The Value Of Multiple Sequence MRI To Detect Gallstones And Correlation Between Metal Compositions And MRI Feature

[Objective]This study intend to choose optimal MRI sequences in order to improve the the detection of gallstones, to analyse the features of different type of gallstones. Secondly, to measure the metallic contents of gallstones by chemical methods, to correlate these contents with the features of MRI, to evaluate the possibility of gallstones classification and the feasibility to analyze chemical composition in vivo.[Materials and Methods]There were 30 patients with gollstones enrolled in the study, MR Imaging was performed before surgery on a 1.5T scanner (Tiwn-speed Infinity With Excite II). Two conventional MR sequences, that is single-shot fast spin-echo T2-weighted imaging with fat saturation (FSE-FS T2WI) and in-phase fast spoiled gradient-echo T₁-weighted imaging (FSPGR T₁WI) were used. The 3D fast spoiled gradient-scho T₁-weighted imaging with fat saturation(3D-FSPGR-FS T₁WI) and fast imaging employing steady-state acquisition (FIESTA) were obtained as well. The type of gallstones were classfied by postopretive macroscopy. The detection rate of different sequences were compared and blind trial was applied. Characteristics of MR images of gallstones in different subtyps were observed and recorded. The average signalintensity were measured and the signal was corrected with that of spleen to explore the feasibility of classifying. Secondly, the samples in Phantom study were scanned with the same methods. To analyze the influence of water on gallstones, the ratioes of the signal intensity between stone specimens and Phantom Model was calculated and compared both prior and post drying. The contents of metallic elements (Ca Na Cu Fe) was measured by method of flame atomic obsorption spectrum. The signal intensity of gallstone specimens were correlated with whose metal contents, the correlative coefficient and regression equation were calculated.[Result]Thirty patients were divided into two groups, pigment gallstone (n=16) and cholesterol gallstone (n=14).Stones were classified into four types according to their signal intensity and homogeneity compared to that of peripheral bile juice on MRI, that is, homogenous high signal intensity, homogenous low signal intensity, mixed high signal intensity, mixed low signal intensity, and isointense. On 3D-FSPGR-FS TjWI, two of sixteen pigment gallstone presented with homogenous high signal, thirty cases with mixed high signal, and one case with isointense. On FSPGR TjWI, two cases presented with homogenous high signal, seven cases with mixed high signal, six cases with isointense, and one case with mixed low signal. However, most of the pigment gallstone showed homogenous or mixed low signal on FIESTA and FSE-FS T2WI, and few presented with isointense. Most of the cholesterol gallstone appeared as homogenous or mixed low signal on all MRI sequences, and few showed isointense. The detection rate of gallstones was 93.33% and 96.67% in 3D-FSPGR-FS TiWI and FIESTA. The corrected average signal intensity of the pigment gallstone on all 3D-FSPGR-FS TiWL FIESTA and FSPGR TjWI were statistically different from that of the cholesterol gallstone.After analysing of the stones specimens, a statistically different of the signalintensity ratioes between fresh and dry pigment gallstone on 3D-FSPGR-FS T]W1, FIESTA and FSPGR TiWI was demonstrated. For the cholesterol gallstones, the signal intensity ratio was different between fresh and dry specimens on FIESTA. Mental contents in both the pigment gallstones and cholesterol gallstones were measured by means of flame atomic absorption spectrum. Mental content (sum of the Ca, Na, Cu, and Fe) per piece weight was statistically different between 16 cases of pigment gallstone and 14 cases of cholesterol gallstone. Signal intensities of all stones specimens on 3D-FSPGR-FS TjWI were positive related to the mental contents (r=0.668).[Conclusion]3D-FSPGR-FS TiWI and FIESTA sequences are sensitive to detect gallstones. On 3D-FSPGR-FS TiWI, most of the pigment gallstones presented with specific high or mixed high signal intensity, but cholesterol gallstone presented with low or mixed low signal intensity. According to comparison of MRI signal intensity prior and post drying and correlation between MRI signal intensity and metal contents, the signal intensity differences between pigment gallstone and cholesterol gallstone on 3D-FSPGR-FS TiWI and FSPGR TjWI are related to the metal contents, especially calcium. And water molecules might also have critical effect on the difference of MRI signal intensity. So the application of 3D-FSPGR-FS TiWI and FIESTA sequences on diagnosis of gallstones clinically, especially the former, could not only improve the detection rate of stone, but also help to classify of gallstones.[ The creative points] In the research we've found several creative pointsas followed:1. The detection rate of gallstones was statistically higher in 3D-FSPGR-FS TiWI and FIESTA.2. On 3D-FSPGR-FS TiWI, most of pigment gallstone presented with specifichigh or mixed high signal intensity, but cholesterol gallstone presented with low or mixed low signal intensity. Therefore, we can sort gallstones according it.3. It is the first attempt in China that examining gallstone specimens before and after dryness by means of MRI. Pigment gallstone show specific high signal intensity, on 3D-FSPGR-FS TiWI, water molecules had substantiated with necessary effects.4. Measuring the component of metal in pigment gallstones and cholesterol gallstones through flame atomic absorption spectrum method and studying its relativity with MRI signal intensity have also been performed for the first time in China as well as in the world. We've proved that he component of metal is statistically different between pigment gallstone and cholesterol gallstone. Signal intensities of all stone specimens on 3D-FSPGR-FS TiWI are positively related to their metal contents.