MRI compatible 3-D intracardiac echography catheter and system
Inventors
Degertekin, Fahrettin Levent • Tekes, Coskun • Lederman, Robert Jay • Kocaturk, Ozgur • Rashid, M. Wasequr • Ghovanloo, Maysam
Assignees
Georgia Tech Research Corp • US Department of Health and Human Services
Publication Number
US-10123768-B2
Publication Date
2018-11-13
Expiration Date
2034-09-25
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Abstract
An intracardiac imaging system has an intracardiac echography catheter with an internal volume, a proximal end and a distal end. The catheter includes an atraumatic tip disposed on the distal end of the catheter, a pair of inductively coupled coils proximal the atraumatic tip, at least one CMUT on CMOS volumetric imaging chip disposed between the pair of coils, and a cable lumen disposed within the volume and configured to small number of electrical connections due to significant multiplexing in the CMUT on CMOS chip. The catheter can be made of MRI compatible materials and can include active cooling channels. The CMUT on CMOS chip has a plurality of Tx elements transmitting imaging pulses, a plurality of Rx elements, disposed on the chip to have a large aperture and a plurality of electronics interfacing with the Tx elements for beamforming and the Rx elements to produce radio frequency output signals.
Core Innovation
The invention is a 3D intracardiac echography (ICE) catheter system utilizing capacitive micromachined ultrasonic transducers on complementary metal-oxide-semiconductor (CMUT-on-CMOS) technology for volumetric ultrasound imaging. This catheter integrates CMUT transmit (Tx) and receive (Rx) elements in a CMUT-on-CMOS chip with on-chip beamforming and massive multiplexing to reduce the number of required external cables significantly. The catheter includes an atraumatic tip, inductively coupled coils for MRI visibility, and can be fabricated from MRI compatible materials with active cooling channels. The system is designed to operate safely under MRI, minimizing RF induced heating and artifacts, while enabling full volumetric real-time 3D intracardiac imaging.
The problem addressed is the limitations of existing intracardiac imaging technologies, which rely on 2D slices or limited 3D volumes that inadequately depict real-time navigation of catheter tips and cardiac structures during interventional procedures. Conventional systems require numerous electrical connections, resulting in large catheter sizes and prohibitive manufacturing complexities, and are unsuitable for MRI operation due to RF heating. Current 3D intracardiac or transesophageal ultrasound probes are not adequately miniaturized for pediatric use or real-time guidance, leading to reliance on X-ray fluoroscopy, exposing patients to radiation and increasing procedural difficulty and duration.
This invention overcomes these limitations by providing a catheter with a large 2D receive array and integrated electronics allowing volumetric image acquisition with fewer than 10 transmit firings and massive multiplexing reducing cable count by 15 to 50 times. Different multiplexing schemes such as frequency division multiplexing, time division multiplexing, and orthogonal frequency division multiplexing are implemented on-chip to enable high bandwidth data transfer. The catheter’s MRI-compatible design includes inductively coupled coils for tracking, active cooling lumens to manage RF heating safely, and mechanical features similar to existing catheters for clinical reliability. This enables radiation-free, real-time, full-volume 3D intracardiac ultrasound imaging compatible with MRI and X-ray systems, supporting complex cardiac interventions with improved guidance and safety.
Claims Coverage
The patent includes two independent claims focusing on a CMUT-on-CMOS chip for imaging applications and a system for intracardiac imaging incorporating the chip. The main inventive features revolve around integrated on-chip multiplexing and beamforming electronics, MRI-compatible catheter design, and methods for reducing cable count significantly.
Integrated multiplexing component reducing output signals
The chip includes a multiplexing component that simultaneously receives at least half of the CMUT receive signals and reduces the number of output signals by a ratio between 15-to-1 and 50-to-1, thereby significantly minimizing cable count.
Beamforming component communicating with transmit elements
The chip comprises an on-chip beamforming component that interfaces with CMUT transmit elements to control the transmission of imaging pulses, including high voltage pulsers and timing/coding circuits.
Use of frequency division multiplexing (FDM) in the multiplexing component
The multiplexing component uses FDM involving feedback transimpedance amplifiers, mixers, bandpass filters, adders, and buffers to combine multiple receiver signals into fewer outputs for cable reduction.
Use of time division multiplexing (TDM) in the multiplexing component
An alternative multiplexing approach using TDM involves a feedback TIA, time-gain compensation, synchronized TDM switches sampling faster than the Nyquist rate, and buffers to output combined signals.
Use of orthogonal frequency division multiplexing (OFDM) in the multiplexing component
The multiplexing component can implement OFDM with components including capacitive-feedback TIAs, single to differential converters, low pass filters, mixers, band pass filters, and buffers to multiplex outputs of multiple channels on a single RF line.
MRI-compatible catheter system with CMUT-on-CMOS chip and minimal wiring
The system comprises an intracardiac echography catheter with an atraumatic tip, CMUT-on-CMOS volumetric imaging chip with multiplexing and beamforming electronics, a cable lumen configured for reduced electrical connections, with catheter sizes approximately 6 to 10 French.
Catheter features for MRI safety and tracking
The catheter includes active cooling lumens to manage RF heating under MRI and a pair of inductively coupled coils proximal to the catheter tip for MRI visibility and tracking, minimizing RF heating and artifacts.
Use of MRI and X-ray safe materials and compatibility with interlaced or simultaneous MRI and ultrasound operation
The catheter body and directional wires are made from MRI and X-ray safe materials and are configured for use during interlaced or simultaneous MRI and ultrasound procedures.
The claims encompass a CMUT-on-CMOS chip with sophisticated multiplexing and beamforming electronics to reduce cable count dramatically, integrated into an MRI-compatible intracardiac catheter system with features for safe operation, active cooling, and tracking, enabling real-time volumetric 3D intracardiac imaging under MRI and X-ray.
Stated Advantages
Dramatically enhances image guidance of complex catheter-based cardiovascular treatments.
Allows procedures to be performed more safely and efficiently while avoiding radiation exposure, especially in children.
Enables novel procedures otherwise requiring surgical repair through improved real-time full-volume 3D imaging.
Significantly reduces cable count, minimizing catheter size and RF induced heating risk under MRI.
Provides real-time en-face depiction of cardiac pathology and catheter devices without constraints of bone, lung windows, or limited probe positioning.
Combines ultrasound imaging with MRI tracking in a single catheter platform, enabling radiation-free catheter navigation and depiction of larger anatomic context.
Cooling system and MRI compatible materials minimize artifacts and RF heating risks.
Documented Applications
Image guidance in intracardiac interventions such as atrial septal defect closure, ventricular septal defect repair, paravalvular leak repair, left atrial appendage closure, and mitral valve leaflet repairs.
MRI-guided catheter-based cardiovascular procedures without radiation exposure, suitable for both adults and children.
Real-time 3D ICE guidance in structural heart disease interventions traditionally reliant on X-ray fluoroscopy and limited 2D or 3D echocardiography.
Potential for novel catheter-based treatments such as non-surgical extra-anatomic bypass and non-surgical mitral neochordal implantation.
Use during simultaneous or interlaced MRI and ultrasound operation for catheter tracking and imaging.
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