Table 4 Influence of geometry parameters for CE-MRA acquisitions

Acquisition Matrix, N_R, in the readout direction (Base Resolution)

256 Minimum Increase to 512 preferred

To get best resolution in readout direction

512 matrix increases TE and therefore TR. (increases scan time)

Acquisition Matrix, N_P, in the phase encoding direction

Maximise

To get best resolution in phase encoding direction

Increases Scan time (directly proportional)

(depends on breath-hold period)

SNR decreases as square root of increase

No of slices, N_S

Maximise

Increases coverage of volume thickness

Scan time (increases proportionally)

(depends on breath-hold period, slice thickness and FOV_S

Increases SNR as square root

(fixed slice thickness)

Slice thickness, THK

Minimise for best resolution in the slice direction

Increases through-plane resolution

Decreases coverage

FOV_S = THKxN_S

Decreases SNR (directly proportional)

Field of View (FOV_R)

Optimise for desired in-plane coverage

Aim to get best in-plane resolution without getting too much foldover

If too small, foldover becomes a problem.

SNR decreases with FOV_R (proportional to square).

Rectangular Field of View factor (RFOV)

Minimise for desired coverage in phase encoding direction

Reduces scan time

Foldover is increased

FOV_P = RFOVxFOV_R

(N_P reduces in same proportion as RFOV)

SNR is decreased

(Proportional to square root)

Zero filling/ interpolation

Apply in the slice direction

Doubles the number of reconstructed slices (but doesn’t improve resolution)

None