Carotid‐CNS MR flow imaging

Abstract

The authors present their 1-year experience with the use of 3DFT, time-of-flight MR angiography for the evaluation of vascular diseases of the head and neck. Their experience with over 150 patients indicates that this examination may be performed in conjunction with standard spin-echo imaging with only a minimal increase in patient examination time. This combined examination is most applicable to atherosclerotic disease of the carotid bifurcation, arterial occlusions of the primary and secondary branches of the intracranial circulation (particularly in pediatric patients such as those following ECMO or with sickle cell anemia), and patients with saccular berry aneurysms. This type of static, angiographic technique adds little to standard spin-echo imaging in patients with arteriovenous fistulae, neoplasms, and giant intracranial aneurysms. Limitations of the present technique include the inability to visualize slow flow lesions (e.g., giant aneurysms) and selected high flow states (arteriovenous fistulae, some severe stenoses).

Non‐contrast enhanced MR angiography: Physical principles

“…The oldest class of NCE-MRA techniques relies on the inflow effect of blood, also known as time-of-flight (TOF) (25,26). The inflow effect is the result of the difference in exposure to radiofrequency (RF) excitation of spins in stationary tissue versus spins in inflowing blood.…”

“…Inflow-based techniques are commonly paired with a flow-compensated readout to reduce signal loss from flow-induced spin dephasing (25,26). These flowcompensated gradient waveforms use extra gradient lobes to null gradient moments for both stationary spins and flowing spins moving through the gradient field.…”

Non-contrast-enhanced four-dimensional (4D) intracranial MR angiography: A feasibility study

“…In addition, the recent reported evidence that nephrogenic systemic fibrosis is associated with the administration of gadolinium-based contrast agents (9) in patients with impaired renal function increases the need for noncontrast methods in some patients. These limitations from using contrast agent have been one of the major motivations for the continuous development of angiographic techniques using a very low dose of contrast medium (10) or even completely eliminating contrast medium administration.Initial development of non-contrast-enhanced MRA started in the late 1980s, and substantial progress has been made in the past 2 decades (11)(12)(13)(14)(15)(16)(17). To date, the most widely used non-contrast-enhanced techniques are time-of-flight (TOF) (12,13) and phase-contrast (PC) MRA methods.…”

“…Initial development of non-contrast-enhanced MRA started in the late 1980s, and substantial progress has been made in the past 2 decades (11)(12)(13)(14)(15)(16)(17). To date, the most widely used non-contrast-enhanced techniques are time-of-flight (TOF) (12,13) and phase-contrast (PC) MRA methods.…”

“…To date, the most widely used non-contrast-enhanced techniques are time-of-flight (TOF) (12,13) and phase-contrast (PC) MRA methods. Despite successful utilization of TOF and PC in certain dedicated clinical applications, data acquisition using either one of these two techniques is fairly lengthy.…”