Opto-acoustic imaging devices and methods

0001(Field of invention) The present invention relates to the field of optical imaging, and more specifically to the design of optical fiber probes for optical coherence tomography (OCT) and other optical imaging such as ultrasound.

0002(background) In recent years, the potential causes of sudden heart attacks (acute myocardial infarction or AMI) have been the focus of much attention. The older predominant theory of loose occlusion of coronary arteries provides widespread histopathological evidence that AMI is the result of rupture of the coronary wall, especially "vulnerable plaque". It has been superseded by a new theory based on it. Fragile plaques, also known as thin-capped fibro-Artheroma (TCFA), are thin fibrous forms that cover the lipid pool located beneath the arterial wall. Characterized by a cap. Conventional X-ray examination-based angiography techniques can be used to detect narrowing of arteries. However, direct observation of the surface of the arterial wall is essential to detect TCFA. Therefore, there is a need for probe designs that allow the detection and visualization of subsurface biological tissues and lipid pools.

<p num="0003"> (Outline of the invention) The present invention relates to methods and devices for imaging biological tissues and other materials using light and acoustic techniques. The combination of optical coherence tomography (OCT), coherence imaging techniques, and intravascular ultrasound (IVUS) is ideal for biological tissues such as arterial walls via small-diameter probes. Suitable for subsurface visualization. The disclosed method is based on a combination of IVUS (intravascular ultrasound) technology and OCT (optical coherence tomography) technology that favorably overcomes the weaknesses of each individual technique. In particular, the combination of both IVUS and OCT enables a robust probe with many advantages.</p><p num="0004"> IVUS is an imaging technology with intermediate resolution (~ 100um) and intermediate penetrating power (~ 2cm). In contrast, OCT is a high resolution (5-20um), shallow penetrating (~ 1mm) technology. Neither technique can individually detect the condition of the arterial wall. For example, cap thickness in potentially dangerous TCFA can range from about 25 um to about 100 um. This range is within the measurement resolution range of OCT, but exceeds the measurement resolution range of IVUS. Conversely, a deep lipid pool under a thin cap greatly increases the risk of AMI. OCT cannot be used to easily penetrate such deep lipid pools, while IVUS can be easily used to visualize such pools.</p><p num="0005"> It is an object of the present invention to describe devices and methods in which IVUS and OCT can be performed simultaneously. A further object of the present invention is to describe an OCT optical sensor and an IVUS ultrasonic sensor that can be combined in the same catheter delivery system.</p><p num="0006"> One advantage of the present invention is the alignment characteristics of OCT and ultrasonic sensors such that common registration of cross-sectional images obtained by two sensors can be obtained with high accuracy. Previous descriptions of such combined catheters did not provide the level of common registration required. Common registration is important because the morphology of the coronary arteries often changes rapidly over distances of less than 1 millimeter in the longitudinal direction.</p><p num="0007"> Another object of the present invention is to describe a sensor structure in which two probe beams are oriented at substantially the same angle with respect to the longitudinal axis of the catheter. Here again, this facilitates proper common registration of images. The different firing angles of the probe beams imply that the two images diverge from each other with depth. This divergence correction calculation is complex and can lead to errors in the image representation.</p><p num="0008"> Another object of the present invention is to describe an efficient method of providing both light energy and electrical energy to a rotation sensor assembly at the tip of a catheter. The use of various torque wires and coated fibers that act as coaxial signal lines saves valuable space within the catheter body.</p><p num="0009"> A further object of the present invention is a probe mechanism that simultaneously reduces unwanted parasitic acoustic and light back-reflection while being aligned and still providing the functionality of other probe assemblies. And to describe the configuration.</p><p num="0010"> Yet another object of the present invention is to describe an efficient rotation mechanism for simultaneously connecting both electrical and light energy to a catheter.</p><p num="0011"> Another object of the present invention is a capacitive micromachine ultrasonic transducer (CMUT) to create a dual element probe such that both the ultrasonic beam and the light beam focus on substantially the same tissue spots at the same time. It is to describe the combined probes that utilize.</p><p num="0012"> In one aspect, the invention relates to a probe. The probe comprises a sheath and a flexible, bidirectionally rotatable optical subsystem positioned within the sheath, the optical subsystem comprising a transmittable fiber, the optical subsystem being defined. It is possible to transmit and collect light of a predetermined range of wavelengths along a first beam having a beam size. The probe also includes an ultrasonic subsystem, which is positioned within the sheath and delivers energy in a predetermined range of frequencies along a second beam having a second predetermined beam size. Adapted to propagate. In one embodiment, the first beam and a portion of the second beam scan the same area at different time points. Alternatively, the first beam may be directed to scan the first band of the region substantially adjacent to the second band of the region where the second beam scans the second band. ..</p><p num="0013"> In another aspect, the invention relates to a system for medical examination. The system includes a first image processing device and a second image processing device. The system also includes a probe for electrical communication between the first image processing device and the second image processing device. The probe then directs and radiates light to an area adjacent to the catheter tip that is introduced into the examination area and directs the reflected light from the illuminated examination area to the first image processing device. The first sensor of an imaging system for optical coherence tomography with optical fiber and the second of an intravascular ultrasonic imaging system for transmitting and receiving acoustic signals as electrical signals to the second image processing device. Includes sensors and. Further, the system also includes a display device for outputting an image processed by the first image processing device and the second image processing device.</p><p num="0014"> In yet another aspect, the invention relates to an imaging probe adapted for insertion into a lumen. The probe is an array of a sheath having a core and an end face, an optical subsystem having an optical focus, an optical subsystem positioned within the core, and an ultrasonic transducer having an acoustic focus. Includes an array that is placed on a portion of the end face.</p><p num="0015"> In yet another aspect, the present invention relates to a probe. The probe is a sheath and a first ultrasonic subsystem, the first ultrasonic subsystem being positioned within the sheath and adapted to propagate energy along the first vector. A first ultrasonic subsystem and a second ultrasonic subsystem, the second ultrasonic subsystem being positioned within the sheath and propagating energy along a second vector. The first vector and the second vector include a second ultrasonic subsystem that is substantially parallel and in opposite directions.</p><p num="0016"> In yet another aspect, the present invention relates to a method of imaging a tissue area. The method includes inserting an imaging probe that combines ultrasound and OCT into the lumen, performing ultrasound imaging, and performing optical coherence tomography imaging. In one embodiment of the method, the flash solution is applied during optical coherence tomographic imaging. In another related method of this aspect, ultrasound imaging is performed at the same time as optical coherence tomography imaging.</p><p num="0017"> In yet another aspect, the present invention relates to a method of imaging a tissue region. The method involves inserting an imaging probe that combines ultrasound and OCT into the lumen and performing ultrasound imaging at the same time as optical coherence tomography imaging, where the flash solution is during imaging. Applies.</p><p num="0018"> An additional aspect of the invention includes a method of making a probe that includes a sensor array, where each sensor includes an ultrasonic transducer and a driver.</p><p num="0019"> It should be understood that the terms "a", "an", and "the" mean "one or more" unless otherwise explicitly stated. ..</p><p num="0020"> The above and other features and advantages of the invention, as well as the invention itself, are more fully understood from the following description and the accompanying drawings and claims.</p>

