Abstract:
A computer controlled apparatus for detecting breast tumors by mechanically palpating a breast in a full scan manner to detect small lumps or anomalies. The patient is positioned on a fully adjustable bed and oriented relative to the apparatus. A detection head mounted for movement in three dimensions is positioned above the bed. A palpation finger is brought into pressure contact with a sequence of small areas across the entire breast, palpating each area to measure tissue density. Concurrent with the palpation scan, a scan of breast color and temperature is conducted. A locator head positions the detector for the scan in a manner that assures repeatability during each of a series of periodic examinations. This system detects very small lumps and allows easy, accurate monitoring of suspicious areas over an extended time period. Several different embodiments of the detection head and location head are described.

Description:
RELATED APPLICATIONS 
     This application is a division of applicant&#39;s copending U.S. patent application Ser. No. 09/241,193, filed Feb. 1, 1999, entitled “Apparatus for Detecting Very Small Breast Anomalies”, which application is a continuation-in-part of U.S. patent application Ser. No. 08/957,648, filed Oct. 24, 1997, now U.S. Pat. No. 6,192,143, dated Feb. 20, 2001. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to apparatus and methods for detecting very small anomalous masses, in particular tumors, in the human breast. In particular, this invention relates to detection heads for physically detecting breast anomalies and generating an electrical signal corresponding to changes in breast characteristics due to such anomalies. 
     BACKGROUND OF THE INVENTION 
     Recent findings indicate that one of eight women will develop breast cancer, the second leading cause of cancer death in women. Unopposed estrogen activity is an important pathogenic factor, with other risk factors including nulliparity, early menarche, late menopause, a family history of breast cancer, middle age and prior breast cancer. 
     The earliest indication of breast cancer generally is the occurrence of a painless lump, sometimes associated with nipple discharge and skin retraction. Later symptoms are generally due to metastases to bone, brain, lungs and liver. Early diagnosis may be possible through monthly self-examinations. Mammography has proven beneficial in early detection. 
     When a very small lump, &lt;2 cm, is detected, a biopsy is generally performed, followed by treatment when the lump is found to be malignant. This can range from a lumpectomy with possible radiation treatment of axillary nodes to a modified radical mastectomy with axillary node dissection. With early treatment, the five-year survival rate is about 85%. Without early detection, if distant metastasis occur, the survival rate may drop to 10% or less. 
     Early detection of lumps is thus essential. Monthly self-examinations are very desirable, followed by examination by a physician if any suspicious areas are detected. It is, however, difficult for an unskilled person to detect very small lumps or to do a thorough examination. 
     Periodic palpation of the breasts by a physician and mammography will often detect very small tumors. These examinations should be reasonably frequent, particularly in older women, in order to detect tumors before they can metastasize. However the cost of frequent examinations, plus the accumulated radiation exposure from frequent mammograms tend to limit frequency. In addition, mammography may miss very small tumors, especially in the dense breasts of younger women. Further, pregnant women should avoid exposure to radiation. 
     Palpation of breasts will not detect very small changes and anomalies of the breast until the changes are so large or hard compared to the normal breast tissue that the difference can be detected by a touch of a finger. Generally, palpation is only capable of detecting changes where the anomalous tissue is relatively hard, has a diameter of at least about one centimeter and is close to the surface of the skin. Deeper anomalies, particular in large breasts, are difficult to detect by palpation. Since the characteristics of anomalies are not quantifiable, detecting changes in anomalies from one examination to another is difficult. 
     Thus, there is a continuing need for improved methods and apparatus for very early detection of very small breast anomalies that could be malignant, while avoiding radiation exposure. 
     SUMMARY OF THE INVENTION 
     The above-noted problems, and others, are overcome in accordance with this invention by an anomalies detection apparatus for thoroughly palpating entire breasts in a continuous, automatic scanning manner, to detect changes in breast tissue physical characteristics. In particular density is measured across the entire breast and, where anomalies are detected, mobility and size of the anomaly are measured. 
