| Objective:To explore some sequence for better demonstration of parotid gland duct and peripheral branches by evaluating the quality of images of the MRS obtained by three different sequences on Siemens 3.0T unit. Also, to find out a optimized condition for increasing the showing of parotid gland duct system through dynamic MRS scan after oral administration of vitamin C.Methods:22 volunteers were performed magnetic resonance sialography with 2D-Half-Fourier Acquisition Single-Shot Turbo Spin-Echo Sequence(HASTE),2D-short TI inversion recovery turbo spin echo sequence(TIR) and 3D-Sampling Perfection with Application optimized Contrasts using different flip angle Evolutions sequence(SPACE), in turn. The images of 2D-HASTE and 2D-TIR sequences were obtained directly without on postprocessing by axial and oblique sagittal scan. The images of 3D-SPACE sequence were obtained by maximum intensity projection reconstruction using two-dimension original information. Ten seconds after citric acid stimulation, oblique sagittal acquisition was used to capture the image of the parotid gland ducts. Using 2D-HASTE sequencing with single-section acquisition of thick sections was repeated every 20 seconds (acquisition time:9 seconds, interval time:11 seconds). This dynamic procedure was conducted during the 2 minutes after stimulation. All of the images obtained by these three sequences were evaluated by two experienced radiologists. The rating standards are as follows:4 scores:the ducts of the parotid gland were demonstrated clearly accompany with good contrast of the image; 3 score:the ducts of the parotid gland were showed less clear accompany with less good contrast of the image; 2 score:the ducts of the parotid gland were showed blur accompany with bad contrast of the image; 1 score:the ducts of the parotid gland are demonstrated vaguely accompany with worse contrast of the image; 0 score: the ducts of the parotid gland are not precisely shown accompany with poor contrast of the image. For objective analysis, duct signal intensity and the corresponding background signal intensity in the phase-encoding direction were measured on the console, the contrast-to-noise ratio (CNR) and signal to noise ratio (SNR) was calculated as tube signal intensity minus background signal intensity divided by noise. Noise was defined as the standard deviation of the background signal intensity. All results are expressed as mean±SD. The result of various different visual scores, SNR, and CNR were analyzed by analysis of variance, ANOVA by SPSS(Version 13.0; SPSS Inc.).Significance was set at P values<0.05.Results:The scores of the MRS images obtained by these three sequences are as follows:main duct:3.42±0.87,3.72±0.57and3.78±0.54, respectively;:2.44±1.48; 2.58±1.36 and 2.61±1.70, respectively; the second or above branch:0.64±0.83, 0.47±1.13 and 1.31±1.69, respectively; total score:2.17±1.60,2.26±1.72 and 2.56±1.73.The SNR of these three sequences is 45.05±22.2,39.64±20.02 and 18.4±7.93, respectively; The CNR of these three sequences is 30.71±18.67, 34.86±20.19 and 16.38±7.81, respectively. The score of main duct after acid stimulation is 3.81±0.58,3.92±0.37,3.86±0.35,3.86±0.42,3.92±0.28 and 3.92±0.37, respectively; The score of the first branch after acid stimulation is 2.94±1.26,3.31±1.06,3.33±0.93,3.33±0.93,3.39±0.84 and 3.28±1.06, respectively; The score of the second branch 1.31±1.06,1.72±1.37,1.86±1.31, 1.89±1.14,2.08±1.25 and 2.06±1.19, respectively; The total score of parotid gland after acid stimulation is 2.69±1.44,2.98±1.37,3.02±1.27,3.03±1.21,3.13±1.17 and 3.08±1.22, respectively. No obvious difference is found in the three sequences regarding the score of main duct(P>0.05); Obvious difference is found in 2D-HASTE and 3D-SPACE sequence regarding the score of main duct (P<0.05), however, no obvious is found in (2D-HASTE vs 2D-TIR sequence) and(2D-TIR vs 3D-SPACE sequence) (P>0.05). Obvious difference is found in these three sequences regarding the score of the second branches (P< 0.05); Obvious difference is found in 2D-TIR and 3D-SPACE sequence regarding the score of the second branches (P<0.05), however, no obvious is found in (2D-HASTE vs 2D-TIR sequence) and(2D-HASTE vs 3D-SPACE sequence) (P>0.05). No obvious difference is found in the three sequences regarding the total score of the parotid gland (P>0.05); no obvious is found in (2D-HASTE vs 2D-TIR sequence), (2D-TIR vs 3D-SPACE sequence) and (2D-HASTE vs 2D-TIR) (P>0.05). Obvious difference is found in the three sequences about SNR of the MRS images(P<0.05); Obvious difference is found in 2D-HASTE vs 3D-SPACE sequence and 2D-TIR vs 3D-SPACE sequence(P＜0.05); however, no obvious difference is found in 2D-HASTE and 2D-TIR sequence(P>0.05); Obvious difference is found in the three sequences about CNR of the MRS images(P<0.05); Obvious difference is found in 2D-HASTE vs 3D-SPACE sequence and 2D-TIR vs 3D-SPACE sequence(P<0.05); no obvious difference is found between 2D-HASTE and 2D-TIR sequence. Obvious difference is found between before acid stimulation and after acid stimulation about the scores of main duct(P<0.05); no obvious difference is found in the six groups after acid stimulation. Obvious difference is found between before acid stimulation and about the scores of the first branches(P<0.05), except in before acid stimulation and 10s after acid stimulation; however, no obvious difference is found in the six groups after acid stimulation(P >0.05). Obvious difference is found between before acid stimulation and about the total score of the parotid gland(P＜0.05), except in before acid stimulation and 10s after acid stimulation(P>0.05); no obvious difference is found in the six groups after acid stimulation(P＞0.05), except in before acid stimulation vs 90s after acid stimulation and before acid stimulation vs 110s after acid stimulation. Obvious difference is found between before acid stimulation and about the scores of the second branches(P<0.05), except in before acid stimulation and 10s after acid stimulation(P>0.05); no obvious difference is found in the six groups after acid stimulation(P＞0.05), except in before acid stimulation vs 90s after acid stimulation and before acid stimulation vs 110s after acid stimulation(P＜0.05).Conclusion:Magnetic resonance sialography can show the duct system of the parotid gland. For Siemens 3.0T unit, no difference is found in showing main duct and the first branch in these three sequences. Although the SNR and CNR of 3D-SPACE sequence are lower than 2D-TIR sequence, it is better than the latter in demonstrating the second branches. The score of parotid gland duct was enhanced obviously after acid stimulation, especially for the second branches. Ninety seconds after acid stimulation is the best time demonstrating parotid gland duct system. |
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