CO₂ and Nd: YAG lasers have been used in head and neck surgery for the past twenty years, KTP laser recently as well. The history of laser surgery in head and neck area and our experience are presented. Endolaryngeal laser surgery has been most commonly performed worldwide since 1972 and more than 300 patients have been treated in period 1980 through 1994 in our clinic. Laser surgery is useful to treat bilateral vocal fold paralysis, laryngeal stenosis and/or web, leukopracia, laryngeal papillomatosis and T1 glottic cancer. Fifty seven cases of T1 glottic carcinoma treated by laser surgery were reviewed. The 3-year determinate survival rate was 100% and the voice coservation rate was 91%(52/57). Laser turbinectomy has been done for the treatment of allergic rhinitis and hypertrophic rhinitis in our outpatient clinic. This therapy was effective in 178 of 204 patients (87%).

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This reports express author's opinion of technical barriers. Laser medicine and surgery should be play the leading part of laser applications. Therefore, the growth has come to a standstill in front of barriers. One of technical barriers is safety. It is a important to defense against the poisonous gas of a gas laser and the harmful materials of a laser delivery system. In the second, a small size of a laser apparatus are desire. The third barrier is a handling of a laser. All parsons want to adjust the laser oscillating mode with simplicity. No almighty laser delivery system can be transmitted all of lasers. Laser oscillating stability, in the forth barrier, should be keep. And, it is a successful way to laser medicine and surgery that the relationship between wisdom of a doctor and science technology of a engineer keep tying.

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In Japan, where the incidence of stomach cancer is among the highest in the world, marked development has been made in its diagnosis and treatment due to the efforts of a number of pioneers, and good therapeutic results are being achieved.
Particularly, the diagnosis of early cancer is excellent, and more than half the patients who undergo surgery for stomach cancer today have early cancers.
With the increase in the number of cases of early stomach cancer, patterns of progression and metastasis have been revealed. Presently, size-reducing operation has been introduced, and endoscopic treatments are being performed depending on the nature of cancer. Lasers have been used for the treatment for stomach cancer since about 1980, at first primarily for inoperable cases.
Thereafter, with accumulation of therapeutic results, lasers have been applied as a radical treatment for limited lesion types. However, the focus of attention of endoscopic treatments has been shifted to demucosation after its advent in about 1985 because of its characteristic that the pathologic tissue can be collected for histopathological evaluation unlike coagulation-cauterization procedures such as laser.
However, demucosation also has a number of technical limitations, and its indications are severely restricted. Today, we combine characteristics of demucosation and laser therapy and select the therapeutic approach according to the nature of individual early stomach cancer. In this study, we evaluated the results of laser irradiation in 158 patients with early cancer treated at our institution and the nature, size, and depth of the lesions are described in connection with the duration of the follow-up period, and present our views on the position of laser therapy in the contemporary treatments for stomach cancer.

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Since 1982, we have performed endoscopic Nd: YAG laser therapy for palliation of cancerous stenosis of the upper gastrointestinal tract. In 111 patients suffering from malignant dysphagia, we used the Nd: YAG laser as a palliative therapy for stenosis relief and the improvement of dietary intake. The stenosis were located on the esophagus in 20 patients, on the cardia in 50 patients, and on the other in 41 patients.
The “prograde method” by t he non-contact irradiation were reported by Fleischer et al, in 1982. And then, since the publication of the “retrograde method”by Ell et al, in 1986, this “retrograde method” has been routinely performed and in west counties, became the mainstream of treatment. On the other hand, our treating method were largely performed by the“prograde method”of the contact irradiation. The patients were treated once to twice a week until luminal patency was achieved, and then thereafter, were maintained by treatment given at 2-to-4-week intervals.
Stenosis improvement was evaluated based on the following three definitions: Technical success, functional success, and clinical success. Luminal stenosis was graded as follows: Grade 0: A thick endoscope can pass through. Grade 1; A thin endoscope can pass through. Grade 2; 5mm at the narrowest part in width. Grade 3; A pinhole or complete obstruction. The improvement by one grade or more for one month or longer were designated as “technical success”. Dietary intake was graded as follows: Grade 0; no dysphagia, Grade 1; sometimes solids, Grade 2; semisolids, only, Grade 3; fluid only. Grade 4; complete dysphagia. The improvement by one grade or more for one month or longer was designated as“functional success”. The period of the non-hospitalization for one month or longer after the first laser therapy was designated as“clinical success”. The technical success, the functional success and the clinical success were 62.8%, 55.0% and 45.0% in esophagus, and 78.0%, 78.0% and 61.2% in cardiac region, respectively.
Good adaptability to laser therapy, as to the patient's characteristics, was noted for advanced age and a performance status of grade 2 or under. Tumors located in the lower or mid third of the esophagus, those with a length of 6cm and shorter and those located cardiac region were well adapted to the Nd: YAG laser therapy. The contact method were more adaptable to each lesion than the non-contact method.
As to the survival time and the lengths of time in which patients required no hospitalization (no hospitalization period), there was statistically no significance between the laser and the non-curative resection groups in cardiac region. On the other hand, the median survival time was 27 weeks in the laser group and 11 weeks in the chemotherapy alone group (P<0.05) in cardiac stenosis. In addition to that, the median value of no hospitalization period was 16 weeks in the former and only one week in the latter (P<0.05),
We conclude that Nd: YAG laser therapy is a useful palliative treatment for improving the stenosis in the esophageal and the cardiac region. It could he said that the laser treatment should be applied as the first choice to a patient who is of poor risk or in whom the surgical procedure is considered to end in a no n-curative resection.

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Esophageal cancer reacts to photodynamic therapy (PDT) markedly and it necrotizes easily besides the ulcer after PDT repairs soon, because it is more sensitive to PDT than gastric cancer. In order to improve the therapeutic effectiveness of PDT with Photofrin II and laser light for superficial esophageal cancer, we employed an excimer dye laser instead of an argon dye laser since 1990. The characteristics of the current laser are as follows: wavelength, 630nm; pulse energy, 4mJ; peak power, 400kW; pulse width, 10nsec; frequency of repetition, 80Hz; average output, 320mW. The entire lesion plus a 5-mm wide perimeter of mucosa was irradiated with an EDL beam at 630nm wave length transmitted endoscopically.
In PDT for esophageal cancer, we had used a front-view fiberscope (model GIF-P10, GIF-XQ20, Olympus, Tokyo, Japan) for five cases with esophageal cancer according to the traditional method of diagnostic endoscopy until 1991. But uniform irradiation was difficult, especially with large lesions, because of esophageal peristalsis and respiratory movement. Since the first trial using a side-view fiberscope in PDT for esophageal cancer in 1992, we used a side-view fiberscope (model GF-20, Olympus, Tokyo, Japan) for five cases with esophageal cancer, not only in PDT, but also in pretreatment examinations and follow-up examinations. Two of them were located in abdominal esophagus (Ea) just above EC junction, where PDT had been considered out of application. In this procedure, patients with a lesion located on the right side can lie in a left lateral position as usual, whereas patients with a lesion located in the left side, especially from 7 to 10 o'clock, must lie in a right lateral position. This enabled photoradiation of esophageal cancer from a 90°angle without any difficulty, besides with less energy intensity of the irradiated laser light. Of these 10 lesions, 9 were cured by initial treatment and no recurrence was proved by endoscopy and biopsy. The final rate of cure was 90% (9/10).

