Photodynamic Therapy

Photodynamic Therapy is a special type of phototherapy aimed at treating cancer

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Photodynamic Therapy involves the use of optical radiation in the cure of medical maladies.

Phototherapy is defined as the treatment of medical, psychological, or cosmetic conditions by exposure to light.

Photodynamic Therapy or PDT is a specialized type of phototherapy for the treatment of cancers and, like some phototherapy treatments, uses photosensitizers, but in a different way.

Photosensitizers are chemicals that increase the sensitivity of an organism either locally or systemically to exposure to light.




In generalized phototherapy, the light source produces the desired effect directly with the photosensitizer increasing the efficiency but the treatment can be done with just the light source.

In Photodynamic Therapy the photosensitizer, which is a required component, reacts to exposure from the light source producing a byproduct that itself is highly reactive with the undesirable tissue cells and is the actual treatment.

Careful control of and exposure to the light source is critical for successful treatment

Photodynamic Therapy photosensitizers are specifically designed to be attracted to or absorbed by metabolically fast cells such as cancer cells and may be directly delivered to the treatment site, taken orally, or intravenously.

Once the photosensitizer has been delivered, the site is exposed to a specific spectral band of light causing a series of reactions in the photosensitzer resulting in the formation of singlet oxygen. The singlet oxygen is itself a very aggressive chemical species causing damage to certain biological cells. That damage is confined to areas where the photosensitizer is present and then exposed to the PDT light source.

In this respect, Photodynamic Therapy is a very selective form of treatment since the mobility of the photosensitizer can be varied by delivery method and specific cells can be targeted by the careful design of the photosensitizer compounds. Even if other tissues have attracted or absorbed the photosensitizer and will be effected by the reaction, their unwanted damage is avoided by precise exposure of the desired treatment site to the PDT light source.

Because of the high exposure precision required, lasers are often used due to their focused output and visible light output, which is the predominant portion of the spectrum used in PDT treatments. However, if a wavelength of light is required that is not producible from a laser or when a broader spectral output is needed, other types of light sources can be delivered to the treatment site with pinpoint accuracy via fiber optics.

Photodynamic Therapy light source measurement solutions

Monitoring the amount of exposure to a PDT light source is absolutely critical in preventing unwanted tissue damage to the patient while maintaining the desired efficacy.

International Light Technologies has a selection of Photodynamic Therapy-specific systems designed for highly accurate intensity, exposure, and spectral wavelength measurement of a wide array of PDT light sources in both laboratory and clinical environments.


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Application Common Sources Spectral Range ILT System Options
Click Links Below
Measurement Range Units
PDT (Maladies including cancers) Laser, LEDs, Xenon Lamp,
Halogen Lamp, Laser Diodes
400-1064 nm ILT5000 Laser Power Measurement Options Up to 200 Watts W
    400-1064 nm ILT2400, SED100/F/K15 4e-10 to 8e-3 W
    400-1064 nm ILT1700, SED033/F/HNK15 7.30e-9 to 7.30e+0 W
    400-1064 nm ILT2400, SED033/F/HNK15 2e-7 to 3 W
    400-1064 nm ILT5000, SED033/F/W 7.69e-11 to 1.54e-1 W/cm²
    400-1064 nm ILT1700, SED033/F/W 1.54e-10 to 1.54e-1 W/cm²
    400-1064 nm ILT2400, SED033/F/W 4e-9 to 7e-2 W/cm²
    610-730 nm ILT5000, SED033/TRED/W 5.9e-11 to 1.18e-1 W/cm²
    610-730 nm ILT1700, SED033/TRED/W 1.18e-10 to 1.18e-1 W/cm²
    710-810 nm ILT5000, SED033/TFRD/W 7.7e-11 to 1.5e-1 W/cm²
    710-810 nm ILT1700, SED033/TFRD/W 1.47e-10 to 1.47e-1 W/cm²
* All Radiometers/Photometers/Spectroradiometers are NIST Traceable.
* If units of measure are not shown please contact us (empirical units also available i.e. fc, fL, nits, lm/ft²).