As part of his clinical diagnosis, Brian was referred to undergo a MRI scan. In this video
we follow him through the process from his arrival at the imaging clinic, through the
various pre-scan procedures that are involved to ensure a safe scan and so we show you what
to expect if you are referred for a scan. After arrival at the clinic and presentation
at reception you will be asked a number of questions that relate to the fact that you
are about to enter a very strong magnetic field. This screening questionnaire is extremely
important in ensuring that it is safe for you to enter the magnet. Any metallic object
either inside or outside your body can be potentially dangerous, so it is essential that the
clinician or MR technician is informed if there is anything potentially harmful present.
The questions will attempt to determine whether there is a risk of any medical implants or
clips, lodged metal fragments, whether you are pregnant, wearing magnetic clothing or
jewellery, have tattoos, concurrent illness or history of illness, and will ask you about
medications or allergies in the event that contrast media is to be administered. If you
are unsure about any questions please ask the MR technologist for advice. Do not answer
no to any question you do not definitely know the answer to. After completing the questionnaire
and if the MR technician is satisfied that it is safe to proceed with your scan, you
will most likely be asked to change out of your clothes into a hospital gown or scrubs.
The MR technologist will again check for metals and then guide you into the magnet room. Due
to the loud noise generated by the pulsed field gradients, it is necessary to wear ear protection.
The MR technologist will position you correctly for the scan on the movable
scanner bed and ensure that you are comfortable. It is essential that you remain as still as
possible during the scan which may last for between 15 and 45 minutes depending on the
protocols specified by the clinician. A motorized bed will then slowly guide you into the magnet
and a laser cross hair is used for accurate positioning. In some cases earphones are used
to allow better communication with the technologist, further reduce noise levels and to listen
to music during the scan. A pneumatic squeeze bulb triggers an alarm should there be any
emergency and you need to stop the scan. For brain scans, a special head RF coil will be
placed over your head. Different coil types may be used for imaging other parts of the
body. Once the scanning begins and gradient coils are pulsed, the acoustic vibrations
give rise to very loud staccato noise patterns. The sounds vary according to the imaging sequence
being used. Here are some typical gradient noise sequences that you may hear.
You may also hear pumping noises associated with the refrigeration unit helping to reduce the evaporation
of cryogens in the magnet. During the scan, the technologist will talk to you to let you
know when scans are to begin and to ensure you are still comfortable. Once the suite
of scans has been completed and the technologist is happy that they are of sufficient quality,
your scan is done and you will be helped out of the magnet. So I hope this example of the
process of having an MRI scan helps you to prepare for your own scan. I trust you've
enjoyed this section, on the fundamentals of MRI.