How does an MRI machine work?

Summary

This script delves into the workings of MRI technology, which uses magnetic fields and radio frequency pulses to create detailed images of internal body tissues. It explains how water composition in the body, particularly the hydrogen atoms, is crucial for MRI imaging. The script also touches on the differences between healthy and diseased tissues, the role of gradient coils in targeting specific areas, and the importance of RF coils in generating the diagnostic images. The video aims to educate viewers on the principles behind MRI, making complex medical technology more accessible.

Takeaways

• 🧲 MRI scans use magnetic fields and radio pulses to create detailed images of internal body structures, aiding in diagnosis of conditions like brain hemorrhage or blood clots.
• 🌀 MRI machines consist of strong electromagnets, gradient coils, and RF (radio frequency) coils to generate the necessary magnetic fields and radio frequency pulses.
• 💧 The human body's water composition is crucial for MRI imaging, as the magnetic field realigns water molecules, which then emit signals when perturbed by radio pulses.
• 🔍 The difference in water composition between healthy and unhealthy tissues allows MRI to distinguish between them, providing clear images for medical analysis.
• 🌀 Hydrogen atoms in the body, which have a small magnetic field, are aligned by the MRI's magnetic field and then flipped by radio frequency pulses, emitting signals as they return to their original state.
• 🔧 The resonance frequency, determined by the Larmor equation, is key to MRI imaging, as it dictates the frequency at which hydrogen atoms will flip in response to the RF pulses.
• 📊 Phase and frequency encoding, along with Fourier transformation, are used to generate detailed 2D images from the signals emitted by hydrogen atoms.
• 🧲 Gradient coils in the MRI machine create varying magnetic fields to select and image specific parts of the body, with different sets of coils for the X, Y, and Z directions.
• 🛠️ The electromagnet in an MRI machine is a critical component, often superconducting and much stronger than common household magnets.
• 🔄 RF coils come in various designs, categorized as surface or volume coils, and are tuned to resonate at the same frequency as the part of the body being imaged.
• 📚 The script also mentions the importance of supporting the creators on Patreon, indicating an educational and community-driven aspect of the content.

Q & A

What is the primary use of MRI scans in the medical field?

MRI scans are primarily used for diagnosis in cases such as detecting brain hemorrhages or blood clots deep inside the brain where direct observation is not possible.

How do MRI machines create detailed images of the human body's organs and tissues?

MRI machines use varying magnetic fields and radio frequency pulses to create detailed images of the organs and tissues in the human body.

What role does water composition play in MRI imaging?

Water composition is crucial in MRI imaging because the human body is made up of about 60% water, and the water molecules in the body are temporarily realigned by the magnetic field during an MRI scan.

How does the MRI scanner operator manipulate the hydrogen atoms within the body during an MRI scan?

The scanner operator uses RF coils to send radio pulses that cause the aligned hydrogen atoms to flip, and then these atoms re-emit RF signals as they realign with the magnetic field, which are used to create MRI images.

What is the significance of the resonance frequency in MRI imaging?

The resonance frequency, determined by the Larmor equation, is significant in MRI as it is the frequency at which the hydrogen atoms resonate and flip in response to the RF pulses.

How do MRI images differentiate between healthy and unhealthy tissues?

MRI images differentiate between healthy and unhealthy tissues by analyzing the unique water composition of each tissue; changes in water composition due to a blood clot, for example, allow for clear distinction between the two.

What is the role of gradient coils in MRI imaging?

Gradient coils are used to select specific parts of the brain for imaging by producing varying magnetic fields in the X, Y, and Z directions, which helps to localize the area of interest.

How do the RF signals emitted by hydrogen atoms contribute to the formation of MRI images?

The RF signals emitted by hydrogen atoms as they return to their normal orientation are received by the computer, which converts these signals into images using phase and frequency encoding with the help of Fourier transformation.

What are the two main types of RF coils used in MRI scanners?

The two main types of RF coils used in MRI scanners are surface coils, which rest on the surface of the object being imaged, and volume coils, which are designed to cover a larger volume.