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We studied the outcome of laser therapy in 85 patients with early gastric cancer who were treated between 1980 and September 1995. Laser therapy was relatively indicated in all patients. The final cancer-free rate was 64.7%. The final cancer-free rate according to lesion diameter was 100% for ? 9mm. 80.0% for 10-14mm, 75.0% for 15-19mm, 62.5% for 20-24mm, 53.3% for 25-29mm, 71.4% for 30-34mm, 100% for 35-39mm, 66.7% for 40-44mm, and 0% for ?45mm. The final cancer-free rate according to the estimated depth of invasion was 73.2% for mucosal cancers and 56.8% for submucosal cancers. The final cancer-free rate according to the macroscopic classification was good for depressed and mixed type (72.1%), but only 35.3% in elevated type, apparently because many patients with elevated type lesions refused additional treatment. The final cancer-free rate according to microscopic classification was 54.5% for undifferentiated (por and sig) type and 71.2% for differentiated (tubular) type. Among the patients with residual cancer, the mean survival period was 3 years 3 months in the survivors with cancer who died of other causes and 1 year 7 months in the patients who died of gastric cancer.

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We performed two endoscopic treatments for early gastric cancer. Thirty-two cases (34 lesions) were treated by laser irradiation during a period between 1987 and 1995, and 57 cases (68 lesions ) were treated by endoscopic mucosal resection using a cap-fitted panendoscope named EMRC during a period between 1992 and 1995.
On 32 cases of laser irradiation, 23 cases were first option which contained 8 relative indication cases and 9 cases were second option which were residual cancer after ethanol injection or mucosal resection. We used Medical YAG laser system MC2100 which has 1.32μm wavelength in addition to 1.06μm wavelength. 1.32μm wavelength is highly absorbed to living tissue than 1.06μm wavelength, thus we can take laser irradiation more safely and effectively with lower output using 1.32μm wavelength.
We experienced no complication on 32 cases of laser therapy. Three cases had residual cancer, and of them 2 cases required operation. Histopathological analysis of the lesions of the resected stomach showed almost all of the submucosal layer was replaced by fibrosis due to laser irradiation. Six cases died from other disease.
With EMRC, we could perform mucosal resection for lesions of all portion, get large specimens, and perform planning fractionated resection safely. EMRC is our first option of treatment for absolute indication lesions. With laser therapy, we could irradiate almost all of the submucosal layer even when the lesion had ulcer or ulcer scars, and admission was not necessary using 1.32μm wavelength. Laser therapy is our first option of treatment for lesions with ulcer or ulcer scars, lesions invading submucosal layer and residual lesions after other endoscopic treatments.

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We performed endoscopic treatment for 210 early gastric cancer lesions with 186 cases for the last fourteen years. We studied the efficacy of combination therapy of endoscopic mucosal resection (EMR) followed by Nd: YAG laser irradiation for early gastric cancer from the view point of long-term prognosis. The objects of this study are 157 lesions after endoscopic treatment. They are divided into 3 groups: the first group is 78 lesions with absolute indication (0-I, IIa, IIb, IIc without ulcerative change whose depth of invation was limited mucosaal layer and size was less than 20mm in diameter with differentiated type of adenocarcinoma), the second group is 22 lesions with relative indication (the same type of macroscopic and histological findings as absolute indication except with more than 21mm in diameter) and the third group is 33 lesions which have no indication for endoscopic treatment and can not be operated. The recurrent rate was 10% in absolute indication group and 32% in relative indication group. However, additional treatment diminished the recurrent cancer in all cases and the effective rate was 100% in both groups. Among 100 lesions which passed more than three years after endoscopic treatment. 32 lesions treated with only EMR and 38 lesions treated with EMR followed by Nd: YAG laser irradiation. The recurrent rate was 0% in the group treated with only EMR and 21% in the group treated with EMR followed by Nd: YAG laser irradiation. However, additional treatment diminished the recurrent cancer in the group treated with EMR followed by Nd: YAG laser irradiation and the effective rate was 100% in both groups. Therefore, we concluded that EMR followed by Nd: YAG laser irradiation can cure early gastric cancer lesions with relative indication as well as the lesions with absolute indication.

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Hysteroscopic surgery has recently being more commonly performed for intra-uterine lesions, since it is a rapid, non-invasive procedure which avoids major surgical intervention and post operative pelvic adhesions. Because Nd; YAG energy can pass through water with little effect and can be delivered through a flexible fiberoptic endoscope, it can be used in the fluid filled endometrial cavity in hysteroscopic surgeries. Between 1988 and 1995, we performed 203 hysteroscopic surgeries using either high frequency electrical power or Nd; YAG laser, among them, 17 cases were done solely by Nd; YAG laser. The hysteroscope used was FUJINON hysterofiberscope (HYS-FT) and OLYMPUS hysteroresectoscope. The Heraeus Laser Sonics model 6000 equipped with a bare end fiber-optic cable (1.1mm in diameter) and Helium neon laser as a tracking low power laser to aim the beam was utilized for the hysteroscopic surgery. Contact delivery of the beam was mainly used for pedunculated lesions and non-contact delivery mode for non-pedunculated lesions. 0.5-2 second pulses with power level of 20-40W were delivered. The laser operations were performed on eases with submucous leiomyomas, endometrial polyps, intra-uterine adhesions as well as uterine septum. This method utilizing flexible fiberscope leaves less dead angles in the uterine cavity, thus, proved to be more suitable to manage the pedunculated lesions. All cases which were treated by laser surgery showed improvement or disappearance of symptoms such as hypermenorrhea, metrorrhagia, postoperatively. Second look hysteroscopy showed no residual tumor tissue or intra-uterine adhesions.

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Among the women who suffered from endomertiosis, pelvic adhesion and polycystic ovarian deseas were treated by endosopic approach to evaluate the effectiveness and consequent pregnancy rate after endoscopic treatment. For endoscopic incision, coagulation and vaporization, KTP/YAG laser system was used. In the women with endometriosis, all endometriotic implants were vaporized and chocholate cysts were removed. The reccurrence rate in patients with chocholate cyst was 23.6%which was significantly lower than that in patient without surgical treatment, and moreover, the duration of deseas free period was longer than that in patient treated with danazol or Gn-Rh analoug. In cnsequence of these result, the pregnancy rate was relatively higher in the patients with endoscopic treatment. In the women with pelvic adhesion, the pregnancy rate was 47.5%in patients with adheiolysis which was significantly higher than in patient with inspection only (20.6%). In patients with polycystic desease who suffered from ovarian hyperstimulation syndrome, the pregnancy rate was 73.1%and the incidence rate of ovarian hyper stimulation was significantly reduced. These results indicated the effectiveness of endoscopic treatment for the infertle women with pelvic deseases.

