Catheter associated problems of multi-fibre systems in clinical excimer laser angioplasty

We report our experience in 60 patients using a recently designed 4 French ring catheter system for coronary and a 7 French ring catheter for peripheral percutaneous excimer laser angioplasty. The advantages in comparison to bare fibres comprise an improved flexibility and a central channel for insertion of guide wires to minimize the risk of mechanical vessel wall perforation. The peripheral laser catheter initially transmitted overall energies of 20 mJ pulse^–1 (51 mJ pulse^–1 mm^–2), the coronary device 4.5–5 mJ pulse^–1 (32 mJ pulse^–1 mm^–2). A 50% or more decrease of energy transmission was found in 43% of coronary catheters due to a number of blinded fibres with other fibres remaining intact. This was either due to a retrograde expansion of shock waves generated by the excimer pulse at a calcified lesion, or the result of a deleterious back-reflection of the laser light by contrast media. However, using both laser catheters ablation of plaque in vivo proved to be possible. Small mechanical defects of the catheter tips in 27% did not result in patient related complications. Our initial experience favours further improvement of ring catheters for percutaneous excimer laser angioplasty.     

Smooth excimer laser coronary angioplasty (SELCA) and conventional excimer laser angioplasty: Comparison of vascular injury and smooth muscle cell proliferation

Although the excimer laser, which utilizes ‘non-thermal ablation effects’, has achieved encouraging results in early clinical trials, the long-term results have failed to show any advantage over conventional percutaneous transluminal coronary angioplasty (PTCA). A new system, Smooth Excimer Laser Coronary Angioplasty (SELCA), has been developed to reduce the tissue damage in the vessel wall caused by shock waves and vapour bubbles.SELCA (wavelength 308 nm, pulse duration 115 ns, repetition rate 150 Hz and energy density 50 mJ mm^-2) lowers the amount of shock wave formation and pressure peak amplitude in the surrounding tissue by about eight times when compared to the conventional 308 nm excimer laser (ELCA). In this preclinical evaluation, this new system was compared to ELCA. Fifty New Zealand White rabbits were stimulated by repeated weak DC impulses for a period of 28 days in order to form an atherosclerotic plaque in the right carotid artery. The vessels were excised 3, 7,14 and 28 days after laser irradiation for immunohistochemical analysis. SELCA and ELCA laser treatment lead to a decrease in maximal intimal wall thickness 3 days after intervention (control: 177±4 μm; SELCA: 131±22μm; ELCA: 120 ±33μm). In the period between 3 and 28 days, a moderate increase in intimal wall thickness was observed after SELCA treatment compared to a significant increase after ELCA (28 days after intervention: SELCA: 157±22μm; ELCA: 274 ±28μm). Bromodeoxyuridine (BrdU) was applied 18 and 12 h before excision of the vessels in order to determine the percent of cells undergoing DNA synthesis. The percent of BrdU labelled SMC in the intima (control: 13 ± 2 cells mm_-2) increased in both groups after 3 days (SELCA: 248 ± 107 cells mm^-2; ELCA: 162 ± 41 cells mm^-2) and 7 days (SELCA: 162± 55 cells mm^-2; ELCA: 279 ± 119 cells mm^-2). The present results demonstrate that vascular wall injury and increase in intimal wall thickness following SELCA are reduced in comparison to the results achieved with the conventional technique. Further trials are necessary to assess whether these improvements will lead to more favourable long-term results after excimer laser angioplasty.     

Autofluorescence spectroscopy using a XeCl excimer laser system for simultaneous plaque ablation and fluorescence excitation

Laser–induced fluorescence may be used to guide laser ablation of atherosclerotic lesions. This study was performed to evaluate arterial autofluorescence spectroscopy in vitro using a single XeCl excimer laser (308 nm) for simultaneous tissue ablation and fluorescence excitation. The laser beam was coupled to a 600-μm silica fiber transmitting 40–50 mJ/mm² per pulse. The fluorescence radiation emanating retrogradely from the fiber was collected by a concave mirror for spectroscopic analysis over a range of 321–657 nm. The arterial media (n = 26), lipid plaques (n = 26), and calcified lesions (n = 27) of aortic specimens from ten human cadavers were investigated in air, saline, and blood. Whereas the spectrum of calcified lesions changed with the surrounding optical medium, the other spectra remained constant. In air and blood, the spectra of arterial media, lipid plaques, and calcified lesions could be differentiated qualitatively and quantitatively (P < 0.0001). In saline, there was no clearcut spectroscopic difference between lipid plaques and calcified lesions. However, normal arterial media and atherosclerotic lesions (lipid plaques plus calcified lesions) could still be discriminated. Thus spectroscopy and plaque ablation can be combined using a single XeCl excimer laser. These encouraging results should stimulate further studies to determine the potential use of this approach to guide laser angioplasty in humans. © 1994 Wiley-Liss, Inc.     

