Acoustic Noise Concerns in Functional Magnetic Resonance Imaging

Department of Radiology, Erasmus Medical Center Rotterdam, Rotterdam, The Netherlands.
Human Brain Mapping (Impact Factor: 5.97). 11/2003; 20(3):123-41. DOI: 10.1002/hbm.10134
Source: PubMed


Magnetic resonance (MR) acoustic scanner noise may negatively affect the performance of functional magnetic resonance imaging (fMRI), a problem that worsens at the higher field strengths proposed to enhance fMRI. We present an overview of the current knowledge on the effects of confounding acoustic MR noise in fMRI experiments. The principles and effectiveness of various methods to reduce acoustic noise in fMRI are discussed, practical considerations are addressed and recommendations are made. Hum. Brain Mapping 20:123–141, 2003.

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    • "Cognitive neuroscientists who study how the brain perceives spoken language desire a quiet imaging technique that can record brain function noninvasively and provide reliable results. Such measurements have proven challenging to collect using functional magnetic resonance imaging (fMRI) due to the substantial acoustic noise associated with echoplanar imaging (Foster et al., 2000; McJury and Shellock, 2000; Moelker and Pattynama, 2003; Price et al., 2001; Ravicz et al., 2000). "
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    ABSTRACT: The functional neuroanatomy of speech processing has been investigated using positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) for more than 20 years. However, these approaches have relatively poor temporal resolution and/or challenges of acoustic contamination due to the constraints of echoplanar fMRI. Furthermore, these methods are contraindicated because of safety concerns in longitudinal studies and research with children (PET) or in studies of patients with metal implants (fMRI). High-density diffuse optical tomography (HD-DOT) permits presenting speech in a quiet acoustic environment, has excellent temporal resolution relative to the hemodynamic response, and provides noninvasive and metal-compatible imaging. However, the performance of HD-DOT in imaging the brain regions involved in speech processing is not fully established. In the current study, we use an auditory sentence comprehension task to evaluate the ability of HD-DOT to map the cortical networks supporting speech processes. Using sentences with two levels of linguistic complexity, along with a control condition consisting of unintelligible noise-vocoded speech, we recovered a hierarchical organization of the speech network that matches the results of previous fMRI studies. Specifically, hearing intelligible speech resulted in increased activity in bilateral temporal cortex and left frontal cortex, with syntactically complex speech leading to additional activity in left posterior temporal cortex and left inferior frontal gyrus. These results demonstrate the feasibility of using HD-DOT to map spatially distributed brain networks supporting higher-order cognitive faculties such as spoken language. Copyright © 2015. Published by Elsevier Inc.
    Full-text · Article · May 2015 · NeuroImage
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    • "In the context of functional magnetic resonance imaging (fMRI), the loud acoustic scanner noise (ASN) that is emitted by the read-out gradient switches of echo-planar imaging sequences is a major confounding factor that becomes increasingly serious as available magnetic field strengths get higher (Foster et al., 2000; Moelker and Pattynama, 2003). Apart from evoking activation in the auditory cortex (Bandettini et al., 1998; Elliott et al., 1999; Hall et al., 2000), ASN has also been shown to influence task-related activity in non-auditory brain regions related to vision (Zhang et al., 2005), motion (Fuchino et al., 2006), imagery (Mazard et al., 2002), nociception (Boyle et al., 2006), emotion (Skouras et al., 2013), attention (Novitski et al., 2001), working memory (Novitski et al., 2003; Haller et al., 2005; Tomasi et al., 2005), and the default mode network (Gaab et al., 2008). "
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    ABSTRACT: Numerous studies on the tonotopic organisation of auditory cortex in humans have employed a wide range of neuroimaging protocols to assess cortical frequency tuning. In the present functional magnetic resonance imaging (fMRI) study, we made a systematic comparison between acquisition protocols with variable levels of interference from acoustic scanner noise. Using sweep stimuli to evoke travelling waves of activation, we measured sound-evoked response signals using sparse, clustered, and continuous imaging protocols that were characterised by inter-scan intervals of 8.8, 2.2, or 0.0s, respectively. With regard to sensitivity to sound-evoked activation, the sparse and clustered protocols performed similarly, and both detected more activation than the continuous method. Qualitatively, tonotopic maps in activated areas proved highly similar, in the sense that the overall pattern of tonotopic gradients was reproducible across all three protocols. However, quantitatively, we observed substantial reductions in response amplitudes to moderately low stimulus frequencies that coincided with regions of strong energy in the scanner noise spectrum for the clustered and continuous protocols compared to the sparse protocol. At the same time, extreme frequencies became over-represented for these two protocols, and high best frequencies became relatively more abundant. Our results indicate that although all three scanning protocols are suitable to determine the layout of tonotopic fields, an exact quantitative assessment of the representation of various sound frequencies is substantially confounded by the presence of scanner noise. In addition, we noticed anomalous signal dynamics in response to our travelling wave paradigm that suggest that the assessment of frequency-dependent tuning is non-trivially influenced by time-dependent (hemo)dynamics when using sweep stimuli.
    Full-text · Article · Jul 2014 · NeuroImage
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    • "While the period between acquisitions is quieter , it would be remiss to think of it as silent. Ambient noise related to ventilation, cryogen pumping, and monitoring equipment are all present during this period and, without effective acoustic shielding , could also affect fMRI data (Moelker and Pattynama, 2003). "
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    ABSTRACT: When conducting auditory investigations using functional magnetic resonance imaging (fMRI), there are inherent potential confounds that need to be considered. Traditional continuous fMRI acquisition methods produce sounds >90dB which compete with stimuli or produce neural activation masking evoked activity. Sparse scanning methods insert a period of reduced MRI-related noise, between image acquisitions, in which a stimulus can be presented without competition. In this study, we compared sparse and continuous scanning methods to identify the optimal approach to investigate acoustically-evoked cortical, thalamic and midbrain activity in the cat. Using a 7T magnet, we presented broadband noise, 10kHz tones, or 0.5kHz tones in a block design, interleaved with blocks in which no stimulus was presented. Continuous scanning resulted in larger clusters of activation and more peak voxels within the auditory cortex. However, no significant activation was observed within the thalamus. Also, there was no significant difference found, between continuous or sparse scanning, in activations of midbrain structures. Higher magnitude activations were identified in auditory cortex compared to the midbrain using both continuous and sparse scanning. These results indicate that continuous scanning is the preferred method for investigations of auditory cortex in the cat using fMRI. Also, choice of method for future investigations of midbrain activity should be driven by other experimental factors, such as stimulus intensity and task performance during scanning.
    Full-text · Article · Jan 2014 · Journal of Neuroscience Methods
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