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PubMed1972

The videorecord: new mode for learning.

The successful delivery of health care involves a commitment to improved communication both with regard to health professionals and the public. The need for innovative educational patterns is implicit in the recommendations of the latest Carnegie Commission Report, Higher Education and the Nation's Health. The new technology of videorecording permits the learner to learn at a time and place of his own choosing. Information is transmitted through the cathode ray tube-a television set-the medium of our time. The videorecord is of significant value in the basic and clinical sciences, in training personnel for allied health professions, and in continuing education. It is thoroughly compatible with the new concept of the open university, an institution without walls. In addition to its unquestioned value in educational programs in the health sciences, the videorecord has major implications for the curriculum in librarianship and for increasing the professional competence of medical librarians and their ancillaries. The medical librarian has a major stake in its imaginative use for overcoming some of the barriers to individual and community health.

Allied Health Personnel↗
PubMed2002

Macroradiography using conventional radiographic X-ray equipment.

Macroradiography is a radiographic imaging technique used to increase the size of the image relative to that of the object. Macroradiographic images suffer degradation due mainly to geometric unsharpness (U(g)). U(g) results from the finite size of the focal spot of the X-ray tube. Specialized equipment with a small effective focal spot size (Eff FSS) is generally used to perform macroradiography. The specialized nature of the equipment means macroradiographic examinations are not commonly undertaken. Macroradiographic examinations can also be performed on conventional radiographic equipment because the Eff FSS varies in the X-ray beam along the cathode-anode axis. Calculations and measurements of FSSs at different positions along the cathode-anode direction of the X-ray beam have been made. A simple technique of angling the X-ray tube 10 degrees towards the cathode reduces the Eff FSS in one dimension while still maintaining a vertical central ray. Reduced beam coverage results from this technique and an increase in radiographic exposure is required to compensate for the anode heel effect. Macroradiographic images of line pair phantoms and a hand-wrist phantom, at various tube angles, have been obtained to compare image detail.

Mathematics↗
PubMed2000

"Anode heel effect" on patient dose in lumbar spine radiography.

Appropriate use of the "anode heel effect" of the output beam from an X-ray tube can reduce the effective dose to patients in some common radiological examinations. We investigated the variation in radiation intensity across the X-ray beam caused by the anode heel effect, and quantified the difference in absorbed dose to critical organs resulting from lumbar spine X-ray projections carried out with the two possible orientations of the patient along the tube axis (cathode to anode). A Rando phantom and some high sensitivity thermoluminescent dosemeters (TLDs) (LiF:Mg,Cu,P) were used. With the tube axis horizontal, radiation intensity profiles, parallel and perpendicular to the axis, were measured. Lumbar spine radiographs were recorded using the Rando phantom in the standard anteroposterior (AP) and lateral projections. TLD pellets were used to measure the absorbed radiation dose at various sites corresponding to critical organ tissues (ovaries, testes, breasts, thyroid and lens). Each set of projections was recorded in two phantom orientations, first with the phantom head placed towards the cathode end of the X-ray tube, and then in the reverse direction. From the radiation intensity profile of the incident X-ray beam, the "cathode end" to "anode end" air dose ratio was found to be 1.8. In lumbar spine radiography, with the phantom head placed towards the anode end of the X-ray tube, the ovaries and testes received an average dose 17% and 12% higher, respectively, in the lateral projection, and 16% and 27% higher, respectively, in the AP projection, than those obtained in the reverse "patient" orientation. These results indicate that patients (particularly females) should always be positioned with the head placed towards the cathode end of the X-ray tube for lumbar spine radiography to achieve significant dose reductions.

Breast↗
PubMed1995

X rays in diagnostic radiology.

An overview of the technical developments in and growth of the diagnostic use of x rays over the century since their discovery is presented. The major developments described include the introduction of the hot cathode x-ray tube, the Potter-Bucky grid, the image intensifier, the computerized tomographic scanner, and the adoption of the digital computer for image processing, display, and storage. Other significant but smaller advances discussed include improved film/screen technology, the rotating anode tube, linear tomography, and some recent advances in image receptors.

