Ultrashort echo time magnetization transfer (UTE-MT) imaging and modeling: magic angle independent biomarkers of tissue properties

Ya-Jun Ma, Hongda Shao, Jiang Du, Eric Y. Chang
2016 NMR in Biomedicine  
Magnetic resonance (MR) imaging biomarkers such as T 2 , T 2 * and T 1rho have been widely used, but are confounded by the magic angle effect. The purpose of this study is to investigate the use of the two-dimensional ultrashort echo time magnetization transfer (UTE-MT) sequence for potential magic angle independent MR biomarkers. Magnetization transfer was investigated in cadaveric Achilles tendon samples using the UTE-MT sequence at five MT powers and five frequency offsets ranging from 2-50
more » ... Hz. The protocol was applied at 5 sample orientations ranging from 0-90° relative to the B 0 field. The results were analyzed with a two-pool quantitative MT model. Multiple TE data was also acquired and mono-exponential T 2 * was calculated for each orientation. Macromolecular proton fractions and exchange rates derived from UTE-MT modeling did not appreciably change between the various orientations whereas the T 2 * relaxation time demonstrated up to a 6-fold increase from 0° to 55°. The UTE-MT technique with two-pool modeling shows promise as a clinically compatible technique that is resistant to the magic angle effect. This method provides information on the macromolecular proton pool that cannot be directly obtained by other methods, including regular UTE techniques. Graphical abstract Graphes of T 2 * values derived by fitting multiple-TE data and macromolecular proton fractions (f), T 2 value of macromolecular proton (T 2m ) and exchange rate from macromolecular proton to water proton (RM 0w ) derived from two-pool MT modeling with five angle orientations between fiber direction F ⃗ and B ⃗ 0 . Fitting errors of these parameters were shown by error bars.
doi:10.1002/nbm.3609 pmid:27599046 pmcid:PMC5069073 fatcat:x3horvp2evaq5kqtnqnxsbphmy