Lased Area Research Articles

Pathological analysis of transmyocardial laser revascularization for acute myocardial ischemia.

Transmyocardial laser revascularization (TMLR) is an alternative surgical procedure for the patients with intractable coronary artery disease. Efficacy of the treatment has been established, however, the mechanism of TMLR is still controversial. In this study, we investigated the effect of TMLR on acute myocardial ischemia with pathological analysis. Under general anesthesia, the hearts of mongrel dogs were exposed. Then, the anterior descending branch of the left coronary artery was ligated to make the ischemic area on the left ventricle. Laser punctures were made 30 minutes after coronary ligation in the TMLR group (n = 5), and no further procedure was performed after coronary ligation in the AMI group (n = 5). One month after these operations, the hearts were extirpated for pathological studies. The avascular area and the viable area in the infarcted area were macroscopically separated by Evans blue dye and triphenyltetrazolium chloride (TTC) staining. Thickness of the left ventricular wall in the infarcted area was also measured and compared. Furthermore, all of the infarcted area and the lased area were microscopically examined with Masson's trichrome stain. The size of the infarcted area in the TMLR group was smaller than that in the AMI group. It was significantly different (p < 0.05) in the basal and apical regions. As a result, the ratio of the viable area by the avascular area was larger in the TMLR group than in the AMI group. It was significantly different (p < 0.05) in the apical region. In the basal region, the thickness of the left ventricle in the AMI group was thinner than that of untreated dogs (normal group: n = 5), and there was no difference between the normal group and the TMLR group. Whereas in the apical region, significant difference of the thickness was found among AMI, TMLR, and normal groups (p < 0.05). In conclusion, our study supported; 1) TMLR reduced overall infarcted size, and increased the viable area in the infarcted area, 2) TMLR prevented the thinning of the left ventricular wall.

The effects of laser-induced collagen shortening on the biomechanical properties of the inferior glenohumeral ligament complex.

The purpose of this study was to determine the effects of laser-induced collagen shortening on the biomechanical properties of the inferior glenohumeral ligament complex. Fifty-seven bone-ligament-bone specimens underwent uniaxial tensioning to 10% strain. Approximately half of the specimens then underwent 10% shortening by lasing using a holmium:yttrium-aluminum-garnet laser. Both groups were again tensioned to 10% strain, and then loaded to failure. Ultimate strain and yield strain were significantly higher in the lased specimens than in the nonlased specimens. No significant difference was found for ultimate stress, yield stress, or elastic modulus between the two groups. Failure of the ligament did not appear to occur in the lased areas. The load-to-failure results suggested that the strength of the ligament complex was not significantly compromised by this lasing protocol.

Reduced‐threshold‐current vertical cavity surface‐emitting laser

AbstractA simple method for reducing the threshold current of vertical cavity surface‐emitting lasers (VCSELs) is described. The approach modifies the top surface of the laser into a dome shape by chemical etching. This reduces the reflectance of the top mirror over an approximately annular region, thereby reducing the lasing area compared to the contact area in a controlled manner. A sevenfold reduction in threshold current over equivalent conventional VCSELs is demonstrated for a nonoptimized device that maintains a similar threshold current density. © 1995 John Wiley &amp; Sons, Inc.

Efficacy of XeCl 308-nm excimer laser in reducing dye penetration through coronal dentinal tubules

The efficacy of XeCl excimer laser irradiation in reducing dye penetration through human coronal dentinal tubules was studied. The roots of 20 freshly extracted human molars were resected, and the apical aspect of the crowns was ground until the pulp chamber was completely exposed. Following total removal of the pulp chamber and further grinding of the occlusal and apical surfaces up to the intact dentin, the teeth were randomly divided into experimental and control groups of 10 each. The teeth in the experimental group were completely coated with nail polish and then irradiated with XeCl 308-nm excimer laser at a fluence of 0.7 J/cm2 to form an elliptical lased area. The teeth in the control group were also coated with nail polish, but with a similar elliptical spot of exposed dentin corresponding to the irradiated spot created in the lased teeth left uncoated. All specimens were placed in 0.5% methylene blue dye for 48 h, rinsed, and air-dried. The specimens were then ground to reach the experimental area in order and photographed. The total area of penetrated dye was determined by three independent evaluators and then measured with a computerized planimeter. The mean total areas (mm2) measured in the lased specimens were significantly smaller than those in the controls (p = 0.012).

