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Updated: May 5, 2026
Magnetic Resonance Imaging Quantification of Pulmonary Perfusion using Calibrated Arterial Spin Labeling
Published on: May 30, 2011
Optimization of pseudo-continuous arterial spin labeling for brain perfusion imaging in the intraoperative setting
Carmen Sánchez-Albardíaz1, Marta Calvo-Imirizaldu1, Verónica Aramendía-Vidaurreta1
1Department of Radiology, Clínica Universidad de Navarra, Pamplona, Spain.
Purpose:
Pseudo-continuous arterial spin labeling (PCASL) efficiency during intraoperative MRI is degraded due to large field inhomogeneities observed in some patients and lower arterial blood velocities induced by anesthesia. The purpose of this work was to maximize labeling efficiency during intraoperative MRI by optimizing PCASL parameters at 3 T.
Methods:
Effects of PCASL labeling pulse interval and gradient parameters on labeling efficiency were first investigated by numerical simulations based on Bloch equations. PCASL parameters were modified accordingly, considering hardware constraints, and evaluated experimentally. An experiment in healthy volunteers compared three labeling pulse intervals. In intraoperative brain tumor patients, different configurations were tested in two experiments: different labeling pulse intervals in patient experiment 1, and different labeling pulse interval and gradient average ( ) in experiment 2.
Results:
Numerical simulations showed that shortening the labeling pulse interval improved robustness of PCASL to off-resonance effects and that raising the increased labeling efficiency for lower blood velocity profiles. In healthy volunteers for large off-resonance, perfusion signal obtained with the labeling pulse interval of 600 μs was significantly higher than the one obtained with 1000 μs and 1400 μs (p-value < 0.001). In patients, a short labeling pulse interval of 600 μs and of 0.9 mT/m improved the quality of perfusion maps and significantly increased quantified cerebral blood flow values (p-value = 0.0078).
Conclusion:
Shortening the labeling pulse interval and increasing the gradient average improves PCASL efficiency in the intraoperative setting.
Insights
Optimizing pseudo-continuous arterial spin labeling (PCASL) parameters, specifically shortening the labeling pulse interval and increasing gradient average, enhances intraoperative MRI perfusion imaging. This improves robustness to field inhomogeneities and increases cerebral blood flow quantification.
Area of Science:
- Neuroimaging
- Medical Physics
- Radiology
Background:
- Pseudo-continuous arterial spin labeling (PCASL) efficiency is often reduced during intraoperative MRI due to magnetic field inhomogeneities and reduced arterial blood flow.
- Anesthesia-induced hypotension can further compromise PCASL performance in patients undergoing neurosurgery.
- Optimizing PCASL parameters is crucial for reliable intraoperative perfusion assessment.
Purpose of the Study:
- To maximize PCASL labeling efficiency in the challenging intraoperative MRI environment at 3 Tesla.
- To investigate the impact of labeling pulse interval and gradient parameters on PCASL performance.
- To optimize PCASL for improved perfusion imaging in brain tumor patients during surgery.
Main Methods:
- Numerical simulations using Bloch equations were performed to assess the effects of labeling pulse interval and gradient parameters.
- PCASL parameters were adjusted based on simulations and hardware limitations, then evaluated experimentally in healthy volunteers and brain tumor patients.
- Experiments involved varying labeling pulse intervals and gradient averages (G_ave) in different intraoperative patient studies.
Main Results:
- Simulations indicated that shorter labeling pulse intervals enhance PCASL robustness to off-resonance effects.
- Increased G_ave improved labeling efficiency, particularly for lower arterial blood velocities.
- In patients, a 600 μs labeling pulse interval and 0.9 mT/m G_ave significantly improved perfusion map quality and quantified cerebral blood flow (p=0.0078).
Conclusions:
- Shortening the labeling pulse interval is key to improving PCASL robustness in intraoperative MRI.
- Increasing the gradient average enhances PCASL efficiency, especially at lower blood flow rates.
- Optimized PCASL parameters significantly improve intraoperative perfusion imaging and quantification.
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