In medical surgery, application of laser is increasing rapidly. At present Ho:YAG laser-based surgical instrument is the clinical standard in Urology. The operating wavelength of Thulium fiber laser (TFL) in the range of 1.9-2.05 µm makes useful for specific surgery because of closely matching wavelength with cellular water absorption. Technologically TFL is superior to Ho:YAG laser operating at 2.1 µm.

Fiber Optics & Photonics Division at CSIR-CGCRI took up an ambitious task to establish state-of-the-art facility and initiate research on TFL targeting applications in medical and strategic sectors. A diode-pumped all-fiber CW/QCW Thulium laser for operating wavelength of 1.94 µm has been developed to deliver CW power in the range of 30-150 W with efficient thermal management.

The 30 W CW/QCW air-cooled laser design has been patented (Indian Patent application no. IN 201911001722) and the technology has been transferred to (i) Bharat Electronics Ltd (BEL) Bangalore for their internal requirement and to (ii) Biorad Medisys Pvt. Ltd., Pune for medical application.

Followed by the ToT, the industry is now progressing for the development of commercial clinical product. A MoU has been signed to upgrade the CSIR-CGCRI prototype to commercial product for urinary stone fragmentation. Presently, the industry is progressing for Pilot scale system manufacturing, testing, clinical validation and certification where CSIR-CGCRI is involved in laser optical engine design and development, product specification for different mode of treatment and up gradation of laser specification. The 1st integrated module has also been demonstrated at hospital and the system modification is progressing accordingly.

The designed TFL has the capability to operate in CW, long pulse as well as short pulse mode providing more versatility for applications in lithotripsy and soft tissue ablation. The excellent beam quality inherent to a fiber laser allows use of smaller diameter delivery fiber which provides better irrigation, improved vision and workspace within the instrument. The wall plug efficiency of such TFL is 17% compared to that of 1-2% for clinically used Ho:YAG laser. Ex-vivo preclinical investigation shows that the designed TFL is consistent to breaking up the urinary stone in a controlled manner with almost uniform fragments < 1.6 mm at fragmentation rate 0.8±0.4 mg/s with minimum retropulsion which can reduce the overall procedural time and potential for clinical use to perform lithotripsy safely and more efficiently with less complications. For India, the USP of that CSIR-CGCRI technology based laser surgical system is i) Minimum optical component architecture – affordable price ii) Compact system with safety features and less maintenance - travel friendly and usable in rural camp iii) Less maintenance - low running cost iv) Energy/Average power setting according to the wide range of stone composition and hardness varies all over India as well as different country.

As per the feedback from several doctors, there is a demand of higher laser Power for soft tissue surgery with high efficiency and less carbonization. High-end surgical devise with higher laser power is under development for lithotripsy of harder stone composition and large soft tissue ablation.

Atasi Pal
Principal Scientist, Fiber Optics & Photonics Division
CSIR-CGCRI