0021The objects and features of the present invention may be better understood by reference to the accompanying drawings and claims. The drawings are not necessarily on scale and instead are generally focused on exemplifying the principles of the invention. The drawings associated with the disclosure are treated individually in the disclosure when they are introduced.<figref num="1A">FIG. 1A depicts a cross-sectional view of a vertically aligned IVUS / OCT probe according to an exemplary embodiment of the invention.</figref><figref num="1B">FIG. 1B depicts a probe utilizing a metal coated fiber with a shielded tube according to an exemplary embodiment of the invention.</figref><figref num="1C">FIG. 1C depicts a probe that utilizes a coil of a torque cable assembly as a conductor, according to an exemplary embodiment of the invention.</figref><figref num="1D">FIG. 1D depicts a cross-sectional view of the probe embodiment depicted in FIG. 1C.</figref><figref num="1E">FIG. 1E depicts a probe containing two transducers adapted for operation at different frequencies, according to an exemplary embodiment of the invention.</figref><figref num="2">FIG. 2 depicts a rotary coupling mechanism for delivering both RF energy and light energy to a rotary probe assembly according to an exemplary embodiment of the invention.</figref><figref num="3">FIG. 3 depicts a rotary coupling mechanism in which a fixed coil is part of a probe interface unit, according to an exemplary embodiment of the invention.</figref><figref num="4">FIG. 4 depicts a probe tip in which CMUT technology is used to achieve a dual focus beam, according to an exemplary embodiment of the invention.</figref><figref num="5A">FIG. 5A depicts a fused OCT-IVUS chart according to an exemplary embodiment of the invention.</figref><figref num="5B">FIG. 5B depicts a fused OCT-IV US image according to an exemplary embodiment of the invention.</figref>

0022The invention described in the claims is more fully understood through the following detailed description, which should be read with the accompanying drawings. In this description, similar numbers indicate similar elements in various embodiments of the invention.

