Diffusion weighted imaging (DWI) and diffusion tensor imaging (DTI) are established techniques of magnetic
resonance widely used for the characterization of the cerebral tissue. Despite the successful application in the brain,
diffusion-weighted single-shot echo-planar-imaging (EPI) of the spinal cord is hindered by the need for highly-resolved
spatial encoding in an area of strong magnetic field inhomogeneities, and the shortness of transverse relaxation time.
The major aim of this study was the optimization of a reliable single-shot EPI sequence for DTI of the spinal cord at
1.5T.
Ten healthy volunteers participated in the study (mean age=28.4±3.1). A single-shot EPI sequence with double spinecho
diffusion preparation and nominal in-plane resolution of 0.9x0.9mm2 was optimized with regard to cerebrospinal
fluid artifacts, and contrast-to-noise ratio between gray matter (GM) and white matter (WM). The effective sequence
resolution was evaluated on a phantom.
A cardiac-pulse gated sequence with optimal matrix size (read x phase=64x32) and b-value (700s/mm2) allowed for the
acquisition of highly-resolved images of the spinal cord (effective in-plane resolution=1.1mm). Preliminary results on
two healthy volunteers showed that the butterfly-shaped GM is clearly recognizable in the reconstructed fractional
anisotropy (FA) maps. Measured WM FA values were 0.698±0.076 and 0.756±0.046. No significant differences were
found in the mean diffusivity computed in the WM as compared to the GM areas.
Optimized spinal cord diffusion imaging provided promising preliminary results on healthy volunteers. The application
of the proposed protocol in the assessment of neurological disorders may allow for improved characterization of healthy
and impaired WM and GM.
Purpose: As the MR contrast-medium gadobutrol is completely eliminated via glomerular filtration, the glomerular filtration rate (GFR) can be quantified after bolus-injection of gadobutrol and complete mixing in the extracellular fluid volume (ECFV) by measuring the signal decrease within the liver parenchyma. Two different navigator-gated single-shot saturation-recovery sequences have been tested for suitability of GFR quantification: a TurboFLASH and a TrueFISP readout technique.
Materials and Methods: Ten healthy volunteers (mean age 26.1±3.6) were equally devided in two subgroups. After bolus-injection of 0.05 mmol/kg gadobutrol, coronal single-slice images of the liver were recorded every 4-5 seconds during free breathing using either the TurboFLASH or the TrueFISP technique. Time-intensity curves were determined from manually drawn regions-of-interest over the liver parenchyma. Both sequences were subsequently evaluated regarding signal to noise ratio (SNR) and the behaviour of signal intensity curves. The calculated GFR values were compared to an iopromide clearance gold standard.
Results: The TrueFISP sequence exhibited a 3.4-fold higher SNR as compared to the TurboFLASH sequence and markedly lower variability of the recorded time-intensity curves. The calculated mean GFR values were 107.0±16.1 ml/min/1.73m2 (iopromide: 92.1±14.5 ml/min/1.73m2) for the TrueFISP technique and 125.6±24.1 ml/min/1.73m2 (iopromide: 97.7±6.3 ml/min/1.73m2) for the TurboFLASH approach. The mean paired differences with TrueFISP was lower (15.0 ml/min/1.73m2) than in the TurboFLASH method (27.9 ml/min/1.73m2).
Conclusion: The global GFR can be quantified via measurement of gadobutrol clearance from the ECFV. A saturation-recovery TrueFISP sequence allows for more reliable GFR quantification as a saturation recovery TurboFLASH technique.
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