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We conducted a phase II study to evaluate the activity and toxicity of photodynatnic therapy (PDT) with photofrin II in centrally located early-stage lung cancer. Main entry criteria were as follows: 1) histologically proven squamous cell carcinoma; 2) all lesions located in subsegmental or larger bronchi; 3) performance stasus of 0 to 2 and Pa02?60mmHg; 4) no lymph node or distant matastases. All patients received photofrin II (2mg/kg) intravenously 48 hours before PDT. The lesions were superficially radiated by argon dye laser or excimer dye laser (100-200 J/cm2). From Jnue 1989 to February 1992, sixty-four lesions in 54 patients were entried. 61 lesions were eligible for toxicity evaluable and 59 lesions were assessable for response. Of the 59 assessable lesions, 50 (84.8%) achieved complete response (CR) after initial PDT. The multiple regression model indicates that estimated length of longitudinal tumor extent (?10mm) was the only independent prognostic factor for CR (p=.0021). Toxicities by PDT with photofrin II according to WHO criteria (grade 2) were transient of ALT (1.9%), pulmonary toxicity (73%), allergic reaction (7.7%) and sunburn (1.9%). In concluision, PDT with photofrin II was effective for patients with centrally located early-stage lung cancer who have limited tumor invasion extending 10mm or less. Based on these results, in 1993 we initiated a phase II study of PDT with photofrin II and excimer dye laser for operable centrally located early-stage lung cancer. This study aimed to evaluate whether PDT can used as an effective alternative therapy to surgery in patients (pts) with operable centrally located early-stage lung cancer. Twenty pts of planned 40 have entered and conducted interim analysis. Of 20 pts with 20 lesions, 17 were eligible for response and toxicity. Of 17 pts, 15 (88.2%) had a CR, and 2 pts without CR received curative resection. of cancer. This study should progress to determine whether PDT can be used as an effective alternative to surgery.

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Twenty one cases of Nd: YAG laser irradiation to the stenosis in trachea or main bronchus were analyzed, which involved 15 cases of malignancy and 6 cases of inflammation. Thirteen cases were located in trachea and 8 cases in main bronchus, and 3 cases were performed with rigid scope (Dumon scope) under general anesthesia and 12 cases with flexible scope under local anesthesia during a period between 1983 and 1995.
Vaporization with a flexible scope under local anesthesia is an effective treatment, but it demands so heavy load to the patients during long term and many frequencies and high energy irradiation. On the other hand, laser coagulation to the bleeding point after mechanical reduction of tumor mass with rigid scope under general anesthesia is safe and reliable method, and it is more comfortable for them, especially for the poor risk patients.

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Minicaliber steerable ventriculoscope was developed for less invasive surgery in the lateral and third ventricle which filled with cerebrospinal fluid. This endoscope,which image is constructed by silica fibers, has 2.8mm of outer diameter, and equiped with 1.2mm single working channel for surgical instrument such as forceps and laser fiber. We have used this minicaliber ventriculoscope for third ventriculogram in the stereotactic surgery, third ventriculostomy in the cases with obstructed hydrocephalus, tumor biopsy, fenestration of cyst wall and septum, and removal of ventricular tube in the choroid plexus. In this endoscopic surgery, Nd:YAG laser was useful for cutting of third ventricular floor, cyst wall, septum and tumor capsule, coagulation of choroid plexus and vesssels of the tumor capsule. Coagulation and cutting of tissue can be effectively achieved by 7 to 25 watts of laser power in contact or near contact mode using with 0.4, 0.6, and 0.85mm of laser fiber. Further advancement of laser technique such as hemostasis of intraoperative bleeding and greater cutting, and surgical instrument is expected for intraventricular endoscopic surgery.

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KTP (potassium titanyl phosphate) laser was successfully applied to neuroendoscopic procedures of intra-ventricular lesions: fenestration of cyst-wall or the floor of the third ventricle (third ventriculostomy) in 27 patients, and vaporization of tumor or adhesive granulation tissue (in case of shunt-tube removal) in 5 patients.
Prior to clinical use of KTP laser, temperature change in the ventricle caused by KTP laser irradiation was investigated using a plastic model of the ventricle. With KTP laser output up to 15 watts in 1 sec pulse mode, temperature increase in the ventricle model was within 5 degree. Continuous irrigation with saline effectively protected the irradiation-induced temperature increase. However, over 10 degree increase in temperature was measured, when the output of 20 watts 1 sec pulse mode was employed in the air.
These results indicate that optimal conditions of KTP laser for clinical use would be 2-5 watts for the fenestration and 5-15 watts for the vaporization in 1 sec pulse mode with continuous irrigation of the ventricle by lactate Ringer's solution.

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Present situation of laser neurosurgery using operating microscope and endoscope are discussed. The lasers which we have mainly used are the CO₂ laser and KTP laser.
The CO₂ laser is very useful to remove hard tissues, even calcified one, through narrow surgical field, especially in cases of deep-seated highly vascular tumors. A case of teratoma in the third ventricle and a case of deep-seated cavernous angioma in the left posterior temporal lobe which were removed by the CO₂ laser are presented in this paper. The dural protector which we developed enables the operator to perform safe and complete removal of ossified posterior longitudinal ligament.
Vaporizing capability of the KTP laser is far stronger than that of the YAG laser in the open-air surgical field. One of the advantages of the KTP laser is that it can be applied through fine optical fiber, which enable endoscopic use through CSF. And also the handpiece of the KTP laser can be designed very thin and light because this laser beam can be transmitted through optical fiber, which is very important in microsurgery.
Recently we have started endoscopic examination of spinal lesions. This new technique revealed some interesting findings, such as rapid to and fro movement of CSF in the area where the subarachnoid space is narrowed, which is impossible to observe without this method. Hyper-vascularization of cauda equina caused by spinal tumor, thickning and adhesion of arachnoid were clearly observed by this sytem. However, development of special bipolar coagulator which can be applied through the working channel is indispensable prior to endoscopic interventions of spinal lesions, although the KTP laser is already applicable.

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CO₂ laser and Nd: YAG laser have been used in the treatment of laryngeal diseases for the past twenty years, and recently KTP laser has been also used. Endolaryngeal laser surgery has been performed for over 300 patients during 1980 to 1994 in our clinic. We present the method and the usefulness of laser surgery to larynx. There are following three methods of endolaryngeal laser surgery; 1 Microsurgery via micromanipulator with KTP or CO₂. 2 Microsurgery via handpiace with Nd: YAG or KTP. 3 Flexible endoscopic surgery with CO₂, Nd: YAG or KTP. The operator should know merits and demerits of each lasers and select the method of surgery. Laser surgery is useful to treat bilateral vocal fold paralysis, laryngeal stenosis (web), leukopracia, laryngeal papillomatosis and T1 glottic cancer.

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Many types of lasers have been developed until now. Several lasers have become new useful tool in the microsurgery. In the ear surgery.laser is usually used on the middle ear disease. But the most epoch-making application of lasers is thought to be used on the inner ear disease. According to the animal study small localized lesion could be made on the membrane rupture em using argon or KIP laser. I think that the sole tool which we can use in the inner ear surgery is the argon or KIP laser.

