The most ideal operation for primary and metastatic lung tumors must give both preservation of good pulmonary function and high curability. As diagnostic technigue and chemotherapy for malignant neoplasms have advanced recently, new operative procedures should also be devised. To cope with these changes, we developed new operative methods using neodymium: yttrium-aluminum-garnet (Nd: YAG) laser for primary and metastatic lung cancer. First, we developed so-called “radical laser segmentectomy.” Since 1988, we have performed this procedure for 18 patients with T1N0 non-small cell lung carcinoma (NSCLC). This innovative operative method consists of a combination of anatomical or nonanatomical segmentectomy by Nd: YAG laser parenchyma sparing with complete hilar and mediastinal lymph node dissection. The median follow-up periods are 24 months, and all but one patient who had radical laser segmentectomy are alive and disease-free. That one patient is alive with cancer recurrence in mediastinum. Second, after 1986, the Nd: YAG laser has been used for 41 patients with multiple lung metastases in order to preserve as much pulmonay tissue as possible and achieve optimal resection of the lesions. Median sternotomy was adopted for 27 of these 41 patients. As a result, 732 metastatic lesions were resected or evaporated in 54 thoracotomies out of these 41 patients. The five-year survival rate was 51%. Although our study was not randomized, survival of those patients who received laser surgery tends to be longer than survival of the 28 patients for whom the Nd: YAG laser was not used. In conclusion, Nd: YAG laser is thought to be a very useful method to preserve normal lung tissue and to obtain high radicality. These procedures will be conducted to extend indication of limited surgery to intentional cases with early lung cancer and to multiple lung metastases from various sites.

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In order to obtain complete decompression of the cervical cord in the anterior approach for cervical spondylosis and/or ossification of posterior longitudinal ligament (OPLL), reactively thickened posterior longitudinal ligament must be removed after removing the osteophytes. This procedure, however, is not easy because the deep and narrow surgical field obliges the operator to use the scissors vertically to the ligament behind which dura and spinal cord is closely placed. Particularly in the case of OPLL, bony tissue involved in the ligament makes it more difficult.
On the other hand, a hard and fibrous tissue like this is a good indication of the carbon dioxide laser, especially when the target is placed vertically to the direction of the laser beam. The most important point is that the spinal cord behind the ligament should be completely protected from laser irradiation. For this purpose, we devised a special handpiece. A small spoon which is bent rectangularly at the neck is attached to the outlet of the handpiece. The tip of the small spoon is inserted between the ligament and dura through a small incision made on the ligament. The ligament is softly lifted up by the tip to make some space between the heated tip and the dura while lasing.
We have tried this new device in three clinical cases. In every case, the thickened ligament with or without bony tissue was effectivery and safely removed. We believe that such a little device will expand the indication of the lasers.

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Between 1979 and 1991, three hundred and sixty-five patients with biopsy proven cervical intraepithelial neoplasia (CIN) with satisfactory colposcopy were treated with the carbon dioxide laser in an outpatient setting and 293 have been followed for one year to 12 years after the laser vaporization. There have been 43 treatment failures, of which 56%of the patients had the second lesion detected during the first year of follow-up. The second lesion consisted of 22 mild dysplasias, 14 moderate dysplasias, 4 severe dysplasias, and 3 CIS. In 6 cases, the grade of the second lesions were higher than that before the laser treatment. There have been no case diagnosed as invasive cancer after laser treatment. The estimated 5-year remission rates calculated by Kaplan-Meier methods were 81.6%for mild dysplasia, 8 2.2%for moderate dysplasia, 82.6%for severe dysplasia and 92.0%for CIS. Of the 43 failures, 11 of the lesions disappeared spontaneously, 26 were treated with repeated laser vaporization, and 6 were treated by conization and/or hysterectomy. Four of the patients with repeated laser recurred and were treated by conization or TVH. All the failure cases have been followed for more than one year after the last treatment and found to have no evidence of disease. Consequently, 283 of 293 cases (96.6%) have been managed satisfactorily by laser treatment alone at outpatient setting. No patients experienced postoperative infection or bleeding requiring hospitalization. These results reconfirm the efficacy and safety of laser vaporization for all form of CIN.

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Between 1985 and 1992, the CO₂ laser conization was used to treat and diagnose 212 women who were diagnosed by cytology studies, colposcopy and biopsy examination to have dysplasia, carcinoma in situ (CIS) and microinvasive carcinoma (MIC). One hundred forty six patients (69%) were performed laser conization in the outpatient unit. One hundred forty eight patients(70%) after conization were followed up by cytology, colposcopy and histology, and 3 moderate dysplasias and koilocytotic atypia (3%) were recurred from 3 patients with CIS and a patient with severe dysplasia, which had been treated by laser conization. One moderate dysplasia and koilocytotic atypia were treated by following laser vaporization. Two moderate dysplasias were treated by following transvaginal hysterectomy and disappeared following cervical biopsy. In 88 follow up cases of CIS and MIC with negative surgical margins, only one case showed moderate dyaplasia 3 years after laser conization. In 18 patient treated by subsequent hysterectomy, who were diagnosed as CIS and MIC with negative surgical margins by pathologic examination of conization specimens, microscopic examination of the hysterectomy specimens revealed moderate and mild dysplasias, but not CIS and MIC. From these results, CO₂ laser conization was a highly effective method for treating cervical intraepithelial lesions and had the added benefit of preserving reproductive function and anatomic integrity. We considered that laser conization could be a therapeutic procedure when both surgical margins of CIS and MIC are negative.

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Two hundred and forty patients with condyloma acuminatum (vulva: 128, vagina: 2, cervix: 18, multiple: 28), 51 with Bartholin's cyst and abscess, 5 with Skene's cyst and 8 with benign vulvar tumor were treated with various lasers (Nd: YAG, CO2, YAG/CO2, KTP/YAG lasers). All patients underwent on an outpatient basis with local anesthesia. Their final cure rates showed 93.1%, 73.2%, 44.4%, 70.0%, 100%, respectively. The patients with residue and/or recurrence of condyloma revealed 17 (56.7%) sexual partners with the same disease and 13 (43.3%) partners without the disease. On the other hand, the patients without them revealed 63 (56.3%) partners with condyloma and 49 (43.7%) without it.
Fifty six patients were also treated with anti viral drugs (Idoxuridine, Aciclovir, Vidarabine, Podophyllin, Fluorouracil) before and after the laser therapy. The laser treatment, especially with the CO2 laser, has been suggested as a promissing therapeutic method for vulvar and vaginal disease on an outpatient basis.

