Simultaneous multislice perfusion imaging in mri

Abstract

An MRI system and method for dynamic susceptibility contrast (DSC) imaging use multiplexed echo planar imaging (M-EPI) to essentially simultaneously acquire MR signals for perfusion parameter images of multiple slices. This essentially simultaneous acquisition of MR signals for multiple slices can be repeated in rapid succession without deteriorating T2* contrast, which makes it practical to image multiple perfusion phases and brings about other significant benefits.

1 - 12 . (canceled) 
     
     
         13 . A magnetic resonance (MR) method of dynamic susceptibility contrast (DSC) perfusion imaging using multiplexed echo planar imaging (M-EPI) to simultaneously image a set of multiple slices and rapidly repeat the imaging of the set of slices in timed relationship to an introduction of contrast agent, comprising:
 (a) positioning a patient in a magnetic resonance imaging (MRI) scanner;   (b) introducing an MRI contrast agent into the patient's vascular system;   (c) applying a radiofrequency (RF) excitation pulse multiplexed in time or frequency to the patient in a selected time relationship to the introduction of the contrast agent;   (d) essentially simultaneously acquiring MR signals for multiple slices of the patient generated in response to the RF excitation pulse, using EPI signal acquisition;   (e) repeating steps (c) and (d) at least once, each repetition being in a selected time relationship to the introduction of the contrast agent, using shorter time intervals TR between repetitions or essentially simultaneous acquisition of MR signals for more slices in a repetition, or both, compared with conventional EPI imaging; and   (f) computer-processing the MR signals to derive images of perfusion parameters for patent's anatomy related to at least some of said slices.   
     
     
         14 . The method of  claim 13  in which step (e) comprises repeating steps (c) and (d) at least 10 times. 
     
     
         15 . The method of  claim 13  in which step (e) comprises repeating steps (c) and (d) at least 50 times. 
     
     
         16 . The method of  claim 13  in which said TR is ≦2000 msec. 
     
     
         17 . The method of  claim 13  in which step (d) comprises acquiring the MR signals for all of the multiple slices in a read period TE≦100 msec. 
     
     
         18 . The method of  claim 13  in which step (f) comprises relating the MR signals S(0) acquired in response to one of the RF excitation signals to respective MR signals S acquired in response to other RF excitation pulses to derive perfusion images or metrics related to changes in T2* relaxation time using a formula
   − In ( S/S 0)/ TE  
 
 
       where TE is related to a time period for essentially simultaneously acquiring the MR signals for the multiple slices generated in response to a multiband RF excitation pulse. 
     
     
         19 . The method of  claim 13  in which at least one of the multiple slices for which MR signals are acquired essentially simultaneously is at a location in the patient's body related to an arterial input and at least one other slice is at a location for which perfusion metrics related to flow from the input. 
     
     
         20 . The method of  claim 13  in which step (d) is repeated multiple times in respective time intervals related to perfusion before, during and after the contrast agent is introduced. 
     
     
         21 . The method of  claim 13  in which the RF excitation pulse is a multiband pulse multiplexed in frequency. 
     
     
         22 . The method of  claim 13  in which the FR excitation pulse is multiplexed in time and comprises a sequence of pulses closely spaced in time. 
     
     
         23 . The method of  claim 13  in which the step of introducing a contrast agent into the patient's vascular system comprises introducing a lower dose than in conventional dynamic susceptibility contrast (DSC) MRI perfusion imaging. 
     
     
         24 . A system
 an MRI data acquisition unit configured for imaging a patient;   a contrast agent injection system configured to introduce an MRI contrast agent into the vascular system of a patient being imaged with said MRI data acquisition unit;   a computer coupled with the MRI data acquisition unit and configured to cause the unit to apply a radiofrequency (RF) excitation pulse multiplexed in time or frequency to the patient in a selected time relationship to the introduction of the contrast agent;   said computer being further configured to cause the data acquisition unit to essentially simultaneously acquire MR signals for multiple slices of the patient generated in response to the RF excitation pulse, using EPI signal acquisition, and to repeat the application of the RF pulse and the acquisition of MR signals plural times, each repetition being in a selected time relationship to the introduction of the contrast agent, using shorter time intervals TR between repetitions or essentially simultaneous acquisition of MR signals for more slices in a repetition, or both, compared with conventional EPI imaging; and   said computer being further configured to process the MR signals to derive images of perfusion parameters for patents anatomy related to at least some of said slices.