Spectral Subtraction Denoising (SSD) Improves Factor-3 GRAPPA 3T Lumbar MRI for Disc Herniation

  • Ildsa Maulidya Mar’athus Nasokha
  • Retno Wati
  • Mei Arnefia
DOI: https://doi.org/10.36079/lamintang.ijcims-0802.1047
Keywords: Computational Imaging, GRAPPA, Image Enhancement, Medical Image Processing, MRI Denoising

Abstract

Parallel imaging shortens lumbar MRI examinations but factor-3 GRAPPA produces spatially varying noise that can obscure clinically important structures. Evidence for a simple, reproducible spectral subtraction denoising approach in clinically acquired 3T lumbar examinations remains limited. This paired pretest-posttest study evaluated MATLAB-based spectral subtraction denoising (SSD) in 16 patients with clinically diagnosed lumbar disc herniation. Sagittal T2-weighted TSE-GRAPPA images acquired at acceleration factor 3 were processed by estimating the background-noise spectrum, directly subtracting it from the image spectrum, retaining the original phase, and applying an inverse Fourier transform. Signal-to-noise ratio (SNR) was measured in five anatomical regions, and two radiologists with more than five years of experience independently performed blinded five-point visual grading. Paired differences were assessed with the Wilcoxon signed-rank test; acceleration-factor comparisons used the Friedman test, and interobserver agreement used Cohen’s kappa. SSD increased SNR in every evaluated structure, with the largest absolute gains in the vertebral body (+1.81) and degenerated nucleus pulposus (+0.41). Overall visual information improved (p < 0.001); four of five structures improved significantly, whereas the vertebral body showed a ceiling effect (p = 0.236). Interobserver agreement increased from κ = 0.60 to κ = 0.72. The findings support SSD as a low-complexity post-processing option for preserving diagnostic visibility in accelerated lumbar MRI. Larger multicenter studies should compare SSD with modern learning-based denoisers and evaluate diagnostic accuracy.

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Author Biographies

Ildsa Maulidya Mar’athus Nasokha

Program of Radiology, Faculty of Health Sciences, Universitas ‘Aisyiyah Yogyakarta. Yogyakarta, Indonesia.

Retno Wati

Program of Radiology, Faculty of Health Sciences, Universitas ‘Aisyiyah Yogyakarta. Yogyakarta, Indonesia.

Mei Arnefia

Program of Radiology, Faculty of Health Sciences, Universitas ‘Aisyiyah Yogyakarta. Yogyakarta, Indonesia.

This is an open access article, licensed under CC-BY-SA

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2026-09-21
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How to Cite
[1]
I. M. Mar’athus Nasokha, R. Wati, and M. Arnefia, “Spectral Subtraction Denoising (SSD) Improves Factor-3 GRAPPA 3T Lumbar MRI for Disc Herniation”, International Journal of Clinical Inventions and Medical Sciences, vol. 8, no. 2, pp. 27-37, Sep. 2026.
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Vol 8 No 2: September 2026
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Articles

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