Lasers in surgery and medicine reviewers. November 1, 1992 through October 31, 1993

Chloro-aluminum sulfonated phthalocyanine (CASPc) is a photo-chemically active dye employed in photodynamic therapy (PDT). CASPc is a potent generator of singlet oxygen when irradiated with 675 nm light and is also capable of fluorescence, allowing visualization of the dye in tissues. We devised an angiography system using CASPc fluorescence to determine its localization in experimental choroidal neovascularization in monkeys and then investigated the ability of CASPc to produce photochemical closure of neovascularization upon irradiation with 675nm laser light. Fluorescent imaging indicated that CASPc localized angio-graphically in areas of neovascularization for at least 24 hours. Irradiation with 675 nm laser light 5–30 minutes after CASPc injection produced complete closure of choroidal neovascularization with minimal damage to overlying retina. We conclude that CASPc localizes in neovascular choroidal vessels and that CASPc photodynamic therapy can produce closure of these choroidal vessels. © 1994 Wiley-Liss, Inc.     

Endoscopic laser therapy in malignant tracheobronchial obstruction using sequential Nd YAG laser and photodynamic therapy

BACKGROUND: Because the survival after treatment of advanced inoperable endo-tracheobronchial carcinoma is so poor, a pilot study was undertaken to evaluate the combined cumulative effect on survival of neodymium yttrium aluminium garnet (Nd YAG) laser followed by photodynamic treatment used endoscopically. METHODS: Seventeen patients who presented between January 1992 and March 1996 with inoperable tracheobronchial lesions causing more than 50% endoluminal obstruction were selected to enter the pilot study. Initially they had bronchoscopic Nd YAG laser treatment to debulk the tumour, and this was followed six weeks later by photodynamic therapy to treat the residual tumour. RESULTS: All patients had symptomatic relief and at least a partial response, and seven had a complete response for 3-6 months. Eight of the 17 (47%) survived for at least two years and 11 (65%) survived for a year or more. The median survival of the 10 patients who had died by the time of writing was 18.5 months (range 5-39), 95% confidence interval (CI) 9.9 to 29.5. CONCLUSIONS: Combined Nd YAG laser and endoscopic photodynamic therapy may be an effective palliative treatment for patients with inoperable endotracheobronchial cancer.


     

Threshold parameters for choroidal vessel closure with the photosensitizer, lambda 27

Objective: To determine the threshold photodynamic therapy parameters, required for choroidal vessel closure, with the photosensitizer, Lambda 27, in Dutch belted rabbits, using fluorescein angiography and histopathology. Design: A pre-clinical experiment. Place and Duration of Study: Department of Ophthalmology at the Tulane University Health Sciences Center, between June 2001 - July 2002. Patients and Methods: Dutch belted rabbits were divided into two groups. The first group was injected intravenously with an aqueous solution of Lambda 27 at 1mg/kg. Saline was injected intravenously into the second group (controls). Approximately 5 minutes after injection of Lambda 27, a diode laser, mounted on Zeiss 30 SL-M slit lamp, emitting light at a wavelength of 719 nm was used to apply photodynamic therapy to the fundus. Lesions were placed on the choroid of the rabbits at a fixed spot size of 1.5 mm, using powers ranging from 50 to 120 mW, for a duration of 5 to 80 seconds. Choroidal vessel closure was documented by fluorescein angiography, the following day, and by light microscopy, after the animals were sacrificed. Results: Choroidal vessel closure was documented using fluorescein angiography for all of the lesions placed at fluence of 22.7 J/cm2 and above. Histopathology also confirmed this finding. No choroidal vessel closure was seen in the rabbits treated with fluences less than 22.7 J/cm2 or in the control group. Conclusion: This experiment establishes threshold parameters for choroidal vessel closure using the photosensitizer, Lambda 27.     

Nd:YAG laser followed by radiation for treatment of malignant airway lesions

Patients with malignant obstructive airway lesions often present with total or segmental atelectasis of lung. In spite of prompt initiation of palliative external radiation alone, some patients were unable to complete the planned course of radiation therapy. Since May 1983, 17 patients with malignant obstructive endobronchial lesions have been treated by endoscopic Nd:YAG laser vaporization of the tumor. One to seven days later, fractionated external radiation therapy was initiated. Endoscopic use of the laser was repeated as needed during the course of treatment. Fifteen out of 17 patients successfully completed the planned course of therapy. The improved performance status was sustained in 13 of 15 patients for 2-13 months. A control group was selected from among patients with similarly located lesions who underwent external radiation treatment only prior to the availability of the Nd:YAG laser therapy. One patient developed radiation pneumonitis six weeks after completion of a second course of external radiation, another patient developed bronchopleural fistula after laser treatment which healed following closed chest tube drainage. The others had longer palliation of symptoms and improved quality of life. The results indicate that relief of airway obstruction by use of the Nd:YAG laser improved the patients' ability to tolerate subsequent external radiation treatment.     

