Developing an Interface and Investigating Optimal Parameters for Real-Time Intracardiac Subharmonic-Aided Pressure Estimation.

Thisstudy focuses on evaluating the real-time functionality of a customized interface and investigating the optimal parameters for intracardiac subharmonic-aided pressure estimation (SHAPE) utilizing Definity (Lantheus Medical Imaging Inc., North Billerica, MA, USA) and Sonazoid (GE Healthcare, Oslo, Norway) microbubbles. Pressure measurements within the chambers of the heart yield critical information for managing cardiovascular diseases.

Real-time 1-D/2-D transient elastography on a standard ultrasound scanner using mechanically induced vibration.

Transient elastography has been well established in the literature as a means of assessing the elasticity of soft tissue. In this technique, tissue elasticity is estimated from the study of the propagation of the transient shear waves induced by an external or internal source of vibration. Previous studies have focused mainly on custom single-element transducers and ultrafast scanners which are not available in a typical clinical setup.

Subharmonic microbubble emissions for noninvasively tracking right ventricular pressures.

Right heart catheterization is often required to monitor intra-cardiac pressures in a number of disease states. Ultrasound contrast agents can produce pressure modulated subharmonic emissions that may be used to estimate right ventricular (RV) pressures. A technique based on subharmonic acoustic emissions from ultrasound contrast agents to track RV pressures noninvasively has been developed and its clinical potential evaluated.

Multi-channel pre-beamformed data acquisition system for research on advanced ultrasound imaging methods.

The lack of open access to the pre-beamformed data of an ultrasound scanner has limited the research of novel imaging methods to a few privileged laboratories. To address this need, we have developed a pre-beamformed data acquisition (DAQ) system that can collect data over 128 array elements in parallel from the Ultrasonix series of research-purpose ultrasound scanners. Our DAQ system comprises three system-level blocks: 1) a connector board that interfaces with the array probe and the scanner through a probe connector port; 2) a main board that triggers DAQ and controls data transfer to a computer; and 3) four receiver boards that are each responsible for acquiring 32 channels of digitized raw data and storing them to the on-board memory.

Noninvasive LV pressure estimation using subharmonic emissions from microbubbles.

To develop a new noninvasive approach to quantify left ventricular (LV) pressures using subharmonic emissions from microbubbles, an ultrasound scanner was used in pulse inversion grayscale mode; unprocessed radiofrequency data were obtained with pulsed wave Doppler from the aorta and/or LV during Sonazoid infusion. Subharmonic data (in dB) were extracted and processed. Calibration factor (mm Hg/dB) from the aortic pressure was used to estimate LV pressures.

Noninvasive estimation of dynamic pressures in vitro and in vivo using the subharmonic response from microbubbles.

The purpose of this study was to develop and validate a noninvasive pressure estimation technique based on subharmonic emissions from a commercially available ultrasound contrast agent and scanner, unlike other studies that have either adopted a single-element transducer approach and/ or use of in-house contrast agents. Ambient pressures were varied in a closed-loop flow system between 0 and 120 mmHg and were recorded by a solid-state pressure catheter as the reference standard. Simultaneously, the ultrasound scanner was operated in pulse inversion mode transmitting at 2.