Relative SNR Measurements in Supine vs. Prone Breast MRI

Supine breast MRI has the potential to improve patient comfort compared to prone breast MRI, in addition to providing images in the same position as subsequent treatment protocols. Novel flexible coil arrays have enabled high SNR and parallel imaging in supine breast imaging, but the combined effect of coil and patient positioning on SNR has yet to be investigated. The aim of this study is to use a tissue-independent metric to account for tissue deformation to compare SNR between prone and supine positions, using appropriate coils for each.

Relative SNR (rSNR) metric is proposed as the ratio of SNR between a breast coil and a body coil. This metric is demonstrated to be tissue-independent, allowing for easier SNR comparisons in cases of tissue deformation. We scanned 10 female subjects and compared the rSNR in segmented regions consisting of breast tissue, chest wall, and axilla between prone and supine breast imaging.

The rSNR was significantly higher in the breast tissue and chest wall in the supine position for all cases. The axilla rSNR was significantly higher in supine for four cases, with another four significantly higher in prone, and two showing no statistical difference. Using a distance-from-coil analysis, we found that the tissue is closer to the coil in supine, and that the supine coil provided higher SNR at distances closer than 4cm.

Our results show that using a surface array coil in the supine position can provide higher SNR than a standard setup in most subjects for most relevant regions of breast MRI.