How consumers view chiropractic advertising.

Chiropractic, as a medical profession, is finally receiving acceptance from the American Medical Association (AMA) and other medical groups. However, what do consumers think about chiropractors and how do they respond to the advertising efforts of chiropractors? This paper presents the findings of a survey concerning consumers' opinions of advertising by chiropractors. Although the opinions of the respondents were mixed, an analysis of the results of the survey suggests important implications for chiropractors and other medical practitioners who wish to use advertising media in marketing their services.

How consumers view physician advertising.

In this study, it was found that consumers generally favor advertising by physicians. They felt that newspaper and professional magazines were more appropriate media for such advertising than television, radio, billboards, telephones, direct mail, and popular magazines. Finally, most consumers have not seen physicians advertise, but of those who have, most have noticed such advertising in a newspaper.

How consumers view hospital advertising.

The purposes of this study were to determine: (a) consumers' attitudes toward advertising by hospitals; (b) which media consumers feel are appropriate for hospital advertising; and (c) whether consumers are seeing hospital advertisements, and if so, through which media. It was found that consumers indeed have a favorable attitude toward hospitals that advertise. It was also found that consumers feel that most media are appropriate for hospital advertising. Finally, it was found that most consumers have seen hospitals advertise their services, especially on television and radio and in the newspaper.

Measurement of the effective dose equivalent in a nuclear reactor environment with a personal thermoluminescent dosimeter.

A study was performed on the measurement of the effective dose equivalent (EDE) with a personal thermoluminescent dosimeter. A Rando phantom with dosimeters inserted at the sites of the tissues specified by ICRP Publication 26 (ICRP77) was exposed at selected locations inside nuclear power stations. The effective dose equivalent was calculated and compared to the personal dosimeter response worn at the normal chest and waist locations. It was found that the EDE could be adequately measured and that the average rem/R conversion factor varied between 0.79 and 0.87, depending on the wearing position and sex of the worker.

Second scatter contribution to dose in a cobalt-60 beam.

Semi-analytic and direct numerical integration approaches have been used to study the contribution of doubly scattered photons to dose at a point P in a homogeneous water medium irradiated by a cobalt-60 point source. The semi-analytic analysis was used for an infinite field radius to calculate the variation of second scatter dose with depth, the angular dependence of the second scatter dose, and the spectra. Direct numerical integration was used to calculate the second scatter dose at a depth of 10 cm for various finite field radii ranging from 0 to 25 cm. Maps were made of the locations of scattering sites that were important to the second scatter dose. These calculations show that the second scatter contribution is generally less than the first scatter dose with the exception of a few sites remote from the point of interest. In many ways, the pattern of dose deposition by second scatter is similar to first scatter with less pronounced features. In other respects, the second scatter appears more isotropic. The implications of these calculations for approximate radiotherapy dose calculations are discussed.

Effect of small inhomogeneities on dose in a cobalt-60 beam.

The effect of small ring-shaped cavities on the dose delivered by a cobalt-60 beam to a homogeneous medium was studied experimentally and theoretically. Changes as small as 1 x 10(-4) of the total dose were measured. Experimental results show that, depending on the position of the cavity, replacing water with a small cavity can either increase or decrease scatter dose to a point in the medium. The increase in scatter dose was not anticipated and to our knowledge is not predicted by any of the presently available inhomogeneity dose correction algorithms used in treatment planning. Calculations were based on the perturbations of first and second scatter dose contributions and show that the presence of a cavity in the medium introduces three processes that decrease scatter dose and five that increase it. The calculated net effect is in good agreement with experiment. Additional calculations show that the effect of a single small inhomogeneity cannot be easily extrapolated to larger inhomogeneities and that multiple inhomogeneities do not act independently. Results from this study demonstrate two constraints that must be satisfied by future dose calculation algorithms: (i) they must correctly determine dose in a homogeneous non-unit density material, and (ii) they must account for the change in dose due to small inhomogeneities in the medium.

