Managing acoustic noise within MRI: A qualitative interview study among Swedish radiographers

INTRODUCTION

Acoustic noise from magnetic resonance imaging (MRI) can cause hearing loss and needs to be mitigated to ensure the safety of patients and personnel. Capturing MR personnel's insights is crucial for guiding the development and future applications of noise-reduction technology. This study aimed to explore how MR radiographers manage acoustic noise in clinical MR settings.

METHODS

Using a qualitative design, we conducted semi-structured individual interviews with fifteen MR radiographers from fifteen hospitals around Sweden. We focused on the clinical implications of participants' noise management, using an interpretive description approach. We also identified sociotechnical interactions between People, Environment, Tools, and Tasks (PETT) by adopting a Human Factors/Ergonomics framework. Interview data were analyzed inductively with thematic analysis (Braun and Clarke).

RESULTS

The analysis generated three main themes regarding MR radiographers' noise management: (I) Navigating Occupational Noise: Risk Management and Adaptation; (II) Protecting the Patient and Serving the Exam, and (III) Establishing a Safe Healthcare Environment with Organizational Support.

CONCLUSION

This study offers insights into radiographers' experiences of managing acoustic noise within MRI, and the associated challenges. Radiographers have adopted multiple strategies to protect patients and themselves from adverse noise-related effects. However, they require tools and support to manage this effectively, suggesting a need for organizations to adopt more proactive, holistic approaches to safety initiatives.

IMPLICATIONS FOR PRACTICE

The radiographers stressed the importance of a soundproofed work environment to minimize occupational adverse health effects and preserve work performance. They acknowledge noise as a common contributor to patient distress and discomfort. Providing options like earplugs, headphones, mold putty, software-optimized "quiet" sequences, and patient information were important tools. Fostering a safety culture requires proactive safety efforts and support from colleagues and management.

Functional ultrasound reveals effects of MRI acoustic noise on brain function

Loud acoustic noise from the scanner during functional magnetic resonance imaging (fMRI) can affect functional connectivity (FC) observed in the resting state, but the exact effect of the MRI acoustic noise on resting state FC is not well understood. Functional ultrasound (fUS) is a neuroimaging method that visualizes brain activity based on relative cerebral blood volume (rCBV), a similar neurovascular coupling response to that measured by fMRI, but without the audible acoustic noise. In this study, we investigated the effects of different acoustic noise levels (silent, 80 dB, and 110 dB) on FC by measuring resting state fUS (rsfUS) in awake mice in an environment similar to fMRI measurement. Then, we compared the results to those of resting state fMRI (rsfMRI) conducted using an 11.7 Tesla scanner. RsfUS experiments revealed a significant reduction in FC between the retrosplenial dysgranular and auditory cortexes (0.56 ± 0.07 at silence vs 0.05 ± 0.05 at 110 dB, p=.01) and a significant increase in FC anticorrelation between the infralimbic and motor cortexes (-0.21 ± 0.08 at silence vs -0.47 ± 0.04 at 110 dB, p=.017) as acoustic noise increased from silence to 80 dB and 110 dB, with increased consistency of FC patterns between rsfUS and rsfMRI being found with the louder noise conditions. Event-related auditory stimulation experiments using fUS showed strong positive rCBV changes (16.5% ± 2.9% at 110 dB) in the auditory cortex, and negative rCBV changes (-6.7% ± 0.8% at 110 dB) in the motor cortex, both being constituents of the brain network that was altered by the presence of acoustic noise in the resting state experiments. Anticorrelation between constituent brain regions of the default mode network (such as the infralimbic cortex) and those of task-positive sensorimotor networks (such as the motor cortex) is known to be an important feature of brain network antagonism, and has been studied as a biological marker of brain disfunction and disease. This study suggests that attention should be paid to the acoustic noise level when using rsfMRI to evaluate the anticorrelation between the default mode network and task-positive sensorimotor network.

