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  • Articles  (21)
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  • Articles: DFG German National Licenses  (21)
  • Photodynamic therapy  (21)
  • Springer  (21)
  • 1995-1999  (21)
  • Technology  (21)
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  • Articles: DFG German National Licenses  (21)
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  • Springer  (21)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Lasers in medical science 10 (1995), S. 13-18 
    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Larynx ; Oval cavity ; Light dose rates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Photodynamic therapy (PDT) has the potential to treat early carcinomas of the oral cavity and larynx while preserving normal tissue. However, normal tissues retain the photosensitizing agents and may be activated by high light fluence and dose rates resulting in normal tissue necrosis. The effects of varying dose rates of light delivery on various tissues in the upper aerodigestive tract have not been evaluated to date and are necessary to determine a ‘therapeutic light dose range’ that will result in selective tumour necrosis. Thirty adult mongrel dogs received intravenous Photofrin, 2 mg kg−1, 48 h prior to PDT treatment. Photodynamic therapy was administered to the tongue, buccal mucosa and larynx with a microlens fibre and implantable cylindrical diffuser at various dose rates from 20 to 125 J cm−2 at 150 mW cm−2. At the same dose rate of light delivery, the tongue was the most sensitive organ, followed by the buccal mucosa, and last by the larynx. The differential tissue effect of identical dose rates of therapy must be taken into account when administering PDT so that selective tumour necrosis with normal tissue preservation may be achieved. This study indicates the need to perform evaluations of the effect of PDT on other tissue types in an animal model with each new photosensitizer prior to administering PDT to those areas in humans.
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  • 2
    Electronic Resource
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    Lasers in medical science 11 (1996), S. 3-10 
    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Non-tumour ; Arteries ; Fibrocellular intimal hyperplasia ; Aminolaevulinic acid ; Phthalocyanine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Photodynamic therapy is being investigated as a cancer therapy. As a cytotoxic treatment, it may also have therapeutic benefits in certain non-tumour conditions. The mechanism of photodynamic therapy is discussed in relation to its cancer therapy. The literature on non-tumour applications of photodynamic therapy is subsequently reviewed, highlighting its vascular applications in particular. Arterial angioplasty restenosis has proved resistant to all treatments tried thus far. Because fibrocellular intimal hyperplasia arising from the proliferation of vascular medial smooth muscle cells forms the pathological basis of restenosis, photodynamic therapy has been considered in its prevention. The literature on two second-generation photosensitizers (5-aminolaevulinic acid and phthalocyanine) which are likely to achieve clinical application are reviewed with regard to their photodynamic effects on fibrocellular intimal hyperplasia. This review concludes that photodynamic therapy shows enough promise for the inhibition of fibrocellular intimal hyperplasia for large animal studies to be pursued.
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  • 3
    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; 5-Aminolaevulinic acid ; Pancreas ; Bile duct ; Duodenum ; Fluorescence microscopy ; Light dosimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Photodynamic therapy (PDT) using 5-aminolaevulinic-acid-(ALA)-induced protoporphyrin IX (PPIX) increases survival in hamsters with pancreatic cancer. However, experiments with other photosensitizers on this model show a high risk of duodenal perforation. In this paper, the pharmacokinetics and PDT effects of ALA on normal tissues in the pancreatobiliary region are presented. Using quantitative fluorescence microscopy, maximum PPIX fluorescence was seen in the bile ducts, less in the duodenal mucosa and least in the muscularis propria and pancreas. For PDT, light was delivered either using a bare fibre touching the tissue (single-point illumination), or irradiating a 1.5 cm diameter circular area. Single-point PDT (50 J) produced only localized reversible damage without perforation. Surface irradiation of the whole periampullary region (50 J cm−2) caused extensive damage, sometimes with perforation. Before PDT can be used safely to treat tumours of the pancreas and bile duct, further studies are necessary to understand its effect on larger areas of normal tissue.
