits the model for each parameter function separately and calculates flow from models, while the second one fits multiple parame- ter functions together. The latter method is proven to perform best by in silico tests. Besides, this method reduces the de- viation of flow comparing to original QFA as expected. Our approach can be generally used in all QFA applications using two-point theory. Further development is possible if number of dimensions of the achieved parameter data are broadened that results in even more data for processing in the second step.
Models of cardiac mechanics are increasingly used to investigate cardiac physiology. These models are characterized by a high level of complexity, including the particular anisotropic material properties of biological tissue and the actively contracting material. A large number of independent simulation codes have been developed, but a consistent way of verifying the accuracy and replicability of simulations is lacking. To aid in the verification of current and future cardiac mechanics solvers, this study provides three benchmark problems for cardiac mechanics. These benchmark problems test the ability to accurately simulate pressure-type forces that depend on the deformed objects geometry, anisotropic and spatially varying material properties similar to those seen in the left ventricle and active contractile forces. The benchmark was solved by 11 different groups to generate consensus solutions, with typical differences in higher-resolution solutions at approximately 0.5%, and consistent results between linear, quadratic and cubic finite elements as well as different approaches to simulating incompressible materials. Online tools and solutions are made available to allow these tests to be effectively used in verification of future cardiac mechanics software.
Student Theses (2)
Y. Gao. Systematic investigation on the Factors Influencing Quantitative ICG Fluorescence Angiography. Institute of Biomedical Engineering, Karlsruhe Institute of Technology (KIT). Bachelorarbeit. 2023
Abstract:
In case of cerebrovascular diseases, patients sometimes need revascularization surgeries to overcome hypoperfusion. The goal is to remain or restore a regular blood flow. Thus, intraoperative blood flow measurement is crucial for surgeons to control the quality of surgical procedure. The state-of-the-art technique is using ultrasonic. However, the instrument has to contact with blood vessel, which may cause contamination, compromise, and in worst case rupture. Therefore, Quantitative Fluorescence Angiography (QFA) is under research. In this thesis, factors influencing the deviation and accuracy of retrospective QFA pipeline developed in previous work are investigated. Using centerline shortening for testing, transit time is proven to be the most sensitive parameter. After applying line fitting to transit time based on centerline shortening, flow turns out to be less deviated. The idea behind centerline shortening and line fitting can be used in all applications if there exists difficulty in collecting data of a single variable without changing others, high deviation of this variable and clear relationship between it and another less deviated variable/s with known distribution.
H. Gao. Aufbau und Ansteuerung einer High-Power-LED-Lichtquelle, für die fluoreszenzoptische Messung der Transmembranspannung von Kardiomyozyten. Institute of Biomedical Engineering, Karlsruhe Institute of Technology (KIT). Bachelorarbeit. 2012