Trading off SNR and Resolution in MR Images

With a fixed time to acquire a magnetic resonance (MR) image, time can be spent to acquire better spatial resolution with decrease in signal-to-noise ratio (SNR) or decreased resolution with increase in SNR. This resolution/SNR tradeoff at fixed time has been investigated by a visual rater study using images of ex vivo mouse brains. Simulated images with a tradeoff between SNR and resolution were produced from high-quality, 3D isotropic mouse brain images to emulate shorter constant acquisition times. The tradeoff images spanned a range of SNRs (63-6) and isotropic resolutions (32-81 microm). Fourteen readers identified the image which best displayed neuroanatomy. Additional experiments tested for (i) intra-observer consistency, (ii) the effect of emulated scan time, and (iii) specifically biased questions pertaining to the perception of neuroanatomy. Optimal anatomical viewing depended primarily on the SNR of the images. Specifically, for fixed imaging time, preference lay in the SNR range of approximately 30-35 with strong consistency and there was minimal effect from overall imaging time.