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Hyperintense thrombus on GRASS MR images: potential pitfall in flow evaluation
D M Yousem1, J Balakrishnan, G M Debrun
1Neuroradiology Division, Johns Hopkins Hospital, Baltimore, MD 21205.
Abstract:
Gradient-recalled acquisition in the steady state (GRASS) MR images, obtained in four patients with angiographic evidence of successful occlusion of cerebral arteriovenous malformations, demonstrated hyperintense signal intraluminally. Although this was initially mistaken as evidence of persistent blood flow in the arteriovenous malformation, the short TR/TE spin-echo images showed hyperintense signal rather than flow void, thereby indicating the presence of subacute thrombus. GRASS images alone should not be used to determine the success of embolotherapy of cerebral arteriovenous malformations or to determine aneurysm patency, since the hyperintense signal is a potential pitfall that may mislead the radiologist in the absence of corroborative images, particularly the short TR/TE spin-echo sequences.
Insights
Gradient-recalled acquisition in the steady state (GRASS) MRI may show intraluminal hyperintensity mimicking persistent blood flow in treated arteriovenous malformations. Short TR/TE spin-echo sequences are crucial for accurate assessment of embolization success.
Area of Science:
- Neuroradiology
- Vascular Imaging
- Magnetic Resonance Imaging (MRI)
Background:
- Gradient-recalled acquisition in the steady state (GRASS) is a common MRI sequence used in neurovascular imaging.
- Assessing the success of embolization for cerebral arteriovenous malformations (AVMs) requires accurate differentiation between residual blood flow and post-treatment changes.
Observation:
- In four patients with successfully occluded cerebral AVMs, GRASS MRI demonstrated intraluminal hyperintense signal.
- This hyperintensity was initially misinterpreted as persistent blood flow.
- Short TR/TE spin-echo sequences revealed hyperintense signal instead of expected flow void, indicating subacute thrombus.
Findings:
- GRASS MRI findings of intraluminal hyperintensity in treated AVMs can be misleading.
- The hyperintensity observed is indicative of subacute thrombus, not residual blood flow.
- Short TR/TE spin-echo sequences are essential for correct interpretation.
Implications:
- GRASS images alone are insufficient for determining the success of AVM embolization or aneurysm patency.
- Radiologists must use corroborative imaging, especially short TR/TE spin-echo sequences, to avoid misinterpretation of subacute thrombus as flow.
- Accurate assessment is critical for patient management and treatment planning in neurovascular interventions.