What are the different coils used in MRI?
Magnetic Resonance Imaging (MRI) forms the very foundation of modern diagnostic medicine by offering unparalleled views of the human body. At the very core of the functioning of an MRI system are the coils. Coils of an MRI system form an essential component in both the generation and reception of radiofrequency or RF signals, which give detailed imaging of the body.
Understanding the types of MRI coils, their functions, and their applications is quite indispensable for any radiologist, technician, or biomedical engineer. Further sections outline in detail the different kinds of coils used in the MRI system, their distinctive features, and their role in imaging.
Introduction to MRI Coils
MRI coils are special devices designed to either transmit or receive radiofrequency signals or both. In principle, they constitute antennae interacting with magnetic fields in the process of MRI. In any case, the quality and specificity of the images obtained largely depend on the type and configuration of the coil used. Of course, each type is developed for certain uses but with advantages in the imaging of certain body parts.
Types of MRI Coils
- Surface Coils
Surface coils are perhaps the most common type of MRI coils. Small and specialized, these coils are placed on or near the region of interest (Patient Body). They are designed to provide the maximum SNR in a local region.
Their applications include small-area treatments of the wrist, knee, or shoulder.
- Advantages
High spatial resolution.
Very well-suited for the detailed imaging of body parts.
- Limitations:
Narrow and poor field of view.
Requires precision positioning.
- Volume Coils
Volume coils are larger, cylindrical coils that can encompass the whole body or part of it. These can be used as both a transmission and a reception coil.
Applications: Very commonly used for imaging of the head, chest, or pelvis.
- Benefits
Uniform signal reception.
Appropriate for large anatomic regions.
Figures Birdcage coils (commonly used for head imaging).
- Phased Array Coils
Phased array coils consist of a number of small surface coils set together. These coils work together to improve the SNR and the FOV.
Applications: General; used to image spine, abdomen, or joints.
- Benefits:
Improved SNR compared to a single surface coil.
Larger area of coverage without losing resolution.
- Gradient Coils
Gradient coils play an important role in spatial encoding. These are not RF coils; however, they have an important role in image generation owing to changes in the magnetic field, particularly in particular directions.
- Applications: Spatial encoding is a feature common to all MRI.
These coils enable slice selection and spatial localization.
They play an important role in modern imaging techniques, including Diffusion-Weighted Imaging (DWI).
- Transmit-Receive Coils
Transmit-Receive Coils undertake the dual responsibility of emitting radio-frequency signals and receiving signals produced by the body tissues. These also involve high-field imaging and special examination.
- Advantages:
High precision in the transmission and reception of signals.
Used quite a lot in research.
- Specialty Coils
Various specialty coils have been designed for specific clinical applications and anatomic regions.
Examples:
- Cardiac Coils Optimized for heart imagery.
- Breast Coils: Designed for breast MRI.
- Extremity Coils: It deals with hands, feet, and other extremities.
Selection of MRI Coils: Things to Consider
The choice of the correct MRI coil depends on various factors:
Anatomical Region:
Size and type of coil should be matched with the region of interest.
Signal-to-Noise Ratio:
Good quality in images gives high SNR.
Field of View (FOV):
The first factor is the size of the area to be imaged.
Field Strength Compatibility:
Ensure that the coil is compatible with the MRI system’s magnetic field strength (e.g., 1.5T, 3T).
Maintenance and Durability:
Assess the coil life and ease of maintenance.
Emerging Trends in MRI Coils
Ongoing development within the MRI technological field refers to improvement in the areas of image quality and patient comfort:
Lightweight coils: Designed ergonomically to minimize patient discomfort.
Wireless Coils: These coils eliminate cables, reduce artifacts, and work comfortably in every exam.
AI-Enhanced Coils: These coils integrate artificial intelligence for automatic optimization of signal acquisition.
3D-printed coils: These coils can be designed individually for each patient.
Maintenance and Troubleshooting
Proper maintenance will help the MRI coil retain its good imaging performance.
- Routine cleaning prevents re-contamination and ensures patient safety.
- Routine Testing: Signals degraded or damaged are indicated.
- Repairs: Immediately repair any broken connections or faulty, or damaged cables.
- Storage: Store coils in a controlled environment to avoid physical damage.
Practical Applications and Use Cases
MRI coils are used in various applications, both clinically and in research:
Neuroimaging: high-resolution head and spine coils to diagnose neurologically relevant conditions.
Musculoskeletal Imaging: Surface and phased array coils for joint and soft tissue imaging.
Cardiovascular Imaging: Special coils for dynamic imaging of the heart.
Oncology: Follow-up with breast coils and body coils to detect tumors.
Conclusion
In this article, we tried to explain this question: “What are the different coils used in MRI?”. We explain that the MRI coils remain behind the scenes in diagnostic imaging and provide the only way of achieving true accuracy and clarity for diagnostics. From surface and volume to phased array and specialty coils, each has a particular purpose that fits into an anatomical region or imaging need. Understanding their role and advantages, and applying them, accordingly, allows for optimum utilization of MRI in the better delivery of patient care. It could be the technician trying to optimize imaging workflows or the hospital administration in search of economically viable solutions; investing in the right MRI coil will be crucial to enhancing the diagnostic capability.
Technomed Medical Parts and Equipment
Technomed Medical Parts and Equipment sells, repairs, and consults on MRI coils. Whether this is during the selection process, where advice and guidance are beneficial, through effective repairs, or finding an extensive array of refurbished OEM-compatible coils, Technomed will be happy to serve. Educated and well-experienced, one’s imaging systems operate with maximum effectiveness while assuring timely and cost-effective solutions without sacrificing diagnostic accuracy. You can contact us for more info.
