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At least 163 records · Page 9Linked to original sources
PubMed1978

Mathematical aspects of divergent beam radiography.

At the present time, largely because of a breakthrough in radiology called computed tomography, the attenuation of x-ray beams is measured in extremely sensitive quantitative ways, and the information from many x-ray sources is assembled and analyzed on a computer. In this situation mathematics can make significant contributions concerning the nature of the information conveyed by x-rays from many sources, the extent to which this information determines the object x-rayed, suitable configurations of sources, methods for using the data to build a detailed reconstruction of the object, etc. This article announces results on these topics for the divergent x-ray beam. The three-dimensionally divergent beam, or cone beam, presents new problems that do not appear in the two-dimensional, or fan beam, case.

Journal Article↗
PubMed2005

Instrumentation for synchrotron-radiation macromolecular crystallography.

X-ray diffraction is an extremely important tool for structure determination of biological macromolecules, to the extent that currently around 85% of Protein Data Bank entries result from X-ray measurements. Many of these structure determinations use synchrotron radiation for data collection. This article aims to give synchrotron users an overview of the functioning of a synchrotron beamline and how the performance of various instruments combines to allow the collection of diffraction data.

Computer Simulation↗
PubMed2003

Extremity soft tissue sarcoma patient follow-up: tumor grade and size affect surveillance strategies after potentially curative surgery.

A large recent survey disclosed considerable variation in the intensity of follow-up after potentially curative surgery for extremity soft tissue sarcoma among highly credentialed clinicians. The source of the variation is not known. The survey was reanalyzed to investigate whether tumor grade and size account for the variation. The 1,592 members of the Society of Surgical Oncology were surveyed to measure their follow-up practices for 10 years after initial therapy for extremity sarcoma. Repeated-measures analysis of variance was used to measure the relationship among follow-up practice patterns and tumor grade, tumor size, and years after surgery. The 318 respondents who performed surgery and also carried out long-term follow-up for their patients with extremity soft tissue sarcoma were considered evaluable; 94% were general surgeons and 5% were orthopedic surgeons. Office visit, complete blood count, liver function tests, chest X-ray, chest computed tomography, extremity computed tomography, and extremity magnetic resonance imaging were ordered significantly more frequently with increasing tumor grade and size. Tumor grade and size significantly impacted physician practice patterns in post-treatment follow-up, although the degree of variation attributable to these variables was modest. These data permit rational design of a randomized clinical trial of two alternative follow-up plans.

Delivery of Health Care↗
PubMed1993

Crystallization and preliminary X-ray analysis of the beta-galactosidase from the extreme thermophilic archaebacterium Sulfolobus solfataricus.

The beta-galactosidase from the extreme thermophilic archaebacterium Sulfolobus solfataricus has been crystallized from polyethylene glycol 4000 in the presence of sodium acetate and acetate buffer at pH 4.6. The protein crystallizes in P3(1)21 or P3(2)21 (a = 169.4, c = 98.29) and the crystals diffract beyond 2.5 A. The measured crystal density (approximately 1.28 g/cm3) is consistent with the presence of a tetramer (molecular mass 240 kDa) in the asymmetric unit. The specific volume of the crystals is 1.7 A3/Da, indicating a solvent content by volume of only 27%, which is amongst the lowest values observed for protein crystals, and indicates virtual close-packing of the tetramers.

Crystallization↗
PubMed1982

Single crystals of 5S rRNA from Thermus thermophilus HB8 and preliminary X-ray diffraction data.

5S rRNA from extremely thermophilic bacteria, Thermus thermophilus HB8, was crystallized. Using a vapour diffusion method, single crystals were grown with sufficient sizes for x-ray diffraction study. The crystals belong to space group P3(1)21 (or enatiomorph P3(2)21) with a = 99 A, b = 99 A and c = 360 A. A unit cell contains probably 36 molecules corresponding to 6 molecules/asymmetric unit. A smaller pseudo-lattice seems to be constructed with the same lengths for a- and b-axis, and 120 A for c-axis. Reflections were observed up to 25 A on x-ray photographs.

Crystallization↗
PubMed1992

[Use of therapeutic discrete plasmapheresis in combination with extracorporeal blood irradiation with ultraviolet rays in the treatment of patients with obliterative disease of blood vessels of the lower extremities].

The results of treatment of 440 patients with obliterative diseases of the arteries of the lower extremities are presented. Use of the ultra-violet rays for extracorporeal irradiation of the blood in combination with discrete plasmapheresis has a pronounced therapeutic effect, contributes to improvement in regional blood flow and shortening the duration of patients' staying in the hospital by 5-7 days.

Adult↗
PubMedDate not supplied

[Requirements and their realization in thoracic radiography].