     The overall system of this detection apparatus includes a bed upon which the patient lies face up and which includes means for precisely positioning the patient in the same position for each of a series of periodic examinations. The detection head is mounted on a carriage for movement in three dimensions adjacent to a patient on the bed. A locator head associated with the detection head controls the bed positioning means to position the breasts in precisely the same position as for prior examinations. A palpation means on the detection head includes at least one finger-like palpation end movable toward and away from the breast surface to palpate the breast in the same general manner as a physician. The palpation device is preferably mounted so as to be movable across the entire breast surface sequentially while maintaining the finger generally perpendicular to the breast surface. 
     Information sensed by the palpation device is collected, stored and displayed in a conventional manner, such as is done with information from other systems such as computerized tomography and magnetic resonance imaging. The display will reveal, and show details of, any anomalies detected, so that further testing, such as through a biopsy, can be done. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     Details of the invention, and of preferred embodiments thereof, will be further understood upon reference to the drawings, wherein: 
     FIG. 1 is a schematic elevation view of an entire anomaly detection apparatus; 
     FIG. 2 is a schematic top plan view showing a patient positioned on the patient positioning bed; 
     FIG. 3 is a schematic elevation view of a detection head and actuator; 
     FIG. 4 is a schematic elevation view of a detection head and actuator positioning device; 
     FIG. 4 a  is a schematic representation of a laser transmitter and receiver reading a laser card within a laser reader of the anomaly detection apparatus; 
     FIG. 5 is a schematic diagram of a first embodiment of a locator head assembly; 
     FIG. 6 is a schematic elevation view of a vertical positioning mechanism of the anomaly detection apparatus of FIG. 1; 
     FIG. 7 is a schematic representation of the internal components of a first detection head embodiment; 
     FIG. 8 is a schematic representation of the internal components of a second detection head embodiment; 
     FIG. 9 is a schematic representation of the internal components of a third detection head embodiment; 
     FIG. 10 is a schematic representation of the internal components of a fourth detection head embodiment; 
     FIG. 11 is a schematic representation of a palpation tip for a detection head; 
     FIG. 12 is a schematic representation of a detection head having a plurality of parallel palpation tips; 
     FIG. 13 a  is a schematic representation of one embodiment of an encoder slide assembly for palpation tip position measurement for use with a single tip arrangement or a multi-tip arrangement as seen in FIG. 12; 
     FIG. 13 b  is a schematic representation of a second embodiment of the encoder slide assembly shown in FIG. 13 a;    
     FIG. 14 is a schematic elevation view of a second embodiment of the distal end of the carriage shown in FIG. 1; and 
     FIG. 15 is a schematic representation of the internal components of a second embodiment of a locator head assembly. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to FIG. 1 there is seen a carriage  10  mounted at a proximal end on a horizontal support  12  for movement therealong. A detection head  14  (as detailed in FIGS. 3 and 4) is mounted at the distal end of carriage  10 . A locator head  16  (detailed in FIG. 5) is also mounted to the carriage  10  for movement therewith. Digital information from and to detection head  14 , locator head  16  and control commands to various motors, limit switches and the like are passed between a computer center  17  as schematically indicated. Information is received, stored, interpreted and displayed in the same manner as other medical scanning devices, such as CAT scans, MRI scans, etc. Three dimensional images can be viewed on a conventional computer monitor. 
     If desired, images may be shown with different tissue density areas shown in different colors. Artificial intelligence techniques may be used to improve system performance. The combination of tissue density information as developed by palpation and the ancillary local color and temperature information results in detection of much smaller tumors and the ability to easily track changes in discrete tissue areas. 
     Horizontal support  12  is mounted on a vertical support mechanism  18  (as detailed in FIG. 6) along which support  12  can move in a vertical direction. Horizontal support includes a traveler  20  that rides in bearings  22  along rods or tubes  24  that are secured at their ends to end blocks  26  and  28 . A lead screw  30  extends from a bearing  32  at end block  26  to a drive motor  34  at end block  28 . Lead screw  30  extends through correspondingly threaded openings in walls  36  of traveler  20  so that traveler  20  will move to the right or left as the lead screw  30  is rotated in one direction or the other. Conventional limit switches  37  prevent over travel of traveler  20 . 
     Guide rods  38  extend vertically through end blocks  26  and  28  and a lead screw  40  extends vertically through end block  28 . These components are shown completely and discussed in conjunction with the discussion of FIG. 6, below. 
