Laser Tip Research Articles

Laser plasty combined with mucosal suture technique for the treatment of child vocal cord adhesion case

A pediatric case of vocal cord adhesion treated by laser plasty combined with mucosal suture technique was reported. A 3 year and 7 month old girl was referred to our clnic with prolonged stridor for more than 2 years. Fiberoptic observations revealed a limitation of the opening of the glottis during inspiration and a tentative diagnosis of bilateral laryngeal paralysis was made. However, microlaryngoscopy performed after tracheostomy under general anesthesia revealed an adhesion of both vocal cords for the anterior 4/5. The adhesion was separated with C02 laser, and the right vocal cord was laterally fixed according to the Ejnell method. One month after the surgery, however, the adhesion recurred. Therefore, under microlaryngoscopy, the ashesion was separated again and the cut end of the right vocal cord was thinned using a laterally beamed laser tip to leave the upper and lower mucosal edges intact. Both mucosal edges were then sutured together to close the raw surface at the cut end by means of our mucosal suture technique reported elsewhere. The entire procedures were made with a supportive viewing of the surgical field using an angurated telescope attached to the operating table.

Photodynamic Therapy

Photodynamic Therapy

Ultrasound imaging of Nd:YAG laser-induced tissue coagulation in porcine livers.

Absorption of laser light energy induces denaturation of proteins and thermocoagulation of irradiated tissue. Recently, MRI-guided laser coagulation in combination with MR thermometry was reported as a treatment of liver tumours. In the present study ultrasonographic imaging was evaluated for its suitability in laser induced tissue thermocoagulation. Fresh porcine livers were used for ex vivo examinations. Placement of the laser catheter and tissue coagulation during laser light emission were online monitored by ultrasonography. Nd:YAG laser-induced tissue damage was evaluated by macroscopical and microscopical examinations of histological sections. During laser light emission a marked hyperdense signal enhancement was observed by ultrasonography which strongly correlated with the extent of macroscopic tissue damage. The size of laser-induced coagulation zone depended on both the power setting and total energy delivered. Carbonization of the tissue surrounding the laser tip is a limiting factor because of laser light absorption. However our data indicate that using appropriate laser energy and exposure time prevent carbonization although carbonization can not be visualized by ultrasonography. It is concluded from the present ex vivo studies that laser coagulation can be effectively performed under ultrasonographic guidance.

Laser-Scanning Probe Microscope Based Nanoprocessing of Electronics Materials

Recently, scanning probe microscope (SPM) has become a promising technique for nanofabrication. In this paper, we present a novel method of nano-fabrication, namely, nano-fabrication by atomic force microscope (AFM) tips under laser irradiation. The SPM was operated as an AFM. During imaging and nano-fabrication, the AFM is in constant force mode. The tip is fixed with the sample moving via a tube scanner. Nano-lithography software controls the scanner motion in x and y directions. The SPM has an open architecture allowing an external laser beam incident on the tip at an incident angle between 0 to 45°. A vertically-polarized Nd:YAG pulsed laser with a pulse duration of 7 ns was focused on the tip. An electrical shutter was introduced to switch the laser irradiation. Alignment between the laser beam and the tip was performed under a high-power charge coupled device (CCD) microscope. The kinetics of the nanostructure fabrication has been studied. Craters were created in air ambient under different laser pulse numbers, pulse energies and tip force. The feature size of the craters, which are in the nanometer scale, increases with the pulse number, pulse energy and the tip force. This technique has potential applications in nano-lithography and high-density data storage.