Acute response of the arterial wall to pulsed laser irradiation

This study was designed to examine the acute response of normal arterial wall to pulsed laser irradiation. Irradiation with an Excimer or a Holmium YAG laser was performed in 15 normal iliac sites of 8 male New Zealand white rabbits. The excimer laser was operated at 308 nm, 25 Hz, 50 mj/mm²/pulse, and 135 nsec/pulse and the Ho:YAG laser was operated at 2.1 μm, 3.5 Hz, 400 mj/ pulse, 250 μsec/pulse. The excimer and Ho:YAG laser were coupled into a multifiber wire-guided catheter of 1.4 and 1.5 mm diameter, respectively. The mean luminal diameter increased similarly from 2.01 ± 0.29 to 2.46 ± 0.27 mm (P < 0.0005) and from 2.09 ± 0.53 to 2.45 ± 0.30 mm (P < 0.005) after excimer and Ho:YAG laser irradiation, respectively. Perforation occurred in 3 of 15 Ho:YAG irradiated sites and 0 of 15 excimer laser irradiated sites. The sites irradiated with excimer or Ho:YAG laser had similar histologic features, consisting of shedding of the endothelium, disorganization of internal elastic lamina, localized necrosis of vascular smooth muscle cells, and fissures in the medial layer. However, the sites irradiated with excimer laser had lower grading scores than those irradiated with the Ho:YAG laser (P<0.05). Irradiation with excimer or Ho:YAG laser of normal arteries results in: (1) vasodilation of the irradiated artery; (2) localized mechanical vascular injury, and (3) Ho:YAG laser induces more severe damage to the arterial wall than excimer. © 1993 Wiley-Liss, Inc.     

308 nm Excimer laser ablation of cartilage

This article reports the investigation of the XeCl excimer laser as a cutting-ablating tool for human fibrocartilage and hyaline cartilage. Quantitative measurements were made of tissue ablation rates as a function of fluence in meniscal fibrocartilage and articular hyaline cartilage. A force of 1.47 Newtons was applied to an 800-μm fiber with the laser delivering a range of fluences (40-190 mJ/mm²) firing at a frequency of 5 Hz. To assess the effect of repetition rate on depth per pulse, a set of measurements was made at a constant fluence of 60 mJ/mm², with the repetition rate varying from 10 to 40 Hz. Histologic and morphometric analysis of preserved specimens was performed using light microscopy. The results of these studies revealed that the ablation rate was directly proportional to fluence over the range tested. Fibrocartilage was ablated at a rate 2.56 times faster than hyaline cartilage. Repetition rate had no effect on the penetration per pulse. Adjacent tissue damage was noted to be minimal (10–70 μm). The excimer laser achieved ablation rates adequate for arthroscopic applications. © 1994 Wiley-Liss, Inc.     

Initial clinical experience with a modified excimer laser for coronary angioplasty

A clinical study was conducted in 32 patients to evaluate the efficacy and safety of a modified excimer laser system for percutaneous transluminal coronary angioplasty. In this system, the laser beam is scanned and transmitted into eight fibre bundles of the catheter device, consisting of 20 50 μm fibres, each. Twenty-eight patients were treated with 1.5 mm laser catheters, four patients with 1.8 mm laser catheters. Mean time of energy delivery was 82±39 s using a mean energy fluence of 49±2 mJ mm⁻². In all 32 patients in whom laser angioplasty was attempted, laser irradiation resulted in a stenosis reduction from 85±10% (mean±s.d.) before to 57±20% after laser treatment. In 16 patients, additional balloon angioplasty had to be performed, either due to an insufficient angiographic result in 11 patients or due to abrupt vessel closure in five patients. In these 16 patients, percent stenosis decreased after balloon angioplasty to 35±14%, corresponding to a luminal diameter of 1.6±0.5 mm. In 10 patients, dissection was observed. In one of these patients, the dissection resulted in a reduction in antegrade flow, necessitating balloon dilatation. One perforation occurred which did not require surgery. There were no deaths, bypass surgery or myocardial infarction. During the time of follow-up, restenosis occurred in 14 patients; in two of these patients bypass surgery was performed and five patients were treated with conventional balloon angioplasty. These results suggest that this form of modified excimer energy delivery provides effective therapy for patients with coronary artery disease. Due to the small catheter sizes, however, one-half of the patients still required additional balloon dilatation. To increase the number of stand-alone laser procedures and to address the issue of restenosis in this patient population appropriately, larger catheter devices will be necessary.     

