Abstract:
A scanner for a medical optical imaging device, comprises an illumination source positioned to direct emitted light into a breast positioned below a support surface; a plurality of detectors positioned to detect light emerging from the breast; and a container disposed below the illumination source and the detectors adapted to trap light reflected from the breast.

Description:
RELATED APPLICATION  
       [0001]    This a nonprovisional application claiming the priority benefit of provisional application Ser. No. 60/197,415, filed Apr. 14, 2000, which is hereby incorporated by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention generally relates to diagnostic medical imaging apparatus and more particularly to a mammography machine that employs a near-infrared laser as a radiation source.  
         BACKGROUND OF THE INVENTION  
         [0003]    Cancer of the breast is a major cause of death among the American female population. Effective treatment of this disease is most readily accomplished following early detection of malignant tumors. Major efforts are presently underway to provide mass screening of the population for symptoms of breast tumors. Such screening efforts will require sophisticated, automated equipment to reliably accomplish the detection process.  
           [0004]    The x-ray absorption density resolution of present photographic x-ray methods is insufficient to provide reliable early detection of malignant tumors. Research has indicated that the probability of metastasis increases sharply for breast tumors over 1 cm size. Tumors of this size rarely produce sufficient contrast in a mammogram to be detectable. To produce detectable contrast in photographic mammograms, 2-3 cm dimensions are required. Calcium deposits used for inferential detection of tumors in conventional mammography also appear to be associated with tumors of large size. For these reasons, photographic mammography has been relatively ineffective in the detection of this condition.  
           [0005]    Most mammographic apparatus in use today in clinics and hospitals require breast compression techniques which are uncomfortable at best and in many cases painful to the patient. In addition, x-rays constitute ionizing radiation which injects a further risk factor into the use of mammographic techniques as most universally employed.  
           [0006]    Ultrasound has also been suggested, as in U.S. Pat. No. 4,075,883, which requires that the breast be immersed in a fluid-filled scanning chamber. U.S. Pat. No. 3,973,126 also requires that the breast be immersed in a fluid-filled chamber for an x-ray scanning technique.  
           [0007]    In recent times, the use of light and more specifically laser light to noninvasively peer inside the body to reveal the interior structure has been investigated. This technique is called optical imaging. Optical imaging and spectroscopy are key components of optical tomography. Rapid progress over the past decade have brought optical tomography to the brink of clinical usefulness. Optical wavelength photons do not penetrate in vivo tissue in a straight line as do x-ray photons. This phenomenon causes the light photons to scatter inside the tissue before the photons emerge out of the scanned sample.  
           [0008]    Because x-ray photon propagation is essentially straight-line, relatively straight forward techniques based on the Radon transform have been devised to produce computed tomography images through use of computer algorithms. Multiple measurements are made through 360° around the scanned object. These measurements, known as projections, are used to back project the data to create an image representative of the interior of the scanned object.  
           [0009]    The detectable signals in an optical breast scanning device are at a very low level. Ambient light must be excluded from the scanning area. Reflections inside the scanner can cause image artifacts or otherwise cause the reconstructed images to be of little use.  
         OBJECTS AND SUMMARY OF THE INVENTION  
         [0010]    It is an object of the present invention to provide a scanner for a medical optical imaging device that suppresses optical reflections within the scanning chamber to minimize formation of artifacts to the reconstructed image.  
           [0011]    It is another object of the present invention to provide a scanner for a medical optical imaging device that excludes ambient light from entering the scanning chamber.  
           [0012]    It is another object of the present invention to provide a scanner for a medical optical imaging device that suppresses reflections inside the optical cavity between the breast and the photodetector.  
           [0013]    In summary, the present invention provides a scanner for a medical optical imaging device, comprising an illumination source positioned to direct emitted light into a breast positioned below a support surface; a plurality of detectors positioned to detect light emerging from the breast; and a container disposed below the illumination source and the detectors adapted to trap light reflected from the breast.  
           [0014]    The present invention also provides a scanner for a medical optical imaging device, comprising an illumination source positioned to direct emitted light into a breast positioned below a support surface; a plurality of detectors positioned to detect light emerging from the breast; and a collimator having a plurality of holes associated with the respective plurality of detectors to restrict the field of view of the detectors. The holes include non-smooth inside surfaces.  
           [0015]    The present invention further provides a scanner for a medical optical imaging device, comprising a scanning chamber including an illumination source positioned to direct emitted light into a breast and a plurality of detectors positioned to detect light emerging from the breast. The scanning chamber includes inside surfaces coated with low-reflectivity material.  
           [0016]    The present invention further provides a scanner for a medical optical imaging device, comprising a scanning chamber including an illumination source positioned to direct emitted light into a breast and a plurality of detectors positioned to detect light emerging from the breast. The scanning chamber includes slanted vertical surfaces to direct light from a horizontal plane.  
           [0017]    These and other objects of the present invention will become apparent from the following detailed description. 
       
