Dual modality imaging system for coregistered functional and anatomical mapping

Abstract

A real-time imaging system that provides ultrasonic imaging and optoacoustic imaging coregistered through application of the same hand-held probe to generate and detect ultrasonic and optoacoustic signals. These signals are digitized, processed and used to reconstruct anatomical maps superimposed with maps of two functional parameters of blood hemoglobin index and blood oxygenation index. The blood hemoglobin index represents blood hemoglobin concentration changes in the areas of diagnostic interest relative to the background blood concentration. The blood oxygenation index represents blood oxygenation changes in the areas of diagnostic interest relative to the background level of blood oxygenation. These coregistered maps can be used to noninvasively differentiate malignant tumors from benign lumps and cysts.

1 . An imaging system for visualization of slices into the depth of tissue of at least a portion of a body, comprising:
 a hand-held imaging probe comprising a light emitting portion and an array of ultrasonic transducers;   a processing system configured to receive data originating from the hand-held imaging probe and to process at least three independent images based at least in part upon said data, the three independent images together comprising:
 a first functional image reflecting distribution of total hemoglobin concentration; 
 a second functional image reflecting distribution of blood oxygen saturation; and 
 a morphological image of tissue structures; 
   the processing system being further configured to substantially co-register the first functional image, the second functional image, and the morphological image in time and space, and to output a substantially co-registered image.   
     
     
         2 . The system of  claim 1 , in which the light emitting portion and the array of ultrasonic transducers in the hand-held imaging probe are arranged in a generally flat linear shape. 
     
     
         3 . The system of  claim 1 , in which the light emitting portion and the array of ultrasonic transducers in the hand-held imaging probe are arranged in a curved concave arc shape. 
     
     
         4 . The system of  claim 1 , in which the hand-held imaging probe is configured to produce at least two optical beams, one on each side of the array of ultrasonic transducers, so as to deliver optical energy to a skin surface at such angle and such distance between them that the optical beams merge into one beam within a distance of skin thickness under the array of ultrasonic transducers. 
     
     
         5 . The system of  claim 1 , further comprising one or more dual-wavelength short-pulse lasers. 
     
     
         6 . The system of  claim 1 , further comprising a plurality of single-wavelength short pulse lasers. 
     
     
         7 . The system of  claim 1 , further comprising a fiberoptic light delivery system. 
     
     
         8 . The system of  claim 1 , in which the system is configured to present images substantially in real time by operating at a video frame rate. 
     
     
         9 . The system of  claim 1 , in which the hand-held optoacoustic probe is configured to deliver optical energy from either under a face of said array of transducers or its side. 
     
     
         10 . The system of  claim 1 , in which the hand-held imaging probe comprises an acoustic lens. 
     
     
         11 . The system of  claim 10 , in which the acoustic lens comprises optically reflective materials. 
     
     
         12 . The system of  claim 11 , in which the optically reflective materials comprise a thin, highly optically reflective metallic layer that removes image artifacts associated with light interactions with the acoustic lens. 
     
     
         13 . The system of  claim 11 , in which the acoustic lens is formed from a white opaque material. 
     
     
         14 . The system of  claim 11 , in which the thin, highly optically reflective metallic layer comprises aluminum, gold, or silver. 
     
     
         15 . The system of  claim 1 , in which the hand-held imaging probe comprises an output fiber bundle with multiple sub-bundles. 
     
     
         16 . The system of  claim 15 , in which said multiple sub-bundles are shaped to provide even illumination of the image plane and smooth illumination edges so as to reduce edge-related optoacoustic artifacts. 
     
     
         17 . The system of  claim 1 , in which the array of ultrasonic transducers comprises ultrasonic transducers having an ultrawide ultrasonic frequency band of sensitivity, with bandwidth of up to 200% from the central frequency. 
     
     
         18 . The system of  claim 1 , in which the hand-held imaging probe comprises an input fiber bundle that is circular in shape to match an incident laser beam. 
     
