First-pass myocardial perfusion imaging and equilibrium signal changes using the intravascular contrast agent NC100150 injection

In this phase I clinical study, the new ultrasmall superparamagnetic iron o xide contrast agent, NC100150 Injection (Nycomed AS, Oslo, Norway, a part o f Nycomed Amersham), was assessed for first-pass magnetic resonance myocard ial perfusion studies and its ability to produce equilibrium signal changes , as a possible indicator of myocardial blood volume. Data were acquired in 18 healthy male volunteers at 0.5 T and 1.5 T,At both field strengths, fir st-pass studies using T1-weighted sequences were acquired. Long TE spin-ech o echoplanar imaging [EPI) was used at 0.5 T and short TE fast low-angle sh ot (FLASH) imaging at 1.5 T. With both sequences, T1 effects dominated the images for low doses. and time intensity curves potentially suitable for pe rfusion analysis were generated. At higher doses, T2 and T2* effects were o bserved. At 1.5 T, these predominantly affected the blood pool signal; howe ver, at 0.5 T the myocardial signal was also involved, reflecting the relat ive T2 and T2* sensitivity of the spin-echo EPI sequence as a result of the long TE and long readout window, respectively, Equilibrium changes were as sessed at both held strengths using T1-weighted FLASH sequences and in addi tion at 1.5 T using T2*-weighted gradient-echo EPI, With the T1-weighted im ages at both held strengths, signal changes were observed in all subjects; however no dose-response relationship could be shown. With the T2*-weighted EPI there was significantly lower signal (P < 0.05) with the 3 and 4 mg/kg doses than with the 2 mg/kg dose. In conclusion, NC100150 Injection is use ful for first-pass myocardial perfusion using T1-weighted sequences; howeve r. low doses in combination with short TE sequences are required to minimiz e sensitivity to T2* effects. Equilibrium signal changes can also be induce d in the myocardium, More work is required to optimize the imaging sequence s and dose of NC100150 Injection for first-pass studies and also to determi ne whether the equilibrium signal changes can be used to measure myocardial blood volume changes in ischemic heart disease, (C) 1999 Wiley-Liss, Inc.