Beryllium Window Tube Research Articles

Mammography Equipment: Principles, Features, Selection

1. Three-phase and constant potential generators may offer advantages over single-phase generators. These include shorter exposure times with less chance for motion unsharpenss, more adequate exposure and possible lower dose, and longer tube life. 2. Control of tube voltage in increments of 1 kVp are desirable for screen-film mammography and 2 kVp for xeromammography. 3. Tube loading limitations should be capable of allowing an adequate mA and mAs output. A mammography unit with a lower mA output may require longer exposure times with consequent motion unsharpness and/or higher dose. The maximum mA output is limited by the power rating of the tube and not by the power rating of the generator, which is usually much higher. Thus, tube rating charts rather than generator power rating should be used to compare the mA output of different mammography units. 4. Phototimer capability can reduce exam time, facilitate proper exposure, and reduce radiation dose. Units with a greater number of density steps and three or more photocell locations, one of which is near the edge of the film holder, provide better phototimer results. 5. A molybdenum target, beryllium window tube with 0.03 mm molybdenum added filtration is presently preferred for screen-film mammography. A tungsten target tube with 1 to 2 mm added aluminum filtration is advised for xeromammography. 6. Effective local spot size for contact mammography should be in the range of 0.2 to 0.5 mm. However, high resolution also requires sufficiently long source-to-image-receptor distances. Using measured focal spot size and source-to-image-receptor distance, it has been shown that some mammography units do not fully utilize the resolution capabilities of some available screen-film systems. On the other hand, a focal spot that is too small may limit the field size and lead to uneven energy distribution in the x-ray field. 7. In order to perform standard and supplementary mammographic projections, the C arm assembly must be capable of being located at multiple positions within a 180 degrees rotation. Greater degrees of rotation are not required. 8. The heat dissipation capability should be adequate to accommodate the anticipated work-load in terms of number of patients and patient scheduling. A mammographic unit with an anode heat capacity of 90,000 heat units or more should be adequate for most practices. A mammography unit with a heat capacity of 20,000 heat units or less may require waiting time between exposures or studies in a high-volume mammography practice. 9. The compression plate should be made of plastic, usually 1 to 4 mm thick.(ABSTRACT TRUNCATED AT 400 WORDS)

Instrumentation for the Measurement of High Energy Phenomena on NASA Spacecraft

High energy astrophysical observations supported by the National Aeronautics and Space Administration will be conducted primarily from the Small Astronomy Satellites (SAS) and the High Energy Astronomy Observatories (HEAO). At the present time, three Small Astronomy Satellites have been approved for flight. The first (SAS A) will carry a set of collimated proportional counters to conduct a high sensitivity, high spatial resolution, all sky survey for X-ray sources, to search for temporal variations in the source intensity, and to measure the spectral distribution of sources in the energy range 1 to 20 keV. The spacecraft will carry two collimator systems of 1 by 10 deg and 10 by 10 deg fullwidth. The proportional counters are gas-filled beryllium window tubes. SAS A is planned for launch in late 1970.

Skin doses from glass and beryllium window x-ray tubes in mammography.

The radiation doses delivered to the skin during mammography may range from less than 2 rads to about 23 rads per film exposure, depending upon several exposure factors of the technic employed. In this study of the Egan technic (1), which utilizes industrial type M film, radiation doses to the skin were determined for both glass and beryllium window x-ray tubes. Of particular interest was the effect of added filtration upon the radiation dose delivered by the beryllium window tube. Earlier measurements of dose from glass window tubes (2, 3) are presented for comparison. Measurements Radiation measurements were made in air with a Victoreen end-window condenser chamber. In calculating absorbed dose, a factor of 0.92 rad per roentgen was used. The back-scatter factors employed were 1.08 for the craniocaudad and mediolateral projections, and 1.12 for the axillary projection. These measured back-scatter factors are somewhat lower than other published values (4) and if in error would require that all doses pres...

New instrumentation for cerebral microangiography.