Selective occlusion of choroidal neovascularization by photodynamic therapy with a water-soluble photosensitizer, ATX-S10

BACKGROUND AND OBJECTIVE: To determine the optimal treatment parameters for selective occlusion of choroidal neovascularization (CNV) by photodynamic therapy (PDT) by using the photosensitizer ATX-S10 and a diode laser (wavelength = 670 nm). MATERIALS AND METHODS: Experimental CNV was induced in rat fundi by argon laser photocoagulation. The distribution of ATX-S10 in the chorioretina was analyzed by fluorescence microscopy, and the optimal treatment parameters for selective occlusion of CNV were investigated by changing the dosage and timing of laser irradiation. CNV closure and resulting damage of the surrounding tissue were documented by fluorescein angiography and light and electron microscopies. RESULTS: Fluorescence of ATX-S10 was observed to be localized in the vascular lumen of the retina and choroid within 5 min after dye injection and increased in intensity in CNV up to 2-6 h and decreased rapidly in normal tissue. Laser irradiation with radiant exposures of 7.4 J/cm2 applied immediately after dye injection or with 22.0 J/cm2 at 2-4 h later effectively occluded the induced CNV without causing significant damage to normal retinal capillaries and large choroidal vessels. CONCLUSIONS: PDT using ATX-S10 can selectively occlude CNV. ATX-S10 is a potentially useful photosensitizer for the treatment of CNV.     

Laser therapy of colorectal carcinoma.

A plethora of literature is available demonstrating the efficacy of Nd:YAG laser therapy for obstructing or bleeding colorectal cancers. The in-hospital mortality and morbidity rates can be reduced when Nd:YAG laser therapy is used to avoid operative diversion prior to resection and anastomosis. The Nd:YAG laser used to control bleeding or obstruction in those patients with either widely metastatic or unresectable locoregional disease has been successful in the majority of patients and has been associated with minimal morbidity and mortality rates. This laser may be the only treatment modality that may substitute for operative diversion in hopeless clinical situations such as hemorrhage or obstruction in patients with advanced disease. The utility of photodynamic therapy for colorectal cancer will require definition in further controlled trials.     

Application of pulsed and continuous wave 1.32 and 1.06 microns wavelengths of the Nd:YAG laser in the canine tracheobronchial tree: a comparative study

Previous investigations have shown good clinical potential for the use of the 1.32 microns wavelength Nd:YAG laser because its soft tissue absorption is better than that of the 1.06 microns wavelength Nd:YAG laser. The 1.32 microns wavelength Nd:YAG laser has an absorption coefficient in water that is 10 times higher than the 1.06 microns wavelength Nd:YAG laser. A comparative in vivo study of laser soft tissue effects was performed by using the 1.32 microns wavelength and the 1.06 microns wavelength Nd:YAG lasers in a pulsed wave (PW) mode and continuous wave (CW) mode using a non-contact endoscopic delivery system. A standard 5 mm mucosal lesion was made in the canine tracheobronchial tree down to the level of the perichondrium. Soft tissue and cartilage effects were examined by light and scanning electron microscopy, acutely, 1 week and 2 weeks after operation, and a comparison was made between the different laser modalities. To create similar lesions, higher energy was required when using the 1.06 microns wavelength Nd:YAG laser. Soft tissue injury was greater with the 1.06 microns wavelength in CW mode, and no cartilage damage occurred in the PW mode. Soft tissue and cartilage repair after 1 and 2 weeks was better with the 1.32 microns wavelength laser. In comparison, the CO2 laser and the contact Nd:YAG laser proved to be more precise cutting tools than the 1.32 microns wavelength or the 1.06 microns wavelength Nd:YAG lasers. Both Nd:YAG laser wavelengths were useful for coagulation and vaporization of tissues and blood vessels. More studies are needed to determine the effect of the new 1.32 microns wavelengths on endotracheal tumors.     