Effect of acoustic noise reduction technology on image quality: a multivendor study

The purpose of this study was to clarify the appropriate use of a combination of pulse sequences and acoustic noise reduction technology in general-purpose brain magnetic resonance imaging. Five pulse sequences commonly used in brain magnetic resonance imaging examinations-turbo spin-echo T2-weighted imaging, T1-weighted fluid-attenuated inversion recovery, T2-weighted fluid-attenuated inversion recovery, diffusion-weighted imaging, and magnetic resonance angiography-were performed on healthy participants at three vendors where acoustic noise reduction technology was available. The results showed that acoustic noise reduction technology reduced sound pressure levels and altered image quality in all pulse sequences across all vendors' magnetic resonance imaging scanners. Although T2-weighted imaging and T1-weighted fluid-attenuated inversion recovery resulted in little image quality degradation, T2-weighted fluid-attenuated inversion recovery, diffusion-weighted imaging, and magnetic resonance angiography had significant image degradation. Therefore, acoustic noise reduction technology should be used with caution.

Resting State Network Connectivity is attenuated by fMRI acoustic noise

INTRODUCTION

During the past decades there has been an increasing interest in tracking brain network fluctuations in health and disease by means of resting state functional magnetic resonance imaging (rs-fMRI). Rs-fMRI however does not provide the ideal environmental setting, as participants are continuously exposed to noise generated by MRI coils during acquisition of Echo Planar Imaging (EPI). We investigated the effect of EPI noise on resting state activity and connectivity using magnetoencephalography (MEG), by reproducing the acoustic characteristics of rs-fMRI environment during the recordings. As compared to fMRI, MEG has little sensitivity to brain activity generated in deep brain structures, but has the advantage to capture both the dynamic of cortical magnetic oscillations with high temporal resolution and the slow magnetic fluctuations highly correlated with BOLD signal.

METHODS

Thirty healthy subjects were enrolled in a counterbalanced design study including three conditions: a) silent resting state (Silence), b) resting state upon EPI noise (fMRI), and c) resting state upon white noise (White). White noise was employed to test the specificity of fMRI noise effect. The amplitude envelope correlation (AEC) in alpha band measured the connectivity of seven Resting State Networks (RSN) of interest (default mode network, dorsal attention network, language, left and right auditory and left and right sensory-motor). Vigilance dynamic was estimated from power spectral activity.

RESULTS

fMRI and White acoustic noise consistently reduced connectivity of cortical networks. The effects were widespread, but noise and network specificities were also present. For fMRI noise, decreased connectivity was found in the right auditory and sensory-motor networks. Progressive increase of slow theta-delta activity related to drowsiness was found in all conditions, but was significantly higher for fMRI . Theta-delta significantly and positively correlated with variations of cortical connectivity.

DISCUSSION

rs-fMRI connectivity is biased by unavoidable environmental factors during scanning, which warrant more careful control and improved experimental designs. MEG is free from acoustic noise and allows a sensitive estimation of resting state connectivity in cortical areas. Although underutilized, MEG could overcome issues related to noise during fMRI, in particular when investigation of motor and auditory networks is needed.

Judgement of valence of musical sounds by hand and by heart, a machine learning paradigm for reading the heart

The intention of the experiment is to investigate whether different sounds have influence on heart signal features in the situation the observer is judging the different sounds as positive or negative. As the heart is under (para)sympathetic control of the nervous system this experiment could give information about the processing of sound stimuli beyond the conscious processing of the subject. As the nature of the influence on the heart signal is not known these signals are to be analysed with AI/machine learning techniques. Heart rate variability (HRV) is a variable derived from the R-R interval peaks of electrocardiogram which exposes the interplay between the sympathetic and parasympathetic nervous system. In addition to its uses as a diagnostic tool and an active part in the clinic and research domain, the HRV has been used to study the effects of sound and music on the heart response; among others, it was observed that heart rate is higher in response to exciting music compared with tranquilizing music while heart rate variability and its low-frequency and high-frequency power are reduced. Nevertheless, it is still unclear which musical element is related to the observed changes. Thus, this study assesses the effects of harmonic intervals and noise stimuli on the heart response by using machine learning. The results show that noises and harmonic intervals change heart activity in a distinct way; e.g., the ratio between the axis of the ellipse fitted in the Poincaré plot increased between harmonic intervals and noise exposition. Moreover, the frequency content of the stimuli produces different heart responses, both with noise and harmonic intervals. In the case of harmonic intervals, it is also interesting to note how the effect of consonance quality could be found in the heart response.

