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A Quick and Inexpensive QA Test Phantom and Procedure for Large Volume Phased Array Receiver Coils

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A Curcuru

A Curcuru*, B McClain , S Mutic , O Green , H Gach , Washington University School of Medicine, St. Louis, MO


MO-RPM-GePD-IT-5 (Monday, July 31, 2017) 3:45 PM - 4:15 PM Room: Imaging ePoster Theater

Purpose: To create an efficient and inexpensive method to diagnose and troubleshoot the integrity of individual coil elements in large volume (body) phased array coils for MRI systems.

Methods: A large homebuilt phantom was built to test the individual phased array coil elements. Sixteen 2.4” diameter holes, forming a 4x4 grid, were cut into a 24’’x24’’x5’’ polyurethane foam block (Grainger). A plastic bottle filled with water doped with nickel(II) chloride was inserted into each hole. The phantom was placed on the patient table with the coil under test (CUT) placed on top. Ten saline bags were placed on top of the CUT to load the coils and ensure signal was available for prescan calibrations. Scans were acquired in 7 slices using a gradient echo pulse sequence [TE/TR: 3/147 ms, 60° flip angle, 480 mm field of view, and 300Hz/pixel]. MRIs were acquired on a 1.5T scanner (Philips Ingenia) and a 0.35 T MR-IGRT system (ViewRay). Individual MRIs were reconstructed for each coil element. The image signal integral, standard deviation, and mean were calculated for the central slice of each coil image and for an automatically segmented region of interest around the highest signal region of interest (bottle) using an in-house MATLAB (MathWorks, Natick, Massachusetts) program.

Results: A faulty coil element was determined qualitatively by observing significant noise in the coil image. Baseline quantitative benchmarks are being acquired to assess appropriate pass/fail criteria. The torso coils were recently replaced on the 0.35 T MR-IGRT system, necessitating further baseline measurements to develop a coil performance specification.

Conclusion: Individual coil elements can be checked quickly and easily using the phased-array QA phantom constructed from inexpensive materials. While the resulting images clearly show when a coil element has failed, additional data is needed before assessing longitudinal changes in coil health.

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