Excimer lasers, color-center lasers of alkali halides, and semiconductor lasers of AlGaAs have become commercially available during the last decade. More recent lasers are discussed as follows:
1.1 Melles-Griot introduced a He-Ne laser with green output at 543.5nm wavelength into market.
1.2 A slab glass laser with a cw output of 140W was reported by the Institute for Solid-State Physics, and a cw power of 1kW is expected.
1.3 A monolithic semiconductor laser array with a quasi-cw power of 25W was reported by Spectra Diode Laboratories.
2.1 Tunable solid-state lasers of alexandrite, GSGG, sapphire etc. are making good progress.
2.2 The copper vapor and the gold vapor lasers are now commercially available, and finding medical uses.
2.3 Quaternary semiconductor lasers of InGaAsP is tunable in the near infrared, and InGaAlP is tunable in the red with a low power.
3. Experimental and theoretical investigations on soliton lasers, free-electron lasers, and X-ray lasers have been very active in the last few years. However, medical application of these lasers must wait for further research and development.

View full abstract

8

View full abstract

A compact laser spot scanner is developed for the treatment of port wine stain using Argon laser photocoagulator. The output end of the fiber is imaged onto the skin surface with a magnifying lens, and is driven by the electromagnetic force from several solenoids placed around the fiber end. The image spot of the end is scanned over the skin surface and forms one large spot.

View full abstract

A laser beam cross section is normally circular and has a Gaussian's intensity distribution. This nature often makes it unsuitable for treatment of hyperpigmented skin lesions. A square shaped uniform intensity distribution is required over the treated area. To overcome this problem, we have developed “Kaleidoscope” to get a square uniform distribution using a quartz square pillar.
This paper describes a theoretical analysis and practical results.

View full abstract

The in-depth laser irradiation therapy for irresectable liver cancers was developed. By puncturing the laser probe into a liver tumor and by irradiating laser energy on it, lesion can be necrotised. As to bladder tumors, PDT method was developed. In this treatment, inserting the laser probe into the cavity of bladder, laser is irradiated spherically all over the cavity of bladder. Treating cancers effectively using laser energy it is essential that laser beam to be irradiated from the tip of the probe should be distributed as uniformly as possible. A double tapered conical probe was designed by computer simulation and probe model was made and checked. The actual irradiation patterns of the probe was similar to those got by computer simulation and was able to obtain good results. Such animal experimentation as pig livers showed the probe could make almost spherical shape of protein coagulated.

View full abstract

We have treated pigmented nevi using mainly ruby laser installed with a kaleidoscope which uniforms the output. We use Nd-glass laser, having wave-length characteristics similar to Nd-YAC laser beam (Wave length: 1.06 μm), for this basic experiment, because it has superior permeability into tissue and in selectively absorbed into melanin pigment. The effect of each laser on animal tissues and the pigmented nevi is examined used ruby laser and Nd-glass laser having the same power per unit area.

View full abstract

We developed YAG-laser oscillator with auto-control system of intra-canal pressure of digestive tract.
We could keep intra-canal pressure of esophagus, stomach and duodenum stable pressure of 5mmHg, 10mmHg, 15mmHg and 20mmHg with use of this system.
So patients felt minor pain and abdominal distension in digestive laser endoscopy treatment. Of course, belch in endoscopy decreased remarkably.
We could use this system to the cases of old or young age without anti-cholinergics.
Occasionally, intra-canal pressure increased over 20mmHg in the laser endoscopy without this system.
So we concluded and emphasized that with this system laser endoscopy treatment will be more safe and sure without agony of patients.

View full abstract

Non-contact irradiation of Nd-YAG laser is sometimes difficult to keep a constant distance between the tip of the quartz fiber and the lesion. On these cases, the contact type of endoprobe is useful which is made of Al₂O₃ (artificial sapphire).
Because this probe is very expensive, we develop a new type of endoprobe which is made of polyacetal (-(CH₂-O)_n-). Its shape is similar to that of the temple bell. The inside of the endoprobe being in contact with the lesion is filled with the water and through it Nd-YAG laser beam is irradiated. On this study we examined histologically the effects of Nd-YAG laser on the gastric mucosa of the dog by using this new endoprobe. Even at 30 Watts the degenerative area by weak contact irradiation was not yet beyond the submucosal layer. On the other hand, the degeneration extended to the serosa by strongly pushing irradiation for 2 seconds at 20 Watts.

