An interstitial diffuse optical tomography (iDOT) system with multiple light diffusers and isotropic detectors has been developed to characterize the optical properties of prostate gland during photodynamic therapy (PDT). During the data acquisition, linear or point sources and detectors are inserted into the prostate gland, sequentially, and controlled by a motorized system. For our continuous-wave (CW) iDOT system, CW measurements of optical signal are made, and the spatial distributions of light fluence rate can be described by the CW diffusion equation. Optical properties (absorption and reduced scattering coefficients) of the prostate gland are reconstructed by solving the inverse problem with the use of an adjoint model based on the CW diffusion equation. To exam our methodology, two and three dimensional mathematical prostate phantoms including anomalies with known optical properties is prepared and we compare the absorption and reduced scattering images reconstructed for the phantom with the known results. In the end, we discuss the issue of reconstruction of optical properties using human patient data.