Magnetic resonance imaging using preparation scan for optimizing pulse sequence

• US 6,781,375 B2
• Filed: 08/15/2002
• Issued: 08/24/2004
• Est. Priority Date: 08/31/2001
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Takai, Hiroshi, Miyazaki, Mitsue
• Primary Examiner(s): ARANA, LOUIS M
• Application Number:
  US10/218,904
• Publication Number:
  US 20030042905A1
• Time in Patent Office: 740 Days
• Field of Search: 324/314, 324/306, 324/307, 324/309, 324/300, 324/318, 324/322
• US Class Current: 324/314
• CPC Class Codes: G01R 33/543 Control of the operation of the MR system, e.g. setting of acquisition parameters prior to or during MR data acquisition, dynamic shimming, use of one or more scout images for scan plane prescription G01R33/546 takes precedence
• CPC Class Codes: G01R 33/546 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 Class Codes: G01R 33/5602 by filtering or weighting based on different relaxation times within the sample, e.g. T1 weighting using an inversion pulse
• CPC Class Codes: G01R 33/5613 Generating steady state signals, e.g. low flip angle sequences [FLASH]
• CPC Class Codes: G01R 33/563 of moving material, e.g. flow contrast angiography
• CPC Class Codes: G01R 33/5635 Angiography, e.g. contrast-enhanced angiography [CE-MRA] or time-of-flight angiography [TOF-MRA]
• CPC Class Codes: G01R 33/56509 due to motion, displacement or flow, e.g. gradient moment nulling G01R33/567 takes precedence
• CPC Class Codes: G01R 33/5673 Gating or triggering based on a physiological signal other than an MR signal, e.g. ECG gating or motion monitoring using optical systems for monitoring the motion of a fiducial marker
• CPC Class Codes: G01R 33/583 Calibration of signal excitation or detection systems, e.g. for optimal RF excitation power or frequency G01R33/246 takes precedence
• CPC Class Codes: G01R 33/586 for optimal flip angle of RF pulses

Abstract

To optimize in advance a desired image quality determining pulse sequence parameter incorporated in an imaging scan, a preparation scan is adopted. The preparation scan is performed with the amount of at least one desired image quality parameter changed for each of plural preparatory images, so that a plurality of preparatory images at the desired same region of the object are acquired. For example, one such image quality parameter is TI (inversion time). The acquired preparatory scan data are processed into a plurality of preparatory images for display. A desired preparatory image is then selected from the plural preparatory images displayed, and the amount of the desired parameter used for that selected preparatory image is then set for use in the pulse sequence for a complete diagnostic imaging scan. Hence the desired image quality determining parameter of the pulse sequence is caused to have an optimum value before an actual complete diagnostic imaging scan.

Claims

1. A magnetic resonance imaging system for performing an imaging scan based on a selected pulse sequence to obtain an MR image at a selected region of an object to be imaged, the system comprising:

a preparation scan performing unit configured to perform a preparation scan to acquire data for a plurality of preparatory images all at the same common location in the selected region of the object, the preparation scan being performed with the value of at least one desired image quality parameter of the pulse sequence being changed for acquisition of each of plural preparatory images;

a preparatory image producing unit configured to produce a corresponding plurality of preparatory images having differing image quality parameters from the data acquired by the performance of the preparation scan;

a displaying unit configured to display the plurality of preparatory images associated with respectively different image quality parameters;

a selection unit configured to allow a desired preparatory image to be selected from the plurality of preparatory images displayed by the displaying unit; and

a setting unit configured to set, into an imaging scan, the value of the image quality parameter associated with the selected preparatory image.

2. A magnetic resonance imaging system as in claim 1, wherein the preparation scan performing unit is configured to perform the preparatory scan with an image matrix smaller in size than that performed by the imaging scan.

3. A magnetic resonance imaging system as in claim 1, wherein the preparation scan is a two-dimensional scan and the imaging scan is a three-dimensional scan.

4. A magnetic resonance imaging system as in claim 1, wherein the preparation scan performing unit is configured to perform the preparation scan prior to the performance of the imaging scan.

5. A magnetic resonance imaging system as in claim 1, further comprising a breath-hold instructing unit configured to instruct the object to continue holding its breath during preparation scan and during the imaging scan.

6. A magnetic resonance imaging system as in claim 1, wherein the pulse sequence includes a train of pulses belonging to SSFP (Steady State Free Precession)-system pulse sequences.

7. A magnetic resonance imaging system as in claim 1, wherein the at least one desired image quality parameter of the pulse sequence includes at least one parameter selected from the group of image contrast parameters consisting of:

a strength of a pulse to suppress a flow void phenomenon of a fluid in the object;

an effective echo time TE_eff concerning behaviors of spins of the object;

a pulse to compensate spin movements due to flow of fluid in the object;

a TI (inversion time) of spins observed when an inversion pulse is applied to the object;

an ETS (echo train spacing) time given to echo signals acquired from the object;

a flip angle of a fat suppression pulse applied to suppress signals from being acquired from fat of the object;

a TI (inversion time) time observed when a fat suppression pulse is applied to the object;

a strength of an MT (magnetization transfer) to cause an MT effect resultant from behaviors of spins in the object;

an angle of a refocusing pulse to reduce an MT effect to be caused in the object;

a flip angle of an RF pulse incorporated in the pulse sequence;

a flip angle of a refocusing pulse incorporated in the pulse sequence; and

a TR (repetition time) of the pulse sequence.

