Patent Document:

the present invention relates to a catheter imaging system and , more specifically , to a catheter imaging system which uses the gaussian profile of projected laser dots to determine plaque depth in blood vessels . the following description is presented to enable one of ordinary skill in the art to make and use the invention and to incorporate it in the context of particular applications . various modifications , as well as a variety of uses in different applications will be readily apparent to those skilled in the art , and the general principles defined herein may be applied to a wide range of embodiments . thus , the present invention is not intended to be limited to the embodiments presented , but is to be accorded the widest scope consistent with the principles and novel features disclosed herein . in the following detailed description , numerous specific details are set forth in order to provide a more thorough understanding of the present invention . however , it will be apparent to one skilled in the art that the present invention may be practiced without necessarily being limited to these specific details . in other instances , well - known structures and devices are shown in block diagram form , rather than in detail , in order to avoid obscuring the present invention . the reader &# 39 ; s attention is directed to all papers and documents which are filed concurrently with this specification and which are open to public inspection with this specification , and the contents of all such papers and documents are incorporated herein by reference . all the features disclosed in this specification , ( including any accompanying claims , abstract , and drawings ) may be replaced by alternative features serving the same , equivalent or similar purpose , unless expressly stated otherwise . thus , unless expressly stated otherwise , each feature disclosed is one example only of a generic series of equivalent or similar features . furthermore , any element in a claim that does not explicitly state “ means for ” performing a specified function , or “ step for ” performing a specific function , is not to be interpreted as a “ means ” or “ step ” clause as specified in 35 u . s . c . section 112 , paragraph 6 . in particular , the use of “ step of ” or “ act of ” in the claims herein is not intended to invoke the provisions of 35 u . s . c . 112 , paragraph 6 . the present invention relates to a catheter imaging system and , more specifically , to a catheter imaging system which uses the gaussian profile of projected laser dots to determine plaque depth in blood vessels . it has been observed that when a narrow band laser beam shines on a plaque surface , both the gaussian profile and the intensity profile of the laser dot vary depending on the thickness of the fat and cholesterol comprising the plaque . the present invention utilizes this phenomenon to measure the depth of plaque on the inner walls of blood vessels . fig1 is an illustration showing an imaging device 100 in accordance with the present invention situated within a blood vessel having fat and cholesterol plaque 102 on the inner vessel walls 104 . imaging components including a mirror 106 , fiber optic bundle 108 having a terminus 109 , and sensor 110 reside inside a catheter tube 112 having a transparent catheter balloon 114 which expands to meet the plaque 102 surface . in a desired aspect , the imaging components are capable of moving axially 115 within the catheter tube 112 . in a further desired aspect , the mirror 106 is substantially conical in shape , although any mirror shape capable of performing the reflection needs of the system may be used . the conical mirror 106 is held at an apex by a holder 116 at the center of the fiber optic bundle 108 . the holder 116 can be independent or connected with a guide wire of the catheter . a projection portion 119 of the fiber optic bundle 108 are used to project several narrow band laser beam dots 120 around the center , which are then reflected by the conical mirror 106 and transmitted through the transparent balloon 114 to the plaque tissues 102 on the vessel walls 104 . the projected laser dots 120 on the plaques 102 are reflected back as an image signal 121 to the fiber optic bundle 108 , where a receiving portion 122 of the fiber optic bundle 108 receives and transmits the reflected image signal 121 to the sensor 110 . the sensor 110 can be anything known in the art for capturing a light signal , including a camera , charge coupled device ( ccd ), diode , or photo cell . a non - coherent portion of the reflected image signal 121 is expected to have a substantially gaussian profile . the shape of the gaussian profile or a best fit curve of the diffusive image intensity of the reflected laser dot varies with respect to the depth of the plaque . therefore , the depth of the plaque on the blood vessel can be resolved by measuring the laser dot profile . this method works on the non - coherent portions of the reflected light , or it can be used in conjunction with optical coherence tomography . it should be noted that other research , as described in u . s . patent publication no . us 2005 / 0251116 a1 , incorporated by reference as though fully disclosed herein , uses a prism coupled with a mechanical rotation device to obtain images of the surrounding tissues from all angles . this system , however , will cause major challenges in packaging due to the relative large size of the mechanical equipment . in contrast , since the small conical mirror of the present invention can reflect the laser beam to all angles of the surrounding tissues as well as direct the images from all angles back to the fiber bundle , the rotating mechanical equipment of the above cited publication is not required . furthermore , the configuration of the present invention allows the entire plaque surface surrounding the balloon catheter to be measured simultaneously . fig2 a shows the gaussian profile 200 of a cross section 202 of a diffusive laser dot image 204 on a chicken fat surface with a depth of 2 . 