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Biomedical subjects

J W Poston

Publications and source records attributed to J W Poston.

At least 19 recordsLinked to original sources
PubMed1991

Adverse drug effects and the need for drug information.

The information needs of a group of patients taking antihypertensive medication were assessed with special emphasis on the influence of perceived symptoms of high blood pressure and adverse drug effects. All patients of a hypertension clinic currently on antihypertensive medication were included in the study. The response rate to the questionnaire was 85%. Of the 623 patients included, only 31% expressed satisfaction with the amount of information received on adverse effects of their antihypertensive drugs. Patients younger than 50 years explicitly expressed a need for information more often than those older than 64. There were no differences in the expressed information needs between men and women. The reported experience of symptoms related to high blood pressure and adverse drug effects was more common among younger patients than among the elderly. Of those who experienced both adverse drug effects and symptoms, 57% expressed a need for more information, whereas only 30% of those who had no such experiences expressed a need for more information on adverse drug effects. It was concluded that there is a substantial need for more information on adverse drug effects, especially among those who have experienced adverse drug effects or some symptoms of hypertension.

Adult↗
PubMed1991

Absorbed dose calculations to blood and blood vessels for internally deposited radionuclides.

At present, absorbed dose calculations for radionuclides in the human circulatory system used relatively simple models and are restricted in their applications. To determine absorbed doses to the blood and to the surface of the blood vessel wall, EGS4 Monte Carlo calculations were performed. Absorbed doses were calculated for the blood and the blood vessel wall (lumen) for different blood vessels sizes. The radionuclides chosen for this study were those commonly used in nuclear medicine. No penetration of the radionuclide into the blood vessel was assumed nor was cross fire between the vessel assumed. The results are useful in assessing the dose to blood and blood vessel walls for different nuclear medicine procedures.

Adult↗
PubMed1991

Estimates of beta absorbed fractions in small tissue volumes for selected radionuclides.

Energy deposition patterns are dependent upon the size and geometry of the source region, distribution of radioactive material, types of radiations and energies emitted by the radionuclide, as well as interfaces between different materials which may exist within the region. Commonly, in absorbed dose calculations for internally deposited beta-emitting radionuclides, it is assumed that the absorbed fraction of energy for the mean beta energy is a sufficient representation of the beta spectrum. The accuracy of this assumption was tested by comparing absorbed fractions calculated using actual beta spectral energies with those obtained using the mean beta energy for several radionuclides commonly used in nuclear medicine. A sphere composed of tissue was chosen as the preferred geometry. Spheres of 0.1, 0.5, 1.0, and 2.0 cm radius were used, and absorbed fractions were calculated as a function of surface-to-volume ratios. This allows the assessment of absorbed fraction in spheres where there is a uniform distribution of a radionuclide.

Beta Particles↗
PubMed1990

Drug prescribing in residential homes for elderly people in the United Kingdom.

Data relating to the use of medicines from a descriptive epidemiologic study of drug use in 55 residential homes for elderly people in Britain were analyzed. Of the 1888 residents included in the study, 1617 (85.6 percent) received a total of 5535 medicines. The median number of medicines received per day was three and the per-day range varied from one to thirteen medicines. Significantly more women than men received medicines and women also received more medicines each. The most frequently prescribed group of medicines were those acting on the central nervous (34.0 percent), the cardiovascular (27.2 percent), and on the gastrointestinal (8.9 percent) systems. Deficiencies were identified in doses, duration, and selection of drugs in certain therapeutic groups.

Aged↗
PubMed1988

Education and training in health physics--a look to the future.

The next 15 to 20 y promise to be a challenging period in health physics education. The U.S. Department of Energy, in a review of current and projected labor market conditions for professional health physicists and health physics technicians, reports current shortages of professional health physicists in the civilian nuclear industry and predicts a high potential for shortages during the next 15 y. The academic health physics community is also faced with the following issues that compound the difficulty in meeting the high employment demands for qualified health physicists in the near future. (1). A decreasing number of programs--In the past few years, several programs have folded or have undergone reorganization, thus reducing the availability of quality programs to train health physicists and health physics technicians. (2). Decreasing federal funding--Government funding of health physics programs is limited, necessitating programs to obtain support from the private sector or from within the colleges and universities themselves. (3). Accreditation of programs--Should programs be accredited to standardize quality and program content? (4). Recruiting quality students--What can programs do to attract high-quality students into the health physics profession? In this paper, each of these issues is examined and possible solutions proposed. Our discussion is primarily meant to be provocative--in this way we hope to stimulate much-needed discourse as a first step in addressing and solving these problems which face the academic health physics community.

Education↗
PubMed1988

The use of diuretic medicines by elderly people in residential homes.

Data relating to the use of diuretics from a descriptive epidemiological study of drug use in residential homes for elderly people were analysed. Of the 1,888 residents included in the study, 797 (42%) received diuretics. Significantly more females than males received diuretics (ratio of 3.1:1) and recipients were significantly older than non-recipients. They received a total of 894 diuretics of which 413 (46.2%) were loop diuretics, 168 (18.6%) were thiazide diuretics and 278 (31.2%) were potassium-sparing diuretics. The single most frequently used diuretic was frusemide. Diuretics were involved in 209 potential drug-drug interactions which represented 41% of the total number of potential drug-drug interactions. Of these interactions 19 were considered to be potentially highly clinically significant.

Aged↗
PubMed1988

The use of digoxin in 55 residential homes for elderly people.

