Purpose: To smooth the scalloped dose pattern that occurs for stepped leaves at a treatment field edge defined by a multileaf collimator.Methods and Materials: Fields with centers shifted slightly in space were superimposed to blur the staggered dose distribution at the field edge.Film dosimetry was used to monitor changes.The dose distribution for a single field position was compared to the distribution for one and three shifts.Three depths were examined and divergent alloy blocks were included in the comparison.Results: The structure that appears at an edge for a single field when leaves are staggered was nearly eliminated when the field was shifted three times to give a total of four different positions.However, shifting the field one time so that two fields were superimposed gave an intermediate result with only slight improvement in the undulating dose distribution.For the four superimposed fields, the 50% isodose pattern converged to a smoothed line running along the center of the original undulating pattern.The 80 and 20% isodoses did not converge to the center of their scalloped patterns.Instead, these isodose lines were spread leaving a larger penumbra width than a divergent alloy block.Conclusions: Shifting and adding fields is an effective method for smoothing the staggered dose distribution that results when the leaves of a multileaf collimator are stepped to form an irregular field pattern.However, the width of the penumbra for the combined fields is wider than the penumbra for a cerrobend block.Multileaf, Penumbra.
Journal Article Modulation of the respiratory depressant effect of ethanol by 5-hydroxytryptamine Get access Alfred A Smith, Alfred A Smith Departments of Psychiatry and Pharmacology, New York Medical College, New York, N.Y. 10029, U.S.A. Search for other works by this author on: Oxford Academic Google Scholar Charles Engelsher, Charles Engelsher Departments of Psychiatry and Pharmacology, New York Medical College, New York, N.Y. 10029, U.S.A. Search for other works by this author on: Oxford Academic Google Scholar Marsha Crofford Marsha Crofford Departments of Psychiatry and Pharmacology, New York Medical College, New York, N.Y. 10029, U.S.A. Search for other works by this author on: Oxford Academic Google Scholar Journal of Pharmacy and Pharmacology, Volume 27, Issue 1, January 1975, Pages 60–62, https://doi.org/10.1111/j.2042-7158.1975.tb09384.x Published: 12 April 2011 Article history Received: 27 September 1974 Published: 12 April 2011
PROMINENT among the symptoms of familial dysautonomia are the manifestations of autonomic dysfunction.1 A disturbance in catecholamine metabolism has been documented by the demonstration of high homovanillic acid and low vanillyl-mandelic acid urinary excretion rates.2 This evidence of pressor catecholamine insufficiency correlates well with the postural hypotension that is consistently found in familial dysautonomia Infusions of relatively small amounts of norepinephrine produce hypertension and patchy erythema,3 suggesting heightened reactivity to sympathetic substances, rather than an excessive production of norepinephrine, as the cause of the clinical symptoms.The abnormality in catecholamine metabolism has now been further explored by measurement of the . . .
Journal Article Reversal by sotalol of the respiratory depression induced in mice by ethanol Get access Kikue Hayashida, Kikue Hayashida Department of Anesthesiology, New York Medical College, New York 10029, USADepartment of Pharmacology, New York Medical College, New York 10029, USA Search for other works by this author on: Oxford Academic Google Scholar Alfred A Smith Alfred A Smith Department of Anesthesiology, New York Medical College, New York 10029, USADepartment of Pharmacology, New York Medical College, New York 10029, USA Search for other works by this author on: Oxford Academic Google Scholar Journal of Pharmacy and Pharmacology, Volume 23, Issue 9, September 1971, Pages 718–719, https://doi.org/10.1111/j.2042-7158.1971.tb08756.x Published: 12 April 2011
Taste perception and discrimination is deficient in patients with familial dysautonomia. No deficiency was evident in parents of children with dysautonomia.
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