Angiography↗
PubMed2001

Since 1895, orthopaedic surgery relies on x-ray imaging: a historical overview from discovery to computed tomography.

The first application of x-ray techniques to human beings was made in Germany by Wilhelm Conrad Röntgen in November 1895. From this first use, different groups became interested in creating and improving the technical devices. Focusing on Germany, in honour of the centenary of the awarding of the first Nobel Prize in Physics to Röntgen in 1901, we present some of the milestones in x-ray imaging, from the first pioneer's approach on glass plates, cathode x-ray tubes, fluoroscopy, earlier communications leading to x-ray films and screens, rotating x-ray tubes, tomography and CT, classic textbooks, radioprotection aspects, as well as some contributions in radiological techniques and orthopedic pathology.

Equipment Design↗
PubMed2001

Since 1895, orthopaedic surgery needs X-ray imaging: a historical overview from discovery to computed tomography.

The first application of X-ray techniques to human beings was made in Germany by Wilhelm Conrad Röntgen in November 1895. From this first use, different groups became interested in creating and improving the technical devices. Focusing on Germany, in honour of the centenary of the awarding of the first Nobel Prize in Physics to Röntgen in 1901, we present some of the milestones in X-ray imaging, from the first pioneer's approach on glass plates, cathode X-ray tubes, fluoroscopy, earlier communications leading to X-ray films and screens, rotating xray tubes, tomography and CT, classic textbooks, radioprotection aspects, as well as some contributions in radiological techniques and orthopedic pathology.

History, 19th Century↗
PubMedDate not supplied

X-ray tubes.

The x-ray tube serves the function of creating x-ray photons from electric energy supplied by the x-ray generator. The process of creating the x-ray beam is very inefficient, with only 1% of the electric energy converted to x-ray photons and the remaining 99% converted to heat in the x-ray tube assembly. Thus, to produce sufficient x-ray output for diagnostic imaging, the x-ray tube must withstand and dissipate a substantial heat load, a requirement that affects the design and composition of the x-ray tube. The major x-ray tube components are the cathode and anode assemblies, the tube envelope, the rotor and stator (for rotating anode systems), and the tube housing. The design of the x-ray tube determines the basic characteristics of the x-ray beam such as focal spot size, x-ray field uniformity, and the x-ray energy spectrum. These x-ray beam characteristics are important because they affect radiologic parameters such as spatial resolution, image contrast, and patient dose.

Technology, Radiologic↗
PubMed1984

Proton-induced characteristic x-rays: a versatile source of ultrasoft x-rays for biological and biochemical investigations.

Very low energy ( ultrasoft ) x-rays of 0.3-5 keV have provided a unique tool for investigation of mechanisms of radiation action, especially with respect to the energy and spatial properties of critical radiation damage in mammalian cells. Experimental investigations to date have been partially limited by the availability and characteristics of suitable ultrasoft x-ray sources. The suitability of small electrostatic proton accelerators, such as exist in many laboratories, have been investigated as a means of producing a secondary beam of ultrasoft x-rays suitable for irradiation of biological and biochemical systems. Results are presented on the physical characteristic of carbon K (0.28 keV) and aluminium K (1.5 keV) ultrasoft x-ray beams produced by bombardment of solid targets of carbon and aluminium with protons of energies up to 750 kV and currents up to 500 microA. These characteristics are compared with those of a cold cathode discharge ultrasoft x-ray tube previously used for mammalian cell investigations. It is seen that the proton accelerator produces much more versatile beams of characteristic ultrasoft x-rays which greatly extend the scope for future experiments on mammalian cells, micro-organisms and biochemical systems. Nevertheless there are situations in which the cold-cathode discharge tube will remain the source of choice and there are other situations, requiring for example energies between characteristic lines, where the greatly more complex synchrotron radiation sources are required.

Animals↗
PubMedDate not supplied

Effective size of the transverse dimension of x-ray-tube focal spots.