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We have performed some procedures of laparoscopic laser surgery with KTP/532 laser. All procedures were observed under video contrail with 3CCD camera.
Using 5 to 15 watts of power from KIP/532 laser, a linear incision was made in the ovarian capsule and wall in ovarian chocolate cyst. After evacuation of bloody content, the cyst wall was completely removed. Filmy peritubular and periovarian adhesions were easily vaporized with KTP/532 laser. With more dense, vascular adhesions, the injury of adjacent tissue was minimized by KTP/532 laser system. The ablation of uterosacral ligament was performed on the posterior portion of ligament adjacent to uterine cervix.
These all procedures tends to save patients time and discomfort. These complaints of all cases were immediately disappeared about 70-80% after laparoscopic surgery. The laparoscopic laser surgery is more effective and minimum invasive treatment for benign gynecologic disorders.

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Rescently laser surgery has been done for sterile patients in Gynecology as well as the cholecystectomy in Surgery. Surgical treatments for sterile patients are classified as follows; the tubal surgery, including the anastomosis and the salpingostomy, adhesiolysis, enuclation of fibroid, repairment of uterine anomaly, ovarian cystectomy, puncture and absorption of ovarian cyst, operations for polycystic ovary syndrom. Except for sterile patients ectopic pregnancy and microfertilization techniques are also use laser to make them more easy and conbinient.
Advantages of laser surgery are treatable to the minutest details, to be used under endoscopies and under microfertilization. In operations for sterile patients laser is especially useful for microsurgical tubosurgery like as uterine cornual-ithmic anastomosis, ithmic-ithmic anastomosis and fimbrioplasty because these operations are done to the minutest details under microscope. But disadvantages are unsuitable for rough surgery, to be needed quite expensive and big instrument. Also operator should use some special glasswares as well. In another hand, endoscopic surgery is going to be very popular in operations for sterile patients and endpmetriosis patients with laser. In endoscopic surgery minute cechniques are required because these operations are not so easy to perform for general gynecologist. In those endoscopic operations laser is quite useful.
In this paper rescent progressive laser surgery for sterile patients are discussed with our experiences and some reports.

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Scanning laser ophthalmoscope (SLO) has two advantages over conventional fundus camera to produce fundus image. One is scanning system of laser beam, which is weak enough for the safety of the retina, and the highly sensitive detector. The other is the confocality and the dark field view, which is produced by the aperture in front of the detector. The confocality increases the contrast of the picture. Three kinds of laser (argon, helium neon and diode lasers) are available for the scanning laser beam. Each of these lasers has its own characteristic in intraocular permeability. Argon laser is good at visualizing the changes of vitreioretinal surface and retinal nerve fiber layer. Herium neon laser offers better visualization of neural retina. Diode laser enables us to see choroidal vessels. These lasers enable fluorescein and indocyanine green angiographies with suitable filters. SLO is expected to offer psycophysical and electrophysiologic tests in the future.

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Laser therapy plays an important role in the ocular hypotensive therapy for various types of glaucomas.
Laser trabeculoplasty (LTP) and laser iridotomy (LI) are time-honored, well-established treatment. Experiences gained in the past decade clearly demonstrated that LIP is supplementary to medical therapy in the treatment of primary open-angle and capsular glaucoma. The ocular hypotensive effect is generally remarkable for one year or so. However, thereafter it decreases over time. Thus, the decline of therapeutic effect should be taken into consideration when the indication of LTP is considered. In contrast to LIP, LI is a real breakthrough in the glaucoma therapy. Surgical peripheral iridectomy, which has been practiced for more than 120 years, has been completely replaced by LI.
The new laser glaucoma therapy includes cyclophoto-coagulation (CPC) and ab interno or ab externo laser sclerostomy. The results of CPC using free-running or continuous wave Nd: YAG laser have been generally disappointing. Newly developed diode laser with wave length of 805nm appears to be more promising.
Ab externo laser sclerostomy with THC: YAG laser has first made quick, reproducible sclerostomy possible. Although the technique is relatively easy to master, the management of the incarcerated iris and the suppression of bleb scarring are particularly important for a functioning bleb formation.

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Atopic dermatitis (AD) is one of the common chronic skin diseases in which a variety of immunological disturbances have been described. Cyclosporin A, gamma interferon, and interleukin 2 were recently suggested for the management of the disease. They all act on some component of the immunological mechanism which provoke eczematous reactions. But because of side effects, we do not use these therapies as our first choice. Steroid ointment is still widely used for the treatment of AD. Steroid rosacea somtimes appears during the prolonged application of steroids. In the present study, we used a GaAlAs 830nm diode laser for treatment of patients with atopic dermatitis. Immunohistological examination was also performed before and after LLLT. The following results were obtained. 1) Itchy sensation decreased in 79 of 112 cases (71%) after this therapy. 2) Skin eruptions improved in 69 of 112 cases (62%). 3)There were no side effects during and after LLLT. 4) Major histocompatibility complex (MHC) class II antigen and intercellular adhesion molecule (ICAM)-1 expression on epidermal cells decreased after the therapy. 5) The number of CD1 positive epidermal dendritic cells did not significantly change before and after LLLT.

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The Q-switched ruby laser has been demonstrated to provide selective photothermolysis of pigmented tissue at a wavelength of 694nm and a pulse width of 30ns with dermal penetration. It was used to treat 114 patients with nevus of Ota with an age range of 8 to 63 years. Other methods of treatment for the nevus of Ota have either left scarring or were ineffective. In most cases, the entire area was treated at an energy fluence of 6 J/cm2 in each treatment session. Treatment intervals ranged from 3 to 4 months. The clinical efficacy of this laser treatment was evaluated in a comparative photographic analysis. Five treatment response levels were established according the percentage of pigment lightening of the original color excellent if there was more than 70% lightening; good from 40 to 69%; fair from 10 to 39%; unchanged if there was not a lightening of at least 9%; worsened if there was 10% darkening. Of the 23 patients who received only one treatment, good responses were achieved in 3 (13%), fair in the 13 (57%), and unchanged in 7 (30%). Of the 25 patients who received two treatments, excellent responses were achieved in 2 (8%), good in 16 (64%), and fair in 7 (28%). Of the 31 patients who received 3 treatments, excellent responses were achieved in 4 (13%), good in 26 (84%), and fair in 1 (3%). Of the 17 patients who received 4 treatments, excellent responses were achieved in 15 (88%) and good in 2 (12%). Excellent responses were achieved in all 18 (100%) patients who received more than 5 treatments. No hypertrophic or atrophic scarring was noted in any of the patients. However, transient postinflammatory hyperpigmentation of 2 months' duration was noted in a few patients. Q-switched ruby selective photothermolysis appears to be an effective and safe method of lightening or removing nevus of Ota.

