Alterations of cerebral perfusion in asymptomatic internal carotid artery steno-occlusive disease

Figure 1. Labeling layout. Labeling was planned by referring to a time-of-flight image where internal carotid arteries and vertebral arteries were most identifiable and most perpendicular to the labeling plane. Labeling efficiency (α) was approximately a sinusoidal function of location within a spatial period of encoding (denoted by Lx in the left-right direction and Ly in the anterior-posterior direction, respectively). In this study, 4 steps were played out as shown by sinusoidal curves (1 step in the anterior-posterior direction and 3 harmonic steps in the left-right direction).

Figure 2. MR images obtained from a 65-year-old female patient with asymptomatic ICA steno-occlusive disease (10–30% stenosis in the left ICA and no stenosis in the right ICA). (A) Time-of-flight angiography. Projection view from below. (B) From top to bottom rows (3 slices are shown in radiological convention): FLAIR images, CBF maps (in units of ml-blood/100 ml-tissue/min), ATT maps (in units of sec), and flow territory maps. Flow territory maps show the membership levels generated by fuzzy clustering, which range from 0 to 1.

Figure 3. MR images obtained from a 60-year-old female patient with asymptomatic ICA steno-occlusive disease (occlusion in the right ICA and 30–50% stenosis in the left ICA). (A) Time-of-flight angiography. Projection view from below. (B) From top to bottom rows (3 slices are shown in radiological convention): FLAIR images, CBF maps (in units of ml-blood/100 ml-tissue/min), ATT maps (in units of sec), and flow territory maps. Flow territory maps show the membership levels generated by fuzzy clustering, which range from 0 to 1. No contribution from right ICA was extractable. In FLAIR images, there are two small foci of white matter hyperintensity in right frontal white matter which might represent chronic ischemic white matter lesions.

Figure 4. MR images obtained from a 57-year-old male patient with asymptomatic ICA steno-occlusive disease (>95% stenosis in the right ICA and 10–30% stenosis in the left ICA). (A) Time-of-flight angiography. Projection view from below. (B) From top to bottom rows (3 slices are shown in radiological convention): FLAIR images, CBF maps (in units of ml-blood/100 ml-tissue/min), ATT maps (in units of sec), and flow territory maps. Flow territory maps show the membership levels generated by fuzzy clustering, which range from 0 to 1. No contribution from right ICA was extractable. In FLAIR images, there are bilateral confluent periventricular white matter hyperintensities which are larger on the right side.

Figure 5. Representative CBF maps (in units of ml-blood/100 ml-tissue/min) derived from multi-PLD data for (A) the rightmost slice in Fig. 2 and (B) the leftmost slice in Fig. 3. Arrows indicate isolated hyperintensities. The open arrow indicates regional hypointensity as compared to single-PLD-derived value.