The present invention relates generally to the field of medical imaging, and more particularly to the illumination of veins and other tissues in the body.
In order to safely and effectively administer intravenous (IV) lines, or draw blood from a patient, it is critical for the health care provider to be able to locate suitable veins. In many instances, experienced medical personnel are able to locate veins by visual inspection under normal lighting conditions, and/or by feel. However, in some cases, the use of sophisticated medical devices is necessary in order to assist in the location of veins on a patient.
Imaging of subcutaneous veins using trans-illumination is generally known in the medical industry. Trans-illumination devices use light from the visible spectrum, and direct it into the tissue that is to be investigated. Examples of such known devices are the VEINLITE®, VEINLITE LED®, and VEINLITE EMS, vein imaging devices commercially available from Translite LLC of Sugar Land, Tex.
The VEINLITE® vein imaging device is a fiber optic based transilluminator for mapping of varicose veins and vein access. The light source is connected by a fiber optic cable to a light emission ring for mapping superficial varicose veins and finding feeder veins for sclerotherapy. The VEINLITE LED® vein imaging device is designed primarily for vein access, and is provided in a self-contained, pocket-sized handheld case; it includes a series of 24 dual-colored light-emitting-diodes (LEDs) and a lithium rechargeable battery. The 24 dual-colored LEDs are arranged in a circular arc pattern, extending over approximately a 290-degree arc. The ring of LEDs is held against a patient's body in the probable vicinity of a vein, and the LED light is directed inwardly into the skin to illuminate a vein that passes below the central hollow of the LED ring. The VEINLITE EMS is a less expensive form of the VEINLITE LED® vein imaging device, including 16 dual color LEDs and using disposable batteries.
Such LED trans-illumination devices have many important benefits, including simplicity, relatively low cost, negligible generation of heat in contact with the patient's skin, and portability. However, such devices are not always effective for locating veins due to the high variability in the absorption and scattering of visible light within human tissue of patients. Difficulties often result from variations in skin tones, body fat, and other physical characteristics. Typically, LED based trans-illumination devices use colors in the near-infrared portion of the visible spectrum, such as red or orange, in order to provide the best view of subcutaneous veins. Some trans-illumination devices also use white light in conjunction with red or orange in an attempt to augment the effectiveness of the longer wavelength red or orange light alone. However, even using visible light at the longest possible wavelengths, subcutaneous veins are not always easily visible on every patient for a variety of reasons.
As an example, patients with darker skin color are known to be more difficult to illuminate, possibly due to the absorption of light by the melanin which creates darker skin tones. Additionally, veins in obese patients are also known to be more difficult to trans-illuminate due to the increased amount of fatty tissue surrounding the vein, which serves to scatter the emitted light and obscure the subcutaneous veins.
In addition, while portable vein imaging devices like the above-described VEINLITE LED® device are pocket-sized, the case is still relatively bulky, particularly when a nurse or medical technician is trying to stabilize the device with one hand while placing a vein puncture needle with the other hand. Moreover, the ring design of the LED light head illuminates only a small portion of a vein at a time, and the relatively small portion of the ring that is left open is insufficient to permit convenient placement of a vein puncture needle within the vein, once the vein is located.
Since simple LED based trans-illumination devices are not always effective in making veins easy to locate, alternate technologies are employed for the purpose of vein location. Imaging devices using infrared (IR) radiation are also very popular, but are inherently more costly and difficult to use. Since the IR wavelengths are not visible to the human eye, electronic detection means must be employed to produce an image that can be viewed by a user, with the resulting captured image projected onto a display or back onto the patient's skin. Thus, IR systems require much more sophisticated electronics, and furthermore result in the health care provider necessarily viewing a projected image of the tissue, rather than the tissue itself. One such example of an IR-based imaging system for viewing veins is disclosed in U.S. Pat. No. 6,424,858 to Williams.
Alternatively, ultrasound imaging technology has also been used to locate veins that are otherwise difficult to visualize. However, like the IR systems discussed above, ultrasound technology is far more costly and difficult to use than a simple LED based trans-illumination device. Furthermore, ultrasound technology by its nature is able to image deeply within human tissue, but is often ineffective for imaging near the skin's surface. Thus, ultrasound systems may in fact have difficulty imaging the most accessible veins near the skin's surface.