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At 6 months after treatment of ten patients with Dye Laser, followed by the application of 5% Hydroquinone Monobenzyl Ether Cream and Sun Shade Cream, the results were either good or excellent in 80.0%, fair in 20%, although the number of patients and the periods of observation after the treatment were very small.

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In plastic and reconstructive surgery, various models have been employed for flaps. But distal end necrosis is entirely due to inadequate dlood supply, arterial inflow and venous outflow. We have use various method that improving the blood circurasion. Since 1983, we have used low powered Ga-Al-As diode laser in improving the vasculer circuration on flap survival in rat models and clinical cases. Caudal based random pattern flaps were raised on the back of two groups of male Wistar rats. 30 animals in each group. One group acted as control, with no irradiation. The second group received radiation from diode laser (830nm, 20mW, 60 sec.) on the flap base in the non-contact·method. Immediately after irradiation, a fluorescein test revealed a longer dye distance in laser group than in control. Seven days later, the laser group also showed the longer survival length. On the second rat model, axcial pattern flaps were raised on the abdominal wall of two groups. 20 animals in each group. One group acted as control. The second group was irradiated diode laser (830 nm, 60mW, 60 sec.) on the flap pedicules. Laser doppler readings were taken before and after each irradiation session. Both blood flow and mass showed a significant increase following low powered diode laser irradiation and seven days later, the laser group showed greater survived area than the control group.
The clinical applications of diode laser were for the enhanced healing of ulcer ornecrosis on the distal end of flaps. The patients who had the questionabule take were given diode laser irradiation (830nm, 60mW, 10 minutes) that was applied in the noncontact method to the pedicule of the flaps and around necrotic area. In all cases both blood flow and mass showed an increase. 10 incidents of possible necrosis were treated in 10 patients. Five patients were showed good take and recovered in 10 to 30 days. Five patients were required surgical operation, a small ulser was seen on the distal end of flap. Diode laser irradiation is effective raethod that stimulate flap survival and vasculer circulation.

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Effect of the Combined Laser Therapy (CLT) to nevus cellnevus was investigated. Four defferent CLTs were performed; 1)Irradiation of Pulse Laser immediately after laser epithelial peeling, 2)Irradiation of Pulse Laser immedeately after CO₂ laser and Nd-YAG Laser vapolization and laser mass reduction, 3)Irradiation of Pulse Laser after epithelium formation on the wound of laser epithelial peeling,and 4)Pulse laser irradiation after epithelium formation of the wound of laser abrasion.
Results
1) Effect of CLT1 was 65.7%
2) CLT2 was effective in lentigo and some special cases
3) Effect of CLT3 was 20%
4) Effect of CLT4 was 50%
Conclusion
In CLT1 and 2, damage of the tissue was large, and, therefore, sufficient effect was expected. Scar formation was very slight. It was plausible that the simultaneous LLLT effect of the pulse laser was combined and the wound healing was reinforced. Therefore, nevus was expected to be treated with CLT1 or 2 without scar formation which was undesirable from a cosmetic view point. CLT1 and 2 were more effective than 3 and 4.

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Since strawberry hemangiomas (SH) involute spontaneously by 5 to 6 years of age, wait and see policy is usually indicated. But SH are not completely regressed leaving capillary dilatations and subcutaneous tumors actually in almost all cases. Especially remained atrophic skin surfaces and fine wrinkles are not able to be repaired completely by surgical techniques. To prevent these secondary deformities we proposed early-stage laser treatment with pulsed dye laser and Nd-YAG laser within a suckling age.We started to treat as soon as the SH could be fined out. The earliest case was 6 weeks after birth. The purpose of this study was to investigate the of of the early laser treatment for SH in infants. The SH are devided into capillary hemangiomas (CPH) and cavernous hemangiomas (CVH); CPH are mainly located in the dermis, and CVH are in the subdermis. CPH were treated with the pulsed dye laser (585nm, 450μsec), and CVH were treated with the CW Nd-YAG laser. CW Nd-YAG laser was irradiated by two methods according to volume of the CVH lesions,which are transcutaneous irradiation for slightly elevated SH and percutaneous bare-fiber insertion for markedly elevated SH. Ulcerated hemangiomas were treated by low reactive level laser therapy (LLLT) using Nd-YAG laser. Consequently the early treated SH using combined laser therapy were involuted promptly as compared with the naturally regressed SH without any secondary marked deformities. Further we emphasize the need of ultra-early laser therapy of SH starting within 4 weeks neonate before proliferative growth phase, since markedly enlarged SH can not involute completely.

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The effect of the laser beam on the tooth structure is principally due to an acquired resistance against acid decalcification of human enamel. We have demonstrated that, of 9 different kinds of laser, the normal pulse Nd: YAG laser is the most suitable for acquired resistance of human enamel. The glazed surface of the enamel was observed immediately after the laser irradiation with an energy density of 47J/cm2. The acid resistance of the lased enamel was observed even after etching in an acidic solution. This means that the surface structure of the enamel still persisted after the acid treatment. In treatment with laser irradiation and fluoride application combined, the enamel treated with an acidulated phophate fluoride (APF) after the laser irradiation obtained the most remarkable acid resistance compared with the other treatments. In this case, the inhibition of calcium dissolution from the enamel was more than 90% (Fig. 1). This level of inhibition has never been approached before. A possible mechanism of the acid resistance of enamel was proposed. In the clinic, sensory responce of 11 subjects during the laser irradiation is summarized (Table 1). Among the 11 subjects, 9 felt a warm sensation during the irradiation, one felt a transient pain, and one felt an impact sensation. The laser beam was also applied at the surface of incipient caries. The black paint almost completely disappeared after the laser irradiation. Then the lased enamel was treated with APF. No visible expansion of the lesion was observed for 24 months after the laser and fluoride application.