Qualitative and quantitative analysis of 3D T1 Silent imaging

PURPOSE

To compare brain magnetic resonance imaging (MRI) using T1 3D Silent and fast T1 3D Gradient-Echo (GRE) BRAin VOlume (known as BRAVO) sequences. The primary aim is to assess the quantitative and qualitative analysis of Silent and BRAVO images by the measurement of the contrast (C), the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR). The second aim is to estimate the subjective sound levels and the specific absorption rate (SAR).

METHODS

Twenty-two subjects had T1 3D Silent and T1 3D BRAVO sequences added to the standard MR examination. The qualitative analysis of the two sequences was performed by two radiologists independently. The quantitative analysis was performed by placing regions of interest on the cerebrospinal fluid, on the white and grey matter. The C, the CNR and the SNR were calculated for each sequence. After each T1-3D sequence, subjects gave a score rating to evaluate the acoustic noise. Finally, the SAR was evaluated by the digital imaging and communications in medicine (DICOM) tags.

RESULTS

The image quality scores obtained by the two radiologists were higher for BRAVO compared to the Silent. However, qualitatively, the Silent images were similar to BRAVO for diagnostic use. Quantitatively, CNR for GM-CSF was comparable in the two sequences and SNR in CSF was higher in Silent than BRAVO. The acoustic noise of Silent sequence was statistically lower compared with BRAVO. The maximum SAR measured was 1.4 W/kg.

CONCLUSIONS

3D T1 Silent can be a valid alternative technique to conventional BRAVO to reduce the acoustic noise preserving the diagnostic accuracy. However, radiologists preferred the conventional sequence to Silent.

Acoustic comfort depends on the psychological state of the individual

Recent studies have shown that comfort can be influenced more by psychological processes than from the characteristics of environmental stimulation. This is relevant for different industrial sectors, where comfort is defined only as a function of the intensity of external stimuli. In the present study, we measured physiological and psychological comfort during the exposure to four levels of acoustic noise [from 45 to 55 dB(A)] corresponding to different comfort classes inside a full-scale mock-up of a cruise ship cabin. We found an increase of psychological and physiological discomfort for higher noise intensities, but not for all the intensities defining the comfort classes. Furthermore, we found that negative psychological states determine a lower physiological sensitivity to acoustic noise variations compared to positive states. Our results show that, at normal/low intensities, psychological processes have a greater role in determining acoustic comfort when compared to the stimulus intensity. Practitioner Summary: This study shows that psychological factors can be more relevant in determining acoustic comfort inside a ship cabin than the intensity of acoustic stimulus itself. This finding suggests that the cruise industry should consider not only the engineering measurements when evaluating comfort on board, but also the passenger' psychological state. Abbreviations: AIC: akaike information criterion; CCT: colour correlated temperature; cd/m²: candela/square meters; df: degrees of freedom; F-test: Fisher's test; HF: high frequency; HR: heart rate; HRV: heart rate variability; HSV: hue saturation value; K: kelvin; LF: low frequency; LF/HF: low frequency to high frequency ratio; lme: linear mixed effects; ms: milliseconds; nu: normalized unit; p: p value; pNN50: percentage of adjacent pairs of normal to normal RR intervals differing by more than 50 milliseconds; r²: coefficient of determination; r_c: concordance correlation coefficient; RMSSD: square root of the mean normal to normal RR interval; SD: standard deviation; SDNN: standard deviation of normal to normal RR intervals; SEM: standard error of the mean; t-test: student's tests; χ²: chi-square test.

The Physics of Magnetic Resonance Imaging Safety

Magnetic resonance (MR) imaging relies on a strong static magnetic field in conjunction with careful orchestration of pulsed linear gradient magnetic fields and radiofrequency magnetic fields in order to generate images. The interaction of these fields with patients as well as materials with magnetic or conducting properties can be a source of risk in the MR environment. This article provides a basic review of the physical underpinnings of the primary risks in MR imaging to foster development of intuition with respect to both patient and risk management in the MR environment.

