MRI compatible 3-D intracardiac echography catheter and system
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.
1. A CMUT on CMOS chip for imaging applications, comprising:
a plurality of CMUT transmit (“Tx”) elements transmitting an imaging pulse;
a plurality of CMUT receive (“Rx”) elements, disposed in proximity to the plurality of Tx elements, receiving the imaging pulse, and each Rx element generating a receiver signal; and
a plurality of electronics interfacing with the Tx elements and the Rx elements, comprising:
a multiplexing component receiving at least half of the generated receiver signals simultaneously and reducing a number of output signals, based on the receiver signals, by a ratio of between 15-to-1 and 50-to-1; and
a beamforming component communicating with Tx elements.
2. The CMUT on CMOS chip of claim 1 , wherein the multiplexing component uses frequency division multiplexing (“FDM”).
3. The CMUT on CMOS chip of claim 2 , wherein the multiplexing component comprises:
a feedback transimpedance amplifier (“TIA”) receiving the receiver signal from the Rx elements;
a mixer receiving a first signal from the TIA;
a band pass filter (“BPF”) receiving a second signal from the mixer;
an adder receiving a third signal from the BPF; and
a buffer receiving a fourth signal from the adder and producing the output signal.
4. The CMUT on CMOS chip of claim 1 , wherein the beamforming component comprises:
a high voltage pulser electrically connected to the Tx elements; and
a timing and coding circuit electrically connected to the high voltage pulser.
5. The CMUT on CMOS chip of claim 1 , wherein the multiplexing component produces the output signal using time division multiplexing (“TDM”).
6. The CMUT on CMOS chip of claim 5 , wherein the multiplexing component comprises:
a feedback transimpedance amplifier (“TIA”) receiving the receiver signal from the Rx elements;
a time-gain compensation (“TGC”) circuit receiving a first signal from the TIA;
a time division multiplexing switch receiving a second signal from the TGC; and
a buffer receiving a third signal from the time division multiplexing switch and producing the output signal.
7. The CMUT on CMOS chip of claim 5 , wherein the time division multiplexing switch samples the second signal at a rate greater than the Nyquist rate.
8. The CMUT on CMOS chip of claim 5 , wherein the plurality of electronics comprises:
a de-multiplexer receiving the RF output signal; and
a low pass filter receiving a first signal from the de-multiplexer and outputting a non-combined output signal.
9. The CMUT on CMOS chip of claim 1 , wherein the field of view is between 90°×90° at approximately 5 cm depth and 45°×45° at approximately 15 cm depth.
10. The CMUT on CMOS chip of claim 1 , wherein the multiplexing component reduces the number of output signals, based on the receiver signals, by a ratio of at least 16-to-1.
11. The CMUT on CMOS chip of claim 1 , wherein the multiplexing component uses orthogonal frequency division multiplexing (“OFDM”).
12. The CMUT on CMOS chip of claim 11 , wherein the multiplexing component comprises:
a feedback transimpedance amplifier (“TIA”) receiving the receiver signal from the Rx elements;
a single to differential converter (“STD”) receiving a first signal from the TIA;
a low band pass filter (“LPF”) receiving a second signal from the STD;
a mixer receiving a third signal from the LPF;
a band pass filter (“BPF”) receiving a fourth signal from the mixer; and
a buffer receiving a fifth signal from the adder and producing the output signal.
13. The CMUT on CMOS chip of claim 1 , wherein at least one of the plurality of Tx elements; the plurality of Rx elements; and the plurality of electronics is on a separate CMUT on CMOS chip in a stacked configuration.
14. A system for intracardiac imaging, comprising:
an intracardiac echography catheter having an internal volume, a proximal end and a distal end, comprising:
an atraumatic tip disposed on the distal end of the catheter;
a CMUT on CMOS volumetric imaging chip disposed proximal of the tip, comprising:
a plurality of CMUT transmit (“Tx”) elements transmitting an imaging pulse;
a plurality of CMUT receive (“Rx”) elements, disposed in proximity to the plurality of Tx elements, receiving the imaging pulse, and each Rx element generating a receiver signal; and
a plurality of electronics interfacing with the Tx elements and the Rx elements, comprising:
a multiplexing component receiving at least half of the generated receiver signals simultaneously and reducing a number of output signals, based on the receiver signals, by a ratio between 15-to-1 and 50-to-1; and
a beamforming component communicating with Tx elements; and
a cable lumen disposed within the volume and configured to receive a plurality of output signal cables from the chip.
15. The system of claim 14 , wherein a size of the catheter is approximately 6 French to approximately 10 French.
16. The system of claim 14 , wherein the catheter further comprises a cooling lumen cooling the catheter from RF induced heating when the catheter is used in conjunction with an MRI scan.
17. The system of claim 14 , wherein the catheter further comprises a pair of inductively coupled coils proximal the atraumatic tip wherein one coil is proximal of the chip and the second coil is distal of the chip, wherein the coils are configured to be visible during MRI operation.
18. The system of claim 14 , wherein the catheter further comprises:
a body comprising at least one MRI safe material;
at least one direction wire disposed in a directional wire lumen, the wire comprising at least one MRI safe material;
wherein the catheter is configured to be used during at least one of interlaced and simultaneous MRI and ultrasound operation.
19. The system of claim 18 , wherein the at least one MRI safe materials are also x-ray safe materials.
20. The system of claim 14 , wherein the multiplexing component produces the output signal using at least one of frequency division multiplexing (“FDM”), time division multiplexing (“TDM”), and orthogonal frequency division multiplexing (“OFDM”).