Optical imaging in tissue with X-ray excited luminescent sensors

Abstract

We report a high-spatial resolution imaging technique to measure optical absorption and detect chemical and physical changes on surfaces embedded in thick tissue. Developing sensors to measure chemical concentrations on implanted surfaces through tissue is an important challenge for analytical chemistry and biomedical imaging. Tissue scattering dramatically reduces the resolution of optical imaging. In contrast, X-rays provide high spatial resolution imaging through tissue but do not measure chemical concentrations. We describe a hybrid technique which uses a scanning X-ray beam to irradiate Gd(2)O(2)S scintillators and detect the resulting visible luminescence through the tissue. The amount of light collected is modulated by optical absorption in close proximity to the luminescence source. By scanning the X-ray beam, and measuring total amount of light collected, one can measure the local absorption near scintillators at a resolution limited by the width of luminescence source (i.e. the width of the X-ray excitation beam). For proof of principle, a rectangular 1.7 mm scanning X-ray beam was used to excite a single layer of 8 μm Gd(2)O(2)S particles, and detect the absorption of 5 nm thick silver island film through 10 mm of pork. Lifetime and spectroscopic measurements, as well changing the refractive index of the surroundings indicate that the silver reduces the optical signal through attenuated total internal reflection. The technique was used to image the dissolution of regions of the silver island film which were exposed to 1 mM of H(2)O(2) through 1 cm of pork tissue.

X‐Ray Excited Luminescence Chemical Imaging of Bacterial Growth on Surfaces Implanted in Tissue

“…[15] The ability of X-ray excited optical luminescence to study silver dissolution through tissue in one dimension was also demonstrated. [16] We also showed that hollow X-ray scintillators could be used to monitor drug release in vitro and the luminescent signal could be detected at one wavelength in living mice, however, luminescent signal was detected by only irradiating a single location in living mice (not a scanned or two dimensional image) and no in vivo drug release monitoring was achieved. [17] Herein, we extended our previous work and developed an XELCI technique to non-invasively map local pH variation due to bacterial metabolic activity in two dimensions through thick tissue with high spatial resolution.…”

In Vivo X-Ray Imaging of Phosphor-Doped PDMS and Phosphor-Doped Aerogel Biomaterials

“…This term captures sensing methods of physical and chemical changes of functionalized surfaces within tissue. An example is described by Chen et al [22] where a phosphor layer was sandwiched in between a thin silver deposit and structural substrate and inserted into pig tissue. X-Ray excited visible phosphor luminescence was adequately transmitted so as to be detected outside the tissue.…”

Sensitivity study of x-ray luminescence computed tomography

“…Typical x-ray contrast agents are highly concentrated aqueous solutions (typically iodine-based), and thus cannot be employed for molecular imaging due to their high viscosity and limits on osmolality [5]. To further investigate the molecular imaging potentials for x-ray imaging, x-ray luminescence computed tomography (XLCT) has recently been studied and developed by several groups, including ours [2–4, 6–17]. …”