Takako Aoki PhD, Presenter: Nothing to Disclose

Mamoru Niitsu MD, Abstract Co-Author: Nothing to Disclose

Kyosuke Kurita RT, Abstract Co-Author: Nothing to Disclose

Reiko Hashimoto RT, Abstract Co-Author: Nothing to Disclose

Shinichi Watanabe RT, Abstract Co-Author: Nothing to Disclose

Junji Tanaka MD, Abstract Co-Author: Nothing to Disclose

We have proposed an optimized protocol with 9 shots per slice and a B1 filter for improved detection of the GAG-CEST effect at 3T in human knee articular cartilage.

Glycosaminoglycan (GAG) concentration in articular cartilage is one of the crucial factors for early diagnosis of osteoarthritis. On a 3T scanner, the chemical shift between GAG and bound water is small, and the signal intensity of GAG is relatively low. Optimization of the scan protocol to maximize detection of chemical exchange saturation transfer (CEST) is essential in order to obtain clinically useful GAG-CEST scans of human knees. In our institute so far, scan parameters have been optimized using phantoms with GAG concentrations of 0.26-1.3w/v% in vitro, and we attempted further optimization for the clinical application of GAG-CEST MRI.

B1 heterogeneity distorted the Z-spectra such that the GAG peak migrated away from the value of 1 ppm suggested in the literature. On the other hand, by applying a B1 filter and 9 shots per slice, the GAG peak tended to be more robust and to fall at 1 ppm. To separate the small chemical shift of GAG in human knees on a 3T scanner, it is essential to maximize detection of the CEST effect.

The knees of 18 healthy volunteers (mean age 36.1 years) were scanned on a whole-body 3T MRI scanner using a 15-channel knee coil and a turbo-FLASH-based prototype CEST sequence. The effects of the following parameters were evaluated by calculating MTR asymmetry (MTRasym) from Z-spectra (plots of signal intensity at sequential saturation pulse frequencies): (1) For 2D scans, the number of shots per slice (4, 6 and 9 shots). (2) For both 2D and 3D scans, B1 filter on and off.  

Aoki, T, Niitsu, M, Kurita, K, Hashimoto, R, Watanabe, S, Tanaka, J, Improved Detection of the Glycosaminoglycan Chemical Exchange Saturation Transfer (GAG-CEST) Effect in Human Knee Cartilage at 3T .  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14012606.html