     Carriage  10  includes a base  42  secured to traveler  20 . A motor  44  within base  42  rotates a screw  46  that is threaded into an intermediate body  48  to raise and lower the intermediate body  48  as the screw  46  is rotated one way or the other. A pair of guide rods  50  extend through brackets  52  to guide movement of the intermediate body  48 . A lower body  54  is secured to intermediate body  48  for rotation relative thereto. A motor  56  is mounted on intermediate body  48  with lower body  54  mounted on the motor shaft  58  for rotation with the shaft. 
     An arm  61  is pivotally mounted at pivot  62  on bracket  64  mounted on the distal end of lower body  54 . A motor  60  on lower body  54  drives a pulley  63  on arm  61  through a jackshaft  65 . 
     Thus, the entire carriage  10  can be moved horizontally by horizontal support  12  and vertically by the vertical support  18  of FIG.  6 . Lower body  54  of the carriage  10  can be rotated through a full circle. Arm  61  carrying detection head  14  can be pivoted through at least 180°. This combination of movements permits the detection  14  head to be positioned in any desired position relative to any portion of a breast surface. 
     In order to perform a complete breast examination, a person lies face-up on a bed  67  mounted on a position adjusting assembly  69  as seen in FIG.  2 . The bed will be positioned generally below detection head  14  of FIG.  1 . 
     Bed  67  has a comfortably padded upper surface, with matrix boards  66  adjacent to the shoulders of person  68 . Conventional optical measuring means (not shown) can be provided to locate the exact position of arms, shoulders and neck relative to the matrix board  66  pattern during a first examination. Then, when the person  68  is again positioned on the bed  67  for a later examination, the optical system in conjunction with conventional software can again determine the person&#39;s position relative to matrix boards  66  and the position of the bed  67  can be adjusted in accordance with stored location information to place the person in substantially the identical position as for the first examination. Further, if person  68  were to move during the examination, the optical system can detect and correct for the change in position. It is highly desirable that the person  68  be positioned as identically as possible for each of the periodic examinations. 
     The underside of bed  67  includes conventional tubular bearings (not seen) through which horizontal guide rods  70  pass. A central threaded rod  72  engages end bearings  74  on assembly  69  and passes through a conventional motor driven nut assembly  76 . As the motor driven nut assembly  76  is rotated in one direction or the other, bed  67  will be correspondingly moved sideways. Similarly, a pair of guide rods  78  extend between end walls  80  of assembly  69 . Guide rods  70  and  78  are each arranged in a set of at least two parallel guide rods. A central threaded rod  82  passes through a conventional threaded block (not seen) secured to the underside of bed  67 . A motor  84  rotates threaded rod  82  to move the bed  67  in either lengthwise direction, as desired. The overhead end blocks  26  and  28  (FIG. 1) are mounted on posts  85 , the lower portions of which are seen in FIG.  2 . 
     The operating structure of detection head  14  is detailed in schematic elevation view in FIG. 3. A removable connection  86  for main housing  87  mounts detection head  14  on arm  61 . Preferably, detection head  14  is rotatable relative to arm  61  by a motor  88 . 
     A detector housing  90  for palpation finger  92  and sensor  94  for sensing distance, color and temperature is mounted on main housing  87  through arms  96  and  98 . Finger  92  is, designed to act like a physician&#39;s palpating finger in a manual breast examination. Typically, finger  92  will be formed from a sturdy, disposable material, such as glass. 
     Sensor  94  includes a distance measuring mechanism, of the sort used in cameras and the like, for providing precise distances between the breast surface and the sensor. If desired, a plurality of spaced range finders may be used to assure that palpation finger  92  is oriented perpendicular to the breast surface. 
     A conventional means for measuring the color of the breast surface being examined is included in sensor  94 . Typically, this can be a conventional prism for breaking up incoming light and refracting each color of light to an independent photo electric or photo resistive sensor. 
     Palpation finger  92  is secured to a distal end of a shaft  100  that is slidable through housing  90  and pivoted at its proximal end to a distal end of arm  102  at pivot point  104 . Arm  102  is rotatable about an axis  106  centrally located along arm  98 . The proximal end of arm  102  is pivotally connected to drive shaft  108  at pivot point  110 . When shaft  108  is moved axially by an actuator within actuator housing  112  (as detailed below in conjunction with the description of FIG. 4) shaft  100  and palpation finger  92  move a proportional distance in the opposite direction. As discussed below, a laser reader in reader housing  114  detects movement of shaft  108  and the feedback resistance to movement experienced by palpation finger  92  when pressing against breast tissue. 
