MRA in the evaluation of EC-IC bypass patency
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Objective:
Our goal was to determine the value and limitations of three-dimensional (3D) time-of-flight (TOF) MR angiography (MRA) for evaluating the patency of extracranial (EC)-intracranial (IC) bypasses.
Materials And Methods:
The 3D TOF MRA was performed in 35 patients to evaluate their EC-IC bypasses (50 sites) at 1.5 T. Subtraction (rephased-dephased) MRA was performed to visualize slowly flowing blood in all patients. Angiographic images were obtained using maximum intensity projection from subtraction images and from rephased images.
Results:
The patency of bypasses was confirmed at 22 sites and was suggestive at 17 other sites using MRA alone. The diagnostic value of subtraction MRA proved to be superior to that of rephased MRA, and the findings of subtraction MRA correlated relatively well with those of conventional angiography. Edited reprojection MR angiograms were helpful in visualizing collateral vessels without overlapping of vessels.
Conclusion:
Although there have been some problems with MRA so far, it is a useful imaging modality for following up patients who have undergone EC-IC bypass operations, in conjunction with clinical examination, transcranial Doppler sonography, and cerebral blood flow studies using single photon emission CT or PET.
Insights
Three-dimensional (3D) time-of-flight (TOF) MR angiography (MRA) is a useful tool for evaluating extracranial-intracranial (EC-IC) bypasses. Subtraction MRA offers superior diagnostic value for assessing bypass patency in patients post-surgery.
Area of Science:
- Neurosurgery
- Radiology
- Vascular Imaging
Background:
- Extracranial-intracranial (EC-IC) bypass surgery is performed to restore cerebral blood flow.
- Accurate assessment of bypass patency is crucial for patient outcomes.
- Limitations exist in current imaging modalities for evaluating bypasses.
Purpose of the Study:
- To evaluate the diagnostic value and limitations of 3D time-of-flight (TOF) MR angiography (MRA).
- To assess the patency of EC-IC bypasses using 3D TOF MRA.
Main Methods:
- 3D TOF MRA was performed in 35 patients with 50 EC-IC bypass sites at 1.5 T.
- Subtraction (rephased-dephased) MRA was used to visualize slow blood flow.
- Maximum intensity projection (MIP) images were generated from subtraction and rephased data.
Main Results:
- MRA alone confirmed bypass patency at 22 sites and suggested patency at 17 sites.
- Subtraction MRA demonstrated superior diagnostic value compared to rephased MRA.
- Subtraction MRA findings correlated well with conventional angiography; edited reprojection MRA aided visualization of collateral vessels.
Conclusions:
- 3D TOF MRA is a valuable imaging modality for follow-up of EC-IC bypass patients.
- MRA should be used in conjunction with clinical examination and other functional studies (e.g., TCD, SPECT/PET).
- While challenges exist, MRA aids in monitoring bypass integrity post-surgery.
