During the past decade our group has developed highly accelerated MR angiographic techniques based on undersampled radial acquisition, constrained reconstruction, and phase contrast imaging. Three basic modes of functional MRA (fMRA) will be implemented using 3D radial acquisition (VIPR). These are: 1. Contrast-enhanced (CE) time-resolved angiography with highly constrained reconstruction (HYPR) 2. Undersampled phase contrast imaging 3. HYPR processed CE-MRA using the phase contrast data for the composite image (HYPR FLOW) See Figure 1 in specific aims for an overview of the three modes. The first mode typically provides acceleration factors of 20 to 200 relative to non-accelerated, Nyquist- satisfying Cartesian acquisition with noise factors an order of magnitude less than for parallel imaging. The phase contrast mode provides a method for non-CE angiography with excellent isotropic spatial resolution. This information permits the measurement of flow and pressure gradients in small vessels, adding a new dimension to non-invasive angiography. In the third mode, which also provides flow derived information, undersampling factors of up to 1000 relative to the Nyquist requirements have been achieved, providing voxel volumes an order of magnitude smaller than competing techniques, with temporal resolution of about 0.75 seconds. We propose to optimize these acquisition and reconstruction methods and to begin preliminary investigations of the feasibility of new applications such as relative wall shear stress measurement and pressure gradients. We will use simulations, phantom studies, volunteers and patients to determine the range of spatial and temporal resolution required for various applications and the sampling and SNR requirements for accurate determination of flow-derived quantities. We will obtain pilot studies in patients with altered flow conditions related to intracranial arterial stenosis, aneurysm and arteriovenous malformations. The data will be processed to provide a temporal series, displays of velocity, volume flow, relative wall shear stress and pressure gradients.
Functional Magnetic Resonance Angiography (fMRA) is a method to visualize the vascular structures of the brain. The technique has benefits over current methods in that it covers the entire brain and provides temporal information, high spatial resolution and flow dynamics. It is of minimal risk compared to conventional catheter based angiography and is thus better suited for the evaluation of atherosclerotic disease in elderly patients. It is a major advance in the evaluation of patients with atherosclerotic disease, brain aneurysms and vascular malformations, which are the leading causes of stoke in the US.
|Schubert, Tilman; Wu, Yijing; Johnson, Kevin M et al. (2016) Time-of-Arrival Parametric Maps and Virtual Bolus Images Derived From Contrast-Enhanced Time-Resolved Radial Magnetic Resonance Angiography Improve the Display of Brain Arteriovenous Malformation Vascular Anatomy. Invest Radiol 51:706-713|
|Bauman, Grzegorz; Johnson, Kevin M; Bell, Laura C et al. (2015) Three-dimensional pulmonary perfusion MRI with radial ultrashort echo time and spatial-temporal constrained reconstruction. Magn Reson Med 73:555-64|
|Prabhakaran, Vivek; Nair, Veena A; Austin, Benjamin P et al. (2012) Current status and future perspectives of magnetic resonance high-field imaging: a summary. Neuroimaging Clin N Am 22:373-97, xii|
|Kecskemeti, Steven; Johnson, Kevin; Wu, Yijing et al. (2012) High resolution three-dimensional cine phase contrast MRI of small intracranial aneurysms using a stack of stars k-space trajectory. J Magn Reson Imaging 35:518-27|
|Chang, W; Loecher, M W; Wu, Y et al. (2012) Hemodynamic changes in patients with arteriovenous malformations assessed using high-resolution 3D radial phase-contrast MR angiography. AJNR Am J Neuroradiol 33:1565-72|
|Chang, W; Frydrychowicz, A; Kecskemeti, S et al. (2011) The effect of spatial resolution on wall shear stress measurements acquired using radial phase contrast magnetic resonance angiography in the middle cerebral arteries of healthy volunteers. Preliminary results. Neuroradiol J 24:115-20|
|Chang, W; Landgraf, B; Johnson, K M et al. (2011) Velocity measurements in the middle cerebral arteries of healthy volunteers using 3D radial phase-contrast HYPRFlow: comparison with transcranial Doppler sonography and 2D phase-contrast MR imaging. AJNR Am J Neuroradiol 32:54-9|
|Frydrychowicz, Alex; FranÃ§ois, Christopher J; Turski, Patrick A (2011) Four-dimensional phase contrast magnetic resonance angiography: potential clinical applications. Eur J Radiol 80:24-35|
|Wu, Y; Chang, W; Johnson, K M et al. (2011) Fast whole-brain 4D contrast-enhanced MR angiography with velocity encoding using undersampled radial acquisition and highly constrained projection reconstruction: image-quality assessment in volunteer subjects. AJNR Am J Neuroradiol 32:E47-50|
|Wu, Yijing; Kecskemeti, Steven R; Johnson, Kevin et al. (2011) HYPR TOF: time-resolved contrast-enhanced intracranial MR angiography using time-of-flight as the spatial constraint. J Magn Reson Imaging 33:719-23|
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