Today, most medical imaging modalities generate digital images, which can be easily manipulated by computers. The digital medical image is structural and functional information of human body in digital form. This laboratory activity focuses on digital picture element, known as pixel , generation. The digital image consists of pixels. Also, this laboratory creates an image of sine wave with different spatial frequency and phase.
Generally, the pixel is expressed in the two-dimensional arrays p (m, n) notation, where m is the row number and n is the column number of that particular pixel. The number of pixels in a digital medical image is its spatial resolution, which relates to the image quality.
By this point, you have studied X-ray radiography, and you probably see the limitations it has. To overcome some (but not all) of these limitations, computed tomography (CT) is used. In this lab, you will see how computed tomography works by using a method called back projection . You will determine one-dimensional cross-sections of a slice of the object being imaged at different levels by combining multiple back projections of the same slice. From these one-dimensional cross-sections, a two-dimensional slice can be made. Then, several two-dimensional slices will be combined to make a three-dimensional reconstruction. It is important to note, however, that usually doctors just look at the two-dimensional cross-sections to gather the information they need. Although three-dimensional reconstruction makes it easier to see the structure, it provides only minimal new information at the cost of computer time and memory.
The objective of this laboratory exercise is to generate a two-dimensional square or rectangular shape as a basic digital image with varying intensity. Using radon transform to create projection of the digital image and from projection data, create a CT image by back projection method.
- MATLAB software
- Image Processing Toolbox
1. Set up the MATLAB and create a white square object with black background.
Image dimension: 256 x 256 pixels