The use of real-time MRI techniques for imaging an extended field of view in magnetic resonance angiography

Accurate, fast, sensitive, and safe imaging of the cardiovascular system has major societal benefits owing to the high prevalence of cardiovascular disease. This is particularly challenging in imaging the peripheral vasculature, defined as extending from the renal artery origins to the ankles, because of the long (>120 cm) superior-inferior (S/I) field of view. Contrast-enhanced MR angiography provides major advantages compared to other imaging methods because it uses no ionizing radiation, provides 3D images, and requires only a relatively benign intravenous injection of contrast material. However, such imaging has major technical challenges in that the speed of passage of the contrast-enhanced blood through the vasculature is highly variable from patient to patient and the potentially rapid enhancement of veins can interfere with the radiological interpretation of disease in the companion arteries. The purpose of this work is to describe MRI physics and engineering methods designed to rapidly acquire high spatial resolution images of the peripheral vasculature at individual table positions or “stations,” and then to integrate these methods with real-time signal processing to allow interactive control of the MRI patient table, allowing it to advance in synchrony with the advancing contrast on a patient-specific basis. Results are presented with single station techniques to illustrate the potential image performance as well as in the more demanding and desired multi-station application in which the time available for data acquisition is limited at each station.