How to calculate actual size of an object in a dicom image?

I have a dicom image of CT scan. Regionprops returns area in pixels. Is there any other way in Matlab to get the actual sizein cms/mms?

Answer 1

[Image Analyst]

Hopefully there is something in your dicom header that gives the spatial calibration in real world units per pixel.

[Sparkle89]

I found a parameter called PixelSpacing in the dicom header. Is that equivalent to XResolution and YResolution in PNG file header?

[Walter Roberson]

PixelSpacing is what you want for 2D. It measures pixel center distance so you can get outer distance by multiplying the number of pixels by the spacing.

The situation in 3d is more complicated.

[Sparkle89]

Thank you Sir.

Pixelspacing returns spacing in mms.

Therefore is the following calculation of size obtained by multiplying area obtained from regioprops by [pixelspacing.x pixelspacing.y] correct?

%PixelSpacing value from dicom header 
% area returned by regionprops
area_in_mm = area .* [PixelSpacing.xvalue PixelSpacing.yvalue]; 

[Image Analyst]

No, more like

area_in_mm = area * PixelSpacing.xvalue * PixelSpacing.yvalue; 

Answer 2

[nehad mohamed]

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

[Image Analyst]

See my attached spatial calibration demo. Adapt as needed.

[nehad mohamed]

error

i want measure distance between to selected point on dicom image and save this distance on excel file

[Walter Roberson]

What error did you run into?

[Image Analyst]

Looks like you forgot to read the posting guidelines. Here they are again:

TUTORIAL: How to ask a question (on Answers) and get a fast answer

[nehad mohamed]

error in measure distance with cm on dicom image

[Walter Roberson]

You already said that you get an error when doing that, but you did not tell us what the error message is, and you did not make your code available for us to review.

[nehad mohamed]

error in function draw line[]

[Image Analyst]

nehad, it looks to me like you totally ignored my comment when I asked you to read this link:

TUTORIAL: How to ask a question (on Answers) and get a fast answer

Your last comment proves that. So after you read that, start your own discussion thread since this is not an official Answer to Sparkle89's question, and we don't want to be sending them emails with every post about this non-Answer.

[Walter Roberson]

Take. A. Picture. Of. The. Error. Message. And. Attach. The. Picture. 🥺

Answer 3

[nehad mohamed]

[nehad mohamed]

this my error and my code

iwant tools like ruler to measure distance and save this distance in excel sheet

[Image Analyst]

Again:

nehad, it looks to me like you totally ignored my comment when I asked you to read this link:

TUTORIAL: How to ask a question (on Answers) and get a fast answer

Your last comment proves that. So after you read that, start your own discussion thread since this is not an official Answer to Sparkle89's question, and we don't want to be sending them emails with every post about this non-Answer.

If you want, you can put a link to your new thread back here. That's all.