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At least 163 records · Page 9Linked to original sources
PubMed1999

Accuracy of MR phase mapping for temperature monitoring during interstitial laser coagulation (ILC) in the liver at rest and simulated respiration.

The chemical shift or proton-resonance frequency (phase mapping) can be used to measure temperature changes. As a subtraction technique, it requires scans at exactly the same location, making it prone to respiration-induced artifacts. The accuracy of magnetic resonance (MR) phase mapping for temperature monitoring of interstitial laser coagulation (ILC) was therefore investigated in two ex vivo models with simulated respiration. MR temperatures were calibrated to interstitially measured temperature. Gradual cooling of a homogenous medium (gel) was monitored for four starting temperatures (room temperature, 40 degrees C, 50 degrees C, and 60 degrees C) during 30 min. Temperature increases were measured during ILC in ex vivo porcine liver with Nd:YAG for 6 min with 5 Watt. Experiments were performed at rest and with simulated respiratory motion (both n = 5). In liver, accuracy did not decrease with respiration simulation (P = 0.32), whereas a significant decline was found in the gel model (P = 0.002). In all experiments a small drift over time was observed between temperature determined with MR and thermoprobes. Correction for temperature-independent phase-shift at a reference location did not enhance agreement. Temperatures could be determined correctly by MR in the moving liver within a range of +/-3.5 degrees C after 6 min of laser application (95% confidence interval), justifying further pre-clinical studies.

Analysis of Variance↗
PubMed1991

[Laser coagulation of the cornea with a holmium:YAG laser for correction of hyperopia].

We present a new technique of hyperopic correction similar to radial thermokeratoplasty. A pulsed Ho: YAG laser was used that emitted radiation at 2.06 microns and was guided by a quartz fiber and a focusing hand piece. The penetration depth of this light in the cornea is about 400 microns. Eight or 16 concentric point coagulations result in steepening in the central cornea. This refractive change is inverse related to the distance to the cornea center, and it increases linearly with increasing laser pulse energy. In four blind eyes it was demonstrated that the parameters evaluated in cadaver eyes can be transferred to living eyes. Surprisingly, the refractive change so created of up to 5 dpt is stable within a period of 4 months. Immediately after surgery, concentric descemet folds can be detected, which gradually decrease within the period reported.

Cornea↗
PubMed1994

Endoscopic laser coagulation of umbilical cord vessels in twin reversed arterial perfusion sequence.

In monozygotic twin pregnancies with reversed arterial perfusion (TRAP) sequence, the donor twin is ut high risk of perinatal death. This paper describes the use of endoscopic surgery in the management of this condition. In four cases of TRAP sequence presenting at 17, 20, 26 and 28 weeks' gestation, respectively, an endoscope was introduced into the uterus under local anesthesia and a Nd-YAG laser was used to coagulate the umbilical cord vessels of the acardiac twin. Laser coagulation was successful in arresting blood flow to the acardiac fetus in the cases treated at 17 and 20 weeks, and healthy infants were delivered at term. In the pregnancies treated at 26 and 28 weeks, the umbilical cords were very edematous and laser coagulation failed to arrest blood flow; healthy infants were delivered after spontaneous labor at 29 weeks. These findings suggest that, during mid-gestation, endoscopic laser coagulation of the umbilical cord vessels of the acardiac twin is an effective method of treating TRAP sequence. In later pregnancy, alternative methods of treatment are needed.

Journal Article↗
PubMed1986

Endoscopic neodymium:YAG laser coagulation in gastrointestinal hemorrhage.

The aim of a resolute, endoscopic treatment in acute gastrointestinal hemorrhage by a neodymium:YAG laser is to prevent massive loss of blood and to avoid transformation of the hemorrhagic shock event into an irreversible state. Parallel to endoscopic procedure treatment of coagulopathies is necessary. 1,029 (94%) out of 1,092 acute bleeding episodes of 852 unselected patients were treated successfully. In bleeding esophageal varices, reduction of mortality from 70% to 36.2% has been achieved by sclerotherapy following laser coagulation of the acute bleeding. Compared with the results of surgery the mortality rate of bleeding acute ulcers has been reduced from 58% to 23.4%, and of bleeding chronic ulcers from 25% for resection and 15% for vagotomy to 0%. For optimal treatment of the patients close cooperation with surgeons is also desirable.

