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Objective To evaluate the advantages of MR LAVA multi-phase dynamic contrast enhancement in abdominal MRI.Methods 42 cases which clinically suspected liver lesions and 15 normal volunteers underwent MRI examination,including routine T_1WI and T_2WI scan,T_1W 2D and 3D FSPGR,LAV A multi-phase contrast enhancement.The detecting rates of 2D,3D and LAVA images were analysed and the signal noise ratio(SNR)of the liver and spleen was observed.Results 68 lesions were detected by LAVA sequence,the detecting rate was 100%,the accurate rate of diagnosis was 95.6%(65/68),while the detecting rates of the lesions were 91.2%(62/68)and 89.7%(61/68)with 3D T1W FSPGR and 2D T1W FSPGR,respectively,the accurate rates in diagnosing the lesions were 76.5%(52/68)and 70.6%(48/68)with 3D and 2D sequences,respectively.The SNR of liver,spleen of 15 normal volunteers were:29.68±2.31 in liver,36.21 ±3.67 in spleen at LAVA plain scan,46.21 ±5.32 in liver,58.75±4.68 in spleen at 2D T_1W FSPGR,19.79±2.23 in liver,23.63±2.14 in spleen at 3D T_1W FSPGR,41.75±5.13 in liver,57.96±6.13 in spleen at LAVA contrast enhancement,56.33±5.63 in liver,63.21±5.32 in spleen at 2D contrast enhancement,29.05±4.68 in liver,46.37±5.17 in spleen at 3D contrast enhancement sequence.Conclusion LAVA multi-phase dynamic contrast enhancement is more predominant than T1W 2D and 3D and 3D FSPGR in displaying the lesions and blood vessels of liver.
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Objective To assess the reliability of auto-shimming line width (LW) and water suppression rate (WS), and the correlation between them. Methods GE Signa Excite HD 3.0T system and eight-channel torso phased-array coils with PRESS sequence were performed in 38 volunteers. Liver spectra were collected with TR of 1500 ms, TE of 30 ms, VOI of 2 cm×2 cm×2 cm, NSA of 64 times. Spectroscopy routine auto-shimming pre-scanning program was executed and the values of LW and WS were recorded. Then another spectroscopy routine auto-shimming pre-scanning program was performed repeatedly and 38 groups of data were obtained totally. Intra-class correlation coefficients (ICC), coefficient of variation (CV) and significance test were conduced on 38 groups of LW and WS data. Spearman rank correlation analysis was used to assess the correlation of LW and WS. Results ①The ICC of LW and WS was 0.862 and 0.961 (both P＜0.0001), respectively, while the value of CV was 0.20, 0.18, 0.09 and 0.08, respectively. Significant difference was not observed; ②The value of correlation coefficient was -0.659, -0.485 (both P＜0.0001), respectively. Conclusion ①The reliability is excellent for in vivo liver 3.0T 1H-MRS and WS appears relatively stable; ②Indexes of LW correlate with WS moderately, and it seems the smaller the value of LW is, the easier to achieve higher WS.
