Patent Application
20100051808
The present invention is generally directed to imaging subsurface structures using infrared light. More particularly, the invention is directed to a system for illuminating an object with infrared light, recording reflected infrared light, and then re-projecting the intensity of the recorded infrared light in the visible range.
Some medical procedures and treatments require a medical practitioner to locate a blood vessel in a patient's arm or other appendage. This can be a difficult task. especially when the blood vessel lies under significant deposits of subcutaneous fat. Previous imaging systems include the system described in U.S. Pat. No. 7,239,909 (hereby specifically incorporated by reference in its entirety) entitled Imaging System Using Diffuse Infrared Light. In that system diffuse infrared light is used to image vasculature below the surface of the skin and then reproject that image onto the skin to reveal the location of the vasculature. It was previously believed that illumination with diffuse infrared light was required for good imaging of vasculature underlying the skin. For that reason, it was believed that a vascular imaging system using a laser or array of lasers as the light source would not work due to the fact that a laser's light is very focused, essentially the opposite of diffuse. The inventor has discovered, however, that a laser or array of lasers producing substantially uniform infrared irradiation will also work. Irradiation would be considered substantially uniform, for the purposes of imaging vasculature, if the high spatial frequency variability is less than ±0.5%. A laser provides uniform irradiation in the very small area upon which it shines. By scanning a laser or an array of lasers, an image of the underlying vasculature can be recorded and projected on a pixel by pixel basis. If the intensity of the laser or each laser in an array of lasers is constant to ±0.5% or if the emitted intensity of the laser or each laser in an array of lasers is measured to allow correction for intensity variations then the average illumination by the scanning laser source would be uniform enough. By scanning the laser beam or beams, an image of a useful size can be generated.
The results of this discovery is an apparatus using one or more lasers to provide infrared light towards an object, such as a patient, to enhance visibility of subcutaneous blood vessels. In one embodiment, the apparatus includes a first irradiating laser array for illuminating the body tissue with infrared light having a first wavelength in the range at which vasculature becomes apparent. Light which is reflected from the object is recorded by a first light sensing device for receiving light of the first wavelength. The first light sensing device then produces a first output representing the intensity of the recorded light. A first projecting laser array then projects a visible light representation of the first output onto the surface of the object.
In another embodiment, the apparatus includes a first irradiating laser array for illuminating the body tissue with infrared light having a first wavelength in the range at which vasculature becomes apparent, and a second irradiating laser array for illuminating the body tissue with infrared light having a second wavelength in the range of 1100 to 1700 nanometers. Light in those two wavelength ranges which is reflected from the object is then recorded by a first light sensing device which receives light of the first wavelength reflected from the object and a second light sensing device which receives light of the second wavelength reflected from the object. The first light sensing device creates a first output, and the second light sensing device creates a second output, each output representing the intensity of the light sensed by its respective light sensing device. The two outputs are then sent to an output comparer capable of comparing the first output and the second output to generate a compared output. Finally, a first projecting laser array projects a visible light representation of the compared output onto the surface of the object.
Using the invention described herein, subcutaneous blood vessels that are difficult or impossible to see under white light can be easily seen on the surface of the skin, enabling medical procedures such as the drawing of blood and i.v. placements, where the location of vasculature is important.