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Using a contact Nd-YAG laser, we have vaporized the pathological inferior turbinates of the patients with perennial allergic rhinitis and hypertrophic rhinitis resistant to medical treatment since 1993.
We performed this operation on 24 patients during a period between June 1993 and May 1994 at JR Tokai General Hospital. One month after the treatment, 13 out of evalutaed 17 patients no longer needed anti-allergic or any other drugs. One patient had been under treatment for nine months.
We evaluated 11 patients, who received our operation before one month, on nasal mucosal response for a vasoconstrictive drug (Naphazoline-nitrate). All of 11 pateints were under treatment, but kept nasal mucosa response for that drug. The difference between histologic findings of one patient at preoperation and those at 3 months after the operation was not almost showed.
We conclude that contact Nd-YAG laser surgery is useful for the treatment of turbinate dysfunction in patients with perennial allergic rhinitis and hypertrophic rhinitis resistant to medical treatment.

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Argon laser and KTP laser are introduced in tympanoplasty under the microscope. Laser is useful for vaporizing malformed ossicles, fixed ossicles and hyaline deposit in the middle ear. The surgical technique and results are reported. Rationale and advantages over conventional method are discussed.
The argon laser is thought to creat localized lesion on the sensory organs of the inner ear without labyrinthine membrane rupture. The specific application of the argon laser on the inner ear disease was presented.

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Laser surgery is one of surgical treatment for allergic rhinitis. We observed morphologic changes in nasal mucosa before and after laser surgery using an optical microscope and scanning electron microscope. The following results were obtained;
1) Hyperplasia of the mucous epithelium, thicking of the basement membrane, edema of the lamina propria mucosae, eosinophilic infiltration,enlargement of the nasal glands and dilatation of the sinusoidal capillary were noted in the allergic nasal mucosa before laser surgery.
2) After laser surgery, the nasal mucosa was covered with epithelium that was squamatized or cuboidal and/or columnar epithelium that was stratified. Granulation-like tissue or cicatricial tissue was found, but edema, eosinophilic infiltration and enlarged nasal glands all but disappeared in the lamina propria mucosae.

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A new photosensitiser, NPe6, was applied to visualize atheromas, NPe6 has been known to accumulate selectively in malignant tumors. We have demonstrated that NPe6 was a potent probe to indicate atherosclerotic plaques depending on it's specific accumulation in the atheroma. The aim of this study is to visualize the atherosclerotic coronary artery on the heart surface in vivo using a newly developed device, an epifluorescence microscopy.
Ten female New Zealand white rabbits were fed on an atherogenic diet containing 0.5%cholesterol for 20 weeks. At 6 hours after administration of NPe6, at a dose of 5mg/kg, rabbits were anesthetized with pentobarbital sodium. Under artificial ventilation, the chest was opened and the heart was mounted on the pericardial cradle, so that we can see the heart surface clearly. The laser beam with a wavelength of 664nm from a diode laser was irradiated on the heart surface, The atherosclerotic tissues in the coronary artery was recognized by detecting the reddish fluorescence.
We have been reported that atheromas were diagnosed both angioscopically and laparoscopically by detecting the fluorescence spectrum of NPe6 using a spectrophotometer.In this study, we demonstrated specific detection of NPe6 fluorescence in the the atherosclerotic coronary arteries using an epifluorescence stereoscope system with a diode laser.

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Since 1984, endoscopic treatments for malignant esophageal obstruction have been actively performed with the purpose of improving the QOL, of end-stage patients. There are 54 cases treated by the combination of laser and other techniques, namely, bougienage or balloon dilation. Nine of them were treated by the high-power diode laser system which is small(38×40×15cm), light (11kg) and cheap. In 4 cases, obstruction (length: 4.25cm in average were treated by the diode laser wish bougie and balloon, but in the rest 5 cases, the prosthesis or memorial metalic stent was placed in cancer tunnel (length is 9.80cm in average).
The irradiation power was 20-25 watts and 1.0 seconds and a total energy for one patient was about 6000 jouls in average.
We obtained satisfactory results without any complication in these patients.
The common meal could be taken in all the patients and they could live for 2.8-6.5 months after the treatment. These results are better than those of patients treated by the Nd-YAG laser.
Such palliative endoscopic treatments for recanaligation should be more applied for the improvement of the QOL., of end-stage cancer patients in recent future. This high-power diode laser, we consider, will be more widely utilized because of its portalibity and lower-cost.

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Backgrounds: Autofluorescences of endogenous porphyrins and. flavins were reported to appear in accordance with oxygen radical induced mucosal injuries in ischemia-reperfusion stress. Using the cultured cells of a rat's gastric mucosal epithelial cell line, we examined a relations between the endogenous cellular fluorescence and cellular injury caused by oxygen radicals. Moreover, we also elucidate relations between porphyrins' fluorescence and intestinal lesions, and examine the clinical applicability of this phenomenon in endoscopy. Methods: Fluorescence intensity of a rat gastric mucosal cell line RGM1 was measured with an ultra-high sensitivity camera-image processor system under a microscope. Cellular fluorescence spectrum were also analyzed. Patients of colon carcinoma, colon adenoma and ischemic colitis in University of Tsukuba Hospital were removed pieces of colon mucosae. which were observed with a microscope. Extracts from these specimens were also analyzed with a spectrofmeter. Results: The cellular fluorescence intensity increased in accordance with H₂O₂ induced cellular injury. Fluorescent substances were indicative of flavins from the spectral pattern of excitation and emission. Mucosae of all these lesions emitted obvious fluorescence and showed statistical significant difference in comparison with normal mucosae. In particular, fluorescence of ischemic colitis was strong and different significantly from the other lesions. Fluorescent substances were decided as porphyrins and flavins with spectroanalyses. Conclusions: These findings indicate that FAD in the cytoplasm of cells injured by H₂O₂ increased in endogenous fluorescence according to the extent of injury, and suggest that fluorescence measurement can be a simple method of cellular toxicology to detect oxygen radical-induced injuries. Colon mucosal lesions were able to detect with the fluorescence endoscopy-image analyzing system. This system can show a highly sensitive diagnosis in endoscopy. The stronger fluorescent mucosa of ischemic colitis patients suggests that mechanisms of this phenomenon came from oxygen radicals.

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An Er: YAG laser is a near infrared laser with a wavelength of 2.94μm. This wavelength is identical to the peak wavelength of the light most readily absorbed by water. When used on living tissue with a sufficient water content, this laser causes a rapid evaporation of the water in just the most superficial layer of tissue, without greatly affecting the tissue in the neighboring area.
The present study was undertaken to assess the clinical usefulness in soft tissue surgery and scaling of a recently developed Er: YAG laser device, designed for dental use, according to the Criterion of Good Clinical Practice for medical devices (GCP) of Japanese Ministry of Welfare.
Thirty one patients with soft tissue lesions (13 males and 18 females from 24 to 71 years old), and sixty patients with calculus deposition (21 males and 39 females from 19 to 72 years old) were treated with the laser.The clinical parameters evaluated were: pain, redness, swelling of the gingiva and the unpleasant sound and vibration associated with the laser treatment. In addition, hemorrhage and wound healing during and after the surgery, and the roughness of the root surface after scaling and the effectiveness of scaling with laser were examined.
Laser surgery caused less hemorrhage and induce better wound healing compared 2with conventional scalpel surgery. It was easy to remove calculi from the root surface with the laser in 95% of the cases. Although the scaled site showed some irregularity, it was not clinical significant in 98% of the cases. Only a few patients complained about unpleasant sound and vibration.
There were no complications or side effects during this clinical trial. Thus, this study suggests that an Er: YAG laser is useful for soft tissue surgery and scaling.

