Excimer laser induced bubble: dimensions, theory, and implications for laser angioplasty

BACKGROUND AND OBJECTIVE: Previous studies have demonstrated that during Xenon-Chloride excimer laser ablation of tissue, rapidly expanding and imploding bubbles (diameter < 3 mm), predominantly containing water vapor, are formed. These short lived bubbles (life time < 300 microseconds) induce mechanical damage in adjacent tissue. In the present study, a theoretical analysis of the volume of vaporized water is correlated with measured bubble volumes formed in hemoglobin solution. STUDY DESIGN/MATERIALS AND METHODS: The dimensions of the rapidly expanding and imploding vapor bubble induced by the XeCl excimer laser pulses (308 nm, 115 ns), delivered via a 300, 550, or 950 microns diameter monofiber in 16% w/v hemoglobin solution (at 37 degrees C), were measured. RESULTS: Theoretical analysis and the experimental data correlated well (correlation coefficient r = 0.97). The diameter of excimer laser induced bubbles increased with increasing pulse energy. For a given radiant exposure, the bubble size was decreased by either decreasing the fiber tip area or by decreasing the absorption coefficient of the hemoglobin solution. CONCLUSION: We conclude that, for a wide range of conditions, theory agrees well with experimental data. Thus, during delivery of excimer laser pulses in blood, bubble dimensions can be reduced by flushing with saline or by reduction of the area radiated with each laser pulse, for example, by pulse multiplexing or using a smaller multifiber catheter.     

Laser angioplasty and recanalization

Percutaneous transluminal coronary balloon angioplasty (PTCA) still is the most frequently applied interventional technique for treatment of coronary artery disease. Plastic deformation of the obstructive plaque with creation of splits, intimal tears and dissections is the main mechanism of PTCA for lumen widening. As a result, acute complications due to flow limiting dissections and acute vessel closure can unpredictably occur resulting in myocardial infarction, urgent bypass surgery and death. Furthermore, long-term success of PTCA is limited by restenosis. In order to overcome these limitations of PTCA, alternative interventional techniques were developed, which instead of deforming the obstructive plaque ablate this tissue. These techniques include high and low speed rotational angioplasty, directional atherectomy, the transluminal extraction catheter, ultrasound angioplasty and laser (Light Amplification by Stimulated Emission of Radiation) angioplasty. 308 nm XeCl excimer laser angioplasty today is the laser technique of choice for clinical application. This pulsed laser requires direct contact to the obstructive plaque. It creates fast (< 200 microseconds) expanding gas bubbles which induce plaque ablation. Main indications for 308 nm XeCl excimer laser angioplasty are diffuse and long coronary lesions and total coronary occlusions. Despite promising initial results this technique showed no better acute and long-term results in comparison to PTCA for the treatment of these types of lesions ("Amsterdam-Rotterdam" Study, "Excimer Rotational Balloon Angioplasty Comparison" Study). As a result, this interventional technique was rarely applied for patient treatment. More recently, the concept of plaque ablation by 308 nm XeCl excimer laser angioplasty was renewed for the treatment of in-stent restenosis. This indication is being investigated in the "Laser Angioplasty of Restenosed Stents" trial. First results document the practicability and safety of this approach. Long-term results are awaited. With ongoing miniaturization, laser guidewires were developed for the recanalization of chronic total occlusions. The randomized multicenter "Total Occlusion Trial with Angioplasty assisted by Laser guidewire "Study documented a success rate of laser wire recanalization in up to 66% in contrast to 47.5% for mechanical wires only. Long-term results are still awaited. Technical and procedural progress including saline flush during laser application, homogeneous light distribution and the concept of smooth laser ablation is pushed foreward to make excimer laser angioplasty safer, more predictable and more effective.     

