ESTRO 2024 - Abstract Book

S3781

Physics - Image acquisition and processing

ESTRO 2024

Results:

The RF transmission loss in the mux was measured to be 4 dB at 64 MHz. Figure 1f shows a comparison of the reconstructed images with and without multiplexing. The coil sensitivity profiles were preserved, indicating a reliable channel separation. The signal-to-noise ratio (SNR) took a factor 9 penalty as quantified in figure 2a-b. A demonstration of the mux modulation in k-space before and after separation is shown in figure 2c-d, respectively. Finally, in figure 2e we show an uncropped image after separation and reconstruction. Image replicas appeared around the mux repetition frequency in the readout direction. The origin of these was found in the square-wave modulation by the mux, which introduces Fourier components at multiples of the repetition rate. Additionally, sharp transient bands appeared from switch events. Both effects determined the effective readout bandwidth to equal the mux repetition rate; therefore cropping the reconstructed image accordingly rendered them irrelevant. We expect further SNR improvements by (1) synchronizing the mux phase to the MRI sequence (Fig. 2d) and by (2) expanding the separation algorithm to account for bandwidth reductions performed internally by the system’s digitizer. Note that the SNR penalty cannot be mitigated fully, since the sample rate is reduced by decimation. This