Routine medical radiographie technics allow the resolution of objects 300 microns in size. The maximum resolution of this order, possible with modern angiographic equipment, permits the visualization of second or third order branches of the major intracranial vessels. The smaller leptomeningeal and the perforating vessels cannot be demonstrated by these means. Microvasculature (perforating vessels and capillaries) can be displayed radio-graphically in vitro with high-resolution photographic plates. The thinly sliced specimen, previously prepared by injection with radiopaque contrast material, is placed over the plate, and the plate is exposed to low-kilo voltage (10–30 kv) radiation, using a beryllium window tube. The relatively long exposure times necessary with the insensitive (ASA 0.0025) high-resolution plates make in vivo display of the microvasculature impossible (1–3). It is our purpose to describe an all-electronic system of radiography2 that permits the display of perforating arterioles in vivo (4–5). Method The radiographic equipment employs an x-ray sensitive Vidicon tube. This tube consists of a semiconductor which responds to incident x-rays by changes in electrical conductivity. The semiconductor employed is a vapor-deposited 30-micron-thick amorphous selenium layer. The semiconductor is applied to a conductive layer connected to the electrode near the face of the beryllium window Vidicon tube. A beryllium window x-ray source is used. The Vidicon tube is combined with television amplifying transmission and display systems. The image area of the standard 1-in. Vidicon tube is 3/8 by 1/2 in. If the transmitted signal is viewed on a 17-in. television monitor a 30-to-l magnification may be obtained. If the number of scanning lines in the television system is 525 (the standard for commercial television in the United States), a scan density of 1,400 lines per inch is achieved with a resultant resolution of better than 10 microns. Movement that is not blurred if filmed at 30 frames/second may be studied by this system. The image may be viewed directly on the television monitor or stored by a commercial television tape system. Approximately 5 mR to 0.5 R is needed per exposure. For this study, male adult albino rats were employed. The aorta was cannulated and a colloidal barium suspension was injected. The flow of barium through the macro-and microvasculature of the brain was observed. Fixed injected brain specimens were observed for detail, and vessels of 20 microns diameter were quite discernible on the television monitor (Figs. 1, 2). Summary An electronic system for the in vivo display of microvasculature is described. The system permits the study of vessels 10 microns in diameter. This range of vessel visualization has previously been unobtainable by standard angiographic technics in man or experimental animals.

Absorbed Dose Determination for X-rays in the Grenz-ray Region (5 to 20 keV Quantum Energy)

Determination of the absorbed dose for very low-energy X-rays is greatly simplified by the absence of scattered radiation. Absorber thickness can be scaled from one material to another by use of a relative effective density, which is the ratio of the mass energy absorption coefficients. Depth dose functions can be transferred from one material to another and from one FSD to another, and can be corrected for changes in air absorption. Exposure in roentgens can be measured directly with a suitable extrapolation chamber. The Fricke ferrous sulphate dosemeter is readily applicable, and a value of G = 14·8 was found for a 50 kvp unfiltered X-ray beam from a beryllium-window tube. It is concluded that the properties of very low-energy X-rays do not necessarily add to the uncertainties inherent in all X-ray absorbed-dose determinations.

THE SELECTION OF OPTIMUM MAMMOGRAPHY TECHNIC.

