Fast and accurate biophotonic simulations for photodynamic cancer therapy treatment planning

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Photodynamic Cancer Therapy (PDT) treats cancer by using a compound that, when activated by light, destroys cells. By limiting where tissue is exposed to light, one can destroy cancerous cells with a procedure that is less invasive than surgery, but with fewer side-effects than traditional chemotherapy or ionizing radiation therapy. This improves patient recovery times and greatly reduces cost compared to these therapies. While PDT is now widely used to treat skin cancers, where it is easy to control which tissue is exposed to light, it has been less used for interstitial cancers within the body. These cancers can be treated with PDT by administering the photosensitizer compound intraveneously, and activating the photosensitizer only near the tumour by light administered with fiber optic "light needles." However, determining where these light probes should be placed is difficult and it is not yet possible to determine in advance of treatment what the resulting light distribution and hence tissue destruction will be; this greatly limits PDT's usefulness for these more complex cancers.In this project we are developing a PDT "treatment planning" system which will both predict the light distribution that will result from a given probe placement, and automatically suggest an optimized probe placement that will yield the best treatment result. Given MRI data that describes both where the tumour is and the boundaries between the various tissues in a patient's body, this system will rapidly but very accurately simulate where light would go, given a set of light probes. This computation is normally very time-consuming, but we will use special computer chips called Field Programmable Gate Arrrays to accelerate the computation, making our computations approximately 60x more efficient. With such a fast computation, we can automatically determine the light distribution for many different possible probe locations, and return a suggested set of optimized probe locations to a clinician, along with the expected result on the tumour and surrounding tissue. Taken together, this system can make PDT therapy effective for complex cancers, making a promising new cancer therapy applicable to many more patients and improving their lives.