Getting an MRI done sometimes can be very frightening. The machine is very large, it makes loud noises, and you have to lay in a small tunnel while being scanned. The MRI consists of a very powerful electromagnet that is always turned on at 3.0 Tesla (the Earth only has a magnetic field of about 0.000058 Tesla, and a common magnet only about 0.001 Tesla).
Contrary to its appearance, however, the MRI procedure is very safe. MRIs on infants have been done safely for over 20 years and is approved by the US Food and Drug Administration (FDA) for use with infants. Tests done on the MRI have shown that it has no harmful effect on living organisms. The software used for our MRI (Trio 3.0 Tesla by Siemens) makes sure that the MRI procedure operates very safely within the parameters set by the FDA. Additionally, our MRI procedure only uses one or two radio-frequency pulses, while some MRI’s use up to 256 pulses. A sudden change of the magnetic field used by the MRI machine can have an affect on the body, but this MRI and all other MRI’s make sure that the magnetic field gradient doesn’t change too rapidly. The FDA’s threshold, which is probably one-third the actual minimum value for any problems, is 20 Tesla/sec. Our MRI (and most other clinical MRI’s) only operate at around 3 Tesla/second, which is well below the requirement.
One risk of the MRI is the magnetic field’s affect on any metallic objects near it. Inside the room where the MRI machine is located, a ferromagnetic metallic object, even something as small as a coin in a participant’s pocket, could become a dangerous projectile in the strong magnetic field. All our participants are therefore screened for metallics inside the body (e.g., heart pacemaker, defibrillator, neurostimulator, skull plates, metal pins, dental braces, bullet or bullet fragments, metal slivers, non-removable piercings), as well as required to remove any free metallic objects outside the body (belt buckles, shoes, diaper pins, coins) before they are allowed inside the room with the MRI. This risk is very easily minimized by being careful to remove any metal before screening.
Another risk of the MRI is the loud noise it makes. Some parts of the MRI procedure can get loud, up to 100 dBA, but participants are equipped with earphones and headphones, and the inside of the MRI is padded with foam for noise reduction, so the participant only hears around 70 dB of noise. 70 dB is a very reasonable amount of sound: a conversation is already 60-70 dB, a lawnmower is 90 dB, and car horns can reach up to 110 dB. Most of our participants will be babies, who usually sleep very well throughout the entire process. This is good evidence that our efforts to reduce the noise levels are successful!
During the MRI scan there will be several people present who have medical and MRI safety training, including a pediatric radiology nurse, a research assistant with MRI technology safety certification, and the PI. The pediatric radiology nurse has several years experience with these recordings and is certified for emergency safety procedures. Also, the parent may stop the experiment at any time, and the participant removed from the scanner in under 5 seconds.
The best way to conduct this study with infants is to conduct it when the babies are usually scheduled to sleep, around 8:00 or 8:30. The parent keeps the baby awake until the study, so that the babies are tired when they arrive. The parent and the baby (after removing all metallic objects) go inside the scanner room, where the parent performs the baby’s usual sleeping routine, such as rocking or feeding the baby. The baby is swaddled and placed on the MRI table, where it will fall asleep and be very secure during the whole process. Babies usually sleep through the entire process, which takes around 15-25 minutes. If the parent desires, he/she may stay in the room with the baby during the procedure. This way the process is not upsetting at all to the baby, and we get a good scan!