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Biomedical subjects

D W Anderson

Publications and source records attributed to D W Anderson.

At least 109 records · Page 6Linked to original sources
PubMed1985

Prevalence of Parkinson's disease in the biracial population of Copiah County, Mississippi.

A door-to-door survey of major neurologic disorders was conducted in the essentially biracial population of Copiah County, MS, using a pretested screening questionnaire. All those suspected of having Parkinson's disease were requested to have a neurologic examination by board-certified neurologists. The study also included those living in institutions. The prevalence of Parkinson's disease (age 40+) was 347 per 100,000 inhabitants. No substantial differences in the age-adjusted prevalence ratios by race or by sex were found in the population studied. Age-specific prevalence ratios for Parkinson's disease increase with advancing age. Over 40% of identified cases were newly diagnosed during the study.

Adult↗
PubMed1985

Dependence of magnetic resonance image (MRI) intensity values on relaxation times, pulse intervals and other signal attenuation factors.

Magnetic resonance image (MRI) pixel intensities were investigated using a phantom containing several uniform size chambers filled with solutions of known relaxation times, as well as head scans of patients and volunteers. Intensities were measured with a variety of pulse intervals typically used for imaging with spin echo, (SE) and inversion recovery (IR) sequences at 0.15 Tesla using the back projection (R-THETA) method, and at 0.27 Tesla using the 2-dimensional Fourier transform (2DFT) technique. The results were compared with the calculated dependence of MRI signal intensity on relaxation times and pulse interval parameters using the well known functions containing exponential forms. The experimental and the calculated pixel intensity time dependence did not always agree. We infer that factors other than the conventional functions for T1 and T2 signal decay are important. These factors may include the attenuation of the radiofrequency (RF) signals through inhomogenious lossy dielectric materials (e.g., tissues and organs), the location (coordinate) of the portion of the sample to be imaged relative to the RF coils, and the timing and amplitude of gradient pulses relative to the RF input and the detected signals. The flow velocity and diffusions are also important determinants of the signal from blood vessels and body fluids. We point out the necessity for further investigation toward more comprehensive understanding of MRI intensities.

Adenoma↗
PubMed1984

Significance of initial "performance status" in patients receiving halfbody radiation.

The excellent palliative value of halfbody radiation is well documented. The optimum time to use this modality for palliation of symptoms is unclear. Our department treated 44 evaluable patients with upper and lower halfbody radiation. Stratification according to a modified Karnofsky performance scale revealed an 86% response with a notable increase in median duration of survival in those patients exhibiting an initial performance scale of -1. The optimum benefit from halfbody irradiation is derived when administered at the earliest indicated time.

Female↗
PubMed1984

Prevalence of cerebral palsy in the biracial population of Copiah County, Mississippi.

As part of a door-to-door survey of major neurological disorders, the prevalence of cerebral palsy was ascertained in the institutionalized and non-institutionalized biracial population of Copiah County, Mississippi. The over-all prevalence ratio was 212 per 100,000 inhabitants. For whites, as for blacks, males had a higher prevalence ratio than females. For both sexes, blacks had a higher prevalence ratio, but the race difference was not striking. Prevalence ratios declined with age. Other findings are presented on clinical features and degree of disability.

Adolescent↗
PubMed1984

Paranasal sinus malignancy--a retrospective analysis of treatment methods.

A retrospective analysis has been made of all cancers of paranasal sinuses seen at the Cancer Control Agency in Vancouver during the years 1970 to 1978. The overall crude five year survival for all cases (49) was 46%. A combined treatment using irradiation and surgery in selected cases generated a five year survival rate of 74.4% as compared to 42.1% in cases receiving irradiation alone. The clinical presentation, staging, and the need for the individualization of treatment methods based on a realistic knowledge of the pathological extent of the disease are discussed.

Adenocarcinoma↗
PubMed1984

Technical artifacts in magnetic resonance imaging.

Various artifacts of Magnetic Resonance Imaging (MRI) typically associated with currently available imaging techniques such as projection reconstruction and two-dimensional fourier transform (2D-FT) are described and illustrated. Examples of MRI artifacts were obtained with an imaging unit with a super conducting magnet operated at .15 Tesla and .27 Tesla with corresponding proton resonance frequency of 6.4 MHz and 11.25 MHz. The .15 Tesla images were obtained using projection reconstruction and the .27 Tesla using the 2D-FT method. Instrument related artifacts include those due to direct current (DC), projection, gradient offset, active shimming, phase encoding, and pulse sequencing. Other often encountered artifacts are related to the patient. These include those due to motion, ferromagnetic effect, and tissue contents. The cause of these artifacts and how (if possible) they may be eliminated or minimized is discussed.