View full abstract

Using the Nd-YAG laser contact method with micro-tip for endoscopic therapy, we studied the change in the size of a tip accompanying an increase in irradiation.
We have performed a single irradiation three hundred times with a new tip (20W, 1.0 second duration) of a pig liver and a resected stomach from a gastric carcinoma patient. Before and after each irradiation, the power of laser transmitted the tip were calibrated by a power meter (Coherent®). And the size of each coagulated tissue was calibrated by micro-meter.
Our result indicated that the change in the size of coagulated tissue and the gradually lower power of the laser transmitted the tip were caused by the heat producted at the cloudy portion of the tip by failed laser transmission as well as by a wider beam arising from the laser reflex at this cloudy part of the tip.

View full abstract

Increased power densities of delivered light can produce elevation in tissue temperature during photodynamic therapy.
We have performed a study to measure the temperature of I. Argon dye laser, (630nm. 200mw). IIGold vapor laser (628nm. 1712Hz. 3.5W) and IIIExcimer dye laser (0.3mJ and 3mJ/puls 1~60Hz). Experiments were performed using FM mouse mammary tumor in mice In-vivo temperature measurements were obtained on anesthetized animals using digital multiple meter (Takeda Riken Co., Ltd).
The temperature of laser beam shows 57°C in Argon dye laser, more than 65°C in Gold vapor laser, rise 10°C in excimer dye laser (60Hz). The temperature of tumor shows 32°C in Argon dye laser, more than 55°C in Gold vapor laser, but no change can be seen in excimer dye laser. There are no difference between HpD injected mouse tumor to control tumor on temperature.
Histological change can be seen on the HpD injected mouse tumor irradiated by excimer dye laser. This shows photodynamic effectiveness without high temperature effect.

View full abstract

The change of tissue temperature on rat brain tumor during HpD-PDT was studied. An increasing of the temperature was dependent on the dose rate of the laser. That is, at the tip of an optical fiber inserted into rat brain tumor, the temperatures increased from 36.0°C to 42.0, 47.8 and 54.7°C when 100, 200, and 300mW laser light were delireved respectively. At the point of 5mm away from the tip, the temperatures increased from 36.0°C to 38.5, 41.0 and 41.5°C. A possibility of hyperthermal effect during HpD-PDT was suggested when the power of laser exceeded 300 mW/cm².

View full abstract

On and off endoscopic laser hyperthermia was carried out repeatedly with foot switch under the following conditions: power of 5 W; 5mm distance between wide divergent micro-rod and thermosensor; and temperature of 42-46°C maintained by thermometer. Hyperthermia was carried out on rat with experimentally produced liver cancer and on patient with pre-operative gastric cancer. Degeneration, necrosis, and tissue deficit occured on the irradiated area. U1-II ulceration developed on a normal canine gastric mucosa; therefore, it is difficult to be called a genuine hyperthermia. It is difficult for a person to maintain a definite temperature and a definite distance between micro-rod and thermosensor for a long period of time. Improvements must be made on the equipment.

View full abstract

Since 1984, we have been studying the experimental studies of endoscopic local hyperthermia with low power Nd-YAG laser irradiation by using frosted probe. In consequence, we developed the computed hyperthermia system. According to our studies, maintenance of the temperature at the therapeutic level (43-43.5°C) in the canine stomach was easy by using this system. When the distance between the frosted probe and the thermosensor stuck into tissue was about 6mm, tissue temperature was controlled to be nearly 43.5°C within an area from 10mm in diameter.
Experimental gastric tumor about 30mm in diameter in the beagle stomach was fade into a shallow ulceration gradually after 4 sessions for 10 weeks.
It was suggested in our studies that the endoscopic local hyperthermia (laserthermia) with low power Nd-YAG laser irradiation would be able to treat the gastrointestinal neoplasms.

