Copper Vapor Pumped Dye Laser Research Articles

Fluorescence biodistribution and photosensitising activity of toluidine blue o on rat buccal mucosa.

The antimicrobial activity of toluidine blue O (TBO) in the presence of red light has been demonstrated for a wide range of microorganisms. The response of tissues to TBO-induced photosensitisation is an important factor in assessing the clinical usefulness of this technique for the treatment of infectious diseases. The aims of this study were to determine the effect of TBO-mediated photosensitisation on rat buccal mucosa and the biodistribution of the photosensitiser in this tissue. An aqueous solution of TBO was applied to one side of the buccal mucosa of the animals. A 6 mm diameter area was then exposed to light (633 nm) from a copper vapour pumped-dye laser. The opposite, untreated, side of the buccal mucosa served as a control. TBO concentrations of 25, 50 and 200 microg/ml, laser light doses of 110, 170 and 340 J/cm(2) were assessed. Control groups of animals were subjected to 340 J/cm(2) laser light alone or to 200 microg/ml TBO alone. Serial sacrifices were performed after 72 h to obtain mucosal tissue samples for histological examination. For the determination of TBO biodistribution, additional groups received the same TBO doses and were sacrificed after 1 min or 10 min. Specimens were removed and frozen immediately for digital fluorescence imaging. No necrotic or inflammatory changes were found in the buccal mucosa of the animals with any of the treatments (using up to 200 microg/ml TBO and 340 J/cm(2) laser light). A high TBO fluorescence in the epithelium, particularly in the keratinised layer, with almost no fluorescence in the underlying connective tissue was demonstrated by the digital imaging. The results of this study suggest that TBO-mediated PDT (within the concentrations and light doses tested) could be a safe antimicrobial approach for the oral infections without damaging the adjacent normal tissue.

Ex-vivo treatment of gastric Helicobacter infection by photodynamic therapy

Attempts to develop PDT for eradication of Helicobacter infection have only been successful in vitro. We have investigated the effect of topical sensitization (except ALA) of Helicobacter mustelae on explanted ferret gastric mucosa using one of five sensitizers (methylene blue (MB), toluidine blue O (TBO), phthalocyanine, haematoporphyrin derivative and 5-aminolavulinic acid), followed by irradiation with an appropriately tuned copper vapour pumped dye laser. A 90% reduction in counts of bacteria sensitized with 0.75 mg TBO kg −1 were seen after irradiation with 200 J cm −2. Concentrations of MB of 0.75 mg kg −1 and 7.5 mg kg −1 were not toxic to H. mustelae, but the further addition of 20 J cm −2 laser light reduced colony counts by more than 99%. MB at a concentration of 75 mg kg −1 exhibited significant dark toxicity towards H. mustelae, but further addition of 20 J cm −2 laser light resulted in near eradication of all colonies. The remaining three compounds were ineffective. Finally, we studied the microscopic fluorescence distribution of MB (7.5 mg kg −1) on ferret gastric mucosa after topical administration. Fluorescence was greatest in the superficial mucosal layer, upon which lies the bacteria. However, from experiments on rats, the energy required to kill the sensitized bacteria was insufficient to damage the underlying mucosa. We conclude that Helicobacter can be killed on host mucosal epithelium following topical administration of MB and subsequent exposure to laser light.

Photodynamic therapy of oesophageal cancer

Twenty-three patients, 12 males and 11 females aged 42–86 years (mean age 69.6), with inoperable oesophageal cancer were treated by endoscopic photodynamic therapy. Inoperability in 20 patients was due to extent of tumour and existence of metastases, in two because of poor general condition and in one patient due to recurrence at the site of previous anastomosis. Prior to treatment, patients' degree of dysphagia and their functional status were recorded. Using barium contrast studies and endoscopy, the extent and location of the tumour within the lumen of the oesophagus were mapped out. Treatment protocol consisted of intravenous administration of the photosensitizer, Polyhaematoporphyrin, followed 24–48 h later by illumination of the tumour with 630 nm light produced by a copper vapour pumped-dye laser and delivered via a 400μm internal diameter optical fibre with a cylindrical diffusing end. All treatments were undertaken under general anaesthesia as day case procedures. There was no treatment-related mortality nor was there any complication apart from a mild skin photosensitivity reaction in one case. Every patient's swallowing and functional status was improved at 6 weeks post-treatment. Ten patients needed more than one treatment: five required oesophageal dilatation. Thirteen patients survived a mean period of 6.2 months. Two needed oesophageal intubation 3–4 weeks before their death. Ten patients are alive at 6–14 months. This study suggests photodynamic therapy in inoperable oesophageal cancer to be a useful treatment method and in suitable cases an alternative to other forms of palliation. Its value lies in the fact that it can be used to treat cancer at any level of the oesophagus irrespective of histology.