The use of multi-colored lights for detecting blood remnants is known in the art. U.S. Pat. No. 7,621,653 to Hendrie discloses an LED-based flashlight which continuously emits blue, green, or white light, while blinking a red light on and off. The patent specification states that this device is particularly useful to forensic investigators and/or hunters by enhancing nighttime visibility of blood traces left at a crime scene, or in the wild by wounded animals. The disclosed device includes an LED module having a first LED bank for emitting light of a first wavelength, and a second LED bank coupled for emitting light of a second wavelength. A control circuit causes the first LED bank to illuminate continuously and the second LED bank to flash on and off at a predetermined frequency. This patent is not directed to visualizing veins within a living body, but rather to detecting blood traces outside a living body.
Further, applications for LED-based trans-illumination devices are not limited to vein imaging. Other tissue imaging needs clearly exist. However, it would be overly expensive if a hospital, clinic, or other medical facility had to have on-hand separate medical imaging devices for different applications, each with its own power source and controller circuitry.
Accordingly, it is an object of the present invention to provide an LED-based trans-illumination device which assists a health care provider in being able to locate suitable veins for a wider variety of patients.
Another object of the present invention is to provide such a device using light from the visible spectrum for producing an image that can be directly viewed by a user without the need for special detection equipment or display devices.
Still another object of the present invention is to provide such a device which can be manufactured simply and inexpensively.
A further object of the present invention is to provide such a device which is portable, easy to use, and easy to position and/or tape against a patient's body while vein puncture, or other procedures, are being performed.
A yet further object of the present invention is to provide such a device which is portable, having a small remote LED head that has high intensity light available for long periods of time due to its cable connection to a base unit which can incorporate a larger power source.
A still further object of the present invention is to provide such a device that functions well even with patients having darker skin tones, or wherein fatty tissues surround features of interest.
Yet another object of the present invention is to provide such a device that can illuminate a greater portion of a vein, or other tissue of interest, while avoiding physical interference with needles or other medical implements to be inserted into the body.
A yet further object of the present invention is to minimize the number of different types of tissue imaging devices that a hospital, clinic, or other medical facility must have on-hand to image different types of tissues in the body.
Yet another object of the present invention is to provide such a device in a form wherein the need to sterilize the device after each use can be simplified, or even eliminated.
These and other objects of the present invention will become more apparent to those skilled in the art as the description thereof proceeds.
Briefly described, and in accordance with a preferred embodiment of the present invention, a trans-illumination device includes at least a first set of LEDs of a first wavelength in the visible spectrum, and at least a second set of LEDs of a second wavelength in the visible spectrum, the second wavelength differing from the first wavelength. A control circuit has a first output coupled to the first set of LEDs to cause the first set of LEDs to emit light of the first wavelength. The control circuit has a second output coupled to the second set of LEDs to emit light of the second wavelength. The LEDs are configured in a light head placed against a patient's skin for directing emitted light into the patient's skin to illuminate subcutaneous tissues. The control circuit and source of electrical power are preferably housed in a separate base unit detachably coupled to the light head by an electrical cable.
In a preferred embodiment of the present invention, the control circuit includes a mode selection feature for choosing the manner in which the two sets of LEDs are illuminated. For example, in one mode, the control circuit causes the first set of LEDs to be illuminated continuously, without perceptible variation in intensity, while periodically modulating the intensity of the second set of LEDs in a gradual fashion. The resulting light emitted by the second set of LEDs takes on a pulsed appearance, enhancing the visibility of subcutaneous tissues, and effectively providing a depth-of-field image of such subcutaneous tissues. Preferably, the intensity of the second set of LEDs is varied by modulating the pulse width of electrical pulses used to turn on the second set of LEDs.
In one preferred embodiment, the light head includes three sets of LEDs generally corresponding to the colors red, orange and yellow. In this preferred embodiment, the orange and yellow LEDs are maintained at relatively constant intensity during use, while the red LEDs are modulated to range between maximum intensity and approximately 25% of maximum intensity over a predetermined time interval. Preferably, such time interval is at least one-half second in duration; in the preferred embodiment, such time interval is approximately one to two seconds.
