Showing papers on "Imaging phantom published in 1983"
TL;DR: It is found that the contrast/detail results for envelope detection in diagnostic ultrasound are almost identical with the results for square law detection with the latter serving as an upper limit for performance in lesion detection.
Abstract: Abstruct-The first- and second-order statistics of envelope detected ultrasound (US)B-mode images for the case of a scattering phantom with many scatteiers per resolution cell have been previously derived. These characteristics are integrated over the region of a simulated focal (disk) lesion and the signal-to-noise ratio (SNR) for lesion detectability is obtained. This SNR requires the average number of independent speckle cells over the lesion area (analogous to the number of x-ray photons over the lesion area in incoherent light or x-ray imaging). This number is obtained from our autocorrelation analysis (second-order statistics). By setting the SNR expression equal to the threshold value SNRT required to detect a lesion in the presence of speckle noise, the dependence of lesion contrast on lesion diameter at threshold is found, i.e., the contrast/detail function. This is a simple inverse relation for ideal observers of US B-scans. It is also found that the contrast/detail results for envelope detectionin diagnostic ultrasound are almost identical with the results for square law detection (the usual laser case) with the latter serving as an upper limit for performance in lesion detection. Finally, the results of human observer performance using a contrast/ detail phantom are compared with the predictions for optimal or ideal 2cm Fig. 1. Schematic of contrast/detail phantom for diagnostic ultrasound. performance. The results are comparable with results for photon imaging systems, with valuesof the SNR at threshold in the neighborhood of 2-3.
261 citations
TL;DR: The study verified that the sampling schemes used in the program can produce random samples according to the theoretical probability distribution functions which describe the photon-scattering process.
Abstract: A computer program using Monte Carlo methods has been developed for the simulation of photon scattering in tissue-equivalent phantoms for incident x-rays in the diagnostic energy range. The study verified that the sampling schemes used in the program can produce random samples according to the theoretical probability distribution functions which describe the photon-scattering process. The Monte Carlo program was applied to determinations of the scatter fractions and edge responses for various phantom sizes, X-ray energies, and recording systems. These quantities were also measured experimentally under comparable imaging conditions. Excellent agreement was obtained between the predicted and experimental results. This investigation established the validity of our Monte Carlo calculations for studies of the physical characteristics of scattered radiation in diagnostic radiology.
128 citations
TL;DR: A phantom that simulates CT measurements in patients and permits comparison of CT density of each nodule with a physical standard derived from clinical experience is designed and facilitates standardized quantitative analysis of pulmonary nodules with current scanners.
Abstract: The CT density of the same pulmonary nodule can vary significantly between scanners or with the same scanner because several independent factors besides partial volume averaging can affect its determination. Hence a single CT number cannot be used to distinguish calcified from noncalcified nodules, ruling out direct extrapolation of quantitative data between scanners. The authors designed a phantom that simulates CT measurements in patients and permits comparison of CT density of each nodule with a physical standard derived from clinical experience. Tests on 35 patients using a GE 8800 showed that no malignant nodules and 65% of benign lesions were more dense than the phantom nodule. This method is independent of inter- and intra-scanner variation and facilitates standardized quantitative analysis of pulmonary nodules with current scanners.
104 citations
TL;DR: The contribution made by contaminating electrons present in a clinical photon beam to the buildup dose in a polystyrene phantom has been calculated and compared to measurements and a Monte Carlo technique was employed.
Abstract: The contribution made by contaminating electrons present in a clinical photon beam to the buildup dose in a polystyrene phantom has been calculated and compared to measurements. A Monte Carlo technique was employed. The calculation was divided into two parts. First, the accelerator treatment head was simulated in detail using the EGS--PEGS electromagnetic shower code. Then, information obtained from these calculations was used to compute dose curves in a polystyrene phantom. Two cases were considered, one in which both electrons and photons were incident upon the phantom, and another in which electrons were eliminated from the incident beam. Results of these calculations agree with recent experimental findings. A decrease in buildup dose as well as a shift in d/sub max/ was observed when electrons were eliminated from the beam.