View full abstract

We studied localized hyperthermia using contact Nd:YAG laser irradiation for tumors on nude mice, which were performed transplantion of anaplastic cell carcinoma obtained from human thyroid lesion. Twenty nude mice were divided into four groups; laser hyperthermia, cisplatin (CDDP) therapy, laser hyperthermia combined with CDDP and control. The new type of ceramics laser rod for localized hyperthermia was devised and used for transplanted tumors on animals. CDDP, 2.4mg/kg, was injected intraperitoneally each subject on the day before laser hyperthermia.
The interstitial laser hyperthermia was carried on for 20 minutes between 41.5 and 43°C. The results showed that laser hyperthermia combined with CDDP was most effective for inhibition of tumor growth in size. Laser hyperthermia without CDDP did not obtain so satisfactory treatment effect, as compared with combination therapy.
We applied this new method to eleven clinical cases with head and neck cancers Laser hyperthermia combined with radiochemotherapy reduced all malignant tumors.
We believe this new method of interstitial laser hyperthermia will be useful for treatments of head and neck cancers.

View full abstract

The therapy of soft laser (Stomalaser) was very effective in many cases of primary care (esp. in atopic dermatitis).

View full abstract

Hemangiomas are common congenital vascular lesions appearing mainly on the face, representing a disfigurement affecting many thousands of individuals. Multiple therapeutic modalities, including laser therapies, Argon, CO₂, Ruby, Diode lasers et al., have been utilized with success. There are many kinds of laser, each with its own characteristics. We have used for treatment such different lasers for different lesions and types. This report will present the experience in YAG laser therapy of hemangioma out of all.
MMB Model Nd-YAG laser with a 0.6mm silastic treatment portal and 0.1 to 3.9-sec pulse duration was used, set at 10 to 25J. 78 vascular lesions (hemangioma) were treated. These include hemangioma simplex, strawberry mark, cavernous type, teleangiectasia and others. We tried to achieved re-epithelization within 10 to 14 days. As a result, YAG laser used revealed the most effective, least damaging one for each case. Some authors reported that YAG laser therapy is less effective and worthwhile than Argon and other procedures concerning of light absorbent efficiency. However we have now recognized that this treatment with YAG laser is a beneficial and important method of curing, in particular in approaching the deep vascular area and protuberant type hemangioma. Furthermore, when we have used the method of marking spots with black ink on vascular lesions, it has enabled good response and greater absorption of light. We present if appropriate criteria are met, hemangioma can be successfully treated by YAG laser therapy.

View full abstract

We have studied clinically Nd-YAG Laser black specificity in the near infra-red region (1.064μm). Nd-YAG Laser could irradiate inside dermis without a damage of epidermis for the cases with nevus cell nevus and this was confirmed by electron microscopy. A series of low output irradiation of Nd-YAG laser may lead definite selective irradiation.

View full abstract

Although clinical results of argon laser treatment of cervical port-wine stain (PS) are generally good, it seems that its efficacy and its treating method are different according to its location, its size and its histological depth.
40 cases of cervical PS, which consist of 14 cases of anterior part of neck,22 cases of lateral part of neck and 4 cases of posterior part of neck, were treated by argon laser(6.8J/cm², pulse beam). Among various sizes of these 40 cases, 19 cases had large type of macule which is beyond two or more parts, and 21 cases had small type of macule which was within one part.
Consequently, good blanching results were obtained in 24 cases (60%). From the standpoint of the size of macule, good results were obtained in 16 cases of small type(76%), although no more than 8 cases of large type had good results (42%). Histologically 11 cases of large type (58%) had deeply located lesion in which argon laser treatment has its limit. On the other hand, 16 cases of small type (76%) had superficial located lesion in which argon laser is effective.
As mentioned on the treating method, PS on the anterior part of neck should be treated by argon laser using zebra method, because the skin on the anterior part is so thin that scar formation is tend to occur. On the other had, PS on the lateral and posterior parts of the neck can be treated uniformly by argon laser, because the wound healing of these parts is generally good.

