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Nov 1974

Volume 1, Issue 6, pp. 303-328


ARTICLES: Calculation of the effects caused by bone present in phantoms irradiated by negatively charged pions

R. T. Santoro, R. G. Alsmiller, Jr., and K. C. Chandler

Med. Phys. 1, 303 (1974); http://dx.doi.org/10.1118/1.1637312 (8 pages)

Online Publication Date: 6 November 2003

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The effects caused by bone present in phantoms irradiated by negatively charged pions on absorbed dose, cell survival, oxygen enhancement ratio, and relative biological effectiveness have been estimated using Monte Carlo methods. The influence of bone along the pion path and also the influence of a bone–tissue interface parallel to the direction of motion of the pions have been considered. Calculated results, as a function of spatial coordinates in a 30‐g/cm2‐thick tissue phantom with bone both included and excluded, are presented. All of the biological data reported here are for T‐1 human kidney cells. The extent to which the effects of bone in the path of the pion beam can be approximated by using results for tissue and measuring depth in the phantom in g/cm2 is considered and discussed.
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87.56.Da Ancillary equipment

ARTICLES: Acoustical properties of blood: A look at the basic assumptions

Avtar Singh Ahuja

Med. Phys. 1, 311 (1974); http://dx.doi.org/10.1118/1.1637313 (6 pages) | Cited 2 times

Online Publication Date: 6 November 2003

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The results from the literature on acoustics in suspensions, excluding the phenomena of relaxation, have been applied to study the effects of red‐cell and plasma densities, compressibilities, viscosities, thermal conductivities, and surface tension on the propagation of sound in blood. For the calculations of the viscous and the thermal absorptions and of the velocity of sound in blood, the red cell may be treated as a rigid spherical particle containing the same volume. For the calculation of the thermal absorption, the erythrocyte may be treated as a spherical particle of finite thermal conductivity at all frequencies; but for the calculation of the velocity of sound, the effect of heat conduction can be ignored above 1 MHz and Wood's sound velocity formula may be used. The calculated sound absorption due to shear viscosity and thermal conduction in whole blood constitutes a significant portion (about 60% or more) of the measured value of the total absorption toward the lower‐frequency range (1 MHz or less) and a negligible portion (about 15% or less) of the total absorption toward the higher‐frequency range (10 MHz or more).
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87.50.Y- Biological effects of acoustic and ultrasonic energy

ARTICLES: Comparison of fast neutron beams for radiotherapy produced by 17.3‐MeV deuterons incident on beryllium and deuterium targets

F. M. Edwards, H. W. Fielding, J. J. Kraushaar, and K. A. Weaver

Med. Phys. 1, 317 (1974); http://dx.doi.org/10.1118/1.1637314 (6 pages) | Cited 2 times

Online Publication Date: 6 November 2003

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Fast neutron beams produced by 17.3‐MeV deuterons incident on a totally stopping beryllium target, a totally stopping deuterium gas target, and a 5.8‐MeV‐thick deuterium‐gas target are compared. It is shown that the deuterium‐gas target yields a significantly higher average energy and dose rate and may offer other advantages as well.
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87.53.Bn Dosimetry/exposure assessment

ARTICLES: Verification of a practical method for making individual corrections for inhomogeneities in the thorax

Ann E. Wright and Melvin F. Strockbine

Med. Phys. 1, 323 (1974); http://dx.doi.org/10.1118/1.1637315 (3 pages)

Online Publication Date: 6 November 2003

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Cobalt‐60 teletherapy dose calculations utilizing a standard correction factor for thorax inhomogeneities can result in dose error due to patient variability. Individual intracavitary measurements avoid this error but are impractical for routine clinical use. A graph has been constructed relating the ratio of measurements made with and without the patient in the beam to an equivalent water depth. With an ordinary ion chamber secured to the beamstopper, the dose was integrated during a 1‐min rotation. A known water depth was used to derive apparent linear attenuation coefficients which, with the equation D0 ∕ Dt = eμt, enabled construction of the graph. To verify the method, tubes with dosimeters were positioned at the axis of rotation during the first treatment of patients with esophageal tumors. Agreement of corrected dose with measured dose is within 3% for 360 deg rotational treatment; uncorrected dose calculations would have resulted in errors of 5%–21%.
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87.53.Jw Therapeutic applications, including brachytherapy

SHORT REPORTS: Photonuclear production of potassium‐38

Coye M. Cole, Fred C. Gray, G. Malcolm Meaburn, and John S. Stevenson

Med. Phys. 1, 326 (1974); http://dx.doi.org/10.1118/1.1637316 (2 pages)

Online Publication Date: 6 November 2003

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Radioactive potassium‐38 has been produced by the photonuclear reactions 39K(γ,n)38K and 40Ca(γ,np)38K, using the bremsstrahlung field developed by an electron linear accelerator. Non‐carrier‐free 38K was produced by irradiating potassium hydroxide pellets for 30 min using 10 kW of 40 MeV electrons passing through a thick tantalum converter. Yields of 25–35 mCi 38K per gram irradiated KOH were obtained. Carrier‐free 38K was produced by similarly irradiating shredded calcium metal, obtaining 2–6 mCi per gram of calcium. In both cases, the target material was dissolved in HCl, neutralized, and prepared as sterile solutions of KCl for injection.
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87.57.un Radiopharmaceuticals

SHORT REPORTS: Current‐limiting resistor for polarizing batteries

Stephen Balter

Med. Phys. 1, 328 (1974); http://dx.doi.org/10.1118/1.1637317 (1 page)

Online Publication Date: 6 November 2003

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The addition of a current limiting resistor to the high‐voltage polarizing batteries of an ionization chamber is described to reduce accidental shock to personnel and possible equipment damage.
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87.56.Da Ancillary equipment
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Medical Physics is an official science journal of the AAPM and of the COMP/CCPM/IOMP
William R. Hendee, Editor
Departments of Radiology, Radiation Oncology, Biophysics, Community and Public Health, Medical College of Wisconsin
One Physics Ellipse
College Park, Maryland 20740
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