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When the pulps of young human teeth have been exposed by dental caries or traumatic fracture, pulpotomy, rather than pulp capping, is recommended as an intermediate treatment. Although surgical instru-mental intervention and the pharmacological side effects of medicaments or capping agents invariably produce some tissue damage, the crucial requirement for successful pulpotomy is to minimize the trauma inflicted on the pulp during the treatment procedure. Throughout the operation, the maintenance of asepsis is also important to avoid infection.
The laser has many desirable characteristics when used as a surgical cutting instrument. The effects of ruby laser beam irradiation on the dental pulp tissue have previously been reported by Adrian et al. (1971). The advantages of the carbon dioxide laser over other lasers are that first bloodless tissue incision can be attained at a practical cutting speed, and second the edge of the laser-irradiated tissue is covered by only a thin layer of necrotic and carbonized tissue. As the laser beam has no mechanical contact with the tissue, the incision is made without inflicting mechanical damage on the remaining pulp tissue. Furhtermore, the operation is performed under aseptic conditions. Thus it may be possible to sever the dental pulp by carbon-dioxide laser without causing hemorrhage, mechanical damage or bacterial contamination, in which case the success rate of vital pulpotomies will be improved.
Up to now the delivery of carbon-dioxide laser beam is very difficult. Recently the suitable fiber for carbon-dioxide laser irradiation is developed. So the pulpotomy operation becomes easy and certain.

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A low power Nd: YAG laser. with a flexible fine optical fiber has been developed for dental use. To investigte the possibility of application in periodontal treatment, the following studies were made.
The purpose of the first study was to determine which laser energy setting resulted in the best condition. Periodontally-involved extracted teeth with subgingival calculus were used. The tested energy settings were 1.5W, 2.0W, 2.5W and 3.0W. Results obtained were as follows: The efficiency at 1.5W irradiation was significantly lower than that at 2.0W, 2.5W and 3.0W. There was no significant difference in efficiency among 2.0W, 2.5W and 3.0W irradiation.
The purpose of the second study was to reveal the effect of laser irradiation on inactivation of endotoxin artificially adsorbed by the healthy cementum and whether the inactivation of endotoxin spread or not by laser irradiation. After collagenase treatment, the healthy cementum was soaked in endotoxin solution. Energy settings were 30mJ for 2sec, 30mJ for 4sec, 50mJ for 2sec and 50mJ for 4sec. The results showed that endotoxin was inactivated at the irradiated spot at an energy setting of more than 30mJ for 2sec. Inactivation of endotoxin was also observed surrounding the spot.
The purpose of the third study was to investigate the clinical effectiveness of laser irradiation in the periodontal pocket. 16 pairs of periodontal pockets with a probing depth were more than 5mm were selected for the study. One irradiated by laser and the other served as controll. Energy setting was from 1.75W to 2.25W at 20pps. The results showed that gingival crevicular fluid and probing depth were significantly redused in the experimental group. And pus discharge disappeared significantly in the experimental site.
These results may confirm that laser treatment is effective in the treatment of periodontal disease.

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Studies of the light properties of hard tooth tissue established the infrared and Ultraviolet regions of the spectrum which are absorbed by dentin (1981, the Japan Society of Conservative Dentistry.)
These studies show that dentin and enamel absorb light in the regions of the spectrum around 3μm and 10μm. Water also absorbs light in the 3μm region.
The Er: YAG laser is effective in the 3μm region and the CO₂ laser in the 10μm region. However, the CO₂ laser has a clinical drawback: it causes heating which cracks the tooth surface. This makes the Er: YAG the best possibility for clinical applications. (1990. The Japan Laser Dental Society.)
It has also been show that the Er: YAG laser removes hard tooth tissue through the micro-explosive reaction of the 00H-Stem of the hydroxy apatite the hydration shell inside the crystal is instantly vaporized.
Our laboratory is getting good results with the clinical application of the Er: YAG laser delivered with a special contact tip developed here. The complete absence of pain during the procedure is especially noteworthy.

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As topics of laser therapy in oral and maxillofacial surgery, the indications by both of high-energy and low-energy laser will be pointed out, but here we would like to state on the former. As objects for the therapy by high energy laser in oral and maxillofacial surgery patients, oral tumors originated from the mucosa, and its associated diseases, such as precancerous diseases, long-lasting mucous inflammations would be included. As malignant tumors, we treated mainly T1 and T2 squamous cell carcinomas and malignant salivary gland tumos, and a case of malignant melanoma of the upper jaw. We have used laser instruments by CO₂, YAG·CO₂ and Nd-YAG since 1984. These laser instruments were changed and improved according to the objects and time lapse. We examined histologically the characteristics of cutting function on the oral soft tissues among a usual surgical knife, electric knife and laser knife. The result showed that the laser knife made the wound healing with thin coagulating, necrotizing layer and closed blood vessels. The findings will be some proof for the minimized bleeding by laser surgery.
As researches by laser for future, we are examining the exima-laser, which helps to cut the bone, and trying to find out the role of YAG-laser on thermotherapy. Dr. Ono, one of our staffs, performed an improvement of the probe for the thermotherapy and investigated the differece of the sensibility between the tumor and the normal tissues of a rabbit tongue, in which VX7 tumor was implanted, by laser radiation. The unique findings of the research was a higher rate of the BrdU marked cells in the tumor than in the normal tissues on third day after laser radiation.
At last, our representative clinical cases with tumor and precancerous lesions treated by laser surgery were presented.

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Soldering has been chiefly used for jointing dental prosthetic materials. Titanium is very difficult to solder because it is highly susceptible to oxidation. The recent development of an infrared heater soldering system is expected to make titanium soldering easier. However, because this soldering system uses a solder different from the conventional solder, it may cause problems in the oral cavity such as low resistance to corrosion. Titanium soldering requires prior fixation with the investment material. Therefore, the author recently attempted laser welding of titanium. In this attempt, normal pulse Nd-YAG lasers (M801A and M802, NEC) were used. The weld strengths of titanium plate specimens obtained by two different welding techniques were compared. With a laser beam (70mm in focal distance, 0.8mm in diameter), two titanium plates (40×10×3mm), superimposed each other 2mm at the end, were welded either by lap seam welding or by spot welding under the following settings: pulse width, 4ms (for spot welding) or 3ms (for lap seam welding); output, 12.5J/P (for spot welding) or 6.3J/P (for lap seam welding). The load required to tear off the joint by pulling for the spot-welded specimen was 90kgf in average, while that for the lap-seam-welded specimen was more than 120kgf in average, where the breakage of the base metal often arose in the proximity of the weld. A major factor hampering the utilization of titanium for prosthesis is the difficulty in processing. If laser welding is introduced to titanium, the dental application of titanium will widen.