To be of utmost value to the radiologist, a roentgenogram of the breast should clearly demonstrate both tiny calcific deposits and fine soft-tissue structures in fat. This requires far greater resolution than most other x-ray examinations, because calcific specks 0.5 mm. and smaller are common, as are soft-tissue fibrils 2 mm. and less in diameter. Roentgenographic images must hence be extremely sharp. In addition, high-contrast technic is required, especially to highlight images of fine soft-tissue structures which are otherwise only marginally detectable. The two technics in widespread use were developed empirically (1, 2). More recently, our previous paper attempted to provide a basis of greater precision for designing and evaluating technics (3). Further investigation, however, has been required to accomplish this goal, along the following lines: (a) More extensive studies below 30 kvp (b) Tests with a beryllium-window tube (c) The effect of patient motion; estimate of permissible amplitude (d) Film development and equipment problems. This communication presents the results of recent studies of these questions, with the object of helping to determine the basis for selecting an optimum technic. Our approach is as follows: Part I. Discussion of the technical factors Part II. Experimental measurements Part III. Discussion and practical conclusions. Part I: Discussion of Technical Factors Table I lists several technical factors important in mammography. Analysis of the effect of each is made difficult by their large number and interdependence. Hence it is convenient to consider them in three separate groups. The first (marked with a dagger in Table I) includes general considerations common to all exposure technics. The second involves geometric considerations. The factors in both of these groups can be treated in a rather straightforward way, and their effects readily evaluated with a minimum of experimental work. They are considered below. The remaining factors relate to beam quality, film choice, and permissible patient motion. They are considered in Part II. General Considerations Common to all Technics 1. Viewing of roentgenograms: Roentgenographic contrast increases roughly in proportion to the density to which the film is exposed (Fig .1). For this reason, mammograms are best overexposed by ordinary standards. This procedure incidentally yields maximum information regarding internal and chest wall areas. The use of an adjustable high-intensity viewbox of the industrial type is advised, to penetrate dark areas on the film. In addition, it is important to mask out glare from the brighter chest wall portion of the roentgenogram. 2. Film Development4: The recommended time is five minutes at 68° F. for no-screen and AA-industrial films, while eight minutes are helpful in speeding up M-industrial film.

Conventional building materials as protective radiation barriers.

The assumtion is often made in x-ray protection planning that conventional building materials provide no shielding. The exception is concrete which, due to wide use, is accepted by everyone as a satisfactory shield. It is not at all unusual to encounter instances where any material other than lead or concrete is considered unacceptable for wall construction without the addition of a very thin sheet of lead. All materials provide some protection, however, and it would seem advisable to take this fact into consideration in shielding calculations. Some types of construction involve materials of a heterogeneous nature and the problem of calculating shielding data under such circumstances does not seem to be a simple one. The only solution apparent to us was actually to construct some typical wall sections and make transmission measurements. The x-ray source used in these investigations consisted of a resonant transformer operating at a nominal frequency of 1,200 cycles, and a grounded anode, beryllium window tube, capable of operation from 70 to 300 kvp at tube currents up to 20 ma. An electronic power source supplied the 1,200-cycle input to the high-voltage transformer. Both kilovoltage and tube current were electronically stabilized and monitored with 0.1 per cent potentiometers having 0.05 per cent reproducibility. Radiation measurements were taken at 70 to 300 kvp, with 0.5 mm. of aluminum filtration up to and including 125 kvp and with 3.0 mm. of aluminum at higher kilovoltages. The filtration was selected to be consistent with that used in connection with the lead attenuation curves in National Bureau of Standards Handbook 60, Fig. 3, page 35. The x-ray unit was provided with a diaphragm which could be adjusted for square or rectangular fields. This diaphragm with its associated light-beam localizer was used to set the field at the front surface of the wall sections. Transmission measurements were made with the smallest practicable ionization chambers better to resolve small holes in the wall sections. All dose rate measurements greater than 1 milliroentgen per minute were taken with a Victoreen 25-r thimble chamber modified and connected as shown in Figure 1. For a few of the measurements at low kilovoltage, a 100-c.c. chamber was used. Comparison of the two chambers showed good agreement, both behind the wall sections and in the unattenuated beam. Ionization currents were read with a null system with a 0.1 per cent potentiometer and a d.c. amplifier as a null detector. The system was calibrated against a Victoreen r meter at dose rates sufficiently high to allow intercomparison. The Victoreen r meter had been calibrated at the National Bureau of Standards. In order to provide data on structures conforming as nearly as possible to that which would be found in actual construction, several trade organizations were asked to provide samples of what they considered to be typical walls.

Absorption Analysis of X-Ray Spectra Produced by Beryllium Window Tubes Operated at 20 to 50 Kvp

It has been shown that absorption analysis can be employed to determine the spectrum of an x-ray beam containing characteristic x-ray lines superimposed on the continuous spectrum. In order to analyze such beams it is necessary to collect absorption data on a second tube, identical to the first except for target material, and operated at the same voltage and current. The method was used to determine the spectra of four different x-ray tubes operated at three different voltages. It was found that the continuous spectrum could be represented by a simple function containing only two constants. One of the constants proved to be independent of tube target material and applied voltage; the other, a function of voltage only. The integrated intensity of the continuous radiation was found to vary directly as the atomic number of the tube target and the square of the voltage applied.

