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Aneurysm wall thickness measurements of experimental aneurysms: in vivo high-field MR imaging versus direct
Camillo Sherif1, Günther Kleinpeter, Michel Loyoddin
1Department of Neurosurgery, Krankenanstalt Rudolfstiftung, Juchgasse 25, A-1030, Wien, Vienna, Austria, camillo.sherif@cerebrovascular.at.
Background:
Thin cerebral aneurysm wall thickness (AWT) is connected to high aneurysm rupture risk. MR imaging of AWT leads to overestimations. The aim of the present study was to quantify MR inaccuracy by comparison with accurate light microscopic measurements.
Methods:
In 13 experimental microsurgical bifurcation aneurysms in rabbits, 3 Tesla (3 T)-MR imaging using contrast-enhanced T1 Flash sequences (resolution: 0.4 × 0.4 × 1.5 mm³) was performed. The aneurysms were retrieved immediately after MR acquisition, cut longitudinally, and calibrated photographs were obtained. AWT (dome, neck) and parent vessel thickness (PVT) were measured on the MR images and microscopic photographs by independent investigators. All parameters were statistically compared (Wilcoxon test, Spearman correlation).
Results:
AWT and PVT could be imaged and measured in all aneurysms with good quality. Comparison with the "real" light microscopic measurements showed a progressive tendency of MR AWT overestimation with smaller AWT: AWT at the dome (0.24 ± 0.06 mm vs. MR 0.30 ± 0.08 mm; p = 0.0078; R = 0.6125), AWT at the neck (0.25 ± 0.07 mm vs. MR 0.29 ± 0.07 mm; p = 0.0469; R = 0.7451), and PVT (0.46 ± 0.06 mm vs. MR 0.48 ± 0.06 mm; p = 0.5; R = 0.8568).
Conclusion:
In this experimental setting, 3 T-MR imaging of cerebral AWT showed unacceptable inaccuracies only below the image resolution threshold. Theoretically, AWT for clinical usage could be classified in ranges, defined by the maximum image resolution.
Insights
Magnetic Resonance (MR) imaging overestimates cerebral aneurysm wall thickness (AWT), particularly for thinner walls. This inaccuracy is below the resolution threshold of 3 T-MR imaging, suggesting clinical classification ranges based on resolution.
Area of Science:
- Neuroimaging
- Medical Imaging
- Vascular Biology
Background:
- Cerebral aneurysm wall thickness (AWT) is a critical determinant of rupture risk.
- Magnetic Resonance (MR) imaging is widely used for AWT assessment but is known to overestimate actual thickness.
- Accurate AWT measurement is crucial for predicting aneurysm rupture and guiding treatment decisions.
Purpose of the Study:
- To quantify the inaccuracy of 3 Tesla (3 T) MR imaging in measuring cerebral aneurysm wall thickness (AWT).
- To compare MR-based AWT measurements with precise light microscopic measurements in an experimental setting.
- To determine the threshold at which MR imaging inaccuracies become clinically significant for AWT assessment.
Main Methods:
- 13 experimental microsurgical bifurcation aneurysms in rabbits were imaged using 3 T-MR with contrast-enhanced T1 Flash sequences.
- Aneurysms were immediately retrieved post-imaging, sectioned longitudinally, and photographed for microscopic analysis.
- Aneurysm wall thickness (AWT) and parent vessel thickness (PVT) were independently measured from MR images and microscopic photographs.
Main Results:
- 3 T-MR imaging successfully visualized AWT and PVT in all experimental aneurysms with good image quality.
- MR imaging demonstrated a tendency to overestimate AWT, with greater inaccuracies observed for thinner walls.
- Overestimation was statistically significant for AWT at the dome (p=0.0078) and neck (p=0.0469), but not for PVT (p=0.5).
Conclusions:
- In this experimental model, 3 T-MR imaging of cerebral AWT exhibits unacceptable inaccuracies primarily for wall thicknesses below the imaging resolution limit.
- The findings suggest that clinical AWT classification could be stratified based on the maximum achievable image resolution.
- Further research may refine MR imaging protocols or post-processing techniques to improve AWT measurement accuracy.
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