Abstract:
An imaging system for locating subcutaneous blood vessels and a method for locating subcutaneous blood vessels using the system. The system includes at least one infrared emitter an infrared detector, a computing unit that enhances images and outputs enhanced images in substantially real time, a display device for displaying enhanced images, and a power source. The method includes the steps of preparing a body target area, putting on the headset, powering up the system, locating a target blood vessel, inserting a needle into the target blood vessel, and performing the medical procedure.

Description:
CLAIM OF PRIORITY 
   This application is a Continuation-in-Part of U.S. patent application Ser. No. 10/760,051, filed Jan. 16, 2004 now abandoned. 

   FIELD OF THE INVENTION 
   The present invention relates generally to the non-invasive viewing of surface and subsurface blood vessels by use of an infrared imaging. In particular, the present invention relates to an imaging system for viewing and accessing subcutaneous blood vessels and a method of use thereof. 
   BACKGROUND OF THE INVENTION 
   Intravenous (IV) access is the single most frequently performed invasive medical procedure in the world today. Though IV is generally considered routine, there are a number of situations in which inhibited IV access can be painful, traumatic, or even dangerous to patients. These include conditions in which subcutaneous blood vessels are difficult to locate because of patient characteristics or environmental conditions. For example, in battlefield conditions, where lighting is limited, it may be difficult, if not impossible, to locate subsurface blood vessels for injection. Easy IV access is especially critical in emergency situations in which a patient&#39;s life may depend on immediate IV access and “first-stick” accuracy. 
   Medical practitioners often encounter difficulty in gaining IV access in a significant portion of the patient population for which subsurface blood vessels are obscured. Such patients include obese patients, darkly pigmented patients, neonates (infants from birth to four weeks of age), children under four years of age, patients experiencing lowered blood pressure, patients who have collapsed veins, and patients requiring IV access in a minor or obscured blood vessel. Difficulties arising in these populations are demonstrated by the numbers: first-stick success rates in children and infants are currently 30%, which indicates that for 70% of the time, IV access in these populations requires more than one stick attempt. In neonates, more than 90% of IV catheters must be removed prematurely, mainly because of the improper placement of the catheters. Difficulties with IV access are encountered not only in locating the subsurface blood vessels, but also in complications that arise from improper insertion of needles or catheters in target blood vessels. Such complications include infiltration, thrombophlebitis, and infection of the IV access site. 
   It should be noted that children who have obscured blood vessels might lie in operating rooms for longer than 30 minutes, while medical practitioners attempt to find a blood vessel suitable for successful IV access. With the cost of operating room time approximately $14,000 per hour, delayed IV access can significantly increase the expense of both operating and office-based medical procedures. 
   IV access is especially critical in emergency situations when first stick accuracy can be life saving. A loss of time or inability to obtain IV access can mean the difference between life and death or, at a minimum, cause significant physical and psychological trauma. Further complicating matters, loss of patient blood and blood pressure in trauma situations can make locating subsurface blood vessels extremely difficult. 
   In cases where catheters, cannulas, and/or IV drips are used in patient treatment, these devices typically remain in a patient&#39;s blood vessel for a long period of time. However, in order to prevent infection, the devices are generally relocated to new body areas every 48 to 72 hours. Constant relocation of these devices over a long-term hospital stay may result in a need for medical practitioners to access less-optimal blood vessels, after more prominent blood vessels have been used. Often, these less prominent blood vessels can not easily be found by visual and tactile clues, and accessing them may require multiple sticks to the patient, which thereby causes the patient physical and emotional pain and trauma. Inhibited IV access can also subject medical practitioners to legal liability risk, by contributing to the complications associated with improper, ineffective, or delayed IV access. 
   IV location and access is both a visual and a tactile process. Traditional methods of IV location and access rely on the medical practitioner using his/her eyes and both hands to clean the target area, apply a tourniquet, locate the blood vessel by palpating the target area, and apply the hypodermic needle. For the sake of safe and efficient patient treatment, it is critical that the hands and eyes of the medical practitioner gaining IV access not be hindered in any way. 