Physicians, financial sponsors or administrators, and public opinion make different demands on a working place concerned with chest radiography. The article describes how these demands are translated into reality by present-day equipment setups and systems. In particular, attention is paid on the basis of a slit type radiographic method to present technical possibilities in respect of image quality, dosage and running costs. Modern X-ray systems can produce a high-quality and low-cost X-ray image with an extremely minimal dose that is nearly no longer measurable (3% of the previously employed dose). The image obtained in this manner is of a diagnostic value comparable to that of the conventional large-size X-ray images.

Humans↗
PubMed1968

Dictyostelium discoideum: a gamma-ray resistant organism.

The vegetative cells of the slime mold Dictyostelium discoideum are extremely resistant to cobalt-60 gamma rays. The survival curve has a shoulder at low doses and a 10 percent survival dose of 300 kilorads in air. Dose fractionation experiments indicate that repair of sublethal damage is an important factor in this resistance.

Cobalt Isotopes↗
PubMed1978

[X-ray-video amplifier photography: use in urologie X-ray diagnosis and renovasography (author's transl)].

Our experiences indicate that the 'urograph', in combination with the 100-mm sheet-film camera, represents an x-ray apparatus that is just about optimally suited to the needs of urologic x-ray diagnoses. Only in extreme situations is the range of movement of the tabletop in the direction of the head and feet insufficient. A major advantage of the camera, and the one which, above all, plays a decisive role in the urologic x-ray diagnosis of children, is that the amount of radiation can be reduced by about 1/2 to 1/3 that necessary with conventional photo techniques. Through optimal use of the apparatus, considerable time and personnel can be saved. In view of the additional fact that kidney angiographs can be performed with this apparatus, in combination with the 100-mm camera, with minimal problems, minimal time, and minimal stress for the patient, x-ray-video amplifier photography represents an important addition to urologic x-ray examination possibilities that today we can no longer afford to do without.

Angiography↗
PubMed2002

Hand-held three-dimensional dental X-ray system: technical description and preliminary results.

OBJECTIVE: To design, fabricate, and perform preliminary in vitro testing of a portable, hand-held, three-dimensional (3D) dental X-ray system using options unique to Tuned-Aperture Computed Tomography (TACT). The design allows for task-specific positioning over an unlimited range of user-selected angles and incorporates an integrated laser guidance system to constrain the focal-object distance. METHODS: A prototype system was fabricated consisting of an extremely lightweight X-ray source cantilevered from an aluminum gunstock-type handle to which a transparent radiation scatter shield was attached. Aiming was facilitated by task-specific visual cues used in conjunction with a spherically shaped radiolucent alignment jig coupled to the tissues of interest. Proper range was assured by a laser-assisted guidance system. The image transducer was an extrinsically modified commercially available CMOS device. The irradiated patient was simulated by a DXTTR phantom. RESULTS: The prototype demonstrated automated display of radiographed intra-oral tissues in three dimensions from arbitrary projection geometries and simulated task-specific sequences. Uncontrolled movements between exposures produced no obvious degeneration of 3D image quality. The aiming system minimized technical errors from misangulation. All dental regions in the phantom were imaged without difficulty. Projected risk was observed to be within clinically acceptable limits. CONCLUSIONS: Task-specific 3D images can be generated from as few as three uncontrolled projections. Total exposures can be prorated to levels not greatly exceeding those required for conventional two-dimensional radiographs of comparable image quality. Predicted radiation risks lie well below existing guidelines for occupational exposure.

Dental Equipment↗
PubMed2006

A case report comparing various radiological tests in the diagnosis of calcific uremic arteriolopathy.

BACKGROUND: Calcific uremic arteriolopathy (CUA) is a rare necrotizing skin condition characterized by calcification in arterioles, leading to ischemia and skin ulcerations. This disease affects 1% to 4% of patients with chronic kidney disease and has a reported mortality rate up to 80%. The diagnosis of CUA is based on clinical judgment suggested by the characteristic skin lesions. Although skin biopsy is the gold standard for establishing the diagnosis, it is performed infrequently because of poor healing and risk for secondary infections. METHODS: In this case report, we compare the ability of various radiological tests to show arteriolar calcifications of patients with CUA. Our patient had biopsy-proven CUA manifesting as chronic nonhealing ulcers of the calves. She underwent soft-tissue x-ray of the affected extremities and high-resolution (0.5-mm slice) computed tomographic (CT) scanning with 3-dimensional image reconstruction. We also used a dedicated mammography machine to obtain images of the patient's calves. Images were compared based on the ability to show small-vessel calcification. RESULTS: Plain soft-tissue x-ray showed mildly increased soft-tissue density and very few calcified vessels, whereas CT showed few calcified small- and medium-sized arterioles. Diffuse calcification of small arterioles in a mesh-like pattern was shown by means of the mammography technique. CONCLUSION: Simple, safe, and inexpensive x-ray imaging using the mammography technique was superior to plain soft-tissue x-ray and 3-dimensional CT in showing the hallmark arteriolar calcifications of patients with CUA. Thus, we propose a possible role for this technique in diagnosing CUA.

Aged↗