     
         19 . The system of  claim 1 , in which the hand-held imaging probe comprises an input fiber bundle having a thermally fused fiber bundle tip such that substantially all fibers in the bundle are reshaped to avoid loss of light through spaces between fibers. 
     
     
         20 . The system of  claim 1 , in which the hand-held imaging probe comprises a fiber bundle that is divided into at least two sub-bundles, with fibers in each sub-bundle being randomized such that two neighboring fibers at an input appear in different sub-bundles of the output fiber bundle. 
     
     
         21 . The system of  claim 1 , in which the hand-held imaging probe comprises a fiber bundle that is divided into at least two sub-bundles to form fiber bundle paddles, with at least one paddle placed on each side of the ultrasonic transducer array, each paddle, in turn, being divided into smaller sub-bundles, each smaller sub-bundle being in a slot in said paddle so as to provide controlled profile of an optical beam. 
     
     
         22 . The system of  claim 1 , in which the hand-held imaging probe comprises fiber bundle, which produces an optical beam that is shaped to complement a size and shape of the ultrasonic transducer array. 
     
     
         23 . The system of  claim 1 , in which the hand-held imaging probe comprises an output fiber bundle having triangular shaped ends so as to allow an output beam to have smooth edges of optical fluence after passing through a light diffuser. 
     
     
         24 . The system of  claim 1 , in which the hand-held imaging probe comprises a plurality of optical windows, each comprising one or more anti-reflection-coated plates with acoustic impedance matching that of tissues to be imaged. 
     
     
         25 . The system of  claim 24 , in which the anti-reflection-coated windows comprise glass, polymer or other solid optically transparent material. 
     
     
         26 . The system of  claim 1 , in which the hand-held imaging probe comprises:
 first and second light diffusers;   first and second optical windows;   at least two output fiber bundles arranged such that optical beams respectively emerging therefrom pass through the respective light diffusers, then pass through the respective optical windows, then merge at least partially.   
     
     
         27 . The system of  claim 1 , further comprising a three-dimensional positioning system configured to control position of the hand-held probe so as to allow assembly of three-dimensional volumetric images of the body from two-dimensional slices made though a depth of tissue obtained by scanning the hand-held probe along the surface of at least a portion of the body. 
     
     
         28 . The system of  claim 1 , in which the handheld imaging probe further comprises an acoustic lens formed from a material that allows it to reflect and scatter light from illumination components with substantially no absorption of such light, and yet be optically opaque. 
     
     
         29 . The system of  claim 28 , in which the acoustic lens is formed from silicon rubber. 
     
     
         30 . The system of  claim 29 , in which the silicon rubber is filled with titanium dioxide. 
     
     
         31 . The system of  claim 29 , in which the silicon rubber is filled with barium sulfate powder. 
     
     
         32 . The system of  claim 1 , in which the handheld imaging probe further comprises a housing that provides hypo-echoic encapsulation of the probe. 
     
     
         33 . The system of  claim 32 , in which internal or external parts of the housing comprise materials that do not absorb near-infrared laser light. 
     
     
         34 . The system of  claim 33 , in which internal or external parts of the housing comprise materials having low thermal expansion properties such that the housing does not emit ultrasound after absorption of laser light. 
     
     
         35 . The system of  claim 1 , in which an assembly of the array of ultrasonic transducers is made of hypo-echoic material. 
     
     
         36 . The system of  claim 1 , further comprising a layer of hypo-echoic material between an assembly of the array of ultrasonic transducers and a fiberoptic assembly to avoid generation of ultrasound upon interaction of light with assembly of the array of ultrasonic transducers. 
     
     
         37 . The system of  claim 1 , in which the hand-held imaging probe comprises a fiber bundle that is divided into at least two sub-bundles to form at least one fiber bundle paddle, said at least one fiber bundle paddle being located on one side of the ultrasonic transducer array.