   Medical practitioners gain proficiency at IV location and access through a process of learning and continued practice. To ensure a high standard of healthcare and patient safety, it is imperative that medical practitioners do not attempt to gain IV access before they are adequately trained. Unfortunately, traditional methods of IV location and access may require years of trial-and-error practice and thereby delay critical healthcare, which increases healthcare costs and possibly jeopardizes patient health. Any advancement in healthcare practices that reduces the amount of training time required for proficiency in gaining skill at IV access could contribute significantly to improved patient care. 
   In order to provide the highest standard of care while reducing the cost of healthcare, it is imperative that medical practitioners locate and gain access to subsurface blood vessels in a rapid and accurate manner. Simplified IV location and access can help to save lives in emergency situations, avoid the trauma of multiple sticks in situations in which patients&#39; vessels are difficult to locate, reduce the number of complications that stem from improperly inserted hypodermic needles and IVs, and reduce costs of medical procedures, by speeding up a critical bottleneck in many medical procedures: IV access. Therefore, what is needed is a hands-free device that allows medical practitioners to rapidly and accurately locate subsurface blood vessels for IV access. 
   As of late, apparatus have developed that help medical personnel more accurately locate blood vessels. For example a system and method for locating subcutaneous blood vessels via IR enhancement is described in U.S. Pat. No. 4,817,622, entitled, “Infrared imager for viewing subcutaneous location of vascular structures and method of use,” in which a human appendage, typically the inside of the elbow, is illuminated with an IR source, for example, at least one incandescent light bulb. A video camera for producing a video image and immediately overlying monitor for displaying the video image is utilized to look at the flesh. The camera is sensitive to IR radiation. A video display in which IR absorbing or scattering contrasting portions of the flesh are highlighted, for example, hard-to-find veins for inserting needles. A contrast enhancing circuit is included, which discloses amplifying the video information with high contrast enhancement of the video. Adaptation of the disclosed circuit to conventional TV charge coupled device cameras and monitors is illustrated with compensation of horizontal sweep to even image background, intensity averaging line-to-line for vertical image uniformity, and display of image contrasts, in a log amplification format. While the &#39;622 patent describes an IR blood vessel viewer, the &#39;622 patent utilizes an analog signal processor, which is not adequate for supporting the digital algorithms needed for true image enhancement and visualization. 
   More recently, U.S. Pat. No. 5,519,208, purports to describes a method and apparatus for gaining intravenous access that includes a source of radiation for irradiating an area of the patient with radiation having a wavelength that is absorbed in areas containing veins and reflected in all other areas. The reflected radiation is then read and the output displayed. Using this technique, venous structures appear as dark lines on the display, enabling a user to position the tip of a hypodermic needle at an appropriate location for drawing blood. 
   Along similar lines, U.S. Pat. No. 6,032,070, purports to describe a system and method to view an anatomical structure such as a blood vessel in high contrast with its surrounding tissue. The system and method may be used to produce an image of an anatomical structure using reflected electromagnetic radiation singularly scattered from target tissue. The system and method purport to provide improved contrast between any anatomical structure and its surrounding tissue for use in any imaging system. 
   Likewise, U.S. Pat. No. 6,230,046, purportedly discloses a system and method for enhancing visualization of veins, arteries or other subcutaneous natural or foreign structures of the body and for facilitating intravenous insertion or extraction of fluids, medication or the like in the administration of medical treatment to human or animal subjects. The system and method include a light source for illuminating or transilluminating the corresponding portion of the body with light of a selected wavelengths and a low-level light detector such as night vision goggles, a photomultiplier tube, photodiode or charge coupled device for generating an image of the illuminated body portion, and optical filter(s) of selected spectral transmittance which can be located at the light source(s), detector, or both. 
   The above referenced patents are illustrative of attempts to demarcate blood vessels from surrounding tissue. The systems and methods of the described patents are non-invasive and, most importantly, provide the near “real time” visualization of the image necessary for these devices to serve their practical purpose. However, because of the need to provide near “real time” images, these devices primarily depend on raw images, or images marginally enhanced by traditional analog means, which are of relatively poor quality for venepuncture accuracy. Therefore, there is a need not only for a device for visualizing subsurface blood vessels, but also a system and method for vascular image location, image enhancement, and hands-free manipulation, for quick and accurate IV access. 
