Mechanical Scanning Device Research Articles

Scanning E-field sensor device for online measurements in annular phased-array systems

Purpose: A measurement device for noninvasive and simultaneous control of antennas during regional radiofrequency (rf) hyperthermia and, subsequently, the estimation of the power distribution in the interior of patients are essential preconditions for further technological progress. Aiming at this, the feasibility of an electro-optical electric field sensor was investigated during clinical rf hyperthermia.Material and Methods: The electro-optical electric field (E-field) sensor is based on lithiumniobate crystals and the Mach–Zehnder interferometer structure, and was tested in an earlier phantom study. For this study, a mechanical scanning device was developed allowing the registration of the E-field during clinical application. Data were recorded along a curve in the water bolus of the SIGMA 60 applicator of the annular phased-array system BSD-2000 (BSD Medical Corp., Salt Lake City, UT) close to the base points of the flat biconical dipole antennas. The results were compared with modeling calculations using the finite-difference time-domain (FDTD) method. For the latter, different antenna models were assumed. For systematic registration of the E-field curves in amplitude and phase, we employed an elliptical lamp phantom with fat-equivalent ring (filled with saline solution) and an elliptical polyacrylamide phantom with acrylic glass wall. Further measurements were carried out during the treatment of 5 patients with 20 hyperthermia treatments.Results: Data of both phantom and patient measurements can be satisfactorily described by the FDTD method, if the antenna model is refined by taking into account the conical form of the dipoles and the special dielectric environment of the feeding point. Phase deviations can be entered ex posteriori for correction in the calculation algorithm. A comparison of amplifier power measurement (forward and backward power) and bolus E-field scans near the antenna base points demonstrates that E-field measurements between antennas and patient are a necessity for the appropriate characterization of antenna radiation properties. These measurements are sensitive to variations of the lossy medium in position and shape, and can be correctly predicted with current models. However, the differences between different patients are moderate and unspecific in both calculations and measurements, with fluctuations at maximum of 30° in phases and 40% in amplitudes.Conclusions: The measurement method presented here turned out to be a practical tool for online registration of E-fields in phases and amplitudes along arbitrary curves in a water bolus or phantom. It can be utilized to evaluate antenna design and modeling calculations and leads, thus, to a better understanding of complicated multiantenna systems. In clinical routine, it can be employed as input for patient-specific hyperthermia planning and, finally, for the realization of online control with subsequent optimization of the power distribution in the patient.

A CCD imaging spectrograph in the improved solar tower of Nanjing University

Since 1992 the solar tower telescope of Nanjing University (118°51′ E, 32°03′ N) as well as its multichannel solar spectrograph, originally established in 1982, have been reconstructed and a two-channel imaging spectrograph has been operated successfully. The apertures of the coelostat and the secondary mirror are both 60 cm. The spherical objective mirror, having an aperture of 43 cm and a focal length of 2170 cm, produces a solar image of 20 cm diameter. Two auxiliary telescopes using a small fraction of the coelostat's aperture were set up for guiding and Hα monochromatic monitoring. A multichannel spectrograph can be operated in six wavebands simultaneously. A CCD imaging spectrograph can be used for data acquisition at Hα and Caii K line wavebands automatically and simultaneously. The instrument consists of two CCD cameras, an image processor (SR-151), a personal computer, and a mechanical scanning device. The principal characteristics of the instruments are described. Some observational results are presented as examples.

Ultrasound Attenuation Imaging in the Os Calcis: An Improved Method

A complete assessment of the broadband ultrasonic attenuation (BUA) distribution within the os calcis was made using an ultrasonic mechanical scanning device with focused transducers. Measurements were performed on 12 os calces removed from fresh female cadavers. We present the first images of BUA of the os calcis. Reasonably high quality images were obtained compared to computed tomography. The resolution provided by the focused transducers is approximately 4 or 5 mm in the focal zone. Compared to dual energy X-ray absorptiometry (DEXA) or quantitative computed tomography, ultrasound imaging of the os calcis offers the possibility of controlling the placement, size and shape of the region of interest and to use multiple measurement sites. DEXA was used systematically to measure the bone mineral density (BMD) of the os calces. A highly significant correlation between BMD and BUA was found (r=0.97 p<0.001).