Clinical experience of laser angioplasty with angioscopic guidance.

Since 1986, intraoperative angioscopic observations have been followed by the study of laser angioplasty experimentally and clinically. The healing process of the lased arterial wall initially was evaluated angioscopically in the canine model. The lased area was observed as a crater covered with char soon after laser irradiation. One week after laser irradiation, subintimal bleeding around the crater and a small fresh thrombus on the crater were seen in some cases. Four weeks after laser irradiation, the crater was covered with new endothelium. In this experimental study angioscopy provides information which cannot be obtained by other means.

唾液浸漬によるレーザー照射エナメル質の変化

Changes in lased human dental enamel after immersion in human resting whole saliva were investigated by the determination of Vickers hardness number (VHN) and amount of calcium released into acid solution, and also by polarized light microscopy and scanning electron microscopy (SEM). Lased enamel had a lower VHN than unlased enamel, but it rehardened significantly after immersion in saliva for 5 days. The VHN of lased enamel became larger as the period of immersion in saliva increased.A high positive birefringence of lased enamel was reversed during the immersion in saliva. After immersion for 10 days, the lased area showed a low negative birefringence which was similar to that of the unlased enamel. The rehardening and the change in birefringence of lased enamel were attributed to deposition of salivary ions in microspaces created in dental enamel by laser irradiation.The amount of calcium dissolved from enamel which was lased and subsequently immersed in saliva for 10 or 20 days was higher than that from enamel which was lased only. However, the lased enamel still retained significantly higher acid resistance than unlased enamel even after immersion in saliva for 20 days. No remarkable change of the surface of lased enamel was observed by SEM after immersion in saliva.Those results suggested that lased enamel gets a structural stability by rehardening and it retains high resistance to an acid attack in the oral cavity.

脱灰エナメル質の再石灰化に及ぼすレーザー照射の影響

The purpose of this study was to examine the influence of laser irradiation on remineralization of demineralized enamel. Twenty human premolar enamel slabs (3×5mm) were prepared for this study. The enamel slabs were ground down to about 400μm and immersed in 0.1M lactic acid buffer (3.0mM Ca, 1.8mM P, 1.0% carboxymethylcellulose, pH 4.5, 37°C) for 12 hours. Demineralized enamel slabs were irradiated with a Q-switch Nd-YAG laser at 50 J/cm2of total energy density. After laser irradiation, slabs were immersed in remineralizing solution (3.0mM Ca, 1.8mM P 1.0% carboxymethylcellose, 150mM NaCl, 3.0ppm F, pH 7.0, 37°C) for 10 days. The degree of remineralization was evaluated by microradiograph using calculated mineral content. Sectioned enamel slabs were also immersed in 0.5M HClO4solution for 1 minute to examine acid resistance of the remineralized enamel.There were signs of remineralization in both the lased and unlased areas, and no clearly difference was recognized between these areas. It appears that remineralization of enamel was not inhibited by laser irradiation. The acid resistance of the remineralized enamel was higher in the lased area than in the unlased area. However, the degree of remineralization corresponding to the mineral level was not significantly different between two areas. It is probable that the permeability of enamel was not decreased by laser irradiation.