Mid-infrared pulsed laser ablation of the arterial wall. Mechanical origin of "acoustic" wall damage and its effect on wall healing

Pulsed mid-infrared lasers are an alternative to excimer lasers for transluminal angioplasty. The mid-infrared lasers, however, were reported to produce "acoustic" wall damage that might impair the immediate and long-term results. To study the immediate and long-term effects on the arterial wall, 184 craters (1 mm diameter and 1 mm depth) were produced perpendicular to the intimal lining in the thoracic aortas of pigs. Three types of craters were evaluated: Ho-YSGG laser-induced (lambda = 2.09 microns, 2 pulses of 500 microseconds, 0.50 joule/pulse, 50 gm force), mechanically drilled, and "acoustic" craters. "Acoustic" craters were produced by two laser pulses delivered into a saline-filled metal fiber cap, which was placed in a mechanically drilled crater. The metal cap was provided with four outlets for water vapor and isolated "acoustic" from optical and thermal laser effects. The pigs survived 3, 14, and 28 days. Arterial wall damage, medial necrosis, and wall healing were assessed microscopically. At 3 days, laser and "acoustic" craters were accompanied by large tissue ruptures (2.7 +/- 0.9 mm and 2.9 +/- 0.8 mm, respectively, mean +/- standard deviation). These were attributed to large vapor bubbles expanding within the tissue. A zone of medial necrosis was observed adjacent to the laser craters (0.43 +/- 0.15 mm) and to the "acoustic" craters (0.17 +/- 0.14 mm). Neither ruptures nor necrosis was observed with the mechanical craters. At 2 and 4 weeks, the necrotic areas were repopulated with smooth muscle cells and all craters were adequately filled with smooth muscle cells, without any sign of an exaggerated proliferative response. We conclude that within the arterial wall, Ho-YSGG ablation was accompanied by the rapid expansion of a water vapor bubble. The formation of the relatively large vapor bubble is inherent to the use of a mid-infrared laser. The risk of creating dissections clinically, when delivering Ho-YSGG laser pulses, remains to be determined. The present study provided no indication that the arterial wall fissures might affect the restenosis rate unfavorably by promoting myointimal proliferation.     

Adult moyamoya disease progressing from unilateral to bilateral involvement

The effect of domestically-manufactured excimer laser with adjunctive balloon angioplasty in achieving revascularization and reduction of residual stenosis was assessed. 20 femoral arteries with thrombosis and occlusion from 12 dogs were subject to angiography. At first excimer laser angioplasty was done followed by balloon angioplasty. The diameter and residual stenosis of revascularized vessel were measured. The result showed that 17 out of 20 vessels (85%) were revascularized. The diameter of revascularized vessel by excimer laser were 1.22 +/- 0.14 mm, while residual stenoses were 54% +/- 5%. After adjunctive balloon angioplasty the diameter and residual stenoses were 2.04 +/- 0.16 mm and 20% +/- 7% respectively (P < 0.05 and P < 0.01). Complication in form of vasoperforation occurred in 3/20 vessels (15%). It is concluded that China- manufactured excimer laser angioplasty is effective when used for revascularization. While the reduction of narrowing and residual stenoses was enhanced after adjunction of balloon angioplasty. This method can be employed in treating peripheral occlusive disease effectively and safely.     

Saline flush during excimer laser angioplasty: short and long term effects in the rabbit femoral artery

BACKGROUND AND OBJECTIVE: In this study, the effect of flushing saline on arterial wall damage (medial ruptures and necrosis), intimal hyperplasia, and arterial remodeling was determined. During excimer laser coronary angioplasty saline is flushed to reduce the size of explosive water vapor bubbles formed by intraluminal delivery of excimer laser pulses in blood. METHODS: In the femoral artery of the rabbit, 600 excimer laser pulses (308 nm, 50 mJ/mm2 per pulse, 20 Hz) were delivered coaxially over a length of 20 mm in 10 bursts of 3 seconds each. In 24/48 procedures, saline was flushed (0.2 ml/s) via the guidewire channel. After 2 and 56 days, microscopic and angiographic results were compared. RESULTS: At 2 days, as compared to lasing in blood, saline flush had drastically reduced the incidence of dissections (2/12 vs. 11/12, P < 0.002), but had increased the extent of medial and adventitial necrosis. The latter is attributed to direct irradiation of the arterial wall. After 56 days, in the saline group, in the middle-distal part of treated segments, medial necrosis without intimal hyperplasia was observed. However, at the edges of these lesions, intimal hyperplasia and arterial shrinkage reduced the lumen. CONCLUSION: Flushing saline during coaxial excimer laser pulse delivery significantly reduced the incidence of vessel wall ruptures, and prevented intimal hyperplasia formation in part of the lesion. The histologic findings at 56 days are attributed to the optical window which the saline flush provides for direct ultraviolet light irradiation of the arterial wall.     

