Fast Field Cycling MRI Radiofrequency Coil
Completed for the Medical Physics and Bio-Engineering department of the University of Aberdeen's School of Medicine and Dentistry.
The Problem
The Problem
The team lacked a radiofrequency (RF) coil to accurately image five to ten centimeters into the human torso. Such a coil is required for in-vivo clinical studies that image changes to tissues brought about by disease.
The Design
Following discussions with my colleagues, as well as research into existing literature on the subject, my first task was to re-create a commonly used, basic surface coil. This design would address constraints in size and cost of the coil as well as the type of MRI that it would be used with.
The first design consisted of a ring of low-cost copper foil connected to recycled capacitors and an RF (M-type) connector. Using an oscilloscope it was observed that, as expected, the low cost materials resulted in a low Q-factor and signal to noise ratio (SNR).
To attain an acceptable image quality, the Q-factor and SNR had to be greatly improved. Higher quality materials were used and a new "butterfly" coil design was proposed. The "butterfly" coil would make use of the transverse region above the center coils to produce a homogeneous image in the region of interest above the central current carrying elements.
To further exploit this concept, new coils were proposed with an increased number of central elements. While increasing the elements would increase image clarity, the fields surrounding the central elements would interfere and decrease image clarity. Therefore, tests were conducted comparing two, four and six central element coils.
Following this process, the two and four element coils were identified as most effective. Further testing was recommended to investigate the relationship between central element separation distance and the number of elements used however, due to time constraints, I was not able to carry out these tests.
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