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W L Kennedy

Publications and source records attributed to W L Kennedy.

6 recordsLinked to original sources
PubMed1990

Three-dimensional compensating filters using magnetic resonance images.

A technique for making radiation therapy compensators for missing tissue using magnetic resonance imaging (MRI) is presented. Magnetic resonance imaging was chosen for its ability to provide easily visible, accurate patient contours at any treatment angle. Phantom studies, including coronal cuts of a 45-degree phantom, showed that distortion in the magnetic resonance imaging is minimal, but that the image magnification should be checked by placing markers on the patient during the procedure. Water bath studies of 4 MV radiation dose uniformity in a compensated 45-degree phantom exhibited variations of less than 4% from the open beam profile. Errors in constructing and using compensators with this technique are analyzed and simulated.

Filtration↗
PubMed1980

Regulation of red blood cell production by erythropoietin: normal mouse marrow in vitro.

The response of immediate erythroid precursors to timed exposures of erythropoietin (Ep) were investigated by examining the formation of murine erythroid colonies in vitro. At various times after the initiation of normal marrow cultures with Ep, enough anti-erythropoietin serum was added to neutralize the actions of the hormone for the rest of the 48 h culture period in plasma clots. Results show that a significant number of erythroid precursors develop to a mature colony after very short Ep exposures (as little as 18 min), but they account for only about 13% of the total colonies generated when Ep is active for 48 h. Only if Ep is active for more than 6 h do additional colonies form, in direct proportion to the length of the Ep exposure. Maximum erythroid colony production requires prolonged exposure to Ep, and the longer Ep is active, the larger the percentage of erythroid colonies that reach 17 cells or more. The mechanism(s) behind these two effects appear intimately connected. These results suggest the existence of two populations of Ep-responsive cells in the immediate erythroid precursor compartment of mice: (1) A CFUE pool, which is on the verge of commitment into the recognizable erythron, and requires very short Ep exposures for this entry; and (2) a "pre-CFUE" stage which feeds into the CFUE pool in the presence of Ep, and which produces colonies only after longer Ep exposures. It is proposed that the pre-CFUE response to Ep involves 1-2 self-replications before entering the CFUE population.

Animals↗
PubMed1979

Hypothermia.

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Humans↗
PubMed1978

Erythroid colony production in vitro as a function of exposure time to erythropoietin.

The effects of timed exposure to erythropoietin of murine bone marrow cells has been studied in in vitro plasma clot cultures. Erythropoietin was added at the start of the incubation period, and at various times after initiation of the culture an anti-erythropoietin serum was added in an amount adequate to neutralize the erythropoietin. Culture methods were used which allow the transformation of the immediate progenitor stem cell of the recognized erythron, the CFU-E. The incorporation of 59Fe was used as an identity marker for hemoglobin synthesis which allowed the classification of colonies as erythroid in autoradiographs. Brief exposure to the hormone for one to two hours produced activation of about 20% of the control (continuous exposure for the 48 h of culture) value. More protracted exposure to erythropoietin caused the conversion of what appears to be a second population of CFU-E, but even 24 h of exposure was not adequate to cause the maximum activation of CFU-E seen in the control cultures.

Animals↗
PubMed1977

A field expander for patients with retinitis pigmentosa: a clinical study.

An inexpensive, commercially available optical device was tested on 10 patients with retinitis pigmentosa to determine its value as a field expander for scanning and as an aid to mobility. Visual acuity and visual fields were measured with and without the expander, and the patients' subjective responses were monitored by a questionnaire that was administered at regular intervals during a 2- to 4-week period between test sessions. Six of the 10 subjects considered the device helpful in at least 1 important visual task and planned to continue using it.

Adult↗