There are many advantages of using lasers and optical fibers in biomedical and clinical applications. First of all, this procedure is non or minimally invasive. The damage risk of the neighbouring tissues is quite low since the laser energy is specifically absorbed by the target tissue. The laser operations are highly controlled thanks to focusing the laser energy with micron precision. The laser parameters such as power, frequency, number of pulses and energy are adjustable. The wavelength of the laser can be selected according to target chromophore absorption such as water, hemoglobin. Laser energy can be transmited with different beam shapes by manipulating the fiber tip geometry. In our group studies, we are focused on IR-range wavelength laser systems operating both continuous wave (cw) and modulated modes for medical applications. Our motivation is to develop medical lasers which are used in mainly endovenous laser ablation (EVLA). Veneous insufficiency in the lower-extremity is a widespread medical situation, in fact 25% of women and 15% of men suffer from this disease in the USA . The varicose veins are a effected or worsened by some conditions, such as pregnancy, aging, standing and sitting for a long time. The primary symptoms cannot be noticed easily by patients, thus, the disease may progress and cause worse symptoms such as night cramps, pain and fatigue . If the varicose vein is not treated before progression, approximately 50% of patients may ultimately suffer from chronic venous insufficiency . The most probable cause of distinctive varicose vein is great saphenous vein (GSV) reflux and even stripping and surgical ligation has been the most certain solution, it causes perioperative morbidity . Since it is identied that the main reason of the varicose vein is the GSV reflux, eliminating of GSV should be the solution. As an alternative to surgical operation, the laser energy was firstly used in an endoluminal operationvby Bone in 1999 . This study opened a door for varicose vein treatment, and a procedure had been developed for treatment of GSV by using 810nm laser diode The delivery of laser energy into blood vessel lumen has been approved by US Food and Drug Administration in 2002 . There are also other options for treatment of GSV reflux, such as, surgery and RF-ablation. Endovenous laser ablation seems to provide important benefits that are avoidance of general anesthesia and lower rates of complication. Our group developed two medical laser systems. The first one is operating at 980nm with cw and modulated modes. The second one is a dual wavelength laser system operating at both 980nm and 1470nm with cw and modulated modes.
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980nm Medical Laser Sytem – Version 1
980nm wavelegth is specific to hemoglobin. This wavelength is used in various biomedical operations such as venous diseases, hemoroid-fistulas, urological tumor, uterine tumor. The first version of medical laser is designed and developed. Combining 980nm laser system and fiber optic probes having different beam shapes, many medical operations can be realized. The design of the medical laser system operating at 980nm wavelength is shown in Fig.1.
Fig.1: Design of medical laser system operating at 980nm.
The laser is modulated by electronic control unit. The duration and interval are adjustable parameters and they can be selected by surgeon. The electronic control unit and the laser diode are cooled by air-cooling system. The package of the medical laser system operating at 980nm is represented in Fig.2.
Fig.2: Medical laser system operating at 980nm
The operation parameters are represented in the Table 1.
Table1: Operation parameters of the medical laser system.
Dual Wavelength Medical Laser System Operating at 980nm and 1470nm – Version 2
1470nm wavelength is prefered since the absorption of the water in this wavelength is considerably high. Thus, it minimizes the postoperative complications such as pain and bruise. Lasers with 980 nm and 1470 nm can be used for different applications in medicine since they target various chromophores. These are gynecology, dermatology and general surgery. The design of the dual wavelength medical laser system is represented in Fig.4.
Fig.4: Design of dual wavelength medical laser system operating at 980nm and 1470nm.
The laser energy dose which is applied to the desired body part can be controlled by electronic unit by increasing or decreasing the current feeding the laser diodes. The wavelength can be changed by the button which is placed on the casing. The laser beam is also modulated by electronic unit. Duration, interval, power and number of pulses can be selected easily from the touch screen (user interface). There is an emergency button on the top of the casing. This button provides a sudden cancellation of the operation in case of any emergency situation. All the system design and parameters are proper for the medical laser system requirements. The latest version of the dual wavelength medical laser system developed by our group is shown in Fig.5. It is compact, user friendly and promissing many medical operations since it has two operating wavelengths which are specific to different chromophores.
Fig.5: Dual wavelength medical laser system operating at 980nm and 1470nm.
The operation parameters and their operating ranges are represented in Table 2.
Table 2: Operation parameters of the dual wavelength medical laser system.
The modulation of the laser system was tested and measured by the oscilloscope. The duration and interval values are chosen from the user interface which is a touch screen. There are some of the examples given in the Fig.6. The duration and interval values satisfy the medical operation requirements.
Fig.6: Oscilloscope images of the modulated laser for (a) duration 100m/s, interval 100ms, (b) duration 200ms, interval 100ms, and (c) duration 30s and interval 30s.
The operating wavelengths of the dual wavelength medical laser system are measured by optical spectrum analyzer. The spectrum of the both wavelength are shown in Fig.7. The laser system is cooled by feedback supported air-cooling system. The wavelength shift in the 980nm laser diode is minimized and eliminated for 1470nm laser diode. It is important to keep the wavelength constant as possible in order not to disturb the medical operation requirements. The wavelength of the both diodes are developed properly for the medical operation requirements.
Fig.7: Optical spectrum of the dual wavelength medical laser system operating at 980nm and 1470nm.
This project is supported by TÜBİTAK under the 1501 program, project number 3140846.