Efficacy of a dynamic collimator for overranging dose reduction in a second- and third-generation dual source CT scanner

Objectives: The purpose of this study was to assess the efficacy of the renewed dynamic collimator in a third-generation dual source CT (DSCT) scanner and to determine the improvements over the second-generation scanner. Methods: Collimator efficacy is defined as the percentage overranging dose in terms of dose–length product (DLP) that is blocked by the dynamic collimator relative to the total overranging dose in case of a static collimator. Efficacy was assessed at various pitch values and different scan lengths. The number of additional rotations due to overranging and effective scan length were calculated on the basis of reported scanning parameters. On the basis of these values, the efficacy of the collimator was calculated. Results: The second-generation scanner showed decreased performance of the dynamic collimator at increasing pitch. Efficacy dropped to 10% at the highest pitch. For the third-generation scanner the efficacy remained above 50% at higher pitch. Noise was for some pitch values slightly higher at the edge of the imaged volume, indicating a reduced scan range to reduce the overranging dose. Conclusions: The improved dynamic collimator in the third-generation scanner blocks the overranging dose for more than 50% and is more capable of shielding radiation dose, especially in high pitch scan modes. Key points: • Overranging dose is to a large extent blocked by the dynamic collimator• Efficacy is strongly improved within the third-generation DSCT scanner• Reducing th

Invloed van stikstofbemesting en kunstmatige beregening op de landbouwkundige en industriële kwaliteit van verschillende zetmeelaardappelrassen : verslag van de veldproeven KB 9036 en KP 9060 : werkdocument over het derde proefjaar 2000

In 2000 werd in een tweetal veldexperimenten met verschillende stikstof-bemestingstrappen, gecombineerd met al dan niet toepassing van kunstmatige beregening en verschillende zetmeelaardappelrassen, getracht inzicht te verkrijgen in de eigenschappen die bepalend zijn voor de kwaliteit van zetmeelaardappelrassen voor vroege en late oogst en bewaring. Stikstofbemesting had invloed op de kwaliteit van zetmeelaardappelen. Met kunstmatige beregening werd het fosforgehalte in het zetmeel in de fractie kleine knollen van één proef verhoogd. Er waren duidelijke verschillen tussen de zetmeelaardappelrassen (Karakter en Seresta). De rijpheid van de knollen was van invloed op het zetmeelgehalte en het ruw- en winbaar-eiwitgehalte, het aantal en de grootte van de zetmeelkorrels en het fosforgehalte in het zetmeel. Er is bepaald onder welke condities het hoogste uitbetalingsgewicht werd verkregen. Dit rapport beschrijft de resultaten van de aanvullende chemische gewasanalyses en de industriële karakterisering van de knol van de in 2000 uitgevoerde veldexperimenten. In Hoofdstuk 2 worden de opzet van de proeven en de analysebeschrijving beschreven. In Hoofdstuk 3 worden de resultaten gepresenteerd en besproken. Hoofdstuk 4 bevat de conclusies en de aanbevelingen voor de veldexperimenten in 2001

The “Knowledgeable” CT Scanner: Optimization by technological advancements

Optimization of a computed tomography (CT) exam can be challenging, as there is a wide variety in patient characteristics, continuously emerging technologies and the inc

Development of cauliflower and its consequences for cultivation

From a number of cauliflower crops, grown during several years, plant development was related to the environmental conditions (mainly temperature). After transplanting three developmental phases could be recognized: juvenility, curd induction and curd growth, Variation in time of curd maturity was mainly due to a variation in time of curd initiation (morphological transition of the apex). Time of curd initiation was determined by the time on which juvenility (characterized by the number of initiated leaves) ended and temperature during the period after juvenility. Higher temperatures during the period of curd induction delayed curd initiation and increased the total number of initiated foliage leaves of a plant.Curd induction could be affected by a GA 4+7 application, resulting in an advance of curd maturity, especially when curd initiation of a crop was delayed due to high temperature.Curd weight at maturity was reduced if plant weight at the time of curd initiation was low, conditions which enhanced development but reduced growth caused buttoning.Bracting was induced by high temperature, and when ethephon was applied just after all plants within a crop had initiated a curd, bracting incidence was enhanced severely. Genetic differences in sensitivity for bracting induced by ethephon were apparent.Prospects of cultural measures to reduce the variation in time of maturity in relation to rapidly changing environmental conditions are discussed