Basic concept of medical image processing

1. Pixel (Pixel), image size, image scale, Pixel & Resolution

Pixel:

Some of the smallest small rectangular blocks that make up a computer image are called pixels.
Image size (image scale):

If the entire image has 256*256=65536 pixels, this is the size of the image (size), also known as the scale of the image. The calculation formula of image scale is

That is, the scale s equals the number of pixels in the x direction of the image and the number of pixels in the y direction.

Pixel & Resolution:

Can be simply understood as, pixels = number of imaging units, Resolution = density. The pixel unit is px (pixel), it is not an absolute size , but a basic imaging unit, the size of a unit on different devices is not the same .

The size of the pixel itself corresponds to the size of the actual object space. Although the pixel size can be set as needed during image processing, the minimum size of the pixel is limited by the resolution of the imaging device itself. For example, an MR Scan

The resolution of the image generated by the instrument is that the smaller the cell size, the finer the image. The more cells in the same unit size, the larger the size of the image. Resolution is the number of pixels per unit size, commonly used in DPI(Dots per inch, commonly used in the printing industry) or PPI(Pixels per inch, often for display devices). The higher the resolution, the more delicate the image.

2. Intensity (Intensity), grayscale (gray level)

Pixels apart from physical dimensions, another important attribute is strength. In the case of black-and-white images, the intensity of the image is expressed in grayscale levels (gray level). Gray levels are often represented by a power of 2 , such as 8bit (256 grayscale, etc.).

Level). Also commonly used are 10bit,12bit and other gray levels.

Basic concept of medical image processing