Blpolar Laser Forceps (双極レーザーピンセット) の開発とその応用

A new device attached double flexible optical fibers was designed as a bipolar laser forceps.The distal tips of the forceps which made of metal sheath were angled roundly inward 45 degree and then, the tips were faced to face each other with the angle of 90 degree. An argon laser deliverling 488-514.5nm was used in the present series. The laser beams were transmitted by the laser fiber couplar with two proximal fibers of 200μm in diameter. The laser beam was irradiated onto the tissue from each tip of the fiber in serted in the metal sheath of the for forceps.The methods of tissue fusion with ELF was summarized as the technique using contact laser irradiation under compression onto the narrow point of the aimed tissue. Looking at the fused tissue tiney crater was seen at the both sides of the compressed portion. Using this modality, an experimental tissue fusion was tried on a sacrificed cattle liver, and then the tensile strengths of the fused liver were measured immdiately after laser irradiation in the groups A 200mW, B 300mW and C 500mW. The best strength in this series was achieved as 17.2g on the average, 6.8g/mm2 on the lased area, at the energy of 2 J in group B, while the control groups of non-contact irradiation by BLF under same conditions could be yield no tensile strength. Corresponding to the welded point, the small hole with thermal damage was observed and ascertained shear strength could be gained according to the adjacent tissue with carbonization. It is expected that bipolar laser forceps would be applied to the clinical field in succession to the further experiments.

Laser angioplastyに関する実験的研究

With argon laser coupled to a fiberoptic system, experimental studies were carried out to evaluate the healing response of the normal arteries to laser irradiation. Firstly, the femoral and carotid arteries in the canine were exposed, and laser irradiation of argon was delivered transluminally by bare ended probe with angioscope by which acute intravascular laser effects were observed. Between 24 hours and 10 weeks after these procedures, the lased canines were anesthetized again, and the healing process of the lased arterial wall was evaluated angioscopically. Subsequently, deep craters covered with char were observed 24 hours after lasing, and fresh thrombus was recognized on the crater in only one of 12 cases. One week after lasing, craters become shallow, and the color of arterial wall around the craters changed reddish by subintimal hematoma. By two weeks, progression of the healing process was observed macroscopically. That is, craters were covered with endothelium and decrease of reddish color of arterial wall around the craters was clearly noted endoscopically. Almost all craters were completely reendothelialized until four weeks after lasing, and the lased areas were completely healed after 10 weeks, angioscopic findings above mentioned were proved pathologically. In conclusion, it could be considered that healing process of the lased arterial wall was completely achieved by four weeks after laser irradiation and angioscopy was useful procedure to observe intravascular laser effects.

連続波Nd : YAGレーザー照射によるラット生活歯髄の変化について

The biological effects of irradiation with cw Nd: YAG laser on the pulp of rat molar teeth were examined histopathologically. Right after the irradiation, the pulp showed exudative inflammatory changes with hyperemia and focal degeneration of odontoblasts. One week later of irradiating with rats, inflammatory changes were improved. One month later, there was marked proliferation of the undifferentiated mesenchymal cells at the lased area. Subsequently the odontoblast layer became prominent followed by the production of the predentin at 4 months later. Six months later, the size of the pulp space was reduced by the continued deposition of the secondary dentin-like tissue. These cellular dynamics was not observed in the non-lased control dental pulp.These results suggested that the once irradiation of cw Nd: YAG laser to the rat molar teeth would cause prolonged biological effects on the pulp tissue.

Laser-induced phase transitions in amorphous Fe 80B 20 alloy

Exposure of amorphous Fe 80B 20 alloy to two pulses of a laser beam of energy 35 Jcm −2 produces the equilibrium crystalline phase mixture α-Fe + Fe 2B at the point of impingement. Analyses of the zones adjacent to the lased area show a three-phase mixture α-Fe + Fe 3B + Fe 2B, a two-phase mixture α-Fe + Fe 3B and clusters of α-Fe in an amorphous matrix as the distance from the lased area is increased. These structures are consistent with earlier work on this alloy utilizing both continuous and isothermal annealing experiments. Although lower fluences (less than 35 J cm −2) do not seem to reveal structural transitions in transmission electron microscope analyses, field ion microscope observations show very small (less than 20 Å) clusters of α-Fe domains and an increasing number of void zones on exposure to an increased laser fluence.