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Biomedical subjects

K E Ekstrand

Publications and source records attributed to K E Ekstrand.

12 recordsLinked to original sources
PubMed1979

The inverse compensating filter.

When a single-field technique is used in megavoltage x-ray therapy, a uniform entrance dose is often required. If there is a large variation in source-to-surface distance over the field, an inverse type of compensating filter is necessary to achieve entrance dose uniformity. The production and utilization of these filters is discussed.

Filtration↗
PubMed1978

A film dosimetry system for use in computed tomography.

The authors describe a film dosimetry system for use in calculating the surface dose delivered by a CT scanner. Kodak XV-2 film is wrapped around a cylindrical water-filled phantom and the dose distribution is recorded. This system is easier to use than thermoluminescent dosimetry (TLD) and provides a detailed map of the dose distribution. Comparison with TLD measurements for a variety of CT scanners indicates that an accuracy of +/-15% can be achieved using this system. Dose distributions obtained with several scanners are shown.

Humans↗
PubMed1977

Proton NMR relaxation times in the peripheral blood of cancer patients.

The proton spin lattice relaxation time (T1) of serum and leucocytes of cancer patients and normal volunteers was measured using pulsed NMR techniques. There was no statistically significant difference in the serum T1 values of cancer patients relative to normal. An increase in T1 relative to normal values was detected in the white blood cells of patients with active leukaemia. In these patients T1 fell to normal levels after the initiation of treatment. The variation of leucocyte T1 with the course of the disease for five patients having leukaemia is presented.

Breast Neoplasms↗
PubMed1976

The routine use of graphic data handlers in a radiotherapy department.

Graphic data handlers are helpful in routine dosimetry. The authors describe a computer program using a graphic digitizer which facilitates determination of the equivalent square of an irregularly shaped field. The digitizer can also be used together with an incremental plotter to produce patterns by which Styrofoam molds can be cut for field-defining blocks. Both programs are designed to be used at a remote time-sharing computer station.

Computers↗
PubMedDate not supplied

Series of high-sensitivity TL phosphors made from divalent-metal sulfates.

A systematic survey of the thermoluminescence (TL) of rare earth activated sulfates of the form MeSO4:RE was made, where Me denotes a divalent metal and RE the rare earth. SrSO4:Tb(3+) and BaSO4:Eu(2+) exhibit very high TL efficiency following gamma irradiation, comparable to that of the most sensitive phosphors currently available for TL dosimetry. Due to their relatively high Z, these phosphors could prove useful as quality indicators for personnel dosimetry or for detecting very small exposures of low-energy X rays of a known quality.

Barium Sulfate↗
PubMedDate not supplied

Heuristic model for understanding x-ray film characteristics.

A simple, heuristic model of a photographic emulsion is described for the purpose of illustrating the fundamental physical processes and emulsion properties which determine the characteristics of an x-ray film (viz., the shape of the H - D curve, film gamma, and film speed). By means of this model, it is shown that the contrast multiplication afforded by an x-ray film (i.e., a film gamma greater than unity) is a direct result of the exponential attenuation of the viewing light by the developed film, and that film gamma is proportional to grain size, grain density, and emulsion thickness. The difference in the H - D curve that is observed when the same film is exposed to light from an intensifying screen or directly to x rays is also predicted by the model.

Models, Theoretical↗
PubMedDate not supplied

Linear accelerator calibration monitor with a memory.

A calibration monitor has been designed for measuring the constancy of linear accelerator or cobalt unit output between full calibrations. This monitor is battery operated, light-weight and slides into the shadow tray attachment on a linear accelerator or cobalt unit for easy setup. It provides a digital readout of the dose delivered, and a consistency check can be made in less than two minutes. The precision of the monitor, determined by cobalt-60 irradiations over a 2 1/2 period, is +/- 0.6% (standard deviation). The monitor also retains the dose reading in a CMOS digital counter indefinitely, hence it can be used in the same fashion as mailed thermoluminescent dosimeters (TLD) for calibration checks at remote facilities without the complicated readout procedures associated with TLD. The monitor can be mailed to a remote facility, positioned without ambiguity, and irradiated; and the reading can be verified on return to the originating center simply by pressing a switch. The monitor can easily be set up to carry out a "blind" check in which the reading obtained is not known to the remote facility.

Calibration↗