Objective To choose optimal concentration and volume of Gd-DTPA solution as a oral gastrointestinal negative contrast agent for MRCP.To evaluate the role of Gd-DTPA solution in improving image quality of MRCP.Methods In vitro experiment:Gd-DTPA solution was made with different concentrations.T1WI,T2WI,two-dimensional single slice fast spin echo sequence and three-dimensional half-fourier acquisition single-shot fast spin echo sequence were performed to measure the signal intensity of these contrast agents respectively,so Gd-DTPA solution with the optimal concentration can be decided as oral negative gastrointestinal contrast agent on MRCP.Clinical study:The Gd-DTPA solution with optimal concentration and volume was regarded as an oral negative gastrointestinal contrast agent of MRCP.Twenty-four patients were performed with MRCP before and after (5--10 minutes and 10--15 minutes)administration of oral negative gastrointestinal contrast agent and image quality was analyzed.Statistical analysis was performed using analysis of variance with SPSS 10.0.Results When the concentration of Gd-DTPA solution was ≤0.01 mol/L,the contrast agent was hyperintense on T1WI.On T2WI,when the concentration was ≥0.015 mol/L,it was as hypointense as basic ground; On 2D FSE MRCP images,controls were hyperintense and the contrast agent with concentration ranging from 0.0025 mol/L to 0.03 moL/L was hypointense.On 3D HEAST MRCP image,controls were hyperintense and when the eoncentration of Gd-DTPA was ≥0.01 mol,the contrast agent was hypointense.The Gd-DTPA solution with the concentration of 0.01 mol/L and the volume of 100 ml was chosen as MRCP oral negative gastrointestinal contrast agent.On MRCP images after oral administration of the contrast agent,in 10-15 minutes,the average grade scores within 24 patients of the intrahepatic bile duct,the common hepatic bile duct,the gall bladder,the common bile duct and pancreatic duct(the average grade scores were respectively 3.63,3.46,3.08,3.71,3.87,3.88,3.79,3.71,3.50) were somehow higher than in 5--10 minutes(the average grade scores were respectively 3.54,3.46,3.00,3.79,3.96,3.87,3.71,3.67,3.54),but showed no statistical difference(P>0.05).However,the scores of the third branch of the intrahepatic bile duct,the common bile duct and pancreatic duct after oral administration of the contrast agent were significantly higher than those before administration of oral contrast agent(the average grade scores were respectively 2.79,3.71,3.50,3.42,3.25) (F=4.36,4.75,7.86,8.05,7.55,P<0.05).Conclusion The0.01 mol/L oral Gd-DTPA contrast agent is optimal because it can suppress the high signal from the retention of the stomach and duodenum completely.It can be regarded as MRCP oral negative gastrointestinal contrast agent.After oral contrast administration,the image quality of MRCP is improved obviously and the pancreaticobiliary tree is clear 5-10 minutes later.