Axis translator for magnetic resonance imaging

• US 4,933,639 A
• Filed: 02/13/1989
• Issued: 06/12/1990
• Est. Priority Date: 02/13/1989
• Status: Expired due to Fees

• Current Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Original Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Inventors: Barker, Bruce R.
• Primary Examiner(s): Tokar, Michael J.
• Application Number:
  US07/310,542
• Time in Patent Office: 484 Days
• Field of Search: 364/754, 364/728.01, 364/841, 364/606, 324/300, 324/307, 324/309, 324/311, 324/312, 324/313, 324/77 K, 128/653
• US Class Current: 324/309
• CPC Class Codes: G01R 33/4833 using spatially selective excitation of the volume of interest, e.g. selecting non-orthogonal or inclined slices
• CPC Class Codes: G01R 33/54 Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console

Abstract

An apparatus and a method to permit virtually any magnetic resonance imaging system to image slices of any orientation by converting its three-channel gradient current demand--a set of three time-varying voltages proportional to the instantaneous currents required in the x, y and z gradient coils--into that required for imaging the chosen plane or volume are provided. The method, which is referred to as axis translation, involves taking the input readout, phase-encoding and slice-selecting gradients from the system'"'"'s host computer and rotating the orientation of these gradients through angles set by the system operator. This is accomplished using a 3×3 analogue matrix which outputs the appropriate imaging demand vector which is thereafter interpreted as current demand in the X, Y and Z coils of the magnetic resonance imaging system in the conventional manner.

Claims

1. A magnetic resonance imaging axis translator comprising:

(a) input means comprising readout, phase-encoding and slice-selecting voltage channels;

(b) a three-by-three analogue matrix vector multiplier having matrix elements for operating upon signals on said voltage channels to effect axis translation;

(c) means for varying said matrix elements to vary the axis translation of signals on said voltage channels; and

(d) output means from said vector multiplier to provide signals which develop current demands in the gradient coils of a magnetic resonance imaging system.

2. A method of axis translation in a magnetic resonance imaging system comprising:

performing a series of locator scans from whose images rotation angles may be measured directly;

receiving input voltages from the MRI system'"'"'s control computer;

equalizing the gain and nulling the input voltage;

equally limiting the slew rate of the input voltages to produce tailored input voltages;

developing a matrix of values which represent attenuation factors defining the axis translation;

applying the attenuation factors to the tailored input voltages to produce tailored and rotated output voltages;

applying an equalizing gain and offset to the tailored and rotated output voltages to produce current demand voltages; and

outputting the current demand voltages to the MRI system'"'"'s eddy current compensation and gradient current sources yielding imaging planes selectably rotated by one, two or three angles.