   Therefore, there is a need for an improved system and method for locating and accessing a target blood vessel that that has the vein enhancing features of the prior art devices discussed above, but produces high quality images in near “real time” such that the system may be used by medical personnel during venepuncture, that allows target blood vessels to be more accurately and rapidly located than is possible using current systems and methods, that allows target blood vessels to be more easily located in difficult conditions and body types (e.g., obese patients, dark pigmentation skin, neonates, collapsed veins, low lighting), that reduces patient pain and trauma, both emotionally and physically; and that allows minimally trained medical staff to provide IV access. 
   SUMMARY OF THE INVENTION 
   The present invention is an imaging system for locating subcutaneous blood vessels and a method for locating subcutaneous blood vessels using the system. In its most basic form, the system includes at least one infrared emitter an infrared detector, a computing unit, a display device, and a power source. 
   The infrared emitter is, or emitters are, configured to illuminate a region under a surface of skin with waves of infrared light. The infrared detector, preferably a CMOS camera, is configured to accept waves of infrared light reflected from the region under the surface of the skin and includes an output for outputting a signal corresponding to unenhanced image data. The computing unit includes an input for accepting the unenhanced image data, a memory, means for enhancing and outputting result images in which enhanced images of blood vessels are shown within the images of the region under the surface of the skin, and an output for outputting the enhanced images in substantially real time. The display device inputs the enhanced images from output of the computing unit and displays the enhanced images. Finally, the power source is in electrical communication with the infrared emitter, the infrared detector, the computing-unit and the display device and provides power thereto. 
   In the preferred embodiment of the system, the means for enhancing and outputting result images includes a digital signal processing unit programmed with computer program means for enhancing and outputting result images at a rate of at least five frames per second. The preferred computer program means includes program means for Gaussian blurring a raw image with a kernel radius of 15, program means for adding an inverse Gaussian-blurred image to the raw image, and program means for level adjusting a result image to use an entire dynamic range. 
   The preferred system includes a headset to which the two arrays of infrared emitters, infrared detector, computing unit, display, and power source are attached. The headset preferably includes a pair of extension arms extending therefrom and a mounting surface pivotally attached to the pair of extension arms. In this arrangement, the two arrays of light emitting diodes and the infrared detector are attached to the mounting surface. The display is preferably disposed upon the headset such that a user is able to view both the display and the surface of the skin without removing the headset. 
   The preferred light emitting diodes are surface mounted light emitting diodes comprising integral micro reflectors. At least one light shaping diffuser is preferably disposed between the arrays of surface mounted light emitting diodes and the surface of the skin. Such a diffuser is preferably-integral to the light emitting diodes, but may be a separate diffuser. At least one first polarizing filter is preferably disposed between the surface mounted light emitting diodes and the surface of the skin, and at least one second polarizing filter is preferably disposed between the surface of the skin and the infrared detector. The polarizing filters preferably act to cross polarize the light, but may provide any arrangement of polarization, or be eliminated completely. 
   The infrared detector is preferably a CMOS camera adapted to generate digital data corresponding to the waves of infrared light reflected from the subcutaneous blood vessels located in the region under the surface of the skin. The CMOS camera may include a high band pass filter adapted to filter out substantially all light outside of an infrared spectrum, or may be adapted to receive both infrared and visible spectrum light. A camera lens is preferably disposed between the surface of the skin and the CMOS camera in order to adjust the focal length of the image. However, in embodiments in which a specialized CMOS camera having the proper focal length is used, or those in which the images are digitally adjusted for proper visualization on the display unit, the camera lens is eliminated altogether. 
   The preferred display is an LCD screen type display having a pair of LCD screens. At least one optical lens is preferably disposed between the LCD screens and a pair of eyes of a user to adjust for differences between the enhanced image an the unenhanced image viewed directly the user. However, in embodiments in which a in which a specialized display, having the proper focal length is used, or those in which the images are digitally adjusted for proper visualization on the display unit, the optical lens is eliminated altogether. 
   Finally, the preferred computing unit includes a digital signal processing unit and image data storage means for storing a multiple images for future viewing. The preferred computing unit also includes an interface for inputting data from a data input and and outputting data to a data output device. 
   In its most basic form, the method of using an imaging system to aid in an insertion of a hypodermic needle into a blood vessel during a performance of a medical procedure includes steps of preparing a body target area, putting on the headset, powering up the system, locating a target blood vessel, inserting a hypodermic needle into the target blood vessel, and performing the medical procedure. 
