MO‐G‐18C‐06: MRI QC: Effects of Multi‐Channel Coil Element Failure On Image Quality

Abstract

Purpose:To quantitatively evaluate changes in phantom quality control (QC) measurements resulting from malfunctioning channels in multichannel brain coils during routine MRI QC.Methods:The large ACR MRI phantom was scanned on a 1.5T GE HDXt scanner using an 8‐channel brain array and on a 1.5T Siemens Aera using a 20‐channel head‐neck array. For the 8‐channel array, images were acquired by sequentially turning off an increasing number of adjacent channels. For the 20‐channel array, images were acquired with various combinations of active coil elements. Percent integral uniformity (PIU), signal‐to‐noise ratio (SNR) and ghosting ratio were measured with and without uniformity correction (UC).Results:For the 8‐channel array, SNR and PIU decreased with the number of inactive coil elements (57% and 34%, respectively). UC increased PIU to >82% and SNR to 80%, but also increased apparent ghosting due to background nonuniformity. For the 20‐channel array, the central pair of element groups (H3‐H4) closest to the phantom had the greatest impact on image quality. Without UC, PIU and SNR were similar when all groups or both H3‐H4 were active. Without UC, PIU decreased by 50% when either H3 or H4 was deactivated. Noise greatly decreased resulting in a ∼500% increase in SNR. Without UC, SNR decreased by 60% and PIU increased when both H3‐H4 were deactivated. PIU was most affected by UC (50%–160% increase). For both coils, ghosting ratio generally increased with UC but not above ACR limit (2.5%). With UC applied, PIU failed the ACR limit (87.5%) when 2 elements of the 8‐channel array or H3‐H4 were inactive.Conclusion:Channel failure for the two multichannel arrays tested was reflected in changes in SNR and PIU. For daily MR QC, setting coil‐specific SNR, PIU and ghosting QC limits to ensure the detection of malfunctioning elements is necessary due to coil design variations.