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Objective To characterize the clinical factors which influence water suppression and auto-shimming line width for liver 3.0 T 1H-MRS.Methods Fifty-seven cases with liver 1H-MR spectroscopy(1H-MRS) were retrospectively studied, including chronic type B hepatitis (n=5), fatty liver (n=14), chronic type B hepatitis combining fatty liver (n=3) and normal situation (n=35).Independent t test was used to characterize the difference of general condition (height, weight, body mass index etc.) between different water suppression effect groups and between different shimming effect groups.Using Chi-square test to analyze whether water suppression rate and auto-shimming line width between fatty liver groups and non-fatty liver exist significance difference .Results By comparing WS ≥90% (n=47)group with WS < 90% (n=10) group, the former showed smaller average height[(164.7±8.0) and (170.5±3.7) cm respectively], weight[(61.8±10.4) and (73.4±5.4) kg respectively], BMI [(22.7±3.2) and (25.2±1.3)kg/m2 respectively]and LW[(17.7±3.7)and(24.6±6.3) Hz respectively]than the latter (t=-3.488,-3.415,-4.002 and-3.327, P < 0.05).By comparing LW 20 Hz (n=41) group with LW 20 Hz (n=16) group, the former showed better water suppression rate [(93.0±2.7)% and (86.1±8.5)% respectively]than the latter(t=3.213,P <0.05), whereas larger weight[(62.2±11.6) and (68.1±6.1)kg respectively]and BMI[(22.8±3.4) and (24.2±1.9)kg/m2 respectively](t=-2.516,-2.024,P <0.05).LW≤20 Hz in the fatty liver and non-fatty liver group was 7/17 and 34/40, respectively (X2=11.347, P < 0.05).WS < 90% in the fatty liver and non-fatty liver group was 10/17 and 0/44, respectively (X2=28.536, P < 0.05) .Conclusion Hepatic steatosis exerts an adverse effect in water suppression and shimming.
ABSTRACT
Objective To characterize the effect of the ~1H-MRS scan parametem, including the type of coil, TE,NSA and VOI, on shimming, water suppression, spectral signal to noise ratio(SNR)and the stability of the baseline of liver in vivo. Methods ~1H-MRS of liver in vivo was performed prospectively on GE Signa Excite HD 3.0 T system in 46 volunteers. Point-resolred spectroscopy(PRESS)sequence with built-in body coil and eight-channel torso phased-array coils was applied. After the localized scan,the first PRESS sequence with a TR of 1500 ms,TE of 30 ms. VOI of 2 cm×2 cm×2 cm and NSA of 64 times was acquired using eight-channel torso phased-array coils.(The first PRESS sequence parametem was deemed as A).Then,the sequence was repeated with alteration of the three parameters including the type of coil,TE and size of VOI.(Changed parameters deem as B).The data were analyzed with the Wilcoxon matched pairs signed test.0 mark:A is similar to B,1 mark:A better than B,-1 mark:A worse than B.Results SNR(-1 mark 0 pair,0 mark 1 pair,1 mark 10 pair,Z=-3.162,P=0.002)was better in data(n=11)with eight-channel torso phased-array coils(A)than that with the built-in body coil(B),but the autoshimming line width with eight-channel torso phased-array coils were inferior to those with built-in body coil (-1 mark 8 pair,0 mark 2 pair,1 mark 1 pair,Z=-2.511,P=0.012).SNR was better in data(n=13)with TE of 30 ms(A)than that at the sequence with TE of 90 ms(B)(-1 mark 2 pair,0 mark 0 pair,1 mark 11 pair,Z=-2.496,P=0.013).whereas baseline stability was,poorer in the former(-1 mark 10 pair,0 mark 2 pair,1 mark 1 pair,Z=-2.333,P=0.020).SNR at the sequence(n=10)with VOI of 2 cm×2 cm×3 cm(B)was better(-1 mark 6 pair,0 mark 4 pair,1 mark 0 pair,Z=-2.449,P=0.014)than that at the sequence(n=29)with VOI of 2 cm ×2 cm × 2 cm(A),but poorer(-1 mark 0 pair,0 mark 5 pair,1 mark 5 pair,Z=-2.041,P=0.041)auto-shimming line width was shown. By comparison the sequences with NSA of 128 times(B)and NSA of 64 times(A),the former could provide better spectrum SNR(-1 mark 21 pair,0 mark 7 pair,1 mark 1 pair,Z=-4.264,P=0.000).Conclusion It is more easy to achieve a homogeneous bo magnetic field using a small size of VOI and builtin body coli.The sequence with VOI of 2 cm ×2 cm ×3 cm.NSA of 128 times is recommended for clinical use. Increase VOI and NSA are helpful to improve SNR. Longer TE is helpful to improve baseline stability.