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Various our studies on the application of Ho:YAG laser (wavelength: 2.1 μm) for urological therapy are reviewed. Since Ho:YAG laser light can be strongly absorbed by living tissue due to an affinity for water, it has excellent cutting properties with thin coagulation layer. In the case of contact irradiation in the tissue, a water vapor bubble is formed at the tip of delivery fiber. This bubble generates stress-wave in its expansion phase and shock-wave in its collapse phase. These mechanical wave induces a new type of tissue destruction which might be useful for destructive therapy. We developed a new laser treatment for ureteral stricture with multi-fiber catheter and benign prostatic hyperplasia by interstitial ablation using Ho:YAG laser. We investigated the efficacy of the these laser treatment and the principle of the laser fragmentation with Ho:YAG laser. In these studies, the characteristics of Ho:YAG laser is well demonstrated. We concluded that Ho:YAG laser may be the effective laser for urology due to its variety of therapeutic effects.

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To explain the mechanism of the stone fragmentation with Ho:YAG laser irradiation, we investigated the fragmentation efficacy in air and in water. We employed the stone model which had been reported by Uchida. The models in dry condition (water content: 14%), in wet condition (44%), and in water were fragmented with Ho:YAG laser on energy level of 0.5 J/pulse and at frequency of 10 Hz through a quartz fiber. The various components of stones were fragmented in air or in water similarly. The fragmentation efficiencies of models in dry condition, in wet condition and in water were 0.12 mg/J, 0.82 mg/J, and 3.0 mg/J, respectively. Those of calcium oxalate stone in air and in water were 0.12 mg/J and 0.36 mg/J. Those of calcium phosphate stone in air and in water were 0.32 mg/J, and 1.1 mg/i. It was clear that the stone fragmentation with pulsed Ho:YAG laser was caused by the expansion of vapor bubble, which was produced by irradiation in water within or around the stone.

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The tunable lasers are now used in medical applications, and most of them are dye lasers. But, it is not easy to handle dye lasers because of the short lifetime of dye, the short range of wave-length, and the troublesome dye disposal.
Therefore, other tunable lasers ;ex solid-state tunable lasers, optical parametric oscillator(OPO), raman-shifted lasers, and free electron lasers(FEL) have been studied on behalf of dye lasers.
This paper describes the present medical applications, the kind of tunable lasers, and the possibility of the future applications of them.

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According to increasing in the recording density and capacity of the optical disks for the application of DVD (Digital Video Disk), red semiconductor laser of 650nm wavelength are developed instead of conventional infrared semiconductor laser of 780nm wavelength. More short wavelength semiconductor laser of 500nm blue wavelength or 400nm purple wavelength are just research and development stage. Since semiconductor lasers cover the wavelength of visible light as described above, they are applied not only to the optical disk but also to medical equipment, bar code scanners, laser beam printers etc. This paper describes the current status and trend of development of visible semiconductor lasers.
(Red semiconductor laser): Red semiconductor laser consists of AlGaInP compound semiconductor material and are put to practical use in the 635nm to 680nm wavelength range. 670nm red semiconductor lasers are applied to the bar code scanners instead of He-Ne gas lasers and make the system to small size and low power consumption. Since DVD players loading 650nm red semiconductor lasers will be on sale in 1996, Red semiconductor laser will come into wide use. As for the application of red semiconductor laser to the medical field, 664nm high power (300mW) red semiconductor lasers are applied to the cancer treatment using PDT (PhotoDynamic Therapy).
(Blue semiconductor laser): Blue semiconductor laser consists of ZnSe which is a compound material of group II element and group V element. Many researchers are involved in developing the blue semiconductor laser. Since the blue semiconductor laser is just realized the CW operation at room temperature, keen competition is carried out.

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The basic performance of pulse-operated dye-doped plastic optical fiber (DPOF) for photodynamic diagnosis (PDD) and photodynamic therapy (PDT) and the photochemical property of photosensitizer are demonstrated. As the dopant in DPOF, Rhodamine 6G, which has a high optical gain of at the latter half of 500 nm, is prepared. Output power from the R6G-doped DPOF is irradiated onto the photosensitizer (zinc (II)5, 10, 15, 20-tetraphenyl porphyrin: ZTP), and fluorescence from the ZTP is observed. Generation of superoxide, which is a form of active oxygen, is confirmed by the method of photochemical reaction. In addition, the possibility of a medical-optical device DPOF is discussed.

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ATX-S10 Analogues for photodynamic therapy (PDT) photosensitizer are synthesized from protoporphyrin dimethyl ester (PP-Me) at 3 steps. At first, the photooxidatio of PP-Me is carried out to obtain a formylchlorin (photoprotoporphyrin dimethyl ester, P-Me). The derivative is treated with various ketone agents, for example, methylhydroxylamine, ethylhydroxylamine and so on. The resulting derivatives have a strong absorption (ε>10⁴) at longer wavelengths (>670nm) and good water-solubility, and the photosensitivities (dansyl methionine test) of them were satisfactory. Relationship tumor tissue affinity with chemical structure of these derivatives have investigated by means of Rt. at HPLC, biodistribution on N₂·PLS method and HPLC analysis, and interaction with HSA. ATX-S10 analogues are also efficient sensitizers on tumor tissue affinity. Therefore, the new derivatives seem to be more useful for tumor treatment.

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The effect of photodynamic therapy (PDT) using Mono-L-aspartyl chlorin e6 (ME2906) on vascular system was examined. Examination of blood flow condition was made by X-ray examination after circulation of barium sulfate on PDT-performed mice and microscopic observation of microvascular change on PDT-performing mice. The blood flow stasis and white thrombus formation were found in the vessels and vascular-shut-down was observed at the area performed PDT. According to electron microscopic observation, some organelle especially endoplasmic reticulum in tumor vascular endothelial cells after PDT were degenerated. On the other hand PDT did not accelerate on platelet aggregation or coagulation in vitro. These results suggest that vascular-shut-down effects are involved in the tumor therapeutic effects of PDT using ME2906. At that time PDT seems to form thrombus through the effects on the endothelial cells but not on the platelets or coagulation factors directly.

