I recall watching my young daughter disappearing, head first, facing upwards into the tunnel of an MRI machine. She was given a buzzer to press if it became too frightening and I was impressed that she endured the whole examination without, apparently, pressing it. When she came out I asked if she had been frightened and she told me that she had never stopped pressing the buzzer! My guess is that it was not connected to anything.
A 15-item questionnaire measuring anxiety symptoms and relaxation symptoms which showed good psychometric properties was developed. The authors conclude: 'The MRI-AQ bridges a gap in knowledge and is a simple and useful tool for measuring patient anxiety during MRI examinations, during interventions, or when new procedures are introduced.'
You can listen to this as a podcast.
AHLANDER B.-M., ARESTEDT K., ENGVALL J., MARET E. & ERICSSON E. (2016) Development and validation of a questionnaire evaluating patient anxiety during Magnetic Resonance Imaging: the Magnetic Resonance Imaging-Anxiety Questionnaire (MRI-AQ). Journal of Advanced Nursing doi:1 10.1111/jan.12917