View full abstract

We have applied endoscopic Nd-YAG laser therapy on four inoperable cancer patients. In 2 early IIa type gastric cancer lesions in two patients, with irradiation energy dose of 25775J. in 9 times (case 1) and 6260J. in 4 times (case 2), the local eradication was accomplished. In case 3, the patient with pyloric stenosis due to the advanced gastric cancer invasion had two months' relief of vomiting by 7093J.(in 2 times) of irradiation. In case 4, patient with a recurrence of metastatic lung cancer after pneumonectomy, 9416J.(in 5 times ) of irradiation relieved him of air-hunger for 6 months. We consider endoscopic Nd-YAG laser therapy is useful in tumor mass reduction for inoperable cancer patients.

View full abstract

6 Cases of various G. I.tract cancer have been treated with laser irradiation by using an endoscopic Nd-YAG laser equipment.A total of 6 cases, 3 with gastric cancer, 2 with esophageal cancer, one with cancer of bile duct were treated Post therapeutic evaluation was assessed by subjective symptoms or endoscopic findings including biopsy. About 2 cases with one esophageal and the cancer of bile duct, the therapy was insufficient. But in all the remaining cases, the therapy for the reduction of tumor mass and improving general status judged to be effective. In these cases, our technique is mainly used as palliative procedure to reduct tumor mass. But the possibility still remains for its application by the improvement of the technique and the equipment.

View full abstract

The occurrence of anastomotic stenosis is rare. However, when it once occurs, various symptoms such as nausea, vomiting and dysphagia appear, usually requiring a decrease in dosage or discontinuation of oral medication, thus causing serious problems. Various approaches have so far been devised, but there is no established treatment for anastomotic stenosis. In the present study, laser radiation was performed as a measure for treating anastomotic stenosis.
Subjects enrolled in this study were 13 cases in total, including 6 cases of whole gastrectomy for gastric cancer, 6 cases of esophagectomy for esophageal cancer, 1 case of esophageal dissection for esophageal varicocele, 1 case of cardiectomy for gastric submucous tumor, and 3 cases of low anterior resection for rectal cancer.
The laser used for these treatments was an Nd-YAG-laser which was endoscopically irradiated to the stenosed site at a dose of about 500-2000J. Because swelling appeared immediately after radiation, the oral dose was reduced temporarily but restored to the initial level within several days. Several repeated doses of radiation resulted in the increased oral dose and improved clinical symptoms. The results are reported in this paper with some X-ray and endoscopic findings.

View full abstract

After operation of esophageal cancer at lower part of esophagus,superficial esophageal cancer was left over at residual esophagus. We performed PDT to the residual lesion near the anastomosis,48 hours after injection of HpD.
After PDT we could see the ulcer induced by LASER irradiation,but the ulcer healed up 1 month after PDT. Now 1 year and 3 months after PDT, there is no finding of recurrence and bite biopsy of the lesion is negative.

View full abstract

Twelve patients with early stage gastric cancer were treated by photodynamic therapy. Haematoporphyr in. derivative was used as apphotosensitizer and an argon dye laser as a light source. On the basis of endoscopy, these cases were classified as type I (two lesions), II_a (three lesions), II_c (six lesions), III+II_c (one lesion). Complete remission was obtained in ten patients.
It is considered that an incomplete response in the early stage cancers is due to insufficient light dosage because of the wide area of tumor, because the site of the lesion is anatomically difficult to photoradiate and because the invasion extends to the muscular layer and serosa.