Ablation dynamics in laser sclerostomy Ab externo by means of pulsed lasers in the mid-infrared spectral range

BACKGROUND AND OBJECTIVE: Sclerostomy ab externo with pulsed laser systems is currently in phase II clinical trials. The authors investigated the ablation dynamics of tissue treated with pulsed laser systems in the mid-infrared range to estimate the extent of thermo-mechanical damage to the sclera and the anterior chamber. MATERIALS AND METHODS: Freshly harvested porcine eyes were used. A bare 400-micron fiber in direct contact with tissue was used for fistulization. Polarization light microscopy, fast-flash photography, as well as optical and acoustic transients were performed for analysis. RESULTS: Substantial mechanical tissue deformation and dissections were found during pulsed laser ablation. The mechanical damage range within tissue far exceeds the pure thermal damage zone. Aspheric cavitation bubbles of up to 3 mm in length penetrate the anterior chamber after perforation. The cavitation demonstrates a significantly larger time constant in tissue than in water. CONCLUSIONS: Early fistula occlusions due to iris adherences may be attributed to iris trauma caused by cavitation. In response to the findings of this study, the authors propose an automatic feedback system to control the ablation process and minimize secondary ocular tissue effects. With respect to the overall damage zones, a new continuous-wave, mid-infrared diode laser system seems to be superior to pulsed laser systems.     

Excimer laser-facilitated angioplasty for undilatable coronary narrowings

Calcified and fibrotic coronary artery lesions cannot always be dilated with conventional balloon angioplasty even at high pressures. This study examines the success of excimer laser facilitated angioplasty in 38 lesions in 37 patients with lesions that failed balloon angioplasty alone.     

Short-term results and intermediate-term follow-up of laser wire recanalization of chronic coronary artery occlusions: a single-center experience

OBJECTIVES: This study sought to elucidate the short-term efficacy and intermediate-term outcome of excimer laser recanalization of chronic coronary artery occlusions in patients in whom attempts at mechanical revascularization had failed. BACKGROUND: Recanalization of chronic coronary occlusions with the use of a mechanical guide wire fails in 30% to 50% of cases, mostly because of inability to pass the wire through the lesion. The value of using excimer laser energy in this setting has not yet been determined. METHODS: The study group comprised 66 consecutive patients with 68 chronic coronary occlusions. Patients were eligible for inclusion in the study if a previous attempt at mechanical revascularization had failed and if their angiographic status was such that 1) the vessel segment distal to the occlusion could be visualized by way of collateral vessels, 2) the entry point of the occlusion was clearly outlined, and 3) not more than one anatomic bend was expected within the occlusion. Excimer laser energy was applied to the lesion through a 0.018-in. (0.046 cm) fiber-optic guide wire. Adjunctive balloon angioplasty and stenting were performed in all successfully treated patients but one. RESULTS: Thirty-four occlusions (50%) in 32 patients (48%) could be crossed with the laser wire. Location and age of the occlusion had no adverse influence on the outcome of laser wire recanalization, nor did the presence of bridging collateral vessels, a major side branch at the site of the lesion or a blunt stump of the occlusion. An inverse relation was found between the success rate and the length of the occlusion, such that a 19% reduction of the success rate accompanied each 10-mm increment of the mean occlusion length. Thus, the success rate was 68% for lesions < or = 10 mm but only 25% for lesions > 30 to < or = 40 mm. The presence of a bend in the lesion exceeding 60 degrees was strongly related to procedural failure. During a median angiographic follow-up period of 18 weeks, restenosis > 50% (n = 6) or reocclusion (n = 4) was found in 10 of the 32 successfully treated patients, for an intermediate-term success rate of 33% (22 of 66). Clinical follow-up revealed improved anginal status in 21 patients (66%) after a median of 24 weeks. Major complications (death, myocardial infarction, emergency operation) were not encountered. CONCLUSIONS: Successful recanalization of a chronic coronary occlusion by using currently available laser wires can be expected in 50% of selected patients in whom attempts at mechanical revascularization fail. Restenosis or reocclusion accounts for an overall 6-month success rate of 35%.     

