Selfencoded marker for optical prospective head motion correction in MRI. The tracking and compensation of patient motion during a magnetic resonance imaging (MRI) acqusition is an unsolved problem. For brain MRI, a promising approach recently suggested is to track the patient using an inbore camera and a checkerboard marker attached to the patientu0027s forehead. However, the possible tracking range of the head pose is limited by the locally attached marker that must be entirely visible inside the camerau0027s narrow field of view (FOV). To overcome this shortcoming, we developed a novel selfencoded marker where each feature on the pattern is augmented with a 2D barcode. Hence, the marker can be tracked even if it is not completely visible in the camera image. Furthermore, it offers considerable advantages over the checkerboard marker in terms of processing speed, since it makes the correspondence search of feature points and markermodel coordinates, which are required for the pose estimation, redundant. The motion correction with the novel selfencoded marker recovered a rotation of 18 degrees around the principal axis of the cylindrical phantom inbetween two scans. After rigid registration of the resulting volumes, we measured a maximal error of 0.39 mm and 0.15 degrees in translation and rotation, respectively. In invivo experiments, the motion compensated images in scans with large motion during data acquisition indicate a correlation of 0.982 compared to a corresponding motionfree reference.

DYSKIMOT: An UltraLowCost Inertial Sensor to Assess Headxe2x80x99s Rotational Kinematics in Adults during the DidrenLaser Test Various noninvasive measurement devices can be used to assess cervical motion. The size, complexity, and cost of goldstandard systems make them not suited to clinical practice, and actually difficult to use outside a dedicated laboratory. Nowadays, ultralowcost inertial measurement units are available, but without any packaging or a userfriendly interface. The socalled DYSKIMOT is a homedesigned, smallsized, motion sensor based on the latter technology, aiming at being used by clinicians in xe2x80x9creallife situationsxe2x80x9d. DYSKIMOT was compared with a goldstandard optoelectronic system (Elite). Our goal was to evaluate the DYSKIMOT accuracy in assessing fast head rotations kinematics. Kinematics was simultaneously recorded by systems during the execution of the DidRen Laser test and performed by 15 participants and nine patients. Kinematic variables were computed from the position, speed and acceleration time series. Twoway ANOVA, Passingxe2x80x93Bablok regressions, and dynamic time warping analysis showed good to excellent agreement between Elite and DYSKIMOT, both at the qualitative level of the time series shape and at the quantitative level of peculiar kinematical eventsxe2x80x99 measured values. In conclusion, DYSKIMOT sensor is as relevant as a goldstandard system to assess kinematical features during fast head rotations in participants and patients, demonstrating its usefulness in both clinical practice and research environments.