5245306 Actively shielded magnet for magnetic resonance apparatus

✍ Scribed by Johannes A Overweg

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 115 KB
• Volume: 12
• Category: Article
• ISSN: 0730-725X
• DOI: 10.1016/0730-725x(94)92272-1

✦ Synopsis

New Patents circuit. Before the beginning of each read-out sequence, the capacitor is charged to a higher voltage than would be necessary to produce a pure sine oscillation during the read-out sequence. The rise time of the gradient pulse thus produced is less than one-fourth of the duration of the sinusoidal oscillation before the zero-axis crossing, and the decay time is less than onefourth of the duration of the sinusoidal oscillation after the zero-axis crossing. Additionally, a constant part of each gradient pulse is nonresonantly generated by a gradient amplifier. Only the steep parts of the oscillation of the resonant circuit are used for the rising and trailing edges, whereas the flattened part of the sine oscillation is cut off. The rising and trailing edges can thus be noticeably shortened, so that a greater range for the constant gradient value, which can be equidistantly sampled in the kspace is available for the signal evaluation.