For how long can one scan at 4 W/kg under the 1st Level Controlled mode?

The correct response indicates that scanning can be conducted for up to 1 hour at a specific absorption rate (SAR) of 4 W/kg under the 1st Level Controlled mode. This duration is set to ensure patient safety while balancing the need for effective imaging.

The 1st Level Controlled mode is a designation used to indicate an environment where the MRI system has specific operational protocols to protect patients from excessive exposure to radiofrequency (RF) energy. The time limit of 60 minutes is consistent with guidelines established by regulatory bodies that monitor the safety of MRI procedures. These guidelines are designed to prevent adverse effects related to thermal injuries or other RF exposure complications potentially arising from lengthy scans at higher SAR levels.

By adhering to this time limit, practitioners can avoid overheating tissues and ensure patient comfort during the imaging process. The careful monitoring and regulation of exposure ensure that the risks are minimized while achieving high-quality imaging results.