DICOM image of size 614 x 816 and laptop monitor 96dpi.What is 1 pixel in mm ???

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vaishali 2013-9-21

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According to 96 dpi 1 pixel = 0.264583333; According to image size 614 x 816: 501024 pixels in..?... (m ,cm ,mm no idea )

from my results i guess it is 1 pixel = 0.050696174;

Am i right???If not why if yes i need proof.

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Answer 1

Walter Roberson 2013-9-21

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96 dpi is, by definition, 96 dots per inch. In the context of monitors, a dot is a pixel, so 96 dpi is 96 pixels per inch. Then 1/96 is the number of inches per pixel. There are 25.4 mm per inch, so 25.4 / 96 is the number of mm per pixel. And that is the 0.264583333 number you see.

614 pixels x 816 pixels = 501024 pixels squared. It isn't a linear measurement, it is an area.

One square pixel is (0.264583333)^2. And that makes 501024 pixels squared = 501024 * (0.264583333)^2 = about 35073 mm^2 (roughly 3.5 decimeters squared)

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vaishali 2013-9-22

while pixel conversion only need to consider monitor DPI or the actual size of the object in the image???

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Answer 2

Image Analyst 2013-9-21

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Why do you care what size it is on the monitor? It would be a different size on a 15", a 17", a 19" a 23" etc. monitor. Don't you really care about the actual size of the object in the image?

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Image Analyst 2013-9-22

编辑：Image Analyst 2013-9-22

You need to have something in your image of known size that you can calibrate against. For example if you put a ruler or other object of known size in your image, then you measure its length in pixels. That will let you know the cm per pixel spatial calibration factor. That factor will not depend on what size monitor you display it on and will not depend on any DPI setting for any monitor or printer that you display the image with.

Image Analyst 2013-9-22

You can put a ruler in your scene and take a picture of it. I don't know how to explain that any better. If you trust your expert to click on two points and tell you how many cm it is, then fine, you can do that.

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