Final answer:
To increase the overall image signal-to-noise ratio (SNR) with a low scan time, increasing the number of excitations (NEX) can be helpful. This yields more signal averaging and thus a higher SNR, but at the expense of longer scan times.
Step-by-step explanation:
When dealing with a noticeable lack in signal-to-noise ratio (SNR) and a low scan time, such as 2 minutes, an increase in number of excitations (NEX) will help increase the overall image SNR. In the context of magnetic resonance imaging (MRI), several parameters can influence the quality of the image obtained. The SNR is a critical factor that denotes the clarity and quality of the MRI scan. By increasing the NEX, you are essentially increasing the number of times the signal is sampled. More samples lead to a better average and therefore, higher SNR at the cost of increased scan time.
However, there's a trade-off that must be considered; increasing NEX will result in longer scan times, which can be a limitation if quick scans are necessary or if the patient's condition does not allow for longer periods of immobility. Nevertheless, if the scenario permits extended scan time, and the goal is to enhance image quality, NEX is a viable variable to adjust. It's also important to note that while increasing NEX improves SNR, it does not necessarily enhance spatial resolution which depends on other parameters such as field of view, matrix size, and slice thickness.