Ultra-High-Resolution Time-of-Flight MR-Angiography for the Noninvasive Assessment of Intracranial Aneurysms, Alternative to Preinterventional DSA?

Abstract

Purpose: The 3D time-of-flight (TOF) magnetic resonance angiography (MRA) at 3T shows high sensitivity for intracranial aneurysms but is inferior to three-dimensional digital subtraction angiography (3D-DSA) regarding aneurysm characteristics. We applied an ultra-high-resolution (UHR) TOF-MRA using compressed sensing reconstruction to investigate the diagnostic performance in preinterventional evaluation of intracranial aneurysms compared to conventional TOF-MRA and 3D-DSA.

Methods: In this study 17 patients with unruptured intracranial aneurysms were included. Aneurysm dimensions, configuration, image quality and sizing of endovascular devices were compared between conventional TOF-MRA at 3T and UHR-TOF with 3D-DSA as gold standard. Quantitatively, contrast-to-noise ratios (CNR) were compared between TOF-MRAs.

Results: On 3D-DSA, 25 aneurysms in 17 patients were detected. On conventional TOF, 23 aneurysms were detected (sensitivity: 92.6%). On UHR-TOF, 25 aneurysms were detected (sensitivity: 100%). Image quality was not significantly different between TOF and UHR-TOF (p = 0.17). Aneurysm dimension measurements were significantly different between conventional TOF (3.89 mm) and 3D-DSA (4.2 mm, p = 0.08) but not between UHR-TOF (4.12 mm) and 3D-DSA (p = 0.19). Irregularities and small vessels at the aneurysm neck were more frequently correctly depicted on UHR-TOF compared to conventional TOF. Comparison of the planned framing coil diameter and flow-diverter (FD) diameter revealed neither a statistically significant difference between TOF and 3D-DSA (coil p = 0.19, FD p = 0.45) nor between UHR-TOF and 3D-DSA (coil: p = 0.53, FD 0.33). The CNR was significantly higher in conventional TOF (p = 0.009).

Conclusion: In this pilot study, ultra-high-resolution TOF-MRA visualized all aneurysms and accurately depicted aneurysm irregularities and vessels at the base of the aneurysm comparably to DSA, outperforming conventional TOF. UHR-TOF with compressed sensing reconstruction seems to represent a non-invasive alternative to pre-interventional DSA for intracranial aneurysms.

Keywords: Compressed sensing; Digital subtraction angiography; MR-angiography; Non-invasive assessment; Post-treatment; Pre-treatment.

Fig. 1

Representative measurements of the aneurysm height and largest diameter aneurysm neck on UHR-TOF (a), conventional TOF (b) and 3D-DSA (c). The aneurysm neck to the anterior communicating artery is more clearly demarcated on UHR-TOF and 3D-DSA compared to conventional TOF

Fig. 2

On ultra-high-resolution-time-of-flight (TOF) MRA (multiplanar [MPR], b) and volume rendering (VR, d) reconstructions), one small aneurysm adjacent to a larger inferior wall carotid artery aneurysm can be clearly separated (white arrows). On conventional TOF, the aneurysms appear as one broad-based aneurysm (MPR (a) and VR (c)). The additional aneurysm was confirmed on 3D-digital subtraction angiography (e, arrow). Conventional TOF parameters are TR/TE 23/3.4 ms, FA 18°, acquisition matrix 500/333, field of view 200 × 200 mm, slice thickness 0.6 mm

Fig. 3

UHR-TOF shows a recurrent, previously clipped and coiled carotid‑T aneurysm in multiplanar (MPR) and volume rendered (VR) reconstructions (a, c, arrows), which was confirmed by DSA (e, f, arrows). The recurrence is not visible on the conventional TOF VR reconstruction and to a limited extent on the MPR reconstruction (b, d, arrows). Conventional TOF parameters are TR/TE 21/3.4 ms, FA 25°, acquisition matrix: 320/238, field of view: 190×165 mm, slice thickness 0.6 mm

Fig. 4

The origin of the common pericallosal artery variant at the aneurysm neck is visualized on UHR-TOF (a, c, arrows) but not on conventional TOF (b, d) and 3D-DSA (e). The vessel origin is confirmed on 2D DSA (f, arrow). Lack of visualization in 3D DSA is due to wash out from the contralateral A1 segment