View full abstract

We have experienced Nd-YAG therapy for a total fo 53 early gastric carcinoma patients who had severe complications, between May. 1982 and September. 1986.
Excluding 9 patients who died, the 44 patients who were followed up in detail consisting of 53 lesions in total showed 47 lesions (88.6%) with no remaining malignant tissue. Mainly undifferentiated types of II_a+II_c or II_c+III, 16-20mm in diameter and in the mid-portion region showed remaining malignancy and recurrent lesions developed. 3 of these recurrent cases underwent operation. 3 cases plus 5 cases from a Nd-YAG therapy pilot study group underwent operation. These 3 operated cases which showed remaining malignancy allowed us to accurately determine the amount extent of irradiation and the optimum angle of beam incidence required for successful Nd-YAG therapy.
For patients with severe complications. Nd-YAG therapy should be the first choice for early gastric carcinoma.

View full abstract

According to our experience, Nd:YAG laser treatment probably achieves local cure in early gastric carcinoma if the lesion macroscopically presents itself as a “white scar” or even this scar disappears during endoscopic follow-up within six months after the last laser treatment.

View full abstract

During past 4 years 40 cases of small gastric cancer were treated radically by endoscopic techniques. The endoscopic treatment was classified tree groups, local resection by snare electro-cauterytechnique (mucosal marking-resection method), local tissue coagulation by laser and combined method of resection and coagulation. These resection technique is the best method because it is possible to examine histopathologically through the resected specimen. Whenever possible, a technique which allows the resection of cancerous lesion should be chosen over photocoagulation techniques, photocoagulation is only used to as a primary treatment when partial or total tissue resection is not considered feasible.
Under these application of laser, 1.32μm wavelength of Nd-YAG laser is very useful. The clinical effects of the coagulation properties of 1.32μm wavelength (B-line) compared to the conventional 1.06μm wavelength (A-line) were studied. We obtained the output power of 20 watts in B-line by replacing the laser millors. Three cases of early gastric cancer including a case of IIc type and two cases of IIa type were first treated endoscopically. The biopsies of all cases are negative for cancer during 3 to 6 months after phototherapy. It was observed that in our clinical studies B-line showed more distinguished effects which are limited in the superficial regions. Even if input and output efficiencies are low in B-line, it is useful because of having more strong coagulation and easer to control than A-line in the treatment of mucosal cancer, especially superficial depressed cancer without concern of perforation.

View full abstract

A comprehensive investigation has been made to develop a new technique for intraoperative laser welding of synthetic surgical sutures. These include nylon, polyester, polyglycolic acid (Dexon) and polyglactin (Vicryl). A black monofilament nylon has proved the best suture for carbon dioxide laser welding in terms of fusibility and joint reliability. Though laser fusion has markedly reduced tensile strength and strength efficiency when compared with conventional knotting, clinical trials have confirmed that a fused, 1-0 monofilament nylon, providing superior tensile strength to a knotted, 6-0 braided silk, can be used in safety for dermal wound closures. With technical improvements, laser welding may revolutionize surgical operations in the future.

View full abstract

The new method of arrest of hemorrhage from born marrow by YAG laser irradiation has been studied. By direct irradiation on the exposed bone marrow, laser is absorbed into flowing blood and does not form enough coagulated layer.
We made a instrument composed of a piece of glass-ceramics and its holder. Irradiation through the grass touched to the exposed bone marrow stopping blood flowing forms thin but enough coagulated layer.
Histological study showed irradiation through the glass damaged bone tissue less than direct irradiation.

View full abstract

From October 1985 to September 1986, twenty one patients who had anorectal diseases were treated with CO₂ laser and YAG laser at Nanasato Hospital.
14 had hemorrhoids, 3 had perianal abscess, 2 had fistula-in-ano, one had hidraadenitis suppurativa and one had rectal carcinoma.
Results were excellent and hospital stays were short.

View full abstract

To make certain the efficacy and security of Contact Nd: YAG laser conization of the uterine cervix, we examined the thermal influence on the neighboring tissues and organs during this procedure. Examination of the thermal influence was done with both continuous measurement of the temperature during the laser procedure and histological analysis. No thermal increases were recorded on the rectal and bladder surfaces closest to the uterine cervix. As for the thermal influence on the cervix uteri, within 2mm of the operational site irreversible histological changes occurred with temperatures rising to between 43 and 63°C. Sensors located more than 4mm from the operational site recorded temperatures ranging from 37 to 42°C, and histological evaluation later revealed reversible tissue damage.