Acoustic sound-induced stress response of Nile tilapia (Oreochromis niloticus) to long-term underwater sound transmissions of urban and shipping noises

Human-made impacts on the acoustic environment from marine industries is becoming a more significant issue with increasing public concern of environmental consequences. Even though there are several reports with scientific evidences on harmful influences of anthropogenic underwater sounds on the aquatic ecosystem, most of the studies so far dealt with trigger effects of short term noise impacts on aquatic animals. In the present study, however, long-term experimentation was conducted with Nile tilapia (Oreochromis niloticus) in order to figure out how fish may respond to long-term exposure of underwater sounds and if the level of response may change (increase or decline) over time. A startle reflex as a sign of stress was seen immediately at the start of the playbacks of ship noise or urban sounds in this study. Peaks of elevated respiratory movements of ventilation (opercula beats and pectoral wing rates) retained high over the following 30 days of sound initiation and underwent a declining trend over the following 90 days of exposure. At the end of the 120-day study period, the lowered response of fish after long-term sound exposure is likely due to the increased tolerance of fish to human-generated underwater sounds of urban and shipping noises. Different than short-term noise impacts, information on long-term exposure of anthropogenic underwater sounds is important for environmental management and setting new regulations for the sustainable use of water resources in the world.

Silent susceptibility-weighted angiography to detect hemorrhagic lesions in the brain: a clinical and phantom study

PURPOSE

To compare the effectiveness of silent susceptibility-weighted angiography (sSWAN), a new imaging technique with lower acoustic noise, with conventional susceptibility-weighted angiography (cSWAN) in the detection of intracranial hemorrhagic lesions.

METHODS

We measured the acoustic and background noise during sSWAN and cSWAN imaging and calculated the contrast-to-noise ratio (CNR) of the phantom consisting of eight chambers with different concentrations of superparamagnetic iron oxide. In the clinical study, we calculated the CNRs of hemorrhagic lesions in 15 patients and evaluated the images for conspicuity and artifact on each sequence and scored them on a 4-point scale. We also evaluated whether hypointense areas observed on sSWAN or cSWAN increased in size from those on T2*-weighted imaging (T2*-WI).

RESULTS

Acoustic noise for sSWAN (57.9 ± 0.32 dB [background noise 51.3 dB]) was significantly less than that for cSWAN (89.0 ± 0.22 dB [background noise 50.9 dB]). The CNRs of phantoms for sSWAN were slightly but not significantly lower than those for cSWAN (P = 0.18). The CNRs of hemorrhagic lesions did not show significant differences between sSWAN and cSWAN (P = 0.17). There were no significant differences between sSWAN and cSWAN with respect to the scores for conspicuity, artifact, and change in size of hypointense areas from T2*-WI.

CONCLUSION

sSWAN is equivalent to cSWAN with respect to the image quality for the detection of hemorrhagic lesions but has lower acoustic noise.

Evaluation of magnetic resonance imaging acoustic noise reduction technology by magnetic gradient waveform control

BACKGROUND

ComforTone is a noise reduction technology used in magnetic resonance imaging (MRI) systems; it suppresses acoustic noise by modifying pulse sequences, which appropriately changes the magnetic field gradient waveforms. Although ComforTone can be used to solve the acoustic noise problems that affect patients who are exposed to acoustic noise from MRI, to the best of our knowledge, the associated technical details have not been published and its effects on acoustic noise reduction remain unclear.

PURPOSE

To evaluate the efficacy of acoustic noise reduction and the impact of acoustic noise reduction technology involving magnetic field gradient waveform control on image quality.

POPULATION

The study included 18 healthy volunteers (11 males and 7 females; median age, 34 years; age range, 24-51 years).

FIELD STRENGTH

1.5 T Philips Ingenia using a SENSE head-spine coil.

ASSESSMENT

The sound pressure level (SPL) and 1/3 octave spectra of MRI acoustic noise with the human head positioned in the iso-center of the MRI system were measured for five different pulse sequences used in clinical MRI. This subjective evaluation of noise included 18 healthy volunteers. The degree of discomfort experienced by the subjects was measured using a visual analog scale. The image quality was assessed objectively and subjectively. For objective assessment, signal-to-noise ratio (SNR) and contrast-to -noise ratio (CNR) of diffusion-weighted images were measured; for subjective assessment, visual evaluation was performed by two radiologists.

STATISTICAL TESTS

Data were analyzed using Welch's t-test, and a p value <0.05 defined significance.

