US 2011/0215804 A1Published application

Magnetic resonance method and system to create an image data set

AssigneeSiemens Aktiengesellschaft

InventorsMichael Deimling, David Grodzki

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Abstract

In a method to create an image data set by operating a magnetic resonance system, at least two phase coding gradients are switched in respective spatial directions, an RF excitation pulse is radiated and a raw data point in a k-space data set belonging to the image data set is read out a predetermined time period after the radiation of the RF excitation pulse. The predetermined time period thereby corresponds to the maximum of a set of a respective minimum time period for each of the at least two phase coding gradients. The minimum time period of the respective at least one of the at least two phase coding gradients is determined depending on the strength of the respective phase coding gradient such that the Nyquist theorem is complied with.

Claims32

Dependent claims

A method to create a magnetic resonance image data set, comprising the steps of:

operating a magnetic resonance data acquisition unit, in which a subject is located, to radiate an RF excitation pulse that causes magnetic resonance signals to be emitted from the subject;
activating at least two phase coding gradients in respective spatial directions that phase code said magnetic resonance signals, each of said at least two phase coding gradients having a gradient strength;
in a readout procedure, reading out said magnetic resonance signals as substantially only one raw data point in a k-space data set representing said magnetic resonance image data, at a predetermined time duration following radiation of said RF excitation pulse;
setting said predetermined time duration as a maximum of a set of respective maximum time periods for each of said at least two phase coding gradients;
setting a minimum time duration TEmin for each of said at least two phase coding gradients dependent on the gradient strength of the respective phase coding gradients in order to comply with the Nyquist theorem;
repeatedly activating said at least two phase coding gradients and radiating said RF excitation pulse and reading out substantially only one raw data point until an entirety of said k-space data set is acquired;
and
setting said minimum time period TEmin for each spatial direction according to:
TE
min
,
i
=
K
i
G
max
,
i
,
wherein i is the spatial direction of the respective phase coding direction, Ki is the gradient moment of the respective phase coding gradient in the i spatial direction, and Gmax,i is the gradient strength of the respective phase coding gradient in the i spatial direction.

18 more elements

A method to create a magnetic resonance image data set, comprising the steps of:

operating a magnetic resonance data acquisition unit, in which a subject is located, to radiate an RF excitation pulse that causes magnetic resonance signals to be emitted from the subject;
activating at least two phase coding gradients in respective spatial directions that phase code said magnetic resonance signals, each of said at least two phase coding gradients having a gradient strength;
in a readout procedure, reading out said magnetic resonance signals as multiple raw data points along a straight spoke proceeding through a center of k-space, in a k-space data set representing said magnetic resonance image data, at a predetermined time duration following radiation of said RF excitation pulse;
setting said predetermined time duration as a maximum of a set of respective maximum time periods for each of said at least two phase coding gradients;
setting a minimum time duration TEmin for each of said at least two phase coding gradients dependent on the gradient strength of the respective phase coding gradients in order to comply with the Nyquist theorem;
repeatedly activating said at least two phase coding gradients and radiating said RF excitation pulse and reading out multiple raw data points along respective spokes until an entirety of said k-space data set is acquired;
and
setting said minimum time period TEmin for each spatial direction according to:
TE
min
,
i
=
K
i
G
max
,
i
,
wherein i is the spatial direction of the respective phase coding direction, Ki is the gradient moment of the respective phase coding gradient in the i spatial direction, and Gmax,i is the gradient strength of the respective phase coding gradient in the i spatial direction.

18 more elements

A magnetic resonance system that creates a magnetic resonance image data set comprising:

a magnetic resonance data acquisition unit;
a computerized control unit configured to operate said magnetic resonance data acquisition unit, in which a subject is located, to radiate an RF excitation pulse that causes magnetic resonance signals to be emitted from the subject;
said control unit being configured to operate said magnetic resonance data acquisition unit by activating at least two phase coding gradients in respective spatial directions that phase code said magnetic resonance signals, each of said at least two phase coding gradients having a gradient strength;
said control unit being configured to operate said magnetic resonance data acquisition unit by, in a readout procedure, reading out said magnetic resonance signals as substantially only one raw data point in a k-space data set representing said magnetic resonance image data, at a predetermined time duration following radiation of said RF excitation pulse;
said control unit being configured to operate said magnetic resonance data acquisition unit by setting said predetermined time duration as a maximum of a set of respective maximum time periods for each of said at least two phase coding gradients;
said control unit being configured to operate said magnetic resonance data acquisition unit by setting a minimum time duration TEmin for each of said at least two phase coding gradients dependent on the gradient strength of the respective phase coding gradients in order to comply with the Nyquist theorem;
said control unit being configured to operate said magnetic resonance data acquisition unit by repeatedly activating said at least two phase coding gradients and radiating said RF excitation pulse and reading out substantially only one raw data point until an entirety of said k-space data set is acquired;
and
said control unit being configured to operate said magnetic resonance data acquisition unit by setting said minimum time period TEmin for each spatial direction according to:
TE
min
,
i
=
K
i
G
max
,
i
,
wherein i is the spatial direction of the respective phase coding direction, Ki is the gradient moment of the respective phase coding gradient in the i spatial direction, and Gmax,i is the gradient strength of the respective phase coding gradient in the i spatial direction.

19 more elements

A magnetic resonance system that creates a magnetic resonance image data set, comprising:

a magnetic resonance data acquisition unit;
a computerized control unit configured to operate said magnetic resonance data acquisition unit, in which a subject is located, to radiate an RF excitation pulse that causes magnetic resonance signals to be emitted from the subject;
said control unit being configured to operate said magnetic resonance data acquisition unit by activating at least two phase coding gradients in respective spatial directions that phase code said magnetic resonance signals, each of said at least two phase coding gradients having a gradient strength;
said control unit being configured to operate said magnetic resonance data acquisition unit by, in a readout procedure, reading out said magnetic resonance signals as multiple raw data points along a straight spoke proceeding through a center of k-space, in a k-space data set representing said magnetic resonance image data, at a predetermined time duration following radiation of said RF excitation pulse;
said control unit being configured to operate said magnetic resonance data acquisition unit by setting said predetermined time duration as a maximum of a set of respective maximum time periods for each of said at least two phase coding gradients;
said control unit being configured to operate said magnetic resonance data acquisition unit by setting a minimum time duration TEmin for each of said at least two phase coding gradients dependent on the gradient strength of the respective phase coding gradients in order to comply with the Nyquist theorem;
said control unit being configured to operate said magnetic resonance data acquisition unit by repeatedly activating said at least two phase coding gradients and radiating said RF excitation pulse and reading out multiple raw data points along respective spokes until an entirety of said k-space data set is acquired;
and
said control unit being configured to operate said magnetic resonance data acquisition unit by setting said minimum time period TEmin for each spatial direction according to:
TE
min
,
i
=
K
i
G
max
,
i
,
wherein i is the spatial direction of the respective phase coding direction, Ki is the gradient moment of the respective phase coding gradient in the i spatial direction, and Gmax,i is the gradient strength of the respective phase coding gradient in the i spatial direction.

19 more elements

Dependencies are inferred from the claim text.