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Photodynamic therapy (PDT) was proved to be a safe and promising alternative for the treatment of patients with superficial esophageal cancer and early gastric cancer who are poor risks for surgery. However, it is very difficult to irradiate enough energy for the proper portion of the lesion, because we can not clearly observe not only the cancerous region, but also the border of irradiation spot during photoradiation. In PDT, a conventional electronic endoscope is not applicable, because excessive amounts of red light at 630nm wavelength for irradiation, which radiate unsystematically, prevent the charge coupled device (CCD) chip from forming and transmitting an image. Then, we used a fiberscope in PDT, with being placed a green filter on the eyepiece of the fiberscope to protect the naked eye from being dazzled during laser irradiation. This method improved being dazzled, but the image of mucosa turned to a greenish one. We could not clearly observe the border of the cancerous lesion. We, therefore, designed an original device for photoradiation in PDT combined an electronic endoscope and a laser. The device consists of an electronic endoscope whose light source is an electric flash lamp instead of a xenon lamp, and a pulsed laser. An ideal combination is an electronic endoscope with 60 frames per second and a pulsed laser with 240 pulses per second. They are conducted so systematically that the laser irradiates at a pause during the electric flash lamp illuminates, and then the CCD chip forms and transmits the image. Furthermore, the CCD chip accepts the image of one pulse of the laser out of four. In conclusion, the new device allows as follows: 1. The laser beam does not prevent the CCD chip from forming and transmitting the image of the mucosa illuminated with an electric flash lamp; 2. The CCD chip can take an image of a spot of laser irradiation, then the image passes through a real-time image processor, and finally the image will be shown on a monitor lied upon the picture of the lesion such as a blue ring. We showed this system can be created theoretically. It is only a dream at present, but in the future when it will put into practice, it will be very useful for PDT to come into wide use, although there will be many difficulties in putting the theory into practice.

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Novel after-loading interstitial therapy was performed in a canine transmissible sarcoma (CTS) model, utilizing photofrinII and an excimer dye laser. First, photofrinII was injected intravenously at a dose of 5mg/kg, the 48h later, laser-proof plastic tubing was implanted in the CTS and optical fiber was inserted into the tubing, followed by photoradiation of the tumor from the inside. The mean diameter of tumor necrosis rapidly increased in parallel with increase in total irradiation energy below 240J/cm, the mean diameter of tumor necrosis was 20.7mm after energy of 120J/cm, and 24.5mm at 240J/cm. Beyond 240J/cm, the diameter gradually increased to 26mm at 960J/cm. As a side effect, cutaneous tissue showed a deep open ulcer at 240J/cm, a shallow ulcer 120J/cm. The thermal effect of laser light is considered negligible below 480J/cm. In addition, 3 hours later after an intravenous administration of BPD-MA verteporfin at a concentration of 2mg/kg, PDT was performed in CTS at conditions of 0.32watt with novel afterloading interstitial PDT using excimer dye laser. At a dose of 150J/cm, the diameter of tumor necrosis was estimated to be 35mm. The problems and future prospects of this interstitial PDT was discussed.

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The efficacy of photodynamic therapy using porphymer sodium (PF) and newly-developed chlorin derivative (ATX-S10) for occlusion of corneal new vessels has been evaluated experimentally. Twenty-six albino rabbits were treated with an intravenous injection of 2mg/kg of PF, followed by argon green laser (514nm) irradiation to the corneal new vessels with three varieties of energy at 24, 48, 72 and 96 hours after the injection, respectively. In another group of 4 rabbits, diode laser (672nm) was irradiated with the energy from 43J/cm2 to 323J/cm2 at 4 and 6 hours after the administration of 12mg/kg of ATX-S10, respectively. The closure of corneal new vesseles was confirmed by slit-lamp examination, fluorescein angiography and light microscopic study. With PF, irradiation with exposure energy of 19.1J/cm2 during 24 and 72 hours after the administration was estimated to be suitable for the treatment, because new vesseles were closed with a mild damage of the surrounding normal tissue such as the iris. Exposure energy more than 38.2J/cm2 was thought to be excess since surrounding normal tissue was heavily damaged. With ATX-S10, selective closure of corneal new vessels were obtained by irradiation with exposure energy of 86.1/cm2 and 258J/cm2 at 4 and 6 hours after the administration, respectively. In control groups which received laser irradiation without photosensitizer administration, new vessels were not closed. These results suggests PF and ATX-S10 used here are new therapeutic agents for the treatment of corneal neovascularization. Especially, ATX-S10 is a promising new photosensitizer since it has more rapid elimination from the body and less skin phototoxicity than PF.

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It has been reported that the incidence of advanced cancer of the uterine cervix is decreasing due to the enforcement and popularity of cancer screening clinics. On the other hand, cervical intraepithelial neoplasia such as dysplasia and carcinoma in situ (CIS) have been noticeably increasing particularly among the young generation in the child-bearing age and therefore a need for conservative surgery of the uterus is in order. We performed conservative operations on patients with CIN and uterine cervical cancer using CO and Nd YAG laser treatments over the last six years. Patients who received laser therapy included 229 who received laser vaporization and 389 who received laser conization. Among these patients, the pathological diagnosis for 55 who received laser conization revealed microinvasive or invasive squamous cell carcinoma. Among the 10 patients with surgical margin remaining positive after conization or with deep stromal invasion by pathological examination, additional treatment consisting of hysterectomy and/or radiotherapy were performed. In those with microinvasive carcinoma who wanted to preserve their uterus, a cure with laser conization was achieved in 97.2%(35/36). There was only one recurrence noted among these patients and this was the case wherein enough lesion could not be excised and post operative pathological examination revealed positive margin. This said patient underwent laser conization during pregnancy at 18 weeks age of gestation and three years thereafter, she was found to have CIS for which she underwent REconization.
The above results suggest that laser conization can be applicable for the treatment of cervical microinvasive carcinoma accompanied by long term follow up and strict pathological diagnosis. Nevertheless, however, more cases would be appropriate to statistically confirm this possibility

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Between 1985 and 1994, two hundred and nineteen patients with biopsy proven cervical intraepithelial neoplasia (CIN) with satisfactory colposcopy were treated with the carbon dioxide laser, and 178 patients were treated with cryosurgery in an outpatient setting. There was no statistical differences in the incidence of persistent disease, cumulative cure rate calculated by Kaplan-Meier Method between the two treatment groups. However, there was a tendency that Laser treatment had lower persistent rate and higer cure rate in the CIN grade 3. Laser vaporization had statistically higer incidence of treatment related hemorrhage. On the other hand, troublesome watery discharge was prominent in the cryosurgery patients. Invasive squamous cell carcinoma has not been identified in either treatment group in the follow up period. These results reconfirm the efficacy and safety of laser vaporization for all form of CIN.

