Edward S. Kenney

Microprocessor controlled multichannel dynamic radiograph

The essential concepts, design and operation of a microprocessor controlled multichannel dynamic radiograph are described. This dynamic radiograph, which detects radiation scattered from within the chest cavity, is used to accurately monitor two- and three-dimensional epicardial motion patterns. The basic concepts of the new radiograph are validated with a set of experiments on mechanical models. The results of the initial testing on experimental animals are presented.

Implementing an automatic control system for dynamic radiography

The basic detection system used for dynamic radiography is reviewed. Some practical factors are discussed in the application of dynamic radiography to the mapping of epicardial motion in canines. A fluoroscopic aiming technique is described for hitting specific points on the cardiac silhouette. The development and design of an automatic control system for dynamic radiography is covered. This system accomplishes automatic detector scanning to the proper depth, as well as calibration of the output signal. This output displays the surface position in millimetres. Some results from canine studies are discussed.ZusammenfassungDas für dynamische Radiographie verwendete grundlegende Aufdeckungs-system wird besprochen. Einige praktische Faktoren bei der Anwendung von dynamischer Radiographie auf die Abbildung epikardialer Bewegung bei Hunden werden diskutiert. Es wird ein fluoroskopisches Zielverfahren zum Treffen spezifischer Punkte auf der Herz-Silhoutette beschrieben. Die Entwicklung und Konstruktion eines automatischen Regelsystems für DRG wird eingeschlossen. Dieses System erzielt automatische Detektorabtastung auf die richtige Tiefe, wie auch Kalibrierung des Ausgangssignals. Dieser Ausgang zeigt die Oberflächenlage in mm an. Einige Resultate aus Untersuchungen an Hunden werden besprochen.SommaireLe système de détection de base utilisé en radiographie dynamique est passé en revue. On étudie certains facteurs d’ordre pratique intervenant dans l’application de la radiographie dynamique au tracé du mouvement épicardiaque chez les chiens. On expose une technique de visée fluoroscopique pour atteindre des points particuliers de la silhouette cardiaque. La mise au point et la conception d’un système de réglage automatique en radiographie dynamique sont traitées. Ce système permet une détection par balayage automatique à la profondeur voulue ainsi que l’étalonnage du signal de sortie. Le signal de sortie permet de montrer la position en millimètre de la surface. Certains résultats obtenus par des études sur des chiens sont évalués.

The Measurement of Multidimensional Myocardial Dynamics Using Scattered Radiation Fields

A new radiographic device, based upon the analysis of scattered radiation fields, has been developed to measure myocardial dynamics. The device consists of an array of detectors arranged to monitor photons scattering from the epicardial surface. Data synthesis permits real-time dynamic displays of the epicardial surface in two and three dimensions. The system has been tested on close-chest canines. Epicardial surface displacements within the closed chest cavity can be measured to 0.1 mm (S.D.). Right or left ventricular surfaces may be monitored on a given scan. Surfaces behind or in front of outer myocardial boundaries within the direct field of view of the detectors are located with equal accuracy. Except for the use of low levels of fluoroscopic x-rays, the procedure is completely noninvasive. Radiation dose levels and component costs for the prototype system are modest. The detector system attaches to a standard fluoroscopic x-ray generator.

Microwave diagnosis of a plasma generated in a reactor and its use as a reactor power monitor

Abstract The plasma produced in a gas filled microwave cavity has been studied by subjecting the cavity to the intense gamma fields present during pulsing operation of a TRIGA nuclear reactor. The cavity studied was designed to serve as an in-core power monitor for extreme power transients and to fulfill the need for a detector of essentially unlimited life. The influence of varying gas pressure and impurity concentration and the effect on sensitivity has been evaluated. High impurity concentrations have been found to greatly influence the cavity performance, reducing free electron densities but improving the response time of the device as a reactor power transient monitor. A prototype device measured gamma ray dose rates from 2 × 10 8 to 2 × 10 10 R/h using natural helium contained in an aluminum cavity. The results are within reasonable agreement with theoretical predictions considering the necessary extrapolation of plasma data.

Delayed neutron spectrum from 87Br created in thermal fission of 235U

Abstract The delayed neutron spectrum from 87 Br beyond 100 keV was measured by a methane filled proton recoil proportional counter. Major peaks were observed at 131 and 192 keV and much smaller peaks at 261, 337, 420, and 520 keV. The observed spectrum is significantly softer compared to the previously reported data.

