Pulsed liquid jet dissector using holmium:YAG laser -: a novel neurosurgical device for brain incision without impairing vessels

Background. Neurosurgery has long required a method for dissecting brain tissue without damaging principal vessels and adjacent tissue, so as to prevent neurological complications after operation. In this study we constructed a prototype of such a device and used it in an attempt to resect beagle brain cortex. Method. The prototype device consisted of an optical fibre, a Y adaptor, and a nozzle whose internal exit diameter was 100 mum. Cold physiological saline (4 degreesC) was supplied to it at a rate of 40 ml/h. Pulsed liquid jets were ejected from the nozzle by a pulsed Holmium:YAG) (Ho:YAG) laser at an irradiation energy of 300 mJ/pulse. The profile of the liquid jet was observed with a high-speed camera while changing the distance between the optical fibre end and nozzle exit (equivalent to the standoff distance). With this device (3 Hz operation), brain dissection of anaesthetized beagles was attempted while measuring the local temperature of the target. A histological study of the incised parts was also performed. Findings. When the standoff distance was 24 mm, the liquid jet was emitted straight from the nozzle at a maximum initial velocity of 50 m/s. The brain parenchyma was cut with this device while preserving vessels larger than 200 mum in diameter and keeping the operative field clear. The local temperature rose to no more than 41 degreesC, below the functional heat damage threshold of brain tissue. Histological findings showed no signs of thermal tissue damage around the dissected margin. Interpretation. The Ho:YAG laser-induced liquid jet dissector can be applied to neurosurgery after incorporating some minor improvements.