News Column

Patent Issued for Opto-Acoustic Imaging Devices and Methods

June 30, 2014

By a News Reporter-Staff News Editor at Cardiovascular Week -- A patent by the inventors Schmitt, Joseph M. (Andover, MA); Petersen, Christopher (Carlisle, MA); Ohasi, Toro (Aichi, JP); Nakamatsu, Tetsuya (Arlington, MA), filed on September 14, 2012, was published online on June 17, 2014, according to news reporting originating from Alexandria, Virginia, by NewsRx correspondents (see also Lightlab Imaging Inc.).

Patent number 8753281 is assigned to Lightlab Imaging Inc. (Westford, MA).

The following quote was obtained by the news editors from the background information supplied by the inventors: "In recent years, the underlying cause of sudden heart attacks (acute myocardial infarctions or AMI) has been the subject of much attention. The older prevailing theory of gradual occlusion of the coronary artery has been superseded by a new theory based on extensive histopathologic evidence that AMI is the result of a rupture in the coronary artery wall, specifically a rupture of a 'vulnerable plaque.' A vulnerable plaque, also known as Thin Capped Fibro-Artheroma (TCFA), is characterized by a thin fibrous cap covering a lipid pool located under the artery wall. Conventional x-ray based angiographic techniques can be used to detect narrowing of the artery. However, directly seeing the surface of the artery wall is essential to detect TCFA. Accordingly, a need therefore exists for a probe design that enables detecting and visualizing subsurface biological tissues and lipid pools."

In addition to the background information obtained for this patent, NewsRx journalists also obtained the inventors' summary information for this patent: "The invention relates to methods and apparatus for imaging biological tissues and other materials using optical and acoustic imaging techniques. A combination of Optical Coherent Tomography (OCT), an interferometric imaging technology, and Intravascular Ultrasound (IVUS), is ideally suited to subsurface visualization of biological tissue, such as the artery wall, via small-diameter probes. The disclosed methods are based on a combination of IVUS (Intravascular ultrasound) and OCT (Optical Coherence Tomography) techniques that advantageously overcomes the weakness of each individual technique. In particular, the combination of both IVUS and OCT allows for a robust probe with many advantages.

"IVUS is a medium-resolution (.about.100 um), medium-penetration (.about.2 cm) imaging technique. In contrast, OCT is a high-resolution (5-20 um), shallow-penetration (.about.1 mm) technique. Neither technique individually can detect the state of the arterial wall. For example, the cap thickness in a potentially hazardous TCFA can range from .about.25 um to .about.100 um. This range is within the measurement resolution of OCT, but beyond the measurement resolution of IVUS. Conversely, deep lipid pools beneath a thin cap greatly increases the risk of an AMI. OCT cannot be used to readily penetrate such deep lipid pools, but IVUS can readily be used to visualize such pools.

"It is an object of the present invention to describe devices and methods whereby IVUS and OCT can be performed simultaneously. It is a further object of the invention to describe OCT optical sensors and IVUS ultrasound sensors that can be combined into the same catheter delivery system.

"One advantage of the invention is the aligned nature of the OCT and ultrasound sensors such that co-registration of the cross-sectional images obtained by the two sensors can be obtained with high precision. Previous descriptions of such combined catheters did not provide the co-registration levels needed. Co-registration is important because coronary morphology changes rapidly, often in less than a millimeter of longitudinal distance.

"It is another object of the invention to describe a sensor structure wherein two probe beams are orientated at substantially the same angle with respect to the longitudinal axis of the catheter. Again, this is to facilitate proper co-registration of the images. Differing launch angles of the probe beams implies that the two images diverge each other with depth. Computational correction of this divergence is complex and can lead to errors in image presentation.

"It is another object of this invention to describe efficient methods of providing both optical and electrical energy to the rotating sensor assembly at the tip of the catheter. Using various torque wire and coated fibers to acts as co-axial signal lines saves valuable space within a catheter body.