A measurement system for continuous wave ultrasound fields

A measurement system for evaluating ultrasound fields is presented. The system utilizes a PVDF hydrophone and a mechanical scanning device. For continuous wave (CW) ultrasound, a high sensitivity is achieved by using a narrow band technique. The high sensitivity is demonstrated in a recording of the beam profile from an air transducer. Recordings from fetal Doppler equipment shows that, due to interference between the multiple transmitters, a high spatial resolution is needed in the field measurements in order to obtain correct values for peak intensities.

Element mapping by a scanning X‐ray system

AbstractPhysical surface analysis methods using charged particles on the excitation side can easily be applied to elemental distribution mapping. One common feature of all known methods is that they work on a micron scale, with respect to spatial resolution and investigated sample area. This paper deals with a new approach to the problem of element mapping using X‐ray fluorescence radiation. In contrast to the well‐known scanning procedures, this method allows the investigation of larger areas (several square centimetres) at lower spatial resolutions (≳ 100 μ). The method applies a mechanical scanning device, a modern energy‐dispersive detector and a computer. The scanning unit allows translation and rotation movements of the sample. By generating a line‐shaped X‐ray beam and translating the sample across the fixed X‐ray strip while measuring the intensity of the fluorescence radiation in a specified energy window, one obtains a strip resolution of the species investigated. If many translation measurements are made under different angular orientations of the sample, a computer converts the strip resolutions of the scanning profiles into a point resolution of the specified element. The mathematical background is known in the literature as ‘representation of a function by its line integrals’ or ‘image reconstruction from projections’. Computer simulation studies and experimental results will be discussed.

An infrared image converter equipped with an array of extrinsic silicon photodetectors

A scanning infrared image converter is described in which the line scanning is performed by sampling of the signals from a one-dimensional array of identical detectors, thus eliminating the need for a fast mechanical line scanning device. Gallium-doped silicon acting as an extrinsic photoconductor at an operating temperature of 4°K has been chosen as a detector material. A temperature resolution of 0.1-0.2°C at a speed of 50 frames/s is obtained with the apparatus. This limitation of the resolution can be ascribed to errors in the gain adjustment of the preamplifiers, the noise equivalent temperature difference of the detectors being much lower than the experimental temperature resolution value.

An automated wall thickness tester

This paper describes a tester used to measure the wall thickness of radioactive waste storage vessels. The tester utilizes the conventional ultrasonic pulse echo principle. Thickness maps are read out on a digital computer and printed to the nearest hundredth of an inch on the computer typewriter. Information on transducer location is obtained from shaft encoders coupled to the mechanical vessel scanning device. Thickness and transducer location information are transmitted to a digital computer for processing, via a telephone data transmitting system. The system is used to determine the effect of process corrosion during long-term waste storage.

LOCATION OF BRAIN TUMORS WITH POLYVINYLPYRROLIDONE-I131.

In recent years, improvements in instrumentation (collimators, mechanical scanning devices, and so forth) and the availability of a greater variety of radioactive isotopes and substances labelled with isotopes have led to renewed optimism regarding the use of scanning methods for locating intracranial tumors. To the clinician these methods represent a valuable adjunct to standard contrast studies, and to the patient, a more tolerable diagnostic procedure. Various agents, including arsenic, copper, potassium, phosphorus, iodoalbumin, and sodium iodide, have been used, paralleling progressive refinement of detection systems. 1-7 However, results have been of limited value, until the recent introduction of chlormerodrin, 8 with accuracy remaining considerably below that afforded by the classical contrast studies. Part of the reason for this failure is the accumulation of the tracer agents in muscle, thereby interfering with detection of lesions in the posterior fossa deep to the suboccipital musculature. Also there has been concern about irradiation

Scanning Microscope for Photoelectric Data Evaluation

This paper describes a mechanical scanning device for evaluation of microscopic data over a large area and an electronic system for collecting and sorting information about the size of light and dark patches on a plate. Preliminary experiments for measuring the size distribution of the islets of Langerhans in histologic sections of the pancreas are described.

Automatic Ultrasonic Inspection

INTEREST in ultrasonic methods of flaw detection has been increasing for some years, and a number of firms have been producing equip‐for the purpose. This equipment has usually, however, been confined to the necessary electronics and transducers, and where mechanization of its application has been desirable the necessary mechanisms have been built up on the site. Now, however, Kelvin &amp; Hughes Ltd. have introduced a range of ultrasonic testing equipment including the mechanical scanning devices. To this range the name Autosonics has been given. There are four main types of equipment, three of which arc illustrated in FIGS. 1–3. Not illustrated is what is called ‘sequence testing’, that is the application of components to a static probe in succession, as by a conveyor.