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Laser has been clinically used only for hemostasis under an endoscope in the early period since laser was developed in Japan in the late 70th. In our department it has been used mainly for endoscopic lithotripsy of bile duct stones and endoscopic treatment for gastrointestinal tumors. Because intra-operative PDT has been used recently as a new aspect of laser treatment, the significance was examined in this study. The clinical results of follow up study on esophageal cancer shows this therapy is effective for shallow cancer. Local recurrence of esophageal cancer somethimes occurs even in the case of n (-) or with the waide dissection of lymphnodes. The reason would be partly due to micro invasion in surrounding connective tissue. PDT would be useful for this residual micro invasion. On the other hand, as to rectal cancer, as the nerve-preserved method has been recommended in recent years PDT would be also useful for the nerve preserved area. In the study of seven cases of esophageal cancer the mean level of photo sensitive material was 2 times higher (117.4±28.5ng/100mg) in cancer tissue than in normal esophageal mucosa (66.7±12.8ng/100mg). This therapy has an advantage easily to use in an operating room compared with intra-operative radio therapy, However, the photosensitive material has a little bit of sideeffects, and more effective laser are not available. The prompt improvement and develop,ent are expecting.

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We studied the effectiveness of Nd: YAG laser endoscopic treatment for early gastric cancer. During the period between 1980 and 1991, 67 cases which were followed up more than a year were evaluated.
The rate of the effectiveness in all subjects was 76%(51/67). In the lesions without lymph nodes metastasis, the rate of the effectiveness was 95%(37/39) (IIa type less than 2cm: 94%(17/18), IIc type less than 2cm without converging folds: 95%(19/20), focal cancer in adenoma: 100%(1/1)). In the other type of lesions, its rate was 50%(14/28). The rates of effectiveness in the lesions more than 2cm in size and the lesions with conveging folds were 30%(3/10) and 50%(8/16), respectively. Therefore, the size and ulcerative findings of lesion were considered for the causes of ineffectiveness.
On the other hand, 3 out of 10 lesions treated more than two times showed effectiveness, but the other 7 lesions ineffectiveness finally. In the effective 3 lesions, the mean number of laser treatment was 2.3 times (2-3), and the period of treatment was 15.5 months (1.5-25). On the other side, in the ineffective 7 lesions, the mean number was 3.9 times (2-8), and the period was 30.3 months (2-83). In these ineffective lesions which showed recurrence repeatedly, we should know the limitation of laser treatment and select the other accurate treatment

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Surgical lasers provide a means for producing precise ablation of tissue associated with decreased mechanical trauma of surrounding tissue. as well as improved hemostasis, hence generally accepted as an advantageous tool in surgery. Spherical laser coagulation therapy, which makes a round coagulation inside the liver with a spherical radiation of Nd-YAG Laser fiber tip, is effective for the treatment of the liver cancer.
Preoperative simulation of the laser fiber insertion is important to avoid damaging important vessels in this therapy. Simulation of the needle puncture for the tumors in the liver were carried out with Computer Aided Surgery (CAS) system, which reconstruct the three-dimensional diagnostic model, from the set of sliced images, e. g. a x-ray computerized tomography and/or a magnetic resonance imaging. With this reconstructed model, the safety areas of needle punctuation was indicated in the open surgery, the PTLV (Percutaneous Transhepatic Laser Vaporization) and the Laparoscopic spherical laser coagulation.

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Since 1984 we have investigated a method of laserthermia using microprobe in experimental and clinical studies. We reported the advantages and week points of this method that were observed by long term clinical follow-up study, and pursued a new method of laserthermia using balloon for the purpose of overcoming the week points of laserthermia using microprobe. We obtaind the following results: 1) Pathological change of the gastric wall after laserthermia treatments for 18 preoperative patients with early gastric cancer indicated the satisfactory penetration effect and safety of laserthermia. 2) Except for one patient with depressed undifferenciated cancer, biopsy specimens after laserthermia treatments became negative for cancer on 13 inoperable patients aiming for complete eradication of cancer cells by laserthermia. But local recurrence was found on 3 patients who were followed up above 4.5 years after laserthermia treatments. 3) Laserthermia using balloon has several advantages as compered with laserthermia using microprobe.

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Since 1979, we began to study contact laser irradiation using of Nd-AG laser for gastric cancers, and developed contact probe. In 1984, we have studying experimentally the endoscopic Nd-YAG laser hyperthermia (named Laserthermia) for the gastric cancer using the interstitial probe and thermocouple (named double channel method). In clinical application with double channel method for human gastric cancer had several demerits. It was not easy to keep certain distance between interstitial probe and thermocouple due to peristaltic wave of the stomach. In this studies, a newly developed single channel method (named hybrid probe) was discussed. Hybrid probe will be applied to a general UGI panendoscope, and it was easy to keep certain distance during Laserthermia. Effects of Laserthermia using hybrid probe on the human gastric cancer transplanted to the nude mice were studied histologically. Tumor shows demarcated necrosis and note the small amountof residual cancer cells. We have applied endoscopic therapy to 79 cases, 91 leisios with early gastric cancer. The total residual cancer leisions were obeserved in 13 out of 82 leisions (15.8%) without 9 operation cases. We found the lesions under 1.0cm in diameter, there was no residual cancer with single endoscopic therapeutic method. In lesions over 2.0cm in diameter and/or submucosal cancers, endoscopic therapy should be necessary in combination.

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We compared an Nd-YAG laser (Model 8000: 1064nm; Molectron Medical) and a high-power diode laser (Diomed 25: 805nm; Diomed) in terms of tissue damage and subsequent cellular proliferative activity. We made a fundamental study on an appropriate injection schedule of 5-FU for the purpose of achieving higher concentration of 5-FU within tumor tissue in laser photoradiation. [Method] i) The gastric mucosa of dogs was continuously photoradiated for 1, 2, 3 or 5 seconds at a power of 10W or 20W and with the transmission fiber either in contact or not in contact with the mucosa. Thermal necrosis of tissue was compared by HE stain. ii) Gastric ulcers were induced in rats by contact photoradiation (20W/1sec.). BrdU (50mg/Kg) was intraperitoneally injected 1, 3 or 7 days after photoradiation. Two hours later, stomachs were resected, and the labelling index (LI) compared. iii) Colon 26 cells were transplanted to the abdominal wall of BALB/c mice by intracutaneous injection. Tumors were treated by contact photoradiation (20W/1sec.). BrdU (50mg/Kg) was administered intraperitoneally 3 or 7 days later. Tumors were resected two hours subsequently, and the LI was compared. iv) BALB/c mice with 10 mm tumor (caused in the same way as iii) were intraperitoneally injected with 5-FU (50mg/Kg). And the tumors were treated by contact photoradiation (10W, 1sec./total dose of 100J) of diode laser. We set the groups of (1) Control, only with 5-FU injection, (2) FL with laser photoradiation 5min. after 5-FU injection and (3) LF with laser photoradiation 30min. before 5-FU injection. We measured intratumoral 5-FU concentration respectively.