The inherent filtration of x-ray tubes.

As many recommendations on radiation protection mention the total filtration demanded in diagnostic radiology, there is a growing interest in a relatively simple method for evaluating the inherent filtration of the x-ray tube. With this knowledge, it is possible to add extra filters to arrive at the prescribed total filtration. When considering the inherent filtration equivalent of x-ray tubes, one must bear in mind the fact that this inherent filtration depends on the tube voltage and the wave form. Further, one can think of the inherent filtration equivalent with respect to the absorption of the x-rays (1) or with respect to their resulting quality, characterized by the half-value layer expressed in terms of the equivalent filter material. Trout and his associates (2) published a simple experimental method for determining the inherent filtration of diagnostic x-ray tubes. A satisfactory value, they stated, can be obtained by determining the half-value layer of the unfiltered beam and relating this to the thickness of aluminum, for instance, which must be added to a beryllium-window tube to produce the same half-value layer under similar conditions. These workers published a number of curves with the half-value layer plotted against inherent filtration aluminum equivalent, with the tube voltage (kvp) as a parameter. No mention was made, however, of the wave form. Actually, according to a personal communication from Mr. Trout, the wave form used was “full-wave” rectified and as close to a sine-wave as one ever sees on diagnostic equipment. We made some similar measurements, for which we used a constant potential wave form. Our curves are shown in Figure 1, along with the curves published by Trout et al. (broken lines) for corresponding tube voltages and full-wave rectified wave form. To check the above method we measured the quality of the radiation from a diagnostic x-ray tube for two wave forms, viz. constant potential and full-wave rectified. The results are given in Table I. With the aid of a cut-away tube unit we also measured the inherent filtration equivalent with respect to the absorbing properties as a function of the tube voltage for constant potential. These results are given in Table II. Conclusions 1. For a given voltage the radiation quality of an x-ray beam, expressed in mm. Al h.v.l., depends strongly on the wave form. 2. There is relatively a great difference in inherent filtration equivalent depending on whether one considers this with respect to adsorption of the x-rays or to radiation quality. 3. For the determination of the inherent filtration equivalent with respect to the radiation quality, one can make use of the set of curves as shown in Figure 1.

Microradiographic techniques for study for emphysema.

The difficulties encountered in studying the macro-anatomy of emphysema are somewhat similar to those that would be encountered in studying the holes of three-dimensional doughnuts with most of the doughnut gone. If the walls of a hollow three-dimensional polygon were intact, one might reasonably expect to reconstruct an image of its size and shape through study of serial sections. In emphysema, however, not only have many of the wall sections partially or totally disappeared, but many of the anchoring corner angles have either been distorted out of recognition or ruptured or retracted. If the difficulties of dealing with tissue almost as fragile as cobwebs are added to this, it is understandable why the anatomy of emphysema has been difficult. Taking advantage of newly developed beryllium-window X-ray tubes and of dryinflation fixation of lungs, we studied 146 lungs in the following manner:

Effects of concomitant superficial x-radiation upon the lethal effectiveness of 250-kvp x-rays.

