Final answer:
The contrast to noise ratio (CNR) in MRI is controlled by tissue properties, MRI sequences, and technical parameters such as echo time, repetition time, and magnetic field strength.
Step-by-step explanation:
The contrast to noise ratio (CNR) in MRI is controlled by several factors, which includes the inherent properties of the tissue being imaged, the type of magnetic resonance imaging (MRI) sequence used, and other technical parameters. Factors such as proton density, T1 and T2 relaxation times, and magnetic field strength directly affect CNR. Additionally, technical parameters like echo time (TE), repetition time (TR), flip angle, and acquisition matrix size can be adjusted to manipulate the CNR.