In vitro evaluation of ablation parameters of normal and fibrous aorta using smooth excimer laser coronary angioplasty

A modified exeimer laser energy delivery system was used to irradiate 100 segments of normal and fibrous aorta in vitro. The laser beam was scanned into 8 fiber bundles consisting of 50 fibers each resulting in a reduction of the applied pulse energy. The total repetition rate was increased to 150 Hz in order to keep the repetition rate per fiber bundle close to 20 Hz and to minimize thermal injury. The results demonstrate that effective ablation (etch rate per 8 pulses > 2.0 μm) occurred at an energy fluency of 50 mJ/mm² in both normal and fibrous aorta. Tissue damage (carbonization, tissue separation, fissures, cracks, and vacuolization) was in a range of 100 ± 28 to 152 ± 30 μm for normal aorta and in a range of 57 ± 35 to 110 ± 39 μm for fibrous aorta. We conclude that effective ablation of normal and fibrous human aorta can be achieved by the application of smooth excimer laser coronary angioplasty. This improvement of excimer laser technology may result in a reduction of shock wave- and cavitation-induced damage leading to a reduction of tissue injury. However, this awaits further in vitro and in vivo confirmation. © 1993 Wiley-Liss, Inc.     

Patch welding with a pulsed diode laser and indocyanine green

Laser tissue welding is a sutureless method of wound closure that has been used successfully in nerve, skin and arterial anastomoses. An elastin-based biomaterial patch was welded to the intimai surface of porcine aorta in the present study. The aorta was stained with indocyanine green dye to efficiently absorb the 808 nm diode laser light. Laser welding with a pulsed diode laser thermally confines heating to the stained portion of tissue, minimizing adjacent tissue damage. Laser welds of stained aorta to biomaterial were attempted by sandwiching the samples between glass slides and applying pressures ranging from 4 to 20 N cm^-2 for 5 ms pulse durations and 83 mJ mm^-2 radiant exposure. Bleaching of the indocyanine green by as much as 85% was observed after exposure laser irradiation. Finally, successful welds required 5 N cm^-2 of pressure between the elastin biomaterial and aorta.     

Occurrence,extent, and implications of pressure waves during excimer laser ablation of normal arterial wall and atherosclerotic plaque

Ablation of atherosclerotic plaque and normal arterial wall was performed using a Xenon-Chloride Excimer laser with a wavelength of 308 nm and a pulse duration of 115 ns. The light was transmitted via a 600 μm bare fibre and adjusted to an energy density of 3.5J/cm². The acoustic signals generated by the laser pulse were measured with two types of hydrophones consisting of polyvinylidenefluoride with active diameters of 0.3 mm and 0.5 mm and recorded on a dual channel digital storage oscilloscope using either a 0.5 m coaxial cable or a broadband fibre-optic transmission system. Tissue was retrieved from nine cadaver human aortas and macroscopically classified as either normal or calcified atherosclerotic plaque. Histological analysis (Haematoxylin eosin, elastica van Gieson, and immunohistochemical staining) was carried out after the experiments to verify the macroscopic diagnosis and to correlate the acoustic responses with the tissue characteristics. For normal arterial wall, maximum peak pressure was 1.28 MPa ± 0.85 MPa, rise time 163 ns ± 43 ns, and pressure increase 8,2k Pa ± 5,4k Pa/ns. For calcified, atheromatous segments, a maximum peak pressure of 2,02 MPa ± 1,16 MPa, a rise time of 69,9 ns ± 25,8 ns, and a pressure increase of 32,3 kPa ± 21,3 kPa/ns was found. Statistical analysis showed a significant shorter rise time (P < 0.0001) and a higher pressure increase (P < 0.0001) for calcified tissue in comparison to normal arterial wall, whereas maximum pressures alone did not allow a differentiation of tissue characteristics. Several hundred kPa are generated during Excimer laser ablation. The results suggest that focal tissue fragmentation is one mechanism of plaque ablation. A differentiation of tissue characteristics is possible by analysis of rise time and pressure increase, potentially providing the possibility of acoustic ablation control. © 1993 Wiley-Liss, Inc.     

