BackgroundIntensity modulated radiotherapy for head and neck cancer necessitates accurate definition of organs at risk (OAR) and clinical target volumes (CTV). This crucial step is time consuming and prone to inter- and intra-observer variations. Automatic segmentation by atlas deformable registration may help to reduce time and variations. We aim to test a new commercial atlas algorithm for automatic segmentation of OAR and CTV in both ideal and clinical conditions.MethodsThe updated Brainlab automatic head and neck atlas segmentation was tested on 20 patients: 10 cN0-stages (ideal population) and 10 unselected N-stages (clinical population). Following manual delineation of OAR and CTV, automatic segmentation of the same set of structures was performed and afterwards manually corrected. Dice Similarity Coefficient (DSC), Average Surface Distance (ASD) and Maximal Surface Distance (MSD) were calculated for “manual to automatic” and “manual to corrected” volumes comparisons.ResultsIn both groups, automatic segmentation saved about 40% of the corresponding manual segmentation time. This effect was more pronounced for OAR than for CTV. The edition of the automatically obtained contours significantly improved DSC, ASD and MSD. Large distortions of normal anatomy or lack of iodine contrast were the limiting factors.ConclusionsThe updated Brainlab atlas-based automatic segmentation tool for head and neck Cancer patients is timesaving but still necessitates review and corrections by an expert.

Quadratic divergencies which lead to the usual fine-tuning or hierarchy problem are discussed in top condensation models. As in the Standard Model a cancellation of quadratic divergencies is not possible without the boson contributions in the radiative corrections which are absent in lowest order of an 1/N c -expansion. To deal with the cancellation of quadratic divergencies we propose therefore an expansion in the flavor degrees of freedom. In leading order we find the remarkable result that quadratic divergencies automatically disappear. *

arXiv:hep-ph/9503337v2 21 Sep 1995 MPI-PhT/95-18/rev TUM-HEP-216/95/rev LMU-05/95/revAbstract Predictions for the ratio M W /m t arise in top condensation models from different methods. One type of prediction stems from Pagels-Stokar relations based on the use of Ward Identities in the calculation of the Goldstone Boson decay constants and expresses M W in terms of integrals containing the dynamically generated mass function Σ t (p 2 ). Another type of prediction emerges from the renormalization group equations via infrared quasi-fixed-points of the running top quark Yukawa coupling. We demonstrate in this paper that in the limit of a high cutoff these two methods lead to the same predictions for M W /m t and M W /M H in lowest loop order.

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