Histological studies of myocardium zones irradiated with Nd-YAG laser

Histological investigation of the dog's myocardium performed 7 and 25 days after irradiation with different doses of Nd-YAG laser show that the damage zone has the shape of a hollow sphere with minor changes in cardiomyocytes in the central part of the sphere. The small blood vessels in the irradiated zone remained undamaged as well. A tentative explanation of the physical process that leads to this type of coagulation zone is given.     

Nd:YAG laser irradiation of the human dental pulp: implications as a predictor of pulp hemodynamics

BACKGROUND AND OBJECTIVE: The aim of study this was to evaluate in vivo the pulpal blood flow rate, pulpal responsiveness, systemic blood pressure, and pulse rate during Nd:YAG laser irradiation of an isolated tooth. STUDY DESIGN/MATERIALS AND METHODS: Thirteen volunteers from the Tsurumi Dental University faculty participated in this study after giving their consent to the Nd:YAG laser irradiation test protocol. Gingivobuccal areas adjacent to mandibular canines were used for clinical evaluation. Each area was coated with India ink and treated with a Nd:YAG laser for 30 sec at 120-mJ pulses at 10 pulses/sec. Pulpal blood flow was measured by a laser Doppler flowmeter during Nd:YAG laser irradiation of the tooth. All pulp responses were measured by an electric pulp tester before and after Nd:YAG laser irradiation. In addition, the systemic blood pressure and pulse rate were monitored throughout the laser irradiation procedure. RESULTS: For all subjects involved in this study, the pulpal blood flow rate increased during laser irradiation. Threshold values of the electric pulp tests increased in six cases and decreased in six cases. One case showed no change. After 1 month, the threshold values for each subject had returned to previously recorded values. Neither systemic blood pressure nor pulse rate was affected during Nd:YAG laser irradiation. Pulpal blood flow was strongly influenced immediately after Nd:YAG laser irradiation, seen as an increase in the flow rate. CONCLUSION: The results of this study suggest that effects of the Nd:YAG laser irradiation are similar to those of low power laser for the improvement of local blood flow.     

Deep and localized hyperthermia of the liver induced by stereotaxic Nd-YAG laser irradiation

Thirty six hepatic lesions (12-18 mm) of localized hyperthermia are induced in eleven pigs by means of a Nd-YAG laser. Laser shots of 80 W/10 sec. are transmitted through a stereotaxic handpiece coupled to a water cooling circulation protecting the optic fibre. The handpiece placement is performed through an ultrasound-guided trocar. The efficiency of the irradiation is visualized by immediate temperature increasing, by ultrasonographic imaging and by anatomical verifications from operating time to four months. The center of lesion initially occupied by coagulative necrosis is rapidly marginated by a gaining ground fibrosis. At long term a fibrotic network invades the scar and confirms healing free of complications. This ultrasonographically assisted technique is proposed for deep vaporisation of disseminated hepatic metastases.     

Nd-YAG laser for general surgery

We report here our clinical experiences with Nd-YAG laser on general surgery, and evaluate the results of this procedure. From December 1979 to December 1981, we applied Nd-YAG laser to various operations as a hemostatic and cutting tool. For hemostasis, we used conventional quartz fiber which was covered with sterile tube, and hemostatic efficacy was examined especially in the subcutaneous bleeding and the bleeding from solid organs. For cutting, we used special devices, ie, Medilas YAG surgical probe (noncontact-type probe), and a laser blade (contact-type probe), and performed four liver resections. It is concluded that the hemostatic efficacy of Nd-YAG laser to various bleeders was proved in general surgical procedures, and furthermore this laser can cut tissue if we utilize these devices. When comparing these two devices, we would prefer the contact-type probe.     

Enhancement of tissue lesion depth by dual wavelength irradiation with the Nd-YAG/KTP laser: Perspectives for laser prostatectomy

The Nd-YAG/KTP laser coagulates and vaporizes prostate tissue. The objective of this study was to investigate the combined effects of both wavelengths and to determine the irradiation parameters allowing the largest lesion volume. Chicken breast tissue was irradiated ex vivo. Consecutive 1064 and 532 nm Nd-YAG/KTP laser irradiations were performed for different combinations (30 W/10 W, 20 W/20 W, 10 W/30 W) with variable total fluence (1200 J, 2400 J, 3600 J) and compared to isofluent single wavelengths at 40 W irradiation. The depths, diameters and volumes of the total lesion as well as the vaporization effects of the 532 nm wavelength on normal and on priorly coagulated tissue were analysed. Maximum total lesion depths (p< 0.001) were found under combined Nd-YAG/KTP (20 W/20 W) irradiation conditions. Ablation efficacy of the 532 nm wavelength was reduced after prior 1064 nm irradiation, but crater depths were increased. Dual wavelength irradiation with the Nd-YAG/KTP laser induces a specific denaturation process. This may represent a new approach to increase the depth of coagulation necrosis, and thus the treated volume, thereby improving long-term results.     

