Medical imaging lasers: Fluorescence molecular tomography
Abstract
Quite possibly the most deciding factor in deciding treatment methods and subsequent patient
outcomes in regards to cancer is the ability to have early and sensitive detection. Fluorescence
molecular tomography (FMT) is such a method of detection. In FMT, a near infrared light laser is
modulated at a radio frequency to generate a diffused photon density wave that provides a
measure of how much phase difference there is between the incident laser light and the
detected laser light due to the structure of a tissue sample. As it is more accurate to measure
this phase difference at a lower frequency, we use a low frequency sinusoidal signal carried by
a radio frequency to modulate the laser source. Phase measurement is then accomplished by
measuring how much each peak has shifted due to the tissue compared to the incident
sinusoidal signal. 3D images of tumors and other tissue abnormalities can then be constructed
from this data, and FMT can be integrated with other more conventional imaging techniques
such as magnetic resonance imaging (MRI). The advantages of this technique include improved
precision, cost effectiveness and no patient risk. Construction of a single light source FMT
system has been completed. Initial study shows a constant drift associated with the system
which must be calibrated each day. The effect of a change in intensity of the laser on system
drift is currently under study.