Photolysis using the dodick–ARC laser system for cataract surgery

Purpose To report the intraoperative and postoperative results of cataract surgery using a pulsed Q-switched neodymium:YAG (Nd:YAG) laser. Setting Eye Clinic, Kreiskrankenhaus Bad Hersfeld, Germany. Methods This prospective study involved 100 consecutive patients who had cataract surgery between October 1998 and May 1999. The patients were allocated to 3 groups based on the hardness of the nucleus using the LOCS III system: Group 1 (NO ≤ 2.9), 48 patients; Group 2 (NO 3.0 to 3.9), 46 patients; Group 3 (NO ≥ 4.0), 6 patients. Plasma was generated with a pulsed Q-switched Nd:YAG laser (ARC GmbH). A clear corneal incision of 1.25 mm provided access for the laser tip. An intraocular lens (CeeOn® Edge [Pharmacia & Upjohn] or AcrySof® [Alcon]) was implanted via a separate clear corneal incision. Intraoperative laser pulse rate and total energy were recorded. Preoperative and postoperative (2 days and 6 months) central cornea thickness was compared. Results In all cases, the cataract was removed within an acceptable time without converting to the conventional phacoemulsification technique. Mean total energy was 1.97 J ± 1.43 (SD) in Group 1, 3.37 ± 1.59 J in Group 2, and 7.70 ± 2.09 J in Group 3. No significant postoperative changes between preoperative and postoperative central pachymetry were seen in Groups 1 and 2; there was a 1.9% postoperative increase in central pachymetry in Group 3. This could be a consequence of the higher volume of intraoperative balanced salt solution and the prolonged procedure in this group. Six months postoperatively, there were no significant changes from the preoperative values. Conclusion Photolysis of the lens nucleus can be used safely and efficiently for nuclei with a hardness up to NO 3.9. The energy required for lens removal was 83% less than that required by phacoemulsification.

Ｙ字型ストッパー付き高拡散型チップを用いたびまん性肺気腫に対するＶｏｌｕｍｅ ｒｅｄｕｃｔｉｏｎ Ｓｕｒｇｅｒｙの一例

びまん性肺気腫に対し, 独自に考案したY字型ストッパー付き高拡散型チップをNd: YAGレーザーに用いたVolume reduction surgery (VRS) を行った症例を経験したので報告する.症例は75歳男性.内科的治療にても呼吸困難が増強し, 胸腔鏡下に二期的に両側のVRSを行った.気腫肺を自動縫合器で切除し, 切除困難部位の気腫肺に対するレーザー焼灼に, 初回左側手術では接触型ジャンボチップを, 右側手術では, Y字型ストッパー付き高拡散型チップを使用した.Y字型ストッパーは焼灼面との距離を約1cmで一定に保ちレーザーチップの先端に焼灼物等が付着しにくく, 術中操作の妨げにならない利点がある.高拡散型チップは1回の焼灼面積が従来のチップの約25倍と広く, 焼灼時間の短縮, 過焼灼による胸膜損傷の予防が可能である.接触型ジャンボチップと比べて, Y字型ストッパー付き高拡散型チップは, VRSの手術時間および術後胸腔ドレーンの留置期間の短縮に有用と思われる.

Internally cooled power laser for MR-guided interstitial laser-induced thermotherapy of liver lesions: initial clinical results.

To evaluate experimentally and clinically an internally cooled power laser system for percutaneous treatment of liver metastases, with magnetic resonance (MR) imaging guidance, to increase the volume of coagulative necrosis with single laser beam applications. The power laser system consisted of standard cannulation paraphernalia and a specially designed 7-F protective catheter for cooling the laser tip during treatment to avoid carbonization. A microdome laser beam applicator with a laser tip diameter of 0.95 mm kept the entire device as small as possible. After the unit was tested in 40 porcine livers, 532 laser beam applications (mean power, 27.5 W [range, 22.1-30.0 W]; mean application time, 19.8 minutes [range, 14-30 minutes]) were performed with MR guidance in 127 patients with 318 liver metastases. The safety of the procedure and the volume of induced necrosis were evaluated. In vitro, cuboid areas of coagulative necrosis with a mean greatest diameter of 4.3 cm +/- 0.5 (SD) were demonstrated after single applications. In vivo, MR thermometry allowed accurate demarcation of changes induced by heat, with a mean diameter of necrosis of 3.3 cm +/- 1.4. No carbonization or vaporization of tissue or damage of equipment occurred during treatment. This power laser system can increase the volume of laser-induced necrosis in liver metastases with a single application, thereby simplifying and accelerating the treatment of larger lesions.

