This PDF file contains the Front Matter associated with SPIE Proceedings volume 7806, including the Title page, Copyright information, Table of Contents, and Conference Committee listing.

Background: Molecular breast imaging (MBI) is a novel breast imaging technique that uses Cadmium Zinc Telluride (CZT) gamma cameras to detect the uptake of Tc-99m sestamibi in breast tumors. Current techniques employ an administered dose of 20-30 mCi Tc-99m, delivering an effective dose of 6.5-10 mSv to the body. This is ~ 5-10 times that of mammography. The goal of this study was to reduce the radiation dose by a factor of 5-10, while maintaining image quality. Methods: A total of 4 dose reduction schemes were evaluated - a) optimized collimation, b) improved utilization of the energy spectrum below the photopeak, c) adaptive geometric mean algorithm developed for combination of images from opposing detectors, and d) non local means filtering (NLMF) for noise reduction and image enhancement. Validation of the various schemes was performed using a breast phantom containing a variety of tumors and containing activity matched to that observed in clinical studies. Results: Development of tungsten collimators with holes matched to the CZT pixels yielded a 2.1-2.9 gain in system sensitivity. Improved utilization of the energy spectra yielded a 1.5-2.0 gain in sensitivity. Development of a modified geometric mean algorithm yielded a 1.4 reduction in image noise, while retaining contrast. Images of the breast phantom demonstrated that a factor of 5 reduction in dose was achieved. Additional refinements to the NLMF should enable an additional factor of 2 reduction in dose. Conclusion: Significant dose reduction in MBI to levels comparable to mammography can be achieved while maintaining image quality.

Thallium bromide (TlBr) and related ternary compounds, TlBrI and TlBrCl, have been under development for room temperature gamma ray spectroscopy due to several promising properties. Due to recent advances in material processing, electron mobility-lifetime product of TlBr is close to Cd(Zn)Te's value which allowed us to fabricate large working detectors. We were also able to fabricate and obtain spectroscopic results from TlBr Capacitive Frisch Grid detector and orthogonal strip detectors. In this paper we report on our recent TlBr and related ternary detector results and preliminary results from Cinnabar (HgS) detectors.

We have developed, fabricated and tested a prototype imaging neutron spectrometer designed for real-time neutron source location and identification. Real-time detection and identification is important for locating materials. These materials, specifically uranium and transuranics, emit neutrons via spontaneous or induced fission. Unlike other forms of radiation (e.g. gamma rays), penetrating neutron emission is very uncommon. The instrument detects these neutrons, constructs images of the emission pattern, and reports the neutron spectrum. The device will be useful for security and proliferation deterrence, as well as for nuclear waste characterization and monitoring. The instrument is optimized for imaging and spectroscopy in the 1-20 MeV range. The detection principle is based upon multiple elastic neutron-proton scatters in organic scintillator. Two detector panel layers are utilized. By measuring the recoil proton and scattered neutron locations and energies, the direction and energy spectrum of the incident neutrons can be determined and discrete and extended sources identified. Event reconstruction yields an image of the source and its location. The hardware is low power, low mass, and rugged. Its modular design allows the user to combine multiple units for increased sensitivity. We will report the results of laboratory testing of the instrument, including exposure to a calibrated Cf-252 source. Instrument parameters include energy and angular resolution, gamma rejection, minimum source identification distances and times, and projected effective area for a fully populated instrument.

The ion photon emission microscope (IPEM), a new radiation effects microscope for the imaging of single event effects from penetrating radiation, is being developed at Sandia National Laboratories and implemented on the 88" cyclotron at Lawrence Berkeley National Laboratories. The microscope is designed to permit the direct correlation between the locations of high-energy heavy-ion strikes and single event effects in microelectronic devices. The development of this microscope has required the production of a robust optical system that is compatible with the ion beam lines, design and assembly of a fast single photon sensitive measurement system to provide the necessary coincidence, and the development and testing of many scintillating films. A wide range of scintillating material for application to the ion photon emission microscope has been tested with few meeting the stringent radiation hardness, intensity, and photon lifetime requirements. The initial results of these luminescence studies and the current operation of the ion photon emission microscope will be presented. Finally, the planned development for future microscopes and ion luminescence testing chambers will be discussed.

