NearIR Photon-counting Camera for Diffuse Optical Tomography

DESCRIPTION (provided by applicant): Early detection and routine clinical screening represent the first line of defense for managing cancer, a disease that claimed over 570,280 lives in the U.S. during the year 2005. Significant advances have been made in the medical imaging of tumors; however, many of these techniques are too expensive to be implemented for routine screening. Diffuse optical tomography (DOT) and diffuse correlation tomography (DCT), which images blood flow, promises to provide a method for routine, non-invasive cancer screening that increases the frequency of screening procedures by reducing, or eliminating, the exposure to radiation. Unfortunately, the need for many single photon-counting detector elements, which are expensive and bulky, constrains the development of DCT instruments. The Phase I funding for this project supported the successful development of a new imaging technology that surmounts the limitations of conventional CMOS (complementary-symmetry metal-oxide-semiconductor) APS (Active Pixel Sensor) and CCD (Charge-Coupled Device) imaging technologies and provides the necessary foundation for DCT imaging. In Phase I, we designed, fabricated and tested CMOS avalanche photodiode pixel capable of single optical photon sensitivity, in the near infrared region of the spectrum, with a timing jitter of less than 350 ps. These CMOS Geiger photodiode (GPD) pixels digitize the incident photo-signal, which solves many of the noise issues that have limited the use of CMOS APS camera pixels for high-speed, high- sensitivity, and high spatial-resolution applications, such as DCT. The Phase II goal is to develop a fully integrated, nearIR digital camera chip for DCT imaging of blood flow. This all-digital, CMOS imaging technology fulfills the demanding requirements for providing high signal-to-noise DCT images through the use of many detector elements. In the Phase II effort, we propose to implement the successful pixel designs, identified in Phase I, to construct a prototype chip that will be incorporated into a patch. We will perform DCT imaging of phantoms in the laboratory of our collaborator, Dr. A. Yodh at the University of Pennsylvania. The diagnosis and imaging of breast tissue, as well as sport related injuries, represents the clinical target of the proposed DCT instrument. This effort improves early cancer diagnosis by non-invasively imaging the increased blood flow in breast tumors using red light.