Spatial and temporal resolution effects on dynamic contrast-enhanced magnetic resonance mammography Michael Aref a , Josh D. Handbury b , Jim Xiuquan Ji c , Susanne Aref d , Erik C. Wiener e, 4 a Department of Nuclear, Plasma, and Radiological Engineering, Beckman Institute Biomedical Imaging Center, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA b The Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL 60064, USA c Department of Electrical Engineering, Texas A & M University, College Station, TX 77843, USA d Aref Consulting Group LLC, Deland, IL 61839, USA e University of Pittsburgh Cancer Institute, Hillman Cancer Center, Pittsburgh, PA 15213, USA Received 19 April 2006; accepted 5 September 2006 Abstract 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 lm 2 to those reported below by selecting a subset of k-space data. We then compared the top five K trans /V T bhot spotsQ obtained from the original data set, 469469-lm 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 lm 2 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 lm 2 , 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 K trans /V T obtained from data sets, the in-plane spatial resolutions of which were improved to 469469 lm 2 by zero-filling FFT, Keyhole and RIGR, statistically differed from those obtained from the original 469469 lm 2 FFT parent image data set. Only the 938938 and 18751875 lm 2 data sets reconstructed to 469469 lm 2 with TRIGR reconstruction method yielded values of the top five K trans /V T hot spots statistically the same as the original parent data set, 469469 lm 2 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 K trans /V T 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. D 2007 Elsevier Inc. All rights reserved. Keywords: Dynamic contrast enhanced; Magnetic resonance imaging; Magnetic resonance mammography; Breast carcinoma; Permeability; Contrast agent transfer 1. Introduction One in vitro histopathological technique for determining the prognosis of a cancer patient relies on differences in capillary density resulting from heterogeneous vascular endothelial growth factor (VEGF)-induced angiogenesis. The prognostic information is obtained at specific micro- scopic fields or magnifications [1–3]. Weidner et al. [2,3] determined that the lowest magnification required for optimally determining prognosis based on capillary density was a microscopic field of view (FOV) of 0.740 mm 2 (860-lm diameter). The greatest magnification at which capillary densities significantly determined prognosis was a microscopic FOVof 0.152 mm 2 (390-lm diameter). Any area between these two limits provided useful prognostic infor- mation, whereas any FOV greater than or less than those defined above lost or obscured the prognostic information. According to Folkman [4–6], acquisition of the angio- genic phenotype is a necessary condition for metastasis and a prognostic marker for malignant breast tumors. One of the means by which a cancer cell acquires the angiogenic phenotype is through the expression of VEGF. This protein 0730-725X/$ – see front matter D 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.mri.2006.09.025 4 Corresponding author. Tel.: +1 412 623 4658; fax: 412 623 3355. E-mail address: wienere@upmc.edu (E.C. Wiener). Magnetic Resonance Imaging 25 (2007) 14 – 34