Preferably, the control circuit also allows other modes of operation. For example, the control circuit may periodically vary the intensity of the first set of LEDs in the same manner as, and in phase with, the modulated intensity of the second set of LEDs. Alternatively, the control circuit may periodically vary the intensity of the first set of LEDs in the same manner as, but in a different phase relationship to, the modulated intensity of the second set of LEDs. Another optional mode of operation causes the second set of LEDs to illuminate in the pulsed manner described above, while causing the first set of LEDs to stay off. Another optional mode provides full intensity for all of the different colors of the LEDs. Yet another optional mode sets the intensity levels of both the first and second set of LEDs to constant values which are selected in such a manner so as to achieve a desired color mix.
Preferably, the control circuit includes a microcontroller programmed with firmware to determine the manner in which the different sets of LEDs are illuminated. If desired, such firmware may be re-programmed from time to time to alter the illumination modes initially programmed into the microcontroller. A mode selection switch allows a user to select a mode that best suits the physiology of the patient being treated.
In a preferred embodiment of the present invention, the first and second sets of LEDs are secured to, and supported by, a light head that projects the light emitted by such LEDs on opposing sides of the tissues being imaged. The light head preferably includes at least a first row of LEDs on one side of the tissues being imaged, and at least a second row of LEDs on the other side of the tissues being imaged. The first and second rows of LEDs extend generally parallel to each other, and are spaced apart from each other by a predetermined distance D. Each of the first and second rows of LEDs extends for a length of at least twice the predetermined distance D to effectively illuminate veins or other subcutaneous tissues, while providing sufficient access to the underlying tissues for insertion of a needle or other medical instrument. In such preferred embodiment, the first set of LEDs and second set of LEDs are alternated in a repeating pattern along each of the aforementioned first and second rows of LEDs. Thus, each row of LEDs includes LEDs that emit the first wavelength of light as well as LEDs that emit the second wavelength of light.
Preferably, the light head includes two generally parallel bars to support the first and second rows of LEDs. Each of the two bars has opposing first and second ends, and the first ends of such bars are joined by a connecting element to form a closed end of the light head; the second ends of the two bars are left unconnected to leave an open end of the light head. In the preferred embodiment, at least some of the LEDs from the first and second sets of LEDs are secured to and supported by such connecting element to emit light into the patient's skin from the closed end of the light head.
In one preferred form of the present invention, the light head is provided as a minimal configuration element which essentially includes only the first and second sets of LEDs, physical support for such LEDs, and electrical conductors for routing the electrical signals to such LEDs to illuminate them in the manner described above. A separate base unit incorporates the above-described control circuit and a source of electrical power. A connection cord extends between the base unit and the light head to provide driving electrical signals that illuminate the LEDs in the desired manner. The light head includes an electrical connector for allowing the connection cord to be removably attached thereto. By providing the light head in such a minimal configuration form, the cost and complexity of each light head is minimized. The cost may actually be low enough to allow such light heads to be disposable, avoiding the need to sterilize the light head or otherwise guard against contamination of the light head from one patient to the next. Alternatively, by providing the light head in such a minimal configuration form, sterilization of the light head, as by autoclaving, between uses is simplified.
Another alternative to avoid the need to sterilize the light head, while minimizing the portion which is discarded, is to provide a protective plastic cover which may be clipped onto the light head prior to its use on a patient, and which prevents blood or other fluids from making contact with the first and second sets of LEDs, the supporting members, and the electrical conductors. An important aspect of the head design is the manner in which light is channeled from the LEDs to the skin surface. In the disposable cover case, clear windowing can be incorporated with lens and or diffuser characteristics. Incorporating lenses into the disposable cover provides an inexpensive method to allow focal and diffusion characteristic options that may be tailored to the patient's tissue characteristics. In this preferred embodiment, a printed circuit board includes a series of electrical conductors. A first set of LEDs of one color, and a second set of LEDs of a different color, are supported upon the lower surface of the printed circuit board and electrically coupled to the electrical conductors of the printed circuit board. A pc board support member, having a shape generally matching that of the printed circuit board, receives the printed circuit board, while having one or more apertures aligned with the LEDs for allowing light emitted by such LEDs to pass therethrough.
