Large Aperture Scanner System (LAS) Software Handbook
Software handbook includes detailed instructions for use of system software application.
99 GENERAL AND MISCELLANEOUS↗
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Operations and Maintenance Manual for Large Aperture Scanner System
Operations and maintenance manual includes detailed instructions for system assembly, use, and maintenance.
99 GENERAL AND MISCELLANEOUS↗
SU-E-T-637: Proton Aperture Quality Assurance Using Computed Tomography
Purpose: To develop an automated algorithm for aperture quality assurance for double scattering proton radiotherapy. Methods: Anterior-Posterior scout images were acquired on a CT scanner for five brass apertures (2 large, 3 small) with 120 kVp and 10mA. A semi-automated algorithm was developed for the QA process. The input includes a user selecting the scout image and the associated patient plan, field and aperture size. The program automatically thresholds the scout image. Next, a connectivity algorithm is used to determine the points associated with the central shape to obtain the contour. To compare with the plan contour, the program converts the detected and plan contours into polar coordinates, interpolates the data to a 1 degree spaced grid, and determines the differences in radial distance at each grid point. Results: The mean and maximum difference and the percentage of points with distance differences less than 1.25 mm (due to the divergent cut of the aperture) between the detected and plan field aperture contours were obtained. A repeatability coefficient was derived based on repeated scanning and processing of three of the apertures. The mean difference for five apertures was 0.44 +/−0.08 mm. The maximum difference in distance was 1.2 +/−0.23 mm for all apertures. The Repeatability Coefficient was +/−0.038 mm, indicating the technique is highly repeatable. The mean percent of points with distance less than 1.25 mm was 97.41 +/−0.35%. Conclusion: Automated CT scout image based proton aperture QA is feasible, saves time, and provides a quantitative metric for proton patient specific aperture QA.
62 RADIOLOGY AND NUCLEAR MEDICINE↗
Structural design of a vertical antenna boresight 18.3 by 18.3-m planar near-field antenna measurement system
A large very precise near-field planar scanner was proposed for NASA Lewis Research Center. This scanner would permit near-field measurements over a horizontal scan plane measuring 18.3 m by 18.3 m. Large aperture antennas mounted with antenna boresight vertical could be tested up to 60 GHz. When such a large near field scanner is used for pattern testing, the antenna or antenna system under test does not have to be moved. Hence, such antennas and antenna systems can be positioned and supported to simulate configuration in zero g. Thus, very large and heavy machinery that would be needed to accurately move the antennas are avoided. A preliminary investigation was undertaken to address the mechanical design of such a challenging near-field antenna scanner. The configuration, structural design and results of a parametric NASTRAN structural optimization analysis are contained. Further, the resulting design was dynamically analyzed in order to provide resonant frequency information to the scanner mechanical drive system designers. If other large near field scanners of comparable dimensions are to be constructed, the information can be used for design optimization of these also.
Sharp, G. R.↗
Miniature rotating transmissive optical drum scanner
A miniature rotating transmissive optical scanner system employs a drum of small size having an interior defined by a circumferential wall rotatable on a drum axis, an optical element positioned within the interior of the drum, and a light-transmissive lens aperture provided at an angular position in the circumferential wall of the drum for scanning a light beam to or from the optical element in the drum along a beam azimuth angle as the drum is rotated. The miniature optical drum scanner configuration obtains a wide scanning field-of-view (FOV) and large effective aperture is achieved within a physically small size.