View full abstract

Experiments irradiated by straight polarized light caused acceleration of wound healing. In case of using the right-hand circular polarized light, the first experiment showed that the effect was noticed on both the irradiated and non-irradiated side. However, in the repeated experiment, the effect was observed only on the irradiated side. However, there was no effect by the left-hand polarized light. Laser which was actually a straight polarized light was changed to a circular polarized light in a few cases. In this group, little effect was obtained by irradiating left-hand polarized light using 1.3μm laser diode, 514.5nm Argon laser or 632.8nm He-Ne laser. This finding strongly suggested that there might be a difference between the left- and right-hand circular polarized light on the heling of experimental wound. More informations on such a mechanism requires further study.

View full abstract

Argon laser (5w) was irradiated on the femoral bone of Wister rats. These rats were sacrificed on 1, 2, 3, 7, 14, 21 and 28 days from the beginning. Repair process of carbonized bone tissue was studied from the view points of histological observations.
Carbonization zone, Degeneration zone and Normal zone could be differentiated by H.E staining. On 1st day,no hematoma (fibrinclot) could be seen at the irradiated site. Fragmentation and absorption of carbonization and degeneration zone began on 7th day following invasion of fibroblasts. After 3 weeks, separation of carbonization and degeneration zone could be observed, but cartilago didn't appear yet. Appearance of cartilago and new bone trabecula was found at 4th week.
From this study, the repair process of carbonized bone delayed comparing to usual fracture healing. It is considered that defect of primary hematoma at the irradiated site and carbonization are concerned with delayed bone repair.

View full abstract

The authors' clinical application of Nd;YAG laser has proved that the severe mobility of loosened affected teeth wore improved remarkably. Then the authors examined the bone healing activation effect of lasers experimentally using the artificially formed bone wound on the femora of rats. The bone wounds were exposed to one of five kinds of lasers, CO₂ L., Nd;YAG L., AlGaAsL., He-Ne L., and Argon L., and the wound healing processes of lased bone and unlased bone were comparatively observed histologically. As the result, all four kinds of laser except CO₂ laser were confirmed to have bone healing activation effect. In addition to this experimental results the clinical evaluation for the bone heating activation effect of lasers is reported in this paper.

View full abstract

Deep brain irradiation with Nd-YAG Laser was experimentally studied in 36adult cats. The quartz fiber of Nd-YAG Laser with a convex tip was inserted into the thalamus and a spheric lesion was successfully made.
(1) Just after irradiation in acute stage four distinct zones (vaporized, carbonized, necrotized and edematous zones) were identified and no bleeding was seen in any zone.
(2) 12 hours later edema extended along the white matter.
(3) 24 hours later edema extended widely along the white matter and petechial hemorrhage was seen in the necrotized zone.
(4) 48 hours later: no changes were seen.
(5) 2 weeks later: gliosis containing macrophages were seen around the necrotized zone and edema was subsiding.
(6) 4 weeks later: vaporized cavity and gliosis with many macrophages were seen.

View full abstract

We have developed contact Nd-YAG laser technique which provides excellent incisional capabilities and minimal tissue damages. This study was undertaken to investigate the effect and healing of contact Nd-YAG laser irradiation in the tongue of rabbits and to compare it to other conventional scalpels such as CO2 laser and electric scalpel. This study confirms that contact Nd-YAG laser may offer specific advantages over other scalpels by histological and histochemical studies. Areas of the damaging tissues after contact Nd-YAG laser irradiation are much lesser than other two scalpels.

View full abstract

For studying the effect of irradiation with pulsed GaAlAs laser diode on wound healing especially granulation tissue formation, fullthickness skin defects surrounded by resinous rings were made on the back of rats and were irradiated with the laser every day Dry weight and collagen production of granulation tissue on 14 p. o. d. were more increased than controls by the irradiation at an energy density of 0.6J/cm². Pathological changes of the granulation tissue were described. Irradiation of pulsed GaAlAs laser diode may promote wound healing with a small energy.

