| 摘要 |
PURPOSE: A method for compensating an MRI system for residual magnetization is provided to maintain a residual magnetization in the MRI system at a constant level which reduces image artifacts by employing a system which adds magnetization reset gradient waveforms with image gradient waveforms, when an image is scanned. CONSTITUTION: An operation of A system is controlled from an operator console(100) which includes a keyboard and control panel(102) and a display(104). The console(100) communicates through a link(116) with a separate computer system(107) that enables an operator to control the production and display of images on the screen(104). The system control(122) includes a set of modules connected together by a backplane(118). These include a CPU module(119) and a pulse generator module(121) which connects to the operator console(100) through a serial link(125). It is through this link(125) that the system control(122) receives commands from the operator which indicate the scan sequence that is to be performed. The pulse generator module(121) operates the system components to carry out the desired scan sequence. It produces data which indicates the timing, strength and shape of the RF pulses which are to be produced, and the timing of and length of the data acquisition window. The pulse generator module(121) connects through a gradient compensation system(129) to a set of gradient amplifiers(127), to indicate the timing and shape of the gradient pulses to be produced during the scan. The pulse generator module(121) also connects to a scan room interface circuit(133) which receives signals from various sensors associated with the condition of the patient and the magnet system. It is also through the scan room interface circuit(133) that a patient positioning system(134) receives commands to move the patient to the desired position for the scan.The gradient waveforms produced by the pulse generator module (121) are compensated by the system(129) and applied to a gradient amplifier system (127) comprised of Gx, Gy and Gz amplifiers.
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