MAGNETIC RESONANCE IMAGING APPARATUS AND MAGNETIC RESONANCE IMAGING METHOD

• US 20110109312A1
• Filed: 11/03/2010
• Published: 05/12/2011
• Est. Priority Date: 11/12/2009
• Status: Active Grant

• Current Assignee: Toshiba Medical Systems Corporation (Canon Inc.)
• Original Assignee: Toshiba Medical Systems Corporation (Canon Inc.), Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: YAMANAKA, Masaaki
• Granted Patent: US 9,013,183 B2
• Time in Patent Office: Days
• US Class Current: 324/309
• CPC Class Codes: G01R 33/288 Provisions within MR facilities for enhancing safety during MR, e.g. reduction of the specific absorption rate [SAR], detection of ferromagnetic objects in the scanner room
• CPC Class Codes: G01R 33/34046 Volume type coils, e.g. bird-cage coils; Quadrature bird-cage coils; Circularly polarised coils
• CPC Class Codes: G01R 33/56375 Intentional motion of the sample during MR, e.g. moving table imaging

Abstract

According to one embodiment, an MRI apparatus includes an image generating unit and an SAR calculating unit. The image generating unit receives a magnetic resonance signal generated as a result of transmission of an RF pulse from an object, and generates image data of the object based on the magnetic resonance signal. The SAR calculating unit performs a correction operation on an energy control value of the RF pulse according to an imaging condition, and calculates an SAR value based on an energy value subjected to the correction operation.

Claims

1. A magnetic resonance imaging apparatus, comprising:

an image generating unit that receives, from an object, a magnetic resonance signal generated as a result of transmission of an RF pulse and generates image data of the object based on the magnetic resonance signal; and

an SAR calculating unit that performs a correction operation on an energy control value of the RF pulse according to an imaging condition and calculates an SAR value based on an energy value subjected to the correction operation.

2. The magnetic resonance imaging apparatus according to claim 1,

wherein the SAR calculating unit is configured to perform a different correction operation depending on an imaging region of the object.

3. The magnetic resonance imaging apparatus according to claim 1,

wherein the SAR calculating unit is configured to perform the correction operation at predetermined time intervals and to store, as intermediate data, an energy value subjected to the correction operation obtained during a predetermined period just before a current reference time.

4. The magnetic resonance imaging apparatus according to claim 3, further comprising:

an imaging condition correcting unit that obtains the intermediate data from the SAR calculating unit, estimates an SAR value for a next scan based on the intermediate data and an imaging condition for the next scan, and determines “

the imaging condition for the next scan which gives an SAR value not exceeding an upper limit”

in a case of the estimated SAR value larger than the upper limit.

5. The magnetic resonance imaging apparatus according to claim 3, further comprising:

an imaging condition correcting unit that obtains the intermediate data from the SAR calculating unit, estimates an SAR value for a next scan based on the intermediate data and an imaging condition for the next scan, and, when the estimated SAR value is lower than an upper limit and has a margin equal to or greater than a predetermined value, with respect to the upper limit, determines the imaging condition for the next scan in such a manner that the estimated SAR value approaches the upper limit.

6. The magnetic resonance imaging apparatus according to claim 1,

wherein the correction operation is performed on the energy control value of the RF pulse so as to reduce an energy attenuation of the RF pulse along a path from a source of the RF pulse to an RF coil that transmits the RF pulse to the object.

7. The magnetic resonance imaging apparatus according to claim 6,

wherein the SAR calculating unit is configured to perform a different correction operation depending on an imaging region of the object.

8. The magnetic resonance imaging apparatus according to claim 6,

wherein the SAR calculating unit is configured to perform the correction operation at predetermined time intervals and to store, as intermediate data, an energy value subjected to the correction operation obtained during a predetermined period just before a current reference time.

9. The magnetic resonance imaging apparatus according to claim 1,

wherein the correction operation is performed on the energy control value of the RF pulse so as to reduce an energy consumption of the RF pulse in an RF coil that transmits the RF pulse to the object.

10. The magnetic resonance imaging apparatus according to claim 9,

wherein the SAR calculating unit is configured to perform a different correction operation depending on an imaging region of the object.

11. The magnetic resonance imaging apparatus according to claim 9,

wherein the SAR calculating unit is configured to perform the correction operation at predetermined time intervals and to store, as intermediate data, an energy value subjected to the correction operation obtained during a predetermined period just before a current reference time.

12. The magnetic resonance imaging apparatus according to claim 1, further comprising:

an RF coil that transmits the RF pulse to the object on a bed,

wherein the SAR calculating unit is configured to obtain position information on the bed and to perform the correction operation on the energy control value of the RF pulse so as to reduce an energy attenuation depending on a position of the bed.

13. The magnetic resonance imaging apparatus according to claim 12,

wherein the SAR calculating unit is configured to perform a different correction operation depending on an imaging region of the object.

14. The magnetic resonance imaging apparatus according to claim 12,

wherein the SAR calculating unit is configured to perform the correction operation at predetermined time intervals and to store, as intermediate data, an energy value subjected to the correction operation obtained in a predetermined period preceding a current reference time.

15. A magnetic resonance imaging method comprising the steps of:

receiving a magnetic resonance signal generated as a result of transmission of an RF pulse from an object;

generating image data of the object based on the magnetic resonance signal;

performing a correction operation on an energy control value of the RF pulse according to an imaging condition; and

calculating an SAR value based on an energy value subjected to the correction operation.