Given FOV = 20 cm x 20 cm and matrix = 256 x 224, what is the frequency resolution?

To calculate the frequency resolution in an MRI scan, you can use the formula that incorporates the field of view (FOV) and the matrix size. The frequency resolution is determined by dividing the FOV by the number of pixels in the frequency direction.

In this scenario, the FOV is given as 20 cm x 20 cm, and the matrix size is 256 x 224. The frequency resolution specifically corresponds to the frequency-encoding direction, which in this case, is determined by the number of pixels in that direction—256 pixels.

First, convert the FOV from centimeters to millimeters to maintain compatible units:

20 cm = 200 mm.

Now, using the frequency resolution formula:

Frequency Resolution = FOV in the frequency direction / number of pixels in the frequency direction.

Substituting the values into the formula gives:

Frequency Resolution = 200 mm / 256.

Calculating that results in approximately:

Frequency Resolution = 0.78125 mm.

When rounded, this value corresponds to 0.78 mm, which matches the choice labeled as B. This calculation confirms that the choice is accurate, reinforcing the importance of understanding how FOV and matrix size interplay to determine various spatial resolution measures in MRI imaging.