     An error correction sensor  116  is provided on detector housing  90 , cooperating with a member  119  mounted on shaft  100  to detect and correct positioning errors. It is possible that moving components of the detection head  14  mechanism shown in FIG. 3 may not be positioned correctly any time after coils  118  (FIG. 4) have been activated and repositioned. Resetting the position of the moving components, e.g., detection head  90 , shaft  100 , arm  102 , and therefore palpation finger  92 , is accomplished by the first coil  118  at the left as seen in FIG.  4 . Slight changes in position of the breast skin, due to breathing or the like, is sensed by finger  92  and a corresponding position correction signal is sent to the leftmost coil  118  to correct for that displacement. While this precision is often not required, it is available if needed. 
     The internal components within actuator housing  112  and reader housing  114  are schematically illustrated in FIG. 4. A series of electromagnetic coils  118  are arranged in a uniformly spaced relationship along a central tube  120 . An end shaft  122  is axially secured to the proximal end of shaft  108  and extends into tube  120 . Shaft  108  slides in a sleeve  123 . 
     End shaft  122  is formed from a magnetic material so that when coils  118  are actuated sequentially, beginning with the coil adjacent to the end shaft  122  fastened to shaft  108 , the magnetic forces will tend to pull end shaft  122  into tube  120 . As shown in FIG. 3, this pulls shaft  108 , arm  102  and shaft  100  and pressing palpation finger  92  toward an adjacent breast. 
     The magnetic forces provide a rather “soft” pull so that breast tissue can stop the advance of palpation finger  92  without severe compression. The distance the finger advances will be in proportion to the density of the tissue, with a lump of more dense tissue resisting penetration, so the distance the finger advances will be less. This arrangement of arm  102 , shafts  100  and  108  with magnetic coils  118  could be thought of as a weighing scale where breast tissue density corresponds to the object to be weighed and the magnetic actuator is the standard portion of weight placed on the other side of the scale. 
     In operation, the first coil of coils  118  will be actuated, moving palpation finger  92  a predetermined distance. Typically the coil is powered up stepwise, at about 250 mv per step up to about 10 volts maximum. The pressure change per step is typically only about 10 grams per mm 2 per step. If tissue resistance is low, the second coil of coils  118 , and others in sequence, will be similarly actuated, further moving the finger  92 . Eventually, tissue resistance will reach a predetermined level and the distance traveled by the finger  92  will be measured, as detailed below, and the information transferred to conventional information storage means. 
     The mechanism for encoding and transmitting the palpation information to the storage and use station (computer center  17 ) is enclosed in reader housing  114 . As seen in FIG. 4, a conventional laser optic card  124 , using technology as applied in musical compact disks but with a single straight track, is carried by shaft  108 . A laser card reader  126  reads the shaft  108  position from the card  124  and transmits the encoded information to the information collection station. There, the information can be converted to machine language or any desired format for interpretation by conventional software systems of the sort used in CAT scan systems or other medical scanning systems. Any error or mechanical tilt is detected in real time by error correction sensor  116  that filters out any mechanical movement other than the desired palpation movement. 
     A typical laser card  127  of the sort used in reader  126  is schematically illustrated in FIG. 4 a.  Card  127  has a series of reflecting areas  129  separated by non-reflective areas  131 . While non-reflecting areas  131  could be light absorbing, generally it is preferred that they be transparent so the incident light will pass through. A laser transmitter  133  directs a laser beam  135  against the patterned area of laser card  127 . When the laser beam  135  hits a reflecting area  129 , reflected light is picked up by a receiver  137 . As card  127  is moved transversely, conventional software can count the pattern of reflected pulses to measure movement of shaft  108  and, ultimately, palpation finger  92 . The reflecting areas  129  can be as small as about 0.001 mm for highly precise movement measurement. 