2 mm . the diameter of the gaussian profile 200 is 100 pixels . similarly , fig2 b shows the gaussian profile 206 of a cross section 208 of a diffusive laser dot image 204 on a thicker chicken fat surface with a depth of 4 . 4 mm . the diameter of the gaussian profile is 120 pixels . as can be seen from the graphs in fig2 a and 2b , the diameter of the diffusive dot image and therefore width of the gaussian profile increases with the depth of the fat layer . a normalized graph of gaussian profiles at various depths can be constructed using experimental data as shown in fig3 . the graph in fig3 plots fat layer depth 300 against normalized gaussian profile diameter 302 . the graph contains two best fit curves , one for a series of data points taken for chicken fat 304 , and one for a series of data points taken for mayonnaise 306 . a similar best fit curve can be constructed for a layer of human fat and cholesterol as found in the plaques on blood vessel walls . when a patient is tested using the catheter imaging system of the present invention , the gaussian profile obtained is compared to a best - fit curve in a normalized graph as in fig3 to determine the depth of the plaque on the patient &# 39 ; s vessel walls . the present invention also comprises the general method of obtaining depth information of material coating from an intensity profile of reflected light . the acts in the method are illustrated in fig4 . the first act is illuminating 400 the surface of a material layer with coherent light . the material layer may be a layer of blood vessel plaque , but the method is generally applicable to any material layer which will produce a reflected image having a substantially gaussian intensity distribution . the light reflected from the material layer will be non - coherent and have a substantially gaussian profile . the non - coherent light is then collected 402 and directed to a sensor where the non - coherent light image is captured 404 by the sensor . the length of a diametrical profile of the reflected non - coherent image is then measured 406 and compared with previously obtained normalized graphical data representing the relationship between profile diameter and material layer depth ( as in fig3 ), whereby the depth of the material layer is obtained 408 . as can be appreciated by one skilled in the art , the present invention also comprises a data processing system for executing the method of the present invention , as previously mentioned . a block diagram depicting the components of an image processing system of the present invention is provided in fig5 . the image processing system 500 comprises an input 502 for receiving information from at least one sensor for use in detecting image intensity of the non - coherent light captured by the sensor . note that the input 502 may include multiple “ ports .” typically , input is received from at least one sensor , non - limiting examples of which include video image sensors . an output 504 is connected with the processor for providing information regarding the intensity profile of the image to other systems in order that a network of computer systems may serve as an image processing system . output may also be provided to other devices or other programs ; e . g ., to other software modules , for use therein . the input 502 and the output 504 are both coupled with a processor 506 , which may be a general - purpose computer processor or a specialized processor designed specifically for use with the present invention . the processor 506 is coupled with a memory 508 to permit storage of data and software that are to be manipulated by commands to the processor 506 . the present invention also comprises a computer program product . an illustrative diagram of a computer program product embodying the present invention is depicted in fig6 . the computer program product 600 is depicted as an optical disk such as a cd or dvd . however , as mentioned previously , the computer program product generally represents computer - readable instruction means stored on any compatible computer - readable medium . the term “ instruction means ” as used with respect to this invention generally indicates a set of operations to be performed on a computer , and may represent pieces of a whole program or individual , separable , software modules . non - limiting examples of “ instruction means ” include computer program code ( source or object code ) and “ hard - coded ” electronics ( i . e . computer operations coded into a computer chip ). the “ instruction means ” may be stored in the memory of a computer or on a computer - readable medium such as a floppy disk , a cd - rom , and a flash drive .

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