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I have two dicom files with the following Image Patient Position (IPP) and Pixel Spacing (PS)

img1, has PS of 2mm IPP of (-256,-256,-128)

img2 has PS of 2.5mm and IPP of (-206,-201,-128)

For image restration / alignment, I understand I need to have both images with the same PS and IPP

My first step is to bring img1 to PS of 2.5mm i.e. interpolate img1 by 1.25 (2.5/2) times to match that of img2.

**Pixel Spacing Calculation:**

2mm = 1pixel

2.5mm = 1/2 *2.5 = 1.25pixel

Do this mean that the IPP of img1 will also change to (-320,-320,-128) i.e. by 1.25 (-256*1.25) times as well?

Thanks a lot in advance

Ash

Ash
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1 Answers1

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No, the IPP defines the position of middle of the top left pixel of the image in patient/world coordinates. You might need to apply the scaling to the position to achieve sub-pixel accuracy.

Markus Sabin
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