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The Rotating Scatter Mask (RSM) system is an inexpensive retrofit that provides imaging capabilities to scintillating detectors. Unlike traditional collimator systems that primarily absorb photons in order to form an image, this system primarily scatters the photons. Over a single rotation, there is a unique, smooth response curve for each defined source position. Testing was conducted using MCNPX simulations. Image reconstruction was performed using a chi-squared reconstruction technique. A simulated 100 uCi, Cs-137 source at 10 meters was detected after a single, 50-second rotation when a uniform terrestrial background was present. A Cs-137 extended source was also tested. The RSM field-of-view is 360 degrees azimuthally as well as 54 degrees above and 54 degrees below the horizontal plane. Since the RSM is built from polyethylene, the overall cost and weight of the system is low. The system was designed to search for lost or stolen radioactive material, also known as the orphan source problem. [ABSTRACT FROM PUBLISHER]

A novel, fully reconfigurable liquid collimator device for \gamma-ray and X-ray imaging was built and tested as a coded aperture. The device contained a 10\,\times\,10 grid of 5\,\times\,5 mm^2 chambers, each 5 cm long. The chambers were either filled with an attenuating liquid, absorbing photons, or evacuated of the liquid, allowing the photons to pass. As the pattern of “on” and “off” chambers was manipulated, different, semi-independent views of the \gamma-ray source were found. A random mask sequence outperformed a uniformly redundant array when maximum-likelihood expectation maximization was used. Noise and reconstruction artifacts decreased as the number of masks increased. With ten mask patterns, the signal-to-noise ratio in images of point sources increased by a factor of 2. Images of a segmented, extended source are presented to demonstrate, qualitatively, that image quality increased when more masks were used. Additionally, the system crudely imaged a source using only the photons that Compton scattered within the mask. [ABSTRACT FROM PUBLISHER]