Study on the improvement of image quality of 3.0 T fetal head MR scan by high dielectric constant / 中华放射学杂志

ABSTRACT

Objective:To explore the clinical application of a new high dielectric constant (HDC) to improve image quality in 3.0 T fetal head MR scans.Methods:Forty pregnant women who underwent 3.0 T fetal head MR examinations at the Drum Tower Hospital of Nanjing University School of Medicine from May to July 2021 were prospectively included and divided into a test group and a control group according to the placement and non-placement of HDC pads. After the scans were completed, qualitative and quantitative analysis were performed on the image quality of the two groups acquired in each case. Qualitative analysis: A 5-point scale was used to score the images of both groups by two diagnosticians and their scores were recorded. Quantitative analysis: Firstly, the overall radiofrequency specific absorption ratio (SAR) values of the two sets of fetal cranial cross-sectional scans of each pregnant woman were recorded separately, and the average rate of change of the overall SAR values was calculated; secondly, four regions of interest (ROIs) were placed on the standard level of the cross-sectional section of each fetal cranium (including the level of the basal ganglia region of the dorsal thalamus), and the minimum and maximum of the four ROIs of each of the two data sets were calculated separately. The ratio of minimum to maximum signal intensity (RSI), signal to noise ratio (SNR) and contrast to noise ratio (CNR) were calculated for each of the four ROIs in the two sets of data. Wilcoxon test was used to analyze the differences between the two groups of image quality score results; paired sample t-test or paired rank sum test was used to analyze the differences in SAR, RSI, SNR and CNR values between the two groups. Results:The fetal head image quality score was 4 (3, 4) in the test group and 3 (1, 4) in the control group, and the test group was significantly higher than the control group, with statistically significant difference ( Z=-3.62, P<0.01), and the images in the test group had a uniform signal compared with the control group, and none of them had significant artifacts. The results of quantitative analysis showed that the overall SAR value of the test group was significantly reduced, with a mean reduction rate of 32.1%, and the difference between the SAR values of the two groups was statistically significant ( Z=-2.78, P<0.01). The RSI, SNR and CNR in the frontal, temporal, thalamic and occipital lobes of the test group were all higher than those of the control group, and the differences were all statistically significant ( P<0.01). Conclusion:The HDC pads can significantly improve the image quality of 3.0 T fetal head imaging by reducing or eliminating the inhomogeneous artifacts in the RF field, which makes a good technical foundation for fetal head MR imaging.