Improved phase-contrast flow quantification by three-dimensional vessel localization

Regional Cerebral Blood Flow Using Quantitative MR Angiography

“…The protocol that uses a retrospectively gated fast 2D phase-contrast sequence has been described previously. 1,18,19 The protocol entails performing a standard axial 2D and 3D timeof-flight (TOF) MR angiography (MRA) of the cervical and cranial vasculature, similar to conventional neck and head MRA. The acquired TOF images were then transmitted to a workstation where rotating 3D surface-rendered vascular images (Figs 1 and 2) were reconstructed using a marching-cube algorithm.…”

“…The acquired TOF images were then transmitted to a workstation where rotating 3D surface-rendered vascular images (Figs 1 and 2) were reconstructed using a marching-cube algorithm. 18 Optimal perpendicular scan plane determination was based on the scan line calculated by a line-fitting algorithm introduced by Zhao et al 18 The coordinates obtained specify the position of an oblique fast 2D phasecontrast sequence, which was then performed based on these coordinates, using a retrospectively gated 2D phase-contrast sequence with the following imaging parameters: TR, 10 -15 ms; TE, 4 -7 ms; flip angle, 15; number of excitations, 4; section thickness, 5 mm for neck vessels and 3 mm for intracranial vessels; FOV, 180 mm for neck vessels and 140 mm for intracranial vessels; and matrix, 256 ϫ 128 for neck vessels and 256 ϫ 192 for intracranial vessels. Velocity encoding was automatically adjusted with the NOVA software if necessary.…”

In Vivo Evaluation of Quantitative MR Angiography in a Canine Carotid Artery Stenosis Model

“…The greatest accuracy in PCMR flow measurements is achieved when the imaging plane is perpendicular to the vessel of interest and the VENC is matched to the throughplane flow. 16 The QMRA software has automated the placement of a perpendicular imaging plane and the selection of the appropriate VENC based on the actual flow in the vessel under study. To date, this technique has been used to guide patient management in cerebral revascularization surgery [17][18][19][20] ; assess intracranial and extracranial vessel stenosis pre-and poststent placement 21 ; measure blood flow in cerebral aneurysms 22 ; evaluate subclavian steal syndrome 23 ; assess collateral volume flow in large-vessel cerebrovascular disease 24 ; and predict outcomes of balloon-occlusion testing.…”

“…To date, this technique has been used to guide patient management in cerebral revascularization surgery [17][18][19][20] ; assess intracranial and extracranial vessel stenosis pre-and poststent placement 21 ; measure blood flow in cerebral aneurysms 22 ; evaluate subclavian steal syndrome 23 ; assess collateral volume flow in large-vessel cerebrovascular disease 24 ; and predict outcomes of balloon-occlusion testing. 20 Although in vitro validation of QMRA has been performed by using flow phantoms, 16 in vivo evaluation of clinically relevant cerebrovascular flows, in conjunction with progressive arterial stenosis, has not been previously described. In this study, we compared the accuracy of QMRA with the criterion standard for direct flow measurement, the sonographic transit-time flow probe, by using an in vivo canine carotid artery model in which flow rates and degree of stenosis were changed systematically.…”

Effect of flip angle on volume flow measurement with nontriggered phase‐contrast MR: In vivo evaluation in carotid and basilar arteries

“…The effect of these differences is difficult to evaluate. For example, misalignment of imaging slices of phase-contrast MRI results in positive errors in vitro, but negative errors in vivo (3).…”