Picosecond lifetimes in 46 V and 46 Ti were determined using the recoil distance Doppler-shift technique with a plunger device coupled to a setup of five HP Ge detectors enhanced by one EUROBALL CLUSTER detector. The experiment was carried out using the 32 S( 16 O,pn) reaction at 38 MeV at the Cologne FN TANDEM facility. The differential decay curve method in coincidence mode was employed to derive lifetimes for five excited states in each nucleus. The resulting E2 transition probabilities are compared with existing shell model calculations and a comparison within the Tϭ1 isospin triplet is given. Absolute E1 strengths of the 2 Ϫ decay in 46 V are discussed.The investigation of NϭZ nuclei is an exciting topic in nuclear structure physics, to which a lot of experimental and theoretical work has been devoted recently. Self-conjugate nuclei are symmetric with respect to the isospin degree of freedom and allow a sensitive testing of the isospin symmetry. This symmetry leads to selection rules, e.g., E1 transitions between low lying states with Tϭ0 character are strictly forbidden. The only way to enhance E1 strengths between such states is to assume an admixture of Tϭ1 components of the wave function, caused by the Coulomb interaction or by isospin violating parts of the strong interaction.The determination of isospin mixing matrix elements via lifetime measurements is of special interest in odd-odd N ϭZ nuclei with valence particles in the f 7/2 shell. In 46 V, much interesting data have been accumulated recently ͓1-6͔. A very peculiar finding was the isospin forbidden 2 Ϫ →1 ϩ transition with a relative E1 strength six times stronger than the strength of a competing allowed one with ⌬Tϭ1 ͓1͔. In order to achieve a better comparison between allowed and forbidden E1 transitions, it is important to determine ͑more and͒ absolute transition probabilities in this nucleus. The present work reports on the decay properties of the 2 1 Ϫ ,T ϭ0 state and explains the observed relative E1 strengths.Aside from this, a comparison with 46 Ti, the isobaric analog partner of 46 V, is presented. In the Tϭ1 triplet the reduced E2 matrix elements have a linear dependence upon T z , which follows from general arguments based on the ideas of isospin symmetry ͓7͔, provided that isospin is a good quantum number. Precise B(E2;2 1 ϩ →0 ϩ ) values provide a stringent test to this theoretical relation. The new data are in better agreement with the theoretical description than a previous value.In 46 V recent model calculations in the full p f shell without any truncation for the positive parity states describe the experimental level order and branching ratios well ͓1͔. Nevertheless, reliable data on transition probabilities are necessary for an overall comparison of experimental data with shell model calculations. Despite its relevance such information is still scarce.We performed a recoil distance Doppler-shift ͑RDDS͒ experiment with the Köln coincidence plunger device ͓8͔ at the FN TANDEM facility at the University of Cologne. Excited states ...

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Radiation exposure to the patient during CT is relatively high, and it is therefore important to optimize the dose so that it is as low as possible but still consistent with required diagnostic image quality. There is no established method for measuring diagnostic image quality; therefore, a set of image quality criteria which must be fulfilled for optimal image quality was defined for the retroperitoneal space and the mediastinum. The use of these criteria for assessment of image quality was tested based on 113 retroperitoneal and 68 mediastinal examinations performed in seven different CT units. All the criteria, except one, were found to be usable for measuring diagnostic image quality. The fulfillment of criteria was related to the radiation dose given in the different departments. By examination of the retroperitoneal space the effective dose varied between 5.1 and 20.0 mSv (milli Sievert), and there was a slight correlation between dose and high percent of "yes" score for the image quality criteria. For examination of the mediastinum the dose range was 4.4-26.5 mSv, and there was no significant increment of image quality at high doses. The great variation of dose at different CT units was due partly to differences regarding the examination procedure, especially the number of slices and the mAs (milli ampere second), but inherent dose variation between different scanners also played a part.