   In the preferred method, the infrared detector of the system is a camera and the step of locating a target blood vessel includes the steps of directing incident light from the infrared emitters on the target area of the surface of the skin, and viewing the target area on the display. In embodiments in which the system includes an optical lens, the step of locating a target blood vessel may include the steps of viewing the image of the target area of the skin as displayed on the display, viewing the unenhanced image on the target area of the skin and adjusting the optical lens to correct the enhanced image displayed on display for depth perception differences between the enhanced image and the unenhanced image. In still other embodiments, the step of locating a target blood vessel includes the steps of viewing the image of the target area of the skin as displayed on the display, viewing the unenhanced image on the target area of the skin and adjusting the display to correct the enhanced image displayed on display for depth perception differences between the enhanced image and the unenhanced image. 
   The preferred embodiment of the method includes the step of optimizing the system. In some embodiments, the optimizing step includes using a data input to specify an enhancement algorithm stored in memory to be used by the digital signal processor to generate the enhanced image. In some such embodiments, the enhancement algorithm is selected based upon a factor selected from a group consisting of a body type, pigmentation, and age of the patient. In other embodiments, the optimizing step includes the step of using the data input to adjust an intensity level of the infrared emitter or emitters. 
   In embodiments of the method in which the hypodermic needle is an infrared viewable hypodermic needle, the step of inserting a hypodermic needle into the target blood vessel may also include the step of viewing the infrared viewable hypodermic needle on the display during and after insertion into the target blood vessel. 
   Finally, some embodiments of the method also include the steps of removing the headset and powering off the system. 
   Therefore, it is an aspect of the invention to provide an improved system and method for locating and accessing a target blood vessel that that produces high quality images in near “real time” such that the system may be used by medical personnel during venepuncture. 
   It is a further aspect of the invention to provide an improved system and method for locating and accessing a target blood vessel that allows target blood vessels to be more accurately and rapidly located than is possible using current systems and methods. 
   It is a further aspect of the invention to provide an improved system and method for locating and accessing a target blood vessel that allows target blood vessels to be more easily located in difficult conditions and body types (e.g., obese patients, dark pigmentation skin, neonates, collapsed veins, low lighting). 
   It is a further aspect of the invention to provide an improved system and method for locating and accessing a target blood vessel that reduces patient pain and trauma, both emotionally and physically. 
   It is a still further aspect of the invention to provide an improved system and method for locating and accessing a target blood vessel that allows minimally trained medical staff to provide IV access. 
   These aspects of the invention are not meant to be exclusive and other features, aspects, and advantages of the present invention will be readily apparent to those of ordinary skill in the art when read in conjunction with the following description, appended claims and accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front isometric view of the preferred embodiment of the system of the present invention. 
       FIG. 2  is a rear isometric view of the preferred embodiment of the system of the present invention. 
       FIG. 3  is an isometric view of the preferred embodiment of the system worn on the head of a user. 
       FIG. 4  is a diagram illustrating the operation of one embodiment of the infrared imaging system of the present invention to detect subcutaneous blood vessels. 
       FIG. 5A  is an image of a human forearm showing unpolarized visible spectrum light reflected from the forearm and captured by a camera. 
       FIG. 5B  is a raw image of the human forearm of  FIG. 5A  showing cross-polarized infrared spectrum light reflected from the forearm and captured by the CMOS camera of the preferred system of the present invention. 
       FIG. 5C  is an enhanced image resulting from the operation of the computer program product of the present invention on the raw image of the human forearm of  FIG. 5B . 
       FIG. 6  is a flow diagram of the preferred method of using the system to aid in locating and inserting a hypodermic needle into a blood vessel in accordance with the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1-3  show the preferred embodiment of the imaging system  10  of the present invention. The preferred embodiment of the system  10  includes a headset  12  to which all system components are attached. The preferred headset  12  includes two plastic bands  14 , 16 ; a vertical band  14  connected to sides of a horizontal band  16 . The vertical band  14 , holding most of the system components, generally acts as a load-bearing member, while the horizontal band  16  is adjustable such that it snugly fits about the forehead of the person using the system. 