Theoretical and experimental determination of sensitivity and edge enhancement in xeroradiography and ionography.

A study of the factors affecting image quality and x-ray sensitivity of ionography and xeroradiography is presented. First, the relative charge sensitivities (nC/cm2mR) are compared. It is shown that high pressure xenon (10 atm cm) as used in ionography produces more than 2.5--3.5 times more charge than the selenium layers used in xeroradiography for the same x-ray exposure. The influence of development time and toner deposition on the appearance of images is investigated theoretically and experimentally. A parameter describing development sensitivity is proposed. It is shown that an increase in development sensitivity (ODcm2/nC) with increasing development time is accompanied by a loss in edge enhancement. The development sensitivity of ionography is about twice that typical of xeroradiography. This makes the total sensitivity (OD/mR) or the ionography process more than 4.5--6.5 times that of xeroradiography. The total sensitivity of ionography is about 1/2 that of par speed film screen combinations.

A technique for the treatment of large irregular fields.

Each method of producing irregular shaped fields has its own particular advantage. This report describes one technique of irregular field production with minimal handling of the shielding material, tapered shielding to provide the greatest accuracy in the field shape, and rapid achievement of patient setup. The reproducibility of these fields is considered.

Calculation of the average energy absorbed in photon interactions.

High energy electrons set into motion by photon interactions with matter lose some of their energy by bremsstrahlung. This loss must be evaluated before energy absorption coefficients may be calculated. Recent extensive tables of data published by Plechaty et al. contain an appreciable error in this quantity. The error results from two simplifying assumptions and for the case of very high photon energies interacting with high atomic number materials can be as much as a factor of two. This has important implications for the evaluation of quantities used in radiation dosimetry.

Variations in x-ray exposures to patients.

X-ray exposures to patients were measured in 30 rooms in Toronto hospitals. For a given procedure, the total exposure for a satisfactory examination differed from one room to another by as much as a factor of 30, skin exposures reaching 90 R and more for barium enemas and barium meals. The factors primarily responsible for these large differences in exposure were fluoroscopic exposure rate (0.65-12 R/min) and time 1.5-12 min), kVp and filtration (8:1), choice of screen-film combination (6:1) and attenuation of table tops and phototimers (4:1). The increase by a factor of 5 in exposure of pelvic organs, when using beams directed AP instead of PA, requires that remote-controlled GI machines be used cautiously, particularly on women of childbearing age. It is also important that these machines have tables with low attenuation. The use in some rooms of minimal fluoroscopic exposure rates and 70 mm fluorography at total exposures of less than 5 R shows that radiographic examinations can be made virtually "safe" with modern, properly adjusted equipment.

Edge contrast in ionography.

The effect of Mylar foil thickness on the appearance of ionography images has been investigated. Approximate expressions for the depletion width of strips and halfplanes of charge are given with supporting experimental measurements. In microdensitometer traces of charged strips and halfplanes the density is shown to be proportional to the vertical field profile of the charge pattern near the Mylar. This work suggests a simple means of altering edge contrast for ionography by using different thicknesses of Mylar. Ionography images of a hand phantom illustrate this effect.

Use of electron filters to improve the buildup characteristics of large fields from cobalt-60 beams.

It has been shown that for Cobalt-60 units capable of producing large fields (up to 40 X 40 cm2)at 80 cm, the dose distribution in the buildup region is quite different from that observed with small fields. First, the maximum dose occurs at 1-2 mm instead of 5 mm; and second, the maximum does in some extreme cases is 15%-20% higher than the dose at 5 mm. Thus, the dose is decreased by more than 15%-20% by 3 mm of tissue, suggesting severe electron contamination. In this report, it is shown that this contamination can be best removed by a filter of thickness 0.4 g/cm2 of medium atomic number, placed some 25 cm from the source inside the collimator. For existing units, positioning the filter inside the collimator is not practical. Acceptable results, however, can be obtained by placing the filter just below the collimator.