Fluorescence time-resolved imaging system embedded in an ultrasound prostate probe

Ultrasound imaging (US) of the prostate has a low specificity to distinguish tumors from the surrounding tissues. This limitation leads to systematic biopsies. Fluorescent diffuse optical imaging may represent an innovative approach to guide biopsies to tumors marked with high specificity contrast agents and therefore enable an early detection of prostate cancer. This article describes a time-resolved optical system embedded in a transrectal US probe, as well as the fluorescence reconstruction method and its performance. Optical measurements were performed using a pulsed laser, optical fibers and a time-resolved detection system. A novel fast reconstruction method was derived and used to locate a 45 µL ICG fluorescent inclusion at a concentration of 10 µM, in a liquid prostate phantom. Very high location accuracy (0.15 cm) was achieved after reconstruction, for different positions of the inclusion, in the three directions of space. The repeatability, tested with ten sequential measurements, was of the same order of magnitude. Influence of the input parameters (optical properties and lifetime) is presented. These results confirm the feasibility of using optical imaging for prostate guided biopsies.