Effects of pulsed Nd:YAG laser radiation on action potential conduction in nerve fibres inside teeth in vitro

Objective: This study aimed to simulate the effects of lasing dentine on pulpal nerve function. Methods: Rat spinal nerve roots were threaded through the prepared pulp canal of a 10 mm long tooth root segment which was mounted in a perspex bath. The protruding ends of the nerve were placed on platinum wire electrodes used to elicit and to record compound nerve action potentials (CAPs). Laser energy (average power = 0.3–3.0 W) was applied to the surface of the root segment using a pulsed Nd:YAG dental laser (dLase 300). Results: With the laser probe tip placed in static contact with the tooth surface, the nerve CAP was irreversibly abolished within 60 s of lasing at 1.0–3.0 W power. When the laser tip was moved to and fro over the root surface in a scanning mode, similar levels of radiation produced less marked effects. In the latter mode, CAP attenuation increased with increasing power and duration of lasing. After 60 s lasing at 0.3 W, the CAP size was 95% (± 5, S.D.) of the prelasing controls value; with 2.0 W the CAP was reduced to 54% (±33). The CAP recovered to 90% of control levels after lasing at powers up to 1.5 W, but reached only 72% of control values after lasing at 2.0 W power. Conclusions: Laser radiation applied to dentine caused a dose-dependent block of action potential conduction in nerve fibres in the underlying pulp chamber.

The modified excimer laser-assisted high-flow bypass operation

BACKGROUND To make high-flow revascularization of the brain possible, we developed an anastomosis technique that obviates temporary occlusion of the recipient artery. After connecting donor and recipient vessels, an Excimer laser catheter, introduced by way of an artificial side branch, creates a hole at the anastomosis site. Because of the inconsistency of the diameter of the hole produced by the closed laser tip, we developed and extensive modification of the procedure. METHODS A new type of laser tip was developed, consisting of two layers of 60 μ laser fibers in a circular configuration with a diameter of 2.2 mm. The laser tip is fixed to the vessel wall at the anastomosis site by suction with a high-vacuum suction device, and a round piece of recipient vessel wall inside the anastomosis is cut out. RESULTS Using the aorta as the recipient vessel in 30 rabbits, the modified technique was developed and, in the end, produced anastomoses with a high patency rate. In 25 patients, high-flow bypasses for different indications were made using a venous transplant interposed between the external carotid artery or one of its branches and the intracranial internal carotid artery, utilizing the modified Excimer laser technique for the intracranial anastomosis. Complications related to the new anastomosis technique were minimal, and a satisfactory patency rate was obtained. CONCLUSIONS The modified Excimer laser-assisted anastomosis technique makes high-flow revascularization of the brain a safe procedure, since temporary occlusion of the recipient proximal brain artery during the making of the anastomosis is obviated.

Measurement and modeling of thermal transients during Er:YAG laser irradiation of vitreous.

We investigated the transient thermal behavior of vitreous in order to understand the local thermal effects of laser output, and to predict the potential for unintentional injury during Er:YAG laser vitreoretinal surgery. The output of a free-running Er:YAG laser (2.94 microns, 300 microseconds FWHM) was delivered through a fiberoptic and applied to en bloc samples of bovine vitreous. Temperature was measured with ultrafine thermocouples. For 6 mJ pulse energy at 10 Hz, a temperature rise of 20 degrees C is measured 500 microns from the laser tip. The temperature rise is localized with a rapid fall-off greater than 1 mm from the energy source. At constant time-averaged laser power, the temperature profile is independent of repetition rate. Our finite-difference model generates results qualitatively consistent with measured data and allows for investigation of the influence of thermophysical parameters on heat transfer. Thermal injury to ocular structures should be limited during intravitreal application of Er:YAG laser energy.

Temperature control and light penetration in a feedback interstitial laser thermotherapy system.