RESULTS

ComforTone could recognize a decrease in sound pressure, and the sound pressure of the acute high-frequency portion of the auditory characteristics was reduced. As reported by the subjects, discomfort caused by the sound pressure was significantly alleviated with ComforTone (p < 0.01). The sound pressure reduction in the high-frequency region with high audibility characteristics was recognized by ComforTone. The visual evaluation of the image quality of the diffusion-weighted images revealed that although there was no difference between SNR and CNR, the image quality was reduced by distortion artifacts.

DATA CONCLUSION

ComforTone reduced the SPL in the frequency range where auditory characteristics were sensitive, suggesting that ComforTone was useful for auditory protection and alleviation of discomfort in patients undergoing MRI. However, because magnetic field gradient waveform control is involved, such noise-reducing techniques should be used by considering their possible influence on the image quality.

Accelerated silent echo-planar imaging

PURPOSE

The standard approach to Echo-Planar Imaging (EPI) is to use trapezoidal readout (RO) gradients with blipped phase-encoding (PE) gradients. Sinusoidal RO gradients with constant PE gradients can reduce acoustic noise. However, this sequence, originally introduced by Mansfield et al., constitutes major challenges for Cartesian parallel imaging techniques. In this study two alternatives to reconstruct a non-blipped EPI are proposed and evaluated.

THEORY AND METHODS

The first method separates the acquired k-space data into odd and even echoes and applies Cartesian GRAPPA separately to each partial data set. Afterwards, the resulting reconstructed data sets for each echo are summed in image space. In the second method, an iterative parallel-imaging algorithm is used to reconstruct images from the highly non-Cartesian data samples.

RESULTS

Compared to blipped-EPI, the first method reduces image SNR depending on the acceleration factor between 11% and 60%. For an acceleration factor of 3 folding artefacts appear. The second method produces slight fold-over artefacts although image SNR is on the same level as the blipped approach.

CONCLUSION

In this study, we have introduced two new approaches to EPI that allow the use of Cartesian parallel imaging in conjunction with continuous data sampling. In addition to providing a reduction in acoustic noise compared to the standard blipped PE EPI sequence, the proposed techniques improve sampling efficiency, resulting in a reduction of the echo-spacing. Of the two methods, the second approach, based on an iterative image reconstruction, provides higher SNR, but requires a longer reconstruction time.

Active control of acoustics-caused nano-vibration in atomic force microscope imaging

In this paper, we propose a finite-impulse-response (FIR)-based feedforward control approach to mitigate the acoustic-caused probe vibration during atomic force microscope (AFM) imaging. Compensation for the acoustic-caused probe vibration is important, as environmental disturbances including acoustic noise induce nano-scale probe vibration, directly affecting the AFM performance in applications such as imaging, nanomechanical characterization, and nanomanipulation. Although conventional passive noise cancellation apparatus has been employed, limitation exists, and residual noise still persists. Thus, a FIR-based active feedforward control approach is developed, by exploring a data-driven approach to account for the vibrational dynamics of the probe caused by the environmental acoustic noise in the controller design. An experimental implementation in AFM imaging application is presented and discussed to illustrate the proposed technique. Experimental results show that the FIR-based feedforward control is promising to not only complement, but also alleviate the limitations of passive noise control in AFM operations.

BIAS: A Regional Management of Underwater Sound in the Baltic Sea

Management of the impact of underwater sound is an emerging concern worldwide. Several countries are in the process of implementing regulatory legislations. In Europe, the Marine Strategy Framework Directive was launched in 2008. This framework addresses noise impacts and the recommendation is to deal with it on a regional level. The Baltic Sea is a semienclosed area with nine states bordering the sea. The number of ships is one of the highest in Europe. Furthermore, the number of ships is estimated to double by 2030. Undoubtedly, due to the unbound character of noise, an efficient management of sound in the Baltic Sea must be done on a regional scale. In line with the European Union directive, the Baltic Sea Information on the Acoustic Soundscape (BIAS) project was established to implement Descriptor 11 of the Marine Strategy Framework Directive in the Baltic Sea region. BIAS will develop tools, standards, and methodologies that will allow for cross-border handling of data and results, measure sound in 40 locations for 1 year, establish a seasonal soundscape map by combining measured sound with advanced three-dimensional modeling, and, finally, establish standards for measuring continuous sound. Results from the first phase of BIAS are presented here, with an emphasis on standards and soundscape mapping as well as the challenges related to regional handling.