8. A magnetic resonance imaging system for performing an imaging scan based on a selected pulse sequence in order to obtain an MR image at a selected region of an object to be imaged, the system comprising:

a preparation scan performing unit configured to perform a preparation scan to acquire data for a plurality of preparatory images all at a common slice located in the selected region of the object, the preparation scan being performed with a TI (inversion time) incorporated in the pulse sequence being changed for acquisition of each of plural preparatory images, the TI being observed when an inversion pulse is applied to the selected region of the object;

a preparatory image producing unit configured to produce a corresponding plurality of preparatory images from the data acquired by the performance of the preparation scan;

a displaying unit configured to display the plurality of preparatory images;

a selection unit configured to allow a desired preparatory image to be selected from the plurality of preparatory images displayed by the displaying unit; and

a setting unit configured to set, into an imaging scan, the TI period associated with the selected preparatory image.

9. A magnetic resonance imaging system for performing a three-dimensional imaging scan based on a selected pulse sequence in order to obtain an MR image at a selected region of an object to be imaged, the system comprising:

a preparation scan performing unit configured to perform a two-dimensional preparation scan to acquire data for a plurality of preparatory images at a common slice located in the selected region of the object, the preparation scan being performed with the value of at least one desired image contrast parameter of the pulse sequence being changed for acquisition of each of plural preparatory images;

a preparatory image producing unit configured to produce a corresponding plurality of preparatory images having different contrast parameters from the data acquired by the performance of the preparation scan; and

a setting unit configured to set the value of the at least one desired contrast parameter for the imaging scan on the basis of the plurality of preparatory images produced.

10. A method of optimizing at least one image quality parameter of an MR imaging scan pulse sequence, the imaging scan being performed to provide an MR image at a selected region of an object to be imaged, the method comprising:

performing a preparation scan to acquire data for a plurality of preparatory images at a common slice located in the selected region of the object, the preparation scan being performed with the value of at least one desired image quality parameter of the pulse sequence being changed for acquisition of each of plural preparatory images;

producing a corresponding plurality of preparatory images having differing image plurality parameters from the data acquired by the performance of the preparation scan;

displaying the plurality of preparatory images;

selecting a desired preparatory image from the plurality of preparatory images displayed; and

setting, into the imaging scan, the value of the at least one desired image quality parameter associated with the selected preparatory image.

11. A method of optimizing at least one image quality parameter of an MR imaging scan pulse sequence, the imaging scan being performed to provide an MR image at a selected region of an object to be imaged, the method comprising:

performing a two-dimensional preparation scan to acquire data for a plurality of preparatory images at a common slice located in the selected region of the object, the preparation scan being performed with the value of at least one desired image quality parameter of the pulse sequence being changed for acquisition of each of plural preparatory images;

producing a corresponding plurality of preparatory images having differing image quality parameters from the data acquired by the performance of the preparation scan; and

setting the value of the at least one desired image quality parameter of the imaging scan on the basis of the plurality of preparatory images produced.

12. A magnetic resonance imaging system for performing a three-dimensional imaging scan based on a selected pulse sequence to obtain an MR image at a selected region of an object, said object being placed in a magnetic static field, to which magnetic gradient fields are applied and from which an MRecho is detected, the system comprising:

a sequencer configured to operate in response to information about the pulse sequence so as to cause not only the magnetic gradient fields and the RF signal to be applied to the region of the object but also the echo to be received;

first means operated through the sequencer by a host computer and configured to perform a two-dimensional preparation scan to acquire data for a plurality of preparatory images at a common slice located in the selected region of the object, the preparation scan being performed with the value of at least one desired image contrast parameter of the pulse sequence being changed for acquisition of each of plural preparatory images and being performed with an image matrix smaller in size than that performed by the imaging scan;

a calculator configured to produce a corresponding plurality of preparatory images having differing image contrast parameters from the data acquired by the performance of the preparation scan;

a display unit configured to display the plurality of preparatory images;

an input device configured to allow a desired preparatory image to be selected from the plurality of preparatory images displayed by the display unit; and

second means operated by the host computer and configured to set, into an imaging scan, the value of the at least one desired image contrast parameter associated with the selected preparatory image.

13. A magnetic resonance imaging system as in claim 12, wherein the preparation scan performing unit is configured to perform the preparation scan prior to the performance of the imaging scan.

14. A magnetic resonance imaging system as in claim 13, further comprising a breath-hold instructing unit configured to instruct the object to continue holding its breath during the preparation scan and during the imaging scan.

15. A magnetic resonance imaging system as in claim 14, wherein the pulse sequence includes a train of pulses belonging to SSFP (Steady State Free Precession)-system pulse sequences.

16. A magnetic resonance imaging system as in claim 15, wherein the at least one desired image contrast parameter of the pulse sequence includes at least one parameter selected from a group of parameters consisting of:

a strength of a pulse to suppress a flow void phenomenon of a fluid in the object;

an effective echo time TE_eff concerning behaviors of spins of the object;

a pulse to compensate spin movements due to flow of fluid in the object;

a TI (inversion time) of spins observed when an inversion pulse is applied to the object;

an ETS (echo train spacing) time given to echo signals acquired from the object;

a flip angle of a fat suppression pulse applied to suppress signals from being acquired from fat of the object;

a TI (inversion time) observed when a fat suppression pulse is applied to the object;

a strength of an MT (magnetization transfer) to cause an MT effect resultant from behaviors of spins in the object;

an angle of a refocusing pulse to reduce an MT effect to be caused in the object;

a flip angle of an RE pulse incorporated in the pulse sequence;

a flip angle of a refocusing pulse incorporated in the pulse sequence; and

a TR (repetition time) of the pulse sequence.