Magnetic resonance scanning and imaging method and magnetic resonance imaging system
Embodiments of the present application provide a magnetic resonance scanning and imaging method, and a magnetic resonance imaging system. The method includes: determining a pulse to be adjusted in a scan sequence, the pulse to be adjusted including a first radio-frequency pulse and a first gradient pulse applied along with the first radio-frequency pulse; determining an adjustment factor based on the first gradient pulse and a minimum repetition time related to a specific absorption rate of radio-frequency energy; adjusting the scan sequence based on the adjustment factor; and, using the adjusted scan sequence, performing a diagnostic scan on a site to be examined, to obtain a magnetic resonance image.
1 . A magnetic resonance scanning and imaging method, characterized in that the method comprises:
determining a pulse to be adjusted in a scan sequence, the pulse to be adjusted comprising a first radio-frequency pulse and a first gradient pulse applied along with the first radio-frequency pulse;
determining an adjustment factor based on the first gradient pulse and a minimum repetition time related to a specific absorption rate of radio-frequency energy;
adjusting the scan sequence based on the adjustment factor; and
using the adjusted scan sequence, performing a diagnostic scan on a site to be examined, to obtain a magnetic resonance image.
2 . The method according to claim 1 , characterized in that the first radio-frequency pulse comprises at least one among an excitation pulse and a refocusing pulse.
3 . The method according to claim 1 , characterized in that the scan sequence further comprises a second gradient pulse not applied along with the first radio-frequency pulse; and
determining the adjustment factor based on the first gradient pulse, the second gradient pulse, and the minimum repetition time related to the specific absorption rate of radio-frequency energy.
4 . The method according to claim 1 , characterized in that determining an adjustment factor based on the first gradient pulse and a minimum repetition time related to a specific absorption rate of radio-frequency energy comprises:
determining the adjustment factor based on the rise time of the first gradient pulse, the duration of maximum gradient strength of the first gradient pulse, and the minimum repetition time.
5 . The method according to claim 4 , characterized in that the product of the minimum repetition time and the adjustment factor is equal to the sum of a first time and a second time, the first time being equal to twice the product of the rise time and the adjustment factor, and the second time being equal to the ratio of the duration to the adjustment factor.
6 . The method according to claim 3 , characterized in that determining the adjustment factor based on the first gradient pulse, the second gradient pulse, and the minimum repetition time related to the specific absorption rate of radio-frequency energy comprises:
determining the adjustment factor based on the rise time of the first gradient pulse, the duration of maximum gradient strength of the first gradient pulse, the time difference between the end time of the second gradient pulse and the end time of the first gradient pulse, and the minimum repetition time.
7 . The method according to claim 6 , characterized in that the product of the minimum repetition time and the adjustment factor is equal to the sum of the time difference, a first time, and a second time, the first time is equal to twice the product of the rise time and the adjustment factor, and the second time is equal to the ratio of the duration to the adjustment factor.
8 . The method according to claim 1 , characterized in that the method further comprises:
replacing the value of the adjustment factor with the value of a preset factor when the adjustment factor is less than or equal to the preset factor.
9 . The method according to claim 1 , characterized in that adjusting the scan sequence based on the adjustment factor comprises:
multiplying separately the amplitude value of the first radio-frequency pulse in the scan sequence, the maximum gradient strength value of the first gradient pulse, and the rise time of the first gradient pulse by the adjustment factor; and
dividing the pulse width of the first radio-frequency pulse and the duration of maximum gradient strength of the first gradient pulse by the adjustment factor, to obtain an adjusted scan sequence.
10 . The method according to claim 1 , characterized in that the adjustment factor is greater than 0 and less than 1.
11 . A magnetic resonance imaging system, characterized in that the system comprises:
a scanning unit; and
a controller configured to execute the magnetic resonance scanning and imaging method according to claim 1 .