Further advantages of the invention will become apparent by reference to the detailed description of preferred embodiments when considered in conjunction with the drawings, which are not to scale, wherein like reference characters designate like or similar elements to the several drawings as follows:
There is a range of infrared irradiation of the body in which skin and other body tissues reflect light but blood absorbs light. For example, infrared light in the range of about 700 to about 1100 nanometers is known to be reflected by the skin and absorbed by the blood. Thus, in video images of body tissue taken under infrared illumination in this range, blood vessels appear as dark lines against the lighter background of the surrounding flesh. The inventor has determined that when an area of body tissue is imaged in this infrared range under substantially uniform infrared illumination, vasculature becomes apparent. Shown in
The imaging system (12) includes a first irradiating laser array (1) having a first wavelength in the range at which vasculature becomes apparent, a dichroic mirror (2) which transmits light in the infrared and reflects light in the visible, a polarizing filter (3), a polarizing beam splitter (4), a scanner (5), a polarizing filter (7), a lens (8), a narrow band filter (a) which transmits light of the wave length at which first irradiating laser array (1) is working, a first light sensing device (10) and a first projecting laser array (11). In one embodiment, the wavelength of the first irradiating laser array (1) is in the range of about 700 to 1100 nanometers, although this range is not the exclusive range at which first irradiating laser array (1) can operate for the invention to work. Vasculature can become apparent slightly above or slightly below this range as well. In the embodiment displayed in
Another embodiment of the invention, depicted in
The embodiment depicted in
Light which is reflected from the object (6) then reflects back to the scanner (5) and through polarizing beam splitter (4). It then passes through polarizing filter (7) which transmits light of a polarization different from polarizing filter (3) and preferably of an orthogonal polarization thereto. The light then passes through a lens (8) and, optionally, a long wavelength pass filter (23). The light passing through the long wavelength pass filter (23) then passes in one embodiment through a microscope objective (24) to a dichroic mirror (25) which transmits light in the range at which first irradiating laser array (1) is emitting and reflects light in the range at which second irradiating laser array (21) is emitting. The light transmitted by dichroic mirror (25) passes through a narrow band filter (9) which allows light to pass through which is in the range at which first irradiating laser array (1) is transmitting. The light passing through narrow band filter (9) then passes by an optical stop (26) to first light sensing device (10) which measures the intensity of the received light. The light which is reflected from dichroic mirror (25) passes through narrow band filter (27) which transmits light of the wavelength at which second irradiating laser array (21) is emitting. That light passing through narrow band filter (27) then passes by optical stop (28), through focusing lens (29) to second light sensing device (30) which records the intensity of the received light. In this embodiment, the second light sensing device (300 can be a photodiode or any other light sensing device which can measure the intensity of the received light. Each of the optical stops (26) and (28) can be a small object, a spatial light modulator such as a DLP chip, an LCOS chip, or a transmissive LCD chip, or any other optical stop which can achieve a similar result of blocking a portion of the transmitted light. If a optical stop (26) or (28) is a small object, such as a wire or a very small inscribed or printed dot, the microscope objective (24) magnifies the received light such that the optical stop eliminates only the center of the beam of received light, and, due to the typically small size of photodiodes operating in the 1100 to 1700 nanometer range, the focusing lens (29) focuses the light onto the second light sensing device (30) to ensure that enough light is gathered. If both optical stops (26) and (28) are digital micromirror devices, such as the DLP made by Texas Instruments, or a LCOS chip or transmissive LCD chip, then the microscope objective (24) and focusing lens (29) may be eliminated. In this embodiment, the first light sensing device (10) can optionally be a silicon photodiode, and the second light sensing device (30) can be an indium-gallium-arsenide photodiode.
The first light sensing device (10) and second light sensing device (30) each emit a respective first output and second output (not shown) representing the intensity of the light which they have received. These first output and second output are compared by the output comparer (not shown) in the method described in published patent application US 2007-0158569 A1 published on Jul. 12, 2007, entitled Method and Apparatus for Projection of Subsurface Structure onto an Object's Surface (hereby incorporated by reference in its entirety) at paragraphs [0670] to [0690] to create a compared output. The output comparer (not shown) may be analog electronics, digital electronics, a computer, or any other device capable of comparing the outputs in the disclosed way. This comparison may be done digitally or otherwise.
The output comparer (not shown) sends the compared output to control first projecting laser array (11) which emits light in the visible range. The light emitted by first projecting laser array (11) reflects from dichroic mirror (2) to pass through polarizing filter (3), reflect from polarizing beam splitter (4), reflect from scanner (5) and shine on the object (6). If the mirrors of scanner (5) are not still in the same position by this point, the light may be skewed between polarizing beam splitter (4) and scanner (5) to align the light such that it arrives at the proper spot on the object.
As for the use of a spatial light modulator such as a DLP chip, a LCOS chip, or a transmissive LCD chip as an optical stop (26) or (28), it provides multiple advantages. First, such devices allow for blocking of tiny portions of the light beam without first magnifying the beam and may be adjusted to block a larger or smaller amount of the beam. In addition, at least with the use of a DLP chip, light which is not transmitted is not lost. When a DLP chip or similar chip is used, it is possible to add one or more additional light sensing devices (not shown) to collect diverted light to use in image generation. Of course, the ray traces of light in
It should be understood that features of any of these embodiments may be used with another in a way that will now be understood in view of the foregoing disclosure. For example, any embodiment could work with or without optical stops.
Although the present invention has been described and illustrated with respect to at least one preferred embodiment and uses therefore, it is not to be so limited since modifications and changes can be made therein which are within the full intended scope of the invention.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US08/80425 | 10/20/2008 | WO | 00 | 11/4/2009 |
| Number | Date | Country | |
|---|---|---|---|
| 60981282 | Oct 2007 | US |