Why are superconducting magnets commonly used in MRI machines?

Superconducting magnets are used in MRI machines because they provide a strong and constant magnetic field, which is essential for high-quality imaging. They are typically much stronger than household magnets.

How does the FEA simulation help in understanding the MRI process?

FEA (Finite Element Analysis) simulation helps visualize the magnetic fields produced by electromagnets and gradient coils, as well as the magnetic flux density in RF coils, providing a deeper understanding of how MRI machines function.

Outlines

00:00

🧠 MRI Technology and Its Medical Applications

This paragraph introduces the use of MRI scans in diagnosing medical conditions such as brain hemorrhages and blood clots. It explains the MRI process, which involves using magnetic fields and radio pulses to create detailed 2D images of organs and tissues. The human body's water composition plays a crucial role in MRI imaging, as the magnetic field realigns water molecules, and radio frequency pulses cause these molecules to emit signals that are captured to form images. The paragraph also touches on the differences in water composition between healthy and unhealthy tissues, which MRI can discern, and the role of hydrogen atoms in this imaging technique.

05:03

🛠️ Components of an MRI Machine and Their Functions

The second paragraph delves into the components of an MRI machine, including the electromagnet, which generates a strong magnetic field, and the RF coils, which are categorized into surface and volume coils. The electromagnet is a key element, with superconducting magnets ranging from 0.5 to 3 Tesla being common. The paragraph also discusses the importance of gradient coils, which provide linear gradients of the magnetic field to allow for the imaging of specific body regions. The use of FEA simulations to analyze the magnetic field produced by the x-axis gradient coil is mentioned, showing the variation in the magnetic field and how it is utilized in MRI imaging.

Keywords

💡MRI scans

MRI, or Magnetic Resonance Imaging, is a medical imaging technique that uses strong magnetic fields and radio waves to generate detailed images of the body's internal structures. In the video, MRI scans are highlighted as a crucial diagnostic tool for conditions such as brain hemorrhages or blood clots, where they provide doctors with the detailed 2D images necessary for precise surgical planning.

💡Magnetic fields

Magnetic fields are a fundamental aspect of MRI technology. The video describes how MRI machines use varying magnetic fields, generated by electromagnets and gradient coils, to align the water molecules in the body. These fields are essential for the process of imaging, as they interact with the hydrogen atoms in the body, which are then detected to create the MRI images.

💡Radio frequency (RF) pulses

RF pulses are electromagnetic pulses used in MRI to excite the hydrogen atoms that have been aligned by the magnetic field. As mentioned in the script, the scanner operator uses RF coils to send these pulses, causing the hydrogen atoms to flip, which is a key step in the imaging process. The RF signals emitted by the atoms as they realign are captured and used to create the MRI images.

💡Gradient coils

Gradient coils are part of the MRI machine and are used to create varying magnetic fields across the body. The script explains that these coils produce opposite magnetic fields to create a gradient, which allows for the selection of specific parts of the body for imaging. This is crucial for generating detailed images of particular regions, such as different parts of the brain.

💡Water molecules

Water molecules, which make up about 60% of the human body, play a significant role in MRI imaging. The video script notes that when a person is inside an MRI machine, the magnetic field realigns most of the water molecules in the body's cells, which is essential for the imaging process. The hydrogen atoms within these water molecules are particularly important due to their magnetic properties.

💡Hydrogen atoms

Hydrogen atoms are highlighted in the script as having a small magnetic field and behaving like tiny bar magnets. Their orientation within the body is random until exposed to the external magnetic field of the MRI machine, at which point they align and are excited by RF pulses. The behavior of these hydrogen atoms is central to the creation of MRI images.

💡Resonance frequency

Resonance frequency, as discussed in the video, is the frequency at which the hydrogen atoms resonate when exposed to the magnetic field. This frequency varies with the strength of the external magnetic field and is critical for the MRI process. The script mentions that the resonance frequency is used to determine the correct RF signal frequency needed to excite the hydrogen atoms.