     An adjustment mechanism  128 , such as a threaded adjustment shaft acting similar to a turnbuckle, is provided to adjust the position of shaft  108  relative to the array of electromagnetic coils  118 . The maximum excursion of shaft  108  is limited by pin  130  extending from shaft  108  and limit switches  132 . 
     The unit will thus sequentially test areas to provide a “picture” of the entire breast surface, revealing density changes indicative of tumors on a very fine scale, in a manner similar to the images produced in MRI, CAT and other physical scanning methods. 
     To provide the maximum consistency of results from one examination to the next, it is highly desirable that the person and the breasts be positioned as identically as possible for each examination. The movable bed arrangement shown in FIG. 2, in cooperation with the locator head  16  schematically illustrated in FIG. 5, provides accurate positioning by locating the position of a person  68  on the bed  67  and actuating the various carriage  10 , bed  67  and detection head  14  movement mechanisms under computer control to locate the breast to be examined in substantially the same position it was in at the last prior examination. 
     A digital camera  134  provides a digitized image of the breast and patient in a matrix manner to supply sufficient data for the ongoing examination session and the pre-positioning of the patient whenever a new image is required. A computer system can compare the original image to a subsequent image at the start of a subsequent examination so that the patient&#39;s position can be adjusted until the images match. 
     A white light source  136  is provided with a schematically illustrated focussing lens system including lens  138 , a lead screw  140  rotatable by motor  142  and threaded through a lens mount bracket  144  to focus a light spot on the breast surface. As the spot of light is moved transversely and focussed at different depths along the breast, the scan can be saved in computer memory in a conventional manner to produce a three-dimensional image of the breast. 
     In addition, a laser scanner  146 , including a laser emitter  148  and a focussing system  150  for producing a small spot on the breast being examined may be used in the same way as the white light spot to create a three-dimensional image. Typically, a 680-820 nm, 0.0095 mw laser may be used, since that laser has sufficient power for imaging without damaging the skin. 
     A window  152  of glass or plastic that is transparent to the white light and laser light closes the bottom of locator head  16 . A similar window  154  covers the side of head  16  adjacent to camera  134 . 
     The vertical support mechanism  18  for raising and lowering the entire carriage  10 , as seen in FIG. 1, is illustrated in FIG.  6 . Vertical guide rods  38  extend from a sturdy base  156  to a top plate  158 . End blocks  26  and  28  carry horizontal support  12  (FIG. 1, omitted from FIG. 6 for clarity) for vertical movement therealong. 
     A powerful motor  160  rotates the sturdy lead screw  40  threaded through block  28 . An upper limit switch  164  and a lower limit switch  166  prevent movement of horizontal support  12  beyond desired limits. For a very strong, sturdy assembly, base  156  will rest on the floor or a sub-floor so that bed assembly  67  could be positioned within a frame formed by base  156 , top plate  158  and vertical guide rods  38 . 
     The image produced by either of these light spots produced at a first examination can be compared to an initial image produced at a later examination to adjust the breast position to substantially match the original position. This will aid in re-examining a suspicious spot or lump found in the initial examination during later examinations. 
     The three-dimensional images can be divided into a matrix of cubes or slices with geometric indicia (e.g., a cube might be identified as cube  2 , 4 , 9  on an x-y-z axis basis) and location scan be directly compared between the light spot image and the finger palpation locations. 
     A second embodiment of internal components of a detection head for detecting changes in density, hardness, and the like in breast tissue in as elected very small area is schematically illustrated in FIG.  7 . 
     A permanent magnet  200  mounted on a non-magnetic rod  202  is movable along the axis of the rod  202  centerline. Suitable guides  204 , such as rollers, ball bearings, a sleeve or the like, allows smooth, low resistance, axial movement of rod  202 . Permanent magnet  200  faces an electromagnet head  206  mounted on a shaft  207  and fixed to housing  208 . Poles of permanent magnet  200  and electromagnet head  206  (when activated) have the same poles juxtaposed, here having north poles adjacent to each other as indicated, with the electromagnet south pole at  210 . Electromagnet head  206  is powered by any suitable number of powered coils  212 , connected at terminal  214  to a power source via wires  216 . 
     Since the magnets  200 ,  206  have the same poles opposite each other, the arrangement will tend to “push” the magnets apart as soon as electromagnet coils  212  are activated. The intensity of this “pushing” force can be varied in accordance with the number of turns in coil  212  and the power provided thereto. 
