Johannes Fischer1, Timo Abels1, Ali Caglar Özen1,2, Matthias Echternach3, Bernhard Richter4, Michael Bock1. 1. Department of Radiology, Medical Physics, Medical Center University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany. 2. German Consortium for Translational Cancer Research Partner Site Freiburg, German Cancer Research Center (DKFZ), Heidelberg, Germany. 3. Division of Phoniatrics and Pediatric Audiology, Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University, Munich, Germany. 4. Freiburg Institute for Musicians' Medicine, Freiburg University Medical Center, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
Abstract
PURPOSE: The temporal resolution of the MRI acquisition is intrinsically limited by the duration of the spatial encoding, which is typically on the order of milliseconds. Faster motion such as the vibration of the vocal folds during phonation cannot be imaged with conventional MRI as this would require sampling frequencies in the kilo-Hertz range. Here, a faster MRI acquisition strategy is presented that encodes a 1D periodic motion at a temporal resolution that is an order of magnitude higher compared to conventional MRI. METHODS: The proposed method encodes the position of an object moving along 1 dimension by applying very short phase encoding gradients along the same direction. This reduces the temporal resolution from the repetition time (TR) to the duration of the phase encoding gradients, which in this work was well below 1 ms. The technique is applied to the vocal fold oscillations and the position of the vocal folds is measured simultaneously using electroglottography (EGG). Simulations of the point spread function for regular encoding and the proposed method are performed as well. RESULTS: With this new phase, encoding strategy oscillations of the human vocal folds up to a frequency of 145 Hz could be dynamically imaged at 10 images per cycle. Simulations show the advantage of this method over conventional imaging of fast moving objects. CONCLUSION: A new method for MR imaging of fast moving spins is presented allowing a temporal resolution below 1 ms at a spatial resolution below 1 mm, circumventing TR as the limit for temporal resolution.
PURPOSE: The temporal resolution of the MRI acquisition is intrinsically limited by the duration of the spatial encoding, which is typically on the order of milliseconds. Faster motion such as the vibration of the vocal folds during phonation cannot be imaged with conventional MRI as this would require sampling frequencies in the kilo-Hertz range. Here, a faster MRI acquisition strategy is presented that encodes a 1D periodic motion at a temporal resolution that is an order of magnitude higher compared to conventional MRI. METHODS: The proposed method encodes the position of an object moving along 1 dimension by applying very short phase encoding gradients along the same direction. This reduces the temporal resolution from the repetition time (TR) to the duration of the phase encoding gradients, which in this work was well below 1 ms. The technique is applied to the vocal fold oscillations and the position of the vocal folds is measured simultaneously using electroglottography (EGG). Simulations of the point spread function for regular encoding and the proposed method are performed as well. RESULTS: With this new phase, encoding strategy oscillations of the human vocal folds up to a frequency of 145 Hz could be dynamically imaged at 10 images per cycle. Simulations show the advantage of this method over conventional imaging of fast moving objects. CONCLUSION: A new method for MR imaging of fast moving spins is presented allowing a temporal resolution below 1 ms at a spatial resolution below 1 mm, circumventing TR as the limit for temporal resolution.
Authors: Johannes Fischer; Ali Caglar Özen; Serhat Ilbey; Louisa Traser; Matthias Echternach; Bernhard Richter; Michael Bock Journal: MAGMA Date: 2021-09-20 Impact factor: 2.310
Authors: Peter Birkholz; Steffen Kürbis; Simon Stone; Patrick Häsner; Rémi Blandin; Mario Fleischer Journal: Sci Data Date: 2020-08-05 Impact factor: 6.444