Circulatory and ventilatory effects of hypervolaemia in artificially ventilated piglets

The influence of hypervolaemia upon circulation and pulmonary ventilation was studied in six piglets (body weights 8.5–10.5 kg). A new functional principle for artificial ventilation was used. The alveolar ventilation was unchanged at normovolaemia and hypervolaemia. Arterial blood gases were sampled and end-tidal carbon dioxide concentrations were measured continuously. Central circulation was followed by pressure recordings and an electromagnetic flow meter for cardiac output measurements. Mean values ± SEM of end-inspiratory tracheal pressures increased from 0.98 ± 0.06 kPa at normovolaemia to 1.57 ± 0.06 kPa at hypervolaemia (p < 0.02). In all animals total compliance decreased (p < 0.02). Simultaneously the insufflation time for the tidal volume decreased by 13 percent (p < 0.05). Arterial oxygen tensions decreased from 8.5 ± 0.48 kPa to 7.0± 0.77kPa (p< 0.05). During hypervolaemia aortic pressures increased from 13.1± 1.3kPato 14.9 ± 0.8 kPa(p< 0.05), pulmonary artery pressures from 2.8 ± 0.33 kPa to 5.0 ± 0.53 kPa (p < 0.02) and cardiac output from 1.07 ±0.17 l · min^-1 to 1.5 ± 0.19 l min ·^-1 (p< 0.02). The stroke work for the right heart increased by 74 per cent (p < 0.02) and for the left heart by 62 per cent (p < 0.02). Pulmonary vascular resistance was unchanged, while systemic vascular resistance was significantly decreased (p < 0.05). The positive effect upon systemic circulation gained by the use of excessive fluid therapy resulted in an overcirculation within the lungs which reduced pulmonary ventilation. This reduction could most probably be related to a closure of terminal airways secondary to lung hyperperfusion, increasing the pulmonary shunt.     

Effects of super-pulsed Nd-YAG laser on arterial tissue: comparison with continuous wave

The effects of a super-pulsed Nd-YAG laser at 1.32 μm wavelength on normal or atherosclerotic human arterial tissue were evaluated and compared with those obtained with continuous wave. One joule per pulse was delivered through a 0.2 mm optical fibre with a pulse width of 10 ms at 10 Hz (super-pulse), or 10 W (10 J) were delivered at continuous wave in saline or blood. Ten joules were delivered with super-pulse or continuous wave for each tissue specimen. The aortic specimens were lased either by continuous wave or super-pulse. At super-pulse mode, ablation efficiency (mm³ J⁻¹) was 0.0149±0.0044 for normal tissue in saline, 0.0148±0.0043 for atheroma in saline, 0.0138±0.0062 for normal tissue in blood, and 0.0146±0.0049 for atheroma in blood. There was no significant difference between the groups. At continuous wave mode, ablation efficiency was 0.0507±0.0299 for atheroma in blood (p<0.001 vs super-pulse). However, extensive charring was observed with continuous wave lasing (41% with continuous against 14% with pulsed mode,p<0.001). Heavily calcified plaques were also ablated at 1.5 J per pulse and 15 W (continuous wave), resulting in extensive charring with continuous wave (77% vs 18% with super-pulse,p<0.01). In conclusion, at super-pulse mode, 1.32 μm Nd-YAG laser has neither the selectivity for atheroma nor influence of blood, thermal injury induced by super-pulse is less than that induced by continuous wave (cw), calcified plaques can be ablated by super-pulse, and super-pulsed Nd-YAG laser angioplasty is safer to use than continuous wave.     