A consistent and as yet inadequately solved problem of radiation dosimetry is that of predicting the biological effect of ionizing radiation in a system wherein a homogeneous dose distribution has not been achieved. Various compromise dose measurements such as the exit dose (1, 2) or the midline tissue dose (3) have been applied and have been shown to be of only limited usefulness. For the end-point of lethality in mammals the dose which probably reflects the biological damage most directly is that which is absorbed within bone marrow. If this is true, radiation not capable of penetrating the shielding bony structures cannot accomplish biological damage that would contribute to acute lethality. It was the purpose of the study to be reported here to test the foregoing hypothesis by concomitant administration of a massive dose of soft x-rays and 250-kv x-irradiation, and simultaneously to determine the lethal dose for the 250-kvp x-rays. Methods Mongrel male dogs weighing initially 8 to 12 kg. were used in all experiments. Prior to radiation exposure they were kept in isolated receiving runs for a minimum two-week quarantine period. During this interval they were dewormed and immunized against distemper and hepatitis. They were then transferred to individual cages in a controlled-environment animal room for one week before exposure and carefully observed for signs of ill health. They were weighed daily prior to and after exposure. Lethality was accounted for forty-five days following exposure. Animals were randomly assigned to treatment groups. They were irradiated under light pentobarbital anesthesia while held suspended in canvas slings. Combined exposure animals received either 1,000 r or 3,000 r in air of 50-kvp radiation. The 50-kvp source was a Picker “Zephyr” x-ray unit equipped with a Machlett OEG-50 beryllium-window tube. Operation was at 50 kvp, 40 ma, with a 0.25-mm. aluminum filter. Under these conditions the initial h.v.l. was 0.16 mm. Al. The animals were reversed midway in the exposure interval to accomplish bilateral exposure. The distance from the target to the animal's midline was 115 cm. Under these conditions the dose rate, in air, measured at the midline distance of the dog, was 48 r/minute. Measurements of dose rates, in air, for the low-energy source were made with a Victoreen condenser r-meter. The chamber used was a factory-calibrated thin nylon wall type. The 250-kvp exposures were made with a General Electric 250-kvp Maxitron operated at 25 ma. No filtration was added, but inherent tube filtration in this machine as used by us is relatively heavy. The initial h.v.l. in copper is 1.8 mm. The ultimate h.v.l. is 2.7 mm. The dose rate to the potential midline of the dog at 115 cm. from the target was 11.8 r/min. Dose rate measurements were made with a Bureau of Standards calibrated Victoreen condenser r-meter and 25-r thimble. Depth dose measurements were made in both water and tissue-equivalent wax phantoms.

Emission Spectrum of N2O+

IN the course of a study of the luminescence of gases irradiated by X-rays (to be published), some unknown bands were observed from nitrous oxide. All the other gases studied emit well-known band systems, usually of the parent gas or its ion. Gases at pressures between 1 and 700 mm. were irradiated with soft X-rays (45 kV. peak) from a beryllium-window tube, and the spectra photographed or scanned with a photomultiplier through a Hilger D.96 f 2 quartz spectrograph. The emission from nitrous oxide consisted of the unknown bands at about 3680, 3540 and 3380 A. and the nitric oxide β system (the bands in the ν′ = 0 progression between ν″ = 3 and 13 were observed). The latter system has been observed previously as fluorescence from nitrous oxide irradiated with vacuum ultra-violet light1. The two sets of bands differ in their dependence on pressure; the β bands suffer little collisional deactivation at high pressures whereas the new bands are strongly ‘quenched’, but they must be much more strongly excited since the intensities are roughly comparable at 600 mm. Since carbon dioxide excited by X-rays emits CO2+ bands (2∑u − 2Πg, ref. 2, and 2Πu − 2Πg, ref. 3) and these show a similar pressure dependence, the new bands are tentatively ascribed to N2O+. Emission by nitrous oxide (N2O) itself is unlikely from a consideration of its excited states4.

Radiation polymerization of liquids.

Radiation polymerization appears to offer interesting possibilities for studying certain aspects of the interaction between radiation and matter. In preliminary studies to be described below, x-rays generated in a 250-kv beryllium window tube and filtered by various thicknesses of copper have been used. Several liquids were considered. Only one was found to be suitable for extensive study. This substance is sensitive to both visible and x-radiation but when kept in the dark is stable for many months. Each specimen of liquid was contained in a 1.5-c.c. gelatin capsule with a lead ball about one-half the diameter of the capsule. The lead ball served as a means of testing for the presence and quantitative extent of solidification. The capsules were irradiated with the longitudinal axis parallel to the direction of and in a small circle concentric with the center of the beam. Uniformity of irradiation of a group of capsules partially embedded in a small block of plastic foam was insured by rotation of the circle of capsules about the central axis of the beam. The extent of polymerization within the capsule was in accordance with variations of x-ray intensity along the longitudinal axis due to inverse-square and absorption effects. Solidification occurs initially at the upper end of the capsule but, for higher voltages, not at the upper surface because of absence of electron equilibrium there. Inversion of the capsule permitted the lead ball, originally at the bottom, to fall through unsolidified liquid to the level of solid polymer. Numerical data were obtained by measuring the distance from the meniscus of the solid polymer to the final position of the ball. After an irradiation, the maximum difference in extent of polymerization among the capsules corresponded to 4 per cent of the total dose. The sensitivity of the monomer varied inversely with the intensity and appeared to be an inverse exponential function of the energy. After irradiation ceased, the rate of polymerization appeared to decrease exponentially, so that the amount of polymerization asymptotically approached the final value in about thirty minutes. The intensity of the incident beam determined the amount of “after-polymerization.” The experimental evidence reported above indicates that the mechanism of action is through the formation of long lived radicals which form macro-molecules.

