<p> An in-process, in-situ cure monitoring technique utilizing a guided wave-based concept for carbon fiber reinforced polymer (CFRP) composites was investigated. Two automated cure monitoring systems using guided-wave ultrasonics were developed for characterizing the state of the cure. In the first system, surface mounted high-temperature piezoelectric transducer arrays were employed for actuation and sensing. The second system motivated by the success of the first system includes a single piezoelectric disc, bonded onto the surface of the composite for excitation; fiber Bragg gratings (FBGs) and/or phase-shifted fiber Bragg gratings (PSFBGs) were embedded in the composite for distributed cure sensing. </p><p> Composite material properties (viscosity and degree of cure) evolved during cure of the panels fabricated from Hexcel^&reg; IM7/8552 prepreg correlated well to the amplitude, time of arrival, and group velocity of the guided wave-based measurements during the cure cycle. In addition, key phase transitions (gelation and vitrification) were clearly identified from the experimental data during the same cure cycle. The material properties and phase transitions were validated using cure process modeling software (e.g., RAVEN^&reg;).</p><p> The high-temperature piezoelectric transducer array system demonstrated the feasibility of a guided wave-based, in-process, cure monitoring and provided the framework for defect detection during cure. Ultimately, this system could provide a traceable data stream for non-compliance investigations during serial production and perform closed-loop process control to maximize composite panel quality and consistency. In addition, this system could be deployed as a &ldquo;smart&rdquo; caul/tool plate to existing production lines without changing the design of the aircraft/structure.</p><p> With the second system, strain in low frequency (quasi-static) and the guided wavebased signals in several hundred kilohertz range were measured almost simultaneously using the same FBG or PS-FBG throughout the cure cycle. Also, the residual strain can be readily determined at the end of the cure. This system demonstrated a real-time, in-situ, cure monitoring system using embedded multiplexed FBG/PS-FBG sensors to record both guided wave-based signals and strain. The distinct advantages of a fiber optic-based system include multiplexing, small size, embedding, utilization in harsh environments, electrically passive operation, and electromagnetic interference (EMI) immunity. The embedded multiplexed FBG/PS-FBG fiber optic sensor can monitor the entire life-cycle of the composite structure from curing, post-cure/assembly, and in-service for creating &ldquo;smart structures&rdquo;.</p><p>

<p> Cerenkov luminescence (CL) is optical radiation induced by fast, charged, particles. In the biomedical setting, it is produced by all PET radionuclides and by radiotherapy beams.</p><p> The work presented in this dissertation, spanning some five years, has sought to both investigate the utility of Cerenkov luminescence imaging (CLI) in the biomedical setting and to push the boundaries by inventing ultrasound-modulated Cerenkov luminescence imaging (USCLI), a modality that potentially mitigates the scattering limit of resolution for CLI. </p><p> Clinical applications of CLI have focused on evaluating the potential of Cerenkov luminescence as a tool for guidance during brain tumor resection. Monte Carlo simulations of a brain phantom, along with an experimental analysis scheme, were developed to recapitulate a tumor margin assessment task. The brain phantom has optical properties derived from real brain tissues, and the simulation accounts for all physics of nuclear decay, charged particles, and optical photon propagation. The relative merits of the Cerenkov luminescence signal have been compared with other decay signals in the context of an intraoperative detection task. Considering two surgically-feasible implementations, imaging with a sensitive camera or intraoperative probe, CL objectively provides the most sensitive signal when the tumor remnant resides at superficial (&lt;2 mm) depths. </p><p> CL-activated photodynamic therapy (PDT) was quantitatively explored, and progress was made toward resolving the quantitative dissonance between extraordinary published results and expected required dosimetry. Published <i> in vivo</i> results, which purport to positively demonstrate CL-activated PDT, are at least six orders of magnitude below the therapeutic threshold for PDT dosimetry. The results herein suggest that CL is unlikely to be the driver of the observed therapeutic results, and the mechanism behind these surprising results merits further investigation.</p><p> Finally, both the theory and instrumentation for USCLI, a new, high resolution imaging modality, were developed. USCLI uses ultrasound to modulate the CL signal and thereby shift the resolution-dependence from tissue optical properties to those of the ultrasound beam. Monte Carlo simulations were performed and positively demonstrate higher resolution CLI in a scattering media. Instrumentation to experimentally demonstrate and quantify ultrasound modulation of Cerenkov luminescence imaging were developed and characterized.</p><p>