Development and Testing of a Second Generation Hand-held Optical Imager

Abstract

Professor Anuradha Godavarty, Major ProfessorHand-held optical imagers are developed towards clinical breast cancer imaging. Herein, a Gen-2 hand-held optical imager has been developed with unique features: (i) image curved breast tissues with ~86% surface contact, and (ii) perform reflectance and transillumination imaging using the novel forked probe heads. Extensive phantom studies were performed using 1% Liposyn solution (background, ~ 300 ml and 1000 ml volumes) and 0.45 cc India Ink (absorption) targets, under different target:background contrast ratios and target depths. Twodimensional surface images detected target(s) up to 2.5 cm deep via reflectance imaging, and up to 5 cm deep via transillumination imaging. Preliminary studies on gel-based breast phantoms (~700 ml) detected targets via reflectance and transillumination imaging. Preliminary in-vivo reflectance studies on normal and cancerous breast tissues also detected targets, although with artifacts. In future, the portable Gen-2 imager has potential for clinical breast imaging via reflectance and transillumination approach after extensive in-vivo studies.iv Chapter 2 contains the background work for this thesis, it includes the theory of optical imaging, comparison of optical with other imaging modalities, an overview of other hand-held optical imagers developed to date and a description of the Gen-1 imager complete with modifications for the Gen-2 imager. Chapter 3 contains the instrumentation of the second Generation hand-held optical imaging system. Chapters 4-7 experimental studies focus on the viability and testing of the Gen-2 imager, initially conducted on liquid phantoms and progressing to gel phantoms an finally human subject studies. CHAPTER 2: BackgroundThe background chapter provides an explanation of the basics of near-infrared optical imaging, its theory, measurement approaches, and the description of various optical imaging devices to date. The hand-held optical devices developed to date by various researchers are also described, followed by the motivation to the development of the second Generation (or Gen-2) hand-held optical imager. Basic information on near-infrared optical imagingOptical wavelengths extend from about 300-1300 nm. The energy found in these wavelengths is <10 electron volts (eV) meaning the energy found in optical wavelengths is non- Deeper tissue penetration allows optical imaging to be implemented as an imaging technology for breast cancer diagnosis and prognosis. Table 1 6 imaging provides a functional imaging modality with decent resolution and contrast while requiring less imaging time than nuclear and MRI for a less expensive device. Theory of near-infrared optical imagingBiological tissue is a high scattering low absorption medium or high (probability of photon scattering by a medium per unit path length) low (probability of absorption by a medium per unit path length). When scattering occurs the photon is directed within a range of possible deflection angles g (average of cosine of scatterin...