title: 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.
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.
authors.affiliation: Department of Biomedical Engineering, I-SHOU University.
authors.forename: Po-Chou
authors.initials: PC
authors.lastname: Chen
authors.forename: Ding-Jie
authors.initials: DJ
authors.lastname: Lin
authors.forename: Jo-Chi
authors.initials: JC
authors.lastname: Jao
authors.forename: Chia-Chi
authors.initials: CC
authors.lastname: Hsiao
authors.forename: Li-Min
authors.initials: LM
authors.lastname: Lin
authors.forename: Huay-Ben
authors.initials: HB
authors.lastname: Pan
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology*; D000818:Animals; D003198:Computer Simulation; D003287:Contrast Media; D004195:Disease Models, Animal; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009942:Organometallic Compounds; D019047:Phantoms, Imaging; D011817:Rabbits; D013848:Thigh / Q000473:pathology
chemical_list: D003287:Contrast Media; D009942:Organometallic Compounds; C090600:gadobutrol