Autocorrection of three-dimensional time-of-flight MR angiography of the circle of Willis

OBJECTIVE. The purpose of this study was to investigate the efficacy of a r etrospective adaptive motion correction technique known as autocorrection f or reducing motion-induced artifacts in high-resolution three-dimensional t ime-of-flight MR angiography of the circle of Willis. MATERIALS AND METHODS. Ten consecutive volunteers were imaged with an un en hanced gradient-recalled echo three-dimensional time-of-flight MR angiograp hy sequence of the circle of Willis. Each volunteer was asked to rotate app roximately 2 degrees after completion of one third and one half of the acqu isition in the axial, sagittal, and oblique planes (45 degrees to the axial and sagittal planes). A single static data set was also acquired for each volunteer. Unprocessed and autocorrected maximum-intensity-projection image s were reviewed as blinded image pairs by six radiologists and were compare d on a five-point image quality scale. RESULTS. Mean improvement in image quality after autocorrection was 1.4 (p < 0.0001), 1.1 (p < 0.0001), and 0.2(p = 0.003) observer points (maximum va lue, 2.0), respectively, for examinations corrupted by motion in the axial, oblique, and sagittal planes. All three axes had statistically significant improvement in image quality compared with the uncorrected images. Changes in image quality after the application of the autocorrection algorithm to static angiogram data were not statistically significant (mean change in sc ore = -0.13 points: p = 0.29). CONCLUSION. Autocorrection can reduce artifacts in motion-corrupted MR angi ography of the circle of Willis without distorting motion-free examinations .