Lewis, Robert↗
Evaluation of a Variable-Aperture Full-Ring SPECT System using Large-Area Pixelated CZT Modules: A Simulation Study for Brain SPECT Applications
Single photon emission computed tomography (SPECT) scanner using cadmium zinc telluride (CZT) offers improved imaging capability over conventional NaI (Tl)-based SPECT scanner. We aim to demonstrate a full-ring SPECT system design with eight large-area CZT detectors that can be used for a broad spectrum of SPECT radiopharmaceuticals and provides higher sensitivity and better spatial resolution than those of conventional NaI (Tl)-based gamma cameras. A newly-designed full-ring SPECT system is composed of 8 large-area CZT cameras (128 mm × 179.2 mm effective area) that can be independently swiveled around their own axes of rotation independently and can have radial motion for varying aperture sizes that can be adapted to different sizes of imaging volume. Extended projection data were generated by conjoining projections of two adjacent detectors to overcome the limited field-of-view (FOV) by each CZT camera. Using Monte Carlo simulations, we evaluated this new system design with digital phantoms including a Derenzo hot-rod phantom and a Zubal brain phantom. Comparison of performance metrics such as spatial resolution, sensitivity, contrast-to-noise ratio (CNR), and contrast-recovery ratio were made between our design and a conventional SPECT scanner. The proposed scanner could result in up to about 3 times faster in acquisition time over conventional scan time at same acquisition time per step. The spatial resolution of our proposed scanner was similar or better to that of the conventional scanner, and there was significant performance improvement over the conventional scanner particularly in sensitivity (approximately 4 times). Overall, we successfully reconstructed the phantom image for both 99 mTc-based perfusion and 123 I-based dopamine transporter (DaT) brain studies simulated for our new design. In particular, the striatal/background contrast-recovery ratio in 3-to-1 reference ratio was over the 0.8 for the 123 I-based DaT study. In conclusion, we demonstrated the potential of our new full-ring CZT SPECT design, showing improved performance metrics such as improved system sensitivity and CNR while maintaining other important imaging parameters such as spatial resolution.
36 MATERIALS SCIENCE↗
A Feasibility Study of a Novel Variable-Aperture Full-Ring SPECT using Large-Area Pixelated CZT Modules: Simulation Results
Emerging single photon emission computed tomography (SPECT) scanner using cadmium zinc telluride (CZT) offers improved quantitative imaging capability over conventional NaI(Tl)-based SPECT scanner. In this study, on top of the previously-developed energy-optimized parallel collimator design [1], we further evaluated a full-ring SPECT system design with eight large-area CZT detectors. In order to evaluate the imaging performance of our proposed CZT-SPECT system, we employed analytical phantom and brain phantom, using a conventional NaI(Tl)-SPECT system as a reference.
36 MATERIALS SCIENCE↗
Oceanography from satellites
It is pointed out that oceanographers have benefited from the space program mainly through the increased efficiency it has brought to ship operations. For example, the Transit navigation system has enabled oceanographers to compile detailed maps of sea-floor properties and to more accurately locate moored subsurface instrumentation. General descriptions are given of instruments used in satellite observations (altimeter, color scanner, infrared radiometer, microwave radiometer, scatterometer, synthetic aperture radar). It is pointed out that because of the large volume of data that satellite instruments generate, the development of algorithms for converting the data into a form expressed in geophysical units has become especially important.
Wilson, W. S.↗
Optical instruments
A wide angle, low focal ratio, high resolution, catoptric, image plane scanner is described. The scanner includes the following features: (1) a reflective improvement on the Schmidt principle, (2) a polar line scanner in which all field elements are brought to and corrected on axis, and (3) a scanner arrangement in which the aperture stop of the system is imaged at the center of curvature of a spherical primary mirror. The system scans are a large radial angle and an extremely high rate of speed with relatively small scanning mirrors. Because the system is symmetrical about the optical axis, the obscuration is independent of the scan angle.
Abel, I. R.↗
A coherent light scanner for optical processing of large format transparencies
A laser scanner is discussed in which the scanning beam is random-access addressable and perpendicular to the image input plane and the irradiance of the scanned beam is controlled so that a constant average irradiance is maintained after passage through the image plane. The scanner's optical system and design are described, and its performance is evaluated. It is noted that with this scanner, data in the form of large-format transparencies can be processed without the expense, space, maintenance, and precautions attendant to the operation of a high-power laser with large-aperture collimating optics. It is shown that the scanned format as well as the diameter of the scanning beam may be increased by simple design modifications and that higher scan rates can be achieved at the expense of resolution by employing acousto-optic deflectors with different relay optics.
