Faster sequences, better coils, better acquisition techniques ("spiral" instead of linear acquisition through K-space, better aliasing which allows for multislice simultaneous acquisition), better motion correction... Kawin Setsompop is the man when it comes to rapid MR acquisition.
https://www.nmr.mgh.harvard.edu/news/20150714/with-new-techniques-mri-faster-than-ever-before
CT is also improving by leaps and bounds. Dual energy CT and improved reconstruction algorithms have improved soft tissue contrast and decreased both radiation and contrast dose significantly. If you want to see some crazy recon algorithms, look up Synho Do's work.