Thank you for joining us as we explore magnetic resonance imaging. This article details what an MRI is and how an it works. Gain a thorough understanding of this diagnostic imaging procedure, so you know what to expect during your diagnostic procedure. At Medicalimagingsource.com our primary mission is to improve the imaging experience for patients.
What Is MRI?
Magnetic resonance imaging, commonly referred to as MRI, is a pain-free, non-invasive diagnostic imaging technique. MRI utilizes a superconductive magnet, radio frequency pulses, and high performance reconstruction computers to produce clear images of the anatomy. MRI scans offer greater detail when imaging soft tissue or non-bony anatomical structures when compared to X-ray, Ultrasound and CT.
How Does An MRI Scan Work?
An MRI scanner produces high definition images of the anatomy by placing patients inside a large superconductive magnet. Hydrogen molecules in the tissue align with the poles of the magnetic field.
Radio Frequency pulses (RF) and secondary magnetic fields interact with the molecules during the excitation phase of the scan sequence. This causes the molecules to flip upon their axis. The hydrogen molecules flip back into alignment between pulses, (this is known as the relaxation phase). Receivers in the scanner then detect the movement of the hydrogen molecules as they flip upon their axis.
In many cases, specialized MRI coils may be fitted to the patient anatomy. These coils act as a localized antenna to maximize the scan signal detected by the magnetic resonance imaging scanner. At this point, the MRI scan receivers collect the scan data and sends it to a high-performance reconstruction computer for processing into 3D renderings.
MRI Scanner Components
The main components of a MRI scanner are:
1. Magnet
Generates a strong magnetic field used to align the hydrogen nuclei in the patient’s body.
2. Cryogenic Cooling Systems
Maintains the superconducting state of the magnet by cooling it to extremely low temperatures.
3. Gradient Coil
Produces varying magnetic fields to spatially encode information for imaging.
4. RF Coil
Emits radiofrequency pulses and receives signals from the patient to create images.
5. MRI Coils
Specialized coils used to enhance signal detection and image quality in specific regions of the body.
6. Patient Table
Platform on which the patient lies for scanning. It allows for precise positioning within the magnetic field.
7. Operator Console
Interface (GUI) for controlling the MRI scanner, adjusting parameters, and acquiring images. MRI technologists workspace
8. PDU (Power Distribution Unit)
Distributes power to different components of the MRI scanner system.
9. Gradient Amplifiers
Amplifies electrical signals to drive the gradient coils for spatial encoding.
10. RF Amplifier
Amplifies radiofrequency signals for transmission to the RF coil.
11. RF Receiver Assembly
Receives and processes radiofrequency signals emitted by the patient during imaging.
12. Image Reconstruction Computer
Processes raw data acquired during the scan to reconstruct detailed images.
13. Peripheral Devices
Additional equipment such as patient monitors and input devices used for operation and data management.
14. MRI Safety Systems
Implements safety protocols and features to ensure the well-being of patients and operators during scanning.
15. RF Shielding
Prevents external radiofrequency interference and contains the RF signals within the scanning environment.
Find additional information on our MRI scanner components explained article.
What is an MRI scan used to diagnose?
MRI proves to be a valuable full body medical imaging tool. Magnetic resonance imaging excels when imaging soft tissue, tendons, ligaments and other non-bony structures.
Researchers are actively finding new imaging applications and optimizing old scan techniques for best image quality possible. MRI scans help detect, diagnose and monitor conditions in every region of the human anatomy.
Brain MRI Scan Clinical Applications
Optimized brain imaging techniques detect conditions such as stroke, swelling, developmental abnormalities, infections, vascular disease and cancer. Tailored RF techniques produce high definition images of anatomical microstructures to aid in the detection of vascular disease.
Diffusion weighted imaging (DWI-MRI) and diffusion tensor imaging (DTI) allows rapid diagnosis for stroke and trauma victims.
Cardiac MRI Clinical Applications
Cardiac MRI scans are the gold standard with unsurpassed image clarity when assessing myocardial viability. Magnetic resonance imaging allows doctors to evaluate the individual chambers, blood vessels and valves of the heart. FMRI cardiac scans allow doctors to get a live view of blood flow as it circulates throughout the heart.
Check our video resources page for more information regarding clinical use.
Magnetic Resonance Imaging (MRI) Safety
Important Notes
-The MRI scan room contains a strong magnetic environment.
-Metal items should never enter the scan room. Patients with pacemakers, neurostimulators, or metal implants should consult with imaging staff before entering the scan room.
-Hearing protection is required during scan procedure.
Related: MRI Safety Zones Explained
How loud is an MRI scan?
MRI scanners produce images by emitting loud high frequency noises. The sounds emitted during the scan procedure can reach levels as high as 120 db. That is as loud as sitting in the front row of a rock concert. The sounds can cause injury or damage to hearing after prolonged exposure. Before the scan starts, hearing protection will be provided to the patient.
What Does an MRI Scan Sound Like?
Listen in to our most popular MRI scan sound video here on our YouTube Page. The unique sounds are part of what allow doctors to take a look inside the body without ever having to make an incision. Click here if you would like to learn more about why MRI sounds are so loud.