     A palpation tip  218  (i.e., palpation finger  92 ), as detailed in FIG. 11, is mounted on the distal end of rod  202 . Tip  218  is brought into contact with(or to a predetermined distance from) the breast surface by carriage  10  as described above. Coil  212  is energized to increase the field around shaft  207  to increase the field at electromagnet head  206  and force permanent magnet  200  further away from electromagnet head  206 , which moves tip  218  against the breast. The breast tissue is depressed at the point of contact, with tissue elasticity pressing tip  218  and non-magnetic rod  202  back toward coil  206  in accordance with tissue elasticity and hardness at the contact point. 
     Variations in this back pressure as represented by the extent to which the tip presses into the breast tissue are transmitted to the recording instrumentation by any suitable means for measuring the movement of tip  218 . Typically, the position of tip  218  may be measured by the mechanism shown in FIGS. 4 and 4 a,  as discussed above. Another embodiment of a tip  218  position measuring system is shown in FIG. 13, described below. 
     The resilient mounting of permanent magnet  200  resulting from the field between the two magnets  200 ,  206  will permit the permanent magnet  200 , should it strike a breast or other surface during positioning of detection head  14 , to provide sufficient “give” to prevent injury or damage to the breast or other surface. 
     Another embodiment of internal components of the detection head is illustrated in FIG. 8. A permanent magnet  222  is mounted on the proximal end of an actuator rod  224  which is slidable along a sleeve  226  mounted on housing  228 . Atip  218  of the sort detailed in FIG. 11 is secured to the distal end of rod  224 . 
     A second permanent magnet  230  is mounted on a holder  231  coaxial with rod  224 . Same poles (north to north or south to south) on each of magnets  222  and  230  face and repel each other. Holder  231  is supported on a disk  232  slidable within housing  234  coaxial with rod  224 . A sleeve  236  is preferably mounted on holder  231  to aid in guiding movement of rod  224 . 
     Detection head  14  is moved as discussed above to bring palpation tip  218  into proximity with a selected location along the breast surface. When tip  218  is initially brought into proximity to the breast surface, rod  224  will hang down and the force of gravity will cause the rod to move to a point where the gap between magnets  222  and  230  will increase. 
     A motor  238  mounted in housing  234  drives a lead screw  240  which is threaded through a corresponding female thread  241  in disk  232 . Motor  238  may be any suitable motor, such as a low rpm DC motor or a stepper motor. Rotation of lead screw  240  will move magnet  230  toward magnet  222  decreasing the intermagnet gap until breast resistance to penetration of tip  218  will return the intermagnet gap to a predetermined distance. The distance that holder  231  and disk  232  move is representative of breast density characteristics at the contact point. A conventional sensor  242  counts the revolutions of motor  238  to measure the corresponding degree of penetration of tip  218  into the breast. 
     Conventional safety sensors  244  may be provided to limit maximum movement of disk  232  (and movement of tip  218  in accordance with disk position) to prevent damage to the breast. As mentioned above, the magnetic field between magnets  222  and  230  will act as a resilient mount for tip  218 , limiting damage or injury should the tip strike a breast or other surface. 
     FIG. 9 is a schematic diagram of another embodiment of detection head  14 . Here, housings  228  and  234 , actuator rod  224 , sleeves  226  and  236 , tip  218 , holder  231 , disk  232 , motor  238  and sensors  242  and  244  are the same as shown in FIG.  8  and discussed above. 
     Instead of the spaced permanent magnets  222  and  230  used in the FIG. 8 embodiment, a spring  248  is fastened between the proximal end of rod  224  and holder  231 . Spring  248  is selected to bias the two juxtaposed ends to a particular, predetermined spacing. As discussed in conjunction with FIG. 8, above, when the detection head  14  is positioned over a breast, tip  218  extends downwardly under the force of gravity. Motor  238  rotates to move disk  232  and holder  231  toward rod  224  until the gap between the distal end of holder  231  and the proximal end of rod  224  is at the original predetermined distance. The total movement of holder  231  is indicated by the number of revolutions of lead screw  240  as measured by counting sensor  242 , which is indicative of breast tissue physical parameters. 
