Water excitation as an alternative to fat saturation in MR imaging: preliminary results in musculoskeletal imaging.
OBJECTIVE
To compare fat suppression methods by using spectrally selective fat saturation and section-selective water excitation in standard magnetic resonance (MR) imaging sequences used in day-to-day musculoskeletal practice.


METHODS
Eighty-three patients underwent MR examination with a 1.5-T system. The two methods were compared by using three common sequences: T1-weighted spin-echo (SE) imaging performed after contrast material injection (n = 24), intermediate-weighted fast SE (n = 36) imaging, and T2-weighted fast SE (n = 36) imaging. Acquisition times of the sequences and signal-to-noise and contrast-to-noise ratios of bone, muscle, fat, and water for the two methods were compared quantitatively. Images were then qualitatively reviewed by two radiologists who were blinded to the type of fat suppression used. Image quality was scored according to four criteria (homogeneity of fat suppression, susceptibility and foldover artifacts, conspicuousness of lesion, and overall image quality) by using a five-point scale (0, bad; 1, poor; 2, fair; 3, good; and 4, excellent). A paired Student t test was used to compare the quantitative data, and a nonparametric paired-data Wilcoxon signed rank test was used for qualitative analysis.


RESULTS
Water excitation allowed a substantial decrease in acquisition time (by up to 50%) for T1-weighted sequences. Quantitative measurements revealed a greater signal-to-noise ratio (P <.01) with water excitation for all three sequences, whereas the contrast-to-noise ratio was greater with water excitation only in intermediate-weighted sequences (P <.01). Qualitatively, water excitation proved statistically better than or equal to fat saturation for all criteria in all imaging sequences (P <.05). Mean scores of overall image quality ranged between 2.5 and 3.0 for fat saturation and 3.4 and 3.7 for water excitation, respectively (P <.05).


CONCLUSIONS
Section-selective water excitation is faster than conventional fat saturation and produces images of better quality.
Department of Radiology A, Hôpital Pellegrin, Centre Hospitalier Universitaire de Bordeaux, Place Amélie Raba-Léon, Cedex 33076 Bordeaux Cedex, France. olivier.hauger@chu-bordeaux.fr
Olivier
O
Hauger
Eric
E
Dumont
Jean-François
JF
Chateil
Maryse
M
Moinard
François
F
Diard
D000293:Adolescent; D000328:Adult; D000368:Aged; D003287:Contrast Media; D005223:Fats; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009140:Musculoskeletal Diseases / Q000175:diagnosis; D009141:Musculoskeletal System / Q000033:anatomy & histology*; D014867:Water
D003287:Contrast Media; D005223:Fats; D014867:Water