Targeted phototherapy using 308 nm Xecl monochromatic excimer laser for psoriasis at difficult to treat sites

Psoriasis is a chronic inflammatory multisystem disease involving skin and joints affecting 1–3 % of the world population. The 308-nm excimer laser has been recently used in the treatment of psoriasis, especially localized psoriasis of scalp and palm and soles. The objective of the study is to evaluate the therapeutic efficacy and safety of a 308-nm excimer laser for the treatment of scalp and palmoplantar psoriasis. A total of 41 adult patients (25 males and 16 females) were enrolled in this study, of which 26 patients had lesions localized to scalp, and 15 patients had involvement of palm and soles. The mean age was 44.5 years (range 18–73). And, the mean duration of psoriasis in our patients was 15 years. They were treated with a 308-nm excimer laser. The initial dose was based on multiples of a predetermined minimal erythema dose, twice weekly for a maximum 12 weeks. Twenty-two of the 23 patients with scalp psoriasis showed improvement, while one patient showed no change; none experienced worsening of symptoms. The mean minimal erythema dose (MED) was found to be 383 mJ/cm² (range 180–650 mJ/cm²). The cumulative dose of irradiation was 1,841 mJ/cm² (range 600–2,500). The percentage improvement from baseline in PSSI score was 78.57 %. Side effects were seen in 20 patients (86.96 %) mainly in the form of erythema. Four patients developed mild relapse at the end of 6 months after the therapy. In 15 patients with palmoplantar psoriasis, the mean MED was found to be 415 mJ/cm² (range 200–950 mJ/cm²). The cumulative dose of irradiation was 28.4–115.5 J?cm² (mean 59.1 J?cm²). The mean number of treatments to achieve clearance (equal to 90 % reduction of PSI score) was 16. Two patients relapsed at the end of 6 months after the therapy. The 308-nm excimer laser is an effective, safe, easy, and relatively quicker method for the treatment of psoriasis at difficult to treat sites, with good results in a somewhat short time.     

Optical properties of human articular tissue as implication for a selective laser application in arthroscopic surgery

Background and Objective: Optical density of normal and pathological hyaline cartilage, meniscus, and synovium is determined using native and laser-irradiated tissue samples in order to examine potentials for a selective laser ablation. Study Design/Materials and Methods: One hundred forty-four autopsy specimens were irradiated in a direct contact mode using a XeCl excimer laser (λ = 308 nm; 20 ns; 40 Hz; 40 ± 2.1 J/mm²; 800 μm fused silica fiber) and a continuous-wave Nd:YAG laser (λ = 1,064 nm; 1 s; 124 ± 5.4 W/mm²; 600 μm fused silica fiber). Transmission spectra were obtained by microspectrophotometry in a spectral range from 250 to 770 nm. Results: In the ultraviolet spectrum analyzed, optical density (OD) is calculated to 0.81 ± 0.05 for native hyaline cartilage, to 1.0 ± 0.07 for meniscal tissue, and to 0.68 ± 0.04 for synovium. With increasing wavelength the OD steadily decreases reaching mean values of 0.06 ± 0.01, 0.13 ± 0.03, and 0.15 ± 0.04 at 750 nm. Compared to normal tissue degeneration of cartilage and meniscus lead to a significant increase in OD with a maximum relative OD of 4.39 and 1.26, respectively (P <.001 and P <.01). In synovitis the OD increases with a maximum ratio of 1.45:1 (P <.01). Following Nd:YAG laser exposition the OD of the coagulated zone exceeded the value of native tissue by a factor of 9.71 for cartilage, 4.71 for meniscus, and 3.04 for synovium (P <.001). Excimer irradiation leads to a 3.38-fold increase in OD for cartilage, 2.23-fold for meniscal tissue, and 1.6-fold for synovium (P <.01). Conclusion: The results presented indicate that a preferential ablation of pathological tissue structures in articular surgery is possible by selecting laser systems with an appropriate spectral emission range. However, thermal laser tissue interaction may lead to severe alterations in optical properties reducing potentials of a preferential or selective laser application. © 1995 Wiley-Liss, Inc.     

