Melanie Freed

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The authors have designed and constructed a small-animal adaptive SPECT imaging system as a prototype for quantifying the potential benefit of adaptive SPECT imaging over the traditional fixed geometry approach. The optical design of the system is based on filling the detector with the region of interest for each viewing angle, maximizing the sensitivity,(More)
We have designed and constructed a small-animal adaptive SPECT imaging system as a prototype for quantifying the potential benefit of adaptive SPECT imaging over the traditional fixed geometry approach. The optical design of the system is based on filling the detector with the object for each viewing angle, maximizing the sensitivity, and optimizing the(More)
Variability in diagnostic performance of breast dynamic contrast-enhanced MRI has highlighted the need for improved standardization. While guidance exists on some aspects of the technique, currently, there is no standardized method for selecting repetition time and flip angle, which are important determinants of image contrast. This study develops a(More)
In this paper, we consider a prototype of an adaptive SPECT system, and we use simulation to objectively assess the system's performance with respect to a conventional, non-adaptive SPECT system. Objective performance assessment is investigated for a clinically relevant task: the detection of tumor necrosis at a known location and in a random lumpy(More)
A survey of 30 nearby M6.0-M7.5 dwarfs with Ks < 12 mag utilizing the Hokupa’a adaptive optics system at the Gemini North Telescope has discovered 3 new binary systems. All 3 systems have separations between 0.120.29 (3 10AU) with similar mass ratios (q> 0.8, ∆Ks < 0.7). This result gives further support to the suggestion that wide (a> 20AU) very low mass(More)
PURPOSE MANTIS is a Monte Carlo code developed for the detailed simulation of columnar CsI scintillator screens in x-ray imaging systems. Validation of this code is needed to provide a reliable and valuable tool for system optimization and accurate reconstructions for a variety of x-ray applications. Whereas previous validation efforts have focused on(More)
PURPOSE Accurate models of detector blur are crucial for performing meaningful optimizations of three-dimensional (3D) x-ray breast imaging systems as well as for developing reconstruction algorithms that faithfully reproduce the imaged object anatomy. So far, x-ray detector blur has either been ignored or modeled as a shift-invariant symmetric function for(More)
We plan to take advantage of the unprecedented combination of low thermal background and high resolution provided by the 6.5m MMT’s adaptive secondary mirror, to target the 3-5 micron atmospheric window where giant planets are expected to be anomalously bright. We are in the process of building a 3-5 micron coronograph that is predicted to be sensitive to(More)
Phantoms for dynamic contrast enhanced (DCE) imaging modalities such as DCE computed tomography (DCE-CT) and DCE magnetic resonance imaging (DCE-MRI) are valuable tools for evaluating and comparing imaging systems. It is important for the contrast-agent distribution within the phantom to possess a time dependence that replicates a curve observed clinically,(More)
Clio is an adaptive-optics camera mounted on the 6.5 meter MMT optimized for diffraction-limited L’ and M-band imaging over a ∼ 15 field. The instrument was designed from the ground up with a large well-depth, fast readout thermal infrared (∼ 3−5μm) 320 by 256 pixel InSb detector, cooled optics, and associated focal plane and pupil masks (with the option(More)