Compressed sensing time-of-flight magnetic resonance angiography with high spatial resolution for evaluating intracranial aneurysms: comparison with digital subtraction angiography

Abstract

Background and purpose: Compressed sensing is used for accelerated acquisitions with incoherently under-sampled k-space data, and intracranial time-of-flight magnetic resonance angiography is suitable for compressed sensing. Compressed sensing time-of-flight is beneficial in decreasing acquisition time and increasing spatial resolution while maintaining acquisition time. In this retrospective study, we aimed to evaluate the image quality and diagnostic performance of compressed sensing time-of-flight with high spatial resolution and compare with parallel imaging time-of-flight using digital subtraction angiography as a reference.

Material and methods: In total, 39 patients with 46 intracranial aneurysms underwent parallel imaging and compressed sensing time-of-flight in the same imaging session and digital subtraction angiography before or after magnetic resonance angiography. The overall image quality, artefacts and diagnostic confidence were assessed by two observers. The contrast ratio, maximal aneurysm diameters and diagnostic performance were evaluated.

Results: Compressed sensing time-of-flight showed significantly better overall image quality, degree of artefacts and diagnostic confidence in both observers, with better inter-observer agreement. The contrast ratio was significantly higher for compressed sensing time-of-flight than for parallel imaging time-of-flight in both observers (source images, P < 0.001; maximum intensity projection images, P < 0.05 for both observers); however, the measured maximal diameters of aneurysms were not significantly different. Compressed sensing time-of-flight showed higher sensitivity, specificity, accuracy and positive and negative predictive values for detecting aneurysms than parallel imaging time-of-flight in both observers, with better inter-observer agreement. Compressed sensing time-of-flight was preferred over parallel imaging time-of-flight by both observers; however, parallel imaging time-of-flight was preferred in cases of giant and large aneurysms.

Conclusions: Compressed sensing-time-of-flight provides better image quality and diagnostic performance than parallel imaging time-of-flight. However, neuroradiologists should be aware of under-sampling artefacts caused by compressed sensing.

Keywords: Compressed sensing; cerebral aneurysm; time-of-flight magnetic resonance angiography.

Figure 1.

Maximum intensity projections and digital subtraction angiography (DSA) of a 48-year-old patient. Small saccular aneurysms at the right paraclinoid internal carotid artery and junctional dilation at the left posterior communicating artery are clearer on compressed sensing time-of-flight (TOF) (a, b) than parallel imaging TOF (c, d) and are more similar to DSA (e, f).

Figure 2.

Maximum intensity projections and digital subtraction angiography (DSA) of a 71-year-old patient. A giant aneurysm was located at the left paraclinoid internal carotid artery. Compressed sensing time-of-flight (TOF; a) shows decreased blood flow of the left distal M1 and M2 segments, but parallel imaging TOF (b) shows relatively well-visualised blood flow of the left distal M1 and M2 segments. There was no significant steno-occlusive lesion at the left distal M1 or M2 segments on DSA (c).

Figure 3.

Maximum intensity projections and digital subtraction angiography (DSA) of a 60-year-old patient. Large aneurysms are located at the left paraclinoid internal carotid artery and basilar artery. Compressed sensing time-of-flight (TOF; a) shows decreased blood flow of both distal M1 and M2, but parallel imaging TOF (b) shows relatively better blood flow of both the M2 segments. There was no significant steno-occlusive lesion at the left distal M1 and M2 segments on DSA (c).