Photodiagnosis (PD), also known as Photodynamic Diagnosis (PDD), is the use of highly sensitive fluorescence drugs to indicate the presence of cancer.
The same drugs that are used for the treatment of cancer (PDT) can be used to assist in its diagnosis.
As in the case of PDT, the drug is first administered to the patient. After a suitable delay, which can be a few hours or a few days depending on the drug, the tumour site is then illuminated with light (usually from a laser).
The colour used for PD is different from that used for PDT. This causes the drug to glow (fluoresce).
In subdued lighting, the fluorescence can be easily seen. This indicates the presence of the drug in the tumour and exact location of the tumour.
The Scottish PDT Centre has diagnosed and treated many patients using the fluorescence from the drug to guide the surgeon during surgery.
Examples include certain types of brain cancer, and tumours located in the urinary tract.
Updated May 2020