Detection of aneurysms by 64-section multidetector CT angiography in patients acutely suspected of having an intracranial aneurysm and comparison with digital subtraction and 3D rotational angiography

Abstract

Background and purpose: Four-section multisection CT angiography (MSCTA) accurately detects aneurysms at or more than 4 mm but is less accurate for those less than 4 mm. Our purpose was to determine the accuracy of 64-section MSCTA (64MSCTA) in aneurysm detection versus combined digital subtraction angiography (DSA) and 3D rotational angiography (3DRA).

Materials and methods: In a retrospective review of patients studied because of acute symptoms suspicious for arising from an intracranial aneurysm, 63 subjects were included who had undergone CT angiography (CTA). Of these, 36 underwent catheter DSA; all but 4 were also studied with 3DRA. The most common indication was subarachnoid hemorrhage (SAH; n = 43). Two neuroradiologists independently reviewed each CTA, DSA, and 3DRA.

Results: A total of 41 aneurysms were found in 28 patients. The mean size was 6.09 mm on DSA/3DRA and 5.98 mm on 64MSCTA. kappa was excellent (0.97) between the aneurysm size on 64MSCTA and DSA/3DRA. Ultimately, 37 aneurysms were detected by DSA/3DRA in 25 of the 36 patients who underwent conventional angiography. The reviewers noted four 1- to 1.5-mm sessile outpouchings only on 3DRA; none were considered a source of SAH. One 64MSCTA was false positive, whereas one 2-mm aneurysm was missed by CTA. The sensitivity of CTA for aneurysms less than 4 mm was 92.3%, whereas it was 100% for those 4-10 mm and more than 10 mm, excluding the indeterminate, sessile lesions.

Conclusions: In comparison with the available literature, 64MSCTA may have improved the detection of less than 4-mm aneurysms compared with 4- or 16-section CTA. However, the combination of DSA with 3DRA is currently the most sensitive technique to detect untreated aneurysms and should be considered in suspicious cases of SAH where the aneurysm is not depicted by 64MSCTA, because 64MSCTA may occasionally miss aneurysms less than 3-4 mm size.

Fig 1.

An 83-year-old woman with SAH and an aneurysm less than 4 mm. Emergent CTA showed a 2-mm MCA bifurcation aneurysm. This was difficult to visualize on conventional DSA (not shown) but was confirmed on 3DRA (B) and surgically.

Fig 2.

A 47-year-old woman with SAH and multiple 4- to 10-mm aneurysms; aneurysm measurement technique is demonstrated. MSCTA showed 3 aneurysms: a 7 mm basilar tip aneurysm (arrowhead, A), a right posterior communicating artery (PcomA) segment aneurysm (solid arrow, A), and a fenestrated, fusiform anterior communicating artery (AcomA, dashed arrow, A). Sectioned 3D (B, top) and MPR (B, bottom) images were used to measure the PcomA aneurysm. 3DRA demonstrated the PcomA (gold arrow denotes the site of hemorrhage, C) and the double-fenestration AcomA (dashed red arrows, C).

Fig 3.

A 78-year-old woman with SAH from an aneurysm more than 10 mm in size. MSCTA showed a 12-mm aneurysm in the periophthalmic ICA segment on 3D-VR images (data not shown), with peripheral calcifications, best seen on MPR (short white arrows, A). The aneurysm was noted to be separate from the ophthalmic artery origin on 3DRA (black arrow, B).

Fig 4.

The only false-negative CTA, in a 72-year-old man with severe headache, lacking hemorrhage on CT. However, the symptoms prompted an MR imaging/MR angiography (data not shown), with tiny infarcts and a questionable left supraclinoid ICA outpouching. Thereafter, the patient underwent catheter DSA to exclude vasculitis (which was negative), which showed a 2-mm periophthalmic aneurysm on 3DRA (dashed arrow, A). Closer, repeat review of the CTA showed the lesion projecting medially over the bony sella (arrow, B).

Fig 5.

The only false-positive CTA. A 38-year-old woman with confusion had a head CT negative for hemorrhage but with an isoattenuated structure in the region of the left MCA (data not shown) and corresponding flow void on T2-weighted MR imaging (data not shown), suspicious for aneurysm. Both 16-section (data not shown) and repeat 64-section CTA were performed, which showed a bizarre 6- to 7-mm outpouching (question marks, A and B) overlying the left MCA bifurcation on MPR axial (A, top) and coronal (A, bottom) and 3D MIP/VR posterior (B, top) and superior (B, bottom) views. This was considered a prominent middle cerebral venous plexus, because the catheter DSA and 3DRA (data not shown) were completely negative.

Fig 6.

Blisterlike lesion in a 46-year-old man with SAH from a 3.5-mm MCA aneurysm, noted on CTA and 3DRA (asterisk, A). The sessile lesion was noted on the undersurface of the ICA and not noted on CTA 3D-VR (data not shown) or MPR (B) views. This was not changed on 2-week repeat catheter 3DRA.

Fig 7.

Atherosclerosis simulating a blister-like lesion. A 52-year-old woman with SAH and focal parenchymal hematoma on CT. CTA showed a 2.9-mm M3 mycotic aneurysm adjacent to the hematoma, also present on 3DRA (dashed arrows, A and B). However, a sessile outpouching was noted on the cavernous ICA undersurface (solid arrows, A and B). Further review of the CTA MPR images revealed this to be an atherosclerotic calcification (pink arrow, C).