Digital imaging
Digital imaging has four basic image quality characteristics: bit depth, matrix, voxels, and pixel. It contains a 2D rectangular-shaped arrangement of numbers known as the matrix. The operator must choose the matrix size, also called field of view (FOV). Large images have a large matrix, and they take longer to process. Pixels are individual matrix boxes that have a number representing the brightness level. A large matrix has a smaller pixel. A voxel is the patient’s volume of tissue. Its information is expressed in the pixel in numerical value. Bit depth is the number of bits per pixel.
The modulation transfer function (MFT) is defined as a component’s spatial frequency response. It changes the contrast values of various objects into the image’s contrast intensity levels. MTF describes the levels of contrast and blurs over different spatial frequencies.
Image brightness is the overall lightness of the image. Contrast means the images’ difference in brightness. An image has to have the required brightness and contrast for it to provide ease of viewing. For example, a black dog in a black background will have poor contrast, while a white dog in a black background will have good contrast. Brightness and contrast must be adjusted appropriately to produce a visible image.
Digital image processing is the skillful influence of pictorial information to magnify the original images’ visual qualities. It helps exaggerate some details to make the final image impressive. The first principle is to program a machine to produce the desired image, enhancing characteristics that impress the human eye. The second principle is an image analysis system that comprises a computer, a display screen, a video camera, and a microscope. The photographer must maximize the camera sensitivity, and the microscope must provide optimal illumination.
The assessment of image quality is a significant step in digital radiography. The elements that measure the digital radiographic performance are the detective quantum efficiency (DQE, the modulation transfer function (MTF), and the noise power spectrum (NPS). NPS is a frequency’s amplitude variance. MTF provides a digital radiographic system resolution.