PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “radiation shielding”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1975

[The radiation protection shield--a useful radiation protective device for stomatological routine radiodiagnosis].

Starting from the shortcomings of the radioprotective devices at present used in routine stomatological radiodiagnosis, the authors describe the advantages of a radioprotective shield which has been produced in the Greifswald University Stomatological Clinic. On the basis of dosimetric studies, the State Board for Nuclear Safety and Radiological Protection of the GDR (Staatliches Amt fur Atomsicherheit und Strahlenschutz der DDR) could demonstrate the suitability of this shield as a radioprotective device for routine stomatological radiodiagnosis.

Humans↗
PubMed2026

Shielding performance and clinical applicability of lead-free materials in computed tomography.

Owing to the high radiation exposure associated with computed tomography (CT) examinations and the image quality degradation caused by conventional radiation shielding materials, this study evaluated the dose reduction performance and image quality maintenance potential of a newly developed lead-free composite shielding material. This material was composed of bismuth, tungsten, tungsten carbide, aluminium, and polyurethane. Phantom-based dose measurements demonstrated that the shielding material achieved dose reduction rates ranging from 17.6% to 37.6%, depending on tube voltage. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and changes in tube current-time product (mAs) under a scout-based automatic exposure control (AEC) protocol were analysed according to the presence or absence of the shielding material across regions. For the clinical evaluation, CT scans were performed on four patients. Furthermore, the images were reviewed to evaluate whether this material affected image quality. The shielding material exhibited radiation reduction levels comparable to those reported in previous studies. SNR and CNR analyses showed minor statistical variations in certain regions; however, most differences were not statistically significant, and even significant differences remained within a range that did not compromise diagnostic image quality. Under the scout-based AEC protocol, the use of the shielding material resulted in less than 1% variation in mAs values. No visually perceptible artefacts or clinically significant image quality degradation were observed. The proposed composite shielding material demonstrated the potential to mitigate some limitations of conventional shielding materials and showed preliminary clinical feasibility as an adjunctive strategy for radiation dose reduction in CT examinations.

Radiation Protection↗
PubMed1979

Ventilation studies with krypton-81m.

Nuclear medicine offers well-established methods for regional lung function assessment in the preoperative evaluation of patients with lung disease. The perfusion study with Tc-99m macroaggregates is simple and can be performed without special precautions in radiation shielding. The ventilation study with Xe-133, however, requires more elaborate apparatus as well as special procedures to collect the exhaled radioactive rare gas. Nuclear medicine departments with access to short-lived radionuclides from a nearby cyclotron can use the krypton isotope Kr-81m. The physical half-life of Kr-81m is 13 s. Its gamma energy of 190 keV is optimal for gamma cameras. Kr-81m can be used as a medical isotope in spite of its short half-life. It can be eluted with a continuously flowing gas from the generator containing the mother nuclide Rb-81 which has half-life of 4.6 h. This short half-life not only simplifies radiation protection but allows repeated studies in different projections as well. Examples of comparative studies with Xe-133 and Kr-81m are presented. The importance of taking not only anterior and posterior pictures but also lateral oblique views is stressed.

Half-Life↗
PubMed1976

Intercomparison of myocardial imaging agents: 201Ti, 129Cs, 43K, and 81Rb.

Thallium-201, 129Cs, 43K, and 81Rb were evaluated as "static" myocardial-imaging agents. Optimal settings of the scintillation camera were determined for each agent. Accumulation for good-quality images can be started as early as 5 min after the dose with 43K, 10 min with 201T1, and 30 min with 129Cs. Imaging times were comparable for 43K, 129Cs, and 201T1 (using the 80-keV x-rays). High-energy photons from the 81Rb preparation, largely from 82mRb contaminant, made it impossible to obtain an interpretable image without the addition of more shielding. Absorbed radiation dose from 81Rb is lower than that from 43K, 129Cs, and 201T1. The highest background activity was observed with 81Rb, followed by 43K, 129Cs, and 201T1 in that order. Overall, 201T1 was best suited for imaging acute myocardial infarction with currently available equipment, and 129Cs was next best. However, because of instrument setting and commercially obtained preparations, 81Rb could not be properly compared with the other radionuclides in our study.

Animals↗
PubMed1977

Dosimetric studies in the radiological examination of the hips in young infants with a special fenestration method of gonad protection.

A special lead shield of 1,5 mm Pb, with a fenestration was used for gonad protection during X-Ray of the hips for detection of dysplasia. The window allows the delineation of all parts of the skeleton required to make a correct diagnosis and check the standardized position of the pelvis, while all other parts, especially the gonads are safely shielded. The scattered radiation for the testes was further reduced by a trough-shaped lead shield behind the scrotum. The effectiveness of this gonad protection was measured by direct dosimetric studies on the infant with LiF and CaF2: Dy dosimeters at different adjustments of the X-ray generator and with medium and ultra high speed screen-film combinations.

Female↗
PubMed1975

The evolutionary origin of feathers.