A₂BLnX₆ elpasolites (A, B: alkali; Ln: lanthanide; X: halogen), LaBr₃ lanthanum bromide, and AX alkali halides are three classes of the ionic compound crystals being explored for γ-ray detection applications. Elpasolites are attractive because they can be optimized from combinations of four different elements. One design goal is to create cubic crystals that have isotropic optical properties and can be grown into large crystals at lower costs. Unfortunately, many elpasolites do not have cubic crystals and the experimental trial-and-error approach to find the cubic elpasolites has been prolonged and inefficient. LaBr₃ is attractive due to its established good scintillation properties. The problem is that this brittle material is not only prone to fracture during services, but also difficult to grow into large crystals resulting in high production cost. Unfortunately, it is not always clear how to strengthen LaBr₃ due to the lack of understanding of its fracture mechanisms. The problem with alkali halides is that their properties decay rapidly over time especially under harsh environment. Here we describe our recent progress on the development of atomistic models that may begin to enable the prediction of crystal structures and the study of fracture mechanisms of multi-element compounds.

Radiation therapy typically employs high energy photon beams because the low absorption coefficient at these energies minimizes skin dose with a conventional, unfocused beam. At orthovoltage energies less than 150 keV, the maximum dose for a single beam occurs very close to the skin surface. However a well-focused beam of low energy x rays can provide much higher flux at the target depth while sparing dose to the skin. The measured focal spot size for the polycapillary optic was 0.2 mm and was found to remain unchanged through 50 mm of phantom thickness. The calculated depth-dose curve was found to peak several centimeters below the surface with 25-40 keV radiation. Modeling indicates that the tumor dose would remain much higher than the skin dose even after scanning to cover a 1 cm³ tumor.

SALOME (an acronym for Small Angle Lab Operation Measuring Equipment) is a versatile, energy-dispersive x-ray diffraction imaging (XDi) test-bed facility commissioned and supported by the Transportation Security Laboratory, Atlantic City, USA. In work presented here, the Inverse Fan-beam (IFB) topology has been realized on SALOME and used to investigate the liquids identification capability of x-ray diffraction (XRD). Liquids were investigated from four classes of materials of relevance to security screening of aircraft passenger luggage; namely: dilute aqueous liquids; concentrated aqueous liquids; hydrocarbon fuels; and oxidizers. A set of features associated with the Molecular Interference Function (MIF) were used to classify the liquids. Within the limited scope of this investigation, XRD proved to have excellent capability for discriminating liquids from one another; in particular, for isolating the threat materials without raising false alarms from either household or innocuous substances. Consequences for XRD-based screening of air passenger luggage are summarized.

Our laboratory has investigated the efficacy of a suite of color calibration and monitor profiling packages which employ a variety of color measurement sensors. Each of the methods computes gamma correction tables for the red, green and blue color channels of a monitor that attempt to: a) match a desired luminance range and tone reproduction curve; and b) maintain a target neutral point across the range of grey values. All of the methods examined here produce International Color Consortium (ICC) profiles that describe the color rendering capabilities of the monitor after calibration. Color profiles incorporate a transfer matrix that establishes the relationship between RGB driving levels and the International Commission on Illumination (CIE) XYZ (tristimulus) values of the resulting on-screen color; the matrix is developed by displaying color patches of known RGB values on the monitor and measuring the tristimulus values with a sensor. The number and chromatic distribution of color patches varies across methods and is usually not under user control. In this work we examine the effect of employing differing calibration and profiling methods on rendition of color images. A series of color patches encoded in sRGB color space were presented on the monitor using color-management software that utilized the ICC profile produced by each method. The patches were displayed on the calibrated monitor and measured with a Minolta CS200 colorimeter. Differences in intended and achieved luminance and chromaticity were computed using the CIE DE2000 color-difference metric, in which a value of ΔE = 1 is generally considered to be approximately one just noticeable difference (JND) in color. We observed between one and 17 JND's for individual colors, depending on calibration method and target. As an extension of this fundamental work¹, we further improved our calibration method by defining concrete calibration parameters for the display, using the NEC wide gamut puck, and making sure that those calibration parameters did conform, with the help of a state of the art Spectroradiometer, PR670. As a result of this addition of the PR670, and also an in-house developed method of profiling and characterization, it appears that there was much improvement in ΔE, the color difference.