Histological changes in human breast cancer after interstitial irradiation with a pulsed Nd-YAG laser

This is a clinical study of the histological changes induced in human primary breast cancer by single-session pre-operative interstitial irradiation using a medium-power Nd-YAG laser (1064 nm, 1–6 W, 20 pulse s^-1, 100 Μs). Changes were studied in 15 tumours resected at an interval of 1–11 days after laser treatment, and in four biopsy samples from three tumours treated conservatively and biopsied for suspected recurrence 1–3 months after laser treatment. All foci of laser-induced destruction consisted of a sphere-shaped infarction 0.5–2.5 cm in diameter which enclosed a small evaporation cavity within carbonized walls. Vapour separation occurred in two tumours and gaseous rupture was seen in one tumour. Extensive vascular damage was seen inside the damaged area; damage to cancer cells was manifested by diminished size, vacuolization, cytoplasmic turbidity, pyknosis, disruption of the nuclear membrane and nuclear homogeneity. No clear morphological signs of damage could be seen in a significant percentage of cancer cells on short-term inspection (35–80%). Long-term histological study revealed a central necrotic area of diameter 1–1.2 cm in the laser-treated tumours, containing no viable cancer cells. In inadequately treated carcinomas, regrowth of tumour was seen at the periphery of this zone.     

The role of pulse length in limiting distant damage to vascular tissue caused by the Nd-YAG laser

The total damage caused by equivalent doses of energy given to human cadaver vascular tissue over the same time scale from three Nd-YAG lasers of different pulse lengths is quantified. The continuous wave (c.w.) laser produces vacuolation and coagulation around a vaporized crater; the 100 μs pulsed laser produces less surrounding damage and the 10 ns pulsed laser none at all. The areas of damage in five craters made with 10 J energy were measured from histology slides using a digitising platten, and it was found that in each case the total amount of damage was the same, even though the depth of the craters made varied. The dose response for vaporization of the 10 ns pulsed laser was the greatest at 35 μm/J and that of the c.w. laser was least at 8 μm/J. A pulse length of 100 μs may not be the optimum for limiting surrounding tissue damage during laser angioplasty but it produces much less damage than a c.w. laser and unlike the 10 ns pulses is easily transmissible down an optical fibre.     

In vivo temperature measurement during transcatheter endomyocardial Nd-YAG laser irradiation in dogs

Intramural temperatures were monitored during catheter-directed endomyocardial non-contact laser irradiation by means of an array of thermocouples inserted epicardially. Via a novel electrode-laser catheter, a total of 30 Nd-YAG laser pulses, 1064 nm, 25 W/15 s, 20 W/30 s, 15 W/45 s,n = 10 each, were aimed at various endocardial sites in the ventricles of four dogs. Temperatures increased gradually after the onset of the laser pulses. Maximum values were measured in the central area of the irradiated spots: 100 ± 15 ‡C at 25 W, 78± 23 ‡C at 20 W and 80 ± 13 ‡C at 15 W. Application of 300 J of laser energy induced significantly higher temperatures at 25 W (p< 0.02) than at 20 or 15 W (20vs 15 W: p> 0.05). Initial temperature rise and lesion formation was accompanied by dwindling of local electrical potentials. There was no crater formation. Transcatheter non-contact Nd-YAG laser coagulation of healthy ventricular myocardium can be performed in a safe and controllable manner at power settings up to 20 W and laser energies up to 675 J.     

Examination of tooth pulp following laser beam irradiation

An attempt was made to determine the maximum amount of laser energy which could be utilized without impairing pulpal vitality. Forty rat molar teeth were irradiated in vivo; the Sharplan CO2 laser modality, focused to a 0.2-mm-diameter spot size was used. The energy output was varied by changing the power and/or the pulse duration. Subsequent histological examination of the irradiated teeth showed that the duration of exposure was more significant than the power. A pulse of 0.2 sec/10 W appears to be the safety limit in preserving pulpal vitality.     

