Radio frequency pulse angle phase setting method and circuit thereof

Abstract

In the present invention, transposition and complementing for envelope signal can be achieved by utilizing trigonometrical function transform when 90 degree, 180 degree and 270 degree set for carrier right angle phase is changed-over to zero degree phase so that problem which there is no function of right angle phase and no function of processing ability for carrier output in some synthesizers of single chip direct digital frequency type can be solved.

Description

field of invention [0001] The invention relates to a method and a circuit for setting a radio frequency (RF) pulse phase in a magnetic resonance imaging (MRI) system. Background technique [0002] In the MRI system, RF pulses modulated in the following form are used (assuming that the initial phase is 0, the same below): [0003] a(t)cos(ωt+φ)+b(t)sin(ωt+φ)………(1) [0004] Among them, a(t)+jb(t) is the complex envelope signal, cos(ωt+φ)+j sin(ωt+φ) is the complex carrier signal, ω is the RF pulse carrier frequency, and φ is the RF pulse carrier phase. In the MRI imaging sequence (sequence), the right-angle phase setting is often used, that is, φ is set to 0°, 90°, 180°, 270°. [0005] When using a direct digital frequency synthesizer (DDS) to generate RF pulses, there are usually only 1 / 4 cycle cos and sin tables in the DDS, and a complete cycle can be output using symmetry. In this RF pulse generation method, the following trigonometric transformation is used: [0006] c...

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Problems solved by technology

[0014] The object of the present invention is to provide a method, which can solve the problem of using a single-chip direct digital synthesizer (DDS) in an MRI system, and this type of DDS chip has neither a right-angle phase setting function nor an external setting for a right-angle phase setting. When setting up the interface, the problem of setting the right-angle phase for the RF pulse

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