Dynamic Radiography A New Imaging Technique Using Penetrating Radiation

One of the authors (ESK) and his students (Refs. 1-4) have, for several years, investigated system dynamics information contained in the gamma ray field emerging from an operating nuclear reactor core. Early experiments were directed along the lines of obtaining the sys-tem transfer function (frequency response). Either a driven perturbation or the natural noise generated in a neutron chain reaction represented the input to the system. The emerging gamma rays represented the system output. In later experiments, two highly collimated detectors were used to respond to the gamma rays generated in two narrow, intersecting channels through the reactor core. As with the earlier experiments, either a driven perturbation or natural noise phenomena can be used as dynamic system input. Selectivity in gamma ray energy detection and correlation of the two detector outputs yield information regarding the fission rate in the volume of intersection of the two channels under surveilance provided that the input process correlation is of dimensions on the order of (or smaller than) the volume of intersection.

An automated system for gamma radiation field mapping

Abstract Remote radiation survey equipment was sorely needed at Chernobyl but adequate systems did not exist. The current state of the art still consists of a survey meter mounted on a robotic carriage, which scans an area at many points on a grid. This process is both time consuming and somewhat inaccurate. The system we have developed will overcome these limitations, and would provide significant savings in man-hours and man-rem over manual survey techniques. The system we have developed consists of a collimated ionization chamber mounted in a scanning head. The measurement process is similar to that used in medical computed tomography (CT) imaging and consists of a series of collimator rotations and translations. The key to this work is the use of a collimator to provide position information with a position insensitive detector. In addition, an inverse filter image reconstruction technique has been used to reduce the distortion effects due to the scanner and scanning process in the resulting maps. This technique models the distortion as a linear, space invariant degrading function which is removed in a deconvolution process. We have constructed first- and second-generation prototype scanners, and developed software to produce three-dimensional radiation field “iso-dose” maps. The iso-dose maps will be superimposed on three-dimensional computer-aided design and drafting (CADD) drawings of the radiation area, aiding in the characterization of the source of radiation.

A high speed Compton scatter pipe wall imaging system

In this study, the main features of a wide-aperture Compton scattering pipe thinning measuring system are investigated, using a simplified analytical model. Two new techniques have been developed to quantitatively measure pipe wall thickness for empty and water filled pipes with and without heat insulation, using a specially designed wide-aperture annular detector. It was found that the geometric effect plays a central role in system behavior and system arrangement. High efficiency and stability of this system make snap-shot type measurements possible and reliable. A simple counting rate method reduces the complexity of the associated electronic data acquisition system. Quantitatively measuring pipe wall thickness is achievable with good sensitivity and resolution up to about 1 cm pipe wall thickness. A relatively low source activity (30 mCi) and low energy (279 keV) 203Hg source makes the system weigh less than 16 lb (shielding designed for up to 0.5 Ci capacity). Based on the principle studied, a wide-aperture Compton pipe wall imaging system has been developed. Preliminary experimental results are reported and agree well with the analytical model.

A new pipe wall thinning inspection system

By introducing wide-aperture detectors, the efficiency of the conventional Compton scatter imaging technique can be greatly improved. This paper reports on a Monte Carlo method developed to investigate the imaging process of this enhanced Compton imaging technique. Using this technique, a conceptual design of a pipe inspection system has been completed. This system feature the use of dual wide-aperture detectors and a photon source of two energy components. In practice, a source of more than two energy components is allowed. With the inspection system, the inner surface contours of the pipe can be reconstructed in a rather straightforward manner, and the inner surface can be fully mapped. The measured data together with the associated geometry parameters such as size and curvature will serve to provide a two- or three-dimensional contour mapping of the pipe.

An improvement of Compton scatter imaging with wide aperture detectors a Monte Carlo study

A novel NDT (nondestructive testing) imaging technique which is based on the measurement of Compton-scattered photons and uses wide-aperture detectors has been developed. With this technique, the inspection speed can be improved because the scanning activities can be reduced by one degree of freedom. Using wide-aperture detectors serves to simplify the design of measurement systems, and the data collection time at each step in the scanning process can be reduced due to the removal of the usual efficiency-reducing focusing collimator. To study the imaging process of the novel NDT system, a number of Monte Carlo calculations have been performed. The Monte Carlo code has been validated by comparison to the widely accepted general-purpose MCNP (Monte Carlo neutron-photon) code and has been found to run over ten times faster than the MCNP code for this particular research. As a result, the NDT system has been designed to deal, in particular, with the pipe wall thinning problems widely observed in nuclear power plants and some fossil power plants. In this application, the contour of a pipe inner surface can be reconstructed in a very straightforward manner, and the scanning activities can be reduced from three dimensions to two dimensions. >