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[Aim] Resectoscopy and Laser hysteroscopy, both of advanced medical instruments are rapidly expanded into common gynecologic fasilities. Character of resectoscopy (RS) and laser hysterofiberscopy (LHFS) was investigated from the point of basic, clinical, and economic view. [Methods and Results]# Basic Experiment-1: Tissue concentration of inflammatory marker in mouce uterus was measured at the point 1 cm departed from the irradiation with Nd; Yag laser, electric cautery, or cold knife. Leukotrien was used as tissue inflammatory marker. The level at the point with laser irradiation was lower than the point with electric cautery. Cold knife showed the middle level of leukotrien between laser and cautery.# Basic Experiment-2: Distribution of white blood cell of the uterine cervix of the cow was counted at the point irradiated with Nd; Yag Laser or electric cautery. The count with laser irradiation was smaller than the electric cautery.# Clinical investigation-1: The direction of the beam of Nd; Yag laser from LHFS and the cutting way of electric cautery from RS was theoreticary investigated. The beam of the laser from hysterofiberscope runs from the top of the scope end beyond the target tissues. It means laser surgery contains risky part that the top of the beam is not able to wacth with hysterofiberscope. On the other hand, RS is safer method because the direction of cutting way is from distal part to proxismal part (the scope head). But RS surgery is some times more difficult than laser surgery because the sturucture of the RS is rigid# Clinical investigation -2: Operation time of RS or LHFS for submucosal myomectomy was compared RS surgery needs longer time than laser surgery.# Economic comparison: General purchase price for RS and LHFS was compared RS is much more reasonable. LHFS is good instrument. But in order to use LHFS safely, Laparoscopic and intra-abdominal ultrasound guidance is necessary. RS will be more commonly used because RS is safer and cheaper.

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Nd; YAG laser can be applied to hysteroscopic surgery, since it can pass through fluid without effect and can be transmitted through flexible fiberoptic cables. It can be delivered in pulses with non-contact mode by bare end fibers without using ceramic tips. Whereas, high frequency electrical power has been applied to hysteroscopic surgery since the time when Neuwirth applied urologic resectoseope into hysteoscopy. It has both cutting and coagulation mode and can supply stable power to extended areas, thus, is suitable to resect large amount of tissue in such cases as non-pedunculated myomas or uterine septa. We have performed 203 hysteroscopic surgeries between 1988 and 1995. Postoperative diagnoses of those cases were submucosal myomas (n=66), myoma deliveries (n=77), endometrial polyps (n=28), cervical polyps (n=8), intrauterine adhesions (n=9) and septate uterus (n=15). Nd; YAG laser was utilized in 17 eases and high frequency electrical power in 186 cases. Mean operation time was 46.3±31.5 min. and mean specimen weight 13.7g±19.0g. When Nd; YAG laser was used, mean operating time was 60.0±33.3 min. and mean specimen weight was 2.3±2.3g. 90%of these cases showed improvement of symptoms such as hypermenorrhea, metrorrhagia or anemia and 2nd-look hysteroscopy revealed no residual lesions in 88.3% of the cases. Among 55 infertile cases, 26 (47.3%) became pregnant post-operatively. So far, we have not experianced major complications such as perforation of the uterus, massive bleeding or TUR syndrome.
Thus, our data demonstrated that hysteroseopic surgeries are safe and effective, minimally invasive proceders for the treatment of intra-uterine lesions.

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Operative laparoscopy was performed on ninety-eight cases with gynecologic benign disease. Lasere equipments (Nd: YAG, KTP/YAG, Ho: YAG), electrocautery (monopolar, bipolar, Argon beam coagulator) and Harmonic scalpel were used. For the treatment of ovarian cyst, drainage, ethanol fixation, ablation of lining, stripping of lininig (intra orextracorporeal) and adnexectomy were performed on them. For adhesion, lysis, and/or TUSL (Transection of Utero Sacral Ligament) were carried out. For myoma, adenomyosis, carcinoma in situ of uterine cervix and descensus uteri with adhesion, LAVH (Laparoscopically Assisted Vaginal Hysterectomy) were carried out.
In the group of endometriosis with endometrioma, 69.2% (18 of 26) reported over 50% pain relief and 11.5% (3 of 26) reported no pain from menstrual pain after the surgery. Recurrent endometrioma was found in 42.3% (11 of 26). In the group of endometriosis, 71.4% (15 of 21) reported over 50% pain relief and 23.8% (5 of 21) reported no pain from menstrual pain. In the group of pelvic inflammatory disease and dysmenorrhea, 57.1% (4 of 7) reported over 50% pain relief and 28.6% (2 of 7) reported no pain from menstrual pain. In the group of ovarian cyst, recurrent cyst was found in 5.9% (1 of 17). All patients after the LAVH had no complaints.
Their complications during and after the operation were minimal. There was no difference between the Laser group and the other group in the results and complications.

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We reported the clinical results of laser therapy for glaucoma with newly developped two kinds of laser systems. One was a diode laser and the other was a Holmium YAG laser.
1)We performed transscleral cyclophotocoagulation (TSCPC) using a diode laser in refractory glaucoma patients, 18 eyes of 16 patients with neovascular glaucoma (NG) and 6 eyes of 6patients with secondary glaucoma (SG). Preoperative intraocular pressure (IOP) averaged 37.4±10.6mmHg (mean±SD) in NG and 32.0±5.7mmHg in SG. IOP control rate, analyzed by the life table method (Kaplan-Meier), was 65.2% in NG and 38.5% in SG. Postoperative complications were minor and no phthisis bulbi was observed. The results indicate that TSCPC with diode laser deserves further investigation as a treatment modality for refractory glaucoma.
2) We performed sclerostomy ab externo with Holmium YAG laser in 21 eyes of 20 glaucoma patients. with poor surgical prognosis. An antimetabolite, mitomycin C (MMC) or 5-fluorouracil (5FU), was used after surgery. IOP averaged 37.9±16.5mmHg in MMC using eyes and 30.6±3.6mmHg in 5FU using eyes. IOP control rate, analyzed by the life table method (Kaplan-Meier), was 47.1% in MMC using eyes and 14.3% in 5FU using eyes. As postoperative complications specific to this method, Descemet's fold and iris incarceration to the sclerostomy stoma were observed in some cases.
This seems to be a convenient method of performing sclerostomy, since it shortens operating time, and permits operation at any site on the limbus. However, the rate of IOP control was less than that obtained by conventional trabeculectomy, and postoperative complications specific to this metod were observed in some cases.
The results suggest that selection of patients is important.

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We evaluated recent photocoagulation treatment for choroidal neovascularization in senile disciform macular degeneration.
Subjects 1: 98 eyes which underwent indocyanine green (ICG)-guided laser photocoagulation for extra and/or juxtafoveal choroidal neovascular membrane (CNM). The photocoagulation success rates were 73 (75%) and 63 (86%) of the 98 eyes maintained or improved visual acuity after treatment. ICG guided-laser photocoagulation was confirmedto be useful for occult CNM by fluorescein angiography.
Subjects 2: 39 eyes which underwent laser photocoagulation for subfoveal CNM. Factors predicting a visual acuities of 0.1 or better were analyzed using the χ² test or Fisher's exact probability method. Factors predicting a visual acuity of 0.1 or better were the distance between the lateral margin of the CNM and the center of the foveal avascular zone being 1/3 disc diameter or less, and pre-treatment retinal sensitivity at the fixation point of 10dB or more. Good indications for photocoagulation of subfoveal CNM were found to be a CNM margin near the center of the foveal avascular zone, and relatively good retinal sensitivity at the fixation point.
Subjects 3: 11 eyes which underwent photocoagulation aimed at subfoveal CNM feeder vessels. In six of the 11 eyes, blood flow to the CNM was obstructed by photocoagulation. However, reopening sometimes occurred a few weeks after treatment. All eyes in which feeder vessel flow was obstructed by photocoagulation, showed resorption of blood and/or exudate, and maintained visual acuity after treatment. Feeder vessels of subfoveal CNM should be coagulated whenever possible.