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  • 4
    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; PDT ; mTHPC ; Early cancer ; Squamous cell carcinoma ; Oesophagus ; Bronchi ; Photosensitizer ; Light dosimetry ; Clinical
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract There have been few studies to date of clinical photodynamic therapy (PDT) with tetra(m-hydroxyphenyl)chlorin (mTHPC). This paper describes the results of the authors' experience with this second-generation photosensitizer, used in the treatment of 40 early cancers of the oesophagus and the bronchi. Surface illumination of the tumour was performed, in most cases, 4 days after intravenous injection of 0.15 mg kg−1 of mTHPC, using 652 nm or 514 nm continuous wave laser light. Endoscopic follow-up with biopsies and brushings was possible for 35 tumours: 27 (77%) showed no recurrence after disease-free follow-ups that ranged from 3 to 38 months. Major complications, all of which were after red light illumination, included one bronchial stenosis, one oesophagotracheal fistula and two probable occult perforations of the oesophagus. Photodynamic therapy with green light renders such perforations of the oesophageal wall essentially impossible at the applied conditions, and appears not to reduce the efficacy of the treatment. Skin photosensitization, which was never observed later than the first week after injection, occurred in 12 patients. Hence, PDT with mTHPC is a safe and effective treatment for early carcinomas of the oesophagus and the tracheobronchial tree.
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  • 5
    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Early stage lung cancer ; Superficial oesophageal cancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract In 1994, the Ministry of Health and Welfare of Japan approved photodynamic therapy (PDT) for the treatment of early stage lung cancer (T0 and T1), superficial oesophageal cancer, superficial early stage gastric cancer and carcinoma in situ and/or dysplasia of the cervix. The decision to do so was based on studies carried out by the PDT Research Group of the Ministry, including PDT treatment of 168 early stage central lung cancers (123 superficial lesions and 45 nodular lesions) and 32 superficial oesophageal cancers. The results presented in this article were analysed according to the extent of the lesion. Of the 123 superficial lung cancers, complete remission (CR) was obtained in 93% of 89 lesions less than 1.0 cm in diameter. Larger lesions responded less well. Complete remission was obtained in 97% of the 33 superficial oesophageal cancers, although three of six patients with lesions over 3.0 cm in diameter later died of metastatic disease. The authors believe PDT to be a suitable and effective treatment for early stage lung and oesophageal cancers.
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  • 6
    ISSN: 1435-604X
    Keywords: Photosensitizer ; Photodynamic therapy ; mTHPC ; Temoporfin ; Pharmacokinetics ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract A Phase I photodynamic therapy (PDT) clinical trial was carried out with Temoporfin (Foscan®, mTHPC) at the Departments of Otolaryngology at Orebro Medical Center (OMC) and Long Island Jewish Medical Center (LIJMC). A range of drug doses, consisting of 0.3, 0.15, 0.075 and 0.0375 mg kg−1, were utilized. Light treatment was performed on the sixth day after injection of the photosensitizer mTHPC. Photodynamic therapy was done on prostate cancer (six cases), bronchial cancer (one case), nasopharyngeal cancer (three cases), laryngeal cancer (eight cases), mesothelioma (one case), laryngeal papilloma (five cases) and basal cell nevus syndrome (one case). A number of patients were treated more than once. Plasma was collected and analysed at 1, 24, 48, 72, 96, 120 and 144 h and at 2 weeks post-injection, to follow the loading and clearance rate of the photosensitizer. Normal and malignant tissues were collected immediately prior to PDT, chemically extracted, and analysed for drug content spectrofluorometrically. Plasma drug levels were proportional to the dose. The half-life of the drug was 45.4 h across the entire dose range. The ratio of the drug in the tumour compared to normal adjacent mucosa was in the range of 2–3. There were no significant adverse effects. These data establish the basis for full clinical trials.