90 citations
TL;DR: To study the effect of the transducer on the final B-scan image, a computer model has been developed simulating the interaction of ultrasound with a simple scattering medium based on single scattering from a collection of points positioned randomly in a three-dimensional volume.
74 citations
TL;DR: The apparatus is capable of studying two scanning geometries that uses either a fan of radiation swept laterally over the film in 5s or a spot of radiation scanned over two dimensions in a raster pattern in 8.8s, which offers good scatter rejection and regional manipulation of film exposure.
Abstract: An experimental scanning apparatus for chest radiography is described which offers good scatter rejection and regional manipulation of film exposure. The apparatus is capable of studying two scanning geometries that uses either a fan of radiation swept laterally over the film in 5 s or a spot of radiation scanned over two dimensions in a raster pattern in 8.8 s. The manipulation of tube output during the scan is achieved by pulse width modulation with film exposure monitored by a fluorescencedetector placed behind the film cassette. Measurements of the scatter rejection properties of the system show that it is superior to that of a 10:1 grid when used with 120‐kVp radiation. Phantom images with both geometries demonstrate the capability of the system to improve uniformity of film exposure and soft tissue contrast throughout the mediastinal, diaphragmatic, and retrocardiac areas. The relative characteristics of the one‐ versus two‐dimension scan geometries are given. Clinical raster images formed with the 8.8‐s scan time show signs of motion unsharpness which becomes insignificant when the scan time is reduced to 4.5 s.
67 citations
TL;DR: The accuracy of the spectral difference method for measuring ultrasonic attenuation has been investigated using tissue-mimicking phantoms using a narrow-band substitution technique and agreement within ±10 percent was typical for measurements in homogeneous materials.
62 citations
Patent•
28 Nov 1983
TL;DR: In this paper, a test phantom and method of fabrication and use of the same is disclosed which phantom is representative of human tissue containing variable concentrations of iodine to serve as a test device in for assessing the performance of X-ray imaging systems such as digital subtraction angiographic apparatus.
Abstract: A test phantom and method of fabrication and use of the same is disclosed which phantom is representative of human tissue containing variable concentrations of iodine to serve as a test device in for assessing the performance of X-ray imaging systems such as digital subtraction angiographic apparatus. The method of fabrication provides the long-term stable incorporation of iodine into a tissue equivalent material which allows standardized testing and evaluation of X-ray imaging systems. The incorporation of additional test details into geometrically fixed positions in the phantom allows accurate and reproduceable measurements of other performance parameters of digital X-ray imaging systems.
54 citations
TL;DR: Results show that variations in quantitative behavior with reasonable changes in patient geometry do not preclude meaningful characterization of solitary lung nodules using CT scans for the three CT scanners studied, providing CT-number threshold data are derived from the same model scanner and operating conditions.
Abstract: The use of absolute CT numbers for in vivo tissue characterization is compromised by a number of technical and geometrical factors. A phantom simulating thoracic geometry and containing intrapulmonary "features" was scanned on three CT scanners allowing for assessment of CT-number variations with a wide number of scanning and geometric parameters. It was found that, with thoracic geometry, the absolute CT numbers of intrapulmonary features (e.g., solitary pulmonary nodules) can vary significantly due to a number of CT scanning parameters, such as geometry, CT scanner used, and/or time. Such variations must be taken into account when establishing criteria for characterizing tissue types using CT numbers. However, results show that variations in quantitative behavior with reasonable changes in patient geometry do not preclude meaningful characterization of solitary lung nodules (using CT-number averages) using CT scans for the three CT scanners studied, providing CT-number threshold data are derived from th...
46 citations
TL;DR: Phantoms designed to simulate cysts or avascular masses and other material encountered in computed tomographic (CT) body and head scanning were used to evaluate the effect of beam hardening in a GE CT/T 8800 scanner.
Abstract: Phantoms designed to simulate cysts or avascular masses and other material encountered in computed tomographic (CT) body and head scanning were used to evaluate the effect of beam hardening in a GE CT/T 8800 scanner. The phantoms were scanned before and after the addition of iodinated contrast material to various compartments within the phantoms. The results indicate that in general the addition of contrast material in the CT body phantom resulted in a decrease in the CT numbers recorded from the cyst phantoms. Conversely, the addition of contrast material in a concentric peripheral cylinder (simulating the addition or presence of the calvarium in CT head scanning) resulted in a generalized inhomogeneous increase in CT numbers of specimen materials contained in that ring.
