T. Yonezawa

Percutaneous Intradiscal Laser Discectomy

Recently percutaneous discectomy, such as chemonucleolysis with chymopapain [1] and percutaneous nucleotomy with punch [2] or nucleotome, has been developed extensively in Europe and America to provide an alternative to surgery in the treatment of lumbar disc herniation. But percutaneous nucleotomy, as mentioned above, has not been used in our daily therapy because of the limitation of indication, complications and technical problems. The experimental study of percutaneous intradiscal laser discectomy (PILD) has been tried to provide an alternative to percutaneous discectomies which are currently applied. The protocol of our study was composed of five parts. The five parts were as follows: 1) The optimum condition was obtained to vaporizes nucleus pulposus with Nd: YAG laser using sacrificed rabbit and goat lumbar discs. 2) The intradiscal changes in the time course were observed by microscopic evaluation using rabbit lumbar discs. 3) The relationship between intradiscal pressure (IDP) and vertical load in the time course were compared between irradiated discs, normal discs and control discs which were operated by curette. 4) Fibers and needles were developed to diminish heat damage. 5) Preliminary in vivo trial of PILD was performed in anesthetized young goats under X-ray guidance prior to the application for human cases.

percutaneous laser nucleotomy for lumbar disc herniation: Preliminary report of early results and MRI findings

Early therapeutic results and magnetic resonance imaging (MRI) findings were serially evaluated for 34 consecutive patients with lumbar disc herniation treated by percutaneous laser nucleotomy (PLN), a minimally invasive technique for reducing intradiscal pressure, in which a neodymium: yttrium-aluminum-garnet (Nd:YAG) laser was used. At the mean follow up 13.8 months after PLN, successful results were obtained in 20 patients (58.8%). No serious complications were encountered. In patients with contained discherniation, the improvement rate was significantly higher than that in patients with non-contained dise herniation (P<0.05). Sagittal magnetic resonance (MR) images obtained during the time sequence after PLN demonstrated a relationship between MR signal intensity patterns and clinical recovery. No measurable change in the size of the herniated mass was confirmed on axial images immediately after PLN, while, in contrast, reduced signal intensity inside the disc was observed in 12 of 20 patients with successful results in the early postoperative period. Postoperative T2-weighted MRI can be used to predict the prognosis of patients treated with PLN.

LASER ANGIOPLASTY SYSTEM USING CONTACT CERAMIC TIP: STABILIZATION OF POWER AND DEVELOPMENT OF ENDOSCOPEPIC SYSTEM

LASER ANGIOPLASTY SYSTEM USING CONTACT CERAMIC TIP: STABILIZATION OF POWER AND DEVELOPMENT OF ENDOSCOPIC SYSTEM Y. Abe, K. Imanishi, T. Yonezawa, T. Chinzei *, I. Sogawa *, M. Suzukawa, K. Mabuchi, K. Imachi, A. Kouno, T. Ono, T. Tago *, K. Atsumi and I. Fujimasa Institute of Medical Electronics, Faculty of Medicine, University of Tokyo. *RCAST We have been developing laser angioplasty system using contact ceramic tip. In order to stabilize the required power for plaque ablation, ceramic coating tip was designed and developed by implanting metal at the point of the surface of ceramic tip, and the special endoscope with 7F size was designed and developed from the points of percutaneous approach and ceramic tip usage. The laser probe was designed to be separated at the part of laser fiber and able to be inserted from the top of the endoscope. The special endoscope and laser probe with ceramic coating tip were very useful for atheroma ablation inside the aorta of atherosclerotic rabbits under the visual field. The required power for plaque ablation with ceramic coating tip was 515W, and was able to be stabilized.

Comparative Study on Excimer, CO2 and Nd: YAG Laser for Biological Tissue Cutting

The mechanism of biological tissue cutting was investigated using excimer laser compared with CO2 and ND-YAG lasers. Tissue cutting by excimer laser is different from others. Tissues are cut sharply, and bleeding from tissue can not be coagurated by using excimer laser. No or a minimal thermal effect can be observed from the postoperative tissues. Many hypotheses have been published the mechanism of tissue cutting by excimer laser; thermal effect, photochemical effect, photon effect, plasma effect and others. From thermographic analysis and histological studies, we confirmed that biological tissues are destroyed by cutting organelle, especially mitochondria. Cells and tissue blow out following to the organelle explosion. It is true that the generation of heat causes and sometimes makes carbonated layer. But the generation of heat is the result following to tissue explosion, The energy balance, between generated and lost heat, makes defferences of tissue effect.