In MRI, scan time is an important factor, but it is typically not adjusted primarily for the sake of improving image quality. Instead, it is often determined by the specific protocol being used and the clinical situation. While a longer scan time can sometimes result in improved signal-to-noise ratio (SNR) and therefore better image quality, it is generally balanced with the need for patient comfort and efficiency in a clinical setting.
On the other hand, layer thickness, matrix size, and field of view are all parameters that can be directly manipulated to enhance image quality. Reducing layer thickness can lead to improved spatial resolution; increasing matrix size improves the detail seen in images; and adjusting the field of view can optimize how much anatomy is captured in the image. Each of these parameters interacts with the others and has a more direct impact on the overall quality of the MRI scan, which is why they are routinely adjusted during imaging procedures.