Acute Disease↗
PubMed1999

[Bleeding from Dieulafoy's ulcer after argon-plasma laser coagulation of gastric angiodysplasia in Heyde's syndrome].

HISTORY: A 75-year-old, pale-looking man with known severe valvar aortic stenosis and three-vessel coronary artery disease previously treated with two bypass grafts was referred for elucidation of anaemia before further coronary artery surgery. INVESTIGATIONS: In addition to chronic iron-deficiency anaemia (haemoglobin 9.5 g/dl) endoscopy revealed gastric angiodysplasia. Endoscopy of the colon was negative. DIAGNOSIS, TREATMENT AND COURSE: Argon-plasma laser coagulation (APC) for the angiodysplasia was performed twice. Although there were no complications at first, five days later tarry stools were noted and hypovolaemic shock developed. Emergency gastroscopy revealed a bleeding vessel stump (Dieufaloy's lesion) proximal to the APC-induced ulcer (stage Ib bleeding [Forrest's classification]). Epinephrine and fibrin glue were applied endoscopically. The patients died 20 days later of septicaemic and multiorgan failure, the result of left-heart failure with pneumonia. CONCLUSION: APC, usually described as being a low-risk procedure, can cause mucosal damage resulting in Dieulafoy's lesion. APC should therefore be carefully monitored.

Aged↗
PubMed1987

Function of the diabetic retina after panretinal argon laser coagulation.

Panretinal photocoagulation has been demonstrated to have a beneficial effect on the natural history of diabetic retinopathy. However, it is associated with detectable loss of retinal function. To determine the best coagulation technique we conducted a prospective study in 32 eyes of 16 patients. We investigated retinal function in relation to spot size and scatter density after panretinal laser coagulation. One eye was treated with approximately 400 comparatively large laser spots (0.6-0.8 mm diameter), whereas the fellow eye was coagulated with approximately 1500 small spots (0.2-0.4 mm diameter), so that the total coagulated area was almost the same in both eyes. Subjective parameters (visual acuity, perimetry, dark adaptation, photostress), as well as objective functions (electroretinogram, ERG; electro-oculogram, EOG), were studied preoperatively and then postoperatively over a time span of 6 months. Pronounced impairment of retinal function was detected, which recovered after 3 months on the average. When the pairs of eyes were compared, persistent visual field scotomas as detected by computerized static perimetry, occurred less frequently in eyes subjected to small coagulation spots, although this tendency was not statistically significant.

Adult↗
PubMed1984

[Argon laser coagulation in exudative senile macular degeneration].

In 26 of 76 eyes with exudative senile macular degeneration, visual acuity improved after argon laser coagulation. However, in most cases the improvement was only of short duration. The treatment was of greater benefit in cases with serous pigment epithelial detachment where there was no subretinal neovascular membrane.

Age Factors↗
PubMed2005

[Transurethral resection for prostatic adenoma larger than 100 ml--preoperative treatment with interstitial laser coagulation of the prostate plus chlormadinone acetate as a treatment maneuver for safer operations].