Data relating to the use of digoxin from a descriptive epidemiological study of drug use in residential homes for elderly people were analysed. Of the 1,888 residents in the study homes, 212 were receiving cardiac glycosides. The ratio of females to males who received cardiac glycosides was 2.8:1; however, this was not statistically significant as it reflected the overall population. The median age of recipients of cardiac glycosides was 85.2 years and they were significantly older than non-recipients (P less than 0.001). The cardiac glycosides were almost exclusively prescribed as digoxin, the median dose was 125 micrograms with a range of 62.5 to 250 micrograms, and the median duration of treatment was 2.3 years, range less than 0.1 to 10.1 years. Digoxin was involved in a total of 152 potential drug interactions, 12 of which were potentially highly significant clinically.

Aged↗
PubMed1988

Use of hypnotic medicines by elderly people in residential homes.

Data relating to the use of hypnotic medicines from a descriptive epidemiological study of drug use in 55 residential homes for elderly people were analysed. Of the 1888 residents included in the study, 435 (23.0%) were receiving a total of 448 hypnotic medicines. There was preferential prescribing of short-acting benzodiazepines but long-acting benzodiazepines represented 31.7% of all hypnotic drugs prescribed. The median duration of treatment with temazepam was 0.8 years and with nitrazepam 2.5 years. The proportion of residents receiving hypnotic medicines in each home varied from 3.6% to 60.0% with a median of 24.1%. This study indicates a need for general practitioners to review their prescribing of hypnotic medicines for elderly people, paying particular attention to the duration of treatment.

Aged↗
PubMed1987

Comparison of measured and calculated internal absorbed doses in a heterogeneous phantom.

The experimental validity of the MIRD (Medical Internal Radiation Dose Committee of the Society of Nuclear Medicine) internal-dose calculations was investigated. Internal radiation doses were measured in a phantom representing the MIRD mathematical phantom using a newly developed volumetric tissue-equivalent dose meter that could be moulded to reproduce the geometry of the phantom's mathematical organs. The MIRD Monte Carlo computer code ALGAM was adapted to simulate the experimental conditions and was run for each calculation with 60,000 photon histories. The experimental data and the theoretical calculations were compared for different combinations of six source organs and seven target organs using 60Co as the source of radiation. The results of this comparison indicated agreement between measured and calculated doses when the uncertainties associated with both techniques are considered. However, statistical analysis of the data also gave an indication that the Monte Carlo method might overestimate the internal absorbed doses since the agreement with the experimental data was found to be in one direction.

Cobalt Radioisotopes↗
PubMed1987

The impact of an isotopic effect on the interpretation of bioassay data for Pu.

A review of the aggregate recoil phenomenon and its potential influence on transfer rates of 238PuO2 and 239PuO2 across the human alveolar wall indicated a significant difference between these two isotopic compounds. Transfer rates were determined in in-vitro experiments and the ratio of the transfer rates for 238Pu to 239Pu was approximately 140 (Ry82). Calculations were performed to assess the importance of this finding on the internal dosimetry of insoluble 238Pu, using methods and models recommended by the International Commission on Radiological Protection (ICRP). It was found that the committed dose equivalent per unit intake was not influenced by the transfer rate from the pulmonary compartment to blood.

Administration, Inhalation↗
PubMed1987

Survey of remedies held and dispensed in residential homes for the elderly.

From a survey of drug use in 55 residential homes for the elderly it was found that a total of 365 medicines comprising 114 different products were held and dispensed by the homes. Of these 43 (12%) were prescription-only medicines. The most frequently held therapeutic groups were analgesics (23% of all remedies held), laxatives (22%) and antacids (14%). It is recommended that a formulary of remedies held and dispensed in residential homes should be introduced in order to rationalize their use.

Aged↗
PubMed1984

An improved volumetric dosimeter for internal dose verification.

The need for a volumetric dosimetry system for use in experiments to verify internal dosimetry calculations has been stressed previously. Such a system, consisting of a mixture of paraffin, tetrachlorobenzene and LiF TLD-100, has been developed at our institute. The dosimeter is essentially tissue equivalent and may be molded easily into any shape. Fabrication procedures and dosimeter-response characteristics of the system are presented. Results indicate no influence of the organic materials on the response of the TLD-100.

Chlorobenzenes↗
PubMed1983

Radon-222 and progeny measurements in "typical" East Tennessee residences.

Modified Wrenn chambers for continuous monitoring of 222Rn, featuring several improvements including a computer-assisted electronics package, have been developed at the Oak Ridge National Laboratory. A field test of these instruments was conducted by placing them in the homes of staff members. Field testing was conducted in seven houses for periods ranging from 4 to 18 days. During this testing period, the 222Rn concentration in these houses was monitored continuously. Radon-222 concentrations in the basements of three of the seven houses were in excess of 100 Bq/m3 almost continuously. One residence had instantaneous concentrations approaching 1000 Bq/m3. Samples of soil and building materials from these residences indicated that 226Ra concentrations were in the normal range (40 Bq/kg). Radon progeny measurements were made in five of these houses on a "typical" day. Results obtained were as follows: for basements, a geometric mean of 0.016 WL (geometric S.D. of 2.9); for upper floors a geometric mean of 0.014 WL (geometric S.D. of 2.9). This paper summarizes the results obtained in the field test.

Air Pollutants, Radioactive↗
PubMed1982

Estimates of absorbed energy in trabecular bone due to beta-particles or electrons.

A computer code, DAB-BE, has been written which can be used to calculate the absorbed energies of beta particles or electrons deposited inside human trabecular bone. The radiation source geometry can be either uniformly distributed in the whole bone or located at a fixed point inside the bone. Bremsstrahlung effects are not considered in these calculations. Results are presented and discussed for six monoenergetic sources of electrons distributed uniformly in a mathematical representation of the arm. In addition, a fixed point source configuration of 1.0 MeV monoenergetic electrons was studied.

Bone and Bones↗