View full abstract

The purpose of this study is to analyse the effect of soft laser irradiation objectively. Facial nerve of rabbit was damaged and irradiated by laser. The returning process of nerve function was analysed electrophysiologically. The result showed that the difference between the laser irradiation group and control group was not significant (p < 0.05), under this experimental condition.

View full abstract

The carbonized layer on living tissue in cutting by KrF excimer laser (wavelength: 0.248 um) was experimentally observed to be much less than that by CO₂ laser (10.6 um). The results of temperature measurement near the laser-irradiating region supported the presence of the carbonization on cutting surface. This carbonization would be caused by the thermal effect, which is strongly dependent on absorption process and thermal diffusion. These are related to the laser wavelength and the pulse interval time.
In KrF excimer laser, cutting without thermal disturbance would be possible under the conditions of long pulse interval, etc..

View full abstract

Our previous studies have shown that the irradiation of He-Ne laser for 2 min per day and 5 days per week inhibits the deposition of supra-gingival plaque in hamsters, which depends on bactericidal effect of the laser. In this report we examined the effect of lesser frequency of irradiation for the purpose of practical application.
Laser used was SOFT LASER 632 (MAINFAR, FRANCE), with a wave length of 632.8 nm, and out put energy 6 mW (CW). Twenty four male golden hamsters were maintained in the diet #2000 and deionized water during this experiment. After four weeks these animals were divided into two groups, A and B. Group A was irradiated in the same conditions of the previous study.Group B was for 3 min once a week. The irradiation was continued for four weeks. Right mandible molars were irradiated, and left side was a non-irradiated control. After irradiation plaque deposition was recorded with periodontal chart (Johansen E., 1952) and calculated by computed digitizer.
As a result, inhibitory effect of plaque deposition was observed in group B that is an irradiation of once a week. It is considered that He-Ne laser would be a useful tool for plaque control in dental practice.

View full abstract

The effect of He-Ne laser (low-power) radiation on the wound healing of guinea pigs skin were studied in connection with three items; such as (1) collagenic hydroxyproline contents, and (2) DNA contents in the tissues, and (3) histological findings, by comparing the group treated by laser every day with untreated group.
The following results were obtained. (1) The contents of hydroxyproline in treated group after three days of incised wound was significantly lower than that of control (untreated) group. (2) The maximal contents of DNA in the treated group was recorded at the third day, and untreated group showed a peak at the fourth day. (3) From the histological findings, increase of fibroblastic cell number were observed on treated group at the third day, but there was no difference of density of collagen between both groups.
These results suggest that the low-power laser radiation accelerated composition of type III collagen for incised wound healing.

View full abstract

Using low-energy Ga-Al-As diode laser, temperature of normal tongue surface of mice were examined. As the results, pathologically specific changes were not observed. On the other hand, temperature of tongue was increased immediately after irradiation and continued longer as well as control.

View full abstract

Using low-power Ga-Al-As diode and He-Ne gas lasers, cell DNA synthesis of mouse fibroblast cells ( NIH/3T3, MEF/NFS) were examined. As the results, lasers didn't stimulate the cell DNA synthesis.

View full abstract

The aim of this study is to evaluate the efficacy and safety of endoscopic PDT with HpD and Argon-dye laser for adenoma of the colon as a local curative procedure. PDT was attempted in 9 adenomas (7 patients) of the colon ranging from 10 to 55mm in size. The effect of PDT was examined histologically in one case. In the remaining cases, the local curability was evaluated by endoscopic follow-up. CR by the initial PDT was obtained in 4 lesions, all of which size was less than 20mm in the largest diameter. The effect of the majority of colonic adenomas more than 40mm in the largest diameter was partial and required additional PDT combined with piecemeal snare-ectomy and Nd: YAG laser. No serious complications were encountered, but luminal narrowing was complicated in one case. The preliminary data indicated PDT was effective to colonic adenoma. The technical difficulty of administering sufficient light en-face was a major cause of incomplete treatment. PDT will be an available method as a local curative procedure for the patients with broad-based adenoma of the colon.