Safety precautions for bronchoscopic Nd-YAG laser surgery

The application of the neodymium-yttrium aluminum garnet (Nd-YAG) laser in bronchoscopy originated in Europe in 1981 and is now widespread in the United States. Transmissible through flexible fiberoptic quartz fibers and an efficient coagulator of tissue, the Nd-YAG laser deeply penetrates tissue not readily predictable by the endoscopist. Dangers associated with the Nd-YAG laser include complications secondary to inadvertent exposure to normal tissues or structures, tracheobronchial accidents (perforation, hemorrhage, fire), and complications related to anesthetic technique (respiratory depression). Hypoxemia related to persistent hemorrhage, accumulation of secretions or debris or both, or anesthesia-induced respiratory depression is the common denominator of most intraoperative and postoperative complications. Careful selection of patients, intraoperative monitoring of ventilation and blood gases, and techniques of rigid bronchoscopy are stressed to avoid complications.     

Non-destructive assessment of inhibition of demineralization in dental enamel irradiated by a lambda=9.3-microm CO2 laser at ablative irradiation intensities with PS-OCT

BACKGROUND AND OBJECTIVE: Polarization sensitive optical coherence tomography (PS-OCT) has great promise for the non-destructive assessment of the efficacy of anti-caries agents such as fluoride and thermal laser treatments on enamel surfaces. The purpose of this study was to demonstrate that PS-OCT can be used to measure demineralization in craters/incisions prepared in enamel by a CO(2) laser operating at the high irradiation intensities required for cavity preparations. MATERIALS AND METHODS: Incisions in bovine enamel surfaces were produced by a CO(2) laser used with a water spray. The laser was operated at lambda=9.3 microm with a pulse duration of 15 micros and an incident fluence of 20 J/cm(2). The laser treatments were also combined with topical fluoride treatments. A PS-OCT system operating at 1,310 nm was used to acquire polarization resolved images of six areas including sound and laser-ablated+topical fluoride treated zones on each sample. After imaging the teeth, they were sectioned and the thin sections were examined with polarized light microscopy (PLM) and transverse microradiography (TMR). The integrated reflectivity and lesion depth derived from the PS-OCT scans, the integrated mineral loss and depth measured using TMR and the lesion depth measured with PLM were acquired for each area on the fifteen samples for comparison. RESULTS: The integrated reflectivity and depth in the areas treated by the laser and fluoride were significantly lower (P<0.05) than for the untreated enamel. Similar results were observed for TMR and PLM. CONCLUSIONS: These results suggest that PS-OCT has great potential for the non-destructive "in vivo" assessment of the inhibition of demineralization by lasers at ablative irradiation intensities with and without topical fluoride application.     

Large-bowel perforation. A rare complication of intravesical Nd-YAG laser irradiation of bladder tumors

A case report of large-bowel perforation after intravesical neodymium-yttrium aluminum garnet laser irradiation is presented. Recommendations to prevent bowel injury are discussed.     

Endobronchial hamartoma treated by an Nd-YAG laser: Report of a case

Endobronchial hamartomas are only rarely encountered. They cause irreversible lung damage due to bronchial obstruction if not diagnosed early and treated properly. Among the various treatments for this rare disease, a surgical resection remains the most popular. We herein report a case of a 53-year-old man presenting with an endobronchial hamartoma which was successfully excised by laser irradiation via a rigid bronchoscope, along with a review of 113 patients with this disease reported in the literature.     