The aim of this study was to describe the performance of a closed loop interstitial laser thermotherapy system in processed liver and to demonstrate its suitability for treating a vascularized tumour in vivo. The thermotherapy system consisted of an Nd: YAG laser and a temperature feedback circuit including an automatic thermometry system and thermistor probes. Experiments in processed liver were performed with a sapphire probe and temperature control at a distance of 10 mm. In most experiments at 1-2 W, and in half of the experiments at 3 W, there was no carbonization, a moderate change in the light penetration and excellent control of the temperature. In experiments with output powers of 4-5 W there was carbonization with rapid deterioration of light penetration and impaired control of the temperature. Carbonization affected the distribution of temperatures, which were lower below, and higher above, the laser tip in experiments with carbonization as compared to experiments without carbonization. Treatment of an adenocarcinoma implanted into rat liver was performed at 2 W with a bare fibre and without blood inflow occlusion. The feedback thermistor probe was placed 3 mm outside the margin of the tumour (largest diameter 9.5 +/- 0.3 mm (mean +/- SEM)). Temperature control and light penetration characteristics were similar to those found in vitro. No tumour could be demonstrated at sacrifice 6 days later. It is concluded that a closed loop feedback system can produce stable and reproducible local hyperthermia, that it performs better when carbonization is avoided and light penetration is preserved and that it has a great potential for interstitial thermotherapy of malignant tumours.

Transmission of Nd: YAG Laser through Human Dentin

Transmission of Nd: YAG laser through human dentin, whose thickness was stepwise decreased, was measured. Four human molars stored in saline solution were used. Dentin specimens with the thickness of approximate 1mm were created by cutting the teeth crossectionally using a diamond disc, followed by being polished by #600 silocone carbide paper and a whetstone. Average dentin thickness (DTh) of each specimen was calculated from five measurements each using a micrometer. Nd: YAG laser equipment used was Dent Lase DCL 8 (S.L.T Japan). An experimental laser tip made of quartz and an experimental gold-plated specimen holder having a central hole were employed. The irradiation conditions of Nd: YAG laser were normal pulse, 170mJ, 20pps and 2-second duration.Three measurements of the intensity of transmitted laser light (T-light) through dentin of approximately 1mm thickness were performed for each specimen by a power monitor (Ophir Optics Ltd). And the power monitor was transferred 2mm perpendicularly from the center of laser light (C-L). And then the measurement of the intensity of scattered laser light (S-light) was trebled. And then the power monitor was further transferred 4, 6, 8, 10 and 12mm from C-L and the measurement of the intensity of S-light was trebled at each displacement from C-L.Then DTh was stepwise decreased with the interval of 100μm, and T-light and S-light was repeatedly measured in the same manner described above.Relationship between DTh and T-light or S-light, and the relationship between the distance from C-L and T-light or S-light were analyzed by regression analysis.The following results were obtained;1. T-light was found to decrease with increasing the thickness of dentin and an exponential relationship was found between DTh and T-light.2. An exponential relationship between DTh and S-light was found when the distance between C-L was within 2mm, but no significant relationship was found if the distance from C-L exceeded 4mm.3. S-light was found to decrease with increasing the distance between C-L and a linear relationship was found between the distance from C-L and S-Light irrespective of DTh.(J. Jpn. Soc. Laser Dent. 7: 37-45, 1996 Reprints request to Dr. Zennyu)

MR imaging-guided laser-induced thermotherapy

SummaryInterstitial laser-induced thermotherapy (LITT) is a recently developed, minimally invasive technique for local tumour destruction within solid organs. The purpose of this study was to evaluate the potential of MR-guided laser-induced thermotherapy (LITT) for the treatment of recurrent head and neck and liver tumours in a prospective study. In the head and neck study 12 patients with recurrent head and neck tumours were treated using MR-con-trolled laser-induced thermotherapy. In the liver study 76 patients with in total 171 histologically-proven liver metastases of colorectal carcinoma, oesopha-geal, gastric, pharyngeal, testicular and Pancoast tumours were treated with LITT. A total of 527 applications were performed. All procedures were tolerated under local anaesthesia with no clinically relevant side effects. MR thermome-try clearly demonstrated an area of signal loss with a radius of up to 15 mm in the vicinity of the laser tip. Dynamic gadolinium-enhanced MRI is suitable for early and late f...