     Another embodiment of a detection head  14  is schematically illustrated in FIG.  10 . Most components are the same as in the embodiments of FIGS. 8 and 9. However, here in place of a magnetic field or spring between the proximal end of rod  224  and the distal end of holder  231 , a gas  250  is enclosed within sleeve  236  at the proximal end of rod  224 . Sleeve  236  fits over rod  224  in a sealing arrangement to prevent pressurized gas  250  from escaping. Any suitable conventional seals may be used between rod  224  and sleeve  236 . 
     Any axial physical force applied to rod  224  will change the gas pressure within sleeve  236  which will be measured by a conventional pressure sensor  252  capable of providing an electronic read-out. As before, when the tip  218  is aligned downwardly in contact with breast tissue, the pressure sensed will be lower. Lead screw  240  will be rotated by motor  238  to move holder  231  toward sleeve  236  to slide the sleeve  236  over rod  224 , decreasing the volume and increasing pressure. The number of motor rotations, as counted by sensor  242 , required to bring pressure up to a predetermined level is indicative of breast physical parameters, such as hardness and density. 
     A preferred palpation tip  218  configuration is schematically illustrated in FIG.  11 . Tip  218  includes a rounded endpiece  254  which touches the breast surface. Any suitable material may be used, which should be disposable or washable. An end isolator  256 , made up of a soft electrically insulating material prevents any static electricity discharge from the body from affecting the readings. A core member  258  connects endpiece  254  to base  260  which is secured in any suitable manner, such as threads, to rod  224 . Side isolator  261  is generally tubular and is mounted on base  260  and spaced from core  258  to absorb any side impacts or sudden shakes. 
     FIG. 12 schematically illustrates a detection head  14  embodiment in which a plurality of tips  218  can be used in a closely spaced parallel array. Here, a plurality of tips  218 , typically of the sort shown in FIG. 11, are mounted on actuator rods  262 , typically rods similar to rods  224  described above, mounted for axial movement. Extension connectors  264 , which may be rigid offset members of the sort schematically shown, inflexible cables, or the like, which are capable of transmitting motion from systems  266  of the sort shown in FIGS. 7-10, are connected between the output ends of rods  224  of those systems and tip  218  actuator rods. 
     An encoder slide is preferably included in each extension connector  264  to provide highly accurate readout of movement of each tip  218  during breast palpation. A preferred encoder slide assembly  268  is detailed in the schematic illustration of FIG.  13 . Such an encoder slide assembly  268  may be used with any of the single tip arrangements of FIGS. 7-10. 
     As seen in FIG. 13, a preferred encoder slide assembly  268  includes an encoder slide  270  secured to rod  224 , as schematically shown, for movement with that rod. Encoder slide  270  could be secured to any suitable part of rod  224  or to tip  218 , as desired. Encoder slide  270  is transparent and includes a strip  272  bearing reflective dots  274  (or, in the alternative transparent dots in an otherwise opaque strip  272 ). 
     Decoder sensors  276  are provided on opposite sides of encoder slide  270 , mounted on a housing  278  secured to housing  228  by any suitable mounting means. Decoder sensors  276  are optical or laser sensors and light emitters of the sort used with conventional music or computer compact disks. 
     Where dots  274  are reflective against a transparent background, light will pass from a light transmitting decoder sensor  276  to the other, which is a light detector. As encoder slide  270  moves, light will be reflected away when a reflective dot is present between the decoder sensors and will pass to the detector when a space between dots is present in the optical path. Thus, changes between receiving and not receiving light at the second decoder sensor will indicate movement of the slide and the number of pulses of light received during encoder slide  270  movement will indicate distance of movement of rod  224  and tip  218 . 
     Where dots  274  are transparent against an opaque background, light pulses received at the detector decoder sensor  276  will indicate movement and distance of movement. 
     In the embodiment shown in FIG. 1, the optical locator head  16  is mounted separately from the arm  61  carrying the detection head  14  carrying the palpation finger  92  and sensor  94 . FIG. 14 illustrates an alternate embodiment in which the optical locating head  16  and detection head  14  are both mounted at the end of the arm  61  on carriage  10 . 
