# Calculating FOV from DICOM headers

Hi all.

I am trying to estimate the FOV (field of view) using information that is available in the header of my dicom fMRI image.

There is no FOV tag in my Dicom header.

Is it correct to use this equation ?
FOVx = “Columns (0028,0011)” * first element of “Pixel Spacing (0028,0030)” ?
FOVy = “Rows (0028,0010)” * second element of “Pixel Spacing (0028,0030)” ?

PS: Pixel Spacing is the voxel size in x and y axis in mm.

Yes, this formula will work for most DICOM images. However, it will fail for mosaics (often used with Siemens V* series scanners). For example, consider these mosaics where your formula would suggest 1284mm (384 * 3.25) instead of 208mm (64 * 3.25).

Be aware that distance between slice centers can be trickier to calculate. The most reliable method is to calculate the Euclidean distance between the Image Position (0020,0032) tag of two neighboring slices.

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Thanks for the prompt reply. So, for non-mosaics, standard DICOM images, my initial post is correct, right?

For all the cases I can think of.

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Hi!

Thanks a lot for your reply. Do you know how we can check if the image is mosaic?
And where this number 64 comes from (which dicom field) for mosaic images?

Is this a mosaic image (from DICOM header)?
(0008, 0008) Image Type CS: [‘ORIGINAL’, ‘PRIMARY’, ‘M’, ‘ND’, ‘MOSAIC’]