   A pivoting housing  18  is attached to the headband  12 . The housing  18  is substantially hollow and is sized to house and protect a headset electronics unit  120  disposed therein. Attached to the housing  18  are a power supply  20 , an image capture assembly  30 , and an enhanced image display unit  40 . 
   The power supply  20  for the headset electronics unit  120  preferably includes two rechargeable lithium ion batteries  22 , which are connected to the electronics unit via a pair of battery terminals  24  attached to the rear of the housing  18 . The rechargeable lithium ion batteries  22  are preferably of the same type commonly used with video camcorders, as these are readily available, are rechargeable without fear of memory problems, make the unit completely portable, and will provide sufficient power to the headset electronics unit  120  when two such batteries  22  are used. However, it is recognized that any power supply  20  known in the art to supply power to electronics, such as alternating current power plugs, may be employed to achieve similar results. 
   The image capture assembly  30  is powered thorough the headset electronics unit  120  and includes a pair of infrared emitters  32 ,  34 , and a camera  38 , or other infrared detector, disposed between the infrared emitters  32 , 34 . The infrared emitters  32 , 34  and camera  38  are preferably attached to a common mounting surface  31  and are pivotally connected to a pair of extension arms  36  that extend from the housing  18 . Mounting in this manner is preferred as it allows the emitters  32 ,  34  and camera  38  to be aimed at the proper target, regardless of the height or posture of the person wearing the headset. However, it is recognized that both could be fixedly attached to the headset, provided the relationship between the emitters  32 ,  34  and camera  38  remained constant. 
   The infrared emitters  32 ,  34  of the preferred embodiment are surface mount LEDs (light emitting diodes) that feature a built-in micro reflector. Light emitting diodes are particularly convenient when positioned about the head because they are found to generate less heat then conventional bulbs and do not require frequent changing. Further, surface mount LED&#39;s that emit infrared light through light shaping diffusers to provide uniform light and are readily adapted for attachment to a variety of other flat filter media. The preferred infrared emitters  32 ,  34  each utilize a row, or array, of such LED&#39;s in front of which is disposed a light shaping diffuser (not shown). Such emitters  32 ,  34  may be purchased from Phoenix Electric Co., Ltd., Torrance, Calif. First polarizing filters  33 ,  35  are mounted in front to the light shaping diffusers of each of the infrared emitters  32 ,  34 . These polarizing filters  33 ,  35  are preferably flexible linear near-infrared polarizing filters, type HR, available from the 3M Corporation of St. Paul, Minn. In operation, the LED&#39;s are powered through the headset electronics unit  120  and emit infrared light, which passes through the light shaping diffuser  205  and the first polarizing filters  33 ,  35  to produce the polarized infrared light  215  that is directed upon the object to be viewed. 
   The camera  38  is adapted to capture the infrared light  230  reflected off of the object to be viewed and to provide this “raw image data” to the headset electronics unit  120 . The preferred camera  38  is a monochrome CMOS camera that includes a high pass filter (not shown) that filters out all light outside of the infrared spectrum, including visible light. A CMOS camera is preferred as it produces pure digital video, rather than the analog video produced by the CCD cameras disclosed in the prior art, and is, therefore, not susceptible to losses, errors or time delays inherent in analog to digital conversion of the image. The CMOS camera is may be any number of such cameras available on the market, including the OMNIVISION® model OV7120, 640×480 pixel CMOS camera, and the MOTOROLA® model XCM20014. In the test units, the OMNIVISION® camera was used with good success. However, it is believed that the MOTOROLA® camera will be preferred in production due to its enhanced sensitivity to infrared light and the increased sharpness of the raw image produced thereby. 
   A camera lens  240  is preferably disposed in front of the camera  38 . This camera lens  240  is preferably an optical lens that provides an image focal length that is appropriate for detection by the camera  38 , preferably between six inches and fourteen inches, eliminates all non-near IR light, and reduces interference from other light signals. The preferred camera lens  240  is not adjustable by the user. However, other embodiments of the invention include a camera lens  240  that may be adjusted by the user in order to magnify and/or sharpen the image received by the camera  38 . Still others eschew the use of a separate camera lens  240  completely and rely upon the detection of unfocused light by the camera  38 , or other infrared detector. 
