Phase contrast magnetic resonance imaging for cerebral aqueduct resistance

• Transmantle pressure under the influence of free breathing: non-invasive quantification of the aqueduct pressure gradient in healthy adults
• Assessment of neurofluid dynamics in relation to clinical improvement after tap-test: pilot study
• Enhanced in vitro model of the CSF dynamics
• Mathematical Modelling of CSF Pulsatile Flow in Aqueduct Cerebri
• Magnetic Resonance Imaging of Normal Pressure Hydrocephalus
• Physical phantom of craniospinal hydrodynamics
• Potential surrogate markers of cerebral microvascular angiopathy in asymptomatic subjects at risk of stroke
• Abnormalities of CSF flow patterns in the cerebral aqueduct in treatment-resistant late-life depression: a potential biomarker of microvascular angiopathy

Phase Contrast Magnetic Resonance Imaging (PC-MRI) for Cerebral Aqueduct Resistance is a specialized application used to evaluate the cerebrospinal fluid (CSF) dynamics within the narrow channel of the cerebral aqueduct. This approach has significant clinical implications for diagnosing and managing conditions such as hydrocephalus, aqueductal stenosis, and normal pressure hydrocephalus (NPH).

Phase Contrast Magnetic Resonance Imaging (PC-MRI) is an invaluable tool in neurosurgery for evaluating cerebral aqueduct resistance, particularly in the context of cerebrospinal fluid (CSF) dynamics. It provides non-invasive, quantitative insights into conditions affecting CSF flow, aiding in diagnosis, treatment planning, and post-treatment assessment.

• PC-MRI can identify reduced or absent CSF flow through the cerebral aqueduct, a hallmark of aqueductal stenosis.
• Helps differentiate obstructive hydrocephalus (e.g., due to aqueductal stenosis) from communicating hydrocephalus or other causes of ventricular enlargement.

• Quantifies Aqueductal CSF Flow:
  • Measures velocity, flow rate, and pressure gradients across the aqueduct.
  • Determines the severity of obstruction and helps decide between treatment options like endoscopic third ventriculostomy (ETV) or ventriculoperitoneal shunting.
• Guides Surgical Approach:
  • Provides detailed visualization of CSF dynamics, crucial for complex cases.

• Evaluating Surgical Success:
  • After procedures like ETV, PC-MRI can confirm restored CSF flow through the bypassed pathway or aqueduct.
• Monitoring Shunt Function:
  • Detects changes in flow dynamics that may indicate shunt malfunction or over-drainage.

• PC-MRI aids in distinguishing:
  • Normal Pressure Hydrocephalus (NPH):
    • Demonstrates characteristic CSF flow patterns and increased stroke volume in the aqueduct.
  • Obstructive Hydrocephalus:
    • Shows significantly reduced or absent flow in the aqueduct.

• Provides data for investigating:
  • Pressure gradients and flow oscillations in CSF pathways.
  • Pathophysiology of conditions like Chiari malformation or syringomyelia.
• Enhances understanding of CSF dynamics in neurosurgical disorders.

• Non-Invasive:
  • No need for invasive pressure monitoring techniques.
• Quantitative and Reproducible:
  • Provides objective data on CSF flow, velocity, and resistance.
• Dynamic Imaging:
  • Captures pulsatile CSF flow synchronized with the cardiac cycle.
• Enhanced Surgical Decision-Making:
  • Helps tailor interventions based on precise flow dynamics.

• Artifact Susceptibility:
  • Sensitive to patient motion and magnetic field inhomogeneities.
• Specialized Expertise Required:
  • Requires trained personnel for image acquisition and interpretation.
• Temporal Resolution Constraints:
  • Limited ability to capture extremely rapid flow changes.

• Preoperative:
  • Patient undergoes PC-MRI to measure aqueductal CSF flow and resistance.
  • Results guide the decision to perform ETV or shunting.
• Postoperative:
  • PC-MRI assesses surgical outcomes, confirming restored CSF flow or detecting complications.

• Integration with AI-based analysis for automated detection of CSF flow abnormalities.
• Use of 4D flow MRI to provide more comprehensive insights into CSF dynamics in real time.

PC-MRI is a cornerstone in managing neurosurgical patients with disorders of CSF flow, improving diagnostic accuracy, guiding surgical decisions, and optimizing postoperative care.

No dedicated platform exists for quantifying ΔP, and no research has been conducted on the impact of breathing on ΔP. This study aims to develop a post-processing platform that balances accuracy and ease of use to quantify aqueduct resistance and, in combination with real-time phase contrast MRI, quantify ΔP driven by free breathing and cardiac activities.

Thirty-four healthy participants underwent 3D balanced fast field echo (BFFE) sequence and real-time phase contrast (RT-PC) imaging on a 3T scanner. We used the developed post-processing platform to analyze the BFFE images to quantify the aqueduct morphological parameters such as resistance. RT-PC data were then processed to quantify peak flow rates driven by cardiac and free breathing activity (Qc and Qb) in both directions. By multiplying this Q by resistance, ΔP driven by cardiac and breathing activity was obtained (ΔPc and ΔPb). The relationships between aqueduct resistance and flow rates and ΔP driven by cardiac and breathing activity were analyzed, including a sex difference analysis.

The aqueduct resistance was 78 ± 51 mPa·s/mm³. The peak-to-peak cardiac-driven ΔP (Sum of ΔPc+ and ΔPc-) was 24.2 ± 11.4 Pa, i.e., 0.18 ± 0.09 mmHg. The peak-to-peak breath-driven ΔP was 19 ± 14.4 Pa, i.e., 0.14 ± 0.11 mmHg. Males had a longer aqueduct than females (17.9 ± 3.1 mm vs. 15 ± 2.5 mm, p < 0.01) and a larger average diameter (2.0 ± 0.2 mm vs. 1.8 ± 0.3 mm, p = 0.024), but there was no gender difference in resistance values (p = 0.25). Aqueduct resistance was negatively correlated with stroke volume and the peak cardiac-driven flow (p < 0.05); however, there was no correlation between aqueduct resistance and breath-driven peak flow rate.

The highly automated post-processing software developed in this study effectively balances ease of use and accuracy for quantifying aqueduct resistance, providing technical support for future research on cerebral circulation physiology and exploring new clinical diagnostic methods. By integrating real-time phase contrast MRI, this study is the first to quantify the aqueduct pressure difference under the influence of free breathing. This provides an important physiological reference for further studies on the impact of breathing on transmantle pressure and cerebral circulation mechanisms ¹⁾

While the findings are promising, they are preliminary, and further studies with larger sample sizes, disease populations, and longer follow-up periods are needed to validate these results and explore their clinical implications. The lack of a detailed description of the software’s algorithms and technical specifications also limits the broader applicability of the approach, and future papers should provide more transparency in this area to ensure reproducibility and robustness. Nevertheless, this research opens the door to a better understanding CSF circulation and its potential role in neurodegenerative diseases.