A Magnetic Resonance Imaging (MRI) procedure uses radio waves and a strong magnet to align hydrogen protons in the body; when the magnets pull the protons from their normal position and on to a radiofrequency pulse, the protons release energy as they realign, which allows the computer to create very high detail tissue images by differentiating between the signals from various water molecules.
Tremendous Amount Of Magnetic Field Strength
The MRI uses superconducting magnets to generate incredible levels of strength of magnetic fields. Ideally, very strong magnetic fields will allow for the ‘alignment’ of protons (nuclei of hydrogen) inside the human body.
The Application Of Radio Frequencies
The application of the radio frequency waves is what actually ‘excites’ protons from their ‘aligned’ position and puts them into an ‘excited’ energy state.
The Emission Of Radio Frequency Signals
Once protons return to their ‘default’ position, they will emit radio frequency signals.
How An MRI Machine Creates Images
Inside the MRI machine, the MRI equipment sends out signals to your body, which your body receives and then the device detects through its receivers and uses this signal to create images of your body on the computer screen.
How To Determine The Relaxation Time Of Protons
After the signal has been sent and received, the MRI will determine how long the protons remain in alignment and then, how long it would take for them to return to their normal state (relaxation time). The two different times associated with the return to the original state are T1 (the time taken for the magnetics to return to the point of equilibrium) and T2 (the time taken for the axial rotation to return to a point of equilibrium).
Creating The Magnetic Field
Creating a magnetic field that is the right amount of strength and stability is the key to being able to carry out a successful MRI scan. MRI systems utilize superconducting magnets to generate very low resistance electrical fields and therefore produce a stable strong uniform magnetic field. These superconducting magnets are constructed from coils that have zero electrical resistance at very low temperatures (cryogenic) and this allows an electrical flow through them to have zero energy loss.
Cooling the coils to allow for superconductivity creates a magnetic field that is uniform in quality and produces high strength. The strength of the magnetic field generated by these types of superconducting magnets is the range from 1.5 to 3 Tesla, with the capability of the MRI machine dictating how strong it can produce the magnetic field.
Principles Of MRI And Radio Waves
The foundation of MRI is the relationship between magnetism and radio frequency waves. The magnetic aspect of the MRI process comes from the “spin” of certain atoms. For example, hydrogen (or protons), which are abundant in the body have the property of having “spin” hence, they produce very small amounts of magnetic fields around each hydrogen nucleus.
A superconducting magnet creates a very long-lasting magnetic field when the patient places him/herself into the scanner. A uniform and strong magnetic field polarizes the proton and creates what is called “alignment” of the hydrogen nuclei within the body. This process is vital for the entire MRI sequence.
Following the alignment of the hydrogen nuclei, RF (radio frequency) is applied to the patient. The RF energy causes the aligned hydrogen nuclei to absorb the RF energy and enter a “higher energy state.” When the RF energy is removed, the hydrogen nuclei return to their initial location and need to release the absorbed energy through RF signals.
What Is The Role Of Hydrogen Atoms And Their Alignment In MRI Scans?
Hydrogen is abundant in the human body, which comprises tissues & fluids therefore it is a great material to capture via MRI.
In MRI, hydrogen nuclei line themselves up with the natural magnetic field of the human body when the MRI equipment is activated.
As such, hydrogen nuclei all align in one direction while at rest, causing the same number of protons to align with the magnetic field as protons that do not align.
Hydrogen is the most common substance on Earth, and therefore there is a vast amount of it available in the human body.
Using an MRI to track hydrogen atoms in tissues provides the medical professional with large quantities of images of an organ’s or tissue’s overall health.
As a result, the position of the hydrogen nuclei relative to the magnetic field, referred to as the magnetic moment, has been developed and studied for over 30 years.
Development Of A Magnetic Field
The performance of an MRI scan depends greatly upon how well a highly concentrated and stable Magnetic Field Can Be Produced. Superconductor Magnets are the type of magnet used in MRI Scanners because they possess the ability to create a strong and consistently created magnetic field.
The various coils made of superconducting material are able to accomplish this because they have zero resistance to electrical flow when they are cooled to low enough temperatures by Cryogenic Systems.
This cooling process is essential because it ensures that when the coils are electrically conducting, there is no resistance and thus no loss of energy, resulting in a strong, steady magnetic field. The strength of the magnetic field produced by these magnets will depend on the type of scanner, typically ranging from 1.5 – 3 Tesla.
Along with the primary magnetic field, the MRI scans are also dependent on Gradient Coils. The Gradient Coils produce relatively weak magnetic fields along a single axis and can be controlled to create a linearly increasing or decreasing magnetic field along that axis.
Spatial encoding of the MRI data occurs through the adjustment and timing of Gradient Coils to produce multidimensional images from MRI data. The Gradient Coils also assist in determining the position and strength of the signals produced by the hydrogen nuclei during the scan.
Conclusion
MRI scans use a combination of special magnets, radio wave pulses, and a specific type of hydrogen atom known as a proton to create accurate pictures without hurting anyone inside their bodies. With stable magnetic field values ranging from 1.5–3 Tesla and using coils that can create very precise points in space and help calculate the time it takes for certain tissues to relax.
Frequently Asked Questions
Q. What Is The Science Behind MRI Scans?
Magnetic resonance imaging (MRI) works by aligning all of a person’s hydrogen protons using powerful magnetic forces and radio frequency fields before recording how much energy was expended when realigning these hydrogen protons into an orderly state.
Q. What Do MRI Scans Do To Your Body?
Using strong magnetic fields and radio frequency waves, MRI scans provide an image of your body’s interior. MRI scans assist physicians in diagnosing various medical issues regarding organs, soft tissues, the brain, spine, or joints, and they do this without exposing you to harmful radiation.
Q. What Are The Fundamental Physics Of Mr Imaging?
The principles of MRI physics are based on nuclear spin (hydrogen protons) aligning themselves with an external magnetic field and, due to their nuclear spins, precessing (rotating) about this field at a specified frequency called the Larmor frequency.
Q. What Happens Behind The Scenes Of An MRI Scan?
Through the use of large magnets, MRI technology utilizes strong magnetic fields to induce a temporary state of alignment within a patient’s body with regard to the protons found within water.
Q. Why Do I Feel Weird After An MRI?
After an MRI, you may feel ‘strange’ due to side effects of the contrast dye such as a warming sensation, a metallic taste, nausea and headaches; anxiety based on the loud noises and being in a tight space; or subtle effects of the magnetic fields on the fluid in the inner ear which may have caused dizziness or a feeling of being off balance.