Excimer laser angioplasty versus balloon angioplasty in functional and total coronary occlusions

Registries of excimer laser coronary angioplasty have reported good results in the treatment of complex coronary artery disease, including total or subtotal coronary occlusions. One hundred three patients (103 lesions) with a functional or total coronary occlusion were included in a randomized trial (Amsterdam-Rotterdam [AMRO] trial, total of 308 patients), 49 patients were allocated to laser angioplasty and 54 patients to balloon angioplasty. The primary clinical end points were death, myocardial infarction, coronary bypass surgery, or repeated coronary angioplasty of the randomized segment during a 6-month follow-up period. The primary angiographic end point was the minimal lumen diameter at follow-up in relation to the baseline value (net gain), as determined by an automated contour-detection algorithm. Laser angioplasty was followed by balloon angioplasty in all procedures. The angiographic success rate was 65% in patients treated with excimer laser-assisted balloon angioplasty compared with 61% in patients treated with balloon angioplasty alone. No deaths occurred. There were no significant differences between the laser angioplasty group and the balloon angioplasty group in the incidence of myocardial infarctions (1 patient vs 3, respectively, p = 0.36), coronary bypass surgery (4 patients vs 2, respectively, p = 0.34), repeat angioplasty (10 patients vs 8, respectively, p = 0.46) or primary clinical end point (15 patients vs 12, respectively, p = 0.34). The net gain in minimal lumen diameter and restenosis rate (>50% diameter stenosis at follow-up) were 0.81 +/- 0.74 mm and 66.7%, respectively, in patients treated with laser angioplasty compared with 1.04 +/- 0.68 mm and 48.5%, respectively, in patients treated with balloon angioplasty (p = 0.59 and p = 0.15, respectively). Excimer laser-assisted balloon angioplasty demonstrated no benefit over balloon angioplasty with respect to initial and long-term clinical and angiographic outcome in the treatment of patients with functional or total coronary occlusions of >10 mm in length.     

Picosecond laser in situ keratomileusis with a 1053-nm Nd:YLF laser

BACKGROUND: Excimer laser in situ keratomileusis requires a microkeratome to generate an anterior corneal flap, plus an excimer laser to ablate the underlying stromal tissue. In this paper we introduce the concepts of laser flap formation and in situ keratomileusis using a picosecond laser. METHODS: A neodymium-doped yttrium-lithium-fluoride (Nd:YLF) laser with a plano-plano quartz applanation lens was used to generate various patterns of intrastromal photodisruption in human donor eyes to fashion anterior corneal flaps and generate intrastromal lenticules. RESULTS: Smooth intrastromal dissections, 6 mm in diameter, were generated 160 microns below the corneal surface when the laser delivered pulses at 1 kHz with energies of either 40 microJ/pulse or 60 microJ/pulse, placed 20 microns apart in an expanding spiral. This enabled us to fashion anterior corneal flaps. The ease of the surgery and quality of the dissection corresponded well, and it was evident that both deteriorated noticeably when the laser pulses were separated by 25 microns or 30 microns, regardless of pulse energy. Using 40 microJ laser pulses placed 20 microns apart we also created a 5-mm diameter, 320 microns thick (130 microns-450 microns deep) stromal lenticule below a corneal flap that was easily extracted when the flap was raised. CONCLUSIONS: Anterior corneal flaps were easily fashioned using a Nd:YLF laser. Picosecond laser in situ keratomileusis with a Nd:YLF laser could offer a favorable alternative to combined microkeratome/excimer laser in situ keratomileusis.     