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We performed 215 laparoscopic cholecystectomies with YAG laser on the patients with cholelithiasis, choledocholithiasis, cholecystic polyp and cholecystic benign tumor since April in 1991. The male was 37% (80 cases) and the female was 63% (135 cases). The average of the age of the patients was 50.8±12.4 years old (mean±SD). We tried to do the intraoperative choledochography in all cases to avoid the intraoperative misorientation in the biliary tract and to ensure the safety on the operation. We didn't get the intraoperative choledochography in the early 6 cases, but we could do the intraoperative choledochography in 100% of the recent 105 cases. The average of the operation time was 136±49min in the first 40 cases, 94±30min in the following 40 cases and 105±64min in the latest 135 cases (mean±SD, respectively). And the average of the amount of laser work was 2944±2167 joule, 1327±667 joule and 1570±1161 joule (mean±SD, respectively). We had 7 cases with severe adhesion around the gallbladder and with thick wall of gallbladder, but completed the laparoscopic cholecystectomy with the dissection of gallbladder from the fundus (so called von Fundus aus). We recognized the sharp dissection with YAG laser especially in these 7 cases, but we never forget we had the laser tip broken during the operation in 2 cases of the above 7 cases. In conclusion, laparoscopic cholecystectomy with YAG laser may be accepted much more commonly as a less invasive surgical therapy in the near future.

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Laparoscopic cholecystectomy (LC) has now become the first choice treatment for gallstones. Dissection of the gallbladder bed is importnat in performing the entire procedure successfully and several cutiting devices such as laser, electrocautery or harmonic scalpel are now applied. In the present study, the usefulness of laser for the dissection of gallbladder bed and lithotripsy of common bile duct stones was evaluated in 225 patients who had undergone LC and in 5 with common bile duct stones, respectively. Laser was used in 86 of the 225 patients, electrocautery, in 117, and harmonic scalpel in 22. Laser had effecient cutting and coagulation capabilities compared with the other two cutting devices, and it was consiedred to be an useful cutting device for LC. However, when the dissection layer was unclear, perforation of the gallbladder by laser occurred in 11 of 86 (12.8%), while electrocautery caused the perforation in 21 of 117 (18.0%), and harmonic scalpel, in 1 of 22 (0.5%). Although laser was considered to cause less tissue damage than electrocautery, its operation seemed rather difficult. In 5 patients with common bile duct stones, pulsed dye laser was used for lithotripsy. Laparoscopically, the cystic duct was exposed and a fine choledochoscope was inserted into the common bile duct through it. A fiber for laser guide was inserted through the scope into the bile duct and laser was fired at stones. In all the 5 patients, stones were smashed effectively. Small fragments of stones had disappeared completely during the operation in 1 patient, while some fragments still existed even after the procedure in the remaing 4. One of the 4 patinets had T-tube instituted by laparotomy and a tube wsa placed in the bile duct through the cystic duct (C-tube) in the remaing 3. In three of the 4 pateints, small stones disappered postoperatively and the other patient underwent endoscopic sphyncterotomy. Thus, laser was considered to be an important tool for not only the dissection of gallbladder bed but also lithotripsy of the common bile duct stones. However, improvement of the technique is necessary.

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The Nd-YAG laser was compared to the electrocautery in laparoscopic cholecystectomy. Eighty one cases were reviewed with thirty two patients in the laser group and forty nine patients in the electrocautery group. The operative time and the postoperative hospital stay were almost same in each group. Gallbladder perforation during the dissection of the gallbladder bed occured in 10 percents of each group patients. There were no difference in liver function at one postoperative day between two groups. Although the rate of postoperative complications was slightly high in the electrocautery group, the causes of complications were not related to the energy source. These results suggest that the laser is not superior to the electrocautery in laparoscopic cholecystectomy.

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Since July 1990, 750 consecutive patients with gallstones have undergone laparoscopic cholecystectomy. The overall results were satisfying, emphasizing the safety and efficacy of the new procedure laparoscopic cholecystectomy. 670 of 750 patients have undergone ablation of gall bladder by Nd-YAG laser and other 80 patients by electric cautery. In fundamenntal experiment, laser effected narrow and deep denaturalization, but on the other hand electric cautery effected wide and shallow denaturalization. In clinical data there was no significant difference between laser and electric cautery, but by laser we could ablate gall bladder more delicately than by electric cautery and then we think in cases of chronic severe cholecystitis we had better use laser because it is necessary to distinguish exact layer of ablation. Forty patients with common bile duct stones have undergone laparoscopic transcystic cholangioscopic lithotripsy (LTCL). In power of lithotripsy Alexandrite laser was inferior to Electrohydraulic lithotripsy (EHL), but in safty Alexandrite laser was superior to EHL.

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Low power He-Ne lasers (λ=632.8nm, 8.5mW, Senkou Med. Mgf. Co., Tokyo) have been used for the treatment of 159 painful out-patients (postherpetic neuralgia 83, herpes zoster 13, whiplash syndrome 9, rheumatoid arthritis 7, reflex sympathetic dystrophy 5, causalgia 5 cases, and etc.) and 12 patients without pain (facial palsy 7 and alopecia areata 5 patients). The effectiveness of the laser therapy in 159 patients is 81.8% by a four-grade evaluation. The degree of pain relief from postherpetic neuralgia is 44.6% after 50 treatments and correlated with the number of treatments. These results suggested that repeated irradiation with low power He-Ne laser is an effective and safe therapy for painful out-patients.
The mechanisms of analgesic effects of low-power laser were categorized into three systems; the first is the reduction of painful stimuli by the antiinflammatory effect, hyperpolarization of neural membrane potentials and the increase in local blood flow after irradiation of lasers, the second is the blocking effect of neural transmission and the third is the inhibition of the dorsal horn neurons. The mechanisms were discussed using results of our basic studies.

