Dynamic quantitative nonenhanced magnetic resonance angiography of the abdominal aorta and lower extremities using cine fast interrupted steady-state in combination with arterial spin labeling: a feasibility study

Abstract

Background: Cine fast interrupted steady-state in combination with arterial spin labeling is a recently described nonenhanced magnetic resonance angiography (MRA) technique that relies on bolus tracking for time-resolved digital subtraction angiography-like displays of blood flow patterns. We evaluated the feasibility of applying this technique to display in-plane flow patterns in two regions: the abdominal aorta and lower extremity peripheral arteries.

Methods: We performed an institutional review board-approved study in healthy subjects and patients. In 7 healthy subjects, in-plane flow was imaged at 4 stations ranging from the lower legs to the aorto-iliac bifurcation (junction of the distal thigh and upper calf, mid-thigh, junction of the upper thigh and pelvis, upper pelvis). In 5 healthy subjects and 6 patients without abdominal aortopathy, images were acquired through the suprarenal abdominal aorta. Ten patients with known peripheral arterial disease and two patients with stable disease of the abdominal aorta were also evaluated. Peak velocity was compared at each of the 4 stations for cine fast interrupted steady-state in combination with arterial spin labeling and two-dimensional cine phase contrast in patients with normal vessels.

Results: In-plane flow patterns were well visualized in all peripheral arterial stations and in the abdominal aorta, providing a high quality display of hemodynamic patterns along extensive lengths of the vessels. There was very strong positive correlation (r = 0.952, P < 0.05) and excellent agreement (intraclass correlation coefficient, 0.935; 95% confidence interval, 0.812-0.972) between peak flow velocities measured by cine fast interrupted steady-state in combination with arterial spin labeling and two-dimensional cine phase contrast. In 10 patients with peripheral artery disease and 2 patients with aortic pathology, cine fast interrupted steady-state in combination with arterial spin labeling provided a visual demonstration of abnormal hemodynamics.

Conclusion: This feasibility study suggests that cine fast interrupted steady-state in combination with arterial spin labeling provides an efficient, high quality and physiologically accurate display of in-plane flow patterns over extensive lengths of the lower extremity peripheral arteries, which can be difficult to achieve using other MRA techniques.

Keywords: Angiography; Fast interrupted steady-state; Flow measurement; Magnetic resonance imaging; Peripheral artery disease; Quiescent interval slice-selective.

Fig. 1

a Bland-Altman diagram showing the plot of the difference between the flow velocity measured by cine fast interrupted steady state in combination with arterial spin labeling (cFASL) and 2D phase contrast (PC) at all stations in both cohorts against the mean velocity of the pair (n = 38). Red lines show the 95% limits of agreement, and the green line shows the mean value of the differences. b Bland-Altman diagram showing the plot of the difference between the flow velocity measured by cFASL and 2DPC at all stations in the lower extremity volunteers against the mean velocity of the pair (n = 27). Red lines show the 95% limits of agreement, and the green line shows the mean value of the differences. c Bland-Altman diagram showing the plot of the difference between the flow velocity measured by cFASL and 2DPC in the suprarenal aorta against the mean velocity of the pair (n = 11). Red lines show the 95% limits of agreement, and the green line shows the mean value of the differences

Fig. 2

a Linear relationship between overall peak flow velocity measurements in the lower extremities and suprarenal aorta using cFASL and 2DPC. b Linear relationship between lower extremity peak flow velocity measurements using cFASL and 2DPC. c Linear relationship between suprarenal aorta peak flow velocity measurements using cFASL and 2DPC

Fig. 3

54-year-old female healthy subject. a Scout coronal bSSFP image through the abdominal aorta. b Sagittal cFASL shows progression of the labeled bolus (arrows) through the upper abdominal aorta (8 of 32 frames shown, temporal resolution = 20 ms). The labeled bolus is plug-shaped as opposed to the parabolic shape seen with laminar flow in the smaller peripheral arteries

Fig. 4

55-year-old healthy male. a QISS MRA shows normal appearance of the peripheral arteries. b Coronal cFASL (maximum intensity projections across all slices, 6 of 22 frames shown) acquired through the upper pelvis, thigh-pelvis junction, mid-thigh and calf-thigh junction (top row to bottom row, respectively). Symmetrical progression of the labeled bolus (red arrows) through the legs is observed. A small amount of arterial signal can be observed in early frames (green arrowhead), which represents residual signal from tagging that occurred in a prior cardiac cycle. Retrograde flow in veins is observed above each tag (long blue arrow = inferior vena cava)

Fig. 5

58-year-old female who presented with disabling right leg pain. a computed tomography angiography (CTA) shows moderate stenosis at the bifurcation of the right common femoral artery, best shown in the magnified sagittal multi-planar reconstruction. b Sagittal cFASL (8 of 32 frames shown) shows the stenosis which appears comparable in severity to the CTA. c Coronal cFASL illustrates a slight delay in the progression of the labeled bolus in the right common iliac and superficial femoral arteries (most apparent in the first few frames) with respect to the contra-lateral arteries, consistent with a hemodynamically-significant lesion

Fig. 6

67-year-old male with history of left leg pain. CTA (a) and QISS MRA (b) show occlusion of the distal left superficial femoral artery (SFA) with distal reconstitution through collateral vessels. c Coronal cFASL shows normal, rapid progression of the labeled bolus through the right SFA, in contrast to the markedly delayed progression of the labeled bolus through the left-sided collaterals distal to the occlusion

Fig. 7

69-year-old male with right leg claudication secondary to occlusion of the proximal right superficial femoral artery. a CTA demonstrates heavily calcified atherosclerotic disease. b QISS MRA. Red arrow = incidental moderate stenosis of the left common iliac artery (CIA). c Axial slice from CTA (top) and QISS MRA (bottom) shows the left CIA stenosis. d Coronal cFASL shows a similar rate of progression of the labeled bolus on the two sides despite the presence of the left-sided stenosis (red arrows). This finding is suggestive that the stenosis is not hemodynamically significant. The left CIA plaque is visible as a partial filling defect in the labeled bolus of arterial blood. e Thin-slice (3-mm) axial cFASL at the level of the stenosis shows the arterial lumen (white) in high contrast to the plaque (dark). f Axial 2DPC at the level of the stenosis shows flow velocity (top) and bulk flow (bottom) for the right (red) and left (green) vessels. 2DPC confirms that the stenosis is not hemodynamically significant since bulk flow is approximately equal between the two sides during the systolic phase of the cardiac cycle, despite the increased peak flow velocity within the stenosis

Fig. 8

46-year-old male with a stable type B aortic dissection under surveillance. a Maximum intensity projection from QISS MRA shows the extension of the aortic dissection into the right common iliac artery. b Maximum intensity projection of five 9-mm thick slices using cFASL shows faster progression of the labeled bolus through the narrow, medially-located true lumen compared to the wider false lumen. c Single 27-mm slice using cFASL shows similar findings to (b) in one-fifth the scan time of the multi-slice cFASL acquisition