Optimized clinical T2 relaxometry with a standard CPMG sequence.
OBJECTIVE
To optimize the accuracy and precision of T2 measurements using the standard Carr-Purcell-Meiboom-Gill (CPMG) sequence. T2 values obtained with this technique are normally sensitive to imperfect refocusing due to the formation of unwanted stimulated echoes.


METHODS
Modifications are made to the refocusing slice selection width and the interleaving scheme. A widened refocusing slice improves the uniformity of the refocusing flip angle across the slice. A slow spin echo acquisition provided "gold standard" T2 values. Repeated T2 measurements in phantom and human studies are used to compare the accuracy and precision of the optimized and non-optimized CPMG implementations.


RESULTS
The required slice thickness ratio between refocusing and excitation slice widths is found to be 3:1 for typical optimized radiofrequency pulses. T2 values obtained using this optimized implementation more closely correspond to "gold standard" values. Repeated T2 measurements indicate significantly improved correspondence between data and model. A reduction in the fitting error of approximately 70% is demonstrated for phantoms.


CONCLUSIONS
We demonstrate that a relatively simple change to the CPMG relaxometry sequence parameters from the default setup yields significant improvements in the accuracy and precision of T2 measurements.
Pell
Gaby S
GS
Brain Research Institute, Austin Health, Heidelberg West, VIC, Australia.
Briellmann
Regula S
RS
Waites
Anthony B
AB
Abbott
David F
DF
Lewis
David P
DP
Jackson
Graeme D
GD
D000328:Adult; D016477:Artifacts; D004578:Electron Spin Resonance Spectroscopy; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D012986:Software Validation