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  • 7
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    Lasers in medical science 11 (1996), S. 237-246 
    ISSN: 1435-604X
    Keywords: Fluorescence ; Time-resolved confocal microscopy ; Porphyrins ; Fluorescence polarization ; Photodynamic therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The application of a novel time-resolved confocal fluorescence microspectrometer to studies of the distribution and speciation of porphyrin photosensitizers in rat C6 cerebral glioma cells is described. The instrument combines a mode-locked argon ion laser excitation source with time-correlated single photon counting fluorescence detection and has sub-micron spatial and sub-nanosecond temporal resolution. The porphyrins studied were haematoporphyrin derivative (HpD), haematoporphyrin IX (HP), porphyrinc (Pc) and the tetrakiscarborane carboxylate ester of 2,4-(α,β-dihydroxyethyl) deuteroporphyrin IX (BOPP). From the heterogeneous emission observed in vitro, assignments and spatial location of various porphyrin species are proposed.
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  • 8
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    Lasers in medical science 10 (1995), S. 19-24 
    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Light dosimetry ; Fibre optic probes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract We describe the calibration of fibre optic probes used to perform in vivo light dosimetry studies during the treatment of skin lesions by photodynamic therapy. Results from six individual detectors show that the linearity of the calibration and the calculated radiant energy fluence rate within a liquid phantom are independent of the type and sensitivity of the probe. The method of calibration is also shown to yield the optical interaction coefficients of the phantom.
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  • 9
    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Haematoporphyrin derivative ; In vivo ; Laser ; Light source ; Murine tumour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The performance of a low cost, table-top/portable light source was tested against an argon ion pumped dye laser for in vivo photodynamic therapy (PDT). The prototype delivers up to 1 W via a 4 mm flexible lightguide within a 30 nm bandwidth centred at any wavelength from 300 nm to 1200 nm at fluence rates of up to 8 W cm−2. An in situ bioassay using regrowth delay of tumour T50/80 was used to quantify the relative efficacy of the prototype with a laser. The tumours were sensitized with haematoporphyrin derivative (HpD) and externally irradiated. There was no significant difference in the response of the tumour to treatment between the two light sources (p = 0.69). Mean growth delays ranged from 2 days (light dose 10 J cm−2) to 20 days (light dose 100 J cm−2). The estimate for the difference in means (laser minus prototype growth delay) was only 0.66 days and was not statistically significant. This in vivo study demonstrates that the prototype is equivalent to a laser in PDT effect. The device has low capital/running cost, is simple to use and is one of the most powerful, spectrally efficient non-laser PDT sources available.
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  • 10
    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Isotropic fibre optic light diffusers ; Construction of diffusers ; Quality assurance of diffusers ; Calibration of diffusers ; Goniometer ; Integrating sphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Spherical isotropic fibre optic light diffusers are used in photodynamic therapy either as a light source or as a light detector. The construction of light diffusers using different materials is described, viz. an optical method involving local polymerization of a dental fissure sealant, which is referred to as the Henderson method, and a second method using plastic or ceramic pre-fabricated spheres. Quality tests necessary for reliable clinical use are presented for the mechanical strength, output power and isotropy. The maximum pull-off force and blow-off output power for the different kinds of diffusers were determined. The calibration procedures are given for measurement of the output power and wavelength of the light emitted by a diffuser and for measurement of the fluence rate by a light-detecting diffuser, using a compact integrating sphere device. With all types of diffusers described, an isotropy can be obtained of better than ± 20% measured over a 320° angle for spheres as small as ≈ 1 mm. Larger ceramic diffusers are particularly suitable for delivering high output powers. A 3-mm-diameter ceramic diffuser mounted on a 600-μm-core fibre can emit up to ≈ 5 W of continuous wave (CW) visible light in air. Diffusers used for light detection can measure the light fluence rate in tissue with ≈15% accuracy or better if calibration factors are determined for each individual probe.
