Author's School

School of Engineering & Applied Science

Author's Department/Program

Biomedical Engineering

Language

English (en)

Date of Award

January 2010

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

Lihong Wang

Abstract

Diagnosis of early breast cancer is the key to survival. The combined contrasts from thermoacoustic and photoacoustic tomography: TAT and PAT) can potentially predict early stage breast cancer. We have designed and engineered a breast imaging system integrating both thermoacoustic and photoacoustic imaging techniques to achieve dual-contrast: microwave and light absorption), non-ionizing, low-cost, high-resolution, three-dimensional breast imaging. We have also developed a novel concept of using a negative acoustic lens to increase the acceptance angle of an unfocused large-area ultrasonic transducer: detector), leading to more than twofold improvement of the tangential resolution in both TAT and PAT when the object is far from the scanning center. A contrast agent could be greatly beneficial for early cancer diagnosis using TAT/PAT, because the early stage intrinsic contrast can be low. We have developed a carbon nanotube-based contrast agent for both TAT and PAT. In comparison with deionized water, single-walled carbon nanotubes: SWNTs) exhibited more than twofold signal enhancement for TAT at 3 GHz, and in comparison with blood, they exhibited more than sixfold signal enhancement for PAT at 1064 nm wavelength. Using PAT in conjunction with an intradermal injection of SWNTs, we also showed the feasibility of noninvasive in vivo sentinel lymph node imaging in a rat model. We have also developed and demonstrated molecular photoacoustic imaging using unique "soft-type" colloidal gold nanobeacons: GNBs) in the near-infrared region. GNBs represent a novel class of stable, colloidal gold nanoparticles, incorporating small metallic gold nanoparticles that can clear from the body when the particles are metabolically disrupted. We have also imaged the sentinel lymph node using different sizes of GNBs, showing that size plays an important role in their in vivo behavior and uptake to the lymph nodes. In addition to providing diagnostic imaging, TAT and PAT can be used in therapy for real-time temperature monitoring with high spatial resolution and high temperature sensitivity, which are both needed for safe and efficient thermotherapy. Using a tissue phantom, these noninvasive methods have been demonstrated to have a high temperature sensitivity of 0.15 0C at 2 s temporal resolution: 20 signal averages).

Comments

Permanent URL: http://dx.doi.org/10.7936/K7MP518M

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