💡Phase and frequency encoding

Phase and frequency encoding are techniques used in MRI to generate detailed images. The script explains that these encoding methods, along with Fourier transformation, are used to process the RF signals received from the body to create the cross-sectional 2D MRI images. This encoding is essential for distinguishing between different types of tissues and for producing high-resolution images.

💡Fourier transformation

Fourier transformation is a mathematical process used in MRI to convert the time-domain signals from the body into spatial-frequency domain data, which can then be used to create images. The script mentions this transformation as a key part of the process that translates the RF signals into the detailed 2D images that are the end result of an MRI scan.

💡Superconducting magnet

The superconducting magnet is the main component of an MRI machine that provides the strong magnetic field necessary for imaging. As described in the script, these magnets are continuously on and are significantly stronger than household magnets. The strength of the magnet, measured in Tesla, is a critical factor in the quality of the MRI images produced.

💡RF coils

RF coils are essential components of the MRI machine that send and receive RF signals. The script discusses different types of RF coils, such as surface coils and volume coils, which are designed to interact with the body's tissues to produce the magnetic resonance signals that are used to create images. The design and tuning of these coils are crucial for the quality of the MRI scans.

Highlights

MRI scans are crucial in diagnosing conditions like brain hemorrhages and blood clots that are not visible to the naked eye.

MRI imaging uses magnetic fields and radio pulses to create detailed 2D images of internal organs and tissues.

The human body's water composition plays a vital role in MRI technology due to the magnetic properties of hydrogen atoms.

When inside an MRI machine, water molecules in cells are realigned by the magnetic field, aiding in imaging.

Radio frequency (RF) signals are used to flip the aligned hydrogen atoms, which then emit signals as they realign.

Each tissue has a unique water composition, allowing MRI to differentiate between healthy and damaged tissues.

The resonance frequency of hydrogen atoms, determined by the Larmor equation, is key to MRI imaging.

The MRI process involves striking an RF pulse to flip hydrogen atoms, which then emit signals detected by the machine.

Unhealthy tissue with more hydrogen atoms generates different RF signals, aiding in diagnosis.

Phase and frequency encoding with Fourier transformation is used to generate detailed MRI images.

Gradient coils in MRI machines select specific parts of the body for imaging by altering magnetic field strength.

The main electromagnet in MRI machines provides a constant magnetic field, with gradient coils adjusting it for imaging.

Superconducting magnets, ranging from 0.5 to 3 Tesla, are used in MRI machines for their strong magnetic fields.

RF coils in MRI scanners come in various designs, categorized into surface and volume coils.

Surface coils in MRI lie on the surface of the object being imaged, enhancing the magnetic flux density.

FEA simulations demonstrate the distribution of magnetic flux density in RF coils during MRI.

The resonant frequency of the RF coil is tuned to match the part of the body being imaged for optimal results.