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  • 11
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    Lasers in medical science 11 (1996), S. 139-143 
    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Fluence ; Irradiance ; Light source
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Photodynamic therapy is generally carried out using a laser, usually a dye laser with the wavelength tuned to suit the particular sensitizer. The availability of broad-band sources for use in photodynamic therapy is challenging the role of the laser, since the non-laser sources are more portable and less expensive. Also, the wavelengths utilized may easily be changed by optical filtering. However, the use of a broad-band source introduces serious problems with dosimetry. The concept of the ‘total effective fluence’ takes account of the incident spectral irradiance from the light source, optical transmission through tissue (preferably including backscatter), and absorption by the sensitizer. Application of the concept to various light sources demonstrates the potential value of this simple concept.
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  • 12
    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Diode laser ; mTHPC ; Depth of necrosis ; Normal rat liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Initial pre-clinical evaluation of a new 652 nm diode laser system for photodynamic therapy was performed to establish its efficacy in photo-activating the second-generation photosensitizer meta-tetrahydroxyphenychlorin (mTHPC). The diode laser was compared directly to a copper vapour laser pumped dye laser using depth of necrosis in normal rat liver as a measure of the photodynamic effect. No significant difference between the two lasers was observed.
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  • 13
    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Photofrin ; Oral mucosa ; Normal tissue damage ; Light dosimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Photodynamic therapy (PDT) is a treatment modality with potential application for premalignant lesions and squamous cell carcinoma of the oral mucosa. PDT in principle has dual selectivity. This may result from a ‘preferential’ retention of the photosensitizer in target tissue. In addition, the photodynamic activity will be limited to the irradiated area because PDT will not affect tissues in the absence of excitation light. The specificity of PDT is limited by the fact that normal tissues also retain the photosensitizer to some degree, which makes these tissues susceptible to PDT damage. To optimize PDT for oral malignancies, a study was undertaken on normal tissue to investigate the responses in rat palatal mucosa and surrounding anatomical structures. Eighty male Wistar rats were used in the study. Photofrin was administered i.v. at four doses (0, 2.5, 5 or 10 mg kg−1 body weight). Irradiation for PDT was performed 24 h later. An argon pumped dye laser system was used to produce light of two different treatment wavelengths (514.5 and 625 nm), and various energy density levels (0, 25, 50, 100 or 200 J cm−2). Early effects of PDT were studied at 2 days and late effects at 2 months after treatment. Twenty-four hours after i.v. administration of Photofrin, it was found that PDT affects normal tissues of the oral cavity both macroscopically and microscopically. Combinations of photosensitizer doses ≥5 mg kg−1 and light doses≥100 J cm−2 caused severe and permanent damage to the palatal mucosa and adjacent normal structures such as palatal bone and dentition. Light scattering and internal reflection usually raise the fluence rate in tissue above the irradiance of the incident beam. In an additional study using six male Wistar rats, the energy fluence rate at two treatment wavelengths (514.5 and 625 nm) was measured ex vivo in the palatal mucosa and adjacent anatomical structures. As expected, the energy fluence rates were wavelength, tissue and depth dependent. At the air-mucosa boundary, light of 625 nm was found to have a three-times higher fluence rate than the primary incident beam. Under similar conditions, the fluence rate of 514.5 nm was found to be less, but still twice as high as the primary incident beam. At deeper levels of the rat maxilla, fluence rates were still elevated compared with the incident beam. For 625 nm light, this phenomenon was observed up to the level of the nasal cavity. These increased fluence rates could largely explain the pattern of damage to normal mucosa and surrounding anatomical structures.
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  • 14
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    Lasers in medical science 10 (1995), S. 67-71 
    ISSN: 1435-604X
    Keywords: Oesophageal cancer ; Photodynamic therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract 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.