Diagnostic Errors↗
PubMed1984

Focused hyperthermia with a magnetic resonance imaging (MRI) unit and an interstitial grounded probe.

The feasibility of using a commercial magnetic resonance imaging (MRI) scanner to do either imaging or hyperthermic treatment was demonstrated. Radiofrequency (RF) induced focal heating of phantoms and animal tissues was performed using a MRI scanner as the RF power source and a grounded interstitial probe as a device to produce hyperthermia via eddy current convergence. In the therapeutic mode, a pulse width of 900 microseconds and interval of 50 ms were used to give 2% duty cycle (closest simulation to continuous wave (CW) mode without bypassing imaging filters). Temperature in the vicinity of the grounded probe was measured with a field nonperturbing fluoroptic probe. Temperatures increased 4.5 degrees C in 5 minutes in a dielectrically uniform phantom, 3.1 degrees C in 6.7 minutes in rats' leg muscles, and 5.0 degrees C in 6.0 minutes in rats' peritoneum. The MRI of the phantom with the grounded probe and the fluoroptic probe was obtained using spin echo sequences. The potential advantage of this approach is visualization of deep-seated tumors and hyperthermic treatment with minimal modification of the MRI scanner.

Animals↗
PubMed1984

The tuning fork--an essential instrument in otologic practice.

Two groups of people are critical of the tuning fork--those who have never used them and those who do not know how to use them. The tuning fork correctly used is still a dependable method of diagnosing conductive hearing loss and invaluable in the diagnosis of unilateral total sensorineural hearing loss. The degree of conductive loss can be estimated by using tuning forks of 256 through 1024 frequency. These statements are based on the results of this study in which tuning fork tests were performed on a series of patients who subsequently underwent complete otologic examination and audiometry. The method of tuning fork use, the value particularly in the diagnosis of conductive hearing loss, and the tuning fork's limitations are discussed.

Audiometry↗
PubMed1983

Accelerator room photoneutron and photon background measurements using thermoluminescent dosimeters.

Photoneutron dose equivalents and photon doses in the treatment room of a clinical linear accelerator were measured with sets of isotopically enriched LiF thermoluminescent dosimeters and a moderating sphere. Dosimeter neutron calibrations with 252Cf sources were repeated many times during the extended series of measurements because the 6LiF dosimeter sensitivity increased with successive neutron irradiations. Expressed as a fraction of the primary bremsstrahlung beam dose at maximum, the photoneutron background was 2.04 +/- 0.05 mrem/rad (10(-3) Sv/Gy) at 1 m lateral to beam center in the patient midplane at 25 MV. The fraction of this result due to thermal neutrons was found to be only about 2%. The photon background dose was 2.98 +/- 0.04 mrad/rad (10(-3) Gy/Gy). The photoneutron dose equivalent per unit primary dose was found to be nearly independent of the collimator size used but increased by 40% when the bremsstrahlung endpoint energy was increased from 20 to 35 MeV with no change in flattening filters.

Background Radiation↗
PubMed1982

Prevalence of essential tremor. Results from the Copiah County study.

This investigation determined the prevalence of essential tremor in a US population. The findings were derived from a large-scale morbidity survey conducted in a rural, biracial Mississippi county (Copiah County). Both the household and the institutionalized populations of the county were included. Results were limited to persons 40 years old or older. Prevalence ratios were higher for women than for men and were higher for whites than for blacks. Age-specific prevalence ratios generally increased with age. The overall prevalence ratio was 414.6 per 100,000 inhabitants.

Adult↗
PubMed1982

Regression and differentiation of neuroblastoma tumors in mice treated with differentiating agents--prostaglandin E1 and a phosphodiesterase inhibitor, RO 20-1724.

Prostaglandin E1 (PGE) and d, 1-4-(3-butoxy-4-methoxybenzyl)-2-imidazolidinone (RO 20-1724, an experimental cyclic nucleotide phosphodiesterase inhibitor) cause cell death and cyclic AMP-mediated differentiation of murine neuroblastoma (NB) (cell line C-1300) cells in vitro. We report, for the first time, that these agents can be used in vivo to cause regression of NBs in A/Jax mice. These drugs were also able to slow the growth of primary tumors, prevent metastases, and cause morphological differentiation of tumors. The similarity of the response of human and mouse NB cells to differentiating drugs indicate that these agents have the potential to replace or support conventional chemotherapy in treatment individualized to NB. The mouse model of NB provides an excellent means to study the effectiveness of alternative drug therapy in vivo.

4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone↗