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      The Impact of Flip Angle and TR on the Enhancement Ratio of Dynamic Gadobutrol-enhanced MR Imaging: In Vivo VX2 Tumor Model and Computer Simulation.

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          Abstract

          Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is widely used to diagnose cancer and monitor therapy. The maximum enhancement ratio (ERmax) obtained from the curve of signal intensity over time could be a biomarker to distinguish cancer from normal tissue or benign tumors. We evaluated the impact of flip angle (FA) and repetition time (TR) on the ERmax values of dynamic gadobutrol-enhanced MR imaging, obtaining T1-weighted (T1W) MR imaging of VX2 tumors using 2-dimensional fast spoiled gradient echo (2D FSPGR) with various FAs (30°, 60° and 90°) at 1.5 tesla before and after injection of 0.1 mmol/kg gadobutrol. In vivo study indicated significant differences between ERmax values and area under the ER-time curve (AUC100) of VX2 tumors and muscle tissue, with the highest ERmax and AUC100 at FA 90°. Computer simulation also demonstrated the ER as a strictly increasing monotonic function in the closed interval [0°, 90°] for a given TR when using T1W FSPGR, and the highest ER value always occurred at FA 90°. The FA for the highest ER differed from that for the highest signal-to-noise or contrast-to-noise ratio. For long TR, the ER value increases gradually. However, for short TR, the ER value increases rapidly and plateaus so that the ER value changes little beyond a certain FA value. Therefore, we suggest use of a higher FA, near 90°, to obtain a higher ERmax for long TR in 2D SPGR or FSPGR and a smaller FA, much less than 90°, to reach an appropriate ERmax for short TR in 3D SPGR or FSPGR. This information could be helpful in setting the optimal parameters for DCE-MRI.

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          Author and article information

          Journal
          Magn Reson Med Sci
          Magnetic resonance in medical sciences : MRMS : an official journal of Japan Society of Magnetic Resonance in Medicine
          Japanese Society for Magnetic Resonance in Medicine
          1880-2206
          1347-3182
          2015
          : 14
          : 3
          Affiliations
          [1 ] Department of Biomedical Engineering, I-SHOU University.
          Article
          10.2463/mrms.2014-0048
          25833269
          10114001-305c-45d1-b6cb-ee1181c4f7b7
          History

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