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  • 15
    ISSN: 1435-604X
    Keywords: 5-Aminolaevulinic acid ; Protoporphyrin IX ; Photodynamic therapy ; Skin neoplasms ; Basal cell carcinoma ; Actinic keratosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Photodynamic therapy (PDT) with topical application of 5-aminolaevulinic acid (ALA, 20% w/w) was used to treat superficial basal cell carcinoma (BCC, 16 patients), Morbus Bowen (one patient), basal cell naevus syndrome (BCNS, three patients), actinic keratosis (AK, two patients), chronic inflammation (CI, one patient), and metastasized BCC (one patient). The interval between ALA application and illumination was 3–6 h. The incident light dose was 50–100 J cm−2, mostly 75 J cm−2, at 633 nm wavelength. This was based on the fluorescence excitation spectrum, measured on the skin of human volunteers. In a few cases, 514.5 nm light was used. A complete response (CR) rate of 79% (median follow-up 13 months) was obtained with 42 BCC lesions. The treatment of five areas with AK, two areas with CI and one area with M. Bowen yielded three CR for AK and five partial remissions (PR). Photodynamic therapy of metastasized BCC, after either topical or oral ALA, was not successful. Treatment of BCNS was satisfactory with 100% CR in one patient (22 lesions), PR in a second patient (20 lesions), and good palliation in a third patient (〉250 lesions). The treatment was well tolerated, although the illumination had to be interrupted occasionally due to pain. Healing usually occurred in 2 weeks. Cosmetic results were good to excellent. 5-Aminolaevulinic acid application over 16–19 h and repeated treatments made it possible to obtain CR of non-superficial lesions. The selective tumour fluorescence was then lost, however, due to fluorescence of normal skin, but the cosmetic outcome did not deteriorate. 5-Aminolaevulinic acid PDT may be a good alternative outpatient treatment, especially in elderly patients and for large treatment areas. The excellent cosmetic outcome warrants further study in younger patients. More work is necessary to establish optimal ALA-treatment schemes.
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  • 16
    ISSN: 1435-604X
    Keywords: Lewis lung carcinoma ; Liposomes ; Photodynamic therapy ; Pulsed laser irradiation ; Zn(II)-phthalocyanine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The effectiveness of a pulsed dye laser (673 nm) for photodynamic therapy (PDT) of tumours in the presence of Zn(II)-phthalocyanine (ZnPc) was evaluated using Lewis lung carcinoma-bearing mice. The tumours were irradiated with different pulse energies (from 0.4 to 10 mJ) at a constant fluence of 0.6 J cm−2 at 24 h after administration of 0.25 mg kg−1 body weight liposome-incorporated ZnPc. Maximal PDT effect, as evaluated by changes in mean tumour diameter, animal survival time and histological evaluation of tumour necrosis, was observed after 3.0 mJ pulse energy irradiation which appears to yield a deeper light penetration and a more efficient sensitizer excitation when compared with lower or higher pulse energies. Electron microscopic analysis of photo-treated tumour indicates preferential damage to malignant tissue as compared to endothelial cells.
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  • 17
    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Non-laser light source ; 5-Aminolaevulinic acid ; Non-melanoma skin cancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The efficacy of a prototype non-laser light source for photodynamic therapy was assessed in clinical practice in the treatment of Bowen's disease and actinic keratoses. The light source, incorporating a 300 W short arc plasma discharge, was adjusted by appropriate filters to produce a bandwidth of 630±15 nm. Topical 5-aminolaevulinic acid was applied 4 h before irradiation to permit production within the lesion of the active photosensitizer, protoporphyrin IX. Individual lesions received 94–156 J cm−2. Twenty lesions of Bowen's disease and four actinic keratoses were treated in 12 patients. Patients were reviewed at monthly intervals and treatment repeated if residual disease was present. Clearance was achieved with a single treatment in 15 lesions and in all of the remaining nine lesions after a second treatment. The treatment was well tolerated, with pain absent or mild during treatment in 22 lesions, with only one lesion requiring local anaesthesia. Over the 10 days following treatment, no pain was associated with 21 treated lesions. During a 12 month follow-up period, two Bowen's disease lesions recurred. The overall complete response rate was 92%. Scarring was evident following PDT in only three lesions. Photodynamic therapy using this portable non-laser light source appears to be an effective and well-tolerated treatment for Bowen's disease and actinic keratoses.