A disposable base, generally matching the shape of the pc board support member, is detachably coupled to the pc board support member, an inner surface of the disposable base releasably engaging the outer surface of the pc board support member, and the outer surface of the disposable base being adapted to be engaged with a patient's skin. In the preferred embodiment, the disposable base likewise includes one or more base apertures aligned with the apertures of the pc board support member for allowing light emitted by the first and second plurality of LEDs to pass through such base aperture into the patient's skin. Ideally, the disposable base includes one or more translucent lenses disposed within such base apertures for sealing the base apertures while directing light emitted by the LEDs into the patient's skin.
The lower cost of minimal configuration light heads facilitates providing two or more different styles of light heads, each incorporating a different profile and/or different pattern of LEDs. Each of such different styles of light heads is adapted to be connected to the same base unit, allowing for simple and rapid exchange of such light heads when required by the circumstances. Different styles of light heads may be better suited to visualize different subcutaneous features, yet all of such light heads may be driven by the same base unit. For example, a light head for pediatric use may be of smaller size, and perhaps include a smaller number of LEDs. Of course, a base unit may be used in conjunction with two or more light heads of the same type or style, particularly if such light heads are disposable after single-use application, or if two or more patients co-incidentally require the use of such medical imaging device at approximately the same time.
In an alternate embodiment, the light head is provided in the form of a stand-alone case that contains the aforementioned LED control circuit and a power source, e.g., a battery. In this alternate embodiment, the base unit is essentially used to re-charge the light head. Preferably, the base unit includes its own higher-capacity battery, and can be plugged into an AC outlet for rapid recharging of its higher-capacity battery. The base unit includes a docking port adapted to receive the light head when the light head is not in use. When the light head is docked with the base unit, electrical connections therebetween allow the battery with a relatively greater amp-hour capacity in the base unit to charge the battery with relatively lesser amp-hour capacity in the light head. Thus, the light head may be charged in the base unit for its next use, even if the base unit is not plugged into an AC outlet. Once the battery in the light head is re-charged, the light head is removed, or un-docked, from the base unit and is ready for use.
In
Still referring to
As shown in
Each of the first and second rows of LEDs (118 and 120, respectively) extends for a length of approximately twice the predetermined distance D to effectively illuminate veins or other subcutaneous tissues. Thus, if separation distance D is one inch, then the LEDs supported within each of arms 106 and 108 preferably extend over a length of approximately two inches. This profile has been found to adequately illuminate subcutaneous tissues while providing sufficient access to the underlying tissues for insertion of a needle or other medical instrument. If desired, the length over which the LEDs supported within each of arms 106 and 108 extends may be more than double the separation distance D.
Preferably, the three sets of red, orange and yellow LEDs are alternated in a repeating pattern along each of the aforementioned first and second rows of LEDs 118 and 120, as well as in the connecting element 110. Thus, row 118 includes red, yellow and orange LEDs, and row 120 also includes red, yellow and orange LEDs.
In the preferred embodiment, light head 100 is encased in a medical grade plastic, as the light head is likely to be exposed to human tissues and human bodily fluids. The LEDs are preferably surface-mounted LEDs that are flow-soldered to a U-shaped supporting printed circuit board that is electrically connected to RJ-11 connector 104 (see
Alternatively, the printed circuit board may connect red LEDs 112a-112j in parallel with one another, such that the LED anodes are connected to a common conductor, and may similarly connect orange LEDs 114a-114j in parallel with one another with the device anodes connected to a second common conductor, and may similarly connect yellow LEDs 116a-116j in parallel with one another with the device anodes connected to a third common conductor. Those skilled in the art can appreciate that other combinations of series and parallel connection are also possible.