   A second linear polarizing filter  39  is disposed in front of the lens  240  of the camera  38 . This second polarizing filter  39  is preferably positioned so as to be perpendicular to the direction of polarization through the first polarizing filters  33 ,  35  in front of the infrared emitters  32 ,  34 , effectively cross polarizing the light detected by the camera  38  to reduce spectral reflection. The polarizing filter  39  was selected for its high transmission of near-infrared light and high extinction of cross-polarized glare. Such polarizer may be purchased from Meadowlark Optics, Inc. of Frederick, Colorado under the trademark VERSALIGHT®. 
   The camera  38  is in communication with the headset electronics unit  120  and sends the raw image data to the unit for processing. The headset electronics unit includes the electronics required to supply power from the power supply  20  to the image capture assembly  30 , and an enhanced image display unit  40 , and the compatible digital processing unit  122  which accepts the raw image data from the camera  38 , enhances the raw image, and sends an output of the enhanced image to the enhanced image display unit  40  and, optionally, to an interface  52 . In the preferred embodiment, this interface  52  is standard VGA output  52 . However, interface  52  may be any electronic data I/O interface capable of transmitting and receiving digital data to and from one or more input or output devices, such as an external monitor, external storage device, peripheral computer, or network communication path. 
   The preferred digital signal-processing unit  122  is a digital media evaluation kit produced by ATEME, Ltd. SA, Paris, France under model number DMEK6414, which uses a Texas Instruments TMS320C6414 digital signal processor. This processing unit  122  is preferably programmed with an embodiment of the computer program means described in the applicants&#39; co-pending U.S. patent application Ser. No. 10/760,051, in order to enhance the images. The image enhancement algorithms embodied in the computer program means utilize several elemental processing blocks, including (1) Gaussian Blurring a raw image with a kernel radius of 15, (2) adding the inverse Gaussian-blurred image to the raw image, and (3) level adjusting the result to use the entire dynamic range. Image enhancement is performed in a series of steps, which are coded into a computer program that runs on digital signal processor  120 . The programming languages are typically C language and assembly language native to digital signal processor  120 . An example algorithm is as follows: 
                                                               ON device startup       BEGIN                Perform Initialization of Blur Kernel            END       WHILE device = ON       BEGIN                Acquire digital image data from the camera into RAM buffer           Save non-enhanced copy of the image data into another RAM buffer           Perform 2D transform of image data in first RAM buffer into the           frequency domain           Perform smoothing of transformed image data USING Blur Kernel           Perform 2D inverse transform of smoothed image data into           the spatial domain           Perform inversion of the smoothed image data           Perform add the inverted image data to the non-enhanced copy           of the image data           Perform contrast stretching           Perform gamma enhancement.           Send the enhanced image data to the display buffer            END                    
However, it is understood that other systems may use different means for similarly enhancing such images in near real-time and, therefore, it is understood that all embodiments of the invention need not include this program product or perform the methods described in the above referenced patent application.
 
   The enhanced image is outputted from the processing unit to the enhanced image display unit  40 . The preferred display unit  40  is distributed by i-O Display Systems of Sacramento, Calif., under the trademark I-Glasses VGA. This display unit  40  includes a binocular display that includes a pair of LCD screens in front of which are disposed a pair of optical lenses  42 ,  44  that allow the focal length to be adjusted for ease of viewing. The preferred an optical lenses  42 ,  44  provides image depth perception compensation to the user when the system  10  is used in a bifocal mode. That is, when the user views the body target area via display  150 , the optical lenses  42 ,  44  ensure that the image appears similarly sized and distanced as when the user views the target area without using display  40 . However, it is understood that a monocular display unit  40  having no such focal length adjustment could likewise be used. The preferred display unit  40  also includes an on-screen display that is not currently used, but may be used in the future to show what enhancement option has been chosen by the user. 
   The system  10  may be used in a total immersion mode, in which the user focuses on the target area by using exclusively display  40 . Alternatively, the system  10  may be used in a bifocal mode, in which the user views the body target area via a combination of display  40  and the naked eye. In bifocal mode, the user alternates between viewing the enhanced and non-enhanced image views of the body target area, by directing his/her gaze upward to display  40  or downward toward the body target area and away from display  150 . 