SALOME (an acronym for Small Angle Lab Operation Measuring Equipment) is a versatile, energy-dispersive x-ray diffraction imaging (XDi) test-bed facility; commissioned, funded and supported by the Transportation Security Laboratory, Atlantic City, USA. In work presented here, SALOME has been used to investigate the photon collection efficiency of three beam topologies that have been proposed for Next-Generation XDi, namely: Direct Fan-beam (DFB); Parallel Beam (PB); and Inverse Fan-beam (IFB). The single channel replication unit for each of the three topologies was implemented on SALOME. The apertures defining each topology were varied in width, influencing both the detector scatter signal and the momentum resolution. A small powder graphite sample was used as reference object for these measurements, as it provided simultaneous data on counting rate as well as peak resolution for the selected Bragg peak. The photon collection efficiencies at constant momentum peak width for the DFB, PB and IFB topologies were found to follow the trend (from lowest to highest, respectively) conjectured elsewhere in the scientific literature.

Polycrystalline Mn²⁺ doped (0.5 wt%) MgSO₄ has been prepared by using recrystallization method. The defect assisted thermally stimulated luminescence (TSL) properties of Mn²⁺ doped MgSO₄ induced by X-rays, were studied in the dose range of 0.25 to 1.0 Gy. The resultant glow curves show an intensive glow peak around 475 K accompanied by one shoulder at 428 K. Computerized glow curve deconvolution tool is used to evaluate the effective trapping parameters and suggests quasi-continuous distribution of traps in the range of 0.50-1.08 eV. An important feature of this phosphor is its 'non-shifting T_m (peak temperature)' property when the sample is subjected to various doses of X-irradiation. TSL sensitivity of pure MgSO₄ phosphor is enhanced with the incorporation of Mn2+ impurity. The TSL response of this sample as a function of absorbed dose up to 1.0 Gy suggests that it will be also very suitable for detecting very small exposures of low energy X-rays and γ-rays.

Current spectroscopic detector crystals contain defects that prevent economic production of devices with sufficient energy resolution and stopping power for radioisotope discrimination. This is especially acute for large monolithic crystals due to increased defect opportunity. The proposed approach to cost reduction starts by combining stereoscopic IR and ultrasound (UT) inspection coupled with segmentation and 3D mapping algorithms. A "smart dicing" system uses "random-access" laser-based machining to obtain tiles free of major defects. Application specific grading matches defect type to anticipated performance. Small pieces combined in a modular sensor pack instead of a monolith will make the most efficient use of wafer area.

Despite the outstanding scintillation performance characteristics of CeBr₃ and LaBr₃:Ce, commercial availability and application is limited due to the difficulties with crystal growth of large, crack-free single crystals of these fragile materials. Aliovalent doping was employed to strengthen CeBr3 in an effort to ease crystal growth constraints and improve ingot yields. Six divalent (Ca²⁺, Sr²⁺, Ba²⁺, Zn²⁺, Cd²⁺ and Pb²⁺) and two tetravalent cations (Zr⁴⁺ and Hf⁴⁺) were investigated as dopants to strengthen CeBr3 without negatively impacting scintillation performance. Ingots containing nominal concentrations of 500ppm and 1000ppm of each dopant were grown. Fluorimetry, preliminary scintillation, and preliminary fracture toughness measurements are presented for these aliovalently-doped scintillators. While Ca²⁺, Zn²⁺, Cd²⁺, and Hf⁴⁺ all exhibited little or no change in the peak fluorescence emission for 300nm excitation, Sr²⁺, Ba²⁺, Pb²⁺, and Zr⁴⁺ exhibited varying degrees of red-shifting. As expected, Pb²⁺ had a drastic detrimental effect on scintillation. Initial microindentation data indeed indicates a noticeable increase in the fracture toughness of the doped crystals as compared to undoped CeBr₃.