MR-gesteuerte laserinduzierte Thermotherapie bei Tumoren in der Kopf-Hals-Region: Erste klinische Ergebnisse

To analyse the value of MR-guided laser-induced thermotherapy (LITT) for palliative treatment of recurrent tumours of the head and neck region. 8 patients with recurrent tumours of the head and neck region (squamous cell carcinomas n = 6, pleomorphic adenomas n = 2) underwent MR-controlled LITT. A 7 French laser applicator was inserted under local anaesthesia into the centre of the recurrent tumour. A Nd:YAG laser with a wavelength of 1064 nm was used. Therapy was monitored on-line using special MR thermosequences. Preinterventional contrast-enhanced MRI revealed a recurrent tumour of the head and neck region for all eight patients. All patients tolerated the procedures well under local anaesthesia, with no clinically relevant side effects. The MR thermosequences depicted up to 15 mm diameter areas of less signal near the laser tip. Postinterventional contrast-enhanced MRI revealed hypovascularized areas due to the resulting coagulative necrosis. Coagulative necrosis of 4 cc to 28 cc occurred in all patients, and a reduction of clinical symptoms was achieved in five. The results obtained indicate that minimal invasive LITT can be a therapeutic alternative for palliative treatment of head and neck tumours.

Recurrent nasopharyngeal tumors: preliminary clinical results with interventional MR imaging--controlled laser-induced thermotherapy.

To evaluate magnetic resonance (MR) imaging-controlled laser-induced thermotherapy (LITT) in the treatment of recurrent head and neck tumors. Six patients with recurrent nasopharyngeal tumors (squamous cell carcinoma [n = 4], pleomorphic adenoma [n = 2]) underwent LITT with local anesthesia. A 7-F introducing sheath was inserted into the center of the tumor followed by a specially designed laser emitter. Therapy was monitored on-line with MR thermometry, and the amount of necrosis was estimated with dynamic and static contrast material-enhanced sequences. All procedures were well tolerated with use of local anesthesia, with no clinically relevant side effects. MR thermometry depicted up to 15-mm-diameter areas of less signal intensity near the laser tip. Coagulative necrosis was achieved in all patients (volume range, 4-28 cm3), and clinical symptoms were reduced in four. MR imaging-controlled LITT may be a safe, minimally invasive alternative in the treatment of recurrent head and neck tumors.

A comparative study of etching enamel by acid and laser

Acid etching is regarded as one of the main means of providing additional retention in aesthetic dentistry. Alternative methods of achieving bonding to tooth tissue which have been proposed include laser etching. Conflicting results on bond strength to enamel have been reported for laser etching. Here the tensile bond strength of composite resin to acid- and laser-etched enamel was measured and the topographical differences between the surfaces were evaluated using the scanning electron microscope. The laser used was a pulsed Nd-YAG laser at 10 pulses per second with a pulse length of 150μs, 80mJ pulse−1, 1.064μm wavelength. The results obtained indicate that the bond strength of laser-etched enamel was significantly lower than that of acid-etched enamel. In this study the difference may be attributable to the chromophore used. Variations in the rate of traverse of the laser tip across the surface did not appear to produce significant alterations in the bond strength.

Effects of a carbon dioxide laser on human root dentin

The effects of the Luxar LX-20 CO2 dental laser on resected apical root dentin were examined using stereomicroscopy and scanning electron microscopy. The surfaces of 2-mm-thick sections of dentin from freshly extracted human teeth were exposed to CO2 laser radiation. Fluences used ranged from 2.1 to 625.0 J/cm2. The effects of the laser energy on the dentin ranged from no visible effects, to charring, cracking, cratering, and glazing. The most dramatic effect was cracking. Cracking was evident on all specimens having any visible modification of the dentin. A prototype-curved laser tip was used and compared with a standard straight tip. The curved tip did not deliver laser energy to the dentin as efficiently as a straight tip. CO2 laser radiation did not consistently obliterate dentin tubules.