The aforementioned RJ-11 connectors are commonly used in electronic products, and are often used to connect telephones to wall-mounted telephone jacks. While telephones typically require only two active conductors, the RJ-11 connector standard allows for up to six separate conductors. Thus, in the preferred embodiment of the present invention, RJ-11 connector 104 can support up to three independent strings of LEDs. RJ-11 connectors also include locking tabs, which prevent lighting head 100 from inadvertent disconnection from its associated base unit. Those skilled in the art will appreciate that, for light heads incorporating more than three different LED strings, a different connector, with greater conductor capacity could be used, or that other types of connectors, such as TRS (Tip, Ring, Sleeve), which are commonly used for audio applications, may also be used.
The plastic used to form light head 102 consists of a two piece assembly which is then closed about the aforementioned printed circuit board by ultrasonic welding in order to create a robust assembly that is resistant to moisture ingress. Alternatively, the two piece assembly used to form light head 102 may be designed to snap together to simplify its manufacture. Light emitting channels formed in the underside of arms 106 and 108 permit the light emitted by LEDs 112, 114 and 116 to shine outwardly into the patient's skin. At least the surface which covers the LEDs 112, 114 and 116 themselves must be clear to allow the transmission of light from the LEDs; the balance of the plastic assembly used to form light head 100 is preferably opaque to minimize the amount of incident light emitting from the LED head which is not directed into the tissues being investigated.
The printed circuit boards and plastic enclosures used to form light head 100 may be created in a variety of shapes, sizes, and profiles to best visualize different subcutaneous features of interest. Similarly, different light heads may incorporate different pattern of LEDs. For example, a light head for pediatric use may be of smaller size, and perhaps include a smaller number of LEDs. Each of such different styles of light heads may nonetheless be connected to the same base unit.
In use, light head 100 is placed against a patient's skin for directing emitted light emitted by LEDs 112, 114 and 116 into the patient's skin to illuminate subcutaneous tissues. Light emitted by the LEDs in the opposing arms 106 and 108 of light head 100 projects into the patient's skin on opposing sides of the tissues being imaged.
As shown in
Referring now to
The upper face 202 of base unit 200 includes two membrane-type electrical switches 204 and 206. Switch 204 is a power switch for turning base unit 200 on and off. Switch 206 is a mode selection switch to be explained in greater detail below. End wall 208 of base unit 200 includes an RJ-11 connector (not visible in
In
Turning to the block diagram schematic shown in
Still referring to
As shown in
In the event of a low battery condition, battery charger IC 304 signals microcontroller 300 to cause the green PWR LED (incorporated within membrane power switch 204) to blink at a 1 Hz rate in order to warn the user that base unit 200 has approximately 45 minutes of remaining operation before it must be recharged.
The block diagram schematic of
Referring jointly to
Microcontroller 300 is programmed (using inputs D+ and D− coupled to mini USB) to generate three pulse width modulated (PWM) signals on output lines 306, 308 and 310, to drive the three banks of LEDs in the light head. The flash memory in microcontroller 300 can be programmed using the D+ and D− input signal lines coupled to mini-USB port 212; during programming, mini-USB port 212′ is coupled by an appropriate cable to the USB port of a computer. The program is stored as firmware in flash memory of microcontroller.
Light intensity from the LEDs (112′, 114′, 116′) can be adjusted by varying the duty cycle of the pulse width modulated (PWM) signal used to drive each of the different colors. The PWM signals can be varied from a minimum of 0% (no illumination) to a maximum of virtually 100% (maximum intensity). The microcontroller firmware is preferably programmed to drive the three independent LED strings (red, orange, yellow) in one of four predetermined modes. These user modes vary the intensity of the light provided by the LED strings by varying the duty cycle of the PWM signal associated with each of the LED strings. Since three separate pulse-width modulated outputs are provided by microcontroller 300, the three LED strings may be driven completely independently of one another. The pulse width modulated signals 306, 308 and 310 are connected to an ENABLE pin of the corresponding LED driver IC (312, 314, 316) to vary the output voltage that causes the LEDs to turn on and illuminate. Alternatively, the microcontroller firmware may be programmed with a greater number of predetermined modes.