40 citations
TL;DR: Initial phantom studies imply that the time to maximum opacification (tmax) can be used to determine absolute and relative blood flow with a high confidence level (r greater than .989).
Abstract: Temporal filtration of fluoroscopic video sequences is being used as an alternative to pulsed digital subtraction angiography. Using the same image processing architecture and a slight modification in processing logic a parametric image can be synthesized from such a temporally filtered image sequence in virtual real time, i.e., an image sequence that spans T seconds takes exactly T seconds to process. Off-line computer processing is not required. Initial phantom studies imply that the time to maximum opacification (tmax) can be used to determine absolute and relative blood flow with a high confidence level (r greater than .989). Phantom and animal examples are presented.
Patent•
27 Sep 1983
TL;DR: In this paper, an ultrasound phantom is provided which simulates human tissue containing tissue masses viable for biopsy, which is used to demonstrate or teach the performance of a biopsy procedure assisted by real-time ultrasonic imaging.
Abstract: An ultrasound phantom is provided which simulates human tissue containing tissue masses viable for biopsy. The phantom is used to demonstrate or teach the performance of a biopsy procedure assisted by real-time ultrasonic imaging. The phantom comprises a plurality of small balloons, filled with a viscous substance, and tied shut. The balloons are distributed through and surrounded by a gelatinous substance comprising tissue equivalent material. During a simulated biopsy procedure, a section of the phantom is imaged as a biopsy needle penetrates through the tissue equivalent material, pierces one of the balloons, and aspirates some of the viscous substance from the balloon.
TL;DR: A simple phantom has been employed to investigate the image linearity for a wide range of activity distributions and count rates and the stability against “cross-talk” from neighbouring regions is established.
Abstract: A simple phantom has been employed to investigate the image linearity for a wide range of activity distributions and count rates. The phantom is composed of two activity regions, one contains a short-lived isotope and the other a long-lived isotope. Specifically, the phantom consists of a 20 cm flood phantom containing 68Ga (half-life 1.14 h) into which a 6 cm diameter cylinder containing 64Cu (half-life 12.7 h) is placed in an off-centre position. The copper region is initially a cold spot but, after many gallium half-lives, becomes a hot spot. Successive data sets from the phantom are taken over a long period and the reconstructed images analysed to establish the linearity within each region and hence the stability against “cross-talk” from neighbouring regions.
TL;DR: It is concluded that simple dosimetric techniques can provide adequate physics background for stereotaxic radiosurgery with small radiation fields and high-energy x rays.
Abstract: Dosimetry for 10-MV x rays has been extended to radiation fields smaller than 4 X 4 cm which may be suitable for radiation therapy of small lesions, eg, intracranial tumors, benign or malignant Special consideration in this study was given to (i) the variation of dose with field size (collimator and phantom scatter), (ii) the central axis percentage depth doses, and (iii) the moving-beam therapy dose distribution We conclude that simple dosimetric techniques can provide adequate physics background for stereotaxic radiosurgery with small radiation fields and high-energy x rays
TL;DR: Small relative changes in CT numbers should be regarded with caution when comparing one substance or area with another or one study with another.
TL;DR: It is demonstrated that energy-sensitive neutron transmission measurements can be used in conjunction with computed tomography to determine spatial distributions of specific elements in a sample containing elements of biological interest.
Abstract: Neutrons and X-rays are mathematically equivalent as probes in computed tomography. However, structure in the energy dependence of neutron total cross sections and the feasibility of using time-of-flight techniques for energy sensitivity in neutron detection suggest that spatial distributions of specific substances can be determined from neutron transmission data. We demonstrate that this is possible by tomographically reconstructing from such data a phantom containing several different structural materials.
TL;DR: It was found that observers can discriminate depth differences of one to two millimeters in magnification stereoscopy, and similar performance for magnification stereoscopic cerebral angiograms is expected.
