Abstract
PurposeTo implement and characterize a fluorine-19 (19F) magnetic resonance imaging (MRI) technique and to test the hypothesis that the 19F MRI signal in steady state after intravenous injection of a perfluoro-15-crown-5 ether (PCE) emulsion may be exploited for angiography in a pre-clinical in vivo animal study.Materials and Methods In vitro at 9.4T, the detection limit of the PCE emulsion at a scan time of 10 min/slice was determined, after which the T1 and T2 of PCE in venous blood were measured. Permission from the local animal use committee was obtained for all animal experiments. 12 µl/g of PCE emulsion was intravenously injected in 11 mice. Gradient echo 1H and 19F images were obtained at identical anatomical levels. Signal-to-noise (SNR) and contrast-to-noise (CNR) ratios were determined for 33 vessels in both the 19F and 1H images, which was followed by vessel tracking to determine the vessel conspicuity for both modalities.Results In vitro, the detection limit was ∼400 µM, while the 19F T1 and T2 were 1350±40 and 25±2 ms. The 19F MR angiograms selectively visualized the vasculature (and the liver parenchyma over time) while precisely coregistering with the 1H images. Due to the lower SNR of 19F compared to 1H (17±8 vs. 83±49, p<0.001), the 19F CNR was also lower at 15±8 vs. 52±35 (p<0.001). Vessel tracking demonstrated a significantly higher vessel sharpness in the 19F images (66±11 vs. 56±12, p = 0.002).Conclusion 19F magnetic resonance angiography of intravenously administered perfluorocarbon emulsions is feasible for a selective and exclusive visualization of the vasculature in vivo.
Highlights
A considerable research effort is directed at improving the detection of vascular disease with different modalities such as Xray, intravascular ultrasound (IVUS), computed tomography (CT) and magnetic resonance angiography (MRA) [1]
The in vitro 19F perfluoro-15-crown-5 ether (PCE) T1 relaxation time was very similar in saline and blood (1400630 and 1350640 ms (Fig. 1a)), while the T2 was significantly reduced in venous blood from 440625 to 2562 ms (Fig. 1b)
The PCE appeared to be welldistributed throughout the vasculature immediately after injection and 19F imaging was successful until 5 hours after injection
Summary
A considerable research effort is directed at improving the detection of vascular disease with different modalities such as Xray, intravascular ultrasound (IVUS), computed tomography (CT) and magnetic resonance angiography (MRA) [1]. Because of its non-invasive nature and lack of harmful radiation, MRA is considered the most patient-friendly among these techniques, while soft-tissue characteristics and blood flow can be exploited for contrast generation. The main challenge for MRA is associated with the fact that signal originates from water protons, which are abundant in the entire body. This leads to background signal in the image and the blood-pool cannot be seen exclusively. This means that some strategy is needed to attenuate the signal from static tissue in close proximity to the blood vessels. Contemporary MRA is commonly performed using intravascular [2] or extracellular [3] T1-lowering gadolinium (Gd) contrast agents, time-of-flight (TOF) imaging, or phase contrast (PC) imaging
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