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  • 18
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    Lasers in medical science 11 (1996), S. 23-29 
    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Head and neck cancer ; Chlorin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Over the past 30 months, the authors have treated a wide variety of head and neck cancer patients with meta-tetrahydroxyphenylchlorin (mTHPC)-mediated photodynamic therapy (PDT). This drug is a powerful, second-generation photosensitizer with significant advantages over earlier drugs. Treatment ranged from palliation and adjunctive to curative procedures. Results to date are very encouraging, with marked advantages over standard methods of treatment with respect to morbidity, both functional and aesthetic. Potential cure rates remain essentially unchanged, very much dependent on the stage of the tumour. These promising early results justify a multicentre study for treatment of early head and neck cancer using this drug and light combination. This is now underway.
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  • 19
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    Lasers in medical science 11 (1996), S. 155-161 
    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Interstitial ; Dunning R3327 prostate tumour ; Threshold light dose ; Cylindrical diffuser ; Diffusion theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Interstitial photodynamic therapy (PDT) could be an alternative radical treatment for prostate cancer. The ability to predict the depth of necrosis is necessary for light treatment planning using multiple optical fibres. The extent of PDT necrosis was studied in subcutaneously implanted R3327-AT6 Dunning prostate tumours which had similar optical characteristics to human prostate. Tumour-bearing subjects were given 20 mg kg−1 Haematoporphyrin esters (HPE) and irradiated 24 h later with 630 nm laser light. Five subjects per group were treated with increasing light doses (50–450 J cm−1) delivered interstitially via a single 2 cm long cylindrical diffuser. After 450 J cm−1 of irradiation, 4.3±0.8 cm3 [standard error of the mean (s.e.m.)] of tumour tissue was necrosed to a depth of 10.5±0.8 mm around the diffuser. There was an approximately linear correlation between the volume of PDT necrosis around the fibre and prescribed light dose. The mean threshold light dose for PDT effect was 18±2 J cm−2. In this tumour with a mean photosensitizer concentration of 16±1.5μg g−1, low light doses produced tumour necrosis. PDT using multiple diffusers could destroy a relatively large tumour volume and the ‘diffusion theory’ model reliably predicted the depth of necrosis.
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  • 20
    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Early stage carcinoma ; Bronchi ; mTHPC ; Light dosimetry ; Fluorescence ; Spectroscopy ; Photosensitizer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Under identical conditions (drug and light dose, timing), the results of photodynamic therapy (PDT) of carcinomas of the bronchi with tetra(meta-hydroxyphenyl)chlorin (mTHPC) show large variations between patients. Before patients underwent PDT treatment, the mTHPC level was measured in the lesion, the normal surrounding tissue and the oral cavity, with an apparatus based on fluorescence spectroscopy. The fluctuations in degree of tissue reaction and tumour destruction between patients could be explained by individual variations in the mTHPC level in the mucosa of the bronchi. The patients who showed the highest mTHPC fluorescence signal also had the strongest response to PDT. In addition, a correlation between the mTHPC level in the oral cavity and bronchial mucosa was found. It is concluded that PDT can be improved by measuring the mTHPC level in the bronchi or the oral cavity before treatment by fluorescence spectroscopy, and then by adjusting the light dose to be applied to the observed mTHPC level.
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  • 21
    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Dosimetry ; 5-Aminolaevulinic acid ; Protoporphyrin IX ; Photobleaching ; Topical application
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Photodynamic therapy (PDT) based on topical application of photosensitizers is currently in clinical use for the treatment of basal cell carcinoma of the skin, and it has been evaluated in animal models for photo-ablation of the endometrium. This paper presents a dosimetry model which indicates that a limiting factor in treating thick tumours will be the transport of the drug into the tumour rather than depletion of the optical distribution. The model predicts that an optical irradiation of 100 mW cm−2 at 635 nm for 20 min, ie well below the threshold for hyperthermic reaction, will give an adequate light dose to a depth of 3 mm. The time required for photosensitizers to diffuse to this depth is in the range of 3–15 h, dependent on the diffusion properties of the tissue.
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