Laser Sphincterotomy and Ablation of the Prostate Using a Sapphire Chisel Contact Tip Firing Neodymium:Yag Laser

I report a modified technique for use of a contact laser for urological endoscopic surgery in spinal cord injury patients. Instead of the usual technique of passing the laser probe for surface vaporization, subsurface buttonholes were drilled with subsequent incision of the overlying tissue. As a result, creation of an adequate channel was expedited with excellent hemostasis. A total of 40 spinal cord injury patients (mean age 50.1 years, range 28 to 76) underwent transurethral surgery for bladder outlet obstruction using a sapphire contact laser tip. Of the patients 50% had undergone previous transurethral surgery and were not voiding well. Urodynamic studies demonstrated detrusor-sphincter dyssynergia in 37 patients (92.5%). Avoiding cystoure- throgram was done in 83% of the patients and showed vesicoureteral reflux in 17%. On cystoscopic examination 32.5% of the patients had an associated enlarged prostate, 32% stricture of the bulbous urethra and 20% bladder neck stenosis. Apart from transurethral sphincterotomy in these patients, ablation of the prostate, stricture and eradication of bladder neck stenosis, as indicated, were also done with the contact laser. Blood loss was approximately 25 to 50ml. per procedure except for 2 initial patients with a blood loss of 100 to 150ml. Approximately 3,500 to 8,900 joules accumulated energy were used for transurethral sphincterotomy and 11,000 to 37,000 joules for transurethral resection of the prostate. An indwelling Foley catheter was placed postoperatively for a mean of 3 days (range 1 to 8). All patients were followed for 6 to 23 months (mean 13.1). Four patients failed laser transurethral sphincterotomy: 1 due to inadequate initial incision and 3 who initially underwent laser transurethral incisions of the prostate and had persistent detrusor-sphincter dyssynergia (all had relief following laser transurethral sphincterotomy). All subsequent patients are voiding well with a wide open bladder neck and posterior urethra as shown on a voiding cystourethrogram.

Laser angioplasty: enough to make your blood boil!

Some of the effects on blood and contrast agents of a laser angioplasty device of the "hot tip" variety have been studied. This device liberates iodine from contrast agents both in the form of soluble free iodide and in the form of solid elemental iodine debris. Some of the solid iodine does not adhere to the probe but remains free and, in vivo, would be available to embolize distal vessels. The liberation of iodine occurs more readily with dimeric agents than with monomeric contrast agents regardless of whether they are ionic or non-ionic. Blood and blood/contrast agent mixtures exhibit local boiling in the vicinity of the hot tip laser probe. Blood so treated exhibits markedly accelerated clotting as indicated by measurements of whole blood clotting times. Untreated blood to which aliquots of blood treated as described above are added also exhibits accelerated clotting. The laser tip, operating in blood/iodine mixtures, becomes coated with a friable black/brown deposit which analysis reveals to be a mixture of carbon and iodine. Again, some of this particulate debris fails to adhere to the probe and is available as free embolic material. The possible practical clinical implications of these observations are discussed.

Complications of laparoscopic hysterectomy

To evaluate complications of laparoscopic hysterectomy.A retrospective analysis of complications was tabulated from hospital and office records. Forty-five consecutive patients had laparoscopic hysterectomies from November 1991 to November 1992. Complications were divided into operative, anesthetic, postoperative, nursing, and equipment. Each complication was subjectively graded from mild to severe.Complication rates by group were: operative 11%, anesthetic 7%, postoperative 16%, nursing 4%, and equipment 56%. Operative complications included one bladder perforation, two superficial epigastric artery perforations, and two subcutaneous emphysema cases. There were three anesthetic complications from fluid overload. Postoperative complications included four patients with periumbilical cellulitis. Three patients, who had laparoscopic supracervical hysterectomies, continued to menstruate. Nursing complications included two transient nerve injuries, one femoral and one peroneal. Equipment complications had the highest incidence; the most common type was bipolar cautery dysfunction (22 of 45). There were two video difficulties and one lost laser tip. There were no cases of death, postoperative ileus, fever, thrombophlebitis, transfusions, urinary tract infections, urinary atony, pneumonia, bowel injuries, ureteral injuries, or atelectasis. All patients were treated as outpatients, and no one was admitted or readmitted. Ninety-eight percent of the complications were mild to moderate, with only 2% (one of 45) severe.Overall complication rates are high after laparoscopic hysterectomy, even though the complications are predominantly mild to moderate in severity.