Treatment of cervical dentin hypersensitivity using neodymium: Yttrium-aluminum-garnet laser. Clinical evaluation

BACKGROUND AND OBJECTIVE: The incidence of cervical dentinal hypersensitivity is related to the high number of non-carious cervical lesions. This clinical research was developed in order to evaluate the Nd:YAG laser treatment of cervical dentin hypersensitivity after attempting the removal and control of etiologic factor after two different stimuli. STUDY DESIGN/MATERIALS AND METHODS: Twenty patients participated in this study in a total of 145 teeth, where 104 received the Nd:YAG laser treatment and 41 remained as control. RESULTS: The results showed that there was statistically significant reduction of hypersensitivity as for the groups that received the treatment with Nd:YAG laser, as for the control teeth. However, the reduction of cervical dentinal hypersensitivity was statistically greater when there was the association of the removal of etiologic factors with the application of Nd:YAG laser. CONCLUSIONS: We concluded that the laser irradiation was effective in the treatment of cervical dentin hypersensitivity after 6 months.     

The effect of laparoscopic treatment of polycystic ovarian disease by CO2-laser or Nd:YAG laser

Summary The feasibility and efficacy of laparoscopic CO₂ laser and Nd:YAG non-contact laser application for the treatment of polycystic ovarian disease (PCOD) were evaluated in 30 patients (19 patients treated with the CO₂ laser, and 11 with the Nd:YAG laser). The criteria for inclusion of PCOD in our study were: amenorrhea or oligomenorrhea with chronic anovulation, failure to ovulate in response to clomide or human menopausal gonadotropin, elevated serum levels of luteinizing hormone (LH) or an elevated LH/follicle-stimulating hormone ratio, exaggerated LH response to gonadotrophin-releasing hormone (GnRH), elevated serum androgen levels, and ultrasonographic features of polycystic ovaries. Eight pregnancies after CO₂ laser and three after Nd:YAG laser were achieved. Decline of serum androgen concentrations was noted in both groups, but was significantly higher in the Nd:YAG laser group (from 3.4±0.4 ng/ml to 2.2±0.2 ng/ml). Nine patients checked before and after laser treatment showed a decrease in the characteristically exaggerated pituitary response to exogenous GnRH injection. There were no consistent findings of the pattern in LH pulsatility studied in 5 patients after Nd:YAG laser treatment. Ovarian status was investigated in 11 patients by second-look laparoscopy or cesarian section. There were absolutely no adhesions after Nd:YAG laser coagulation. Filmy adhesions were seen in 3 patients in the CO₂ laser group.     

Comparative evaluation of the effects of Nd:YAG and Er:YAG laser in dentin hypersensitivity treatment

Dentin hypersensitivity (DH) is one of the most common complications that affect patients after periodontal therapy. So far, many investigators have successfully used different types of laser on DH treatment. The aim of this study was to evaluate the comparative effect of Nd:YAG laser and Er:YAG laser on human teeth desensitization. A group of nine patients with a total of 63 chronic hypersensitive teeth were selected. Each one of them should at least have three hypersensitive teeth. These teeth were randomly allocated into three groups. Group 1, Nd:YAG laser (1 W, 15 Hz, 60 s, two times); group 2, Er:YAG laser (100 mJ, 3 Hz, 60 s, two times); and group 3 serves as control group without any treatment. Assessment of pain was performed by a visual analysing scale (VAS) after stimulation of sensitive tooth by using the sharp tip of an explorer. This test was performed before treatment, immediately after that and at 1-, 3- and 6-month intervals after treatment by one blinded examiner. Analysis of VAS score between the three groups at the time of treatment did not show any significant difference (p = 0.506). However, by using repeated-measurement analysis of variance test, significant differences were seen in the three groups between before-treatment VAS score and after treatment (p < 0.0005). This statistically significant difference in the control group demonstrated a placebo effect. However, the effect of using Nd:YAG and Er:YAG lasers was stronger than this placebo effect, so that after removing the effect of the placebo, differences immediately after, 1, 3 and 6 months post treatment between all three groups still were statistically highly significant (p < 0.0005). Compared to the Er:YAG laser group, using Nd:YAG laser resulted in a significant reduction of VAS score at each follow-up examination (p < 0.0005). Although using Nd:YAG and Er:YAG laser in desensitization of hypersensitive teeth showed a placebo effect limited to a short time, results of this study demonstrated that both of these lasers have an acceptable therapeutic effect. The observed effects seemed to last for at least 6 months. It was concluded that Nd:YAG laser is more effective than Er:YAG laser in reduction of patients’ pain.     

