Registration Method Between Phase-Contrast Magnetic Resonance Angiography and Time-of-Flight Magnetic Resonance Angiography—A Preliminary Study

Purpose: To evaluate a new method that registers phase-contrast magnetic resonance angiography images to time-of-flight magnetic resonance angiography images. Methods: Magnetic resonance angiography datasets of 10 healthy volunteers obtained by using two modalities (phase-contrast magnetic resonance angiography and time-of-flight magnetic resonance angiography) were preprocessed. Specifically, vessel regions were extracted using the region growing method with a threshold of 10% of the signal intensity maximum or 50% of the signal intensity maximum for phase-contrast magnetic resonance angiography images and time-of-flight magnetic resonance angiography images, respectively. Then, the normalized mutual information method was used to determine spatial positions, and registration between non-preprocessed phase-contrast magnetic resonance angiography and time-of-flight magnetic resonance angiography was performed using the spatial position information. Misalignment of 3 anatomical points was used to compare the accuracy of registration in this data group (the proposed method group) to that in the data group without registration (the non-registration group) and that in the data group subjected to normalized mutual information-based registration without preprocessing (the non-preprocessing group). Results: The mean misalignment of 3 anatomical points ± standard error was 1.69 ± 0.11 mm in the proposed method group, and 2.77± 0.13 mm and 90.28 ± 8.24 mm in the non-registration group and non-preprocessing group, respectively. The mean misalignment of 3 anatomical points was significantly smaller in the proposed method group than in the non-registration group (p = 0 001). Conclusions: The proposed preprocessing and registration method improved the accuracy of normalized mutual information-based registration between phase-contrast magnetic resonance angiography images and time-of-flight magnetic resonance angiography images.