Laser synovectomy of the knee joint

The clinical impact of laser-assisted synovectomy was investigated in a two-part study consisting of a morphological part with morphometric measurements and an in vivo part using an animal model. A continuous wave Nd:YAG laser ( = 1064 nm; power density 18–106 W/mm²; exposure 0.5–5 s) and a XeCl excimer laser ( = 308 nm; pulsewidth 20 ns; repetition rate 10–70 Hz; energy density 20–45 mJ/mm²; exposure 10–60 s) were employed in combination with a fused silica fiber with diameters of 600 m and 800 m, respectively. In vitro study. Under light microscopy, synovium exposed to Nd:YAG laser energy presents a transitional band (with a mean diameter of 2 mm) with three zones: a carbonized area, a vesicular zone, and a coagulated part. In contrast, pulsed UV-laser irradiation leads only to a narrow transitional zone extending 10–70 m. Scanning electron microscopy reveals a clear-cut surface following excimer synovectomy, whereas Nd:YAG laser irradiation forms an irregular surface with numerous bursts due to vaporizing activity. In vivo study. Partial synovectomy of the knee joint was performed in two groups of 14 New Zealand white rabbits with a 1064-nm Nd:YAG laser and a 308-nm XeCl excimer laser. Another 14 animals synovectomized in a conventional technique served as a control. Morphological examination and histopathological scoring of the synovial membrane were performed 4 days to 6 months after the operation. The progress of synovial regeneration following excimer laser synovectomy did not differ from observations in the control group. However, Nd:YAG laser irradiation led to a significantly delayed formation of a neosynovium. In addition, Nd:YAG laser application provided an efficient hemostasis. In conclusion, the Nd:YAG laser is a suitable instrument for synovectomy and is superior to conventional techniques, as it provides sufficient hemostasis, an appropriate extent of synovial resection, and delayed formation of a neosynovium, thus interrupting the vicious cycle that may lead to an early recurrence of synovitis.     

Experimental study of application of excimer laser to laser angioplasty

The possible application of excimer laser to laser angioplasty was studied. In the first experiment, the ablative effects of excimer laser at wavelengths of 248 nm and 308 nm on the pig myocardium were examined in vitro at an air-tissue interface. Crater depth increased with total delivered energy and energy per pulse. Very clear cuts could be observed by histological examination. There was no evidence of thermal damage at a wavelength of 248 nm, at 10 pps. Above 10 pps, a thin bordering zone of suspicious thermal damage was noted with the wavelengths of 248 nm and 308 nm. Thermal damage increased with pulse repetition rate. In the second experiment, the effects of excimer laser irradiation on blood were examined. Five vials, each of which contained 3 ml of blood, were exposed to 37.5 mJ laser beam at 10 pps in repetition rate for 10, 20, 30, 40, 50 seconds. One vial was left untreated as a control. No change in hematocrit value was observed after excimer laser irradiation. In contrast, the level of plasma free hemoglobin rose progressively with each increased duration of exposure. This result indicates that the lysis of erythrocytes does not occur in the laser-exposed cells. However, the damage to erythrocyte membrane took place as it was evidenced by progressive hemoglobin leakage into plasma. In the third experiment, the excimer laser was coupled to a 400 microns quartz optical fiber and the laser energy transmitted through the fiber was measured. At a wavelength of 308 nm, pulse energies up to 9 mJ were noted at the tip of the fiber. At a wavelength of 248 nm, the fiber tip was destroyed. In the fourth experiment, acute and chronic healing responses of normal canine arteries to excimer laser irradiation were studied in 4 mongrel dogs. The artery healed completely at the 18th day after the excimer laser irradiation. There was no evidence of thrombus formation and intimal hyperplasia in these arteries. The results suggest the applicability of excimer laser to laser angioplasty.     

A comparison of photosensitizer administration routes for interstitial photodynamic therapy of the liver

Accurate localization of laser light within a tumour lessens the need for selective tumour retention of the photosensitizer. The aim of this study was to investigate different routes of photosensitizer administration for interstitial photodynamic therapy (IPDT) of the liver. Sprague-Dawley rats were photosensitized with HPD 5 mg kg⁻¹ intravascularly at 48 h or by regional administration 60 min prior to light delivery or by interstitial injection (0.04 mg, 0.15 ml) directly into the hepatic parenchyma at 10 and 60 min prior to light delivery. Thirty-two joules of light from a helium-neon (HeNe) laser were delivered interstitially into the median lobe of the liver via a 200-μm optical fibre. Four days after light delivery the liver was harvested, sectioned and stained with haematoxylin and eosin (HE). The maximum cross-sectional area of photodamage was estimated for each photosensitizer administration route in six livers. Both conventional PDT and interstitial routes of administration of the photosensitizer showed comparable areas (±s.e.m.) of bioactivity (8.32±2.03 mm² and 9.5±1.44 mm²) that were greater than those for control livers treated with light only (1.89±0.39 mm²,p<0.01). The maximum area of biological effect was noticed in livers regionally photosensitized by the portal vein or hepatic artery 60 min prior to light delivery (intraportal vein 13.32±1.52 mm² and intrahepatic artery 14.21±4.19 mm²,p<0.01). These results suggest that for IPDT, regional administration of a photosensitizer may achieve the greatest biological effect. This route may be the most appropriate route for interstitial PDT using a selective light delivery system within the liver.     