Turning briefly to
In the timing diagram of
Time T1 is a programmable time interval representing the amount of time that should elapse between Time T0 and the beginning of a ramping up (or ramping down) of the PWM duty cycle. D1 represents a starting level of a PWM duty cycle at time T1, and D2 represents an ending level of the PWM duty cycle at time T2. The ramp rate for the “turn on” phase of the PWM duty cycle may be expressed in units of duty cycle change per unit time, and may be expressed mathematically as the rise divided by the run, or (D2−D1)/(T2−T1). Time T3 represents the time at which the PWM duty cycle should begin ramping back down, and time T4 represents the time at which the PWM duty cycle should complete its return back to initial level D1. The ramp rate for the “turn off” phase of the PWM duty cycle is the fall divided by the run, or (D2−D1)/(T4−T3). Finally, time T5 represents the end of the cycle, and the beginning of the next cycle. All of times T1, T2, T3, T4 and T5 are counted out by microcontroller 300.
Within
Referring again to
In a preferred embodiment of the present invention, Mode #1 drives the orange and yellow LEDs with relatively constant intensity, as per the graph of λ1 in
In Mode #2, all three colors (red, orange and yellow) are operated at maximum intensity. This basic mode is a good starting point for all patients initially.
Mode #3, is similar to Mode #1, except that the yellow LEDs are maintained at full intensity, while both the red and orange LEDs are gradually modulated from high to low intensity and back to high intensity. The modulation of the red and orange LEDs is preferably in phase with each other (i.e., the intensity of the red LEDs rises and falls in synchronization with the rising and falling of the intensity of the orange LEDs), although the modulation of the red and orange and LEDs could also be performed out of phase, if desired.
In Mode #4, the intensities of all three colors (red, orange and yellow) are gradually modulated, preferably in a sequential fashion rather than being in synchronization. Those skilled in the art will appreciate that other modes of operation can easily be programmed into microcontroller 300, and that more than four predetermined modes of operation may be programmed into the base unit at any given time. For example, an optional mode of operation may cause two or three of the LED colors to be held at constant intensity levels which are selected so as to provide a desired mix of wavelengths which is particularly suited to a patient's physiology.
In use, the light head may initially be positioned with arms 106 and 108 perpendicular to the likely direction of the potential vein. Once a candidate vein has been located, the light head can be rotated 90 degrees to position the vein between, and relatively parallel to, arms 106 and 108 of light head 100. This helps to ensure that the vein does not make an unexpected change of direction in the area where an IV needle will be placed. Once the light head is held or taped in place, the mode select button 206 can be advanced through its four different modes to see which mode provides the best view of the vein.
In an alternate preferred embodiment of the electronic controller shown in the circuit schematic of
Once microcontroller 436 (U1) is in its awake state, momentary depressions of button switch 438 (S1) do not produce a signal of sufficient duration to cause microcontroller 436 (U1) to re-enter its sleep state. Rather, a momentary depression of button switch 438 (S1) will produce a short duration pulse that lasts approximately the same amount of time that button switch 438 (S1) remains depressed. When button switch 438 (S1) is released, however, the pulse will quickly dissipate, as any stored charge on capacitor 446 (C4) is quickly discharged through resistor 442 (R6). However, in its awake state, microcontroller 436 is programmed to respond to rising edge transitions at input pin 4 (PA3) by advancing from one pre-programmed user mode to the next. Thus, if microcontroller 436 (U1) is in its awake state, successive momentary (i.e., less than 1 second) depressions of button switch 438 (S1) will cause microcontroller 436 to advance through its four pre-programmed user modes.