嗅鞘细胞经低能激光照射后移植对大鼠脊髓损伤神经功能修复的影响

Objective To investigate the effects of transplantation of olfactory ensheathing cells (OECs) irradiated by low power laser irradiation(LPLI) on the repair of transversal spinal cord injury in rats. Methods Twenty-four SD rats were randomized into 3 even groups after the animal models of spinal cord completely transected at T12 had been established for 4 weeks. OECs(group A), OECs ir-radiated by LPLI(group B) and DMEM fluid(empty control group) were transplanted into the caudal zone of the spinal cord in the 3 groups(n=8) respectively. The functional repair was evaluated by Bundle branch block (BBB) score, pathology and Flumgold label, respectively. The BBB scores before and after transplantation were statistically analyzed by one-factor analysis of variance or repeated measurement anal-ysis of variance, respectively (α=0.05). Results The methods of transplantation and the evaluation time had significant effects on the BBB scores in the 3 groups (P=0.000), and the BBB scores were significantly different among the 3 groups (P=0.000). Anti-NGRFp75 and anti-GFAP staining positive OECs were observed in the cephalic and caudal areas in group B, only anti-GFAP staining positive OECs were observed in group A, but nothing was found in the empty control group. The neural fibers labeled by Flurogold passed through the lesion area and extended into the cephalic and caudal areas in groups A and B, but were not present in the empty control group. Conclusion Although transplantation with both OECs and OECs irradiated by LPLI can promote the repair of spinal cord injury in rats, OECs irradiated by LPLI may be more effective.     

嗅鞘细胞经低能激光照射后移植对大鼠脊髓损伤神经功能修复的影响

目的 探讨嗅鞘细胞(OECs)经低能激光照射(LPLI)后移植对大鼠脊髓横断损伤后功能修复的影响. 方法 24只SD大鼠T<,12>脊髓完全横断伤模型建模4周后,随机分为OECs移植组、经LPLI的OECs的移植组和空白对照组(DMEM培养液),应用BBB评分法、组织学评价以及Flurogold逆行示踪评价各组脊髓损伤的修复情况. 结果三组大鼠不同移植方式以及评分时间点对移植后下肢功能BBB评分结果的影响差异均有统计学意义(P=0.000),且组间差异均有统计学意义(P=0.000).经LPLI的OECs移植组大鼠头尾侧均可见NGFRp75阳性及GFAP阳性的OECs,OECs移植组则仅可见GFAP阳性的OECs,空白对照组未见NGFRp75阳性及GFAP阳性的OECs.OECs移植组和经LPLI的OECs移植组大鼠头尾侧及瘢痕区均可见Flurogold标记的神经纤维穿行,空白对照组未见Flurogold标记的神经纤维穿行. 结论 OECs及经LPLI的OECs均可促进损伤脊髓的功能恢复,OECs经LPLI后可能更具有促进损伤脊髓功能恢复的作用.     

Porcine skin ED50 damage thresholds for 2,000 nm laser irradiation

BACKGROUND AND OBJECTIVES: To gain refinement in safe-exposure limits, indicated by the maximum permissible exposure (MPE) limits, the minimum visible lesion thresholds for three spot sizes (5-15 mm) and four exposure durations (0.25-2.5 seconds) were determined for the skin at 2,000 nm continuous wave laser irradiation. STUDY DESIGN/MATERIALS AND METHODS: A series of experiments were conducted in vivo on female Yucatan mini-pigs to determine the ED50 damage thresholds for 2,000 nm continuous wave laser irradiation. The study employed Gaussian laser beam exposures with spot diameters (1/e2) of 4.83, 9.65, and 14.65 mm and exposure durations of 0.25, 0.5, 1.0, and 2.5 seconds as a function of laser power. The effect of each irradiation was evaluated within 1 minute after irradiation and the final determination was made at 48 hours post-exposure. Probit analysis was conducted to estimate the dose for 50% probability of laser-induced damage (ED50), defined as persistent redness at the site of irradiation for the mini-pig skin after 48 hours. RESULTS: The MPE spot size and exposure duration trends for 2,000 nm laser exposure is consistent for exposure diameters less than 3.5 mm. However, for larger exposure diameters of 4.83, 9.65, and 14.65 mm and exposure duration longer than 0.25 second, the current MPEs are bigger than one tenth of our damage thresholds. For Gaussian laser profile, which is common for many laser output irradiance distributions, lower energy is required to generate a lesion on skin for smaller spot sizes and shorter exposure duration. On the other hand, for spot sizes greater than 4.83 mm and exposure duration over 0.25 second, the average radiant exposure at threshold is inversely proportional to spot size. The irradiance-time and temperature-time power law at the threshold were investigated as well and showed that the irradiance-time power law was a close approximation to estimate laser irradiance at ED50 damage threshold. CONCLUSIONS: The thresholds study shows that consideration for lowering the MPE standards should be explored as the laser beam diameter becomes larger than 3.5 mm. Based on the limited experimental data, the duration and size dependences of the ED50 damage thresholds could be described by an empirical equation: Irradiance at the threshold = (5.669-1.81xspot diameter)xexposure duration -0.794.