What parameter is primarily adjusted to control the amount of noise in MRI images?

The amount of noise in MRI images is primarily controlled by adjusting the number of excitations (NEX). Increasing the NEX improves the signal-to-noise ratio (SNR) because it involves acquiring multiple averages of the same data. This averaging process reduces the random noise present in the image, effectively enhancing the overall quality and clarity of the MRI scan. Thus, by increasing the NEX, the noise is diminished relative to the actual signal from the tissues being imaged, leading to clearer and more diagnostic images.

In contrast, matrix size, TR (repetition time), and TE (echo time) influence other aspects of image quality and acquisition parameters, but they do not directly control the amount of noise. Matrix size affects spatial resolution but may not have a substantial impact on noise levels. TR and TE are critical in timing aspects of imaging and tissue contrast but are not the primary factors in managing noise. Therefore, focusing on the NEX parameter is essential for effectively controlling noise in MRI imaging.