Spatial and temporal resolution effects on dynamic contrast-enhanced magnetic resonance mammography

We tested the hypothesis that partial volume effects due to poor in-plane resolution and/or low temporal resolution used in clinical dynamic contrast-enhanced magnetic resonance imaging results in erroneous diagnostic information based on inaccurate estimates of tumor contrast agent extravasation and tested whether reduced encoding techniques can correct for dynamic data volume averaging. Image spatial resolution was reduced from 469×469 μm2 to those reported below by selecting a subset of k-space data. We then compared the top five Ktrans/VT “hot spots” obtained from the original data set, 469×469-μm in-plane spatial resolution and an 18-s temporal resolution processed by fast Fourier transform (FFT), with values obtained from data sets having in-plane spatial resolutions of 938×938, 1875×1875 and 2500×2500 μm2 and a temporal resolution of 18 s, or data sets with temporal resolutions of 36, 54 and 72 and a spatial resolution of 469×469 μm2, and found them to statistically differ from the parent data sets. We then tested four different post processing methods for improving the spatial resolution without sacrificing temporal resolution: zero-filled FFT, keyhole, reduced-encoding imaging by generalized-series reconstruction (RIGR) and two-reference RIGR (TRIGR). The top five values of Ktrans/VT obtained from data sets, the in-plane spatial resolutions of which were improved to 469×469 μm2 by zero-filling FFT, Keyhole and RIGR, statistically differed from those obtained from the original 469×469 μm2 FFT parent image data set. Only the 938×938 and 1875×1875 μm2 data sets reconstructed to 469×469 μm2 with TRIGR reconstruction method yielded values of the top five Ktrans/VT hot spots statistically the same as the original parent data set, 469×469 μm2 in-plane spatial and 18-s temporal-resolution FFT. That is, partial volume effects from data sets of different in-plane spatial resolution resulted in statistically different values of the top five Ktrans/VT hot spots relative to a high spatial and temporal resolution data set, and TRIGR reconstruction of these low resolution data sets to high resolution images provided statistically similar values with a savings in temporal resolution of 2 to 4 times.