Microcontroller 436 (U1) is further programmed to provide pulse width modulated (PWM) outputs at pin 13 (PB5) and pin 12 (PB6) which are used to drive transistors 448 (Q1) and 450 (Q2), respectively. Transistors 448 and 450 are N-channel MOSFETs produced by Vishay Semiconductor. A logic high signal at the gate of transistor 448 (Q1) or 450 (Q2) will cause the respective N-channel MOSFET to conduct, and thus, connect the Tip or Middle of TRS receptacle 452 to ground through resistor 454 (R13) or resistor 456 (R15), respectively. TRS receptacle 452 is located on the controller circuit board in the base unit, and is electrically coupled to the LED light head by a three-conductor connecting cable (not shown in
An alternate embodiment of a circuit schematic of the LED lighting head for use with the present invention is shown in
Each series-connected pair of LEDs may be further connected to either the Tip or the Middle of TRS receptacle 478 (J1) on the LED lighting head by including a current-limiting resistor in the appropriate location. For example, the cathode of LED 458 (LED 2) in the series-connected LED pair formed by LEDs 458 and 460 (LED 2 and LED 4) may be connected to the Tip conductor 480 of TRS receptacle 478 (J1) if resistor 482 (“R1”) is inserted in the LED head printed circuit board. Alternatively, the cathode of LED 458 (LED 2) in the series-connected LED pair formed by LEDs 458 and 460 (LED 2 and LED 4) may be connected to the Middle conductor 484 of TRS receptacle 478 if resistor 486 (“R2”) is inserted in the LED head printed circuit board. It should be apparent to those skilled in the art that either resistor 482 or resistor 486 will be inserted into the printed circuit board, but that it would be undesirable to place both resistors R1 and R2 in the printed circuit board; doing so would cause the series-connected LED pair 458 and 460 to be connected to, and thus controlled by, signals at both the Tip and Middle conductors 480 and 484, respectively, of TRS receptacle 478.
Still referring to
In the same manner as described above, the remaining pairs of series-connected LEDs are coupled to either the Tip conductor 480 or Middle conductor 484 of TRS connector 478 on the LED lighting head printed circuit board by inserting a similar current-limiting resistor in one of two potential locations which are connected to the corresponding LED pair through electrically-conductive traces on the printed circuit board. Thus, when TRS connector 478 is connected to its corresponding receptacle 452 on the controller printed circuit board of
With reference to
As an example of how microcontroller 436 (U1) of
In a similar fashion, assume that series-connected LED pair 459/461 (LED 1 and LED 3) is connected to the Tip conductor 480 of TRS connector 478 by including resistor 496 (R3) on the LED head printed circuit board, and not including resistor 493 (“R4”). Let us further assume that LEDs 459 and 461 emit light of a second wavelength, λ2. Then, if output PB6 of microcontroller 436 is in the high state, transistor 448 (Q1) will conduct current through LED pair 459/461 (LED 1 and LED 3), causing them to emit light. The current, Imax2, flowing through LED pair 459/461 will be a function of the physical characteristics of LED pair 459/461 (LED 1 and LED 3) and transistor 448 (Q1), the value of resistor 496 (R3) on the LED head printed circuit board, and the values of resistors 497 (R2) and 454 (R13) on the controller printed circuit board. The current Imax2 will remain constant at any given temperature of operation and voltage V IN.
Those skilled in the art will appreciate that if a light emitting diode (LED) is driven by a pulse width modulated signal, then the average current through the LED is proportional to the duty cycle of the PWM signal. For example, if the output PB5 (pin 13) of microcontroller 436 (U1) is driven with a 50% duty cycle, this means that output PB5 is in the high state 50% of the time, and the low state for other 50% of the time. In this example, the series-connected LED pair formed by LEDs 458 and 460 (LED 2 and LED 4) will conduct current Imax1 50% of the time, and will be in the off state for the other 50% of the time. Thus in this case, the average current conducted by series connected LED pair 458/460 (LED 2 and LED 4) will be one-half of Imax1. Those skilled in the art can appreciate that virtually any pulse-width-modulated (PWM) duty cycle between 0% and 100% may be used. If the PWM frequency is higher than that which can be perceived by the human eye, then the LED pair 458/460 (LED 2 and LED 4) will appear to be illuminated in a constant fashion, even though they are in fact being cycled on and off by output PB5 of microcontroller 436.
