In this question, I would like to focus on intensity value of the CT Scan. First, take a look at the image below:
The upper image is the original image, while the lower image is the thresholded version. In order to measure volume of any shape, theoretically, it is possible to simply just count the number of voxels in the image. However, the outermost layer of the object (ex. nodule) shows darker intensity, while all voxels inside the object have very high intensity. If I simply count the voxels in the thresholded version, I will highly likely to get a result volume larger than the actual volume for the lung nodule.
I also see that there are variables such as window center (level) and window width, which can be used to adjust the DICOM image's intensity information. Different intensity can alter the result volume.
So here is the question: if I am to measure any given lung nodule, what should I do in order to achieve the best possible precision? When should we ignore the lower intensity voxels? Or must I do this in some other ways?