Corrections for nonuniform x-ray intensity distributions have been computed for the dimension perpendicular to the anode-cathode axis of x-ray-tube focal spots. These correction factors were developed from comparison of OTFs for focal spots with uniform intensity distributions to those for focal spots with symmetric double-peaked intensity distributions.

Technology, Radiologic↗
PubMed2001

A truly hybrid interventional MR/X-ray system: feasibility demonstration.

A system enabling both x-ray fluoroscopy and MRI in a single exam, without requiring patient repositioning, would be a powerful tool for image-guided interventions. We studied the technical issues related to acquisition of x-ray images inside an open MRI system (GE Signa SP). The system includes a flat-panel x-ray detector (GE Medical Systems) placed under the patient bed, a fixed-anode x-ray tube overhead with the anode-cathode axis aligned with the main magnetic field and a high-frequency x-ray generator (Lunar Corp.). New challenges investigated related to: 1) deflection and defocusing of the electron beam of the x-ray tube; 2) proper functioning of the flat panel; 3) effects on B0 field homogeneity; and 4) additional RF noise in the MR images. We have acquired high-quality x-ray and MR images without repositioning the object using our hybrid system, which demonstrates the feasibility of this new configuration. Further work is required to ensure that the highest possible image quality is achieved with both MR and x-ray modalities.

Brain↗
PubMed1979

Notation of physical equations no longer a problem.

Physical quantities and equations are used to define the laws of natural and engineering sciences. Clarity has been brought in equal measure into the the theory of physical quantities and the SI-system of units due to the basic work of Wallot and that of national and international institutions. For practical use in this paper, the most important rules and definitions for the formulation of physical equations are treated in an elementary form and the ease of their use is demonstrated in the following examples: speed of a car, capacitance of a plate capacitor, thermal emission of the cathode of an x-ray tube, oxygen uptake in cardiology, mole concentration and mass concentration of a substance in a solution. In addition, some important quantities and units of cardiology were summarized in a table.

Cardiology↗
PubMed1989

Measurement of DNA damage and cell killing in Chinese hamster V79 cells irradiated with aluminum characteristic ultrasoft X rays.

Chinese hamster V79 cells were irradiated with 1.487 keV aluminum characteristic X rays produced using a cold-cathode discharge tube. Under aerobic conditions a relative biological effectiveness (RBE) of 2.18 for cell killing in comparison to 250-kVp X rays was measured using cells grown in suspension and irradiated on membrane filters. DNA damage in the form of single-strand (ssb) and double-strand breaks (dsb) was measured using the filter elution technique. The aerobic RBEs are 1.64 for dsb induction and 0.49 for ssb induction, consistent with the view that dsb are more closely related to cell kill than ssb. A reduced oxygen enhancement ratio (OER) for cell killing was measured for Al-K X rays, but the OER for dsb induction was similar to that measured for 250-kVp X rays. A curvilinear relationship between dsb induction and dose is observed, similar to that seen for 250-kVp X rays. This agrees with the concept that ultrasoft X rays produce critical lesions similar to hard X rays but with a greater efficiency per unit dose.

Animals↗
PubMed1994

Sub-kilohertz flash X-ray generator utilising a glass-enclosed cold-cathode triode.

The construction and fundamental studies are described for a sub-kilohertz X-ray generator for producing low-dose rate flash X-rays. The X-ray tube was a glass-enclosed cold-cathode triode, composed of a tungsten plate target, a rod-shaped graphite cathode, a mesh-type trigger electrode made of tungsten wires, and a glass tube body. The coaxial condenser was charged up to 60 kV by a power supply, and the electric charges in the condenser were discharged to the X-ray tube repetitively when a negative high-voltage pulse was applied to the trigger electrode. The maximum tube voltage before the discharging was equivalent to the initial charged voltage of the condenser, and the maximum tube current was about 0.3 kA with a charged voltage of 60 kV. The X-ray durations were about 1 microsecond, and the X-ray intensity was about 0.47 microC kg-1 at 0.5 m per pulse with a charged voltage of 60 kV. The maximum repetition rate of the X-rays was about 0.4 kHz, and high-speed radiography was performed.

Animals↗