Closed MRI vs Open MRI
Closed MRI scanners are the most common magnet type in clinical use. They feature a cylindrical design with a full magnet enclosure. This design offers higher magnet strengths between 1 Tesla and 7 Tesla. Magnet bore width of a closed system is limited to 70 cm. Closed MRI maximum patient weight is limited to 350lbs.
Meanwhile, open MRI systems feature a double pillar design that maximizes patient access and visibility. This specialized imaging system offers magnet strengths up to 0.8 Tesla. Open MRI is open on 3 to 4 sides and offers patients greater visibility when inside the magnet enclosure. Click here for more information about open MRI vs closed MRI.
MRI Scan Procedure
This section provides an overview of the diagnostic scan experience. Know what to expect before, during and after a magnetic resonance imaging exam.
How long does an MRI scan take?
MRI scans average between 25 and 35 minutes to complete each examination. Some exams may require a contrast agent to be administered to enhance features within the anatomy. This process may add up to 15 minutes to the total scan time. Patients can expect to arrive 30 minutes before scheduled imaging procedure for check-in and screening processes. Total time spent at imaging facility is between 1 and 2 hours.
Scan Preparation
After patients have checked in, the screening processes begins. The screening process ensures patients are safe to enter the scan room and are free of metal items.
Patients with pacemakers, neurostimulators, or metal implants should consult with imaging staff before entering the scan room. Once the patient is cleared to enter, they are lead into the scan room.
Patients are asked to lay in a position that is best suited for imaging the anatomical region of interest. The technologist may place pads, straps, or blankets around the patient during scan preparation to aid in patient comfort.
Patients are encouraged to remain as still as possible during the scan sequences to produce the best image quality. Once the patient is ready to begin, the table will slide into the scanner until the anatomical region of interest is aligned with the magnet isocenter.
The technologist will step into the operator room once the patient is prepared to begin the scan sequence. Operator rooms sit adjacent to the scan room. RF-shielded viewing windows ensure the technologist can always keep visual line of sight with the patient. The technologist can communicate with patients at any time via a two way speaker.
What If You Need To Stop The Scan?
Patients will be given an emergency squeeze bulb to hold during the examination.
If at any point there is a need to stop the scan, the patient can squeeze an emergency bulb that will immediately alert the technologist to pause the scan.
Recommended Article: Top 20 Tips To Stay Calm During Your Next MRI Scans
What is getting an MRI like?
The technologist will start the scan remotely from the operator room. At this point, the magnet produces powerful primary and secondary magnetic currents. This is a non-invasive process and will not cause any harm or pain to the patient.
High frequency RF pulses are emitted from the scanner to interact with the molecules within the tissue. This is also a non-invasive process and will not cause any harm or pain to the patient.
The RF pulses cause the molecules to flip from a lower energy state to a high energy state. Detectors in the scanner sense the movement of the molecules and use the signal to create 3d renditions of the anatomy.
During the scan, patients are asked to remain as still as possible so the images will be clear. Some scan sequences may require the patient to hold their breath. The technologist will prompt the patient if a breath hold scan sequence is the next scan sequence
Does MRI Use Radiation?
Unlike CT scans, MRI scanners do not emit ionizing radiation. This makes magnetic resonance imaging scans the preferred imaging option for patients that require multiple scans over time while monitoring known conditions.
What are the Side Effects of MRI Scan?
MRI scans provide safe, pain-free and non-invasive diagnostic imaging exams. There are no known side effects to an MRI scan, so patients may resume normal activities after the examination. Drink plenty of water over the next 24 hours to help flush any contrast agents.
The incidence rate of adverse reaction to contrast agents is less than 1 percent. Mild symptoms may include nausea, headache, or dizziness for a brief time after contrast has been administered. Adverse reactions to contrast agents typically occur within the first hour after administration.
For more information regarding possible adverse reactions to contrast agents: https://www.acr.org/-/media/ACR/files/clinical-resources/contrast_media.pdf
Scan Results Wait Time
Upon the completion of the diagnostic procedure, images are sent to a radiologist for reading and diagnosis. Results are then forwarded to general practitioner to plan future treatment, if any. Patients typically receive results within 24 – 48 hours. Check with your imaging facility for an accurate estimate of results.
Conclusion
Magnetic resonance imaging is a modern marvel in medical science that offers a pain-free, non invasive diagnostic exam with no know long term effects. MRI scans offer unbeaten clarity when imaging soft tissue, ligaments, tendons and other non-bony structures. Vascular techniques allow for HD imaging of anatomical microstructures. This makes MRI the best imaging choice for many brain and cardiac imaging techniques. The clinical applications of magnetic resonance imaging are growing with every passing day. The advent of new imaging techniques will find new applications for magnetic resonance imaging.
Notes From The Author
Related Resources
- Radiology Blog
- Learning Hub
- What’s The Difference Between MRI and CT Scans?
- Guide To Breast MRI
- MRIPETCTSOURCE YouTube Channel
- What Are The Different GE MRI Scanner Models?
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