A new system for a combined laser and ultrasound application in neurosurgery

A new combined Laser and Ultrasound Surgical Therapy (LUST) device suitable for endoscopical coagulation and tissue fragmentation has been developed at the LMTB. The new feature is the simultaneous transmission of laser radiation and ultrasound via flexible silica glass fibers. The ultrasound tissue interaction is based on the well-known CUSA-technology which enables the surgeon to cut various types of tissue with different degrees of effectiveness. Application fields are in oncology, neurosurgery and angioplasty. The laser radiation can be used, for example, for tissue coagulation purposes. With a fiber based LUST-system working at a frequency of 30 kHz, a displacement of 100 microns could be attained at the distal end. (The usual standard CUSA displacement is 10-350 microns.) During in vitro experiments the following tissue fragmentation rates could be achieved: brain tissue 50 mg sec-1, liver 4.5 mg sec-1 and kidney 4 mg sec-1 (displacement of the tip 60 microns; phi 1.3 mm; suction setting: 5 W). Laser radiation up to 25 W was sufficient to coagulate soft tissue. This technology offers new possibilities in minimal invasive surgery. The flexible opto-acoustic waveguide (phi 400-1700 microns) can be bent making areas accessible that were previously inaccessible. Without changing the instrumentation the surgeon can use the laser radiation for tissue coagulation or cutting and the ultrasound for tissue fragmentation and tissue reduction.