Performance Assessment of a Novel Endosphenoid Pituitary Microcoil for MRI
Introduction: The identification of the pituitary microadenoma causing Cushing’s disease remains elusive in up to 40% of patients. The inability to detect small tumors (< 3 mm) by MRI presumably arises from multiple factors, including low signal-to-noise ratio (SNR). SNR is related to magnet strength and the number of antenna coils, and inversely related to field of view (FOV) and distance from source to receiver coil. We designed and constructed a prototype MRI antenna microcoil assembly that situates the coil immediately adjacent (1 mm) from the pituitary gland.
Objective: We hypothesize that the higher SNR achievable in the area pituitary gland will allow ultra-high-resolution imaging, hopefully capable of detecting tumors as small as 1 mm.
Methods: A 2 cm diameter loop made from a single contiguous copper trace attached to a coax cable was constructed. A tuning electrical circuitry allowed active decoupling of the loop during the transmit portion of the pulse sequence. The built-in docking port relays the signal from the coil remote tune/match box to the preamp via a micro coaxial connector.
Results: We have tested the coil on isolated muscle tissue, demonstrated up to a 6-fold increase in SNR over the head coil. The local coil alone had sufficient SNR improvement for FOV coverage of over 1 - 1.5 cm in depth and width (large enough for pituitary gland). The coil was then tested in a cadaver, revealing similar SNR improvement.
Conclusions: This preliminary study demonstrates that the microcoil concept can result in an increase in SNR. Further studies and development are required.