Radiographic techniques

W. L. Bloom, J. L. HoUenbach, and J. A. Morgan, Medical Radiographic Technique, Charles C. Thomas Publishing, Springfield, lU., 1965. 

Both ultrasonic and radiographic techniques have shown appHcations which ate useful in determining residual stresses (27,28,33,34). Ultrasonic techniques use the acoustoelastic effect where the ultrasonic wave velocity changes with stress. The x-ray diffraction (xrd) method uses Bragg s law of diffraction of crystallographic planes to experimentally determine the strain in a material. The result is used to calculate the stress. As of this writing, whereas xrd equipment has been developed to where the technique may be conveniently appHed in the field, convenient ultrasonic stress measurement equipment has not. This latter technique has shown an abiHty to differentiate between stress reHeved and nonstress reHeved welds in laboratory experiments. 

Stress-corrosion cracks tend to be fine, tight, and easily overlooked. Various nondestructive techniques are available to aid in the discovery of cracks, such as dye penetrant, and ultrasonic and radiographic techniques. 

There are several schemes for nondestructive evaluation. Changes in electrical resistance can be used to follow corrosion. Radiographic techniques involving X-rays and gamma rays have been applied. Transmitted radiation as well as back scattered radiation have been used. 

Cook (Ref 2) devotes Chapter 9 to a discussion of compressive elastic props of solids under expl attack. Modern applications of expls involve the compressibility of solids under extremely high pressures. Walsh et al (Ref 1) reported the equations of state of 27 metals under shock compression. Schall Thomer (Ref 3) measured the shock compressibility of Mg-Al alloy, Lucite polyethylene by flash radiographic techniques... 

The study of shaped charge and high velocity jets involves investigations in a variety of scientific fields. These include the physics of plasticity of metals at very high strain rates the physics of interactions between metals and HE s and the field of instrumentation design for highly specialized applications. Included are multiple flash radiographic techniques which produce... 

Radiology Laxatives are used to clean the gastrointestinal tract before radiographic techniques are performed. 

Fig. 4.8 Regions of different flow behavior in two-dimensional hoppers as observed by radiographic techniques. [Reprinted by permission from J. Lee et al., Trans. Soc. Rheol., 18, 247 (1974).]...

Localized malignant mesotheliomas occur > and show the same histologic and immunohistochemical features of diffuse malignant mesotheliomas. However, mesotheliomas may be diffuse and beyond the resolution of current radiographic techniques (e.g., computed tomography and magnetic resonance imaging) and initially appear as localized. 

Laxatives are used to hasten the elimination and reduce the absorption of a poison that has been taken. Laxatives are used before and after treatment with antihehnintic drugs. Laxatives are used to clean the gastrointestinal tract before radiographic techniques are performed. 

In other studies, Edwards (248), Fairchild, Tonna, and Seibold (257, 258) and Frigero (293) have employed activation analysis low-background radiographic techniques to measure the boron distribution within cells in order to use Boron-10 in clinical trials of an experimental therapuetic procedure, that is, neutron capture therapy. These particular cellular distribution studies were carried out on mouse spleen, and, after the activation, the materials were exposed to photographic nuclear track emulsions of Eastman Kodak Type NTA. The countable a-particle tracks obtained in these experiments showed that concentrations of B-10 of 60 Mg/gm, the amount that can be safely delivered to tumors in human subjects, could be readily determined. In other applications of activation analysis and autoradiography, Vincent (963) and Vincent, Haumont and Roels (964) made microscopic determinations of sodium in compact bone and of bone phosphorus. 

Chamley and coworkers first developed radiographic techniques for evaluating the wear rate of UHMWPE acetabular components in patients. In 1973, Chamley and Cupic reported on the long-term wear performance in the first cohort of patients to receive a UHMWPE component between November 1962 and December 1963. During this time period, 170 patients received a cemented LFA with an UHMWPE component a total of 185 acetabular cups were implanted. Because of the elderly population originally implanted with the components, many had died or were too infirm to travel to the clinic for followup examination (more than two-thirds of the patients were older than 60 years of age at the time of implantation). Thus, only 106 out of the original 185 UHMWPE cups could still be evaluated after 9 or 10 years of implantation. The complications for this series included a 4-6% rate of infection, 1-2% rate of mechanical loosening, and a 2% incidence of late dislocation. 

Although knee arthroplasty enjoys a remarkable clinical track record, problems with wear and fatigue damage of UHMWPE continue to limit the longevity of both unicondylar and bicondylar knee replacement components. Unlike in the hip, where radiographic techniques have been developed to quantify in vivo wear rates, there currently exist no standard and widely accepted techniques for tracking the clinical performance of UHMWPE in patients with knee replacement. Thus, today the most effective way to evaluate the in vivo performance of UHMWPE continues to be the analysis of retrieved components from revision surgery or from autopsy donations. 

Although fluoroscope-assisted or computer-assisted radiographic techniques are widely employed among the orthopedic community, ultrasoimd... 

All of the in vivo wear measurement techniques described in this section related to TKA have certain drawbacks and unique limitations. Certainly all of these methods are predicated on the presence of a metallic tibial baseplate. In this respect, radiographic wear assessment in the hip and the knee share a common limitation, although the inclusion of a radiographic wire marker in all-UHMWPE cups has somewhat alleviated this concern. In addition, from a practical perspective, both fluoroscope-assisted or computer-assisted radiographic techniques for TKA are more cumbersome and nonstandard than the methods used to obtain radiographs for routine clinical diagnosis. Ultrasound as a wear measurement technique for TKA is in its infancy, insofar as widespread acceptance is concerned. Finally, the absolute accuracy of these in vivo wear... 

One of the most convenient methods for determining the numbers of dust particles on a substrate before and after an experiment is the use of tracer atoms. Any proportionality between the number of particles on the substrate and the number of pulses measured in a counter can only be found for more or less monodisperse particles it is impossible to draw any conclusion as to the size distribution of particles in a polydisperse dust. Either counters or a radiographic technique may be used in determining the number of active particles. 

Examinations will include liquid penetrant or magnetic particle techniques when surface examination is specified, ultrasonic or radiographic techniques when volumetric examination is specified, and visual inspection techniques will be used to determine surface condition of components and for evidence of leakage. Specific techniques, procedures and equipment, including any special techniques or equipment will be in accordance with the requirements of IWA-22 00 of ASME Section XI and will be defined in the in-service inspection program. 

Good radiographic technique depends heavily on patient preparation and the relationship formed between the radiographer, the child and their carers. 

The flash X-ray radiographic technique used for the determination of the detonation wave parameters is based on time-dependent tracing of the position of thin metal foils moving together with detonation products behind the detonation wave front at the same velocity. Therefore, viewing the movement of the foils, one obtains the velocity of detonation products behind the detonation wave front, i.e., their mass velocity (Chick et al., 1985 Dorokhin et al., 1988 Huiling et al, 1985 Trimble et al, 1981). On the basis of that velocity, other detonation parameters can be calculated. 

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