Detection and Characterization of Intracranial Aneurysms with MR Angiography: Comparison of Volume-Rendering and Maximum-Intensity-Projection Algorithms

Detection and Characterization of Intracranial Aneurysms with MR Angiography: Comparison of Volume-Rendering and Maximum-Intensity-Projection Algorithms

Ammar Mallouhi¹, Stephan Felber, Andreas Chemelli, Andreas Dessl, Alexandra Auer, Michael Schocke, Werner R. Jaschke and Peter Waldenberger

^¹ All authors: Department of Radiology, Innsbruck University Hospital, Anichstr. 35, 6020 Innsbruck, Austria.

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Fig. 1A. —Graphs shows parametric receiver operating characteristic curves representing findings of both reviewers for maximum-intensity-projection and volume-rendering algorithms. For detection of any aneurysm, area under curve, from top to bottom, was 0.96 (p < 0.001) for reviewer 1 and 0.94 (p < 0.001) for reviewer 2 for volume-rendered images, and 0.91 (p < 0.001) for reviewer 2 and 0.89 (p < 0.001) for reviewer 1 for maximum-intensity-projection images.

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Fig. 2A. —38-year-old man with three intracranial aneurysms. Coronal left oblique digital subtraction angiogram depicts round 2-mm aneurysm (small arrow) of anterior cerebral artery and lobulated 5-mm aneurysm (large arrow) at bifurcation of internal carotid artery.

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Fig. 2B. —38-year-old man with three intracranial aneurysms. Coronal oblique subvolume maximum-intensity-projection image from MR angiography shows both aneurysms; however, aneurysm (arrow) of anterior cerebral artery was categorized as probably present by one reviewer and was not seen by second reviewer.

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Fig. 2C. —38-year-old man with three intracranial aneurysms. Left oblique volume-rendered image from MR angiography shows both aneurysms, which were detected with certainty by both reviewers, with superior depiction of anterior cerebral artery aneurysm (arrow).

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Fig. 1B. —Graphs shows parametric receiver operating characteristic curves representing findings of both reviewers for maximum-intensity-projection and volume-rendering algorithms. For detection of lobulated aneurysms, area under curve was 0.97 (p < 0.001) for reviewer 1 (dashed line) and 0.95 (p < 0.001) for reviewer 2 (solid line) for volume-rendered images, and 0.70 (p = 0.061) for reviewer 1 (dashed and dotted lines) and 0.69 (p = 0.067) for reviewer 2 (dotted line) for maximum-intensity-projection images.

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Fig. 3A. —46-year-old woman with multiple intracranial aneurysms. Inferosuperior left oblique three-dimensional digital subtraction angiogram shows lobulated 4-mm aneurysm (straight arrow) at bifurcation of left middle cerebral artery. Note, in addition, two aneurysms of left internal carotid artery (at carotid arterial bifurcation, curved arrow, and at C7 segment, arrowhead) that were treated with detachable coils.

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Fig. 3B. —46-year-old woman with multiple intracranial aneurysms. Subvolume oblique axial maximum-intensity-projection image from MR angiography clearly depicts aneurysm (arrow) of middle cerebral artery, but its morphology is not clearly shown.

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Fig. 3C. —46-year-old woman with multiple intracranial aneurysms. Inferosuperior left oblique volume-rendered image from MR angiography shows aneurysm (solid arrow) of middle cerebral artery and reveals its morphology and relationship to parent vessels. Image also shows aneurysms (arrowheads) of left internal carotid artery and one of right internal carotid artery (at C6 segment, open arrow) before treatment.

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Fig. 4A. —Diagrams show results of limits-of-agreement analysis, in which differences between MR angiographic reconstructions and digital subtraction angiograms (DSA) are plotted against their means. Diagram shows good agreement between digital subtraction angiography and maximum intensity projection (MIP), inferred from bias of -1.3 mm (solid line) with relatively wide range of agreement (±2 SD; ±2.84 mm; dashed lines).

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Fig. 4B. —Diagrams show results of limits-of-agreement analysis, in which differences between MR angiographic reconstructions and digital subtraction angiograms (DSA) are plotted against their means. Diagram shows considerably better agreement between digital subtraction angiography and volume rendering (VR), inferred from smaller bias of -0.3 mm (solid line) and narrower range of agreement (±2 SD; ±1.62 mm; dashed lines).

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Fig. 5A. —64-year-old woman with two aneurysms of internal carotid artery. Right oblique digital subtraction angiogram depicts oblong aneurysm (arrow) of right internal carotid artery (at C6 segment) with narrow neck.

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Fig. 5B. —64-year-old woman with two aneurysms of internal carotid artery. Subvolume oblique sagittal maximum-intensity-projection image from MR angiography shows aneurysm (open arrow) of internal carotid artery depicted in A but does not optimally reveal aneurysm neck. Image also depicts second 2-mm aneurysm (solid arrow) of right internal carotid artery at C7 segment that was also detected on digital subtraction angiography (not shown).

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Fig. 5C. —64-year-old woman with two aneurysms of internal carotid artery. Right oblique volume-rendered image from MR angiography depicts oblong aneurysm (open arrow) and reveals more detailed information about origin and morphology of aneurysm neck. Volume-rendered image also shows small round aneurysm (solid arrow) of internal carotid artery.

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Fig. 6A. —35-year-old man with 6-mm aneurysm at trifurcation of right middle cerebral artery. Superoanterior three-dimensional digital subtraction angiogram depicts aneurysm (arrowhead) of right middle cerebral artery and shows that all three M2 segments of middle cerebral artery are incorporated in aneurysm pouch.

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Fig. 6B. —35-year-old man with 6-mm aneurysm at trifurcation of right middle cerebral artery. Subvolume axial oblique maximum-intensity-projection image from MR angiography depicts aneurysm (arrowhead) and shows three vessels arising from it.

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Fig. 6C. —35-year-old man with 6-mm aneurysm at trifurcation of right middle cerebral artery. Superoanterior volume-rendered image from MR angiography shows aneurysm (arrow) and three arising M2 segments with considerably better vascular delineation than in B

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