Biomedical subjects
Publications and source records attributed to D Tomasi.
An application of the target field method to the design of shielded biplanar gradient coils for magnetic resonance imaging electromagnets is presented. Some specific cases are studied, and optimized geometries are proposed for the axial and transverse gradient coils that eliminate the third- and minimize the fifth-order terms in the magnetic field expansion.
This work presents an approach for fast optimization of gradient coils, using the simulated annealing method. The shielding condition derived from a target field method and the analytical evaluation of the fields produced by simple geometries were used to reduce the computing time. This method is applied to the optimization of a shielded biplanar gradient coil set. Efficiency, inductance, and homogeneity of the gradient fields produced by the optimized geometries were studied as a function of the number of wires, for the longitudinal and transverse gradient coils. A prototype of the gradient set was made to test the proposed design method. The resulting experimental values of coil efficiency, inductance, field linearity, and shielding performance exhibit good agreement between theory and experiment.
A simple method for imaging the magnetic field produced by arbitrary current distributions is presented. The method is based on the use of a phase reference image and can be easily adapted to any standard magnetic resonance imaging scanner. Examples are given to application to gradient coil characterization and quantitative field measurements.
We present a method to obtain MRI amplitude images that can picture the magnetic field due to arbitrary shaped magnetized objects. The method employees the gradient recalled echo sequence and two sets of data obtained in separate experiments, one of which provides a phase reference image making it possible to eliminate the effect of the B0 field inhomogeneities. The final magnitude images have a good signal-to-noise even at low fields, and provide qualitative as well as quantitative information about the magnetic field produced by the ferromagnetic object. As an example the method is applied to study the field produced by a small metal piece in a 500-G scanner, and the experimental results are compared with numerical simulations. Copyright 1998 Academic Press.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
143 older than 18 years epileptic patients have been considered under the concers of their driving licence. The 33,5% of them was already in hold it. Epilepsy was under different clinical forms. The majority of the subjects would suffer from generalized primary suizures, otherwise from partial fits, either elementar or complex. Subjects who already had the licence (37 over 75 men and 15 over 68 women) were presenting most scanty crisis, or since one year had non suffered from any at all. The frequency of crisis was very low for all the patients who had presented epilepsy before beingin permitted to drive; no question had been raised for them. Subjects without licence (25 men over 42 and 18 women over 53) had not been permitted to drive because of their illness. This group was mainly composed by patients either suffering from epilectic cerebropaty from very frequent fits, or from both. It is maintained as reasonable that italian laws conform to those within other E.E.C. countries for what concerns driving licence for epileptics; these patients, whether controlled, are assumed as well capable as accountable in mastering their condition, even when driving.