Qualitative and quantitative analysis of 3D T1 Silent imaging

Abstract

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.

Keywords: Acoustic noise; Magnetic resonance imaging; Neuroimaging; Silent scan; Zero time of echo.