View full abstract

Infrared laser endoscopy was devised to diagnose the depth and spread of involvement of gastric cancer. The beam of IR laser, which was produced by krypton dye laser, and which has 805nm wave length and about 300mW output, was led through a diffuser into the light guide fiber bundle of the conventional gastrofiberscope, so that the gastric wall was illuminated uniformly. Since infrared rays are invisible to naked eye, reflected light was visualized by IR vidicon tube on the television monitor. That made possible the real-time observation of the gastric wall illuminated by IR laser on the TV monitor. The deep vessels of stomach wall were observed in positive image, because the hemoglobin absorbs infrared rays considerably. ICG which was used as a routine liver function test and had a strong absorption peak at 805nm, was injected intravenously, and vascular network of deep vessels was obviously enhanced.
Twenty-nine gastric cancer cases were examined by this method. About 10 seconds after beginning of ICG (5mg/kg) injection intravenously, the image of deeper vessels became markedly clear in all of cases. In a few minutes, tumor stain and pooling phenomenon were observed.
In 23 out of 29 cases with gastric cancer, findings of infrared endoscopic angiography were studied by referring the operated gastric specimens. Tumor stain and/or pooling phenomenon were observed along the whole margin in 11 cases, at half margin in 6 cases, and partially in 6 cases, respectively. The characteristic findings of IR angiography are disappearance of normal mucosal vascular network with thin tumor stain in mucosal cancer, thick tumor stain and pooling on the margin in submucosal cancer, thick tumor stain on the crater in advanced cancer, respectively.
By adjusting the wave length of laser beam to the absorption peak of ICG (805mn), not only the image of the vascular network was observed more clearly, but also the cancer lesion was enhanced by tumor staining, and was margined by pooling.

View full abstract

Using the color papers and stained pig livers, we have demonstrated that cauterization of YAG laser beam are color dependent. Clinically, we observed that low power (15-20w) YAG laser would only cauterized in the area of stained Methylene blue without concerning the direction of the laser beam.
This method made it possible to irradiate early gastric cancer with no significant effects on normal gastric mucosal region.

View full abstract

We developed a laser Doppler velocimeter (LDV) with a one fiber catheter and succeeded in measuring coronary blood velocities. However, the one fiber system suffers from a broad Doppler spectrum due to the flow distribution at the vicinity of the fiber tip. To improve the Doppler shift spectrum, we tested an laser Doppler velocimeter with two fibers which extends the sensing field away from the fiber tip. The two fibers were placed side by side. The He-Ne laser beam was focused onto the entrance of one fiber (clad:62.5 m, core:50 m). The beam was emitted into a flow field with a spreading angle of 5. The backscattered light was collected by another fiber with a receiving angle of 17. The power of the reflected light from a mirror was maximum at 0.6mm from the fiber tip in a water bath. Evaluation of the Doppler signal was performed using an annular open channel flow on a rotating turntable. Doppler signals were analyzed by a spectrum analyser. The Doppler shift signal showed a-peaked pattern that is convenient for Doppler shift detection. The Doppler shift frequency had a linearity with the known blood flow velocity.

View full abstract

Theoretical analyses are conducted on the probing volume of a laser speckle flow monitor. The level of the light backscattered from scattering centers at certain depth in the skin tissue to the detecting point is evaluated. It is found that the size and the depth of the probing volume becomes larger with an increase of the distance between the illuminating and detecting fibers.

View full abstract

Power spectral distribution (PSD) of the laser speckle fluctuations produced by the blood flow in the intestinal mucosa of a rabbit are studied experimentally. It is found that the PSD takes a Gaussian profile being different from those produced by the skin blood flow. The mean frequency fm of the speckle signal is measured to evaluate the blood flow level. The value of fm,is shown to decrease from 1.8kHz to 1.0kHz when the vascular pedicle of the intestine is clamped.

View full abstract