Dynamic Spin Labeling Angiography in Extracranial Carotid Artery Stenosis
Carsten Warmutha,
Maria Rüpinga,
Annette Förschlerc,
Hans-Christian Koennecked,
Jose Manuel Valduezab,
Andreas Kauertd,
Stephan J. Schreiberb,
Ralf Siekmanne and
Claus Zimmerc
a Department of Radiology, Charité-Universitary Medicine Berlin, Berlin
b Department of Neurology, Charité-Universitary Medicine Berlin, Berlin
c Department of Neuroradiology, University Hospital Leipzig, Berlin
d Department of Neurology, Ev. Krankenhaus Königin Elisabeth Herzberge, Berlin
e Department of Neuroradiology, Giessen Medical School, Justus-Liebig-Universität Giessen, Germany
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FIG 1. DSLA sequence scheme. After the section selective/nonselective labeling pulse, multiphase data acquisition started in a cine-like fashion. Any segmentable gradient-echo readout may be used. Figure depicts FLASH readout with threefold segmentation and flow compensation in the section and read directions. ADC indicates analog-to-digital converter; RF, radio frequency; S, section direction gradient.
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FIG 2. Determination of ATDs. Left, Original signal intensity-time courses measured in the left and right MCAs. Right, Normalized curves (divided by the respective maximum value). By using linear interpolation between the measured points, the intersection at which the signals reached 50% was determined. Difference was referred to as the ATD (arrows).
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FIG 3. Patient 30, with an 85% stenosis of the left ICA. Dynamic angiograms of the circle of Willis in foot-to-head projections at 60, 100, 140, 220, 300, and 580 ms after labeling in a-f. In a, the right ICA (upper arrow) and basilar artery (lower arrow) fill first. In b, Collateral flow into the left MCA via the left posterior communicating artery and the anterior communicating artery is shown. In d, Left ICA fills. In f, because of the finite length of the labeled bolus, all vessels but the left ICA and MCA contain unlabeled blood at this late phase.
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FIG 4. ATDs calculated for the CS (left) and MCA (right) increase significantly with the degree of stenosis (P < .01). Values at 60% and 75% stenosis are those of individual patients.
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FIG 5. ROC curves for ATDs in the CS. Left, Distinction of control subjects and patients with 30–60% stenosis. Right, Distinction of control subjects and patients with <70% stenoses from those with 70–95% stenosis. ATD of >150 ms proved a high-grade stenosis (specificity, 100%; sensitivity, 56%).
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FIG 6. Scatterplot of the ATDs calculated for the MCA versus those for the CS. Patients were subdivided by the degree of collateral flow visible on DSLA. Degree of collateralization was determined by subjectively assessing flow in the anterior and posterior communicating arteries. Patients with pronounced collateral flow are in the group in whom MCA ATD was less than CS ATD.
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FIG 7. In a, DSLA difference images of the circle of Willis in patient 40, with a 95% stenosis before and after endarterectomy. In b, Signal intensity-time courses in the CS. After intervention, arrival time on the affected side was the same as on that the unaffected side (about 125 ms). Amplitudes were not calibrated; hence, higher signal intensity was not associated with higher blood flow or blood volume in a vessel.
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