Thesis Committee

Brian Pogue, Ph.D. (Chair)

Shudong Jiang, Ph.D.

Keigth Paulsen, Ph.D.

Sergio Fantini, Ph.D. (Tuft University)

Abstract

Multimodaitliy imaging is becoming the standard of care for research and clinical studies.  Such an approach is able to provide complementary information which can detect and characterize tumors.  Advancing instrumentation for diffuse near-infrared spectroscopy (NIRS) within a conventional magnetic resonance imaging (MRI) scanner requires careful choices to make a true hybrid imaging system.  In this thesis, a series of system technology development studies were completed in order to analyze what was needed to prototype the next phase of this technology with detection being possible within the MRI. Initially in a breast imaging system, a set of parallel plates was used with a newly created frequency-domain and continuous wave source-detector array.  The opto-electronic sub-system was created and deployed within a previously existing MRI-coupled spectroscopy approach, principally allowing incorporation of additional NIR wavelengths beyond 850nm, with interlaced channels of photomultiplier tubes and silicon photodiodes.  This new sub-system improved the data quality and accuracy in recovery of all breast optical properties. 

While the current system is highly functional, and was deployed in a large clinical trial of over 60 subjects, the usability was found to be limited due to the cumbersome nature of the fiber-breast geometry and adaptability of the system.  Furthermore, there is a severe penalty for the lack of full breast coverage as the sensitivity of DOT to tumors drops.  Full coverage of the breast was found to be a critical.  Adding more fibers for full breast coverage is impractical due to the size of the fibers as well as the significant cost that would be incurred.   In order to solve this challenge, we have built a system which places detectors in direct contact with the patient’s tissue, thus, forgoing the long fiber optic cables used with the hybrid system and improving light throughput.

The new modular design, which allows up to 64 detectors to be used, places the detectors’ frontend electronics outside the MRI room without sacrificing the detectors sensitivity or dynamic range.  Characterization and calibration of the system is described in detail.