Picker International, Inc.

Koninklijke Philips Corporation N.v.

Philips Medical Systems (cleveland), Inc.

Francis H Bearden

Gordon D DeMeester

Haiying Liu

G Neil Holland

David Leslie Foxall

Dee H Wu

Paul M Margosian

Kenneth S Denison

Christopher K Anand

E Mark Haacke

Xecheng Liu

A method of MRI includes supporting a subject in an examination region of an MRI scanner, and setting up a spin system with a net magnetization. An inversion pulse is applied which inverts the magnetization of the spin system in a selected volume of the subject. As the magnetization re-grows, a first set of raw data is generated by acquiring MR signals from a series of regions within the selected volume. For the first set of raw data, the series of regions are acquired in a first temporal order with respect to the inversion pulse. The inversion pulse is re-applied, and as the magnetization re-grows, a second set of raw data is generated in similar fashion to the first. However, for the second set of raw data, the series of regions are acquired in a second temporal order with respect to the inversion pulse. The second temporal order is different from the first temporal order. From the first and second sets of raw data, respectively, first and second sets of complex image data are generated. A complex phase correction factor is then determined and applied to one of, or both, the first and second sets of complex image data to thereby phase match the same. A combined image is generated via a pixel by pixel complex combination of the phase matched first and second sets of complex image data.

Combination of fluid-attenuated inversion-recovery complex images acquired using magnetic resonance imaging

A non-rectangular central kernel ( ) of magnetic resonance image data is collected and stored in an acquired data memory ( ). A non-rectangular peripheral portion ( ) of magnetic resonance image data adjacent the central kernel ( ) is collected and stored in the acquired data memory ( ). A phase correction data value set ( ) is generated from at least a portion of the central and peripheral data value sets. A synthetic conjugately symmetric data set ( ) is generated ( ) from the peripheral data set and phase corrected ( ) using the phase correction data value set ( ). Unsampled corners of k-space are zero filled. The central, peripheral, and conjugately symmetric data sets are combined ( ) to form a combined data set. The combined data'set is Fourier transformed ( ) to form an intermediate image representation ( ), which may be exported for display ( ) or used for a further iteration. In this manner, a significant amount of data in a central region of k-space that contributes most strongly to the resultant image is collected while significantly reducing data acquisition time.

Two-dimensional phase-conjugate symmetry reconstruction for 3d spin-warp, echo-planar and echo-volume magnetic resonance imaging

A method of magnetic resonance imaging includes subjecting a number of regions of an object being imaged to a magnetic resonance calibration pulse sequence. Each calibration pulse sequence generates a single calibration echo. Each of the calibration echoes are collected and therefrom correction factors are generated. Thereafter, the method includes subjecting the regions of the object being imaged to a plurality of magnetic resonance imaging pulse sequences. Each of the imaging pulse sequences generates a single imaging echo. Each imaging echo is collected into k-space as a plurality of sampled data points. The plurality of sampled data points are adjusted in accordance with the correction factors as each imaging echo is collected into k-space.

Prescan calibration of spatially dependent data errors in single echo sequences

A transmitter (24) and gradient amplifiers (20) transmit radio frequency excitation and other pulses to induce magnetic resonance in selected magnetic dipoles and cause the magnetic resonance to be focused into a series of echoes (66) at each of a plurality of preselected echo positions following each excitation. A receiver (38) converts each echo into a data line. Calibration data lines having a close to zero phase-encoding are collected and used to generate correction parameters (102) for each of the echo positions. These parameters include relative echo center positions (96) and unitary complex correction vectors (106). The calibration data lines for each of the preselected positions are one-dimensionally Fourier transformed (82) and multiplied (90) by the same complex conjugate reference echo (80). These data lines are then inverse Fourier transformed (92) to generate an auxiliary data array (94). A relative echo center position is computed (96) which represents a fractional shift of the true center relative to the reference echo. A complex sum is computed (104) from the relative echo center position and normalized (106) to generate a unitary correction vector. The phase-correction parameters are used to phase-correct (116) imaging data lines. The phase-corrected imaging data lines are sorted (122) to build an image plane which is one-dimensionally Fourier transformed (128) in the phase-encoding direction to produce a final corrected image (130) for display on a monitor (134).

Method for magnetic resonance spin echo scan calibration and

Magnetic resonance imaging data lines or views are generated and stored in a magnetic resonance data memory (56). The number of views or phase encode gradient steps N along each of one or more phase encode gradient directions is selected (70) to match the dimensions of the region of interest. A discrete Fourier transform algorithm (94) operates on the data in the magnetic resonance data memory to generate an image representation for storage in an image memory (96). Unlike a fast Fourier transform algorithm which requires a.sup.N views or data lines, where a and N are integers, the discrete Fourier transform has a flexible number of data lines and data values which can be accommodated. More specifically to the preferred embodiment, the discrete Fourier transform operation is performed by a CHIRP-Z transform or a Goertzel's second order Z-transform which can accommodate any number of data lines or values.

Discrete Fourier transform imaging

An incomplete set of three dimensional magnetic resonance data is collected and stored in acquired data memory (40). The incomplete data set is complete with respect to first and second directions and incomplete with respect to a third direction. However, the acquired data set has data along the third direction between .+-.n central values and half the remaining values. One dimensional inverse Fourier transforms (64, 66) are performed with respect to the first and second directions to create an intermediate data set (68). A phase correction array or plurality of phase correction vectors p(r) are generated from the intermediate data and stored in a phase correction memory (82). A symmetric data set (100) is created as the complex conjugate of the intermediate data set. The intermediate and symmetric data sets are one dimensionally inverse Fourier transformed (96, 104) with respect to the third direction one vector at a time to produce vectors of first and second complex image arrays (f.sub.A, f.sub.S) corrected (96, 108) with the corresponding phase correction vector, and combined (110) into a line of a resultant three dimensional image representation (112).

Three dimensional volume imaging with conjugate symmetrization

Hybrid fast scan magnetic resonance imaging is performed by using, for example, both a two dimensional Fourier transform (2DFT) method using phase encoding prior to data collection and an echo planar technique which phase encodes by using an oscillating gradient during data collection. In this hybrid imaging, the amplitude of the oscillating gradient determines the time savings achieved in imaging. The hybrid scan has particular application for medical diagnostic imaging since it is advantageous that such imaging be conducted as rapidly as possible.

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Twinsburg, OH, United States of America

Francis H Bearden