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The orthor has investigated the effect of laser irradiation to dental enamel on caries prevention in the experimental study as well as the clinical study.
Experimental Study 1: The acid resistance of lased young premolar was determined by acid etching tecnique and SEM observation. The rise in temprature of pulp chamber with laser irradiation to enamel surface with the energy density of 50J/cm² was shown around 5°C. The proper energy density seemed around 50J/cm² on the base of the experimental study.
Experimental study 2: The inhibitory effect of laser irradiation with fluoride application on enamel demineralization of artificial incipient caries lesion was determined. APF application after laser irradiation to incipient caries was more effective for inhibiting enamel demineralization than the treatment of laser irradiation after APF application.
Clinical study: Eight young permanent teeth were exposed to Nd: YAG laser on their occlusal surfaces and followed up for more than five years. The caries had not found on all of them. The white lesions of thirty teeth were treated by Nd: YAG laser irradiation and APF application to be followed up for a year. White lesions have disappeared on 63.3% of the subjects and most of their surfaces have changed to be smoother.

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The Er: YAG laser has a wavelength of 2.94um. Its energy is primarily absorbed by H₂O. Unlike the CO₂ laser, which promotes heat generation because its energy is absorbed by CaCO₃ molecules, the Er: YAG laser seems to produce heat by vaporizing H O, especially water held in a crystalline lattice.
In other words, the Er: YAG laser is thought to produce heat by inducing the detachment of the OH-group from hydroxyapatite, i. e., the instantaneous evaporation of the solid layers of crystals and the hydration shell (Weyl, 1953).

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We investigated the possibility of treating the smear layer by laser irradiation. The surface of the smear layer was irradiated with a laser, and the changes were observed under a scanning electron microscope. A Nd-YAG laser (Osada YAG Laser) and CO₂ gas laser (Mochida Medilaser-MIC 30) were used in defocus. The results showed that both lasers induced changes in the smear layer. Depending on the irradiation level, the smear layer on the intertubular dentin was satisfactorily treated, with the tubular orifices closed.
Next, we determined the penetration of 1% methylene blue from the dentin surface when irradiated by both lasers under various conditions. It was found that while the dye applied to a non-irradiated dentin surface penetrated deeply over the entire area, an irradiated surface blocked dye penetration. This finding was also observed at low energy densities of 25-50J/cm2, which is very interesting from the standpoint of preserving dental pulp.

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We report basic animal experimental study which we evaluated the thermocoagulation fffects of two different type of Nd: YAG laser ( super-pulsed and CW laser ) The Rotalase internally reflecting fiber delivery system coupled to the super-pulsed and continuous wave (CW) Nd: YAG laser was used to create lesions in Seminoma tissue implanted Scid mice with the fiber tip 2mm away from the target tissue under the water. Laser power output used was 20, 40 and 60-watt for varying times (30-180 sec) of irradiation. Stationary lesions, where a single spot of target was irradiated, were created. On the other hand, We measured tissue temperatures at 7, 10 and 14mm from tissue surface.The seminoma tissues removed from Scid mice were photographed after bisection, the fixed in 10% formalin and examined histologically.
For the purpose of these experiments, ablated tissue is defined as the volume of tissue that has been destroyed by both coagulation and vaporization. Estimates of the volume of ablated tissue were made by macroscopic examination of the bisected lesion, measuring the depth and width of the lesion as seen from the edges of the coagulated area around vaporized zone. The mean depth and width penetration, volume ablation and rising of the tissue temperature at super-pulsed 60-watt, 60 second was greater than that observed at other groups. Irradiated spot lesions were characterized by an initial 10-20 second period of tissue blanching followed by an audible“popcorn phenomenon”which meant more than 100 C in tissue temperature, then formation of small surface bubbles as tissue began to evaporate and char. This study suggests the potential usefulness of the super-pulsed Nd: YAG laser for VLAP.

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Transurethral balloon laser thermotherapy (TUBAL-T) was performed on thirty patients with benign prostatic hyperplasia (BPH). The urethra was cooled at less than 42 degrees C by the urethral cooling system during the treatment, and the hyperplastic prostate tissue at 5 to 10mm depth from the urethral surface was heated at more than 45 degrees C. The depth of tissue damages ranged from 10 to 20mm from the urethral surface by CT or MR images. By pathological studies, the coagulonecrotic or degenerative changes of the prostatic epithelia, the smooth muscle cells and the small vessels were observed.
On twenty patients, I-PSS scores decresed to 9.3 points at 3 months later compared with 16.9 port before the treatment, and QOL scores improved at 2.5 points at 3 months compared with at 3.9 points before the treatment. While the prostatic volume in some patients decreased, the value was not significantly decreased at 3 months later. Adverse effects were minimal ( urinary retention in 2 patients; macroscopic hematuria in 2 administered anti-coagulant drugs), and it was thought that TUBAL-T was safe and useful method for BPH.

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For the past 50 years, transurethral resection of the prostate (TURP) has been the most common surgical treatment for benign prostattic hyperplasia (BPH). Alternative methods for treating BPH have been established during the past 10 years.
We assessed the safety and efficacy of visual laser ablation of the prostate (VLAP), performed with the Urolase and ProLase II laser fiber, compared to TURP in patients with BPH.
In this non-randomized comparative study, 50 BPH patients were treated with TURP and 50 and 25 were conducted with VLAP using Urolase and ProLase II laser fibers. Efficacy was assessed with International Prostate symptom score, urinary flow rate, postvoid residural urinary volume and estimated prostate volume.
There was a clinically significant improvement in all efficacy parameters in all groups. In the TURP, Urolase and ProLase II groups 81.6% (40/49), 92.0% (46/50) and 84.0% (21/25) were categorized as effective cases at 3 months postoperatively, and 100.0% (16/16), 93.1% (27/29) and 84.6% (11/13) were showed effective cases at 12 months postoperatively. Total and postoperative hospitalization in VLAP group were shorter but duration of the postoperative balloon catheter was longer than conventional TURP group.
Although TURP remains standard surgical treatment for BPH, VLAP is attended with less morbidity and made a similar clinical effect compared to TURP. VLAP in conjunction with TURP may result in less risk of postoperative urinary retention and vesical irritability.

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A comparative trial of 85 patients with Benign Prostatic Hypertrophy was performed, treating them with a YAG Laser system, Optica 60Z (made by Xintec, USA) and Rotalase fibers. This series was composed of 55 patients treated by VLAP only (A Group) and of 30 patients who underwent a combined therapy of laser application followed by an additional TUR-P (B Group). Both groups gave effective results of treatment. To be noted especially is that B Group presented an earlier post-operative improvement in AUA symptom score, maximum flow rate and post-void residual urine. The laser-assisted TUR-P proved thus to be a faster and more radical technique than the VLAP monotherapy.

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