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Start of funding 01.07.2008

Computer Vision Methods for Retrospective Motion Compensation in MR Imaging

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Despite major advances in magnetic resonance (MR) pulse sequences, motion still remains problematic. The efforts to prepare and conduct anesthesia to avoid patient motion are considerable, add significantly to the overall exam cost, and pose some secondary risk to the patient. The proposed research project is interested in the image driven correction of all types of patient motion. Motion compensation will be accomplished by determining the positional change of the head in real-time using a calibrated optical tracking and adjusting the acquisition frame of reference so that it follows the head movement and coincides with the original prescription. This both removes motion artifacts and minimizes spin history effects.

Final report:
Correcting patient motion in magnetic resonance imaging (MRI) is a challenge that is still not fully solved. Many correction approaches have been suggested, however, a considerable limitation for the majority of them is that they only work on a subset of pulse sequences used in MRI. From a routine clinical imaging perspective this is inadequate. Recently, a new and more promising selection of motion correction methods have been suggested that rely on optical pose tracking, and work prospectively. Furthermore, they are MR data acquisition independent. A lately proposed method utilizes a checkerboard marker attached to the patient’s forehead that is tracked by an MRI-compatible camera setup placed inside the scanner. One potential limitation of this approach, however, is the restricted field of view of the camera due to the constricted space inside the scanner bore. This restricts the amount of motion that can be reliably detected to a narrow range, and also renders the approach sensitive to where the marker is placed within the field of view of the camera. To overcome these restrictions, a self-encoded marker design was developed and compared against the conventional checkerboard marker. The new marker design offered considerable advantages over a checkerboard marker in terms of accuracy and precision over a much wider range of pose changes. In-vivo experiments were of great diagnostic quality and the system was essentially able to adapt to motion over the entire range of possible motion within the MR head coil [1,2,3,4].

Publications that acknowledge the BaCaTeC grant:

[1] Aksoy, Murat; Forman, Christoph; Straka, Matus; Çukur, Tolga; Hornegger, Joachim; Bammer, Roland - Hybrid Prospective & Retrospective Head Motion Correction System to Mitigate Cross-Calibration Errors - Magnetic Resonance in Medicine, Volume 67, Issue 5, pages 1237–1251, May 2012
[2] Forman, Christoph; Aksoy, Murat; Hornegger, Joachim; Bammer, Roland Self-encoded marker for optical prospective head motion correction in MRI Medical Image Analysis, vol. 15, no. 5, pp. 708-719, 2011
[3] Forman, Christoph; Aksoy, Murat; Straka, Matus; Hornegger, Joachim; Bammer, Roland Extending the Tracking Range for Prospective Motion Correction using a Single In-bore Camera and the Self-Encoded Marker Proceedings of the ISMRM Workshop on Current Concepts of Motion Correction for MRI & MRS (ISMRM Workshop on Current Concepts of Motion Correction for MRI & MRS), Kitzbühel, Austria, 24-28.2.2010, pp. -, 2010
[4] Forman, Christoph; Aksoy, Murat; Hornegger, Joachim; Bammer, Roland Self-encoded Marker for Optical Prospective Head Motion Correction in MRI Lecture Notes in Computer Science (Medical Image Computing and Computer-Assisted Intervention MICCAI 2010), Beijing, China, 20-24.9.2010, vol. 6361, pp. 259-266, 2010