| Part I Alterations of Pancreatic Signals on MR Images Associated with Diabetes Purpose:To analyze the pancreatic signal alterations on MR images associated with diabetes.Materials and Methods:This retrospective study was approved by the local Ethics Committee,and informed consent was waived.Abdominal MR images of 17 diabetic patients and 17 patients without diabetes were analyzed.The signal intensity values of the pancreas,liver,spleen,and left paraspinal muscle were measured on T2-weighted fat saturated,T1-weighted in phase,T1-weighted out of phase,water and fat images.Signal intensity ratios(SIRs)of pancreas to liver,spleen,and muscle and fat content of pancreas,liver,spleen,and muscle were calculated and then compared between diabetes and controls by independent samples t-test or Mann-Whitney test.Results:The SIRs of pancreas to liver,spleen and muscle showed no significant difference between diabetes and controls on T2-weighted fat saturated,Tl-weighted in phase,Tl-weighted out of phase,and water images(P>0.05).The mean SIR of pancreas to muscle on fat images of diabetes was significantly higher than that of controls(2.9341 ± 1.2354,2.1074 ± 0.7080,P=0.0421).Fat contents of pancreas and liver of diabetes were significantly higher than those of controls(0.1424±0.0513,0.0982±0.0311,P=0.0048;0.0865±0.0536,0.0465±0.0272,P=0.0125),while fat contents of spleen and muscle showed no significant difference(P>0.05).Conclusion:Pancreatic signals of diabetes show no significant alterations on T2-weighted fat saturated,T1-weighted in phase,T1-weighted out of phase,and water images.The SIR of pancreas to muscle on fat images and quantification of fat revealed elevated pancreatic fat content of diabetic patients.Part Ⅱ Quantification of Pancreatic T2*Values:influence of Region and Glucose DysregulationPurpose:To evaluate the differences in T2*values between pancreatic head,body and tail,and the impact of glucose dysregulation.Materials and Methods:This study was approved by the local Ethics Committee,and informed consent was obtained from all subjects.A multiple gradient recalled echo sequence was performed on a 3.0T MR scanner in 11 patients with diabetes and 16 normal controls.The T2*values of the pancreatic head,body and tail were obtained.The differences in T2*values between different regions were analyzed with repeated measures analysis of variance.The T2*values were compared between the diabetes and the controls by independent samples t-test.The repeatability of the pancreatic T2*measurements was assessed by calculating the intraclass correlation coefficient(ICC)and coefficient of variation(CV).Results:In the control group,the average T2*value of the pancreas was 31.51±3.43 ms.There was a significant difference in the T2*values of the three different anatomical regions(P=0.0010),and T2*value of pancreatic heads was significantly higher than that of pancreatic tails(P=0.0043).The average T2*value of the pancreas in the diabetic group was 28.70±4.23 ms,and there was no significant difference in T2*values between the three different anatomical regions(P=0.0776).The T2*values of global pancreas,pancreatic bodies and tails in the diabetic group was slightly smaller than those of the control group(P=0.0691,0.1020,0.1268).The T2*values in the pancreatic head of the diabetic group were significantly lower than those in the control group(P=0.0235).Pancreatic T2*measurements showed good repeatability(all ICC>0.95,CV<2.1%).Conclusion:The T2*values showed a decreasing trend from pancreatic head to pancreatic tail in the normal pancreas.The T2*values of the pancreas of diabetic patients were reduced,and this change was more obvious in the pancreatic head.Part Ⅲ Functional MRI of Human Pancreas Using BOLD Contrast:Responses Following Glucose IngestionPurpose:To evaluate the response of the pancreas to glucose ingestion in healthy volunteers by blood oxygenation level-dependent(BOLD)magnetic resonance imaging(MRI).Materials and Methods:This study was approved by the local Ethics Committee,and informed consent was obtained from all subjects.A multiple gradient recalled echo(mGRE)sequence was performed on a 3.0T MR scanner in 12 healthy volunteers before and after glucose or water ingestion.Pancreatic T2*values were calculated from it at each time point,and changes following stimulation were analyzed using summary measures.The valley values and times were compared between the glucose and water ingestion by paired samples t-test.The repeatability of the pancreatic T2*measurements was assessed by calculating the intraclass correlation coefficient(ICC)and coefficient of variation(CV).Results:Pancreatic T2*measurements showed good repeatability(all ICC>0.75).CV for the six baseline acquisitions was 2.74±0.97%,indicating a 5.37%measurement error.A transient but significant decrease(-6.88±1.01%,P value,0.0005-0.0467)in the pancreatic T2*values was observed within 5 minutes after glucose ingestion,rather than water consumption.Compared to water,glucose ingestion induced earlier(valley times:3.46 ± 3.22 vs.7.75±4.09 min,P=0.0006)and remarkable pancreatic T2*decrease(valley values:-15.33±5.90%vs.-6.88 ± 3.11%,P=0.0006).Conclusion:BOLD MRI enabled noninvasive quantification of pancreatic T2*changes during glucose stimulation.Glucose ingestion resulted in a rapid and significant pancreatic T2*decrease in healthy young volunteers. |
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