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Chi Hyung Seo,
Douglas N Stephens,
Jonathan Cannata,
Aaron Dentinger,
Feng Lin,
Suhyun Park,
Douglas Wildes,
Kai E Thomenius, Peter Chen,
Tho Nguyen,
Alan de La Rama,
Jong Seob Jeong,
Aman Mahajan,
Kalyanam Shivkumar,
Amin Nikoozadeh,
Omer Oralkan,
Uyen Truong,
David J Sahn,
Pierre T Khuri-Yakub,
Matthew O'Donnell
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ABSTRACT: A method is introduced to monitor cardiac ablative therapy by examining slope changes in the thermal strain curve caused by speed of sound variations with temperature. The sound speed of water-bearing tissue such as cardiac muscle increases with temperature. However, at temperatures above about 50°C, there is no further increase in the sound speed and the temperature coefficient may become slightly negative. For ablation therapy, an irreversible injury to tissue and a complete heart block occurs in the range of 48 to 50°C for a short period in accordance with the well-known Arrhenius equation. Using these two properties, we propose a potential tool to detect the moment when tissue damage occurs by using the reduced slope in the thermal strain curve as a function of heating time. We have illustrated the feasibility of this method initially using porcine myocardium in vitro. The method was further demonstrated in vivo, using a specially equipped ablation tip and an 11-MHz microlinear intracardiac echocardiography (ICE) array mounted on the tip of a catheter. The thermal strain curves showed a plateau, strongly suggesting that the temperature reached at least 50°C.
IEEE transactions on ultrasonics, ferroelectrics, and frequency control 07/2011; 58(7):1406-17. · 1.80 Impact Factor
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B T Khuri-Yakub,
Omer Oralkan,
Amin Nikoozadeh,
Ira O Wygant,
Steve Zhuang,
Mustafa Gencel,
Jung Woo Choe,
Douglas N Stephens,
Alan de la Rama, Peter Chen,
Feng Lin,
Aaron Dentinger,
Douglas Wildes,
Kai Thomenius,
Kalyanam Shivkumar,
Aman Mahajan,
Chi Hyung Seo,
Matthew O'Donnell,
Uyen Truong,
David J Sahn
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ABSTRACT: Capacitive micromachined ultrasonic transducer (CMUT) arrays are conveniently integrated with frontend integrated circuits either monolithically or in a hybrid multichip form. This integration helps with reducing the number of active data processing channels for 2D arrays. This approach also preserves the signal integrity for arrays with small elements. Therefore CMUT arrays integrated with electronic circuits are most suitable to implement miniaturized probes required for many intravascular, intracardiac, and endoscopic applications. This paper presents examples of miniaturized CMUT probes utilizing 1D, 2D, and ring arrays with integrated electronics.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2010; 2010:5987-90.
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Douglas N Stephens,
Matthew O'Donnell,
Kai Thomenius,
Aaron Dentinger,
Douglas Wildes, Peter Chen,
K Kirk Shung,
Jonathan Cannata,
Pierre Khuri-Yakub,
Omer Oralkan,
Aman Mahajan,
Kalyanam Shivkumar,
David J Sahn
[show abstract]
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ABSTRACT: The purpose of this study was to develop a high-resolution, near-field-optimized 14-MHz, 24-element broad-bandwidth forward-looking array for integration on a steerable 9F electrophysiology (EP) catheter.
Several generations of prototype imaging catheters with bidirectional steering, termed microlinear (ML), were built and tested as integrated catheter designs with EP sensing electrodes near the tip. The wide-bandwidth ultrasound array was mounted on the very tip, equipped with an aperture of only 1.2 by 1.58 mm. The array pulse echo performance was fully simulated, and its construction offered shielding from ablation noise. Both ex vivo and in vivo imaging with a porcine animal model were performed.
The array pulse echo performance was concordant with Krimholtz-Leedom-Matthaei model simulation. Three generations of prototype devices were tested in the right atrium and ventricle in 4 acute pig studies for the following characteristics: (1) image quality, (2) anatomic identification, (3) visualization of other catheter devices, and (4) for a mechanism for stabilization when imaging ablation. The ML catheter is capable of both low-artifact ablation imaging on a standard clinical imaging system and high-frame rate myocardial wall strain rate imaging for detecting changes in cardiac mechanics associated with ablation.
The imaging resolution performance of this very small array device, together with its penetration beyond 2 cm, is excellent considering its very small array aperture. The forward-looking intracardiac catheter has been adapted to work easily on an existing commercial imaging platform with very minor software modifications.
Journal of ultrasound in medicine: official journal of the American Institute of Ultrasound in Medicine 03/2009; 28(2):207-15. · 1.25 Impact Factor
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David J Sahn,
Douglas N Stephens,
Jonathan M Cannata,
K Shung,
Omer Oralkan,
Amin Nikoozadeh,
B T Pierre Khuri-Yakub,
Hien Nguyen, Peter Chen,
Aaron M Dentinger,
Douglas Wildes,
Kai E Thomenius,
Aman Mahajan,
Kalyanam Shivkumar,
Matthew O'Donnell
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ABSTRACT: Our Bioengineering Research Partnership grant, -High Frequency Ultrasound Arrays for Cardiac Imaging", including the individuals cited at the end of this paper - Douglas N. Stephens (UC Davis), Matthew O'Donnell (UW Seattle), Kai Thomenius (GE Global Research), Aaron M. Dentinger (GE Global Research), Douglas Wildes (GE Global Research), Peter Chen (St. Jude Medical), K. Kirk Shung (University of Southern California), Jonathan M. Cannata (University of Southern California), Butrus (Pierre) T. Khuri-Yakub (Stanford University), Omer Oralkan (Stanford University), Aman Mahajan (UCLA School of Medicine), Kalyanam Shivkumar (UCLA School of Medicine) and David J. Sahn (Oregon Health & Science University) - is in its sixth year of NIH funding, having proposed to develop a family of high frequency miniaturized forward and side-looking ultrasound imaging devices equipped with electrophysiology mapping and localization sensors and eventually to include a family of capactive micromachined ultrasonic transducer (cMUT) devices - a forward-looking cMUT MicroLinear array and a ring array capable of 3-dimensional imaging and a 5Fr lumen large enough to admit an electrode and ablation devices.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2009; 2009:1913-7.