     FIG. 4  illustrates one embodiment of the infrared imaging system  10  used to view subcutaneous blood vessels  220 , such as arteries, veins, and capillary beds, which are present under the surface  225  of normal human skin. The infrared imaging system  10  described in connection with  FIG. 4  includes all of the features of the preferred embodiment described above, in addition to including a camera lens  240 , image data storage means  445 , a data input  250 , and data output  255 . 
   Image data storage means  245  is any means of digital data storage that is compatible with digital signal processor  120  and may be used to store multiple enhanced and/or unenhanced images for future viewing. Examples of such image data storage are random access memory (RAM), read-only memory (ROM), personal computer memory card international association (PCMCIA) memory card, and memory stick. Depending on memory size, hundreds or thousands of separate images may be stored on the image data storage means  245 . 
   Data output  250  is any external device upon which the image data produced by digital signal processor  120  may be viewed, stored, or further analyzed or conditioned. Examples of data output  250  devices include external video displays, external microprocessors, hard drives, and communication networks. Data output  250  interfaces with digital signal processor  120  via interface  52 . 
   Data input  255  is any device through which the user of the system  10  inputs data to digital signal processor  122  in selecting, for example, the appropriate enhancement algorithm, adjusting display parameters, and/or choosing lighting intensity levels. Examples of data input  255  devices include external keyboards, keypads, personal digital assistants (PDA), or a voice recognition system made up of hardware and software that allow data to be inputted without the use of the user&#39;s hands. Data input  255  may be an external device that interfaces with digital signal processor  120  via interface  52 , or may be integrated directly into the computing unit. 
   Digital data path  265  is an electronic pathway through which an electronic signal is transmitted from the camera  38  to the digital signal processor  122 . 
   In operation, the infrared imaging system  10  is powered on and the infrared emitters  32 ,  34  produce the necessary intensity of IR light, preferably at 850 nm and 950 nm wavelengths, required to interact and reflect from oxyhemoglobin and deoxyhemoglobin contained within normal blood. The resulting light path passes through diffuser system  205 , where it is dispersed into a beam of uniform incident light  215  of optimal intensity and wavelength. Incident light  215  passes through first polarizers  33 ,  35 , which provide a first plane of polarization. Polarization of incident light  215  reduces the glare produced by visible light by reflection from skin surface  225 . Incident light  215  is partially absorbed by the oxyhemoglobin and deoxyhemoglobin that is contained with subcutaneous blood vessels  220  and, thus, produces reflected light  230 . 
   Reflected light  230  passes through second polarizer  39 , which provides a second plane of polarization. The second plane of polarization may be parallel, orthogonal, or incrementally adjusted to any rotational position, relative to the first plane of polarization provided by first polarizers  33 ,  35 . Reflected light  230 , passes through first lens  240 , which provides an image focal length that is appropriate for detection by the camera  38 , eliminates all non-near IR light, and reduces interference from other light signals. 
   Camera  38  detects reflected light  230  and converts it to an electronic digital signal by using CCD, CMOS, or other image detection technology. The resulting digital signal is transmitted to digital signal processor  122  via digital signal path  265 . Digital signal processor  122  utilizes a number of algorithms to enhance the appearance of objects that have the spatial qualities of blood vessels, so that the user can distinguish blood vessels easily from other features when Viewed on display  40 . Such enhancement might include, for example, image amplification, filtering of visible light, and image analysis. The resulting digital signal is transmitted to display  40  via digital signal path  265 , where it is rendered visible by LCD, CRT, or other display technology. Additionally, the resulting digital signal may be outputted to an external viewing, analysis, or storage device via interface  52 . The image produced by display  40  is then corrected for depth perception by second lens  260 , such that, when the user views the body target area via display  40 , the image appears similarly sized and distanced as when the user views the target area with the naked eye. 
     FIGS. 5A ,  5 B and  5 C demonstrate the image enhancement produced by the system of the present invention.  FIG. 5A  is a photograph of a human forearm using light from the visible spectrum. As seen from this photograph, it is difficult to locate the veins upon visual inspection.  FIG. 5B  is a raw image of the same human forearm sent from the image capture assembly  30  of the present invention to the processing unit. The veins in this image are considerably more visible than those in  FIG. 5A . However, they are not sufficiently dark and well defined to allow easy location of the veins during venepuncture.  FIG. 5C  is an enhanced image using the image enhancement process of the present invention. As can be seen from this figure, the veins are very dark and, therefore, are easily located for venepuncture. 