A Study of the Inherent Filtration of Diagnostic X-Ray Tubes

The use of added filtration in diagnostic technics and the variation of inherent filtration in different types of diagnostic tubes has brought about the need for a simple procedure for determining the aluminum equivalent of the inherent filtration of the x-ray tube. Once the inherent filtration equivalent is determined, additional filter can be added to arrive at any desired total filtration. Since there will be differences in the inherent filtration of tubes of the same type and variation in the thickness of the added filters due to commercial tolerances, the accuracy of the measurement of the inherent filtration need not be of a high order. A measurement of the half-value layer of the beam from the x-ray tube without added filter would seem to be a useful and sufficiently accurate means of determining the inherent filtration. With the aid of better low-energy instrumentation than previously available in our laboratory, and of beryllium window tubes, measurements have been made to relate, inherent filtration to half-value layer. For further relating the experimental data to the actual components going to make up the inherent filtration (glass, oil, Bakelite), a cutaway tube unit of typical component thicknesses was constructed. An x-ray beam having low filtration (2 mm. Be) was directed through each of the elements and through the assembly to determine their influence on the resulting total filtration. Glass was found to have a transmission of 6 per cent at 80 kvp, which was reduced to 5 per cent by the addition of oil and Bakelite. From this it is evident that the glass window of the tube accounts for most of the inherent filtration. When the beam from the 2-mm. beryllium window was filtered by directing it through the cutaway tube assembly, the half-value layer and the aluminum filtration necessary to obtain the same half-value layer at 80 kvp were: h.v.l. 0.90 mm. Al, aluminum equivalent 0.87 mm. Al. There was no significant change in the aluminum equivalent of the cutaway tube unit from 50 to 100 kvp. All this leads to the assumption that a satisfactory value for the inherent filtration of a diagnostic tube unit can be obtained by determining the half-value layer of the unfiltered beam from the tube unit and relating this to the thickness of aluminum which must be added to a beryllium window to produce the same half-value layer under similar conditions.

Spectral Dose-Rate Distribution in the X-Ray Beam from a Beryllium Window Tube Operated at 50 KVP

Knowledge of the quality of the X-ray beam from a beryllium window tube operated at low kilovoltages is of interest both to the clinical radiologist, who uses such beams for superficial therapy, and to the scientist who may wish to take advantage of either the high intensity or long wavelengths of such beams. The spectral doserate distribution in the X-ray beam can be computed from the filtration data by a method using Laplace transforms (1). The results of such computations for the X-ray beam from a beryllium window tube operated at 50 kvp are given in this paper. EXPERIMENTAL METHOD

X-rays in philately.

