Multiecho multimoment refocussing of motion in magnetic resonance imaging: MEM-MO-RE.
Gradient moment nulling techniques for refocussing of spin dephasing resulting from movement during application of magnetic resonance imaging gradients have gained widespread application. These techniques offer advantages over conventional imaging gradients by reducing motion artifacts due to intraview motion, and by recovering signal lost from spin dephasing. This paper presents a simple technique for designing multiecho imaging gradient waveforms that refocus dephasing from the interaction of imaging gradients and multiple derivatives of position. Multiple moments will be compensated at each echo. The method described relies on the fact that the calculation of time moments for nulled moment gradient waveforms is independent of the time origin chosen. Therefore, waveforms used to generate the second echo image for multiple echo sequences with echo times given by TEn = TE1 + (n - 1) * (TE2 - TE1) may also be used for generation of the third and additional echo images. All echoes will refocus the same derivatives of position. Multiecho, multimoment refocussing (MEM-MO-RE) images through the liver in a patient with ampullary adenocarcinoma metastatic to the liver demonstrate the application of the method in clinical scanning.
Duerk
J L
JL
Department of Radiology, MetroHealth Medical Center, Cleveland, Ohio 44109.
Simonetti
O P
OP
Hurst
G C
GC
Motta
A O
AO
D000230:Adenocarcinoma / Q000175:diagnosis / Q000556:secondary; D000368:Aged; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008113:Liver Neoplasms / Q000175:diagnosis / Q000556:secondary; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008433:Mathematics; D008962:Models, Theoretical; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors