Large coverage black‐bright blood interleaved imaging sequence (LaBBI) for 3D dynamic contrast‐enhanced MRI of vessel wall

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Vessel wall inflammation plays an important role in the development of vascular diseases such as atherosclerosis and aneurysms 1. In several studies, vessel wall inflammation has been shown to be associated with clinical vascular events 3. Thus, it is important to image vessel wall inflammation in vivo. Dynamic contrast‐enhanced MRI (DCE‐MRI) is a useful tool to analyze inflammation in carotid atherosclerosis noninvasively 5 by using pharmacokinetic modeling.
However, using DCE‐MRI to evaluate inflammation in the vessel wall is technically challenging, especially in early lesions. There are two competing requirements in DCE data acquisition 11: high temporal resolution bright‐blood imaging for arterial input function (AIF) acquisition and high spatial resolution black‐blood imaging for vessel wall depiction. Currently, most studies have made compromises by acquiring only bright‐blood images 6 for advanced plaques. The bright‐blood technique can estimate the AIF directly, but the temporal resolution (∼15 s) is compromised by the high spatial resolution required for vessel wall imaging and is usually insufficient to extract AIF accurately. More importantly, thin vessel walls with early lesions cannot be quantified reliably due to signal contamination from the luminal signal. Black‐blood DCE techniques have also been proposed for vessel wall imaging 9 that allow accurate thin vessel wall imaging by suppressing blood signal. However, AIF cannot be extracted directly from the black‐blood images and may introduce bias in the pharmacokinetic analysis using the reference region method or population AIF 9.
Recently, several techniques enabling interleaved black‐bright blood imaging have been introduced 15, which can acquire bright‐blood images for AIF and black‐blood images for vessel wall in a single scan. However, these techniques are based on a double inversion recovery 18 or quadruple inversion recovery 19 prepulse for black‐blood imaging. Thus, they are limited to 2D vessel wall imaging and with limited longitudinal coverage. Mendes et al. 20 proposed an interleaved 2D/3D bright‐blood imaging sequence to perform 3D vessel wall DCE‐MRI. However, the vessel wall imaging in this sequence may still suffer from luminal signal contamination, since no black‐blood prepulse was used.
In this study, we propose a large coverage black‐bright blood interleaved imaging sequence (LaBBI) for vessel wall DCE‐MRI. In this sequence, the 3D large coverage high spatial resolution black‐blood vessel wall images and 2D high temporal resolution bright‐blood images can be acquired in an interleaved fashion within a single scan. In LaBBI, the spatial and temporal resolution of the two acquisitions can be adjusted flexibly to satisfy the requirements of pharmacokinetic analysis on different targets. Simulations, phantom studies, and in vivo experiments were performed to test the feasibility of the proposed LaBBI method.

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