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J J Spokas

Publications and source records attributed to J J Spokas.

6 recordsLinked to original sources
PubMedDate not supplied

Composition of A-150 tissue-equivalent plastic.

In recent years, the use of tissue-equivalent materials has become quite common in fast-neutron dosimetry, with the A-150 plastic developed by Shonka et al. probably the most popular. Information on this specific plastic is scantily reported in the literature and as a consequence a preponderance of authors unknowingly reference an article by Shonka describing an early version of a tissue substitute plastic but having a different elemental composition than the present A-150 formulation. We have reviewed the results of 21 chemical analyses which have occurred over a time span of four years on a total of 14 samples of A-150 plastic and based on these data and the formulation of the plastic, have arrived at a suggested composition for A-150 tissue-equivalent plastic. The ambiguities of water absorption by nylon, one of the components of the plastic, and the uncertainty this reflects in the composition of the plastic were evaluated.

Fast Neutrons↗
PubMedDate not supplied

Investigation of cables for ionization chambers.

Seven coaxial cables which are in use for carrying currents generated in ionization chambers have been critically studied with reference to their suitability to this application. Included in this study are four low-noise triaxial cables and three low-noise two-conductor cables. For each cable the following characteristics were considered: inherent noise currents, currents produced by cable movements, polarization currents, the degree of electrostatic shielding of the central signal-carrying conductor, and radiation-induced cable currents. The study indicated that of the seven cables, two low-noise triaxial cables, both employing solid Teflon dielectric surrounding the central conductor, appear to offer the best overall performance for use with ionization chambers.

Electricity↗
PubMedDate not supplied

Dose descriptors for computed tomography.

A weakness in the dose descriptor, the computed tomography dosimetry index, is discussed and an alternate descriptor is proposed. The new descriptor, the equivalent rectangular width, conveniently expresses the spatial spread of dose and is simply derived from customary dose measurements. A measure of performance, which expresses the relative size of the volume being imaged with respect to the volume receiving the dose, is suggested for computed tomography. 87.70.Es, 87.60.Mv.

Radiation Dosage↗