Transcripts

you might have seen this on TV or some

of you might have even experienced this

strange procedure firsthand

MRI scans are used in the medical field

for diagnosis

in cases such as a brain hemorrhage a

blood clot occurs deep inside the brain

where doctors can't see

an MRI scan produces a very detailed 2D

image of the brain allowing doctors to

analyze the damaged tissue and then

perform their targeted surgery

let's take a deep dive into how MRI

imaging works and the principle behind

it

MRI is a technique that uses varying

magnetic fields and radio pulses to

create detailed images of the organs and

tissues in the human body

MRI machines have tube-shaped strong

electromagnets gradient coils and RF

coils to generate strong varying

magnetic fields and radio frequency

pulses

using the help of em Works in this FEA

simulation we can see the magnetic

fields produced by electromagnets

uniform magnetic fields are produced

inside the bore

now let's focus on the effect of

magnetic fields and radio frequency

signals on the body

the human body is made up of 60 water

and water composition surprisingly plays

an important role in this technique

when you lie inside an MRI machine

the magnetic field generated by the

electromagnets and gradient coil

temporarily realigns most of the water

molecules in your cells in the direction

of the magnetic field

the scanner operator commands RF coils

to send radio pulses causing these

aligned atoms to flip

within a few seconds the atoms realign

with the magnetic field emitting an RF

signal

this RF signal is used to create

cross-sectional 2D MRI images

we'll expand on this brief explanation

of MRI imaging technology later on

first let's explore the difference

between healthy and unhealthy tissues in

the human body each tissue has its own

unique water composition

when a blood clot happens in a certain

tissue it changes the water composition

of that area

this allows us to clearly see the

difference between healthy and damaged

tissues

let's narrow our focus on the water

molecules inside our tissues

the water molecule has two hydrogen

atoms

this hydrogen atom has a small magnetic

field and it acts as a tiny bar magnet

however this magnetic field keeps on

spinning since the atom is spinning

naturally the axis of the spinning

magnetic field is oriented randomly in

the human body

when this hydrogen atom comes into

contact with an external magnetic field

the orientation of the magnetic field of

the hydrogen atom changes and aligns

with the direction of the field

Additionally the rate of magnetic field

spin also changes

in this case the rate of the spin is

known as the resonance frequency and it

varies according to the strength of the

external magnetic field

this resonance frequency is quite

important in MRI and is determined using

the laramore equation

let's move on to the next step

so far we've aligned all the hydrogen

atoms in the direction of the magnetic

field

let's strike a radial pulse on a

hydrogen atom as a result the hydrogen

atom changes its orientation and flips

90 degrees with respect to the main

magnetic field

it's important to remember that the

frequency of an RF signal should be the

same frequency as the hydrogen atom's

resonance frequency

only then will the hydrogen atom flip

when we remove the RF pulses the atom

loses its energy and returns to its

normal orientation

the energy it emits is in the form of RF

pulses

however the time it takes each atom to

return to normal is different meaning

that the duration of emission of RF

signals is also different

the computer receives these signals and

converts them into images

since the unhealthy tissue has more

hydrogen atoms it generates different RF

signals

but how exactly can we generate a

detailed image the secret lies in phase

and frequency encoding with the help of

Furrier transformation

now that you know how an MRI machine

generates 2D images of a particular part

of the brain you may be wondering how

the machine is able to select the

specific part of the brain for Imaging

this work is done with the help of

gradient coils

the main electromagnet is constant and

the pair of gradient coils produce

opposite magnetic fields to each other

one coil increases the magnetic field

and the other side coil decreases the

magnetic field due to this gradient of

the magnetic field formed in between the

two coils

there are three sets of coils for the X

Y and Z directions let's see the

magnetic field produced by the x-axis

gradient coil with the help of FEA

results produced by em works

these results show us that variation in

the magnetic field gradually increases

from one coil to the other

gradient coils need to provide linear

gradations of the magnetic field as we

see in this FEA result

as a result the resonance and frequency

of hydrogen atoms will change from head

to toe gradually in order to image the

body region of Interest we must simply

use the specific radio frequency in RF

coils to excite just that part of

hydrogen atoms that provide a signal

as you might imagine the main component

of an MRI machine is the electromagnet

which provides a strong magnetic field

most magnets are of the superconducting

type ranging from 0.5 to 3 Tesla

the superconducting magnet is

continuously on from the time of

installation to the time of

decommissioning

the magnet is 100 times stronger than

small household magnets such as those

found on refrigerator doors or in

children's toys

another main component of an MRI scanner

is the RF coils

many coil designs exist but they all

fall into two main categories surface

coils and volume coils

as the name suggests a surface coil

rests on the surface of the object being

imaged Let's do an FEA simulation once

again of a Birdcage brain RF coil with

the help of em works

this result shows that there is more

magnetic flux density on the side

conductors and less on the end rings

in its simplest form it's a coil of wire

with a capacitor in parallel the

inductance of the coil and the

capacitance from a resident circuit are

tuned to have the same resonant

frequency as the part being imaged

thank you for watching we hope you

enjoyed this video please don't forget

to support lezix on patreon