Partial Flip Angle

INCORRECT. The T2* time is not changed by RF pulses or magnetic field gradients.

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INCORRECT. Smaller flip angles can be quicker to apply, but this does not significantly affect the repetition time (TR) of the pulse sequence. How does the flip angle affect the TR?

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Partial flip angle. The rotation of net magnetisation into the xy-plane need not be 90°. Less time is required for the recovery of Mz.

CORRECT. We can reduce the amount of time it takes to get an image in a large number of ways in MRI. However, the most simple is to reduce the amount of magnetisation which we rotate into the xy-plane.

Partial rotation of the net magnetisation vector produces a smaller signal; less magnetisation is precessing in the xy plane to start with. But there is usually enough for a good signal measurement. Since M_z has a headstart on it's way back to thermal equilibrium (M₀), we don't need to wait for as long before we can rotate the net magnetisation again and make another signal measurement (with a different phase encoding, of course).

Partial rotation of the net magnetisation is described by a lower angle of rotation (e.g. a 15° RF pulse).