To acquire anatomical information we are using a Rad-Icon Shad-o-Box X-ray detector that provides a field of view of 5 cm × 10 cm. The gamma camera has a 10 cm diameter active area and can be used for 125I, 99mT and 111In radionuclide imaging. For the gamma camera we use is a Hamamatsu position sensitive photomultiplier tube more » coupled to a pixellated NaI(TI) scintillator array with individual crystal elements 1 mm × 1 mm × 5 mm in size and a 0.25 mm septum between each element. Thomas Jefferson National Accelerator Facility and Case Western Reserve University have been collaborating on the development of a planar imaging system which in addition to radiopharmaceutical based functional imaging and x-ray radiography structural imaging also allows for the in vivo bioluminescence imaging thus providing another functional imaging modality. The addition of a third modality is the goal of our instrumentation development. Recently small animal research utilizing nuclear medicine based imaging has been combined with structural anatomical imaging from x-ray radiography providing a powerful tool for animal researchers.
#OID THE TALOS PRINCIPLE IMAGES PORTABLE#
Finally, portable detectors for alpha, BETA, and gamma radiation are described. Their performance is illustrated with the spectrum of Th/sup 229/ and its descendants and the fission spectrum of Cf/sup 252/.
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The theoretical foundation of semiconductor detectors and their radiological characteristics are described. The junction field lies between 10/sup 2/ and 1/sup 4/ v/cm and the response velociiy at 5 x 10/sup 6/ cm/sec, which means that charges are collected in less than 10/sup -9/sec. A potential difference appears and then disappears according to the law, e-/sup t %TT/, where theta = RC which is the product of junction resistance and capacity. If a Ge or Sijunction is placed between electrodes, electrons and holes are rapidly separated by the electric field and collected at opposite parts of the junction. It is of the magnitude 10/sup -5/ to 10/sup -3/ sec. Electrons and holes have the tendency to recombine rapidly, but in an n-type crystal of great purity the life of the charge is longer and depends on more » the number of holes. The mean energy of pair creation is 2.94 ev for Ge and 3.50 ev for Si. The detectors are based on the principle that if a charged particle traverses a semiconductor, it creates a number of electron-hole pairs. The rapid progress made in solid state physics had made it possible to use semiconductors for a new class of radioactive detectors whose accuracy, sensitivity, simplicity, response time, and inexpensiveness compare favorably with conventional detectors. Choosing as a model example a Mo-Ag radiator-spacer pair of materials, we demonstrate that the x-ray transition radiation line can be well resolved with the use of spatial and frequency filtering. Having experimental goals in mind, we have considered also the unwanted effects due to bremsstrahlung radiation, absorption and scattering of radiated photons, detector-related issues, and inhibited coherence of transition radiation due to random deviation of spacing between the layers. We show that one of the main factors in achieving the required resonant line is the absence of the contrast more » of the refractive indices between the spacer and the radiator at the far wings of the radiation line for that purpose, the optimal spacer, as a rule, should have a higher atomic number than the radiator.
![oid the talos principle images oid the talos principle images](https://game-guide.fr/wp-content/uploads/2015/03/TalosLogoHiRes.jpg)
The approach toward choosing radiator-spacer couples for the generation of hard x-ray resonant transition radiation by few-MeV electrons traversing solid multilayer structures for the energies of interest to medicine (30-50 keV) changes dramatically compared with that for soft x-ray radiation. Our research effort is aimed at developing an x-ray source for medical applications, which is based on using low-energy relativistic electrons. We show that a periodic metal-metal multilayer nanostructure can serve as an efficient source of hard x-ray transition radiation.