In an MRI scan, which of the following is a critical operational procedure?

In the context of MRI operations, ensuring that coils are always plugged in before scanning is crucial because the coils play a vital role in the acquisition of image data. Coils are responsible for both transmitting radiofrequency pulses and receiving the emitted signals from the patient during the scan. If the coils are not properly connected, the MRI scanner cannot function optimally, which can lead to poor image quality or even a failure to obtain images altogether.

While performing routine maintenance on coils, recalibrating the magnet, and limiting patient movement are all important aspects of MRI operations, they do not directly impact the immediate functionality of the scanner in the same way that ensuring the coils are properly plugged in does. Regular maintenance and recalibration are part of good practice but do not require attention immediately before each scan as plugging in the coils does. Similarly, limiting patient movement is a goal during the scanning process but is dependent on factors outside the immediate operational procedures of the MRI machine. Thus, ensuring coils are connected is regarded as a critical step for ensuring successful MRI scans.