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Intracellular and extracellular water volumes in the human body have been computed using a sequence of models starting with a linear first order RC circuit (Cole model) and finishing with the De Lorenzo model. This last model employs a fractional order impedance whose parameters are identified using the frequency characteristics of the impedance module and phase, the latter being not unique. While the Cole model has a two octaves frequency validity range, the De Lorenzo model can be used for three decades. A new linear RC model, valid for a three decades frequency range, is proposed. This circuit can be viewed as an extension of the Cole model for a larger frequency interval, unlike similar models proposed by the same authors.

The large signal operation of the bulk acoustic wave (BAW) resonators is characterized by the amplitude-frequency effect and the intermodulation effect. The measurement of these effects, together with that of the small signal frequency characteristic, are used in this paper for the parameter identification of the nonlinear circuit models developed previously by authors. As the resonator has been connected to the measurement bench by wire bonding, the parasitic elements of this connection have been taken into account, being estimated solving some electrical and magnetic field problems.

The Compton camera, in principle, can improve spatial resolution and efficiency with respect to today's PET and SPECT techniques. The optimization of a Compton camera system in terms of efficiency and resolution is a complex multi-parameter problem. The efficiency depends on various detector parameters (material, thickness, positioning, etc.). The influence of these parameters on the image reconstruction is investigated for a conventional reconstruction technique in order to find optimum detector parameters. The case studies are based on a model for a system consisting of a silicon drift detector (electron detector) and a scintillator detector (photon detector). Effects of secondary and background processes were not included in this model. It was found that high-energy gamma sources (300 keV and more) are preferable over lower-energy sources (e.g., 140 keV) commonly used for SPECT. A Si detector as an electron detector and an angular range between 30[degrees] and 80[degrees] is most useful considering the various physical and experimental constraints. Silicon drift detector (SDD) with integrated front-end electronics offers a very good energy resolution due to its low electronics noise. The intrinsic resolution of both detectors influence the overall resolution considerably. A relatively large pixel size of the SDD considered here reduces the number of readout channels, but also limits the intrinsic resolution. The thickness of the electron detector should be chosen in such a way that its effects on efficiency and spatial resolution are balanced. Interdetector distance of at least 15 cm was found to be appropriate for the detector setup considered in this paper. Index Terms--[sup.113m]In, Compton camera, detector parameters, electronic collimation, emission tomography, silicon drift detector.