Callen, W. R.↗
Approaches to vegetation mapping and ecophysiological hypothesis testing using combined information from TIMS, AVIRIS, and AIRSAR
The Tropical Rainforest Ecology Experiment (TREE) had two primary objectives: (1) to design a method for mapping vegetation in tropical regions using remote sensing and determine whether the result improves on available vegetation maps; and (2) to test a specific hypothesis on plant/water relations. Both objectives were thought achievable with the combined information from the Thermal Infrared Multispectral Scanner (TIMS), Airborne Visible/Infrared Imaging Spectrometer (AVIRIS), and Airborne Synthetic Aperture Radar (AIRSAR). Implicitly, two additional objectives were: (1) to ascertain that the range within each variable potentially measurable with the three instruments is large enough in the site, relative to the sensitivity of the instruments, so that differences between ecological groups may be detectable; and (2) to determine the ability of the three systems to quantify different variables and sensitivities. We found that the ranges in values of foliar nitrogen concentration, water availability, stand structure and species composition, and plant/water relations were large, even within the upland broadleaf vegetation type. The range was larger when other vegetation types were considered. Unfortunately, cloud cover and navigation errors compromised the utility of the TIMS and AVIRIS data. Nevertheless, the AIRSAR data alone appear to have improved on the available vegetation map for the study area. An example from an area converted to a farm is given to demonstrate how the combined information from AIRSAR, TIMS, and AVIRIS can uniquely identify distinct classes of land use. The example alludes to the potential utility of the three instruments for identifying vegetation at an ecological scale finer than vegetation types.
Oren, R.↗
Use of the Space Shuttle for remote sensing experimentation during the 1980's
Planned and possible future experiments that may be conducted on Space Shuttle missions of the mid and later 1980s are discussed. Remote sensing experiments will be performed on Shuttle missions STS-7, STS-9, STS-11, and STS-17, and will conduct surveys using the Modular Optoelectronic Multispectral Scanner, a multispectral linear array imager; a high-resolution metric photographic camera; the Microwave Remote Sensing experiment, with capabilities for passive and active operation as an X-band radiometer, scatterometer or synthetic aperture radar; the Large Format Camera, a high-resolution photogrammetric camera with forward motion compensation; and the four experiments of the OSTA-3 payload: Shuttle Imaging Radar-B, the Measurement of Air Pollution from Space experiment, the Feature Identification and Location Experiment, and the Large Format Camera. Conceptual plans for experiments that may be conducted in the latter part of the decade include a high spectral resolution imaging sensor, multispectral radar surveys, and multispectral measurements in the thermal infrared.
Settle, M.↗
A full-ring variable-aperture cadmium zinc telluride system for whole-body single photon emission computed tomography: realistic simulations with phantoms
Single photon emission computed tomography (SPECT) is an imaging modality that has demonstrated its utility in a number of clinical indications. Despite this progress, a high sensitivity, high spatial resolution, multi-tracer SPECT with a large field of view suitable for whole-body imaging of a broad range of radiotracers for theranostics is not available. Purpose We have designed a cadmium zinc telluride (CZT) variable-aperture full-ring SPECT scanner instrumented with a broad-energy tungsten collimator intended to fill this technological gap. The final purpose is to provide a multi-tracer solution for brain and whole-body imaging. Our static SPECT scanner breaks the paradigm of the standard dual- and triple-head rotational SPECT systems, utilizing a larger detector area in each scan increasing the sensitivity. We provide a demonstration of the performance of our design using a realistic model of our detector with simulated body-sized 99mTc phantoms. Methods We developed a realistic model of our detector by using a combination of a Geant4 Monte Carlo simulation and a CZT detector response model based on a finite element model. Our approach models the characteristic low-energy tail effect in CZT that noticeably affects the sensitivity and the quality of the scatter correction in CZT detectors. We implement a modified dual energy window scatter correction adapted to include the CZT low-energy tail effect. A dedicated correction is also developed to eliminate the undesirable truncation observed in images given the presence of detector edges and gaps between detectors, due to the non-rotational nature of our device. Corrections for the attenuation, detector response and the presence of collimators are also included. The images are reconstructed using the maximum-likelihood expectation-maximization algorithm implemented in the reconstruction open software STIR. Detector and reconstruction performance are characterized with a Derenzo phantom and a body-sized National Electrical Manufacturers Association (NEMA) Image Quality (IQ) phantom containing 99mTc. Results Our SPECT design can resolve 6.4mm rods in a Derenzo phantom and obtain a good image contrast with the IQ phantom. Explicit testing of the gap and edge correction is provided, showing an excellent performance in eliminating the image truncation artifacts. Our modified scatter correction shows no overestimation of the contrast-recovery ratio for our realistic CZT detector model, as opposed to the cases without correction and with a standard dual-energy window scatter correction. Conclusions In this paper, we further demonstrate the performance of our design for whole-body imaging purposes. This adds to our previous demonstration of improved qualitative and quantitative 99mTc imaging for brain perfusion and 123I imaging for dopamine transport with respect to state-of-the-art NaI dual-head cameras. We show that our design performs similarly to the VERITON SPECT from Spectrum Dynamics, a commercial full-ring CZT SPECT camera, with the potential advantage of the broader energy range of application given by our custom-design tungsten collimators. Here, our device combines high sensitivity and image resolution with a broad-energy imaging application for the purpose of clinical imaging and theranostics of emerging radionuclides.
