Riccardo Guzzardi

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Measurement of myocardial blood flow by 13NH3 relies heavily on the assessment of both the input function and the variable tissue extraction fraction. In six open-chest dogs, myocardial and arterial 13NH3 activity was measured both by in vitro sampling and by in vivo positron emission tomography (PET). Regional myocardial blood flow was forced to vary in(More)
This paper describes an investigation of some of the important physical characteristics of a whole-body positron tomograph consisting of two rings of bismuth germanate detectors of dimensions 5.6 mm X 30 mm X 30 mm (512/ring). The resolution applicable to in vivo imaging is six mm or more, depending on radionuclide and reconstruction filter and is very(More)
In positron tomographic images, the ability to differentiate closely lying structures, the spillower of activity from a region into adjacent regions and the reduction in apparent isotope concentration in small structures are all dependent on spatial resolution. Resolution in the reconstructed image is affected by (i) detector size, (ii) the spatial sampling(More)
This paper reviews the basic aspects, problems, and applications of Compton imaging including those related to nonmedical applications. The physics and technology at the base of this specific methodology are analyzed and the relative differences and merits with respect to other imaging techniques, using ionizing radiations, are reviewed. The basic Compton(More)
We describe the characteristics of the CAMIRD/III, a software package for the calculation of radiation dose from internally distributed radionuclides. The work concerns the preparation of a revised version of both CAMIRD/II, which uses prestored data of the specific absorbed-energy fraction, and MIRD-S, which uses the precalculated "S" values. Some(More)
To evaluate scatter fraction and scatter pair spatial distribution, experimental methods are generally used. These methods make use of a line source, placed along the FOV axis, inserted in a cylindrical phantom filled with air or water. The accuracy of these experimental methodologies can be tested by the use of a Monte Carlo method. In fact, the simulation(More)
We describe a new device for data acquisition from a gamma camera using an electronic spatial "diaphragm," with variable offset and zooming. The device, mainly applied to cardiac studies, permits selection of the desired part of the field of vision to be digitized and to zoom, before the computer acquisition. The spatial diaphragm spans 0.4-0.9 of the(More)