Within a portion of their operating range, light emitting diodes will emit light having an intensity that is proportional to the average current that is driven through them. Since the average current through each LED pair is controlled by the PWM duty cycle as explained above, then the luminous intensity of each LED is in fact proportional to the PWM duty cycle used to drive them, as illustrated in
Those skilled in the art will appreciate that, while the preferred embodiment of the present invention uses two or more distinct color strings of LEDs for maximum control, it is not necessary that each LED string be limited to LEDs of a single color. A particular LED string may be designed to have two or more different-colored LEDs arranged in series within the string, or to have two or more different colored LEDs arranged in parallel, or in a series-parallel combination. Likewise, while the preferred embodiments include two or three separate strings of LEDs, it is also possible to use a smaller or larger number of LED strings.
Those skilled in the art will now appreciate that a simple and inexpensive LED-based trans-illumination device has been described for assisting health care providers in locating suitable veins for a wider variety of patients. The disclosed device uses light from the visible spectrum for producing an image that can be directly viewed by a user without the need for special detection equipment or display devices. The disclosed trans-illumination device is highly portable, easy to use, and easy to position against a patient's body. Moreover, the profile of the light head, and the various illumination modes, permit the device to function well even with patients having darker skin tones, or wherein fatty tissues surround features of interest. The profile of the light head allows a greater portion of the vein to be illuminated, and yet avoids any significant interference with needle placement. In addition, the ability to use the same base unit with a number of light heads allows medical personnel to select a light head best suited to a particular patient, while minimizing the number of different types of tissue imaging devices on hand. Finally, the disclosed device lends itself to sterilization between uses, although the use of inexpensive, interchangeable light heads may actually result in such light heads being considered disposable after each single-use. The light head 100, and the handheld unit 250 (depicted in
Now referring to
As shown in
Support member 514 has an inner (or “upper”) surface 516 and an opposing outer (or “lower”) surface 518 (see
In addition, support member 514 terminates in an upwardly-directed flange 526. Flange 526 provides structural support for an electrical connector mounted to the printed circuit board. Flange 526 has a central hole 528 formed therein for receiving the cylindrical barrel of the aforementioned electrical connector. In addition, a pair of attachment depressions 504 and 511 (see
In
Turning now to
Disposable base 502 is preferably opaque, but includes base apertures formed therein aligned with apertures 521, 523, and 524 of support member 514. In turn, these base apertures formed in disposable base 502 are filled with lens elements 503, 508, and 506. Lens elements 503, 508 and 506 seal the base apertures while directing light emitted by the first, second, and third banks of LEDs into the patient's skin.
In use, disposable base 502 is detachably coupled to lighting head assembly 500 by first engaging the detents of tabs 546 and 548 over retaining tabs 525 and 527, respectively, of support member 514. Then, quick release tabs 505 and 507 are slid upwardly over flange 526 until detents on tabs 505 and 507 engage depressions 504 and 511 on flange 526. While not shown, lighting head assembly 500 may also include an upper cover to shield the upper surface of printed circuit board 530 from contamination. The assembled device is then connected by an electrical cable to the electronic controller within the base unit, and can then be used to identify veins or other tissues in a patient. Following such usage, disposable base 502 is easily and quickly detached from lighting head assembly 500 by pulling outward on quick release tabs 505 and 507. Disposable base 502 is then thrown away, and a fresh disposable base is secured over lighting head assembly 500 for the next patient.
While the present invention has been described with respect to preferred embodiments for illuminating veins below the surface of the skin, those skilled in the art will appreciate that the present invention may be applied by medical personnel to better visualize other subcutaneous tissues within the body of a patient.
While the present invention has been described with respect to preferred embodiments thereof, such description is for illustrative purposes only, and is not to be construed as limiting the scope of the invention. Various modifications and changes may be made to the described embodiments by those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims.
This application claims the benefit of the earlier filing date of U.S. provisional patent application No. 61/405,543, entitled “Medical Imaging Device”, filed on Oct. 21, 2010, by the same inventors named herein, pursuant to 35 USC §119(e). This application also claims the benefit of the earlier filing date of U.S. provisional patent application No. 61/405,532, entitled “Pediatric Tissue Illuminator”, filed on Oct. 21, 2010, by the same inventors named herein, pursuant to 35 USC §119(e).
Number | Date | Country | |
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61405543 | Oct 2010 | US | |
61405532 | Oct 2010 | US |