Hållningsspoles

Hållningsspoles, often translated as "posture coils" or "body coils," are specialized electromagnetic coils used in magnetic resonance imaging (MRI) to receive the radiofrequency signals emitted by the body's tissues. Unlike the main magnet and gradient coils responsible for generating the magnetic field and spatial encoding, holdningsspoles are dedicated to detecting the subtle signals that form the MR image. They are placed directly around or on the body part being imaged to maximize signal-to-noise ratio.

There are different types of holdningsspoles, categorized by their design and application. Surface coils are placed directly on the skin and are excellent for imaging superficial structures due to their high spatial resolution. Volume coils, such as head coils or knee coils, encompass the entire body part, providing a larger field of view and good signal uniformity, though often with lower resolution compared to surface coils. Phased-array coils, a combination of multiple surface coils, offer a balance between coverage and resolution by electronically combining signals from individual elements.

The design of a holdningsspole is critical for optimal image quality. Factors like coil geometry, number of elements, and matching networks are carefully engineered to resonate at the Larmor frequency of the hydrogen nuclei being excited by the MRI scanner. The effectiveness of a holdningsspole directly impacts the signal-to-noise ratio (SNR) of the acquired MR images, which in turn affects the diagnostic confidence and detail visible in the final image. Newer advancements include adaptive or dynamic coils that can adjust their sensitivity profile to further improve SNR and reduce artifacts.