Local flip angle correction for improved volume T1-quantification in three-dimensional dGEMRIC using the Look-Locker technique.
OBJECTIVE
To present an evaluation method for three-dimensional Look-Locker (3D-LL) based T1 quantification, calculating correct T1 values independent of local flip angle (FA) variations. The method was evaluated both in phantoms and in vivo in a delayed Gadolinium Enhanced MRI of Cartilage (dGEMRIC) study with 33 subjects.


METHODS
T1 was measured with 3D-LL, using both local FA correction and a precalculated FA slice profile, and compared with standard constant FA correction, for all slices in phantoms and in both femur condyles in vivo. T1 measured using two-dimensional Inversion Recovery (2D-IR) was used as gold standard.


RESULTS
Due to the FA being slice dependent, the standard constant FA correction results in erroneous T1 (systematic error = 109.1 ms in vivo), especially in the outer slices. With local FA correction, the calculated T1 is excellent for all slices in phantoms (<5% deviation from 2D-IR). In vivo the performance is lower (systematic error = -57.5 ms), probably due to imperfect inversion. With precalculated FA correction the performance is very good also in vivo (systematic error = 13.3 ms).


CONCLUSIONS
With the precalculated FA correction method, the 3D-LL sequence is robust enough for in vivo dGEMRIC, even outside the centermost slices.
Siversson
Carl
C
Department of Radiation Physics, Lund University, Malmö, Sweden. carl.siversson@med.lu.se
Tiderius
Carl-Johan
CJ
Dahlberg
Leif
L
Svensson
Jonas
J
D000070598:Anterior Cruciate Ligament Injuries; D002358:Cartilage, Articular / Q000293:injuries*; D003287:Contrast Media; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007718:Knee Injuries / Q000175:diagnosis*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging
D003287:Contrast Media; D019786:Gadolinium DTPA