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Different types of laser powers or systems have been used to treat patients with chronic rheumatoid arthritis(RA). 65 inflammatory wrist joints from 49 RA patients were examined in this study. These wrist joints with motion pain were treated by 3 different types of Ga-Al-As diode lasers with 5 different power levels (10, 20, 40, 60, 100mW C. W.) and 6 different power densities. The effective ratio of the laser treatment was about 80% for all density levels. For an irradiation treatment with a duration of less than 15 seconds, the respective rates of effects were as follows: 100mW (27.3%), 60mW (I)(26.7%), 60mW (II)(35.0%), 40mW(11.1%), 20mW(3.4%), 10mW(0%). A inverse relationship was observed between the power of the laser and the effective time of irradiation, i. e., the higher the power of the laser, the shorter the effective time of irradiation. Laser power plays an important role in determining the degree of the pain-relieving effects. However, the rates of effect were not significantly different between the 60mW treated groups and the 100mW treated group. An inverse relationship was also observed between laser power density and effective time of irradiation. The laser beams with almost identical power densities but different powers didn't have the same effective ratio. The lower effective limit of energy desity might be about 10joule/cm2, and some laser beams with over 300joule/cm2 of energy density had almost the same pain-relieving effect. But over that dose biological inhibition is not the result. About 50% of all cases, irrespective of the type of laser used during treatment experienced pain relief for at least 48 hours after irradiation. Therefore, treatments on either an alternate-day basis or on a twice-weekly basis were determined to be effectively therapeutic.

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We have investigated fundamental action kinetics of low-intensity laser irradiation to living tissue as therapeutic procedure. Various kinds of laser therapies using low-intensity irradiation were reported. Some of them had been received wide recognition and become to be clinical therapy. However fundamental kinetics of therapeutic mechanism was not well-understood. The kinetics should be extremely complex due to stimulation effect, that is, the effect is extremely large comparing to irradiation light dose. In the other hand, there is a possibility of simple kinetics because low-intensity light reveals wide spectrum on therapies.
The temperature elevation of tissue and/or cell during low-intensity irradiation is small enough to deny contribution of thermal kinetics on therapeutic effect. Mitochondria are the major light absorber except blood erythrocyte and melanophore in the living tissue against visible light. Mitochondria are major energy production organella and its function is sensitive in temperature due to complex enzyme reactions. We therefore have one hypothesis of which light absorptions of mitochondria induce localized temperature elevation even tissue temperature elevation is small enough. We measured absorption spectrum of extracted rat liver mitochondria in vitro. We assumed adiabatic condition surrounding a mitochondrion to estimate the maximum temperature elevation. We calculated sufficient temperature elevation to change mitochondria function by the irradiation condition of normal low-intensity laser therapy. Our hypothesis is not denied by this results as a part of the kinetics, however further experiment is necessary to give precise conclusion. Since this hypothesis can not explain the wavelength dependence of our series of low-intensity laser effects, the different kinetics was suggested for different wavelength.

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It is necessity to have experimental animal models which have a tumor on the bronchus for the studies of photodynamic diagnosis and therapy of lung cancer. However, it is a quite hard work to devepole the malignant tumor in the animal bronchus experimentally. The VX-7 cell line, rabbit squamous cell carcinoma, is relatively easy to subculture and generally used in many studies. The aim of this study is to establish the methods how to develop the bronchogenic tumor in the rabbits using newly-developed ultra-thin fiberscope and to performe the photodiagnosis with this model. 15 Japanese white male rabbits weighing 3.5kg weight were used in this study. Under the general anesthesia with 50mg/kg intravenous pentobarbital, intubation was performed with 3.5mm cystoscope for infant. Inoculation of VX-7 tumor using TBAC needle under ultra-thin fiberscope. Fiberscopy was performed once a week. Three weeks after cancer cell transplantation, Photofrin was injected intravenously and fluorescence was examined with a 405 nm laser beam using an excimer dye laser fluorescence-image analyzer. All rabbits were sacrificed at 4 week after inoculation and performed histopathological examination. The fluorescence spectrum of Photofrin with its characteristic maximum peaks at 630nm and 670nm were obtained only in cancer lesions, while surrounding normal tissue demonstrated negligible uptake of dye. It is suggested that this model cancer of carina has been useful in photodynamic diagnosis, photodynamic therapy and their basic study.

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Mono-L-aspartyl chlorin e6 (NPe6) is a photosensitizer that possesses cancer affinity and is excreted from nomal tissues quickly.While NPe6 is exploitable for photodynamic therapy(PDT),it may affects the nomal tissues where NPe6 is over-remaining.To investigate the concentration of NPe6 in malignant tissues and nomal tissues in a mouse tumor model, we've made a fluorescent image analysis system by reconstructing an operating microscope. At 5 hours after administration of NPe6 20mg/kg body weight dose via the tail vein, both malignant and nomal tissues are excited at 405nm.The fluorescence of NPe6 is detected through a multilaminate interference filter that can select the fluorescent wavelength at 661nm or 664nm, -- the former is considered to be emitted mainly by free NPe6 and the latter by NPe6 which binds to albumin and the equivalent.The fluorescent intensity is changed into the concentration of NPe6 by a calibration curve.As a result,NPe6 accumulated in the malignant tissues 7 times as much as in the nomal one,that gives us much reliability upon PDT.

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This is the first report of perifocal brain edema levels of water-soluble pheophorbide-a (Ph-a-Na) comparing with experimental brain tumor levels.For this study,C-6 glioma was implanted into cerebrum of rats,and after about 2 weeks Tumors that grew into 5-7 mm in size and had perifocal brain edema were selected using Magnetic Resonance Imaging. Ph-a-Na levels of tumor region,edema region and normal brain region were analyzed by high-performance liquid chromatography (HPLC) at 4 and 12 hours following intravenous injection of Ph-a-Na.Tumor region level (P<0.05) and brain edema level (P<0.01) of Ph-a-Na at 4 hours were significantly different from normal brain levels of Ph-a-Na at 4 hours (Scheffe's method). At 4 hours after intravenous injection of Ph-a-Na, the tumor: normal brain ratio was 3.84, while the edema: normal brain ratio was 4.43. At 12 hours after intravenous injection of Ph-a-Na, each tissue levels of Ph-a-Na remarkably decreased from at 4 hours.This result indicates a rapid disappearance of Ph-a-Na from body.
These results indicate that at 4 hours after intravenous injection of Ph-a-Na, Ph-a-Na levels of tumor region and edema region are estimated as same on the whole, and much higher than that of normal brain region. This suggests that if photodynamic therapy ( PDT) using Ph-a-Na is applied to brain tumor which has perifocal edema,photochemical reaction which occured at edema region may be equal generally to tumor region.Some reports had been made about that perifacal edema may grow serious after PDT for brain tumor. The cause of this phenomenon may be led by similarity of concentration of photosensitizer between at edema region and at tumor region.

