Magnetic resonance imaging apparatus and method for adjusting excitation region

Patent metadata

Field	Value
Publication number	US-9594135-B2
Application number	US-201013496921-A
Country	US
Kind code	B2
Filing date	Sep 22, 2010
Priority date	Sep 29, 2009
Publication date	Mar 14, 2017
Grant date	Mar 14, 2017

Abstract

In imaging using 2-dimensional selective excitation pulses, regardless of applications thereof, a technique for obtaining a high quality image is provided.
In the technique, a 2-dimensional selective excitation sequence is carried out while changing a coefficient for determining the cylinder diameter of a region excited by the 2-dimensional selective excitation sequence and a time difference for determining an offset position.
The obtained excitation region and a desired region are compared with each other, and the coefficient and time difference with which the obtained excitation region and the desired region match each other are determined to be the optimum ones.
The determination processing may be performed as an initial adjustment, may be performed according to need in each imaging, or may be performed on a per-application basis.

First claim

The invention claimed is:

1. A magnetic resonance imaging apparatus which collects echo signals generated by applying a high-frequency magnetic field and a gradient magnetic field to an object to be examined, which has been placed in a static magnetic field, in accordance with a predetermined pulse sequence and reconstructs an image from the collected echo signals, comprising:
an adjustment unit configured to adjust a profile of an excitation region to be excited by a local excitation sequence, the adjustment unit using (a) a profile adjustment value of the local excitation sequence and (b) a profile adjustment value table in which profile parameters associated with corresponding adjustment values of the local excitation sequence for exciting the excitation region to obtain a specific profile are stored,
a profile adjustment value calculating unit configured to calculate the profile adjustment value of the local excitation sequence, for exciting the excitation region to have an excitation region profile specified by an operator, and
a determination unit configured to determine whether or not a corresponding adjustment value associated with a combination of the profile parameters corresponding to the excitation region profile specified by the operator is stored in the profile adjustment value table,
wherein the profile adjustment value calculating unit calculates the profile adjustment value of the local excitation sequence when the determination unit determines that the corresponding adjustment value associated with the profile parameters corresponding to the excitation region profile specified by the operator is not stored in the profile adjustment value table.

2. The magnetic resonance imaging apparatus according to claim 1 , wherein the profile is adjusted by setting the profile adjustment value calculated by the profile adjustment value calculating unit to the local excitation sequence.

3. The magnetic resonance imaging apparatus according to claim 1 , wherein the adjustment unit comprises a positional adjustment value calculating unit configured to calculate a positional adjustment value of the local excitation sequence for exciting the position of the excitation region based on the excitation region set by an operator, and the position is adjusted by setting the positional adjustment value calculated by the positional adjustment value calculating unit to the local excitation sequence.

4. The magnetic resonance imaging apparatus according to claim 1 , wherein the adjustment unit comprises:
a profile adjustment value table generating unit configured to generate the profile adjustment value table; and
a profile adjustment value extracting unit configured to extract from the profile adjustment value table, at the time of imaging, the profile adjustment values which are stored for each application and correspond to the optimum profile for implementing the relevant application,
wherein the adjustment unit adjusts the profile by setting the extracted profile adjustment values to the local excitation sequence.

5. The magnetic resonance imaging apparatus according to claim 4 , further comprising a profile adjustment value table generating unit configured to store the profile adjustment value calculated by the profile adjustment value calculating unit to the profile adjustment value table.

6. A magnetic resonance imaging apparatus which collects echo signals generated by applying a high-frequency magnetic field and a gradient magnetic field to an object to be examined, which has been placed in a static magnetic field, in accordance with a predetermined pulse sequence and reconstructs an image from the collected echo signals, comprising:
an adjustment unit configured to adjust a position of an excitation region to be excited by a local excitation sequence, the adjustment unit using (a) a positional adjustment value of the local excitation sequence and (b) a positional adjustment value table in which positional parameters associated with corresponding adjustment values of the local excitation sequence for exciting the excitation region at a specific position are stored;
a positional adjustment value calculating unit configured to calculate the positional adjustment value of the local excitation sequence for exciting the excitation region at an excitation region position specified by an operator, and
a determination unit configured to determine whether or not a corresponding adjustment value associated with a combination of the positional parameters corresponding to the excitation region position specified by the operator is stored in the positional adjustment value table,
wherein the positional adjustment value calculating unit calculates the positional adjustment value of the local excitation sequence, when the determination unit determines that the corresponding, adjustment value associated with the positional parameters corresponding to the excitation region position specified by the operator is not stored in the positional adjustment value table.

7. The magnetic resonance imaging apparatus according to claim 6 , further comprising:
a positional adjustment value table generating unit configured to store the positional adjustment value calculated by the positional adjustment value calculating unit to the positional adjustment value table.

8. The magnetic resonance imaging apparatus according to claim 2 , wherein the profile adjustment value includes a coefficient which is related to an amplitude of a gradient magnetic field.

9. The magnetic resonance imaging apparatus according to claim 3 , wherein the positional adjustment value includes a time difference between an application starting time of a high-frequency magnetic field and an application starting time of a gradient magnetic field.

10. The magnetic resonance imaging apparatus according to claim 1 , wherein:
the local excitation sequence is a 2-dimensional selective excitation sequence; and
the excitation region is a cylinder-shaped region.

11. An excitation region adjusting method for adjusting an excitation region to be obtained by executing a local excitation sequence by a magnetic resonance imaging apparatus having a profile adjustment value table in which profile parameters associated with corresponding adjustment values of the local excitation sequence for exciting the excitation region to obtain a specific profile are stored, including:
a determination step of determining whether or not a corresponding adjustment value associated with a combination of the profile parameters corresponding to an excitation region profile specified by an operator is stored in the profile adjustment value table;
a profile adjustment value calculating step of calculating a profile adjustment value of the local excitation sequence for exciting the excitation region to obtain the excitation region profile specified by the operator, when the determination step determines that the corresponding adjustment value associated with the profile parameters corresponding to the excitation region profile specified by the operator is not stored in the profile adjustment value table; and
a profile adjustment value setting step of setting the profile adjustment value calculated by the profile adjustment value calculating step to the local excitation sequence.

12. An excitation region adjusting method for adjusting an excitation region to be obtained by executing a local excitation sequence by a magnetic resonance imaging apparatus having a positional adjustment value table in which positional parameters associated with corresponding adjustment values of the local excitation sequence for exciting the excitation region at a specific position are stored

Assignees

• Goto Tomohiro
• Nishihara Takashi
• Itagaki Hiroyuki
• Hitachi Ltd

Inventors

• Goto Tomohiro
• Nishihara Takashi
• Itagaki Hiroyuki

Classifications

• G01R33/5676

  Gating or triggering based on an MR signal, e.g. involving one or more navigator echoes for motion monitoring and correction · CPC title

• G01R33/4836 Primary

  using an RF pulse being spatially selective in more than one spatial dimension, e.g. a 2D pencil-beam excitation pulse · CPC title

• G01R33/546

  Interface between the MR system and the user, e.g. for controlling the operation of the MR system or for the design of pulse sequences · CPC title

• G01R33/4833

  using spatially selective excitation of the volume of interest, e.g. selecting non-orthogonal or inclined slices · CPC title

• G01R33/4838

  using spatially selective suppression or saturation of MR signals · CPC title