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Technologies
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| Photodynamic Therapy (PDT) |
QLT is a world leader in photodynamic therapy (PDT), which works as follows:
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A photosensitizer is injected into the bloodstream, attaching to lipoproteins. |
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Lipoproteins carry the photosensitizer to target cells. |
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Photosensitizer is activated by light, resulting in disruption of biochemical processes in target cells. |
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Target cells are destroyed leaving surrounding cells intact. |
What is Photodynamic Therapy?
PDT uses light-activated drugs called photosensitizers to treat a range of diseases characterized by rapidly growing tissue, including the formation of abnormal blood vessels, such as cancer and age-related macular degeneration (AMD).
A two-step process
Treatment with PDT consists of a two-step process that starts with administration of the drug, or photosensitizer, by intravenous injection. Once the drug enters the bloodstream, it attaches itself to low-density lipoproteins already circulating. As cells undergoing rapid growth require an above-average supply of lipoproteins, the drug reaches these types of cells more quickly and in higher concentrations.
Once the necessary level of concentration is attained, the second step is to activate the drug with a specific dose of light of a particular wavelength. This causes the conversion of normal oxygen found in tissue to a highly energized form called singlet oxygen, which in turn, disrupts normal cellular functions. Neither the drug nor the light exert any effect until combined.
Selectivity
What makes PDT effective and safe is its selectivity. Because the light is shone directly at the cells in the targeted tissue where the drug accumulates preferentially, damage to the surrounding tissue is limited. The entire procedure can be performed in a physician’s office or on an outpatient basis.
Light source
The type of light source used in PDT varies according to the condition treated.
- Ophthalmology: diode laser light is shone through the slit lamp of a microscope into a patient’s eye.
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In all cases only non-thermal (i.e. non-burning) light sources are used. QLT ensures the availability of light sources and delivery systems by collaborating with leading medical device companies to co-develop and promote PDT-dedicated lights and related devices. |
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