Reproducibility and feasibility study for Phase Contrast MR Angiography at low tesla Open-MRI system

Phase Contrast MR Angiography (PC MRA) was used very powerful tools for diagnosis of blood vessel disease such as hemadostenosis, aneurism or flow velocity measurement. Many studies have been researched PC MRA application at high tesla MRI system because of main magnet field inhomogeneity and low signal to ratio (SNR) at low tesla MRI system. The purpose of this study is to develop the PC MRA pulse sequence for low tesla MRI system and assessed its clinical usefulness and reproducibility at low tesla system. We also evaluated the flow velocity using self-made phantom to accuracy of velocity measurement. The 0.32T MRI scanner (Magfinder II, AILab, Korea) was used in this study. For developed the pulse sequence, bipolar gradients are added to three orthogonal directions and flow compensation gradients were applied to slice selection direction and frequency encoding direction. Reference images were scanned without applied flow encoding gradients. Using flow encoded images and references images, magnitude and phase difference images were calculated. We also used zero-filling technique and Maximum Intensity Projection (MIP) for 3D PC MRA to improvement of image quality. Especially, using the self-made flow phantom, we measured the flow velocity and assessed its accuracy. Consider as based on our results, 2D/3D PC MRA images provide excellent visualization of vasculature of blood vessels and velocity information. Particularly, velocity measurement using phase images were nearly accuracy information about blood vessels velocity compared with doppler ultrasound. In conclusion, Using PC MRA technique displays both anatomic and flow information of blood vessels on images. Although, the image quality and SNR were lower than high tesla MRI system and the scan time was longer than high tesla MRI system, our result sufficient for explanation of flow direction and flow velocity changes in vivo studies during clinical application using at low tesla MRI system.