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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.
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Objective To assess the advantages of multi-source RF transmission(MT) for balanced fast field echo(BFFE) cardiac cine imaging.Methods Fifteen volunteers were scanned on a clinical 3.0 T MR system equipped with MT.Acquisition of B1 maps with and without MT were followed by axial and four chambers BFFE cine imaging for all subjects with different transmission modes[single source RF transmission (ST),MT and MT with allowable shortest TR(MTS)].The B1 field uniformity and contrast to noise ratio (CNR) were quantitatively analyzed.The B1 field uniformity was evaluated by the pixel values within the ROI and was compared with Student t test.CNR was defined as follows:(SIblood-SImyocardium)/ 0.5 ×(SDblood + SDmyocardium).CNR were tested with one-way ANOVA for three groups comparision and with LSD for inter-group comparison.Image qualities were blindly assessed by 2 readers with a 4-score scale.Global image quality scores were tested for statistical significance by using the nonparametric paired sample Friedman rank test for three groups and the Wilcoxon signed rank test for further inter-group comparison.The Kappa statistics was used to assess interreader agreement.Results B1 homogeneity was significantly improved for images with MT compared with ST under the condition of other parameters unchanged (t =21.632,P ＜0.01).In left ventricular,CNR of blood and myocardium was improved from 10.8 ±2.2 for ST to 14.4 ± 2.4 for MT and 14.1 ± 2.2 for MTS.In fight ventricular,it was improved from 7.7 ± 1.2 for ST to 12.2 ± 1.4 for MT and 12.0 ± 1.2 for MTS.The differences were statistically significant (F =11.617,61.472,P ＜0.01).The images of MT and MTS groups demonstrated greater CNR versus the ST images.There was no statistical difference between latter two groups.The image scores of Reader 1 and 2 were 4.60 ± 1.18 and 4.73 ± 1.10 for ST,6.53 ± 1.19 and 6.67 ± 1.29 for MT and 6.73 ± 1.03 and 6.73 ± 0.88 for MTS respectively.There were statistically differences among three groups (x2 =23.577,24.275,P ＜ 0.01).The image quality was improved on BFFE images using MT and MTS technology compared to ST technology,and there were also significant differences.The interreader agreement between two readers was good [K=0.643,0.722 and 0.814(P ＜0.05) for ST,MT,and MTS group respectively].Conclusions MT technology significantly improves B1 field uniformity,increases CNR and reduces artifact on BFFE cardiac cine images.The TR is decreased within the normal SAR ranges,and thus scanning speed is increased.
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Objective To examine supine fulcrum pressurized radiograph to predict spinal flexibility in adolescent idiopathic scoliosis (AIS). Methods 1. Empirical study: put two points (A and B) on one side of the plastic stick and one point on the other side ( C), pressurize on the plastic stick when point C is in the middle of A and B, and then measure the projection shifting of point A. Repeat the pressure test when the distance between A and C doubled. Analyze the effect of increasing distance on diminishing pressure. 2.Clinical study :45 patients ( 16 males and 29 females) underwent standing anteroposterior radiograph ,fulcrum lateral flexion radiograph, supine lateral flexion radiograph. The Cobb's angles were measured and the flexibility ratio was determined on preoperative fulcrum radiograph. Results (1) If the length of A and C was 25 cm, pressurize on point C, when pressure quantitative scale number located 1 scale and 2 scale of the rule, projection shifting of point A were 5 cm and 10 cm. If the length of A and C was 50 cm, pressurize on point C, when pressure quantitative scale number located 1 scale and 2 scale of the rule, projection shifting of point A were 8 cm and 15 cm. The longer the distance, the lesser the pressure force of plastics stick. (2)The Cobb angles and curve flexibility provided by fulcrum lateral flexion radiograph had significant difference from that provided by supine lateral flexion radiograph in male group and female group. Cobb angles of male group was 28. 6°± 4. 1 °, 16. 7°± 4. 6° respectively (t= 7. 438, P ＜ 0. 01 )and curve flexibility was 47. 6% ±8. 1% ,69. 4% ± 8. 5% respectively( t = 7. 438, P ＜ 0. 01 ). Cobb angles of female group was 24.5°± 2. 7°,12. 6°±2. 4° respectively(t = 17. 540,P ＜0. 01 )and curve flexibility was 53.4% ±5.2% ,76. 0% ±4. 7% respectively(t = 17. 54, P ＜ 0. 01 ). The flexibility of spinal main curve of female patients was obviously higher than male patients. Conclusions Supine fulcrum pressurized technique can make up for the insufficiency of supine lateral flexion technique, and provide a convenient, safe, precise and useful method for evaluation of spinal flexibility in AIS.