0023(Detailed description of the invention) The following description will refer to the accompanying drawings illustrating specific embodiments of the present invention. Other embodiments are possible and modifications may be made to the embodiments without departing from the spirit and scope of the invention. Therefore, the following detailed description is not intended to limit the invention. Rather, the scope of the invention is defined by the appended claims.

0024It should be understood that the order of the steps in the methods of the invention is not important as long as the invention is feasible. In addition, two or more steps may be performed simultaneously or in a different order than described herein unless specified in a different manner.

0025Figure 1A shows a conventional IVUS ultrasonic transducer 12, an optical transducer 14 including a tilted chip optical lens assembly 16 mounted on a single-mode optical fiber 18, and a standard compact size that delivers power to the IVUS ultrasonic transducer. A portion of an imaging probe 10a using an RF cable 20 and a torque cable 22 that provides a stable swivel rate for the assembly is illustrated.

0026Torque cables are generally suitable for this dual probe catheter because optical fibers are known to have very low torsional stiffness. For example, with approximately one millionth of the applied torque of Nm, a 1 cm long twist of a standard telecommunications fiber with a diameter of 125 μm is one degree. Therefore, it is impractical to expect the fiber to be sufficiently twisted and rigid to drive the entire assembly.

0027In FIG. 1A, both the optical transducer 12 and the IVUS ultrasonic transducer 14 minimize unwanted parasitic reflections reaching their respective transducers and aligned transverse "cuts" through the tissue. It is folded at an angle to create a "cut". As shown, the acoustic beam (ab) emanating from the transducer is parallel to the light beam (ob) emanating from the fiber. The directions of these two parallel beams are rotated by an angle α with respect to the vertical axis of the probe. As shown in the figure, a small amount of longitudinal displacement is acceptable.

0028As a first-order approximation, this acceptable displacement is the maximum beamwidth of the approximation for the combined probe 10a. In most cases, this will be the width of the ultrasonic beam, generally ranging from about 100um to 300um (OCT beamwidth is generally 25um). Keeping the longitudinal displacement below this longitudinal displacement limit ensures that the beams continue to overlap. In addition, directing the two beams 180 degrees opposite each other ensures easier real-time or post-processing alignment of the two images with respect to the overlay display.

0029Figure 1B depicts probe 10b for imaging with reduced overall diameter. Here, the metal-coated fiber 24 is shown inside the insulating tube 26. These two cylindrical surfaces (tube and coating), the dielectric constant of the insulator, and the thickness of the insulator can be configured to form a simple coaxial transmission line for the RF signal. Such RF signals can vary from 10MHz to 60MHz, depending on the design of the IVUS ultrasonic transducer.

0030FIG. 1C illustrates embodiment 10c of another probe with a different conduction mechanism. In particular, in the indicated probe 10c, the inner coil 28 and the outer coil 30 of the torque cable 22 form a coaxial transmission line 32. The insulating spacer 34 is inserted between the inner coil and the outer coil in order to prevent a short circuit state. The embodiment shown in Figure 1C allows RF power to be transmitted using integrated torque wires. In one embodiment, the transducer is coated with epoxy resin. In one embodiment, both the ultrasonic transducer and the optical fiber are driven by the same torque wire and rotate with each other. The end epoxy resin chip encloses the optical fiber, the ultrasonic transducer, and its associated feed wire. Therefore, epoxy resins are appropriately selected for their optical and acoustic properties, as well as the required electrical insulation. Various epoxy and silicone compounds that meet these requirements can be purchased and / or specially prepared.

0031FIG. 1D illustrates a cross section of the embodiment of FIG. 1C. The two wires connected to the transducers shown in Figures 1C and 1D are fixed and rotate with the transducer.

0032FIG. 1E illustrates an embodiment of another optical probe in which two IVUS ultrasonic transducers T1 and T2 operating at different frequencies are integrated within the device. The low frequency transducer T1 allows ultrasound to scan deeper areas, but reduces resolution. Conversely, the high frequency transducer T2 allows for increased resolution of ultrasound, but reduces penetration depth. In one embodiment, one transducer operates at about 5 MHz and the other transducer operates at about 60 MHz. By using the transducers in different frequency ranges, the optical probe gains the advantages of both transducers and alleviates the shortcomings of each transducer. This dual transducer probe is a combined OCT / IVUS in cases where very high resolution (about 10um, OCT) is not required due to the fairly high penetration (about 3-5cm) provided by the low frequency ultrasonic transducers. Achieve the same overall goals as catheters.

