Abstract
BackgroundTo show that 3D sequences with ultra-short echo times (UTEs) can generate a positive contrast whatever the magnetic field (4.7, 7 or 9.4 T) and whatever Ultra Small Particles of Iron Oxide (USPIO) concentration injected and to use it for 3D time-resolved imaging of the murine cardiovascular system with high spatial and temporal resolutions.MethodsThree different concentrations (50, 200 and 500 μmol Fe/kg) of USPIO were injected in mice and static images of the middle part of the animals were acquired at 4.7, 7 and 9.4 T pre and post-contrast with UTE (TE/TR = 0.05/4.5 ms) sequences. Signal-to-Noise Ratio (SNR) and Contrast-to-Noise Ratio (CNR) of blood and static tissus were evaluated before and after contrast agent injection. 3D-cine images (TE/TR = 0.05/3.5 ms, scan time < 12 min) at 156 μm isotropic resolution of the mouse cardiopulmonary system were acquired prospectively with the UTE sequence for the three magnetic fields and with an USPIO dose of 200 μmol Fe/kg. SNR, CNR and signal homogeneity of blood were measured. High spatial (104 μm) or temporal (3.5 ms) resolution 3D-cine imaging (scan time < 35 min) isotropic resolution were also performed at 7 T with a new sequence encoding scheme.ResultsUTE imaging generated positive contrast and higher SNR and CNR whatever the magnetic field and the USPIO concentration used compared to pre-contrast images. Time-resolved 3D acquisition enables high blood SNR (66.6 ± 4.5 at 7 T) and CNR (33.2 ± 4.2 at 7 T) without flow or motion artefact. Coronary arteries and aortic valve were visible on images acquired at 104 μm resolution.ConclusionsWe have demonstrated that by combining the injection of iron nanoparticles with 3D-cine UTE sequences, it was possible to generate a strong positive contrast between blood and surrounding tissues. These properties were exploited to produce images of the cardiovascular system in small animals at high magnetic fields with a high spatial and temporal resolution. This approach might be useful to measure the functional cardiac parameters or to assess anatomical modifications to the blood vessels in cardio-vascular disease models.Electronic supplementary materialThe online version of this article (doi:10.1186/s12968-015-0167-4) contains supplementary material, which is available to authorized users.
Highlights
To show that 3D sequences with ultra-short echo times (UTEs) can generate a positive contrast whatever the magnetic field (4.7, 7 or 9.4 T) and whatever Ultra Small Particles of Iron Oxide (USPIO) concentration injected and to use it for 3D time-resolved imaging of the murine cardiovascular system with high spatial and temporal resolutions
The use of this type of contrast agent has two major disadvantages: 1) intra-venous injection entails a risk for the patient to develop nephrogenic systemic fibrosis [4]; 2) first pass extraction and rapid redistribution into the extracellular space limits the time-window of imaging enhanced vasculature [5]
The aim of this study was to show that 3D imaging with ultra-short echo times (TE < 0.050 ms) can generate a positive contrast for blood other a wide range of magnetic fields (4.7, 7 or 9.4 T) and USPIO concentrations injected
Summary
To show that 3D sequences with ultra-short echo times (UTEs) can generate a positive contrast whatever the magnetic field (4.7, 7 or 9.4 T) and whatever Ultra Small Particles of Iron Oxide (USPIO) concentration injected and to use it for 3D time-resolved imaging of the murine cardiovascular system with high spatial and temporal resolutions. The use of this type of contrast agent has two major disadvantages: 1) intra-venous injection entails a risk for the patient to develop nephrogenic systemic fibrosis [4]; 2) first pass extraction and rapid redistribution into the extracellular space limits the time-window of imaging enhanced vasculature [5]. Some gadolinium-based contrast agents have been developed and validated in preclinical models [6]. Ferumoxytol was used at 3 T for contrast-enhanced high resolution imaging of the cardio-vascular system [12, 13]
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