title: Physiology recording with magnetic field probes for fMRI denoising.
abstract: Physiological noise originating in cardiovascular and respiratory processes is a substantial confound in BOLD fMRI. When unaccounted for it reduces the temporal SNR and causes error in inferred brain activity and connectivity. Physiology correction typically relies on auxiliary measurements with peripheral devices such as ECG, pulse oximeters, and breathing belts. These require direct skin contact or at least a tight fit, impairing subject comfort and adding to the setup time. In this work, we explore a touch-free alternative for physiology recording, using magnetic detection with NMR field probes. Placed close to the chest such probes offer high sensitivity to cardiovascular and respiratory dynamics without mechanical contact. This is demonstrated by physiology regression in a typical fMRI scenario at 7T, including validation against standard devices. The study confirms essentially equivalent performance of noise models based on conventional recordings and on field probes. It is shown that the field probes may be positioned in the subject's back such that they could be readily integrated in the patient table.
authors.affiliation: Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Gloriastrasse 35, 8092 Zurich, Switzerland. Electronic address: gross@biomed.ee.ethz.ch.
authors.forename: Simon
authors.initials: S
authors.lastname: Gross
authors.affiliation: Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Gloriastrasse 35, 8092 Zurich, Switzerland. Electronic address: vionnet@biomed.ee.ethz.ch.
authors.forename: Laetitia
authors.initials: L
authors.lastname: Vionnet
authors.affiliation: Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Gloriastrasse 35, 8092 Zurich, Switzerland; Translational Neuromodeling Unit (TNU), Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Wilfriedstrasse 6, 8032 Zurich, Switzerland. Electronic address: kasper@biomed.ee.ethz.ch.
authors.forename: Lars
authors.initials: L
authors.lastname: Kasper
authors.affiliation: Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Gloriastrasse 35, 8092 Zurich, Switzerland. Electronic address: dietrich@biomed.ee.ethz.ch.
authors.forename: Benjamin E
authors.initials: BE
authors.lastname: Dietrich
authors.affiliation: Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Gloriastrasse 35, 8092 Zurich, Switzerland. Electronic address: pruessmann@biomed.ee.ethz.ch.
authors.forename: Klaas P
authors.initials: KP
authors.lastname: Pruessmann
mesh_terms: D000328:Adult; D059907:Functional Neuroimaging / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008991:Monitoring, Physiologic / Q000295:instrumentation*; D012815:Signal Processing, Computer-Assisted
keywords: Breathing recording; Cardiac recording; NMR field probes; Physiological noise correction; Physiology tracking; RETROICOR