Question

1. How are the matrix and pixels related? Why are smaller pixels better for diagnostic quality?

Answer 1

How are the matrix and pixels related?

There are two types of images, analog and digital, used in medical imaging.
Analog images are the type of images that we, as humans, look at. They include such things as photographs, paintings, TV images, and all of our medical images recorded on film or displayed on various display devices, like computer monitors. What we see in an analog image is various levels of brightness (or film density) and colors. It is generally continuous and not broken into many small individual pieces.
Digital images are recorded as many numbers. The image is divided into a matrix or array of small picture elements, or pixels. Each pixel is represented by a numerical value.A digital image is composed of a matrix of pixel elements arranged in rows and columns.In general, the pixel value is related to the brightness or color that we will see when the digital image is converted into an analog image for display and viewing.Generally, at the time of viewing, the actual relationship between a pixel numerical value and it's displayed brightness is determined by the adjustments of the window control as discussed in other modules.

Why are smaller pixels better for diagnostic quality?

Increasing the matrix size, for example from 1024 to 2048 pixels, without changing the image field of view, will produce smaller pixels.This will generally reduce blurring and improve image detail.

The term pixel pitch describes the distance between dots (pixels) in an image. The smaller the distance between pixels, the better the resolution of the image. In digital radiography, the optimum pixel pitch is between 100-150 microns. It is because the human eye can resolve down to about 25 microns (for example, a human hair is about 40 microns), but at this minimal distance between pixels, an animal is exposed to high levels of radiation. At a large pixel pitch, you can use less radiation, but if you zoom in on a radiograph, the image will be grainy. The trade-off between exposure to radiation and image quality is optimized at 100-150 microns.