select roi on the circle

Good day,

I hope someone can help me here.

I have a phantom CT image and want to select the objects (Roi). The objects are on a circle. Is there a way to convert this ROI to Cartesian coordinates. many thanks and best regards

[Sulaymon Eshkabilov]

Here are a couple of good examples how to work with ROI:Eg1., Eg2.

Answer 1

[Image Analyst]

Looks like you could simply create a mask using the code in the FAQ:

https://matlab.fandom.com/wiki/FAQ#How_do_I_create_a_circle?

Answer 2

[Latifa Bouguessaa]

Hello,

Thank you Sulaymon Eshkabilov and Image Analyst for your answer.

I have now segmented my phantom on the picture and determined the center of the phantom. but I couldn't cut the desired area (roi) on the picture.

I need to select an arc with Radius1=45 and Radius2=55 on the image. The center of the phantom has the coordinates X= 259 and y=252.

can someone help me??

Best regards

[Image Analyst]

Why do you need to cut it out (crop it)? That's probably not necessary. If you do you can do this

props = regionprops(mask, 'BoundingBox');
croppedImage = imcrop(grayImage, props.BoundingBox);