Notes of Medical images

Pagina 1

1 INTRODUCTION This part of the course will go through the basics of medical images acquisition and processing. We will see what the main techniques are used to inspect by images the human body, the principles of image processing techniques and how to extract relevant features from those images, eventually useful to later analyse and classify them automatically, as we saw for signals. BUT signal is a 1-dimensional sequence of values evolving in time, now we have a 2-dimensional set of information, which is fixed in time signals are defined in TIME DOMAIN // image are defined in the SPACE DOMAIN At first an image domain can be considered continuous, but still, we will deal with digital images. Therefore, the fundamental unit of information we will deal with is the pixel, that is what identifies the resolution. Medical images are usually defined in the grey scale, not in RGB. Most common grey scale is defined in the intensity range (0,255) In the course we will also address the physical principles that lie behind the acquisition of medical images. It is relevant since according to the instrumentation employed and the physical principle exploit in the interaction between the instrumentation and the body matter the resulting image is different and highlights/depicts different aspects/phenomena. Unlike photographic images in which cameras are used to capture the light intensity and/or colour of objects, each medical technology uses a different set of physical properties of living tissues to generate an image. For example, while MRI is based on the magnetic properties of a tissue, CT scan relies on the interaction between the x-ray beams and the biological tissues to form an image. In other words, in medical imaging sensors of different physical properties of materials…