scholarly journals Coregistration and Spatial Compounding of Optoacoustic Cardiac Images via Fourier Analysis of Four-Dimensional Data

2020 ◽  
Vol 10 (18) ◽  
pp. 6254
Author(s):  
Hongtong Li ◽  
Ivana Ivankovic ◽  
Jiao Li ◽  
Daniel Razansky ◽  
Xosé Luís Deán-Ben
Keyword(s):  
Fourier Analysis ◽  
Three Dimensional ◽  
Cardiac Events ◽  
Spatial Compounding ◽  
Optoacoustic Tomography ◽  
Ultrafast Imaging ◽  
Fundamental Frequencies ◽  
Retrospective Gating ◽  
Multiple Frames ◽  
Cardiac Images

Volumetric optoacoustic tomography has been shown to provide unprecedented capabilities for ultrafast imaging of cardiovascular dynamics in mice. Three-dimensional imaging rates in the order of 100 Hz have been achieved, which enabled the visualization of transient cardiac events such as arrhythmias or contrast agent perfusion without the need for retrospective gating. The fast murine heart rates (400–600 beats per minute) yet impose limitations when it comes to compounding of multiple frames or accurate registration of multi-spectral data. Herein, we investigate on the capabilities of Fourier analysis of four-dimensional data for coregistration of independent volumetric optoacoustic image sequences of the heart. The fundamental frequencies and higher harmonics of respiratory and cardiac cycles could clearly be distinguished, which facilitated efficient retrospective gating without additional readings. The performance of the suggested methodology was successfully demonstrated by compounding cardiac images acquired by raster-scanning of a spherical transducer array as well as by unmixing of oxygenated and deoxygenated hemoglobin from multi-spectral optoacoustic data.

scholarly journals Nervous Activity of the Brain in Five Dimensions

Biophysica ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 38-47
Author(s):  
Arturo Tozzi ◽  
James F. Peters ◽  
Norbert Jausovec ◽  
Arjuna P. H. Don ◽  
Sheela Ramanna ◽  
...  
Keyword(s):  
Fourier Analysis ◽  
Nervous Activity ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Data Sets ◽  
Spatial And Temporal Patterns ◽  
Five Dimensions ◽  
Four Dimensions ◽  
Scale Free ◽  
The Brain

The nervous activity of the brain takes place in higher-dimensional functional spaces. It has been proposed that the brain might be equipped with phase spaces characterized by four spatial dimensions plus time, instead of the classical three plus time. This suggests that global visualization methods for exploiting four-dimensional maps of three-dimensional experimental data sets might be used in neuroscience. We asked whether it is feasible to describe the four-dimensional trajectories (plus time) of two-dimensional (plus time) electroencephalographic traces (EEG). We made use of quaternion orthographic projections to map to the surface of four-dimensional hyperspheres EEG signal patches treated with Fourier analysis. Once achieved the proper quaternion maps, we show that this multi-dimensional procedure brings undoubted benefits. The treatment of EEG traces with Fourier analysis allows the investigation the scale-free activity of the brain in terms of trajectories on hyperspheres and quaternionic networks. Repetitive spatial and temporal patterns undetectable in three dimensions (plus time) are easily enlightened in four dimensions (plus time). Further, a quaternionic approach makes it feasible to identify spatially far apart and temporally distant periodic trajectories with the same features, such as, e.g., the same oscillatory frequency or amplitude. This leads to an incisive operational assessment of global or broken symmetries, domains of attraction inside three-dimensional projections and matching descriptions between the apparently random paths hidden in the very structure of nervous fractal signals.

scholarly journals Cardio-Oncology: The Role of Echocardiography in Cancer Patients

2021 ◽  
Author(s):  
Theodoros Ntoskas
Keyword(s):  
Cancer Therapy ◽  
Cancer Patients ◽  
Cardiac Imaging ◽  
Early Recognition ◽  
Cardiac Injury ◽  
Three Dimensional ◽  
Cardiovascular Complications ◽  
Cardiac Events ◽  
Ongoing Research ◽  
Wide Availability

Cardio-oncology is a rapidly emerging medical field that focusses on the improvement of the quality of life of cancer patients by preventing and treating the adverse cardiovascular complications of cancer therapy. Early recognition of cancer therapy-related cardiac dysfunction (CTRCD) provides an opportunity to mitigate cardiac injury and risk of developing late cardiac events. Cardiac imaging, and in particular, transthoracic echocardiography, plays an essential role in the baseline assessment, the detection and the surveillance of CRTCD in patients during and after the cancer therapy. Although the frequency of screening for the cardiotoxicity in patients undergoing active treatments and cancer survivors remains a topic of debate and ongoing research, echocardiography continues to be the leader for continuous monitoring by imaging due to the wide availability, lack of exposure to radiation, ability to recognise the effects on cardiac function and assess haemodynamics and other cardiac structures. The cardiac imaging applied to cardio-oncology includes standard and advanced (speckle tracking and three-dimensional (3D)) echocardiography.

Fundamental Frequencies of Turbine Blades With Geometry Mismatch in Fir-Tree Attachments

2006 ◽  
Vol 128 (3) ◽  
pp. 512-516 ◽  
Author(s):  
Fei Qin ◽  
Liming Chen ◽  
Ying Li ◽  
Xiaofeng Zhang
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Significant Influence ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Element Model ◽  
Gap Size ◽  
Fundamental Frequencies ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

Geometry mismatch in a turbine blade root, which arose in manufacturing process or caused by wearing out during service, leads to contact conditions changed in fir-tree attachments. As a result, shifting of the fundamental frequencies and redistribution of stress in the blade base possibly cause failure of the blade. A three-dimensional finite element model of a blade and its fir-tree attachments have been constructed and analyzed by taking into account contact nonlinearity in the attachments and large deformation effect of the blade. The geometry mismatch was introduced into the finite element model by defining gaps between two contact surfaces in the attachments. The influence of gap configuration and gap size on contact and fundamental frequencies was investigated. Results showed that gap configuration has significant influence on fundamental frequencies of the blade, especially on its bending modes. Gap size has little influence on the frequencies but significant influence on the contact status and thus changes stress distribution in the attachments. The results also suggest that modeling contact behavior in fir-tree attachments is necessary to obtain more accurate fundamental frequencies.

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