title: Hybrid prospective and retrospective head motion correction to mitigate cross-calibration errors.
abstract: Utilization of external motion tracking devices is an emerging technology in head motion correction for MRI. However, cross-calibration between the reference frames of the external tracking device and the MRI scanner can be tedious and remains a challenge in practical applications. In this study, we present two hybrid methods, both of which combine prospective, optical-based motion correction with retrospective entropy-based autofocusing to remove residual motion artifacts. Our results revealed that in the presence of cross-calibration errors between the optical tracking device and the MR scanner, application of retrospective correction on prospectively corrected data significantly improves image quality. As a result of this hybrid prospective and retrospective motion correction approach, the requirement for a high-quality calibration scan can be significantly relaxed, even to the extent that it is possible to perform external prospective motion tracking without any prior cross-calibration step if a crude approximation of cross-calibration matrix exists. Moreover, the motion tracking system, which is used to reduce the dimensionality of the autofocusing problem, benefits the retrospective approach at the same time.
authors.affiliation: Department of Radiology, Stanford University, Stanford, California 94305-5488, USA. maksoy@stanford.edu
authors.forename: Murat
authors.initials: M
authors.lastname: Aksoy
authors.forename: Christoph
authors.initials: C
authors.lastname: Forman
authors.forename: Matus
authors.initials: M
authors.lastname: Straka
authors.forename: Tolga
authors.initials: T
authors.lastname: Çukur
authors.forename: Joachim
authors.initials: J
authors.lastname: Hornegger
authors.forename: Roland
authors.initials: R
authors.lastname: Bammer
mesh_terms: D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology*; D002138:Calibration; D004867:Equipment Design; D019544:Equipment Failure Analysis; D019416:Head Movements; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation* / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods* / Q000592:standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity