The "imgradient3" function in MATLAB is designed to compute the gradient magnitude and direction of a 3-dimensional grayscale image. The input to this function can indeed be a 3D binary image or a 3D grayscale image. When you're working with DICOM slices, which are typically 2D slices of a 3D volume, you need to stack these slices together to form a 3D volume before you can use "imgradient3".
You can read the dicom files using the "dicomread" function, then create a 3D image by stacking the slices and then feed into the "imgradient3" function and get the gradient magnitude and direction. You can refer to the following MATLAB Answer for more information on how to do this:
In case of the example you have mentioned, "vol" that is fed into "imgradient3" is a 128×128×27 uint8 array, i.e. It has 27 images each of the size 128x128 pixels.
Hope this helps!
