“higher intensity” and “high signal intensity” in images

Question

I'm newbie in Computer Vision and image processing.

I'm reading the article "Automated White Matter Hyperintensity Detection in Multiple Sclerosis Using 3D T2 FLAIR" and it said:

2.2.4. WMH Segmentation with High Spatial Frequency Suppression

White matter lesions have higher intensity and generally clear boundaries relative to the surrounding WM. Unfortunately, in the 3D T2 FLAIR images, the GM can also present with high signal intensity, especially in elderly people.

What does it means "higher intensity" and "high signal intensity"?

I think it means that white matter lesions are very white but I'm not sure because I don't understand why the use the words "intensity" and "signal" when they are talking about images.

Answer 1

The intensity of a pixel is its value (e.g., from 0 to 255). For instance, in a black-and-white/grayscale image, pixel intensity 0 means the pixel is black, and pixel intensity 255 means the pixel is white; intensities in between the two are shades of grey.

"White matter lesions have higher intensity" means that the pixels in the area of a white matter lesion have higher intensity values.

In this context "signal intensity" is presumably a synonym for "intensity".