Multiple fibre interstitial photodynamic therapy of patients with colorectal liver metastases

Multiple fibre interstitial photodynamic therapy (IPDT) was performed in patients with colorectal hepatic metastases (CRHM) to determine treatment response and side-effects. Ten patients aged 48–75 years with 16 CRHM (seven solitary) were sensitized with (111 mg m−2) haematoporphyrin derivative intravenously. Forty-eight hours later a custom-designed light delivery system guided by ultrasound allowed 630 nm light from a copper vapour pumped-dye laser split into four 200 μm optical fibres to be geometrically positioned within the metastasis. This was performed percutaneously in four patients and at laparotomy in six. Metastases were imaged using computerized tomography and volumes measured by planimetry. Growth was expressed as a ratio relative to the initial volume (RVG). Following IPDT no complications occurred. Three metastases were not treated because of technical problems. No patient suffered skin photosensitivity reactions. Twelve weeks following IPDT, 12 metastases of less than 60 cc initial volume had a mean RVG of 0.99 (s.d. 0.27). One large solitary metastasis continued to grow after IPDT with a RVG of 1.9 after 12 weeks. Untreated hepatic metastases had a mean RVG of 2.13 after 12 weeks. These data suggest that IPDT can reduce the growth of small hepatic metastases and can be performed with low morbidity when applied at laparotomy and with minimally invasive techniques.

The Morphological and Functional Changes in Rat Bladder Following Photodynamic Therapy with Phthalocyanine Photosensitization

We have studied photodynamic therapy (PDT) in the rat bladder with a new photosensitizer, aluminium sulfonated phthalocyanine (AlSPc) given intravenously and intravesically. The microscopic distribution of photosensitizer fluorescence in the bladder wall was studied by laser fluorescence microscopy. Prior to PDT the bladder capacity and compliance were assessed by filling cystometry. Intravesical red light (675nm.) from a copper vapour pumped dye laser was used to activate the photosensitizer using light doses of 20 to 200J/cm.2 Urodynamic and histologic changes were studied at intervals for up to three months.The fluorescence studies showed that AlSPc was eliminated from the deeper muscle layers more quickly than from the superficial layers of the bladder wall so that by 24hours there was four times as much fluorescence from the mucosa and lamina propria compared to the deeper muscle. Control bladders illuminated with laser light alone showed no effects at these light doses. Animals treated 24hours after sensitization showed a reduction in bladder capacity of up to 78% (20J/cm.2 light and 1.5mg./kg. AlSPc). An initial reduction in compliance recovered in two weeks after low doses (0.5mg./kg.) of AlSPc but was still abnormal at three months after higher doses (1.5mg./kg.); though there was no long term histologic abnormality seen.Aluminium sulfonated phthalocyanine is a promising photosensitizer for bladder photodynamic therapy and using low doses of the drug it is possible to produce a superficial necrosis without muscle damage across a range of light doses. This heals by epithelial regeneration with no long term functional impairment. Direct absorption of this photosensitizer following intravesical administration seems unreliable.

Release Studies of Atomic Technetium

AbstractApplication of a laser ion source (LIS) is a promising new technique for trace analysis with high efficiency and selectivity. One of the problems which can limit its efficiency attained in practice is the adsorption of sample atoms on the hot walls of the LIS cavity. We have studied the release of atomic technetium from different wall materials at temperatures up to 2500 K. For these investigations resonance ionization of technetium atoms applying a copper vapour pumped dye laser system and γ‐spectrometry of 6‐h 99mTc have been used. Theoretical calculations of the heat of desorption for technetium on different wall materials are presented and compared with experimental data. Though the results reported concern technetium, most of the considerations are quite general for a laser ion source.