     Optical locator head  16  in the FIG. 15 embodiment includes a motor housing  282  secured by any conventional means, such as bolts (not seen) to detection head  16 . A lens enclosure  284  is secured to motor housing  282  after precise positioning during manufacture of the assembly. A lens assembly  286  is slidably mounted within lens enclosure  284  for axial movement relative thereto. 
     A motor  288  is mounted within motor housing  282  and drives a lead screw  290  which is threaded through a nut  292  secured to lens assembly  286  to move the lens assembly  286  axially within lens enclosure  284 . 
     Two laser beam positioning enclosures  294  are mounted on opposite sides of motor housing  282 . Each enclosure  294  contains a pre-focussed conventional visible light (typically 680 to 850 nanometer) laser diode and light sensor unit  296 . A prism  297  refracts light from the laser diode in unit  296  toward the breast being examined, typically along schematically indicated light beams  298 . Light reflected from the breast surface passes back through prism  297  to the sensor in unit  296 . This diode and sensor unit  296  operates in the same manner as conventional compact disk readers. The sensed returned light will be maximum when the beam from the beam generated by unit  296  is 90° to the breast surface. The mechanism described above for moving palpation tip  218  in three dimensions can thus adjust tip orientation to provide palpation at 90° to the breast surface. Two enclosures  294  with the components described above are preferably provided, with the first used to palpate one breast and the second used to palpate the second breast, since the size and shape of the two breasts are often somewhat different. 
     A motor  300  in each of the laser beam positioning enclosures  294  drives a lead screw  302  that engages an arcuate gear sector  304  to rotate each unit  296  and prism  297  about a center of rotation of the gear sector  304 . Prism  297  preferably refracts light from the diode in unit  296  at 90°. The laser diode within unit  296  generates a laser beam that produces a red dot on the breast being examined. A conventional sensor  306  within each enclosure  294  counts rotation of lead screw  302  and is calibrated to indicate the exact distance to the surface upon which the dot appears when the beam is 90° to the surface. The system computer then can conventionally calculate a three dimensional image of the breast surface from a number of these angle readings. 
     Lens assembly  286 , in conjunction with a light sensor  308 , a pre-focussed sensor lens  310  and lenses  312  operate in the same manner as conventional camera automatic focussing systems to bring the breast surface into sharp optical focus by rotating lead screw  290  as necessary. A position sensor  313  counts rotation of lead screw  290  to provide information to the central computer as to the position of focus. Since optical locator head  16  moves in conjunction with detection head  14 , when locator head  16  is moved to focus on the breast surface, palpation tip  218  will be brought into the predetermined contact with the breast tissue. 
     Extreme position sensors  314  are preferably provided to sense movement of lens enclosure  284  to the ends of its desired range of movement and prevent damage which might be caused by movement outside the selected range. Sensors  314  may be any conventional sensors, such as pressure switches, which can turnoff motor  288 . 
     In operation, either of the locator head  16  embodiments as shown in FIGS. 5 or  15  can be conventionally programmed to map an entire breast step by step. The horizontal and vertical (X and Y) movement of the carriage  10  takes locator head  16  to all of the selected points across the breast. The focussing mechanism within motor housing  282  and lens enclosure  284  will continually focus sensor  308  to provide the necessary Z direction alignment. The position sensor  313  will count the revolution of motor  288  while the motor is bringing lens assembly  286  to the point of focus to continuously provide lens position information. 
     Once locator head  16  has visited all desired points on the breast and has calculated its distance from every visited point, the computer can provide a conventional drawing in three dimensions of the entire breast. During palpation of the breast, location head  16  verifies the address being palpitated. Also, location head  16  will automatically compensate for breast movement as the patient breathes. If desired, a video camera  316  may be mounted on locator head  16 , as seen in FIG. 14, to provide a general view of the breast during palpation. 
     Thus, the apparatus of this invention will provide an accurate map of the breast, will detect tissue density anomalies and will accurately re-examine the breast from time to time to monitor any changes in breast density anomalies. 
     While certain specific relationships, materials and other parameters have been detailed in the above description of preferred embodiments, those can be varied, where suitable, with similar results. Other applications, variations and ramifications of the present invention will occur to those skilled in the art upon reading the present disclosure. Those are intended to be included within the scope of this invention as defined in the appended claims.