As is well known, radiography provides a means for non-destructive analysis in many fields outside of medicine and medical research. Perhaps the industrial applications have received the most publicity, but x-rays have been similarly employed in such fields as archaeology, paleontology, geology, biology, conchology, zoology, and entomology. One of the best known non-medical and non-industrial uses of radiography is in art museums, where paintings are examined for analysis of the paint, canvas, paper, or wood base. Quite recently similar investigations have been made in the field of philately, or stamp collecting. A postage stamp consists basically of a design printed on a small piece of thin paper. It is important to the collector to be able to differentiate various characteristics of stamps. These include: (1) the method of printing, such as intaglio, letterpress, offset, photogravure, or other process; (2) the type of paper—woven, laid, ribbed, pelure, etc.; (3) watermark, if any, in the paper. Such information is essential in cataloguing stamps for collections or sales. Many stamps are of high value, selling for hundreds and even thousands of dollars if in good condition and genuine. Years ago clever counterfeiters created reproductions of quite a few of these high-value stamps. Nowadays the unscrupulous artisan will not forge an entire stamp, but he is able to increase the value of a genuine stamp by repairing torn or thin areas of the paper, adding paper to narrow margins (Fig. 1), replacing perforations that have been torn off, and chemically removing cancellations. He also will redraw the design where damaged (Fig. 2). Such repairs frequently are impossible of detection by the naked eye, the microscope or ultraviolet light. Hence, such alterations may be overlooked even by the advanced philatelist. The application of x-rays has made it possible to study the minute details of the design, paper texture, watermark, and cancellation of the postage stamp. One can facilitate determination of authenticity by comparing the radiographic image of a genuine with that of a questionable stamp. Repaired areas will usually show as clearly on the radiograph as would a fracture of a long bone. Such analysis is made possible by the use of three different technics: low-voltage radiography, autoelectronography, and electronography. Each procedure reveals certain aspects of the stamp not readily apparent with the others. Technics Low-Voltage Radiography: Because postage stamps are printed on such thin paper and offer so little absorption, x-rays of very long wave length must be employed. We have found that a beryllium window tube operated at 6 kv. is most satisfactory. The designs and cancellations of stamps are printed with inks whose color is derived from metallic pigments such as mercuric oxide, lead oxide, etc., or from organic substances such as carbon and the aniline dyes.

Corrigenda

CorrigendaPublished Online:28 Jan 2014https://doi.org/10.1259/0007-1285-26-306-325SectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail AboutAbstractIn the paper entitled “A Theoretical Study of Radiation Outputs and Qualities from a Beryllium Window Tube Operated at Low Kilovoltages (10–50 kVp)” by W. A. Jennings, Brit. Journ. Rad., 1953, xxvi, 193–206, the following corrections should be made:1. In Table I, p. 194, every figure in the column headed “Air” is too large by a factor of 8. The printed data are values of μt, where t=8 cm, and not of μ itself.2. The specific gravity of Al is given as 2·07, which should be 2·70.3. In the first expression on p. 194, “σ2” should read “σαa”.Neither of the latter errors affects any of the published data. Previous article Next article FiguresReferencesRelatedDetails Volume 26, Issue 306June 1953Pages: 273-328 © The British Institute of Radiology History Published onlineJanuary 28,2014 Metrics Download PDF

A theoretical study of radiation outputs and qualities from a beryllium window tube operated at low kilovoltages (10-50 kVp).

An attempt is made to apply some theoretical data regarding continuous X-ray spectra, due to H. A. Kramer, to the conditions obtaining in the use of low kilovoltage beryllium window tubes. Thus, after introducing the appropriate absorption coefficients, transmitted spectral dose rate distributions are computed for selected absorbers (beryllium, aluminium and air thicknesses). Thence, relative outputs and qualities relating to constant potential generation are derived by graphical integration. These results are then extended to pulsating tension units by applying the data to the actual kV and tube current waveforms to which the experimental equipment used by the writer is subject. By this means dose rate waveforms are obtained and their relative areas provide the relative outputs under pulsating tension which can be compared with the corresponding experimental data previously published. From a consideration of relative quality data, a correction for the self-hardening effect of the cathode beam target-penetration is made in terms of an equivalent filtration. The dependence of output on tube current, and air absorption losses are also analysed. The ranges considered are (1) 10 to 50 kVp; (2) 0 to 2 mm Al external filtration (1 mm Be. inherent filtration); (3) 2·5 to 50 mA tube current; (4) 10 to 50 cm F.S.D.

Correspondence

In the above letter, Mr. Heasman points to the change in effective atomic number of the phantom material known as Mixture D at a wave length of 2·5A, and refers to measurements made with a beryllium-window tube operated at kilovoltages below 50 kVp.

Beryllium-window tube outputs; further considerations regarding the use of constant and pulsating tension.

Beryllium-window tube outputs; further considerations regarding the use of constant and pulsating tension.