Browsing NTNU Open by Author "Avdal, Jørgen"
Now showing items 1-18 of 18
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3-D Doppler imaging in cardiac applications using high frame-rate sequences
Fiorentini, Stefano (Doctoral theses at NTNU;2020:60, Doctoral thesis, 2020)Several decades after the establishment of Doppler ultrasound, quantification and imaging of blood flow using Doppler-based techniques continue to face multiple challenges. Out-of-plane flow, transit-time broadening and ... -
Analysis of Aberration Effects on Flow Imaging and Quantification in Echocardiography
Fiorentini, Stefano; Måsøy, Svein-Erik; Avdal, Jørgen (Journal article; Peer reviewed, 2023)In medical ultrasound, aberration is a phenomenon that causes distortion of the ultrasound wavefront as it travels through an inhomogeneous medium. Aberration has been investigated since the 1960s and is known as a major ... -
Combined 2-D Vector imaging and Tracking Doppler for improved vascular blood velocity quantification
Avdal, Jørgen; Løvstakken, Lasse; Torp, Hans; Ekroll, Ingvild Kinn (Journal article; Peer reviewed, 2017)Measurement of the maximum blood flow velocity is the primary means for determining the degree of carotid stenosis using ultrasound. The current standard for estimating the maximum velocity is Pulsed Wave (PW) Doppler with ... -
Combining Automatic Angle Correction and 3-D Tracking Doppler for the Assessment of Aortic Stenosis Severity
Fiorentini, Stefano; Espeland, Torvald; Berg, Erik Andreas Rye; Aakhus, Svend; Torp, Hans; Avdal, Jørgen (Journal article; Peer reviewed, 2019)Aortic valve stenosis (AS) is a narrowing of the aortic valve opening, which causes increased load on the left ventricle. Untreated, this condition can eventually lead to heart failure and death. According to current ... -
Data Adaptive 2-D Tracking Doppler for High-Resolution Spectral Estimation
Karabiyik, Yücel; Avdal, Jørgen; Ekroll, Ingvild Kinn; Fiorentini, Stefano; Torp, Hans; Løvstakken, Lasse (Peer reviewed; Journal article, 2019)Spectral broadening in pulsed-wave Doppler caused by the transit-time effect deteriorates the frequency resolution and may cause overestimation of maximum velocities in high-velocity blood flow regions and for large ... -
Deep Learning Applications for the Assessment of Valvular Heart Disease using Transthoracic Echocardiography
Wifstad, Sigurd Vangen (Doctoral theses at NTNU;2024:198, Doctoral thesis, 2024)Valvular heart disease (VHD) is a class of diseases that affect the heart valves, and are associated with a reduced cardiac output and a poor prognosis for the afflicted patients. Transthoracic echocardiography (TTE) is ... -
Development of a new algorithm for measurement of fatigue and stress in steel
Avdal, Jørgen (Master thesis, 2009)A study is done on the transient phase of a voltage signal resulting from a current regulated four point probe measurement on steel plates. Some electromagnetic theory is developed, including a study of the effects of ... -
Doppler ultrasound for quantification of fluid influx/ efflux from borehole fractures using LWD tools
Indimath, Shivanandan (Doctoral theses at NTNU;2024:221, Doctoral thesis, 2024)The work presented in this thesis is aimed at studying the potential for applying ultrasonic Doppler measurements during a borehole drilling process using ultrasonic logging-while-drilling (LWD) tools. The primary intention ... -
Effect of bubble size on ultrasound backscatter from bubble clouds in the context of gas kick detection in boreholes
Indimath, Shivanandan; Fiorentini, Stefano; Bøklepp, Bjarne Rosvoll; Avdal, Jørgen; Johansen, Tonni Franke; Måsøy, Svein-Erik (Peer reviewed; Journal article, 2023)Early detection of gas influx in boreholes while drilling is of significant interest to drilling operators. Several studies suggest a good correlation between ultrasound backscatter/attenuation and gas volume fraction (GVF) ... -
