Apparatus for doppler interferometric imaging and imaging guidewire

• US 5,582,171 A
• Filed: 07/08/1994
• Issued: 12/10/1996
• Est. Priority Date: 07/08/1994
• Status: Expired due to Fees

• Current Assignee: Oppenheimer Wolff & Donnelly
• Original Assignee: Insight Medical Systems, Inc. (Enovis Corp.)
• Inventors: Chornenky, Victor, Fettig, Peter
• Primary Examiner(s): Smith, Ruth S.
• Application Number:
  US08/272,764
• Time in Patent Office: 886 Days
• Field of Search: 128/653.1, 128/633-634, 128/664-666, 128/656-658, 128/772, 604/96, 604/97, 356/345
• US Class Current: 600/425
• CPC Class Codes: A61B 1/00183 for variable viewing angles
• CPC Class Codes: A61B 2562/028 Microscale sensors, e.g. electromechanical sensors [MEMS]
• CPC Class Codes: A61B 5/0066 Optical coherence imaging
• CPC Class Codes: A61B 5/0084 for introduction into the body, e.g. by catheters A61B5/1459 takes precedence
• CPC Class Codes: A61M 25/09 Guide wires

Abstract

An apparatus for Doppler interferometric imaging comprising a balanced fiber optic interferometer, a low coherence light source and an imaging guidewire is used for diagnosis of intravascular obstructions. The imaging guidewire, which is also used for placement of over-the-wire catheters, comprises a hollow elongated body, an optical fiber, a rotatable mirror at its distal end and a micromotor operable to sweep the sampling beam around the vessel. An optical length modulator in the reference arm of the interferometer provides ramp wise modulation of optical length and a Doppler frequency shift for the reference beam. The polarization diversity detection scheme and two envelope detectors tuned for the Doppler frequency, perform measurements of the intensities of the two linear polarizations of the retroreflected light. Combined with current values of the optical length of the reference arm and angular position of the sweeping mirror, this information is used for reconstruction of the cross-sectional images of the vessel in two polarizations. These images are used for measurements of the geometry and recognition of the morphology of an intravascular obstruction which is utilized for diagnosis of atherosclerosis and real-time guidance of interventional procedures like PTCA.

Claims

1. An interferometer for performing real time intravascular imaging, comprising:

a low coherence light source;

means for splitting the light source into a sampling beam and reference beam;

a reference optical path for receiving the reference beam, wherein the reference optical path leads to a means for causing ramp-wise modulation of a length of the reference optical path length;

a sampling optical path for receiving the sampling beam, the sampling optical path leading to a vascular sample and terminating at an inner wall of a vessel;

means for ramp-wise modulation of a length of the reference optical path length comprising a spiral optical element with a spiral receiving surface, a rotational shaft, the spiral receiving surface mounted on the rotational shaft, the shaft having an axis positioned substantially parallel with axis of the reference beam as the reference beam approaches the spiral receiving surface, and means for causing the shaft to rotate;

means for combining reflections from the reference optical path and sampling optical path;

a polarization means for decomposition of each of said optical outputs into two optical signals with orthogonal polarizations;

photodetection means for generating electrical signals from the resulting combined optical signals;

electronic substation means for subtracting two electrical signals corresponding to the same polarizations for reducing excessive noise of the light source;

envelope detecting means for forming an envelope of an amplitude of the electrical signals from the photodetection means; and

means for processing said electrical signals to form a cross-sectional image of the vessel.

2. The interferometer of claim 1, wherein the spiral optical element comprises a rotating spiral reflective surface for receiving a reference beam.

3. The interferometer of claim 1, wherein the spiral optical element comprises a rotating optically transparent member having a spiral surface for receiving a reference beam.

4. The interferometer of claim 1 and further comprising an imaging guidewire comprising:

an elongated cylindrical body having a proximal and distal end and a throughbore extending therethrough;

an optical fiber extending through the throughbore;

an optical connection means for optically connecting the optical fiber to the light source.

5. The interferometer of claim 1 wherein the means for causing the shaft to rotate further comprises an electromotor means for causing the shaft to rotate at a speed between about 5 and about 500 Hc.

6. The interferometer of claim 1 wherein the means for combining reflections from the reference optical path and sampling optical path further comprises an electromotor having a shaft, wherein a mirror is mounted onto the shaft, and further comprising a control means for:

providing current to the electromotor;

tracking the angular position of the mirror;

controlling a rotational speed of the shaft; and

sending signals to the means for processing the electrical signals.

7. A device for real time intravascular imaging, comprising:

an imaging guidewire having an elongated hollow body with a distal and proximal end and a throughbore extending therethrough, an optical fiber positioned in the throughbore;

a micro optical collimator positioned at distal end of the fiber;

a housing proximate the distal end of the guidewire proximate said collimator;

a mirror positioned in the housing and capable of rotating about a central axis of the throughbore;

micromotor means for rotating the mirror; and

connection means for providing electrical connection of the micromotor means to a power source;

a fiber optic interferometer comprising;

a low coherence light source;

a beam splitting means for splitting light into a reference and a sampling beam;

a reference arm for receiving the reference beam;

means for causing ramp-wise modulation of a length of the reference arm comprising a spiral optical element with a spiral receiving surface, a rotational shaft, the spiral receiving surface mounted on the rotational shaft, the shaft having an axis positioned substantially parallel with an axis of the reference beam as the reference beam approaches the spiral receiving surface, and means for causing the shaft to rotate;

a sampling arm extending through the guidewire, terminating at a vessel wall;

means for combining optical signals from the reference arm and the sampling arm and for generating two optical outputs;

a polarization means for decomposition of each of said optical outputs into two optical signals with orthogonal polarizations;

photodetection means for converting the optical signals to electrical RF signals;

electronic subtraction means for subtracting two electrical signals corresponding to the same polarizations for reducing excessive noise of the light source;

envelope detection means for restoration of the amplitude envelope of the RF signals;

means for converting the outputs from the envelope detection means into digital signals;

computer means for receiving the digital signals and processing the information to reconstruct cross-sectional images of a vessel; and

display means for displaying cross-sectional images of the vessel.

8. An imaging guidewire, comprising:

an elongated hollow body with a distal end, a proximal end and a throughbore extending longitudinally therethrough;

an optical fiber extending through the throughbore;

a micro optical collimator positioned at a distal end of the optical fiber;

an optical connector means for connecting the proximal end to a low coherence interferometer;

a hermetic housing mounted proximate said distal end of the hollow body proximate the collimator;

a mirror mounted within said housing for reflecting light emanating from said collimator in a generally transverse direction and to the vessel walls, said mirror mounted for rotation about an axis substantially in line with a central throughbore axis;

a micromotor means positioned proximate the distal end for rotating the mirror; and

connection means for providing electrical connection of the micromotor means to a power source.

9. The imaging guidewire of claim 8, wherein the mirror comprises a reflective surface located in a plane that intersections a longitudinal axis of a light beam exiting the micro optical collimator, wherein an angle formed between the longitudinal axis and the plane is between about 35 and about 55 degrees.

10. The imaging guidewire of claim 8, wherein the elongated hollow body has an outer surface, and the connection means comprising at least on electrically conductive contact positioned on the outer surface of the elongated body.

11. The imaging guidewire of claim 8, wherein the optical fiber is a single mode fiber.

12. The imaging guidewire of claim 8 and further comprising a balloon located proximate the distal end and enclosing the housing, and a syringe fluidly connected to the balloon.