Micro gamma camera optics with high sensitivity and resolution (Invited Paper)

Abstract

Polycapillary x-ray optics are bundles of micron size hollow tubes, inside of which x rays are propagated by total reflection much like visible light in solid fiber optics. The small critical angle for total reflection from the glass walls of the tubes, 0.06° at 27 keV, results in very high angular selectivity. The field of view of each capillary tube is limited by this angular acceptance to less than 50 microns at a source-to-optic distance of 2 cm. Each adjacent tube works in parallel so that a large area can be covered at this resolution with much higher count rate than for a single collimator. Measurements have been performed using 125 I brachytherapy seeds in Lucite phantoms using the optics and imaging detectors. Measured resolutions were detector-limited at better than 0.1 mm. Calculations for expected sensitivity and signal-to-background ratios were developed from geometrical models and show good agreement with measurements. Results indicate that the optics provide superior signal count rates to conventional collimators for geometries such as small animal imaging in which sub millimeter resolution with inch-wide or larger fields of view are desirable.

Dynamics of Surfactant-Suspended Single-Walled Carbon Nanotubes in a Centrifugal Field

“…The analysis reveals the progressively greater uptake of SDS molecules (i.e., greater SC desorption) as SWNT diameter increases (Table ). This is consistent with the higher activation energies required by SC to desorb from most small-diameter nanotubes. , The ability of the 3:2 weight ratio to separate metals from semiconductors can be explained by the stronger interaction of SC with the former. Apart from the fact that cholate suspends more nanotubes as a result of its naphthenic structure, the proximity of the hydroxyl groups in the cholate molecule to the nanotube surface results in electronic polarization toward the SWNT .…”

“…At this juncture, we would like to emphasize that the 1:1 replacement of SC by SDS was assumed because of the lack of information involving any other adsorption scheme. It is entirely possible that not all the cholate molecules will be replaced by SDS, which still raises the density of the nanotube, while conforming to the approximate diameter dependence of SC desorption. , …”

Focusing Polycapillary Optics and Their Applications

“…Beam shaping is particularly intriguing for small animal imaging. An example of a focusing optic used to collect combined computed tomography (CT) and micro Single Particle Emissision CT (SPECT) images is shown in Figure 35 [107,108]. Collecting both the external CT beam and the scintigraphy image with a single optic decreases registration error when combining scintigraphy images from a conventional γ camera with CT data.…”

Microscintigraphy with high resolution collimators and radiographic detectors

“…[15][16][17] The small hole size has also been demonstrated in earlier preliminary measurements to give high spatial resolution in measurement of radioactive sources. [18][19][20] FIG. 1.…”