Previous theories relating the origin of feathers to flight or to heat conservation are considered to be inadequate. There is need for a model of feather evolution that gives attention to the function and adaptive advantage of intermediate structures. The present model attempts to reveal and to deal with, the spectrum of complex questions that must be considered. In several genera of modern lizards, scales are elongated in warm climates. It is argued that these scales act as small shields to solar radiation. Experiments are reported that tend to confirm this. Using lizards as a conceptual model, it is argued that feathers likewise arose as adaptations to intense solar radiation. Elongated scales are assumed to have subdivided into finely branched structures that produced a heat-shield, flexible as well as long and broad. Associated muscles had the function of allowing the organism fine control over rates of heat gain and loss: the specialized scales or early feathers could be moved to allow basking in cool weather or protection in hot weather. Subdivision of the scales also allowed a close fit between the elements of the insulative integument. There would have been mechanical and thermal advantages to having branches that interlocked into a pennaceous structure early in evolution, so the first feathers may have been pennaceous. A versatile insulation of movable, branched scales would have been a preadaptation for endothermy. As birds took to the air they faced cooling problems despite their insulative covering because of high convective heat loss. Short glides may have initially been advantageous in cooling an animal under heat stress, but at some point the problem may have shifted from one of heat exclusion to one of heat retention. Endothermy probably evolved in conjunction with flight. If so, it is an unnecessary assumption to postulate that the climate cooled and made endothermy advantageous. The development of feathers is complex and a model is proposed that gives attention to the fundamental problems of deriving a branched structure with a cylindrical base from an elongated scale.

Animals↗
PubMed1975

The effect of radar on cardiac pacemakers.

The susceptibility of 16 noncompetitive cardiac pacemakers to radiation from a powerful radar system was investigated in the laboratory and in the vicinity of its prototype. From comparative in vitro tests in air, fat, water, and saline it was concluded that only tests in fat or air represent the worst case condition after implantation. In air all pacemakers showed signs of interference at pulse power densities between 0.025 mW/cm2 and 62.5 mW/CM2. Three of six implanted pacemakers were triggered or inhibited depending on their mode of operation when tested at a location 1.2 km away from the radar station by the radar beam occurring every 5.5 sec. Because interfering radiation can enter the pacemaker circuitry directly along the electrode, acting as an antenna, metal encapsulation of the pulse generator does not provide sufficient shielding against microwave radiation. However, pacemakers modified by metal encapsulation and a low-pass filter at the electrode remained undistrubed at pulse power densities of greater than 10 W/cm2 when tested under worst case condition in air.

Evaluation Studies as Topic↗
PubMed1976

Eye protection from light radiation.

It appears that green absorptive lenses are highly desirable for the purposes of shielding the eyes against light radiation from molten metal during the casting and soldering procedures. The dental laboratory technicians have experienced no after-images, less eye fatigue, and no adverse symptoms when using these lenses, as were reported previously. The lenses not only effectively protect the eyes from the injurious light wavelengths, but they also provide for enough normal (as well as individually corrected) vision to accomplish any procedure necessary in the dental laboratory. We propose that the green absorptive lenses, with individual corrections if needed, be considered for dental laboratory technicians during dental laboratory procedures when needed, such as during casting and soldering, to protect their eyes from light radiation.

Color↗
PubMed1976

A dental radiologic health laboratory teaching method.

The School of Dental Medicine at Tufts University has given new direction to the understanding of radiologic health through a program in which all students participate in some laboratory activities directly related to the problems of radiologic health in dental practice. This article presents an explanation of the background of this program and the experiments performed and discusses the interest in the program and its effect on the dental students. The laboratory program described is held for 3 1/2 hours on Wednesday afternoons at the Dental School, since this is a period of minimum patient load in the Radiology Department. The course is presented for third-year dental students who already have takin a lecture course in the fundamentals and techniques of radiology and have received training in the proper procedures for taking radiographs. The program is designed as a series of experiments dealing with machine output, filtration, collimation, exposure factors, scatter radiation, film density, patient protection, and shielding. The students are introduced to various radiation-detection instruments and given the opportunity to use these instruments to measure output and scatter-radiation levels under varying conditions. The laboratory teaching method presented can also be reprogrammed for different group sizes and time schedules.

Boston↗
PubMed1977

[Radiation-physical conditions concerning irradiation by means of remote afterloading (author's transl)].

Afterloading techniques, proposed as early as 1903, came into practical use only during the last two decades. Remote afterloading techniques were introduced clinically when suitable sealed gamma sources became available and reliable equipment were designed, transferring the radiation sources between a shielding container and suitably designed irradiators in the patient. The technique can be used with low or high dose-rate and offers several advantages, such as complete elimination of all radiation protection problems, optimization of the treatment technique - through several means - and possibly increased treatment capacity. Two applications of a particularly flexible system are illustrated. Requirements for the development, advantages with today's technique and possibilities for future development are discussed.

Female↗
PubMed1978

Radiotherapy of benign dermatoses: indications, practice, and results.

Limited indications for radiation treatment of benign dermatoses are presented in order to emphasize modern restrictions and techniques in the use of dermatologic radiation therapy and to promote measures of protection against stray radiation. The use of softer, less penetrating X rays, least effective doses and meticulous shielding are recommended. So done, radiation therapy offers an effective therapeutic alternative for conditions that do not respond to other forms of treatment.

Acne Vulgaris↗