Photodynamic therapy using pheophorbide a and Nd:YAG laser.

The authors describe a new photodynamic therapy (PDT) method for malignant brain tumors. Pheophorbide a (Ph-a), the photosensitizer, has low toxicity, causes no skin sensitization and is activated with an acoustic Q switched neodymium yttrium-argon-garnet (Nd:YAG) laser which achieves deep tissue penetration. The Ph-a distribution in Fisher 344 (F344) rats bearing rat T9 glioma at 24 hours after intravenous injection was very low in the normal brain tissue, but significantly higher in the T9 glioma giving a tumor to normal brain tissue concentration ratio of 7.5:1. The in vitro survival rate of T9 glioma cells pretreated with Ph-a was 68.8 +/- 5.4% after laser irradiation for 20 minutes, significantly lower than in the control groups. This indicates that Ph-a was activated with the acoustic Q switched Nd:YAG laser causing the photodynamic effect. The survival rate after Ph-a pretreatment and laser irradiation in a waterbath at 44.0 degrees C was further reduced to 15.8 +/- 3.3%. In vivo PDT studies using T9 glioma cells inoculated into the dorsal region of F344 rats showed tumor eradication in four of six rats. The combination of PDT and laser hyperthermia produced tumor eradication in all six rats. The combination of PDT and hyperthermia is a promising method for tumor treatment.     

Laser endoscopic treatment for upper gastrointestinal cancers.

We report the effective clinical use of endoscopic laser in Japan using the results of a nationwide survey and our own experience with more than 100 cases. The Nd:YAG laser and argon dye laser with hematoporphyrin derivative (photodynamic therapy) were most commonly used in digestive endoscopy and were investigated as new modalities of cancer therapy. Photodynamic therapy was fairly effective, especially in superficial esophageal cancer and the ill-defined lesions of early gastric cancer. Endoscopic laser treatment was carried out on 80 patients with 86 lesions of early gastric cancer at our hospital, and the following tumor types were proven highly curable by this means: focal cancer, IIa and so-called "gastritis-like" tumors less than 2 cm in size. The Nd:YAG laser provides a new approach to palliative treatment, such as recanalization of neoplastic obstruction in the advanced stage of gastrointestinal cancers.     

Endoscopic laser therapy of the watermelon stomach.

Endoscopic laser therapy has been used in the treatment of vascular lesions throughout the gastrointestinal tract. The "watermelon stomach" is a pattern of vascular ectasia in the gastric antrum that results in chronic gastrointestinal blood loss and iron deficiency anemia. We have treated 7 transfusion dependent patients with a watermelon stomach using endoscopic laser therapy. Four of these patients were treated with the argon laser and 3 with the Nd:YAG laser. Patient age and prior transfusion requirements were similar in both groups. The mean number of treatments to obliterate vascular lesions and eliminate the need for transfusions was 5.75 +/- 0.89 (SEM) for the argon laser and 2.33 +/- 0.27 for the Nd:YAG laser (P < 0.05). Lesions recurred and required retreatment in 1 patient treated with the Nd:YAG laser and 3 patients treated with the argon laser (mean follow-up of 35 months). We conclude that endoscopic laser therapy with either the argon or Nd:YAG laser is an effective treatment modality for antral vascular ectasia (watermelon stomach). The Nd:YAG laser requires fewer treatment sessions than the argon laser to obliterate the lesions without increased risk of complications.     

Acute effect of the Nd:YAG laser on the cerebral arteriovenous malformation: a histological study

The acute effect of Nd:YAG laser beam on cerebral arteriovenous malformations (AVMs) was examined. Histological examination of the specimens after treatment with the Nd:YAG laser revealed that the most prominent effect of the laser was shrinkage of the collagen of the vessels of the AVM, which led to laser-induced narrowing of blood vessels. The brain tissue confined to the resected AVM did not contain any histological evidence of acute damage. The resection of 10 cases of AVMs was safely accomplished with no morbidity or increased neurological deficits attributable to the laser technique.     

