Magnetic resonance imaging apparatus and a method for determining trigger timing of ce-mra scan

Abstract

The present invention discloses an apparatus and a method for determining a trigger timing of a CE-MRA scan. The apparatus comprises: a blood flow velocity acquisition unit configured to acquire a blood flow velocity of a target vessel; and a trigger timing determination unit configured to determine the trigger timing for performing the CE-MAR scan on a CE-MRA scan region according to the blood flow velocity and a predetermined image acquisition condition during a monitoring scan. The apparatus and method take the blood flow velocity into consideration, and can determine the trigger timing of the CE-MRA scan automatically and accurately.

1 . A magnetic resonance imaging apparatus for determining a trigger timing of a Contrast Enhanced Magnetic Resonance Angiography (CE-MRA) scan, comprising:
 a blood flow velocity acquisition unit configured to acquire a blood flow velocity of a target vessel; and   a trigger timing determination unit configured to determine the trigger timing for performing the CE-MAR scan on a CE-MRA scan region according to the blood flow velocity and a predetermined image acquisition condition during a monitoring scan.   
     
     
         2 . The apparatus according to  claim 1 , wherein the blood flow velocity acquisition unit is further configured to receive the blood flow velocity of the target vessel from outside. 
     
     
         3 . The apparatus according to  claim 1 , wherein the blood flow velocity acquisition unit comprises:
 an image acquisition unit configured to acquire a plurality of time-phase images obtained by the monitoring scan on a monitor region; and   a blood flow velocity detection unit configured to detect the blood flow velocity of the target vessel using the plurality of time-phase images.   
     
     
         4 . The apparatus according to  claim 1 , wherein the image acquisition condition includes the type of a sequence for the CE-MRA scan, and the trigger timing determination unit comprises:
 a scan lead time determination unit configured to determine a sequence switching time according to the type of the sequence for the CE-MRA scan as a scan lead time, wherein the sequence switching time is a time needed for switching from the monitoring scan to the CE-MRA scan of the type of the sequence; and   a trigger timing determination subunit configured to determine the trigger timing according to the blood flow velocity and the scan lead time.   
     
     
         5 . The apparatus according to  claim 4 , wherein the trigger timing determination subunit comprises:
 a trigger position determination unit configured to calculate a scan lead distance according to the blood flow velocity and the scan lead time, and determine a trigger position according to the scan lead distance and the CE-MRA scan region; and   a trigger position monitor configured to determine triggering the CE-MRA scan when it is detected through the monitoring scan that a contrast agent in the target vessel arrives at the trigger position.   
     
     
         6 . The apparatus according to  claim 5 , further comprising:
 a monitor region adjustment unit configured to expand a monitor region for the monitoring scan automatically when the trigger position is outside the monitor region, such that the trigger position is in the expanded monitor region.   
     
     
         7 . The apparatus according to  claim 4 , wherein the trigger timing determination subunit comprises:
 a trigger position determination unit configured to calculate a scan lead distance according to the blood flow velocity and the scan lead time, and determine a trigger position according to the scan lead distance and the CE-MRA scan region;   
       a residual trigger time calculator configured to calculate, according to the blood flow velocity, a time needed for a contrast agent in the target vessel to flow to the trigger position from a current position of the contrast agent in the target vessel detected through the monitoring scan, as a residual trigger time; 
       a modular operation unit configured to perform a modular calculation on the residual trigger time with an inter-frame time interval of the monitoring scan as a modulus, activate a residual trigger time monitor when a remainder resulting from the modular calculation is not zero, and activate a trigger position monitor when the remainder resulting from the modular calculation is zero;
 the residual trigger time monitor configured to start countdown when the same number of frames as a quotient resulting from the modular operation have been scanned through the monitoring scan, and determine triggering the CE-MRA scan when it is determined through the countdown that a time equal to the remainder resulting from the modular operation has elapsed; and 
 the trigger position monitor configured to determine triggering the CE-MRA scan when it is detected through the monitoring scan that the contrast agent in the target vessel arrives at the trigger position. 
 
     
     
         8 . The apparatus according to  claim 3 , wherein the blood flow velocity detection unit comprises:
 a vessel detection unit configured to detect the target vessel in the plurality of time-phase images; and   a blood flow velocity calculator configured to calculate the blood flow velocity of the target vessel according to a difference of the lengths of the target vessel in any two of the plurality of time-phase images and a time period between the two images.   
     
     
         9 . The apparatus according to  claim 8 , wherein the blood flow velocity detection unit is further configured to, in the case that a plurality of target vessels are detected by the vessel detection unit, determine the trigger timing using the smallest one of the blood flow velocities of the plurality of target vessels calculated by the blood flow velocity calculator, as the blood flow velocity for determining the trigger timing. 
     
     
         10 . The apparatus according to  claim 1 , further comprising:
 a monitor region determination unit configured to determine, before the monitoring scan is started, a monitor region for the monitoring scan according to a predetermined blood flow velocity of the target vessel, the predetermined image acquisition condition and the CE-MRA scan region.   
     
     
         11 . The apparatus according to  claim 1 , wherein the trigger timing determination unit is further configured to trigger the CE-MRA scan automatically after the trigger timing is determined. 
     
     
         12 . The apparatus according to  claim 7 , wherein in the case that the residual trigger time is shorter than the inter-frame time interval, it is determined to trigger the CE-MRA scan when the residual trigger time elapses, and the residual trigger time is calculated and corrected frame by frame. 
     
     
         13 . A method for determining a trigger timing of a Contrast Enhanced Magnetic Resonance Angiography (CE-MRA) scan, comprising:
 acquiring a blood flow velocity of a target vessel; and   determining the trigger timing for performing the CE-MAR scan on a CE-MRA scan region according to the blood flow velocity and a predetermined image acquisition condition during a monitoring scan.