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PURPOSE
To quantify Gd-DTPA concentration from signal intensity (SI) by mathematical interpretation of Volume Interpolated Body Examination (VIBE) sequence.
METHOD AND MATERIALS
50 tubes were filled with continuous concentrations of Gd-DTPA in saline (range0-6mM, increasing step 0.12mM). The T1 values of all the saline were measured through T1 maps, which were got using SE T1WI sequences with multiple TR (800/531ms) and the same TE (7.8ms). The relaxation rate (R1) is equal to 1/T1. The SIs of the 50 tubes were measured respectively, using VIBE sequence (1.5T Siemens, AVANTO, lesser soft coil, 3.5 sec.) with 60mm slab (12 interpolated 5mm slices) and different flip angles (FA) (10°, 15°, 25°, 45°, 90°) . The relation between R1 and Gd-DTPA concentration can be obtained from a linear regression. The relation between the SIs on the VIBE and R1 was fitted by a third-order polynomial function. Gd-DTPA concentration and SI could be related to R1 indirectly, from which SI-Time curves were converted to concentration-time curves. To optimize the dynamic range (R1; range associated with a monotonic increase of signal intensity) and the sensitivity (slope of the relationship between image signal intensity and R1) of the VIBE, the use of different FAs was tested. The effect of different interpolated slices was determined by comparing R1-SI curves of different slices.
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