If you chose Sag, Cor or Ax on the Sequence Information page you will now need to enter explicitly all the parameters relating to the Scanning Range that you require for your scan prescription.

Figure 1. Scanning Range menu window.

From the Scanning Range window the Field of View, Slice Thickness and Gap and the Slice Positions are set. These parameters will determine the scanning coverage and, together with the Matrix Size, the pixel resolution that you will obtain in your images.

READ FIELD OF VIEW will set the field of view in the Read, or Frequency, direction. Type in the required size in mm.

PHASE FIELD OF VIEW will set the field of view in the Phase Encode direction. Type in the required size in mm. To avoid phase wrap use a field of view larger than the area of anatomy being imaged. (Alternatively you might swap the direction of phase and frequency encoding later in the scanning prescription).

SLICE THICKNESS: Type in the required slice thickness in mm.

SLICE GAP: Type in the required gap between the slices in mm. If you want contiguous slices then enter "0".

START POSITION and END POSITION: Type in the start and end positions you require for your slices in mm relative to the magnet's isocentre. These values, together with the slice thickness and gap, will determine the number of slices acquired. The number of slices in your prescription will be calculated if you type a [RTN] in the Position fields. If necessary, the End Position will be amended to the nearest valid value that fits your prescription.

Note that Right, Anterior and Superior are Positive co-ordinates relative to the isocentre with Left, Posterior and Inferior being negative. Therefore, if you wish to plan slices from 20mm left of the isocentre to 20mm right of the isocentre you would need to type in -20 at the Start Position prompt and 20 at the End Position prompt.

INTERLEAVE SLICES: Use this option to select either interleaved slice acquisition (slice 1, 3, 5, 7 collected, followed by slice 2, 4, 6, 8 etc. in a TR period) or sequential slice acquisition (slice order 1, 2, 3, 4, 5, 6, 7, 8 etc. in a TR period). Interleaved acquisition is advised for spin echo acquisitions.