Abstract
Progress in photodynamic therapy (PDT) depends on the development of: (1) photosensitizers,
(2) optical devices among which are lasers and light delivery systems, and (3) clinical
procedure. The light delivery systems which are the focus of this article are fiberoptic
devices developed in Lausanne, Switzerland* for use in the endoscopic treatment of
cancer or precancerous lesions in the bronchi, the esophagus, the uterus, the cervix,
the upper aerodigestive tract and thoracic cavity. Light delivery systems for both
surface and interstitial application are presented, together with some of the physical
principles on which they are based. Incorporation in these devices of the possibility
for in-situ measurement of reflected therapeutic light and/or fluorescence emitted
by endogenous and/or exogenous dyes allows for improved light and drug dosimetry,
as well as the measurement of photobleaching, local oxygenation and other tissue properties.
The necessity of information on tissue optical parameters, as well as the use of simple
mathematical models and tissue phantoms, for optimizing light distributing devices
is underlined.
The devices are optimized for delivering the desired light intensity distribution
to the targeted region with minimal losses. In some cases this implies using the device
to modify the shape of the hollow organ during PDT, an example of which is given for
the case of the esophagus. In another strategy, one adapts the shape of the device
to that of the organ, using an elastic balloon catheter. Here examples are given for
the uterus, the bronchi and the thoracic cavity. The mechanical properties, the sizes,
shapes and materials of the light delivery systems must be optimized for safe use
while retaining low cost. Furthermore, the devices must whenever possible be rendered
compatible with existing medical technology.
A significant improvement in clinical efficacy has been demonstrated in the testing
of some of these new fiberoptic light delivery systems.
For endoscopic PDT in the hollow organs, the design and optimalization of multiple
new approaches to light distribution will continue to lead to improved clinical results.
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* The devices discussed in this article have been developed at the Federal Institute
of Technology and/or by Medlight SA in Lausanne, Switzerland.
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