Assessment of a rapid clearance blood pool MR contrast medium (P792) for assays of microvascular characteristics in experimental breast tumors with correlations to histopathology

The diagnostic potential of a new rapid clearance blood pool contrast mediu m (P792; MW = 6.47 kDa) for the MR assessment of microvessel characteristic s was assessed in 42 chemically-induced breast tumors, with comparisons to albumin-(Gd-DTPA). Microvessel characteristics, including the transendothel ial permeability (K-PS) and the fractional brood volume (fPV), were estimat ed by using dynamic MR data fit to a bidirectional two-compartment model. T he MR-derived estimates for K-PS and fPV using each contrast agent were com pared, and assays using each contrast agent were correlated to the histolog ic tumor grade (SBR score) and the microvascular density (MVD) counts. Usin g P792-enhanced data, neither K-PS nor fPV showed a statistically significa nt correlation with the tumor grade or the MVD (P > .05). Conversely, using albumin-(GdDTPA)(30), KPS values correlated significantly with the histolo gic tumor grade (r = .55; P < .0005) and the MVD (r = .34, P < .05), wherea s no correlation was established for fPV, In conclusion, based on P792 data no correlation between tumor microvascular characteristics and histologic markers (SBR score or MVD) was found in this breast tumor model. Our analys is suggests that contrast media of relatively large (on the order of 90 kDa ) molecular sire, such as albumin-(GdDTPA)(30), are more accurate for the c haracterization of tumor microvessels. (C) 2001 Wiley-Liss, Inc.