Abstract: Two types of stereoscopic phantoms were constructed to determine the sensitivity of observers in detecting depth information obtained by means of the magnification stereoscopic technique. One of these, a "plus" phantom, contained perpendicular aluminum wires at the top and bottom of steps of various thicknesses; the observer was asked to identify whether one of the wires was on the top, the bottom, or uncertain in location. The fraction of correct responses versus the height of the step was plotted, indicating the detectability of depth. Fourteen of 20 unselected observers (70%) responded consistently and were considered "good" observers. In general, the greater the stereo shift, the greater the fraction of correct responses. A second phantom, a mesh phantom, contained standard and randomly positioned test wires. The observer was asked to identify the depth position of a test wire with respect to the standard wire if they were in the same plane. It was found that observers can discriminate depth differenc...
TL;DR: An experimental system developed for studying the distribution of electric field in lossy bodies produces a map of the internal electric field intensity in a phantom model of the human body exposed in the near field of radio and microwave radiators.
Abstract: This paper describes an experimental system developed for the purpose of studying the distribution of electric field in lossy bodies. Ultimately, a map of the internal electric field intensity in a phantom model of the human body exposed in the near field of radio and microwave radiators is obtained. The field is sampled by a nonperturbing probe in a number of points under computer control using a system consisting of a microcomputer and a minicomputer. A description is given of the hardware and software components of the scanning system and the results of experimental evaluation of the performance of the system. For illustration the electric field distributions in simple configurations obtained experimentally are presented and compared with analytical results.
TL;DR: Measured phantom diameter dependence of the true count rate shows good agreement with theoretically anticipated characteristics, including maximum sensitivity at around 30cm dia, and relative system detection efficiency measured with a line source at FOV center is 96% at 15ns time window.
Abstract: A 3-detector ring, 5-slice whole-body positron CT has been developed and is being tested. The PCT, POSITOLOGICA-II, has a total of 480 BGO's (160/ring), and employs continuous rotation scan (0.5rps). By using a 15mm wide BGO, a 9.2mm FWHM spatial resolution for reconstructed image is obtained at the center of FOV. Measured phantom diameter dependence of the true count rate shows good agreement with theoretically anticipated characteristics, including maximum sensitivity at around 30cm dia. Sensitivities for 20cm dia. phantom are 28 and 38 kcps/?Ci/ml for in-plane and cross-plane, respectively, including scattered coincidences. Relative system detection efficiency measured with a line source at FOV center is 96% at 15ns time window (90% at 12ns), basing on 100% efficiency in 20-24ns.
TL;DR: The Neuro-PET is calibrated with a round or elliptical phantom that approximates a patient's head; this method eliminates the effects of scatter and self-attenuation to first order, which reduces the measured scatter to zero, as determined with a 5 cm cold spot.
Abstract: The Neuro-PET is a circular ring seven-slice positron emission tomograph designed for imaging human heads and small animals. The scanner uses 512 bismuth germanate detectors 8.25 mm wide packed tightly together in four layers to achieve high spatial resolution (6-7 mm FWHM) without the use of beam blockers. Because of the small 38 cm ring diameter, the sensitivity is also very high: 70,000 c/s per true slice with medium energy threshold (375 keV) for a 20 cm diameter phantom containing 1 ?Ci/cc of positron-emitting activity, according to a preliminary measurement. There are three switch-selectable thresholds, and the sensitivity will be higher in the low threshold setting. The Neuro-PET is calibrated with a round or elliptical phantom that approximates a patient's head; this method eliminates the effects of scatter and self-attenuation to first order. Further software corrections for these artifacts are made in the reconstruction program, which reduce the measured scatter to zero, as determined with a 5 cm cold spot. With a 1 cm cold spot, the apparent activity at the center of the cold spot is 18% of the surrounding activity, which is clearly a consequence of the limits of spatial resolution, rather than scatter. The Neuro-PET has been in clinical operation since June 1982, and approximately 30 patients have been scanned to date.
TL;DR: It is shown by a theoretical analysis, as well as by using simulated scans, that the phantom view method does tend to diminish the distant streaks more than other methods tested, and there is a point of diminishing returns in increasing the number of phantom views.
