MEDICAL DOSIMETRY AND DOSE DELIVERY FOR PHOTOBIOMODULATION AND PHOTODYNAMIC THERAPY Dennis Sourvanos Joseph P. Fiorellini Timothy C. Zhu The successful application of Photobiomodulation (PBM) and Photodynamic Therapy (PDT) in clinical settings is challenging due to the complex tissue boundaries and intricate 3-dimensional geometries of the targeted anatomical site. There are no known advanced medical dosimetry protocols that incorporate the tissue optical properties of bone, soft tissue, dentin, and enamel. To address this issue of calculating dosage for tissue boundaries of the head and neck region, this thesis aims to investigate dosimetry in the traditional silicone phantom model, a novel 3-dimensional model of the human maxilla, and the mandibular tissues of the porcine cadaver. The medical dosimetry system utilized throughout this thesis incorporates a dual-motor continuous wave transmittance spectroscopy technique to measure tissue optical properties. The system has been successfully used in human clinical PDT treatment and calibrated with a new series of silicone phantom models in both traditional and novel 3-D shapes. The phantom optical properties were extended to include a broader spectrum of human dental-oral craniofacial tissues. Multiple translational preclinical porcine mandible cadaver experiments were conducted to investigate light transmission through complex tissue boundaries at different power outputs and wavelengths. The optical properties of all silicon phantom models and porcine cadavers were validated through dual-catheter, interstitial, and semi-infinite light transmission measurements. Statistical assessments revealed significant variations across all silicon phantom model types, the impact of light transmissions through the optical properties of complex geometries, and that significant variabilities of the 3D shape could lead to inaccuracies when modeling complex anatomical structures. The porcine mandible cadaver system demonstrated that transmission is modified as it passes through boundaries with different optical properties. Significant findings revealed consistencies for soft tissue light transmission irrespective of power, the correlation of light transmission, distance, and different tissues. Significance was determined between the 661nm and 810nm wavelengths and for the semi-infinite light dosimetry protocol to recognize homogenous and mixed tissue groups. The research conducted seeks to enhance medical dosimetry protocols in the head and neck region with eventual translation to human clinical care.