THE DIMINISHING VARIANCE ALGORITHM FOR REAL-TIME REDUCTION OF MOTION ARTIFACTS IN MRI

A technique has been developed whereby motion can be detected in real time during the acquisition of data, This enables the implementation o f several algorithms to reduce or eliminate motion effects from an ima ge as it is being acquired. One such algorithm previously described is the acceptance/rejection method, This paper deals with another real-t ime algorithm called the diminishing variance algorithm (DVA), With th is method, a complete set of preliminary data is acquired along with i nformation about the relative motion position of each frame of data, A fter all the preliminary data are acquired, the position information i s used to determine which data frames are most corrupted by motion, Fr ames of data are then reacquired, starting with the most corrupted one , The position information is continually updated in an iterative proc ess; therefore, each subsequent reacquisition is always done on the wo rst frame of data. The algorithm has been implemented on several diffe rent types of sequences, Preliminary in vivo studies indicate that mot ion artifacts are dramatically reduced.