Clinical Evaluation of Highly Accelerated Compressed Sensing Time-of-Flight MR Angiography for Intracranial Arterial Stenosis

Abstract

Background and purpose: Time-of-flight MR angiography is the preferred imaging technique to assess intracranial arterial stenosis but is limited by a relatively long acquisition time. Compressed sensing provides an innovative approach in undersampling k-space to minimize the data-acquisition time. We aimed to evaluate the diagnostic accuracy of compressed sensing TOF for detecting intracranial arterial stenosis by comparison with conventional parallel imaging TOF-MRA.

Materials and methods: Compressed sensing TOF and parallel imaging TOF were performed in 22 patients with intracranial arterial stenosis. The MRA scan times were 2 minutes and 31 seconds and 4 minutes and 48 seconds for compressed sensing TOF and parallel imaging TOF, respectively. The reconstructed resolutions were 0.4 × 0.4 × 0.4 and 0.4 × 0.4 × 0.6 mm³ for compressed sensing TOF and parallel imaging TOF, respectively. The diagnostic quality of the images and visibility of the stenoses were independently ranked by 2 neuroradiologists blinded to the type of method and were compared using the Wilcoxon signed rank test. Concordance was calculated with the Cohen κ. Edge sharpness of the arteries and the luminal stenosis ratio were analyzed and compared using a paired-sample t test.

Results: The interrater agreement was good to excellent. Compressed sensing TOF resulted in image quality comparable with that of parallel imaging TOF but boosted confidence in diagnosing arterial stenoses (P = .025). The edge sharpness of the intracranial arteries for compressed sensing TOF was significantly higher than that for parallel imaging TOF (P < .001). The luminal stenosis ratio on compressed sensing TOF showed no significant difference compared with that on parallel imaging TOF.

Conclusions: Compressed sensing TOF both remarkably reduced the scan time and provided adequate image quality for the diagnosis of intracranial arterial stenosis.

Fig 1.

Source images and coronal view of MIP images in a 42-year-old patient. The speckled noise in the center can be seen on the source image of conventional PI-TOF (A), whereas some artifacts with a curved stripe pattern can be seen on the source image of CS-TOF (C). These artifacts are eliminated on the MIP images and have little effect on the visualization of the stenosis. An obvious stenosis located in the M1 segment of the left middle cerebral artery is sufficiently visualized on both PI-TOF (B) and CS-TOF (D) (arrowheads). The edge sharpness of vessels on CS-TOF (D) is higher than that on PI-TOF (B) (short arrows). The image quality of the right intracranial internal carotid artery (long arrow, B) is improved on CS-TOF (D).

Fig 2.

MIP images of a 68-year-old patient. Mild stenosis located in the proximal M1 segment of left middle cerebral artery can be sufficiently visualized on both PI-TOF (A) and CS-TOF (B) (arrowheads). The edge sharpness of vessels on CS-TOF is higher than that on PI-TOF (arrows).

Fig 3.

The degree of each luminal stenosis measured on CS-TOF and PI-TOF, respectively.

Fig 4.

Bar plots of the 2 readers' preferences. CS-TOF is considered not inferior to PI-TOF in all cases. In 50.0% and 45.5% of patients, the diagnostic quality of CS-TOF is considered better than that of PI-TOF by each of the 2 readers.