Light delivery and light dosimetry for photodynamic therapy

Abstract Photodynamic therapy (PDT) has attracted attention because it was considered to be a selective form of cancer treatment causing minimal damage to normal tissues. This is not exactly true, because the ratio between the photosensitizer concentrations in tumour and surrounding normal tissues is not always much more than one. Nevertheless, tumour destruction by PDT with relatively little damage to normal tissue is possible in many cases. This requires sophisticated light delivery and/or light dosimetry techniques. In this respect the limited penetration of light into biological tissues can sometimes be useful. In this paper a qualitative and sometimes quantitative discussion is given of the physical phenomena determining the energy fluence in a biological tissue. Most important is light scattering, the contribution of which depends on the geometrical conditions. Finite beam surface irradiation, irradiation of hollow organs (bladder) and interstitial irradiation are discussed separately. The emphasis is on light ‘dose’ and light dose distribution. It is emphasized that PDT dosimetry in general is complicated by photosensitizer distribution (which is usually not known), by photobleaching of the sensitizer, by possible effects of hyperthermia, and by changes in optical properties during and as a result of PDT

Photodynamic therapy: A promising new modality for the treatment of cancer

The first reports on photodynamic therapy (PDT) date back to the 1970s. Since then, several thousands of patients, both with early stage and advanced stage solid tumours, have been treated with PDT and many claims have been made regarding its efficacy. Nevertheless, the therapy has not yet found general acceptance by oncologists. Therefore it seems legitimate to ask whether PDT can still be described as "a promising new therapy in the treatment of cancer". Clinically, PDT has been mainly used for bladder cancer, lung cancer and in malignant diseases of the skin and upper aerodigestive tract. The sensitizer used in the photodynamic treatment of most patients is Photofrin, (Photofrin, the commercial name of dihematoporphyrin ether/ester, containing > 80% of the active porphyrin dimers/oligomers (A.M.R. Fisher, A.L. Murphee and C.J. Gomer, Clinical and preclinical photodynamictherapy, Review Series Article, Lasers Surg. Med., 17 (1995) 2-31). It is a complex mixture of porphyrins derived from hematoporphyrin. Although this sensitizer is effective, it is not the most suitable photosensitizer for PDT. Prolonged skin photosensitivity and the relatively low absorbance at 630 nm, a wavelength where tissue penetration of light is not optimal, have been frequently cited as negative aspects hindering general acceptance. A multitude of new sensitizers is currently under evaluation. Most of these "second generation photosensitizers" are chemically pure, absorb light at around 650 nm or greater and induce no or less general skin photosensitivity. Another novel approach is the photosensitization of neoplasms by the induction of endogenous photosensitizers through the application of 5-aminolevulinic acid (ALA). This article addresses the use of PDT in the disciplines mentioned above and attempts to indicate developments of PDT which could be necessary for this therapy to gain a wider acceptance in the various field

Point View in Bird and Flower Painting

在中国传统绘画中，点景是极其重要的一种表达方式。石涛所研究的绘画问题中，情感、理性、力量都是不可缺少的，如何恰当地运用这三者，却有可能导致完全不同的创作结果。而点景正是这三者的集合点，不仅要用心灵去感受自然对象的内在精神，不能因为对象的限制而使感受层次也受到限制，把眼睛之受升华为心理之受。在绘画作品中合理地运用点景能使画家的情感与物象更加融合，画家自身的主观感受在画面上得到充分的体现，以一种小的特殊表现符号流露出画家作品里表达的象征倾向和审美概念，对画面的构图及意境有着画龙点睛的作用。本文以花鸟画点景为研究对象，重点介绍了点景的表现与意义；进一步阐述了点景在传统花鸟画构成中的作用，着重论述其在...The “point view” is extremely important as a means of expression in the traditional Chinese painting. Emotion, rationality and power are essential in the Shi Tao studied painting, and how to properly use them may lead to the creation of a completely different result. For the reason that “point view” is a collection of these three points, shouldn’t we only use the soul to feel the inner spirit of n...学位：文学硕士院系专业：艺术教育学院美术系_美术学学号：1862007115166

Short- and long-term normal tissue damage with photodynamic therpay in pig trachea: a fluence-response pilot study comparing Phtofrin and mTHPC.

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Photodynamic effectiveness and vasoconstriction in hairless mouse skin after topical 5-aminoleculinic acid and single- or two-fold illumination.

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PpIX fluorescence kinetics and increased skin damage after intracutaneous injection of 5-aminolevulinic acid and repeated illumination

Photodynamic therapy with topically applied 5-aminolevulinic acid is used successfully for superficial skin lesions. The results for thicker, nodular lesions are less favorable. The method of aminolevulinic acid administration, the concentrations of aminolevulinic acid, and the irradiation schemes used so far have not been investigated thoroughly. As aminolevulinic acid photodynamic therapy has high potential for the increasing problem of skin cancer, we investigated both visually and histopathologically the photodynamic-therapy-induced skin damage after intracutaneous administration of aminolevulinic acid in normal porcine skin. We also investigated the kinetics of the aminolevulinic-acid-induced photosensitizer protoporphyrin IX fluorescence after irradiation in relation to fluence and irradiance. Finally we investigated the effect on photodynamic-therapy-induced damage of a fractionated irradiation. This study demonstrates that intracutaneous administration of aminolevulinic acid leads to higher fluorescence levels and thus to formation of higher protoporphyrin IX concentrations than topical application of aminolevulinic acid cream. The peak level of protoporphyrin IX after intracutaneous administration of aminolevulinic acid is reached earlier than after topical administration. The comeback of fluorescence, indicating re-synthesis of protoporphyrin IX after irradiation, is inhibited with increasing fluence. Photodynamic-therapy-induced damage increases with increasing fluence, but is independent of the irradiance. Finally, the photodynamic-therapy-induced skin damage seems to be greater after fractionated irradiations with two equal light fractions of 15 J per cm2 separated by a dark interval of 2 h