1. Field of the Invention
The present invention relates to a medical device for use in taking blood samples. More particularly, the present invention is directed to a laser lancet for use in obtaining precise blood samples from patients.
2. Description of the Related Art
The taking of blood samples is a necessary part of the process of diagnosing and controlling disease. Traditionally, blood samples are obtained by puncturing the skin of a patient's finger with a sharp object such as a needle or pointed blade. Larger samples required the use of a syringe needle which would be inserted into a vein. The needles and pointed blades include exposed points which are a danger to health care workers and produce a significant fear and apprehension in patients who anticipate a painful experience. Once used, the blood infected needles and pointed blades must be discarded under carefully controlled conditions. Moreover, the use of disposable needles and pointed blades requires medical providers to keep a large inventory at all times. The result is an expensive and potentially dangerous process for obtaining blood samples from patients.
Recently, lasers commonly known as laser lancets, have been used as a substitute to a needle or pointed blade for obtaining blood samples from patients. A laser lancet can be used to puncture the surface of the skin causing a rupture of subcutaneous capillaries and the expression of blood or can puncture a hole through the skin and a vein for larger blood samples. The blood can then be collected for analysis. These laser lancets contain complex circuitry and control systems to vary the power, duration, pulse rate, and size of the laser pulses. A small blood sample from the finger can be taken by a single short high power pulse which vaporizes the skin tissue and severs many small blood vessels. This results in a blood sample of a few drops. To collect a larger blood sample, the laser must be able to deliver a greater power pulse or the same power pulse repeated over a short period of time to puncture the skin and an underlying vein. After puncturing the vein a larger volume of blood can be collected. Varying the power, duration, and pulse rate of a laser pulse requires complex circuitry and control systems which greatly increases the cost of the laser lancet and the training needed to operate the laser. This results in increased cost to the patient.
Further, many of the prior art laser lancets are designed to puncture the skin of a finger or a vein in an arm of an adult patient. Infant patients require the puncture to have a larger surface area but less depth than adults to collect the same amount of blood. An infant's capillaries are close to the skin and the depth can, therefore, be reduced. This requires the blood taker to be skilled in varying the size of the puncture depending on the age of the patient. Additionally, even though a laser pulse remains the same, the depth of the puncture will vary depending on the location of the puncture. The skin on an arm is soft and will vaporize easily causing a deeper puncture. The skin of a finger, however, may have callouses or is generally harder, so it is more difficult to vaporize with the laser pulse. The result is more complex circuitry and control systems and, consequently, additional training of personnel. Again, there is increased cost to the patient.
It is well-known in the industry to use a laser system for surface reprofiling in which a mask is disposed between the laser and the target. The mask provides a predefined profile of resistance to laser radiation erosion by selectively absorbing some of the laser radiation while permitting the remainder to be transmitted to the target in accordance with the mask profile. The mask, however, only controls the amount of energy which is incident on the target and does not control the expanse (surface area and depth) of the affected skin.
It is also known to modify the intensity distribution of a laser beam by attaching a rotatable mask which spins and allows only a portion of the laser beam to pass to the target surface. The intensity modifying mask, however, requires a means to rotate the mask and must be structurally connected so it can be rotated. This, of course, increases the complexity and cost of the system. Moreover, the intensity modifying mask does not control the expanse of the incision.
It is therefore desirable to provide a laser lancet assembly which can deliver a pre-determined precisely controlled laser pulse.