High-resolution whole-brain dynamic contrast-enhanced MRI using compressed sensing

Dynamic contrast-enhanced (DCE) MRI is a powerful tool that maps the spatial distribution of vascular parameters in the brain, including blood-brain-barrier (BBB) permeability, interstitial transit times, and interstitial volume. DCE-MRI is widely used to assess BBB leakage in brain tumors and multiple sclerosis lesions, and it has potential applications in Alzheimer’s dementia, vascular cognitive impairment, migraine, epilepsy, and neuropsychiatric disorders such as depression. It involves intravenous administration of a paramagnetic contrast agent and continuous MRI acquisition of images to track the passage of the contrast through the volume of interest. Due to conventional Nyquist sampling requirements, most brain DCE-MRI scans have 5-second temporal resolution, 8-slice coverage, and relatively poor spatial resolution. Using MRI sparse sampling and constrained reconstruction techniques, we showed order of magnitude improvements in spatial resolution and coverage. Our recent work demonstrates the potential for improved clinical assessment of primary and metastatic brain tumors. Current clinical DCE-MRI protocols sacrifice spatial resolution and slice coverage to achieve the temporal resolution of 2–5s required to characterize contrast agent kinetics. A typical spatial coverage is 5cm, with spatial resolution 0:9 0:9 7:0mm3, and a temporal resolution of 5s. The restricted coverage and spatial resolution make it difficult to fully characterize large tumors or scattered metastatic lesions that may be present throughout the brain. MRI methods that involve sparse sampling and constrained reconstruction, including compressed sensing (CS— acquiring and reconstructing signals based on principles of sparsity), have emerged as a powerful tools to address this Figure 1. Spatial coverage of the experimental and conventional brain dynamic contrast-enhanced (DCE) MRI scans. The experimental scan provides high nearly isotropic spatial resolution over the entire brain, and allows for arbitrary reformatting. This patient had a large 6cm glioblastoma multiforme that was completely captured by the experimental scan.