MR imaging: influence of imaging technique and postprocessing on measurement of internal carotid artery stenosis
F Runck1, R P Steiner, W A Bautz
1Department of Radiology and Neuroradiology, Klinikum Augsburg, Augsburg, Germany. frank.runck@klinikum-augsburg.de
Background And Purpose:
MR angiography (MRA) is increasingly used as an alternative to digital subtraction angiography (DSA) to evaluate internal carotid artery (ICA) stenosis. Because MRA is not standardized in data acquisition and postprocessing, we sought to evaluate the effects of different acquisition techniques (time-of-flight MRA [TOF-MRA]) and contrast-enhanced MRA [CE-MRA]) and postprocessing methods (maximum intensity projection [MIP], multiplanar reformation [MPR], and volume-rendering on stenosis grading.
Materials And Methods:
Fifty patients (33 men, 17 women) with symptomatic ICA stenosis were examined at 1.5T. Two imaging techniques and 3 postprocessing methods resulted in 6 image datasets per patient. Two readers independently evaluated ICA stenosis according to the North American Symptomatic Carotid Endarterectomy Trial criteria. Interobserver variability was calculated with the Pearson correlation coefficient and simultaneous confidence intervals (CI). The relationship of the values of ICA stenosis between the techniques was assessed by means of simultaneous 95% Tukey CI.
Results:
Interobserver agreement was high. Higher concordance was found for postprocessing techniques with TOF- than with CE-MRA; the mean difference between TOF-MPR and TOF-MIP was 0.4% (95% CI, -2.9%-3.8%). Stenosis values for CE-MPR differed significantly from those of CE volume-rendering (7.2%; 95% CI, 3.9%-10.6%).
Conclusion:
Stenosis grading was found to be independent of the postprocessing technique except for comparison of CE-MPR with CE volume-rendering, with the volume-rendering technique resulting in higher stenosis values. MPR seems to be best-suited for measurement of ICA stenosis. Parameter setting is critical with volume-rendering, in which stenosis values were consistently higher compared with the other methods.
Insights
Different MR angiography (MRA) techniques and postprocessing methods impact internal carotid artery (ICA) stenosis grading. Multiplanar reformation (MPR) is best suited for ICA stenosis measurement, while volume-rendering requires careful parameter setting.
Area of Science:
- Radiology
- Medical Imaging
- Neurovascular Imaging
Background:
- MR angiography (MRA) is an emerging alternative to digital subtraction angiography (DSA) for evaluating internal carotid artery (ICA) stenosis.
- Standardization of MRA acquisition and postprocessing techniques is lacking, necessitating evaluation of different methods.
Purpose of the Study:
- To assess the impact of various MRA acquisition techniques (TOF-MRA, CE-MRA) and postprocessing methods (MIP, MPR, volume-rendering) on internal carotid artery (ICA) stenosis grading.
- To determine the optimal postprocessing technique for accurate ICA stenosis assessment.
Main Methods:
- Fifty patients with symptomatic ICA stenosis underwent 1.5T MRA using two acquisition techniques and three postprocessing methods, generating six datasets per patient.
- Two independent readers graded ICA stenosis using North American Symptomatic Carotid Endarterectomy Trial criteria.
- Interobserver variability and differences between techniques were statistically analyzed.
Main Results:
- High interobserver agreement was observed for all tested MRA techniques and postprocessing methods.
- Postprocessing concordance was higher with time-of-flight MRA (TOF-MRA) compared to contrast-enhanced MRA (CE-MRA).
- CE-MPR showed significant differences in stenosis values compared to CE volume-rendering, with higher values for volume-rendering.
Conclusions:
- Multiplanar reformation (MPR) is recommended as the most suitable postprocessing technique for measuring ICA stenosis.
- Volume-rendering techniques can lead to higher stenosis values and require critical parameter adjustments for accurate grading.
- Stenosis grading is generally independent of postprocessing technique, with notable exceptions requiring careful consideration.
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