62 RADIOLOGY AND NUCLEAR MEDICINE↗
CT dose equilibration and energy absorption in polyethylene cylinders with diameters from 6 to 55 cm
Purpose: ICRU Report No. 87 Committee and AAPM Task Group 200 designed a three-sectional polyethylene phantom of 30 cm in diameter and 60 cm in length for evaluating the midpoint dose D{sub L}(0) and its rise-to-the-equilibrium curve H(L) = D{sub L}(0)/D{sub eq} from computed tomography (CT) scanning, where D{sub eq} is the equilibrium dose. To aid the use of the phantom in radiation dose assessment and to gain an understanding of dose equilibration and energy absorption in polyethylene, the authors evaluated the short (20 cm) to long (60 cm) phantom dose ratio with a polyethylene diameter of 30 cm, assessed H(L) in polyethylene cylinders of 6–55 cm in diameters, and examined energy absorption in these cylinders. Methods: A GEANT4-based Monte Carlo program was used to simulate the single axial scans of polyethylene cylinders (diameters 6–55 cm and length 90 cm, as well as diameter 30 cm and lengths 20 and 60 cm) on a clinical CT scanner (Somatom Definition dual source CT, Siemens Healthcare). Axial dose distributions were computed on the phantom central and peripheral axes. An average dose over the central 23 or 100 mm region was evaluated for modeling dose measurement using a 0.6 cm{sup 3} thimble chamber or a 10 cm long pencil ion chamber, respectively. The short (20 cm) to long (90 cm) phantom dose ratios were calculated for the 30 cm diameter polyethylene phantoms scanned at four tube voltages (80–140 kV) and a range of beam apertures (1–25 cm). H(L) was evaluated using the dose integrals computed with the 90 cm long phantoms. The resultant H(L) data were subsequently used to compute the fraction of the total energy absorbed inside or outside the scan range (E{sub in}/E or E{sub out}/E) on the phantom central and peripheral axes, where E = LD{sub eq} was the total energy absorbed along the z axis. Results: The midpoint dose in the 60 cm long polyethylene phantom was equal to that in the 90 cm long polyethylene phantom. The short-to-long phantom dose ratios changed with beam aperture and phantom axis but were insensitive to tube voltage. H(L) was insensitive to tube voltage and CT scanner model. As phantom diameter increased from 6 to 55 cm, E{sub in}/E generally decreased but asymptotically approached constant levels on the peripheral axes of large phantoms. The curve of E{sub in}/E versus scan length was almost identical to that of H(L). Similarly, E{sub out}/E increased with scan length and asymptotically approached the equilibrium for large scan lengths. E{sub out}/D{sub eq} was much less than the equilibrium length L{sub eq} where H(L) = 0.98, even with scan lengths much larger than L{sub eq}. Conclusions: The polyethylene phantom designed by ICRU Report No. 87 Committee and AAPM Task Group 200 is adequately long for assessing the midpoint dose and its equilibration in CT scanning. The short-to-long phantom dose ratios and the H(L) data provided in this paper allow easy evaluations of the midpoint dose, longitudinal dose distribution, and energy absorption in polyethylene phantoms. The results of dose equilibration and energy absorption presented herein may be insightful for the clinical CT scans with various subject sizes and scan lengths.