Between August 1985 and March 2004, we performed transurethral resection of the prostate (TURP) in 18 patients with benign prostatic hyperplasia (BPH) whose prostatic volume was larger than 100 ml. We divided the patients into two groups. Group A consisted of a total of 14 cases: 10 cases whose mean prostate volume was 114 ml (100 to 137 ml) and 4 cases whose prostate volume was not measured before TURP but whose mean resected prostatic tissue weight was 113 g (105 to 118 g). Group B consisted of 4 cases whose mean prostate volume was 110 ml (101 to 133 ml). Patients in group B underwent interstitial laser coagulation of the prostate (ILCP) followed by oral chlormadinone acetate (CMA) therapy (50 mg/day); TURP was performed 6 months later, once the prostate volume had shrunk to an average of 76 ml (66 to 91 ml). Mean resected weights and operation times were: group A, 93.1 g, 66.3 min; group B, 60.5 g, 55.7 min. There were 12 blood transfusion cases (85.7%; intraoperative) in group A, and 1 (25.0%; POD 1) in group B. Accordingly, this preoperative treatment was considered a safer method of TURP for BPH 100 ml or more. There were no cases of TURP syndrome or death in either group.

Aged↗
PubMed1985

Cellular mechanisms of resolution of drusen after laser coagulation. An experimental study.

Naturally occurring drusen in two eyes of a rhesus monkey resolved after the application to the retina of mild laser coagulation. Clinically, resolution took place approximately nine days following treatment. The cellular mechanism for resolution was observed by light and electron microscopy over a time period of three days to six weeks after treatment. A previously unidentified phagocytic cell, probably derived from the pericyte of the choriocapillaris, was observed to remove drusenoid material after laser photocoagulation. The cell appeared to be analogous to the mesangial cell of the renal glomerulus.

Animals↗
PubMed1989

Free running Neodymium-YAG laser coagulation of the human fovea. A light and electron microscopic study.

Free Running Neodymium-Yttrium Aluminum Garnet (FR Nd-YAG) laser coagulation of the macula was performed in seven human eyes. Follow-up varied from 1 to 15 days. Damage to the outer retinal layers was apparent immediately after exposure whilst that in the inner retinal layers developed subsequently. The choriocapillaris and major choroidal vessels were occluded. Visual acuity changed in an unpredictable way.

Adult↗
PubMed1986

[Long-term study following panretinal argon laser coagulation in proliferative diabetic retinopathy].

Fifty-eight Type I diabetics were followed up for a minimum of 5 years after panretinal argon laser coagulation in both eyes for proliferative diabetic retinopathy. During the course of this study, 18 patients were excluded because thorough follow-up examinations according to our systematic approach had become impossible. The results of this study indicate that successful photocoagulation depends essentially on the initial findings, on the type and extent of treatment as well as on regular and thorough follow-up examinations.

Adult↗
PubMed1994

Development and experimental in vivo validation of mathematical modeling of laser coagulation.

Most clinical procedures using the laser are based on thermal laser-tissue interactions. The treatment often consists of inducing damage of given degree and extent by heating the tissue. The aim of this study was to develop a model called HELIOS. The ability of HELIOS to predict thermal coagulation was evaluated by comparison with in vivo experimental results. Conversion of laser light in tissue was studied using the beam-broadening model. Temperature was described by the heat conduction equation solved using the finite difference method. The tissue denaturation was modeled by the Henriques equation leading to the determination of the damage coefficient omega. For a given set of laser and tissue parameters, HELIOS makes a graphic representation of coagulation necrosis and temperature evolution in tissue. HELIOS was validated by experimental studies in vivo on rat liver using a CW Nd:YAG laser, a CO2 laser, and an argon laser. For given sets of laser parameters, temperature measurements were performed using an infrared camera. Histological examinations were carried out on samples to quantify the depth of coagulation necrosis. Experimental data obtained in vivo were compared with those calculated using HELIOS and similar sets of parameters. The difference between the predicted temperature evolution on tissue surface and that measured by the infrared camera was < 5 degrees C in all cases. The difference between the predicted coagulation necrosis depth and the corresponding experimental one was < 10%. In conclusion, HELIOS allows good prediction of tissue temperature and coagulation necrosis.

Animals↗
PubMedDate not supplied

Analysis of prophylactic laser coagulation of retinal defects and degenerations performed in patients of the Free University of Amsterdam during the period from 1982 to July 1986.