Single-laser approach for fluorescence guidance of excimer laser angioplasty at 308 nm: evaluation in vitro and during coronary angioplasty

BACKGROUND AND OBJECTIVE: Spectroscopic guidance of laser angioplasty has been attempted using a diagnostic He-Cd laser in addition to the therapeutic laser system. This study evaluated a single-laser approach for simultaneous ablation and fluorescence excitation. STUDY DESIGN/MATERIALS AND METHODS: A spectroscopy system was coupled to a clinical XeCl excimer laser. Ablation of 162 human aortic samples in saline and blood with 45 mJ/mm2 per pulse yielded 676 fluorescence spectra validated histologically. The same equipment was used in 16 patients for angioplasty of 18 coronary stenoses applying 500 to 1,725 pulses with 45 to 60 mJ/mm2 under saline flushing. A total of 783 spectra were recorded and validated by intracoronary ultrasound (categories: atheroma, fibrous plaque, calcified lesion). RESULTS: In vitro, 5 types of spectra could be differentiated: (1) atheroma, (2) fibrous plaque, (3) calcified lesion in saline, (4) media, and (5) calcified lesion in blood. Discriminant analysis prospectively classified 576 validation spectra with the following sensitivity and specificity for each type: (1) 83.5 and 97.1%, (2) 85.7 and 96.8% (3) 100 and 98.5%, (4) 98.1 and 99.3%, (5) 98.9 and 100%, respectively. In vivo type 1, 2, 3, and 5 spectra were also observed, but not the media spectrum. The predominant sonographic category also prevailed in spectroscopy. Calcified lesions yielded type 3 and 5 as well as mixed spectra. CONCLUSIONS: Using an excimer laser for angioplasty allows combining ablation and fluorescence excitation without a diagnostic laser. Principal types of atherosclerotic lesions and the media can be differentiated spectroscopically with this approach.     

Factors determining the refractive effects of intrastromal photorefractive keratectomy with the picosecond laser

PURPOSE: To determine the relationship between laser parameters and tissue removal with picosecond laser intrastromal photorefractive keratectomy (ISPRK) and to assess the effect of the parameters on the healing process and the long-term refractive changes. SETTING: Medical Laser Center Lübeck, Germany. METHODS: A modified Intelligent Surgical Lasers (ISL) 2001 system with a cone angle of 30 degrees was used for in vitro investigations of the laser effects in water and on the porcine cornea. Photographic methods were used to determine the plasma volume and to investigate the thickness of the intrastromal bubble layer as a function of the laser pulse energy, the number of layers in which the pulses were applied, and the layer separation. The data were used to calculate the amount of tissue removal. Histologic evaluation was done by polarization microscopy after Sirius-red staining. RESULTS: The laser pulses produced a sponge-like appearance of the stroma in a layer extending through about one third the corneal thickness, accompanied by mechanical distortions of the stromal lamellae. Thermal changes were weak. Tissue removal was impaired by the cavitation bubbles from preceding laser pulses. The amount of evaporated tissue depended only weakly on laser pulse energy and number of layers in which the pulses were applied. The maximum amount of tissue that could be evaporated without damaging the outer corneal layers was a 10.0 microm thick layer. With a 6.0 mm optical zone, the tissue removal produced an immediate refractive effect of only 0.85 diopter. CONCLUSIONS: Intrastromal PRK does not work as originally envisioned because the amount of evaporated tissue is very small. The greater long-term refractive changes observed in animal experiments and clinical studies must therefore be due to the healing response of the cornea. Because the refractive effects are strongly influenced by the healing response of the cornea, they are poorly predictable.     