Atomic fluorescence in a pulsed hollow cathode discharge with a copper vapor pumped dye laser

Application of a pulsed glow discharge as an atomizer for atomic fluorescence spectroscopy with a copper vapor laser pumped dye laser excitation source was investigated. The discharge system was synchronously pulsed with the laser to provide a low noise background and the low pressure, inert gas atmosphere contributed to an almost ideal environment for fluorescence measurement. The high repetition rate of the copper vapor laser (6000 Hz) improved the detection efficiency over lower repetition rate laser systems. Disposable graphite cup electrodes were used as demountable hollow cathodes for measurement of aqueous samples. The samples were injected into the cathode cups and dried using a programmable electrothermal device for reproducibility. The discharge chamber was a commercially available vacuum chamber adapted for both flowing and static gas environments. Operational parameters, such as chamber pressure, discharge voltage, sample volume, and cathode cup diameter were evaluated for maximum fluorescence signal. The maximum signals were observed at discharge voltages of 480 V for solid samples and above 1000 V for aqueous samples. The chamber pressure (2–14 Torr) was not critical. Sample sizes of over 40 μl gave no signal increase. Maximum fluorescence signals were obtained 10–15 s (60 000–90 000 shots) following the initiation of laser-discharge pulsing. Linear calibration curves were obtained for lead and iridium with limits of detection of 15 fg and 2 pg, respectively. Although the signal was higher in a static gas environment, the signal to noise ratio was lower than in a flowing gas system.

Muscle Damage and Recovery in the Rabbit Tongue Following Photodynamic Therapy with Haematoporphyrin Derivative

To study the effects of photodynamic therapy on the tissues of the tongue, 20 New Zealand White rabbits were injected intravenously with haematoporphyrin derivative. Their tongues and those of 2 controls were illuminated with 100 J/cm2 of red light from a copper vapour-pumped dye laser emitting light at 625 nm. The rabbits were sacrificed at intervals between 2 days and 12 weeks following treatment. Their tongues were examined histologically. Initially there was marked damage to mucosa, muscle and blood vessels. However, this healed by a mixture of regeneration and scarring.

THE PHOTOKILLING OF BLADDER CARCINOMA CELLS in vitro BY PHENOTHIAZINE DYES

The potential photodynamic therapy photosensitizers Methylene Blue, Azure C, Methylene Violet, Thionine, Methylene Green, Haematoporphyrin, Nile Blue A, chloroaluminium phthalocyanine and bis-aluminium phthalocyanine were examined for their photoeffects and dark toxicity against a human superficial bladder carcinoma cell-line. By examination of [3H]thymidine uptake into dye-treated cells after irradiation with a copper-vapour pumped dye laser, it was found that Methylene Blue was the most phototoxic and dark toxic of all the dyes tested, suggesting that the dye might be of some use as a topically applied photodrug for use in photodynamic therapy of superficial or early-recurring carcinomas.

Measurement Methods for Atomic Fluorescence and Laser-Enhanced Ionization Spectrometries with a Copper-Vapor Pumped Dye Laser

Several correction methods for several types of spectral and electrical interferences with a copper-vapor pumped dye laser system are presented. A tunable pulsed dye laser pumped with a copper vapor laser was used to excite the atomic fluorescence of Li, Na, In, and Fe and the atomic ionization of Li, In, and Fe. Correction methods used involved either modulation of the pulsed laser output and subsequent subtraction of noise or electrical bandwidth limitation of the signals to enhance the signal to high-frequency laser noise ratio. These methods are shown to provide a significant reduction in high-frequency interference, a major noise source with this type of pump laser. These three correction methods are shown to provide a significant improvement in the detection power of both laser-enhanced ionization and fluorescence methods. Limits of detection are presented for each correction method.

Axial mode structure of a copper vapor pumped dye laser

A search for lasers to be employed in the development of uranium isotope separation techniques led to the investigation of a copper vapor pumped tunable dye laser patterned after the concept developed by Hansch. This investigation revealed that although the time integrated spectral output covered approximately 1.3 GHz, which was the desired bandwidth, the time resolved spectral output included high visibility mode structure which fluctuated randomly from pulse to pulse. These fluctuations could significantly reduce the throughput efficiency of multiphoton photoionization isotope separation processes involving strongly inhomogeneously broadened transitions.