124 research outputs found
Explicit optimization of plan quality measures in intensity-modulated radiation therapy treatment planning
Conventional planning objectives in optimization of intensity-modulated
radiotherapy treatment (IMRT) plans are designed to minimize the violation of
dose-volume histogram (DVH) thresholds using penalty functions. Although
successful in guiding the DVH curve towards these thresholds, conventional
planning objectives offer limited control of the individual points on the DVH
curve (doses-at-volume) used to evaluate plan quality. In this study, we
abandon the usual penalty-function framework and propose planning objectives
that more explicitly relate to DVH statistics. The proposed planning objectives
are based on mean-tail-dose, resulting in convex optimization. We also
demonstrate how to adapt a standard optimization method to the proposed
formulation in order to obtain a substantial reduction in computational cost.
We investigate the potential of the proposed planning objectives as tools for
optimizing DVH statistics through juxtaposition with the conventional planning
objectives on two patient cases. Sets of treatment plans with differently
balanced planning objectives are generated using either the proposed or the
conventional approach. Dominance in the sense of better distributed
doses-at-volume is observed in plans optimized within the proposed framework,
indicating that the DVH statistics are better optimized and more efficiently
balanced using the proposed planning objectives
QuizzEuropa - et brætspil om et andet Europa
Bliv udfordret på din sammenhængsforståelse for Europas historie, kulturelle mangfoldighed og politiske geografi gennem fokus på regioner frem for nationalstater. Et lærerigt og underholdende bidrag til undervisningen
The Twisted String Vertex Algorithm Applied to the -Twisted Scalar String Four Vertex
Recently an algorithm was found by means of which one can calculate terms at
arbitrary oscillator level in the four-Ramond vertex obtained by sewing. Here
we show that this algorithm is applicable also to the case of -twisted scalars and derive the full propagator for scalars on the Riemann
sphere with two branch cuts. The relation to similar results previously derived
in the literature by other means is discussed briefly.Comment: 18 pages (LaTeX), G\"oteborg ITP 94-
Kreditorekstinksjon ved rettsstiftelser uten rettsvern i bakenforliggende ledd
MasteroppgaveJUS399MAJUR-2MAJU
Ny forskning i grammatik
Many Danish cognition verbs take both indicative and infinitive complements. We examine what the contrast between the two complement types codes. The literature offers two answers. One is that the contrast has to do with coreferentiality: if the cognition verb’s primary argument is coreferential with the primary argument of the complement, the complement tends to be infinitive; if not, the complement must be indicative. The other answer concerns the contrast between propositions and states-of-affairs: the indicative complement designates a proposition, the infinitive complement a state-of-affairs. Corpus studies support both answers. They also support an analysis of indicatives as proposition markers. But infinitives cannot – straightforwardly – be analysed as state-of-affairs markers
Kognitionsverber og kontrasten mellem indikativ- og infinitivkomplement
Many Danish cognition verbs take both indicative and infinitive complements. We examine what the contrast between the two complement types codes. The literature offers two answers. One is that the contrast has to do with coreferentiality: if the cognition verb’s primary argument is coreferential with the primary argument of the complement, the complement tends to be infinitive; if not, the complement must be indicative. The other answer concerns the contrast between propositions and states-of-affairs: the indicative complement designates a proposition, the infinitive complement a state-of-affairs. Corpus studies support both answers. They also support an analysis of indicatives as proposition markers. But infinitives cannot – straightforwardly – be analysed as state-of-affairs markers
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