Prevalence of cardiovascular diseases in elderly Chinese people in Taiwan

PURPOSE: To analyze whether nonmechanical trephination with an excimer laser influences post-operative blood-aqueous barrier breakdown after penetrating keratoplasty. METHODS: Patients undergoing penetrating keratoplasty for keratoconus or Fuchs dystrophy were prospectively randomly assigned to trephination by either excimer laser or conventional mechanical handheld motorized trephine. All surgery was performed by one surgeon, and preoperative, intraoperative, and postoperative treatment was identical in both groups. Aqueous flare was quantitatively determined postoperatively in a masked fashion by laser flare-cell meter. For statistical analysis, the nonparametric Wilcoxon-Mann-Whitney test was used. RESULTS: A total of 52 eyes of 52 patients were examined (Fuchs dystrophy, 10; keratoconus, 42). During the early postoperative period (days 3 to 9), eyes that had undergone nonmechanical excimer laser trephination (25/52) showed significantly (P < .005) lower flare values than did eyes that had undergone mechanical trephination (27/ 52). In both groups, flare values returned to normal levels by 6 weeks postoperatively. CONCLUSION: Early postoperative blood-aqueous barrier breakdown is less pronounced after penetrating keratoplasty with nonmechanical excimer laser trephination.     

Complement-derived anaphylatoxins in human donor corneas treated with excimer laser

BACKGROUND AND OBJECTIVE: An inflammatory response produced by excimer laser photorefractive keratectomy (PRK) may be associated with the subsequent corneal haze and regressions in refractive error observed after treatment. Complement-derived anaphylatoxins, potent mediators of inflammation, may have a role in postoperative healing. MATERIALS AND METHODS: Twenty right human donor corneas underwent a 6-D excimer laser PRK treatment. The corresponding left donor corneas served as the controls. After incubation in tissue culture media for 6 hours and elution in phosphate-buffered saline with EDTA for 24 hours, complement-derived anaphylatoxins C3a, C4a, and C5a were measured in corneal eluates by radioimmunoassay. RESULTS: Compared with control corneas, the excimer PRK corneas failed to demonstrate a significant increase in C3a, C4a, or C5a levels (P > .05). CONCLUSIONS: These results suggest that the excimer laser at this dose does not activate significant complement in the cornea.     

Hepatic energy and substrate metabolism: a possible metabolic basis for early nutritional support in cirrhotic patients

Excimer laser photorefractive keratectomy and excimer laser in situ keratomileusis are relatively new treatment modalities that can be used to correct refractive errors of the eye. They are most commonly used to correct myopia (nearsightedness) but can also be used to correct hyperopia (farsightedness) and astigmatism. The excimer laser alters the refractive state of the eye by removing tissue from the anterior cornea through a process known as photoablative decomposition. This process uses ultraviolet energy from the excimer laser to disrupt chemical bonds in the cornea without causing any thermal damage to surrounding tissue. The modified anterior corneal surface enables light to be focused on the retina, thereby reducing or eliminating the dependence on glasses and contact lenses. We discuss in detail all aspects of excimer laser refractive surgery--techniques, indications and contraindications, clinical outcomes, and complications.     

Effects of ArF:excimer laser irradiation on human enamel and dentin

Round enamel and dentin surfaces of sound and carious extracted human teeth were irradiated by an ArF:excimer laser for up to 180 sec. Thermographic measurements indicated that the temperature rise due to heat accumulation caused by laser irradiation on these enamel and dentin surfaces was up to 19 degrees C (10 HZ with 540 J/cm2), and the temperature returned to the preirradiation value within 10 sec after the irradiation was stopped. Under light microscopy, no carbonization was evident on these surfaces, and a simple recess was formed by abrasion or vaporization in the irradiated regions. In the secondary SEM, uniformly distributed fine pores and prism structures appeared slightly on the enamel surfaces. Between the peritubular and the intertubular dentin, there appeared a distinct difference in the dissolved area. The laser almost completely removed carious regions of the enamel and the dentin, and penetration extended beyond the carious regions. In the backscattered electron SEM, highly mineralized layers were observed on the enamel and dentin surfaces dissolved by the laser.     

