Surgery – Instruments – Light application
Reexamination Certificate
2001-11-08
2004-07-13
Shay, David M. (Department: 3739)
Surgery
Instruments
Light application
C606S011000, C606S013000, C606S015000, C372S025000, C372S029020, C372S068000, C372S070000, C372S071000
Reexamination Certificate
active
06761713
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of co-pending German Patent Application No. 100 55 179 entitled “Laservorrichtung, insbesondere für chirurgische Anwendungen”, filed on Nov. 8, 2000.
FIELD OF THE INVENTION
The present invention generally relates to a laser unit. More particularly, the present invention relates to a medical laser unit to be used in the field of surgery. For medical applications and especially surgical applications, interaction between the laser radiation and the tissue is required. In surgical applications, it is desired to make it possible to cut soft tissue supplied with blood and also soft tissue not supplied with blood with the laser radiation only with a thin coagulation edge being located about the cutting region, but with sufficient hemostasis in any case. On the other hand, it is desired to be capable of coagulating soft tissue in a specific way and to fragment, erode or remove hard body materials by pulsed laser radiation of short time high power laser pulses. For example, the relevant hard materials may be bones, urinary concretion and gall stones. At the same time, it is desired to make the handling of the laser radiation as simple and safe as possible. It is ideal not to transmit the laser radiation as a free beam, but rather through a protected articulated mirror arm or an optical wave guide which delivers the laser radiation to the respective surgical site.
BACKGROUND OF THE INVENTION
Laser units which serve to produce either continuous laser radiation or pulsed laser radiation are known. A known laser for producing continuous laser radiation is produced and sold by the assignee of this application. It includes a laser rod made of laser material as a laser body. To excite the laser material, there is a plurality of laser diodes as pump light sources the pump light of which is introduced into the laser rod at its longitudinal end. The pump light is kept in the laser rod by index guidance, meaning total reflection, until it will be absorbed by the laser material over an absorption length of approximately the same size as twice the length of the laser rod. Cooling of the laser rod over its entire circumference with an enclosed cooling coat results in an rotational symmetric temperature distribution around the axis of the laser rod. Pump light which is not absorbed after the first pass through the laser material returns at the far end of the laser rod at an optical coating being highly reflective for the pump light wave length into the laser material for a second pass. The continuous laser radiation of the known laser unit has a wavelength in the region of 2 &mgr;m and it is suitable to cut and also just to coagulate soft tissue and to achieve excellent hemostasis in well circulated tissues like prostate, kidney and liver. Cutting power or cutting efficiency is good, and there are a good cutting results which have a thin coagulation edge which typically is less than approximately 1 mm. However, the continuous laser radiation of the known laser unit is not suitable to erode and to fragment hard materials.
Laser units for producing continuous laser radiation with laser diodes as pump light sources are also known in embodiments of known laser units including transversal pump geometries.
Furthermore, laser units in which a laser body made of laser material, for example also a laser rod, is excited by a flash lamp as pump light source in a transversal pump geometry are also known. The pump light power of a flash pump may be increased in a way that the pulse-like laser radiation is realized at pulse peak power in the multi Kilowatts region and the pulse energy of the single pulses occurs in the multi Joule region. However, the pulse repetition rate is limited by the decreasing laser efficiency with increasing laser material temperature which typically occurs under flash lamp pumping. A longitudinal pump geometry which would be interesting for thermal reasons is difficult to be realized with one flash lamp since the wavelength of the pump light for this purpose has to be adjusted to approach an energy level shortly above the transition to be excited to attain population inversion at the laser transition and the required absorption length in the laser rod. Such fine tuning is not possible with flash lamps which rather radiate in a wide-band way. Furthermore, geometric radiation characteristics of the flash lamp oppose to the introduction of the delivered pump light into the laser rod. The pulsed laser radiation of the known laser unit including the flash lamp as pump light source allows for eroding and fragmenting hard materials in a good way. The single pulses initiate shockwaves which destruct the respective hard material in a controlled manner. In case of pulsed laser radiation of the known pulsed laser, cutting power and cutting quality is not good in soft tissue. In case of high rates of pulses, cutting power and cutting quality is increased. However, the cut edges are strongly fringed due to the way of pulsing. Coagulation only of soft tissue is less efficient with pulsed laser radiation of which the repetition rate does not exceed 50 Hz in the known laser unit including a flash lamp as a pump light source compared to coagulation with continuous laser radiation of the other known continuous wave laser unit.
SUMMARY OF THE INVENTION
The present invention relates to a medical laser unit for surgical applications. The medical laser unit includes at least one laser body being made of laser material. A first type of a pump light source is designed and arranged to continuously excite the laser material and to generate continuous laser radiation. A second type of a pump light source is designed and arranged to excite the laser material by pulses and to generate pulsed laser radiation. A transmitting unit is designed and arranged to transmit the continuous laser radiation and the pulsed laser radiation to a surgical application site. More particularly, the present invention relates to a medical laser unit which has two modes of operation, a first mode for cutting and a second mode for fragmenting. The medical laser unit for surgical applications includes at least one laser rod being made of laser material, at least one laser diode being designed and arranged to continuously excite the laser material and to generate continuous laser radiation and at least one flash lamp being designed and arranged to excite the laser material by pulses and to generate pulsed laser radiation. The laser diode and the flash lamp are designed and arranged to excite the laser material of the laser rod to generate continuous laser radiation in a first mode of operation in which the laser diode excites the laser material above a laser threshold. In a second mode of operation, the laser diode and the flash lamp are designed and arranged to simultaneously excite the laser material of the laser rod to generate pulsed laser radiation, the laser diode exciting the laser material below the laser threshold and the flash lamp additionally exciting the laser material above the laser threshold. The unit further includes at least one transmitting unit being designed and arranged to transmit the continuous laser radiation and the pulsed laser radiation to a surgical application site.
The novel laser unit fulfills all requirements of surgical applications, meaning it is suitable to cut soft tissue with a thin coagulation edge and excellent hemostasis of well circulated tissue, to purely coagulate soft tissue as well as to erode and to fragment hard materials.
The novel laser unit leaves the known concept of fulfilling all requirements of surgical applications with one single way of generating laser radiation. Consequently, the novel medical laser unit includes both elements to produce or generate continuous laser radiation as well as such ones to produce pulsed laser radiation of high pulse peak power at a short pulse duration. The generation of continuous laser radiation is to be understood as either real so called continuous wave laser radiation or as q
Lisa Laser Products OHG Fuhrberg & Teichmann
Shay David M.
Thomas Kayden Horstemeyer & Risley
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