First let's review what are the factors that affect the quality of a CT image a***: The most important factor is the CT resolution, followed by a part of the preparation before the examination .
Then the main preparations for the examination are:
1. Remove high-density objects from the surface of the body, and try to get the patient to cooperate as much as possible during the examination.
2. One week before the examination can not be digestive barium meal examination and no history of swallowing high-density tablets.
3. Contrast allergy testing is required for imaging.
Next are the CT parameters:
1. Density resolution. Density resolution is affected by scanning layer thickness, noise, number of photons, object size, and detector sensitivity, among which noise is the most important influence.
2.Time resolution. Temporal resolution: is the time it takes for a CT device to acquire a layer of complete image data that can be reconstructed. The shorter the time the higher the resolution.
3. Spatial resolution. Influenced by pixel, focus, detector size, reconstruction range and reconstruction matrix, scanning layer thickness, pitch, reconstruction algorithm. The spatial resolution is closely related to the size of the pixels; the larger the pixels and the smaller the number, the lower their spatial resolution. On the contrary, the smaller the pixel, the higher the number, the higher the spatial resolution.
4. Noise. Noise is characterized by uneven CT values of pixels in a homogeneous object image, which results in a grainy image and reduced density resolution.
5. Artifacts. There are two main aspects: (1) equipment causes; (2) patient causes: motion artifacts and beam hardening artifacts.
6. Choice of window width and position.
7. Suitable scanning field.