Polymorphism of Mhc-DRB alleles in Cercopithecus aethiops (green monkey): generation and functionality

PURPOSE: To evaluate the use of scanned intrastromal picosecond and femtosecond laser pulses in lamellar refractive surgical procedures. METHODS: Intrastromal corneal photodisruption was performed in fresh porcine and primate cadaver eyes with a solid-state femtosecond laser. Laser pulses were focused 150 to 200 microns below the epithelial surface and scanned in a spiral pattern to create a plane. A flap was made by scanning an arc pattern from the plane of the spiral to the surface of the cornea. Tissue plane separation was graded using a standard scale, while internal surfaces were analyzed by scanning electron microscopy. Comparison was made to a picosecond laser system using the same delivery system device. Creation of a stromal lenticule for in situ keratomileusis was also demonstrated and compared with both laser systems. RESULTS: For femtosecond pulses, tissue separation was achieved best with pulse energies from 4 to 8 microJ and spot separations from 10-15 microns. Picosecond pulses accomplished less complete separations with pulse energies of 25 microJ and spot separations from 10 to 20 microns. Surface quality corresponded to dissection results, with high-grade dissections resulting in a smooth surface appearance, versus a more irregular surface for low-grade dissections. Although high-grade dissections could be created with picosecond pulses (with optimal parameters) in ex vivo porcine eyes, only femtosecond parameters produced similar results in ex vivo primate eyes. CONCLUSION: In contrast to previous attempts using picosecond lasers which require additional mechanical dissection, high precision lamellar refractive surgery may be practical with femtosecond laser pulses.     

Biliary cystadenoma. A report of 2 cases]

The application of laser/thermal energy in arthroscopic shoulder surgery remains controversial. Laser proponents tout the benefits of coagulation and vaporization of tissue, whereas opponents cite costs, complications, and the fact that the laser has not yet shown results superior to presently available mechanical techniques. A lack of basic science studies and the aversion of many physicians to the marketing aspects of laser technology have undermined the widespread orthopaedic acceptance of laser techniques. Newer applications, such as capsular shrinkage are just now being evaluated as to effect and efficacy. Orthopaedists should be assured that, at present, they are not compromising patient care by not using laser techniques.     

Large ovarian endometriomas

The management of large endometriomas was described in a series of 814 patients. Combined therapy using gonadotrophin-releasing hormone agonist (GnRHa) and carbon dioxide laser laparoscopy was proposed. Drainage and GnRHa for 12 weeks provoked a reduction of the endometrioma size up to 50% of the initial value. After vaporization of the internal wall, a cumulative pregnancy of 51% after 1 year was achieved. A recurrence rate of 8% was observed for a follow-up of 2-11 years. Histological data demonstrated that the epithelium covering the ovary which is the mesothelium can invaginate in the ovarian cortex. Some of the invaginations were seen to be continuous with endometrial tissue, strongly suggesting the metaplasia theory in the pathogenesis of ovarian endometrioma.     

Carbon dioxide laser-assisted hair transplantation. The effect of laser parameters on scalp tissue--a histologic study

BACKGROUND: "Char-free" carbon dioxide lasers are capable of precise tissue vaporization with minimum residual thermal damage. These lasers deliver very high bursts of energy for extremely short durations, and can vaporize recipient sites during hair transplantation, which are consistent in depth and diameter. OBJECTIVE: To determine the depth of ablation and lateral thermal damage of scalp tissue using various laser parameters with the Sharplan 80XJ Silklaser. METHODS: Two hundred forty laser recipient sites were created, using 24 different laser parameters in each of 10 specimens of scalp tissue removed during scalp reduction. These specimens were evaluated histologically for depth of ablation and lateral thermal damage. RESULTS: While some laser parameters worked better regarding consistent depth of ablation of scalp tissue, lateral thermal damage was quite narrow (average, 20-50 microns). CONCLUSIONS: None of the laser parameters tested in this study should be problematic when used clinically for hair transplantation.