Optical and X-Ray Technology Synergies Enabling Diagnostic and Therapeutic Applications in Medicine

X-ray and optical technologies are the two central pillars for human imaging and therapy. The strengths of x-rays are deep tissue penetration, effective cytotoxicity, and the ability to image with robust projection and computed-tomography methods. The major limitations of x-ray use are the lack of molecular specificity and the carcinogenic risk. In comparison, optical interactions with tissue are strongly scatter dominated, leading to limited tissue penetration, making imaging and therapy largely restricted to superficial or endoscopically directed tissues. However, optical photon energies are comparable with molecular energy levels, thereby providing the strength of intrinsic molecular specificity. Additionally, optical technologies are highly advanced and diversified, being ubiquitously used throughout medicine as the single largest technology sector. Both have dominant spatial localization value, achieved with optical surface scanning or x-ray internal visualization, where one often is used with the other. Therapeutic delivery can also be enhanced by their synergy, where radio-optical and optical-radio interactions can inform about dose or amplify the clinical therapeutic value. An emerging trend is the integration of nanoparticles to serve as molecular intermediates or energy transducers for imaging and therapy, requiring careful design for the interaction either by scintillation or Cherenkov light, and the nanoscale design is impacted by the choices of optical interaction mechanism. The enhancement of optical molecular sensing or sensitization of tissue using x-rays as the energy source is an important emerging field combining x-ray tissue penetration in radiation oncology with the molecular specificity and packaging of optical probes or molecular localization. The ways in which x-rays can enable optical procedures, or optics can enable x-ray procedures, provide a range of new opportunities in both diagnostic and therapeutic medicine. Taken together, these two technologies form the basis for the vast majority of diagnostics and therapeutics in use in clinical medicine

Real-Time Quantitative Bronchoscopy

The determination of motion within a sequence of images remains one of the fundamental problems in computer vision after more than 30 years of research. Despite this work, there have been relatively few applications of these techniques to practical problems outside the fields of robotics and video encoding. In this paper, we present the continuing work to apply optical flow and egomotion recovery to the problem of measuring and navigating through the airway using a bronchoscope during a standard procedure, without the need for any additional data, localization systems or other external components. The current implementation uses a number of techniques to provide a range of numerical measurements and estimations to physicians in real time, using standard computer hardware

Secondary Electron Yield Measurements of Carbon Nanotube Forests: Dependence on Morphology and Substrate

Total, secondary, and backscatter electron yield data were taken with beam energies between 15 eV and 30 keV, in conjunction with energy emission data, to determine the extent of suppression of yield caused by carbon nanotube (CNT) forest coatings on substrates. CNT forests can potentially lower substrate yield due to both its inherently low-yield, low-atomic number (Z) carbon composition, and its bundled, high-aspect ratio structure. Rough surfaces, and in particular, surfaces with deep high-aspect-ratio voids, can suppress yields, as the electrons emitted from lower lying surfaces are recaptured by surface protrusions rather than escaping the near-surface region. Yields of multilayered materials can be modeled essentially serially as a combination of the constituents. However, it is shown that suppression of yields due to CNT forest morphology is more significant than simple predicted contributions of homogeneous layered components. This effect is found to be most pronounced at low energies, where the incident electrons interact preferentially with the CNTs. CNT forests between 20 and 50 μm tall were grown on a thick silicon substrate capped with a 3-nm diffusion barrier of evaporated aluminum using a wet injection chemical vapor deposition (CVD) method. Yields of an annealed substrate and constituent bulk materials were also investigated. At incident electron energies above ~1200 eV, the substrate secondary yield dominated those of the CNT forests, as incident electrons penetrated through the low-density, low-Z CNT forests, and backscattered from the higher-Z substrate. At lower energies \u3c1200 \u3eeV, the CNT forests substantially reduced the overall yields of the substrate, and for \u3c500 eV CNT forest yields were \u3c1, well below the already low yields of bulk graphite. This suppressed yield at low energies is attributed to the porosity and preferred vertical alignment of the CNT forest. The yield’s dependence on the height and density of the CNT forest is also discussed

Influence of Vibrationally-Induced Structural Changes on Carbon Nanotube Forests Suppression of Electron Yield

Carbon nanotube (CNT) forest coatings have been found to lower electron yield from material surfaces. The suppressed yields have been attributed to both the lower inherent yields of low-atomic number carbon and the enhanced electron recapture resulting from the morphology of the carbon layer. To explore the relative contributions of these two causes of yield suppression, tests have been made on CNT forest-coated conducting substrate samples subjected to vibrationally-induced changes of the coating structure. The extent of vibrationally-induced structural changes—due, for example, to shear-force conditions during space-vehicle transit—are of interest, as CNT have been a frequent topic of scientific curiosity and space applications due to their high tensile strength, high aspect ratio geometry, and unique electromagnetic characteristics. Their use has also been beneficial for sensor equipment, both terrestrial and space-faring, due to their extremely low photon and electron reflectivity

Suppresion of Electron Yield With Carbon Nanotube Forests: A Case Study

Electron emission of carbon nanotube (CNT) forests grown on silicon substrates was measured to investigate possible electron yield suppression due to the composition and morphology of CNT forests. CNT forests are vertically-oriented tubular formations of graphitic carbon grown on a substrate; these have been widely investigated for their extreme properties in optical, electrical, and mechanical aspects of physics and material sciences. CNT coatings are good candidates for yield reduction, in analogy with the near-ideal blackbody optical properties of CNT forests. Carbon with its low atomic number has an inherent low yield due to its low density of bulk electrons. Furthermore, the large aspect ratio of this vertically-aligned CNT allows for easy penetration of the high energy incident electrons, but enhanced recapture of lower-energy secondary electrons due to their wider angular distribution of emission. Total (TEY), secondary (SEY) and backscattered (BSEY) yield curves using 15 eV to 30 keV electron beams, along with energy emission spectra, were acquired for three CNT forest samples to determine the extent of yield suppression of the substrate due to the CNT forests [Wood, 2018]