Arterial compliance in patients on long-treatment-time dialysis

Arterial compliance is found to be reduced in haemodialysis patients. It is not clear whether decreased arterial compliance in uraemic patients is a consequence of long-standing increased mean arterial blood pressure or a consequence of the uraemic state. An adequate blood pressure can be achieved by long-treatment-time dialysis of 8 h three times a week. We studied femoral and carotid artery wall properties in 24 normotensive patients on long-treatment-time dialysis and 4 normal controls matched for mean arterial pressure, age, sex, and body mass index. Arterial distensibility coefficient and compliance coefficient were determined with a vessel wall movement detector system, 24 h after dialysis in the supine position. The patients were 5.9±6.6 years on long-treatment-time dialysis at a Kt/V of 1.8±0.4. We found no significant differences in mean arterial pressure or pulse pressure between patients (85±13, 55±17 mmHg) and controls (84±6, 50±13 mmHg). Femoral distensibility coefficient and compliance coefficient were lower in patients (6.0±2.4 10^-3/kPa; P <0.05, 0.52±0.28 mm²/kPa; n.s.) compared to the controls (8.8±4.0 10^-3/kPa, 0.67±0.38 mm²/kPa). No differences in carotid distensibility coefficient and compliance coefficient were found between patients (12.8±4.6 10^-3/kPa, 0.72±0.30 mm²/kPa) and controls (14.1±4.4 10^-3/kPa, 0.70±0.23 mm²/kPa). We conclude that patients on long-treatment-time-dialysis have an increased stiffening of the muscular femoral artery but not of the more elastic carotid artery. Results suggest that the uraemic state itself has a deleterious effect on the elastic properties of the muscular femoral artery.     

Rate-dependent,nonlinear photoablation of ocular tissue at 308 nm

To quantify the dependence on pulse repetition rate of 308 nm laser ablation in ocular tissue and elucidate the photoablation mechanisms involved, 85 full-thickness ab interno sclerostomies were created in six human donor eyes using an 800-μm-diameter quartz optical fiber. A laser pulse duration of 135 ns, fluence of 31 mJ/mm², and a fixed repetition rate between 5 and 40 Hz were used for 38 sclerostomies; the remaining 47 sclerostomies were completed at various laser settings during initial experimentation. Surprisingly, the numbers of pulses required for complete penetration of the optical fiber through the fixed tissue thickness were not constant as expected but decreased nonlinearly with increasing repetition rate. This demonstrates that the 308 nm excimer laser cuts ocular tissue significantly more rapidly per pulse at higher repetition rates. To explain this nonlinearity, we propose a composite ablation mechanism composed of photochemical, thermal, mechanical, and optical effects in varying proportions. © 1994 Wiley-Liss, Inc.     

Degeneration and recovery of the neuromuscular junction after application of extracorporeal shock wave therapy

It is known that free nerve endings are degenerated after application of shock waves. We therefore hypothesized that the application of shock waves to muscle induces dysfunction of neuromuscular transmission at neuromuscular junctions. We investigated changes in neuromuscular transmission in response to shock wave application. Sprague–Dawley rats were used in this study. Two thousand shock waves at an energy flux density of 0.18 mJ/mm² were applied to their right calf muscles. Neuromuscular junctions of gastrocnemius muscles were evaluated using rhodamine–α‐bungarotoxin on the day of treatment (n = 5). Amplitude and latency of compound muscle action potentials were measured on the day of treatment and 1, 2, 4, 6, and 8 weeks after treatment (n = 10, each group). Degenerated acetylcholine receptors existed in all treated muscles. Although the action potential amplitude on the treated side was significantly less than on the control side from the day of treatment (25.1 ± 7.8 vs. 34.5 ± 9.1, p = 0.012) to 6 weeks (27.9 ± 7.2 vs. 34.5 ± 7.2, p = 0.037), there was no significant difference at 8 weeks. There was no significant difference in transmission latency between the groups. The application of shock waves to muscle induced a transient dysfunction of nerve conduction at neuromuscular junctions. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1660–1665, 2012