Acoustic noise reduction in T 1- and proton-density-weighted turbo spin-echo imaging

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.

Maintaining Image Quality While Reducing Acoustic Noise and Switched Gradient Field Exposure During Lumbar MRI

BACKGROUND

MR-generated acoustic noise can contribute to patient discomfort and potentially be harmful. One way to reduce this noise is by altering the gradient output and/or waveform using software optimization. Such modifications might influence image quality and switched gradient field exposure, and different techniques appear to affect sound pressure levels (SPLs) to various degrees.

PURPOSE

To evaluate SPLs, image quality, switched gradient field exposure, and participants' perceived noise levels during two different acoustic noise reduction (ANR) techniques, Quiet Suite (QS) and Whisper Mode (WM), and to compare them with conventional T2-weighted turbo spin echo (T2W TSE) of the lumbar spine.

DESIGN

Prospective.

SUBJECTS

Forty adults referred for lumbar MRI.

FIELD STRENGTH/SEQUENCE

Conventional T2W TSE, T2W TSE with QS, and T2W TSE with WM were acquired at 1.5 T.

ASSESSMENT

Peak SPL (A-weighted decibels, dBA), perceived noise levels (Borg CR10®-scale), signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), three radiologists' qualitative assessments in image quality on an ordinal scale 1-4, switched gradient field exposure (% general public), and gradient currents were measured. Interobserver reliability was reported as percentage agreement.

STATISTICAL TESTS

Repeated measures ANOVA, Friedman's ANOVA, and Wilcoxon's Signed-Rank Test for acoustic noise measurements and image quality assessments.

RESULTS

Mean peak SPLs were 89.9 dBA, 74.3 dBA, and 78.8 dBA for conventional, QS, and WM, respectively (P < 0.05). Participants perceived QS as the quietest and conventional as the loudest sequence (P < 0.05). No qualitative differences in image quality were seen (P > 0.05), although QS showed significantly improved SNR and CNR (P < 0.05). Switched gradient field exposure was reduced by 66% and 48% for QS and WM, respectively.

DATA CONCLUSION

Without degrading image quality, both QS and WM are viable ANR techniques in lumbar T2W TSE. QS provided the lowest SPL, the lowest gradient field exposure and was perceived as the most silent among the three sequences.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY STAGE: 5.

MRI acoustic noise-modulated computer animations for patient distraction and entertainment with application in pediatric psychiatric patients

PURPOSE

To reduce patient anxiety caused by the MRI scanner acoustic noise.

MATERIAL AND METHODS

We developed a simple and low-cost system for patient distraction using visual computer animations that were synchronized to the MRI scanner's acoustic noise during the MRI exam. The system was implemented on a 3T MRI system and tested in 28 pediatric patients with bipolar disorder. The patients were randomized to receive noise-synchronized animations in the form of abstract animations in addition to music (n = 13, F/M = 6/7, age = 10.9 ± 2.5 years) or, as a control, receive only music (n = 15, F/M = 7/8, age = 11.6 ± 2.3 years). After completion of the scans, all subjects answered a questionnaire about their scan experience and the perceived scan duration.

RESULTS

The scan duration with multisensory input (animations and music) was perceived to be ~15% shorter than in the control group (43 min vs. 50 min, P < 0.05). However, the overall scan experience was scored less favorably (3.9 vs. 4.6 in the control group, P < 0.04).

CONCLUSIONS

This simple system provided patient distraction and entertainment leading to perceived shorter scan times, but the provided visualization with abstract animations was not favored by this patient cohort.

Software-based noise reduction in cranial magnetic resonance imaging: Influence on image quality

Objectives

To investigate acoustic noise reduction, image quality and white matter lesion detection rates of cranial magnetic resonance imaging (MRI) scans acquired with and without sequence-based acoustic noise reduction software.

Material and methods

Thirty-one patients, including 18 men and 13 women, with a mean age of 58.3±14.5 years underwent cranial MRI. A fluid-attenuated inversion recovery (FLAIR) sequence was acquired with and without acoustic noise reduction using the Quiet Suite (QS) software (Siemens Healthcare). During data acquisition, peak sound pressure levels were measured with a sound level meter (Testo, Typ 815). In addition, two observers assessed subjective image quality for both sequences using a five-point scale (1 very good—5 inadequate). Signal-to-noise ratio (SNR) was measured for both sequences in the following regions: white matter, gray matter, and cerebrospinal fluid. Furthermore, lesion detection rates in white matter pathologies were evaluated by two observers for both sequences. Acoustic noise, image quality including SNR and white matter lesion detection rates were compared using the Mann-Whitney-U-test.

Results

Peak sound pressure levels were slightly but significantly reduced using QS, P≤0.017. Effective sound pressure, measured in Pascal, was decreased by 19.7%. There was no significant difference in subjective image quality between FLAIR sequences acquired without/with QS: observer 1: 2.03/2.07, P = 0.730; observer 2: 1.98/2.10, P = 0.362. In addition, SNR was significantly increased in white matter, P≤0.001, and gray matter, P = 0.006, using QS. The lesion detection rates did not decline utilizing QS: observer 1: P = 0.944 observer 2: P = 0.952.

Conclusions

Sequence-based noise reduction software such as QS can significantly reduce peak sound pressure levels, without a loss of subjective image quality and increase SNR at constant lesion detection rates.