Magnetic resonance imaging apparatus and control method thereof
Appropriate processing is executed in a method for excluding body motion data and image reconstruction according to a type and a characteristic of a body motion, so as to reduce an influence of the body motion, and prevent deterioration of image quality caused by exclusion of data generated during the body motion. An MRI apparatus includes a processing determination unit that collects k-space data and acquires body motion information from a sensor capable of detecting not only a respiratory motion but also general body motions, analyzes the body motion information obtained by the sensor, and branches and executes processing for subsequent data collection and image reconstruction according to the analysis result. The MRI apparatus determines, based on a temporal characteristic such as a duration and a frequency, and a spatial characteristic of the body motion, particularly a generation pattern in a k-space, body motion data to be excluded, and executes image reconstruction suitable for k-space data after exclusion of the body motion data.
1. A magnetic resonance imaging apparatus, comprising:
a measurement unit configured to measure a nuclear magnetic resonance signal of a subject;
a calculation unit configured to generate an image by using the nuclear magnetic resonance signal measured by the measurement unit;
a control unit configured to control operations of the measurement unit and the calculation unit;
a body motion analysis unit configured to analyze, based on a body motion detection result received from a sensing unit disposed to be physically separated from the subject, and configured to detect a body motion of the subject, a spatial characteristic and a temporal characteristic of the body motion; and
a processing determination unit configured to determine, by using body motion information obtained by the body motion analysis unit, a change in processing of at least one of the measurement unit or the calculation unit, the control unit controlling the processing of the measurement unit and the calculation unit according to the determination result of the processing determination unit, wherein
the processing determination unit is further configured to determine, by using the body motion information, at least one of a body motion correction or remeasurement to be carried out, and to acquire the body motion information from the body motion analysis unit during a pre-scan performed by the measurement unit, and control, based on the body motion information acquired in the pre-scan, an image pulse-sequence used in a main scan executed following the pre-scan.
2. A control method of a magnetic resonance imaging apparatus including a measurement unit configured to measure a nuclear magnetic resonance signal of a subject, and a calculation unit configured to execute a calculation by using the nuclear magnetic resonance signal, the control method comprising:
an analysis step of analyzing, based on a body motion detection result received from a sensing unit disposed to be physically separated from the subject being imaged by the magnetic resonance imaging apparatus and detecting a body motion of the subject, a spatial characteristic and a temporal characteristic of the body motion;
a processing determination step of determining, by using body motion information obtained when analyzing in the analysis step, a change in processing of at least one of the measurement unit or the calculation unit;
a step of controlling the processing of the measurement unit and the calculation unit according to the determination result obtained in the processing determination step;
a step of determining, by using the body motion information, which of a body motion correction and remeasurement should be carried out; and
a step of acquiring the body motion information during a pre-scan performed by the measurement unit, and controlling, based on the body motion information acquired in the pre-scan, an image pulse-sequence used in a main scan executed following the pre-scan.
3. The magnetic resonance imaging apparatus according to claim 1 , wherein the body motion analysis unit is further configured to output the spatial characteristic and the temporal characteristic of the body motion as the body motion information, using a body motion analysis algorithm of a computer vision.
4. The magnetic resonance imaging apparatus according to claim 1 , wherein the processing determination unit is further configured to determine, by using the body motion information, whether the body motion correction is necessary, and when determining that the body motion correction is necessary, the processing determination unit determines whether to execute body motion correction processing of the calculation unit in an image space or in a measurement space.
5. The magnetic resonance imaging apparatus according to claim 1 , wherein the processing determination unit is further configured to specify, based on the body motion information, a nuclear magnetic resonance signal to be excluded from the nuclear magnetic resonance signal used by the calculation unit for image generation.
6. The magnetic resonance imaging apparatus according to claim 1 , wherein the processing determination unit is further configured to, when a frequency of the body motion is high in the body motion information acquired during the pre-scan, change a measurement method for the main scan to a non-Cartesian measurement.
7. The magnetic resonance imaging apparatus according to claim 1 , wherein
the body motion analysis unit is further configured to analyze a type, a motion time, and a motion vector, each of the body motion, and
the magnetic resonance imaging apparatus further comprises a body motion specifying unit configured to determine, based on the analysis result of the body motion analysis unit, data to be excluded from k-space data for image reconstruction.
8. The magnetic resonance imaging apparatus according to claim 5 , wherein the processing determination unit is further configured to determine whether a reduction factor when the nuclear magnetic resonance signal to be excluded is excluded is a value at which image reconstruction by the calculation unit is possible, and specify the nuclear magnetic resonance signal to be excluded.
9. The magnetic resonance imaging apparatus according to claim 5 , wherein
the measurement unit is further configured to measure the nuclear magnetic resonance signal at a predetermined acceleration rate,
the calculation unit is further configured to execute image reconstruction by using an under-sampled nuclear magnetic resonance signal, and
the processing determination unit is further configured to determine whether a total reduction factor of a reduction factor when the nuclear magnetic resonance signal to be excluded is excluded and a reduction factor determined by the predetermined acceleration rate is a value at which the image reconstruction by the calculation unit is possible, and specify the nuclear magnetic resonance signal to be excluded.
10. The magnetic resonance imaging apparatus according to claim 5 , wherein the processing determination unit is further configured to differentiate, depending on a domain of a measurement space, a rule for excluding the nuclear magnetic resonance signal.
11. The magnetic resonance imaging apparatus according to claim 5 , wherein the processing determination unit is further configured to determine whether the nuclear magnetic resonance signal to be excluded is low-frequency data or high-frequency data in a measurement space, and determine necessity of remeasurement based on the determination result.
12. The magnetic resonance imaging apparatus according to claim 9 , wherein the calculation unit is further configured to execute the image reconstruction with a total reduction factor of a reduction factor after the nuclear magnetic resonance signal to be excluded is excluded and the reduction factor determined by the predetermined acceleration rate.
13. The magnetic resonance imaging apparatus according to claim 9 , wherein the calculation unit is further configured to independently execute the image reconstruction with the reduction factor determined by the predetermined acceleration rate and the image reconstruction with a reduction factor after the nuclear magnetic resonance signal to be excluded is excluded.
14. The magnetic resonance imaging apparatus according to claim 7 , wherein the processing determination unit is further configured to perform a control of transmitting, based on the analysis result of the body motion analysis unit and based on the data to be excluded from the k-space data, to the measurement unit an instruction to change a measurement control procedure and to the calculation unit a selection of a reconstruction method to correct for the body motion.