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

Abstract

ObjectivesTo 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 methodsThirty-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.ResultsPeak 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.ConclusionsSequence-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.

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

“…5). 4,13,25 For qualitative assessment, three radiologists (reader 1, 2, and 3, with 21, 8, and 9 years of clinical MRI experience, respectively) blindly evaluated the images on separate workstations. To minimize bias, the three T2W TSE sequences were coded and renamed, and the image order was randomized for each subject.…”

“…There have mainly been two approaches to restrict sound propagation within an MR system: modifying the hardware and optimizing the software. 1,4,13,14 When remodeling the hardware, the focus has been to minimize the mechanical forces, thus reducing vibrations and sound pressure waves (eg embedding the gradient coils in a vacuum chamber or dampening mechanical components). 1,4,14,15 However, this is complex, often costly, and, in some cases, even reduces the gradient efficiency.…”

“…This enables removing unnecessary gradient activity while maintaining the net effect on the magnetization, thus optimizing the gradient waveform regardless of timing constraints. 4,13,17 The QS algorithm can be applied to spin echo (SE), turbo spin echo (TSE), diffusion weighted imaging, and gradient echo (GRE) with T1 contrast, or susceptibility weighted imaging. Still, several pulse sequences do not have the option, eg T2*-weighted GRE.…”

“…Several authors have studied gradient waveform optimization for noise reduction and its effect on image quality, 4,13,14,[22][23][24][25] yet, there is limited knowledge about gradient field exposure in this context. 18 Previous ANR research has been focused on head MRI.…”

Editorial for “Maintaining Image Quality While Reducing Acoustic Noise and Switched Gradient Field Exposure During Lumbar Magnetic Resonance Imaging”

“…1,2 MRI operating at 1.5 T generates a noise level of nearly 120 dB (A), which is equivalent to the noise level produced by a jet engine. 3 The acoustic noise produced during scanning is strongly related to patient discomfort and fear, which can cause image degradation as a result of patient movement. In addition, in patients with dementia, consciousness disturbances, or claustrophobia, as well as in children, the loud noise that is produced is considered to be an obstacle to performing MRI.…”