Angiographic properties of Gd-DTPA-24-cascade-polymer — a new macromolecular MR contrast agent

Abstract

Purpose: A new macromolecular MR contrast agent, Gd-DTPA-24-cascade-polymer, was assessed for MR angiography of peritumoral vessels in rats. Material and methods: High resolution 3D-SPGR (TR/TE 100/5ms, α = 90°) angiograms were acquired in 10 Fischer rats bearing subcutaneous R3230 mammary adenocarcinomas. MRI was performed before, immediately and 40 min after administration of Gd-DTPA (0.1 mmol Gd/kg), and after either Gd-DTPA-cascade-polymer or albumin-(Gd-DTPA) 30 (each 0.05 mmol Gd/kg). A semi-quantitative analysis of small peritumoral vessels and tumor rim enhancement was performed on maximum intensity projection (MIP) angiograms using a 4-point scoring system. A quantitative analysis compared vascular signal-to-background-(S/B), signal-to-noise-, and contrast-to-noise-ratio. Results: Gd-DTPA produced a transient and low-scoring vessel definition (0.2 ± 0.1), but strong rim enhancement (score 1.7 ± 0.1). The cascade polymer resulted in better but submaximal vessel delineation (score 1.6 ± 0.3, S/B 5.0 ± 0.2) and strong rim enhancement (score 1.8 ± 0.1). Albumin-(Gd-DTPA) 30 produced the best and most time-persistent angiograms (score 2.6 ± 0.2, S/B 7.4 ± 0.2), but minimal rim enhancement (score 0.3 ± 0.2). Conclusion: The Gd-DTPA-24-cascade-polymer demonstrated the useful combination of strong tumor rim enhancement and detailed angiographic definition of peritumoral vessels. These are advantages associated with extracellular and blood pool contrast media, respectively.