Abstract: An artefact that can occur in CT scans with too few views is the appearance of streaks at some distance from the sharp edge that causes them. We investigate, for parallel beam scanners, the effectiveness of the method of phantom views, as well as other methods of angular interpolation, in diminishing the view-limited streak artefact. The phantom view method consists of inserting data points obtained by interpolation in angle, along with the real data points. We show by a theoretical analysis, as well as by using simulated scans, that the phantom view method does tend to diminish the distant streaks more than other methods tested. Furthermore, we show that there is a point of diminishing returns in increasing the number of phantom views.
TL;DR: Although better intraplanar resolutions were obtained with the rotating slant hole, the rotating camera was found to give superior definition of a defect and less propagation between reconstructed sections of the phantom.
Abstract: Measurements were made on the tomographic imaging abilities of a rotating slant hole collimator and a rotating scintillation camera system using a standard heart phantom and thallium-201. This allowed a comparison to be made between these and published results for conventional imaging and the seven pinhole technique under standardised conditions. Although better intraplanar resolutions were obtained with the rotating slant hole, the rotating camera was found to give superior definition of a defect and less propagation between reconstructed sections of the phantom.
TL;DR: A phantom for study of uniformity, artifacts from dense structures, and consistency in pixel values was constructed and on-site studies showed that the phantom was appropriate for such measurements.
Abstract: A phantom for study of uniformity, artifacts from dense structures, and consistency in pixel values was constructed. On-site studies of eight computed tomographs belonging to the second, third, and fourth generations showed that the phantom was appropriate for such measurements. The results indicate certain inherent shortcomings in some of the present designs.
TL;DR: In this article, the parametric dependence of spatial resolution on tomographic parameters is investigated and the influence of Computerized Tomographic parameters, such as the number of angular views, ray spacings in a fan beam, the degree of collimation, and the magnitude of the object opacity, is investigated.
Abstract: The parametric dependence of spatial resolution on tomographic parameters is investigated. The influence of Computerized Tomographic parameters, such as the number of angular views, ray spacings in a fan beam, the degree of collimation, and the magnitude of the object opacity, on the spatial resolution is studied. The research was carried out using a specially designed resolution phantom. The phantom was designed to incorporate features of varying sizes, shapes and mass densities. An index of resolution is defined to quantatively express the results of this study.
TL;DR: Experimental verification of the new dichotomic sampling scheme was attempted and applied to a circular ring PET system to improve the sampling thereby the overall system resolution and its performances.
Abstract: Experimental verification of the new dichotomic sampling scheme was attempted and applied to a circular ring PET system to improve the sampling thereby the overall system resolution and its performances. In the experiment, two different types of aperture collimators were adopted for high resolution (HR) and very high resolution (VHR) imaging. In HR mode, a resolution of 6.5 mm FWHM was obtained without appreciable degradation in overall sensitivity which represents a threefold resolution improvement over the original system. In phantom studies with HR mode a sensitivity of 4500 counts/sec/?Ci/cc was obtained for a 20 cm diameter uniform phantom filled with water. VHR mode experiment was also conducted to observe the ultimate resolution capability of DICHOTOM-I system and resolution of 4.2 mm FWHM was obtained at the expense of sensitivity reduction by a factor of four from HR mode experiment.
TL;DR: The first prototypes of an abdominal phantom have been constructed, intended for eventual use in training diagnostic ultrasound personnel and in demonstrating commercial equipment.
Abstract: The first prototypes of an abdominal phantom have been constructed. The phantom is intended for eventual use in training diagnostic ultrasound personnel and in demonstrating commercial equipment. It is constructed from plastics believed to be stable and approximately tissue-equivalent at room temperature. Abdominal structures are formed from a dispersion of a polystyrene butadiene plastic in mineral oil. Polyvinyl chloride particles are incorporated to provide the desired attenuation coefficients and scattering levels. B-scans of the phantom produced realistic images, although problems associated with scanning technique and somewhat high phantom attenuation were noted. Very useful phantoms should result from relatively simple improvements in construction techniques.