En ny metode for aliaskorrigering i Vector Doppler Ultralyd: Evaluering av en tosidig oppsett
Alsenwar, Manar (Master thesis, 2019)Doppler ultralyd er et veldig nyttig verktøy i klinisk praksis, og det brukes til blodhastighetsestimering. Imidlertid er alle strømningshastighetsestimater en-dimensjonal, noe som gjøre at estimatene vil være avhengige ... -
FLUST: A fast, open source framework for ultrasound blood flow simulations
Ekroll, Ingvild Kinn; Saris, Anne E.C.M; Avdal, Jørgen (Peer reviewed; Journal article, 2023)Background and objective:Ultrasound based blood velocity estimation is a continuously developing frontier, where the vast number of possible acquisition setups and velocity estimators makes it challenging to assess which ... -
Maximum velocity estimation in coronary arteries using 3D tracking Doppler
Fiorentini, Stefano; Saxhaug, Lars Mølgaard; Holte, Espen; Bjåstad, Tore Grüner; Torp, Hans; Avdal, Jørgen (Journal article, 2018)Several challenges currently prevent the use of Doppler echocardiography to assess blood flow in the coronary arteries. Due to the anatomy of the coronary tree, out-of-plane flow and high beam-to-flow angles easily occur. ... -
Model-Based Evaluation of Blood Velocity Estimation Techniques
Avdal, Jørgen (Doctoral thesis at NTNU;2015:81, Doctoral thesis, 2015)Pulsed Wave (PW) Doppler is a flow imaging modality in which the velocity distribution of the blood flow in a spatial region is displayed over time. In this work, methods for improvement of the conventional PW Doppler ... -
Optimization of pulsed-wave Doppler ultrasound for estimation of influx/efflux in oil and gas boreholes while drilling using conventional LWD transducers
Indimath, Shivanandan; Fiorentini, Stefano; Bøklepp, Bjarne Rosvoll; Avdal, Jørgen; Måsøy, Svein-Erik (Peer reviewed; Journal article, 2022)The extraction of oil and gas typically involves drilling boreholes through various subsurface strata. Abrupt variations in the formation properties can severely compromise the borehole stability if the drilling process ... -
Quantification of Flow Rates and Flow Volumes in Valve Regurgitation Using 3-D High Frame-Rate Ultrasound
Fiorentini, Stefano; Berg, Erik Andreas Rye; Torp, Hans Garman; Aakhus, Svend; Avdal, Jørgen (Journal article; Peer reviewed, 2023)Valve regurgitation is a cardiac condition caused by the incomplete closure of a cardiac valve. Untreated, this condition may result in cardiac failure. Regular monitoring of this condition is essential in guiding the ... -
Quantifying Valve Regurgitation Using 3-D Doppler Ultrasound Images and Deep Learning
Wifstad, Sigurd Vangen; Løvstakken, Lasse; Avdal, Jørgen; Berg, Erik Andreas Rye; Torp, Hans; Grenne, Bjørnar; Fiorentini, Stefano (Peer reviewed; Journal article, 2022)Accurate quantification of cardiac valve regurgitation jets is fundamental for guiding treatment. Cardiac ultrasound is the preferred diagnostic tool, but current methods for measuring the regurgitant volume are limited ... -
Retrospective Transmit beamforming and Coherent Plane-Wave Compounding for Microvascular Doppler Imaging: A Comparison Study
Golfetto, Cristiana; Ekroll, Ingvild Kinn; Torp, Hans; Løvstakken, Lasse; Avdal, Jørgen (Peer reviewed; Journal article, 2020)Imaging blood flow in small vessels is of great clinical value for evaluating increased vascularization, potentially related to angiogenesis in cancer or inflammation processes in musculoskeletal disease. Using a traditional ... -
Tapered Vector Doppler for Improved Quantification of Low Velocity Blood Flow
Ekroll, Ingvild Kinn; Perrot, Vincent; Liebgott, Herve; Avdal, Jørgen (Peer reviewed; Journal article, 2020)A new vector velocity estimation scheme is developed, termed Tapered Vector Doppler (TVD), aiming to improve the accuracy of low velocity flow estimation. This is done by assessing the effects of Singular Value Decompostion ...