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Hematoporphyrin derivative has became the most popular agent for photodynamic therapy. However, vigorous studies are under way throughout the world to seek new photosensitizers with greater cancer cell affinity and less side effect. But no ideal photosensitizer has yet been found. ATX-S10 (molecular weight: 839.85) is a new photosensitizer. It is a chlorin derivative that has two asparginate side chains at the carbon of the tetrapyrrol rings via peptide linkage. Mono-L-aspartyl chlorin e6 (NPe6) is also a chlorin derivative and has been studied clinically in the U. S. A.. We measured spectra (absorbance and fluorescence) of ATX-S 10 with and without the addition of albumin and the result suggested that the albumin binds via an asparaginate residue of ATX-S10.

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HAT-D01 is a typical fluorescent diagnostic agent without phototoxicity because the exited triplet status is extremely short and the molecular structure has meta-phenylene spacer-bearing porphyrin hetero-dimers.
HAT-D01 in PBS was administered intravenously to tumor bearing Balb/C mice via the dorsal tail vein at doses of 80mg/kg body weight. The following tissues were removed: brain, lungs, heart, liver, spleen, intestine, kidneys, skin and tumors at 0.5, 1, 4 & 24 hours after drug administration using 3 mice per time point. Some points of various normal tissues and tumor were chosen and were examined by a new excimer pulse dye laser diagnostic system (Hamamatsu Photonics K. K., Hamamatsu, Japan) using a fiberscope to perform a time-series study of the uptake of HAT-D01 in the various organs and tumors.
The relative intensity of HAT-D01 in the various organs became optimal around 0.5 to 1 hours after i. v. injection at a dose of 80mg/kg. When the relative intensity of HAT-D01 from the tumor was set at 100%, at 0.5 hours after i. v. injection the intensity in other organs was as follows: skin 96%, intestine 52% and other tissues (brain, lungs, heart, liver, spleen and kidneys) below 1%. Therefore, the HAT-D01 in normal tissues except skin decreased gradually with time for up to 24 hours.
These results suggest that HAT-D01 may be useful for clinical photodynamic diagnosis (PDD) of tumors.

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We examined the distribution of interstitial temperature in the canine prostate during balloon laserthermia. The laser equipment (CL50FS, SLT Japan Co. Ltd) generated Nd: YAG laser (1,064nm) and the laser was irradiated over 360°cylindrically by laser balloon (2cm long) with circulation system of cooling water. By measuring the temperature at 3-5 minutes after the beginning of the treatment, we obtained following results. The temperature of the bladder neck and urethral sphincter maintained below 41°C except extreme conditions. The effect of cooling of the tissue is within 6mm and direct transmission of laser energy is within 10mm.

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In order to obtain basic data of combination effect of laser hyperthermia and PDT for cancer, the present study examined changes in ultrastructures of Hela cells subcutaneously implanted in nude mice immediately after the combination on PDT and laser hyperthermia (LH) and those immediately after PDT or LH alone, using morphometry. The mitochondrial volume densities significantly increased and the surface densities of the mitochondrial inner membrane decreased significantly after single treatment of PDT, LH and the combination of PDT and LH compared with the control. This may indicate that mitochondria are the primary target of the treatments. N/C ratios significantly increased in the treated groups; the ratio was highest in the PDT followed by LH group, in which tumor reduction rate 4 days after the treatment was the highest. In the treatments producing severer effects on tumor cells, mophological feature such as cytoplasmic, condensation appeared in the cells.

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A diode laser system is commonly used as a light source in pain control, but normally it is impossible to use the diode laser for PDT using a common photosensitizer, because it has a too high wevelength and lower laser power. Recently, Matsushita Industrial Equipment Co has developed a new diode laser system which is considered to have potential for PDT with NPe6, due to it's lower wavelength (664nm) and greater laser power. 1×10⁶(one times ten to the sixth) Meth-A fibrosarcoma cells were implanted subcutaneously in the back of four-week-old BALB/ c female mice. A week later, the diode laser was applied five hours after the intravenous administration of NPe6 to each tumor-bearing mouse. At that time implanted tumors generally reached 10mm in diameter and 5mm in thickness in size and the photoradiated field was adjusted 14mm in diameter. The diode laser was adjusted to 664nm wavelength to fit the absorption bands of NPe6. In the first study the rise of tumor temperature during PDT was measured. The different laser light doses were delivered: 0, 50, 100, 150 and 300mW/cm2. A 23-gauge thermocouple hypodermic needle was inserted at a depth 2mm from the tumor surface and intratumoral temperatures were documented chronologically.The average tumor temperature rise at 0, 50, 100, 150, and 300mW/cm2 was 0, 1.75, 3.80, 4.42 and 10.58°C rise during photoradiation. In this investigation our purpose was to examine the effectiveness of PDT alone excluding the effect of any hyperthermia, so in the second study the power of laser was fixed at 100mW/cm2, as this caused only a slight elevation in temperature, below the temperature range of hyperthermia. In the second study six groups of 10 tumor-bearing mice per group were treated with the diode laser 5 hours after the intravenous administration of NPe6 derivative at a dose 1.25, 2.5, 5.0, 7.5 mg/kg i. v. to each tomor-bearing mouse. Total photoradiation ranged from 0 to 150 J/cm2 and the dose rate of delivered light was adjusted to 100mW/cm2. Percentages of cures were determined from numbers of mice that were apparently disease-free 50 days following treatment. Conclusions run as follows: 1.PDT is effective in the treatment of implanted fibrosarcoma using a diode laser with NPe6. 2. We obtained tumor therapeutic effects by PDT unrelated to any hyperthermia effects. 3. The power of the diode laser beam was uniform in intensity throughout the photoradiated field.

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