Hi, MRI safety manual says that whenever you are scanning a patient with a certain surface coil you should remove all unplugged coils from the bore during a scan. For example, if you have a head/neck + spine coil matrix with two coil ports and you are scanning only spine part then you should either connect the head part also or remove head/neck coil from the bore. I was wondering what is the physical mechanism that can cause patient burns? For example, if you scan patient's spine and leave the head coil unplugged. Is it because the unplugged coil is a resonant system designed to absorb RF energy so that when the scan is on and a pulse sequence with alot of RF (T2 FSE for example) is being used the coil can absorb alot of RF energy thus heating up? If the coil were plugged then the system can "detune the coil" and not heat up?! Another reason why unplugged coils should not be in the bore while scanning is the unplugged coil's coupling to patient which can cause increased noise, generate wrong flip angles etc. Another thing I have noticed is that for example, if a patient is sweating alot during a spine scan for example, the image quality is alot more worse. For example Sag spine images are alot more darker than usual. Is it due to sweat that is being "coupled" with the coil thus possibly messing up the flip angles in the patient which results in dark images? Thank you.