How can i convert pixels to mm for a specific Dicom Image?

I want to find the length of a pixel in milimeter(mm).

For other images, I can extract it via the'Xresolution','Yresolution','unit' parameters obtained from the 'iminfo'command.

Can 'dicomimfo' give those properties?

Or is there any other way to convert pixels to mm for dicom images?

[Joseph Cheng]

are you looking for the pixel pitch like each pixel is 14x14 microns or are you looking for something like the length of the table in the image is 2 meters? you'll need to know additional data for the later like the focal length to calculate that and i'm not sure that info is stored in Dicom images.

[Pratik Datta]

Actually, I am working on extracting Nodules from a CT image of Lung.

So,I need to determine whether the size of the nodules is less than or greater than 30mm.

I have a binary image of lung region containing the nodules and have used 'Regionprops' to find the Major Axis Length,MinorAxisLength..etc of all the objects in the image given below.

All of those values are in pixels,so i need to convert them to mm and compare.

Can you suggest a way?

[Walter Roberson]

If you are going to tag a specific person (which you should avoid doing) then you need to at least get the name right!

http://www.mathworks.co.uk/matlabcentral/answers/43073-a-guide-to-tags

[Pratik Datta]

Sorry for the mistake.Will keep in mind the next time.

Answer 1

[Walter Roberson]

Use dicominfo() to fetch the PixelSpacing parameter for the image. See this description of computing some of the location information from DICOM files

[Pratik Datta]

It worked.Thanks for ur help.

[Yassir Garoiaz]

Hi , where can i get pixelspacing info plz , i want calculate the pixel size in an image

[Walter Roberson]

https://www.mathworks.com/matlabcentral/answers/302853-how-can-i-calculate-the-area-of-white-pixels-of-binary-image-in-mm2#comment_390733

Where I gave the example

dinfo = dicominfo('TheFileName.dcm');
spacing = dinfo.PixelSpacing;
per_pixel_area = spacing(1) * spacing(2);
num_white_pixels = nnz(binarized_img);
total_white_area = num_white_pixels * per_pixel_area;

See however http://stackoverflow.com/questions/14930222/how-to-calculate-space-between-dicom-slices-for-mpr when trying to extend to 3D.

[Neda]

I was wondering how can I convert pixel to the mm while my image is a mat file (uint 8). For example, I have a kernel size of 11 * 11 and another one a kernel size of 21 * 21, and I need to know what is equivalent of these sizes in mm?

[nehad mohamed]

I want a tool like a ruler to measure distances in dicom images. In cm. using matlab