Fiber-optic probe and corresponding optical system to detect, deliver, and analyze fluorescence in target tissue

Background

Photodynamic therapy (PDT) is a promising treatment modality for oncology and antimicrobial applications that relies on the excitation of light-sensitive drugs known as photosensitizers by visible light in order to generate reactive oxygen species. The efficacy of PDT is largely determined by the combination of the absorbed light dose and the photosensitizer concentration. The absorbed light dose is determined by the optical properties, absorption and scattering, of the target tissue. In the case of hollow cavities, this is further complicated by the integrating sphere effect, where light that is diffusely reflected at the boundary re-enters the cavity and can result in influence rates much higher than those predicted purely by geometry or diffusion of light. These optical properties are currently unknown for many applications, precluding prediction of light dose and design of treatment plans for maximally efficacious treatment. Furthermore, photosensitizer uptake is unknown in most cases. In order to perform rigorous and efficacious PDT in hollow cavities, a means for determination of these quantities is required. In order to address these challenges, we propose an optical spectroscopy system that will allow for determination of optical properties at the wall of a hollow cavity and photosensitizer uptake at the time of PDT. This will provide for rigorous treatment planning to maximize efficacy and minimize risk to patients.

Technology Overview

The invention consists of a custom fiber-optic probe and a corresponding optical system to deliver, detect, and analyze diffuse optical reflectance and fluorescence in the target tissue. The probe is used with the optical system to perform diffuse reflectance and fluorescence spectroscopy. The system is controlled by a laptop computer using a custom interface built-in LabVIEW. The entire system is enclosed in a medical-grade cart. The entire assembly is designed to withstand high levels of disinfection with chemical agents such as Cidex OPA.

Prior to PDT treatment, patients receive standard of care medical imaging. These medical images are used to generate a 3D representation of the hollow cavity to be treated in simulation space. The optical properties measured are then assigned to the corresponding regions in the simulation space, and the delivery of light is simulated. These simulation results are performed for a variety of possible treatment configurations, including but not limited to the type of optical fiber, delivered optical power, duration of light delivery, and concentration of scattering emulsion in the hollow cavity. This allows for generation of a patient-specific treatment plan that specifies all relevant treatment parameters, while minimizing the delivered light dose, treatment time, and risk of potential thermal damage to the wall of the hollow cavity.