     FIG. 6  illustrates a flow diagram of a method  300  of using the system  10  to aid in the insertion of a hypodermic needle into a blood vessel in accordance with the invention. Method  300  includes the steps of: 
   Step  310 : Preparing Body Target Area 
   In this step, a user, such as a medical practitioner (e.g., doctor, nurse, or technician), prepares the patient&#39;s body target area for injection by using standard medical practices. This might include, for example, positioning the target body area (e.g., arm), applying a tourniquet, swabbing the target area with disinfectant, and palpating the target area. Method  300  then proceeds to step  320 . 
   Step  320 : Putting on the Headset  12   
   In this step, the user places the headset  12  on his/her head and adjusts head mount  16  for size, comfort, and a secure fit. Method  300  then proceeds to step  330 . 
   Step  330 : Powering Up the System 
   In this step, the user powers up the system  10 , by activating a switch controlling the power source  20 . Method  300  proceeds to step  340 . 
   Step  340 : Optimizing the System 
   In this step, the user uses data input  255  to adjust various parameters of the system  10 , including specifying the appropriate digital signal processor  120  algorithms (according to, for example, the patient&#39;s body type, pigmentation, age), intensity levels and/or wavelengths of light produced by the infrared emitters  32 ,  34 , and parameters for the images to be viewed on the display  40 . Method  300  then proceeds to step  350 . 
   It should be noted that Steps  320 ,  330 , and  340  may be performed in any order, e.g., the user may power up the system  10  and optimize it, prior to putting it on. Further, it is recognized that a optimizing step  340  may be eliminated altogether, with settings being preset at the factory. 
   Step  350 : Locating Target Blood Vessel 
   In this step, the user searches non-invasively for the desired target blood vessel(s) (e.g., vein, artery, or capillary bed), by directing the incident light  215  from the infrared emitters  32 ,  34  on the body target area and viewing the target area on display  40 . As viewed on display  40 , the target blood vessel(s) will be visually enhanced, i.e., appear darker than the surrounding tissue, which enables the user to insert a hypodermic needle more accurately and rapidly, in order to gain IV access for injection or blood withdrawal. Because of the hands-free operation of the system  10  the user is free to handle the body target area with both hands, for stability, further palpation, and cleansing, for example. Using the system  10  in a bifocal mode, the user may look down from display  40  to see the body target area as it appears under normal, non-enhanced conditions. Based upon a comparison of the image on the display  38  and the unenhanced image viewed in bifocal mode, the user may then adjust the camera lens  24 , second lens  260  and/or display  38  to compensate for differences in the enhanced image and unenhanced image. Method  300  proceeds to step  360 . 
   Step  360 : Inserting the Needle 
   In this step, the user, taking advantage of the hand-free operation of system  10 , pierces skin surface  225  and inserts a hypodermic needle into the target blood vessel, in order to gain IV access for a procedure, such as, for example, injection or blood withdrawal. Using the enhanced image of the target blood vessel displayed on display  40 , the user may pierce the appropriate blood vessel more accurately and rapidly and, thus, save time and money and reduce the patient&#39;s physical and emotional pain and trauma. Further, in cases where an infrared viewable needle is used, i.e. one upon which an IR-opaque or IR-reflective substance or pattern is applied, the step also includes the step of viewing the needle position and travel path upon the display. Method  300  proceeds to step  370 . 
   Step  370 : Completing Procedure 
   In this step, the user completes the procedure, for example, drug injection or blood withdrawal process, by using standard medical practices. This may include, but is not limited to, for example, allowing a small amount blood to flow into the syringe, releasing the tourniquet, injecting drugs into the target blood vessel or drawing blood into a capture chamber, and removing the hypodermic needle. Method  300  proceeds to step  380 . 
   Step  380 : Removing the Headset  12   
   In this step, the user removes the headset  12  from his/her head and powers off the system  10 . Alternatively, the user prepares additional patients/body target areas for imaging and injection. Method  300  ends. 
   Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions would be readily apparent to those of ordinary skill in the art. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.