What Makes The Scan Sounds in MRI Machines?
RF coil: The RF coil is a radiofrequency antenna that is used to send and receive radio waves to and from the patient’s body. The RF coil produces a variety of different sounds, depending on the type of scan being performed. These sounds can include banging, clicking, and whirring.
Gradient coil: The gradient coil is a set of coils that are used to create rapidly changing magnetic fields. These magnetic fields are used to create detailed images of the patient’s body. The gradient coil produces a loud knocking sound, which is the sound of the coils vibrating against the fiberglass mountings.
The sound level of an MRI scan can vary depending on the type of machine and the type of scan being performed. However, it is generally very loud, reaching levels of up to 130 decibels. This is equivalent to the noise level of a jet engine takeoff. For this reason, patients are always provided with earplugs or headphones to wear during the scan.
Here are some additional details about how each of the components listed above contributes to MRI scan sounds:
Cold head: The cold head uses a process called the Gifford-McMahon cycle to cool the liquid helium. This cycle involves compressing and expanding helium gas, which creates a temperature gradient. The liquid helium is then circulated through the cold head, where it absorbs heat from the superconducting magnet. The chirping sound produced by the cold head is caused by the rapid expansion and contraction of the helium gas.
RF coil: The RF coil produces sound when it is energized with radio waves. The type of sound that is produced depends on the frequency and amplitude of the radio waves. For example, low-frequency radio waves may produce a banging sound, while high-frequency radio waves may produce a clicking or whirring sound.
Gradient coil: The gradient coil produces sound when it is pulsed with electrical current. The pulsing of the current causes the coils to vibrate, which produces a knocking sound. The loudness of the knocking sound depends on the strength of the current and the frequency of the pulses.
It is important to note that the sound level of an MRI scan can be reduced by using different scanning techniques and by using newer MRI machines. However, some level of noise is always present, and patients should always be provided with hearing protection.