"It is a further object of the invention to describe mechanisms and configurations of the probe that will simultaneously reduce unwanted parasitic acoustical and optical back-reflections while still providing an aligned and otherwise functional probe assembly.

"It is yet another object of the invention to describe efficient rotary mechanisms for coupling both electrical and optical energy simultaneously into the catheter.

"It is another object of the invention to describe a combined probe utilizing capacitive micro-machined ultrasonic transducers (CMUT) to create a dual element probe such that both the ultrasound and optical beams focus on substantially the same tissue spot simultaneously.

"In one aspect, the invention relates to a probe. The probe includes a sheath, a flexible, bi-directionally rotatable, optical subsystem positioned within the sheath, the optical subsystem comprises a transmission fiber, the optical subsystem capable of transmitting and collecting light of a predetermined range of wavelengths along a first beam having a predetermined beam size. The probe also includes an ultrasound subsystem, the ultrasound subsystem positioned within the sheath and adapted to propagate energy of a predetermined range of frequencies along a second beam having a second predetermined beam size. In one embodiment, a portion of the first and second beams scan the same region at different points in time. Alternatively, the first beam can be directed to scan a first band of a region that is substantially adjacent to a second band of the region, wherein the second beam scans the second band.

"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, in electrical communication with the first and second image processing devices. In turn, the probe includes a first sensor of are imaging system for optical coherence tomography having an optical fiber for directing and emitting light into an area adjacent to a catheter tip introduced into an examination area and for directing reflected light from the illuminated examination area to the first image processing device; and a second sensor of an intravascular ultrasound imaging system for transmitting and receiving acoustic signals to a second image processing device as electrical signals. Further, the system also includes a display device for outputting of images processed by the first and the second image processing devices.

"In yet another aspect, the invention relates to an imaging probe adapted for insertion in a lumen. The probe includes a sheath having a core and an endface, an optical subsystem having an optical focus, the optical subsystem positioned within the core; and an array of ultrasound transducers having an acoustic focus, the array disposed on a portion of the endface.

"In still another aspect, the invention relates to a probe. The probe includes a sheath, a first ultrasound subsystem, the first ultrasound subsystem positioned within the sheath and adapted to propagate energy along a first vector, and a second ultrasound subsystem, the second ultrasound subsystem positioned within the sheath and adapted to propagate energy along a second vector, wherein the first and second vectors are substantially parallel and opposite in direction.

"In yet another aspect, the invention relates to a method of imaging a tissue region. The method includes the steps of inserting a combination ultrasound and OCT imaging probe in a lumen, and performing ultrasound imaging, and then performing optical coherence tomography imaging. In one embodiment of this method a flush solution is applied during the optical coherence tomography imaging. In another related method of this aspect, the ultrasound imaging is performed simultaneously with the optical coherence tomography imaging.

"In still another aspect, the invention relates to a method of imaging a tissue region, the method comprising the steps of inserting a combination ultrasound and OCT imaging probe in a lumen, performing ultrasound imaging simultaneously with optical coherence tomography imaging whereby a flush solution is applied during the imaging.

"Additional aspects of the invention include methods of fabricating probes that include sensor arrays, wherein each sensor includes an ultrasound transducer and a driver.

"It should be understood that the terms 'a,' 'an,' and 'the' mean 'one or more,' unless expressly specified otherwise.

"The foregoing, and other features and advantages of the invention, as well as the invention itself, will be more fully understood from the description, drawings, and claims which follow."

URL and more information on this patent, see: Schmitt, Joseph M.; Petersen, Christopher; Ohasi, Toro; Nakamatsu, Tetsuya. Opto-Acoustic Imaging Devices and Methods. U.S. Patent Number 8753281, filed September 14, 2012, and published online on June 17, 2014. Patent URL:

Keywords for this news article include: Cardiology, Lightlab Imaging Inc.

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Source: Cardiovascular Week

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