A novel acoustically quiet coil for neonatal MRI system

MRI acoustic exposure has the potential to elicit physiological distress and impact development in preterm and term infants. To mitigate this risk, a novel acoustically quiet coil was developed to reduce the sound pressure level experienced by neonates during MR procedures. The new coil has a conventional high-pass birdcage RF design, but is built on a framework of sound abating material. We evaluated the acoustic and MR imaging performance of the quiet coil and a conventional body coil on two small footprint NICU MRI systems. Sound pressure level and frequency response measurements were made for six standard clinical MR imaging protocols. The average sound pressure level, reported for all six imaging pulse sequences, was 82.2 dBA for the acoustically quiet coil, and 91.1 dBA for the conventional body coil. The sound pressure level values measured for the acoustically quiet coil were consistently lower, 9 dBA (range 6-10 dBA) quieter on average. The acoustic frequency response of the two coils showed a similar harmonic profile for all imaging sequences. However, the amplitude was lower for the quiet coil, by as much as 20 dBA.

Acoustic noise improves motor learning in spontaneously hypertensive rats, a rat model of attention deficit hyperactivity disorder

The spontaneously hypertensive (SH) rat model of ADHD displays impaired motor learning. We used this characteristic to study if the recently described acoustic noise benefit in learning in children with ADHD is also observed in the SH rat model. SH rats and a Wistar control strain were trained in skilled reach and rotarod running under either ambient noise or in 75 dBA white noise. In other animals the effect of methylphenidate (MPH) on motor learning was assessed with the same paradigms. To determine if acoustic noise influenced spontaneous motor activity, the effect of acoustic noise was also determined in the open field activity paradigm. We confirm impaired motor learning in the SH rat compared to Wistar SCA controls. Acoustic noise restored motor learning in SH rats learning the Montoya reach test and the rotarod test, but had no influence on learning in Wistar rats. Noise had no effect on open field activity in SH rats, but increased corner time in Wistar. MPH completely restored rotarod learning and performance but did not improve skilled reach in the SH rat. It is suggested that the acoustic noise benefit previously reported in children with ADHD is shared by the SH rat model of ADHD, and the effect is in the same range as that of stimulant treatment. Acoustic noise may be useful as a non-pharmacological alternative to stimulant medication in the treatment of ADHD.

Reverberation clutter from subcutaneous tissue layers: simulation and in vivo demonstrations

The degradation of ultrasonic image quality is typically attributed to aberration and reverberation. Although the sources and impact of aberration are well understood, very little is known about the source and impact of image degradation caused by reverberation. Reverberation is typically associated with multiple reflections at two interfaces along the same propagation path, as with the arterial wall or a metal sphere. However, the reverberation that results in image degradation includes more complex interaction between the propagating wave and the tissue. Simulations of wave propagation in realistic and simplified models of the abdominal wall are used to illustrate the characteristics of coherent and diffuse clutter generated by reverberation. In the realistic models, diffuse reverberation clutter is divided into that originating from the tissue interfaces and that originating from sub-resolution diffuse scatterers. In the simplified models, the magnitude of the reverberation clutter is observed as angle and density of the connective tissue are altered. The results suggest that multi-path scattering from the connective tissue/fat interfaces is a dominant component of reverberation clutter. Diffuse reverberation clutter is maximal when the connective tissue is near normal to the beam direction and increases with the density of connective tissue layers at these large angles. The presence of a thick fascial or fibrous layer at the distal boundary of the abdominal wall magnifies the amount of reverberation clutter. The simulations also illustrate that compression of the abdominal layer, a technique often used to mitigate clutter in overweight and obese patients, increases the decay of reverberation clutter with depth. In addition, rotation of the transducer or steering of the beam with respect to highly reflecting boundaries can reduce coherent clutter and transform it to diffuse clutter, which can be further reduced using coherence-based beamforming techniques. In vivo images of the human bladder illustrate some of the reverberation effects observed in simulation.