Atrial fibrillation cardiac radioablation target visibility on magnetic resonance imaging

Figures

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  Fig. 1. Illustration of overall study method. CNR contrast-to-noise ratio, ROIs region of interest, SNR signal-to-noise ratio

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  Fig. 2. Exemplar illustration of the diameter size and location of ROIs used to quantitatively calculate image quality metrics. Background (pink), lung (red), left atria (yellow), right pulmonary vein region near the target (green), left pulmonary vein region near the target (blue) ROIs were used

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  Fig. 3. Exemplar images to illustrate the differing image quality and presence of artifacts between MRI acquisition categories and datasets. The best and worst scoring 3D acquisition MRI datasets (3Dacq) in terms of qualitative score and quantitative analysis are compared to 2D acquisitions. 2D balanced steady-state free-precision sequence (TrueFISP) and gradient echo fast low angle shot (FLASH) dataset comparisons are shown to illustrate the increased presence of artifacts with TrueFISP. Near real-time 2D acquisition without ECG-gating (2Dreal-time) datasets had lower signal-to-noise (SNR) and contrast-to-noise (CNR) compared to cardiac-gated datasets (2D TrueFISP & 2D FLASH) and this image quality reduction can be visually observed in these images. Images are for healthy participants rather than atrial fibrillation (AF) participants unless otherwise indicated. SNR and CNR were slightly lower in datasets acquired from AF participants compared to healthy participants. Artifacts detected included motion artifacts, flow artifacts, and signal voids. Arrows indicate the approximate target region

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  Fig. 4. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) between the evaluated ROI(s) and lung ROI, and non-uniformity image quality metrics for 3Dacquisition datasets. Results are given for the average of the left and right PV ROIs (a) and for the left atria (b)

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  Fig. 5. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) between the evaluated ROI(s) and lung ROI, and non-uniformity image quality metrics for 2DECG-gated datasets. Results are given for the average of the left and right PV ROIs (a) and for the left atria (b). The bars and error bars represent the average and standard deviation of the image quality metric throughout the cardiac cycle respectively

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  Fig. 6. Variation of average contrast-to-noise ratio (CNR) between the two PV ROIs and surrounding lung ROI a throughout the cardiac cycle for balanced steady-state free-precision sequence (TrueFISP) in blue and gradient echo fast low angle shot sequence (FLASH) in orange for participant Vol03 and b with time for an exemplar 2Dreal-time dataset. The larger variation in CNR in TrueFISP compared to FLASH observed in a and the periodic variation observed in b loosely corresponding to heart-rate were typical of what was observed in other participants