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Published on: May 31, 2024
Assessment of hypertensive cerebrovascular alterations with multiband Look-Locker arterial spin labeling
Yoojin Lee1, Tae Kim1,2
1Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
Insights
Hypertension slows brain perfusion dynamics, but cerebral blood flow remains unchanged. The multiband Look-Locker ASL technique reveals detailed cerebrovascular changes in hypertensive individuals.
Area of Science:
- Neuroimaging
- Vascular Biology
- Medical Physics
Background:
- Hypertension is a major risk factor for cerebrovascular diseases.
- Understanding hypertension-induced changes in cerebral hemodynamics is crucial for early diagnosis and treatment.
- Arterial Spin Labeling (ASL) is a non-invasive MRI technique for measuring cerebral blood flow (CBF).
Purpose of the Study:
- To quantitatively assess hypertension-induced cerebrovascular alterations using advanced ASL techniques.
- To evaluate the performance of multiband Look-Locker ASL (MB LL-ASL) for detailed hemodynamic parameter quantification.
- To compare cerebrovascular parameters between hypertensive and normotensive individuals.
Main Methods:
- The study utilized a multiband Look-Locker ASL (MB LL-ASL) technique at 3T.
- Vascular crushing gradients were optimized to differentiate arterial from tissue ASL signals.
- Simultaneous quantification of CBF, arterial transit time (tA), capillary transit time (tC), labeled blood delivery duration (τ), and arterial blood volume (CBVa) was performed with high temporal resolution (259 ms) and whole-brain coverage.
Main Results:
- Cerebral blood flow (CBF) was comparable between normotensive and hypertensive subjects (62.2 ± 6.87 vs. 61.9 ± 8.94 ml/100g/min).
- Hypertensive individuals exhibited prolonged capillary transit time (tC) and labeled blood delivery duration (τ) in most brain regions (tC: 1.30 ± 0.09 vs. 1.76 ± 0.16 sec; τ: 1.46 ± 0.10 vs. 2.30 ± 0.22 sec).
- Increased arterial blood volume (CBVa) was observed in the hippocampus and thalamus of hypertensive subjects compared to normotensives.
Conclusions:
- Hypertension significantly slows brain perfusion dynamics without altering overall CBF.
- The MB LL-ASL technique enables detailed characterization of regional cerebrovascular impairments.
- This advanced imaging approach enhances the understanding of hypertension-related cerebrovascular modifications.
Purpose:
To quantitatively assess the hypertension-induced cerebrovascular alterations by measuring the dynamics of arterial spin labeling (ASL) signals.
Materials And Methods:
The multiband Look-Locker ASL (MB LL-ASL) technique was evaluated in comparison to a single-band LL-ASL for three healthy subjects. Also, seven healthy subjects were scanned to determine the strength of the vascular crushing gradients applied to separate arterial from tissue ASL signal. With the optimized MB LL-ASL technique, multiple parameters, cerebral blood flow (CBF), transit times to artery (tA ), and capillary (tC ), delivery duration of labeled blood (τ), and arterial blood volume (CBVa ), were simultaneously quantified for age-matched eight control and eight hypertensive subjects with 259 msec of temporal resolution and 20 slices covering the whole-brain region at 3T.
Results:
While CBF of hypertensives were comparable with those of normotensives (CBF of normotensives vs. hypertensives = 62.2 ± 6.87 vs. 61.9 ± 8.94 ml/100g/min, P = 0.960 for the whole gray matter), tC and τ were prolonged in hypertensives in most brain regions (tC = 1.30 ± 0.09 vs. 1.76 ± 0.16 sec, P = 0.034; τ = 1.46 ± 0.10 vs. 2.30 ± 0.22 sec, P = 0.006 for the whole gray matter). Two regions showed the increased CBVa in hypertensives compared to normotensives (hippocampus and thalamus with P = 0.009 and 0.035, respectively).
Conclusion:
Hypertension slows the perfusion dynamics, while the remaining CBF is unchanged. A detailed characterization of regional cerebrovascular impairments by MB-LL-ASL technique provides better understanding of hypertension-induced cerebrovascular modifications.
Level Of Evidence:
1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:663-672.
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