Q开关Nd:YAG美肤激光治疗太田痣317例

目的:观察Q开关Nd:YAG激光系统治疗太田痣的疗效和安全性。方法:应用Q开关Nd:YAG激光仪对317例太田痣患者进行皮损区的多次照射治疗。治疗间隔时间2～3个月,根据皮损不同颜色、部位、年龄及治疗经验选择不同能量和光斑大小。结果:治疗次数与疗效成正比相关,治疗次数越多,效果越好。接受治疗≤5次时,儿童临床效果较成人好;远期疗效儿童组与成人组相同。结论:Q开关Nd:YAG激光治疗太田痣安全有效,预后好。     

Comparison and sequential study of long pulsed Nd:YAG 1,064 nm laser and sclerotherapy in leg telangiectasias treatment

BACKGROUND AND OBJECTIVES: Millisecond pulsed 1,064 nm Nd:YAG lasers have been developed for the treatment of leg telangiectasias. To date there have been very few side by side comparison studies of laser versus the gold standard sclerotherapy in treating small leg veins. This study aims to compare a long pulsed Nd:YAG laser with contact cooling to sclerotherapy for treating small diameter leg telangiectasias by evaluating objective and subjective clinical effects. STUDY DESIGN/PATIENTS AND METHODS: Fourteen patients were selected with leg telangiectasias ranging from 0.5 to 2 mm at four comparable sites. One site was treated with long pulsed Nd:YAG alone, the second received sclerotherapy alone, the third laser then sclerotherapy, and the last one sclerotherapy then laser. The patients were followed up at 3 months after the last treatment. Photographs were taken pre-operatively and at 3 months after the last session. They were used for objective and comparative analysis. Statistical analysis was performed using Friedman's test controlling for subject. RESULTS: Improvement was tabulated from the photographic assessment on an improvement scale from 0 (no change) to 4 (greater than 75% clearing). There were clinical improvements in the laser group than sclerotherapy without statistical significance. Side effects were minimal and included hyperpigmentation. CONCLUSIONS: This pilot study demonstrates that the Smartepil LS long pulse Nd:YAG 1,064 nm laser can yield results similar to sclerotherapy in the treatment of small leg telangiectasias. Combination of both methods could increase response to treatment.     

Persistent elevation in intraocular pressure after Nd:YAG laser treatment

A bilaterally pseudophakic patient, who had no previous evidence of glaucoma, underwent Nd:YAG laser posterior capsulotomy and dispersal of vitreous syneresis opacities of his left eye. The eye developed persistent intraocular pressure elevation and visual field loss, requiring medical therapy and argon laser trabeculoplasty. His fellow eye remained normotensive after Nd:YAG laser posterior capsulotomy. Nd:YAG laser treatment can result in chronic intraocular pressure elevation and glaucomatous visual field loss.     

The pulsed dye laser versus the Q-switched Nd:YAG laser in laser-induced shock-wave lithotripsy

To date, there are two fairly well-established alternatives for laser-induced shock-wave lithotripsy in clinical practice. The Q-switched Nd:YAG laser is distinguished by the high-stone selectivity of its coupler systems. The necessity of a coupler system and its fairly small conversion rate of light energy into mechanical energy present serious drawbacks. Furthermore, the minimal outer diameter of the transmission system is 1.8 mm. The pulsed-dye laser can be used with a highly flexible and uncomplicated 200-micron fiber. However, the laser system itself is more complicated than the Q-switched Nd:YAG laser and requires a great deal of maintenance. Biological evaluation of damage caused by direct irradiation shows that both laser systems produce minor damage of different degrees. YAG laser lithotripsy with the optomechanical coupler was assessed in 31 patients with ureteral calculi. The instability and limited effectiveness of the fiber application system necessitated auxiliary lithotripsy methods in 14 cases. Dye-laser lithotripsy is currently being tested in clinical application. Further development, such as systems for blind application or electronic feedback mechanisms to limit adverse tissue effects, have yet to be optimized. Nevertheless, laser-induced shock-wave lithotripsy has the potential to become a standard procedure in the endourologic management of stone disease.     

光动力疗法联合贝伐单抗玻璃体腔注射治疗脉络膜新生血管患者的护理

对23例脉络膜新生血管患者采取光动力疗法联合玻璃体腔注射贝伐单抗治疗,15例视力提高,8例视力稳定。提出术前做好患者沟通和教育,治疗中密切配合医生操作,光动力疗法术后做好避光护理及饮食指导,玻璃体腔注射贝伐单抗指导合适体位,预防并发症,对确保治疗效果至关重要。