07 ISOTOPE AND RADIATION SOURCES↗
Calibration source for remote sensors
The source described was developed as a calibration target for the multispectral scanner (MSS) which was flown on the Earth Resources Technology Satellite A (LANDSAT 1). The wavelength region of interest covered the four (4) MSS bands extending from 0.5 to 1.1 micrometers, although the target was calibrated from 0.32 to 2.5 micrometers. The following characteristics for the target were required: (1) large aperture, sufficient to accommodate an instrument with a 9 inch (23 centimeters(cm)) aperture and 2 1/2 deg field of view (fov), (2) highly diffuse energy from target, (3) high spatial uniformity across aperture area of source, (4) spectrally calibrated in absolute units, (5) stable output over long periods of time (1-2 yrs), and (6) rugged, yet portable enough to be easily transported long distances without detrimental effects on the operational capabilities of the target. Two approaches were considered: a thirty (30) inch (76 cm) diameter integrating sphere with a twelve inch (30.5 cm) exit port, or the use of one hemisphere of a 76 cm sphere in conjunction with a Kodak ektolite screen. The screen has the property of reflecting back uniformly into a well defined area the majority of the light received. After some preliminary trials it seemed that the 76 cm sphere would give the most satisfactory results.
Mclean, J. T.↗
Use of spaceborne imaging radar in regional geomorphic studies
In the past two decades, the use of both photographic and non-photographic remote sensing from satellite platforms has provided a unique capability for the observation and study of Earth and planetary surfaces. A wide range of imaging sensors that operate in different portions of the electromagnetic spectrum have yielded images of large areas that formerly were unknown or that had not previously been observed at a simultaneous instant in time. In addition, remote sensors equipped with multispectral or multiband capabilities are capable of taking data at different wavelengths simultaneously. Notable examples include the LANDSAT series of multispectral scanners, thematic mappers, and return beam vidicons. Synthetic aperture radar and LANDSAT imagery are discussed.
Ford, J. P.↗
2-D MEMS Scanner for Handheld Multispectral Dual-Axis Confocal Microscopes
We describe a 2-D microelectromechanical systems (MEMS) scanner for a handheld multispectral confocal microscope for early detection and diagnosis of cervical cancer. This paper is an expansion of work originally reported in the Proceedings of IEEE International Conference on Optical MEMS and Nanophotonics 2012. The MEMS scanner and fabrication process has been designed to improve performance for the dual-axis confocal microscopy architecture. Dual-axis confocal microscopy achieves comparable transverse and depth resolution to high numerical aperture (NA) single-axis confocal microscopy but achieves longer working distance by utilizing low-NA optics. The MEMS scanner has an inner gimbal design with torsional flexures separated from the reflectors to reduce light loss and oxide-free outer axis torsional flexures by utilizing poly vial for electrical access to the inner gimbal electrodes. The devices are large-scale batch fabricated using a double layer silicon-on-insulator (SOI) process and predice postreleasing of dies. The scanner has electrostatic optical deflection angles of 2 degrees for the single-sided inner axis at 75 V and +/- 3 degrees for the outer axis at 120 V. The device has resonance frequencies of similar to 2.48 kHz and similar to 348 z for the inner and outer axis torsional modes, respectively. Reflectance and fluorescence images with 650 mu m x 800 mu m field of view are demonstrated at 15 frames/s. The transverse (axial) resolutions are 4.78 mu m (6.2 mu m), 5.77 mu m (6.2 mu m), and 7.45 mu m (5.6 Am) for wavelengths of 561, 662, and 781 nm, respectively.
cervical cancer↗
The Laboratory for Oceans Computing Facility
The first VAX computer in the Laboratory for Oceans Computing Facility (LOCF) was installed and the facility was largely expanded. The growth is not only in hardware and software, but also in the number of users and in supporting research and development projects. The LOCF serves as a general purpose computing facility for: ocean color research projects, sea ice research projects, processing of the Nimbus-7 Coastal Zone Color Scanner data set, real time ingest and analysis of TIROS-N satellite data, study of the Synthetic Aperture Radar data, study of LANDSAT data, and many others. The physical space and the electrical power layout of the computing room were modified to accommodate all the equipment. The LOCF has several image processing stations which include two International Imaging Systems (IIS) model 75 processors and one Adage processor. The facility has the capability of ingesting the TIROS-N HRPT satellite data on a real time basis. More than 30 software packages were installed on the systems. System software packages, network software, FORTRAN and C compilers, database management software, image processing software, graphics, mathematics and statistics packages, TAE, Catalog Manager, GEMPAK, LAS and many other software developed on the LOCF computers such as SEAPAK have greatly advanced the capability of the LOCF.
Kao, R.↗