In order to evaluate the prophylactic effect on retinal detachment a retrospective analysis was made of the prophylactic laser coagulations for retinal defects and degenerations performed on patients of the Free University of Amsterdam during the period from 1982 to July 1986. The main conclusion is that in a total of 273 treated eyes only two developed a spontaneous retinal detachment after coagulation. This is an incidence of 0.7%, which compares favourably with untreated groups. The treatment criteria were: 1. symptomatic defects; 2. defects and degenerations in fellow eyes; 3. asymptotic defects in aphakia, myopia greater than 5 D, single eyes and a positive family history. The most frequent complication was vitreous haemorrhage due to rupture of a patent vessel bridging the detached lip of a horseshoe tear, but vision was restored to normal in all but one case after the haemorrhage cleared.

Humans↗
PubMed1993

Interstitial laser coagulation of the prostate. An experimental study.

We describe a percutaneous, low power, interstitial method of controlled coagulation of prostatic tissue by laser light which may prove an alternative or adjunct to existing therapy for benign and malignant prostatic disease. One or more 200-600 micron diameter fibres were implanted within the substance of the elderly male beagle prostate (n = 11) through which Neodymium-Yttrium Aluminium Garnet (Nd-YAG) laser energy could be transmitted. Using longer exposures (400-1500s) and lower powers (1-2W) than used in routine endoscopic laser therapy, well defined areas of coagulative necrosis could be created with little tissue charring or damage to the fibre. For an energy dose of 1000J a lesion approximately 1 cm in diameter resulted at 4 days. Ultrasound scanning methods could detect the fibre(s), the area(s) of coagulation and the healed lesions. Treatments were well tolerated. At 6 weeks the treated areas of canine prostate healed by fibrosis surrounding an area of cystic degeneration. Multiple fibre experiments produced larger volume lesions relevant to more extensive cancer or to the coagulation of benign adenomatous hyperplasia causing outflow symptoms. This technique may prove of value for the treatment of moderate benign enlargement of the prostate and for the destruction of small, focal prostatic tumours.

Animals↗
PubMed1998

Interstitial laser coagulation of the prostate: minimally invasive therapy for benign prostatic hyperplasia.

The morbidity and mortality associated with transurethral resection of the prostate (TURP), as therapy for benign prostatic hyperplasia (BPH), is the impetus for the urological community's search for alternative medical and surgical treatments for BPH. Interstitial Laser Coagulation of the Prostate (ILC) is a minimally invasive procedure usually performed to relieve symptomatic BPH, that is accomplished by directing laser energy into the gland via an implanted optical fiber using standard cystoscopic techniques. Treatment of adenomatous tissue with ILC reduces the size of the prostate and disrupts alpha-adrenergic nerve fibers.

Journal Article↗
PubMed1993

Water jet guided Nd:YAG laser coagulation--its application in the field of gastroenterology.

With the water jet guided laser, a comparatively new transmission system has become available, with the aid of which the laser beam is conducted from the end of the transmission fibre of the conventional light guide system to the target tissue via a water jet. The extra costs of this modality are low. The technique is easy to apply, and is associated with a number of technical advantages, such as absence of smoke and carbonisation, reduction in organ distension, etc. The water jet guided laser brings about volume coagulation in the deeper layers of the wall, with concomitant oedema and hyperaemia in the periphery. In a randomised, prospective controlled study, 89 patients with gastroduodenal ulcers bearing a visible vessel were treated with the Nd:YAG laser (wavelength 1.064 nm), 43 with the non-contact, and 46 with the water jet guided modality. In the water jet group a smaller number of bleedings were induced (p < 0.05) and fewer failures, emergency operations and deaths occurred. The technical advantages of the method, together with the results of treatment in 20 tumour patients with adenomas (n = 6) and adenocarcinomas in the colorectum (n = 14) with readily achievable tumour debulking (n = 13) or complete eradication (n = 7), suggest that the use of the water jet guided laser might also be appropriate for the treatment of tumours.

Adenocarcinoma↗