    
    
     BRIEF DESCRIPTIONS OF THE DRAWINGS  
       [0018]    [0018]FIG. 1 is a schematic side elevational view of a medical optical imaging device showing a patient positioned on a support with her breast pendent within a scanning chamber made in accordance with the present invention,.  
         [0019]    [0019]FIG. 2 is a schematic cross-sectional view of a container disposed below a scanner to capture reflected light from the breast during scanning.  
         [0020]    [0020]FIG. 3 is a top plan view taken along line  3 - 3  of FIG. 2, illustrating a honeycomb structure used as a light trap.  
         [0021]    [0021]FIG. 4 is an enlarged partial cross-sectional view of a side wall of the container shown in FIG. 2, showing the relationship between the slant angle and the plane of the data acquisition.  
         [0022]    [0022]FIG. 5 is a perspective view of a collimator made in accordance with the present invention, showing a plurality of openings to restrict the field of view of detectors.  
         [0023]    [0023]FIG. 6 is schematic plan view of the scanner, showing the relationship between the patient&#39;s breast, illumination beam, collimator, detector field of view, and the detector.  
         [0024]    [0024]FIG. 7 is an enlarged schematic cross-sectional view through line  7 - 7  of FIG. 5, showing a light trap for minimizing off-axis light from reaching the detector. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]    A medical optical imaging device is disclosed in U.S. Pat. Nos. 5,692,511, 6,100,520, 6,130,958, which are hereby incorporated by reference.  
         [0026]    Referring to FIG. 1, a patient  2  is positioned prone on a scanning table  4  with one breast  6  pendulant in a scanning chamber  8 . A medical optical imaging scanner  10  comprises a collimator  12  secured to an orbit plate  14  and an elevator plate  16 . The collimator  12  is associated with detectors  13  (see FIG. 5). The orbit plate  14  is orbited through one circle around the breast to obtain one slice of data. The elevator plate  16  is moved vertically by drive screws  18  to position the orbit plate  14  at different vertical locations where the orbit plate  14  is again orbited through one circle around the breast to obtain another slice of data. A side curtain  20  is fixed to the underside of the table  4  and the elevator plate  16  to form a barrier for ambient light for the scanning chamber  8  defined by the side curtain  20 , the orbit plate  14 , the elevator plate  16  and a hollow container  21 , such as a cylinder.  
         [0027]    The side curtain  20  is foldable vertically to allow it to expand and retract as the vertical plate  16  is lowered or raised. The side curtain  20  includes slanted vertical surfaces  23 . The side curtain  20  is advantageously made from low or nonreflective material.  
         [0028]    Referring to FIG. 2, the hollow cylinder  21  has a vertical wall having an inside surface formed into a series of non-vertical steps  22  adapted to direct internal reflections, generally indicated at  24 , downwardly towards the bottom and away from the collimator  12  and the detectors  13 . The reflections  24  originate from the scanning beam  40  impinging on the breast  6 . A bottom wall  26  of the hollow cylinder  21  is provided with a honeycomb structure  28  with openings  30  directed upwardly towards the breast. The honeycomb structure  28  advantageously traps any stray reflections within the hollow cylinder  21  and prevents the reflections from being directed back towards the breast and the collimator  12 .  
         [0029]    The steps  22  are preferably formed with horizontal portions  32  and inclined portions  34 , as best shown in FIG. 4. The steps  22  are configured to direct reflected light away from the scan plane, generally indicated by the scanning beam  40  shown in FIG. 2. The angle  35  between the portions  32  and  34  is configured to cause downward reflections of the stray light. The inside surfaces of the hollow cylinder, including the steps and the honeycomb structure, are painted with flat-black paint to make the surfaces low or non-reflective. The openings of the honeycomb structure  28  are preferably hexagonal, as shown in FIG. 3; however, circular, square, triangular, pentagonal or other geometric shapes would also work.  
         [0030]    Referring to FIG. 5, the collimator  12  comprises a series of holes  36  through a body  37  that arches around the breast  6 . Detectors  13  are positioned at the end of each hole  36  to detect light coming from the breast  6  due to the laser beam  40  impinging on the breast during scanning. The collimator  12  has a vertical surface  42  that faces the breast. The surface  42  is preferably slanted at about  15 ° off the vertical to direct any stray reflections downwardly toward the hollow cylinder  21  and away from other openings  36 . A lens  43  may be placed in front of each detector  13  to increase light collection capability.  
         [0031]    Within the scanning chamber  8 , any surfaces facing the breast is advantageously made low or nonreflective with flat black paint and are slanted from the vertical. In this manner, the chances of any stray reflection finding its way into the holes  36  of the collimator  12  are minimized.  
         [0032]    The collimator  12  is shown schematically in plan view in FIG. 6. Each opening  36  has a field of view, schematically indicated at  44  to restrict the amount and direction of light that can be detected by the detectors  13 .  
         [0033]    Referring to FIG. 7, a portion of the inside surface of each hole  36  is made non-smooth, such as by providing a series of grooves with slanted walls, or threading the opening with a fine pitch screw thread  46 , to significantly reduce the occurrence of off-axis light, generally indicated at  48 , from the reaching the detector  13  disposed at the other end of the hole. The side walls of the thread  46  change the reflection path of the light  48 , as generally indicated at  49 . The length of the openings  36  limits the field of view of the respective detector  13 . Off-axis light  48  is generally reflected light which is not useful. Through axis light  50 , which has passed through the breast, is used for image reconstruction.  
         [0034]    While this invention has been described as having preferred design, it is understood that it is capable of further modification, uses and/or adaptations following in general the principle of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains, and as may be applied to the essential features set forth, and fall within the scope of the invention or the limits of the appended claims.