0033FIG. 2 depicts embodiment 40 of a probe incorporating a mechanism for transmitting both RF energy and light energy to a rotating assembly. In particular, a transformer scheme is used in which the first coil 42 is attached to the rotating assembly 44 and the second coil 46 is integrated with the connector 48 of the optical probe. This configuration has the advantage that both coils move with the assembly during the (longitudinal) "pull-back" scan operation. Such pullbacks are used in both OCT and IVUS scans. When connected with rotation, a spiral scanning pattern is created inside the lumen of the artery. However, this approach presents increased costs for disposable catheters.

0034FIG. 3 illustrates an alternative coupling scheme in which the fixed coil 42 is part of a drive unit 50, an electrified assembly that provides rotational and longitudinal movement. In this embodiment, the fixed coil must be permanent and long enough to efficiently connect RF energy to the rotating catheter coil over the entire pullback length. Incorporating a fixed coil into the drive unit imposes additional requirements on the drive electronics, but reduced catheter use provides overall cost savings.

0035Currently, conventional slip ring technology is widely used in the field of optical imaging. As an alternative to FIGS. 2 and 3, slip ring techniques can be used for the IVUS probes described herein. However, for probes with a central optical configuration, slip rings are more difficult to manufacture than IVUS alone.

0036FIG. 4 illustrates an embodiment comprising a capacitive micromachine ultrasound transducer (CMUT) 52 integrated within a coronary imaging probe 54. The advantage of CMUT is the small size of the transducers manufactured through traditional electronics CMOS processes. The small size and photolithographic fabrication allow customized arrays of transducers to be assembled with drive electronics on the same substrate. In this example, the array is formed in an annular region around the optical transducer. As a result, a aligned, aligned, and combined beam can be formed at a common focus, thereby eliminating the need for software registration and eliminating potential sources of error. However, this probe tip can be larger than the embodiment shown in FIG.

0037FIG. 5A illustrates a fused OCT-IV US image 56 in which the boundary line 58 is chosen near the permeation limit of OCT. By registering the associated images of ultrasound 60 and OCT scan 62 as shown, the clinician can view composite images showing additional physiological data. This approach can be used to image the subsurface lipid pool.

0038FIG. 5B illustrates a fused OCT / IVUS image in which the OCT portion appears in the center of the image and the IVUS portion appears in the periphery. The outer boundary roughly indicates the boundary where the two regions intersect.

0039Guide catheters are not shown in the embodiments depicted in the figure. In general, a guide catheter is a larger bore catheter used to introduce a smaller imaging catheter into the major arterial trunk. From the guide catheter, the flush solution can be ejected to create a clean, blood-free imaging area when OCT imaging is performed. In an alternative embodiment, the flush lumen may be included within the imaging catheter so that the flush solution is drained at the imaging chip rather than through the guide catheter.

0040Aspects and embodiments of the present invention may incorporate various components of various dimensions and materials, as known to those of skill in the art. Although various specific dimensions and materials are described herein, these exemplary materials are not intended to be limiting, but only to specify additional, more specific embodiments. For all of the measurements discussed below, the given dimensions also include a range greater than about 10% to 20% of the given dimensions and a range less than about 10% to 20% of the given dimensions. I'm out. In addition, for all of the measurements discussed below, the given dimensions also range from about 20% to greater than 50% of the given dimensions, and to less than about 20% to 50% of the given dimensions. Includes. Furthermore, for all of the measurements discussed below, the given dimensions also range from about 50% to greater than 100% of the given dimensions, and less than about 50% to 100% of the given dimensions. Includes range.

0041In one embodiment of the probe, the field window used is a transparent epoxy resin based window. Furthermore, in another embodiment, the transducer used has a first dimension of about 0.1 mm and a second dimension of about 0.5 mm. In one embodiment of the probe, the anterior viewing angle is about 10 degrees. In one embodiment of the probe, the end cap used comprises metal. In some embodiments, the probe may include a hollow core that is substantially filled with an epoxy resin material. In one embodiment, the width of the shielded RF cable is about 0.18 mm.

0042It should be recognized that the various aspects of the invention described in the claims relate to the subsets and substeps of the techniques disclosed herein. Moreover, the terms and expressions used herein are used as descriptive terms and are not used to limit them. Although there is no intention to exclude any equivalents of the features shown and described in using such terms and expressions, various modifications are within the claims of the present invention. It is recognized that it is possible with. Thus, in the appended claims and all their equivalents, the inventions specified and distinguished are the desired protections of the letter.

004310a, 10b, 10c imaging probe 12 IV US Ultrasonic Transducer 14 Optical Transducer 16-chip optical lens assembly 18 Single mode optical fiber 20 small RF cable 22 Torque cable 24 Metal-coated fiber 26 Insulated tube 28 Inner coil 30 outer coil 32 Coaxial transmission line 34 Insulation spacer 42 First coil 44 Rotating assembly 46 Second coil 48 connector 50 drive unit