Relating Doses Of Contrast Angent Administered To Time-intensity Curve And Semi-quantitative Parameters On DCE-MRI

Objective To explore the changes of the types of time-signal intensity curve(TIC) and semi-quantitative parameters on DCE-MRI related to different doses of contrast agents in the Walker256murine breast tumor model.And to confirm appropriate parameters which should be used to evaluate responses to neoadjuvant chemotherapy. Mater i a I s and Methods Establish a stable Walker256breast cancer model in rats,12model rats were divided into three groups randomly,4in each group.Then we made routine scan the model rats using Bruker Pharmascan7T MRI scanner (for small animals).And we made dynamic contrast enhanced imaging before and after the injection of contrast medium(repeated twice before the injection,and39times after the injection; contrast medium doses for three groups are0.2mmol/Kg,0.3mmol/Kg and0.5mmol/Kg). Observe findings of the breast tumors on routine MR. Delineate the TICs in each group.Survey the TIC type and calculate all the semi-quantitative parameters(early enhancement parameters:Efirst and Vfirst; peak parameters:SImax> Tpea^Emax and Vmax;wash out parameters:Ewash、Vwash、SER and Slopewash)/According to whether the data is conformed to the homogeneity of variance,we used analysis of variance(One-way ANOVA) and nonparametric rank test(Kruskal-Wallis H test) to compare differences in SIpre and semi-quantitative parameters during thress groups.Results (1)The Walker256breast tumors showed iso-intense signal on T1WI,and hyper-intecse signal or mixed signal(hyper-intecse signal based) on T2WI. After injecting the tumors were enhanced.The types of TIC in all the12tumors were Illpattern. TIC types were not influenced by contrast agent doses,the tumors’curves all showed the outflow type.(2)SIpre showed no statistical differences between the three dose groups(.F=0.720, P=0.513).(3)Efirst and Vfirst showed statistical differences between the three dose groups(F=16.952, P=0.001; F=69.483, P=0.000).Camparing each two groups,there were statistical differences of Eflrst and Vfirst. Camparing dose group1(0.2mmol/Kg) to dose group2(0.3mmol/Kg) EfirstCP=0.010), Vfirst(P=0.000); camparing dose group1(0.2mmol/Kg) to dose group3(0.5mmol/Kg) Efirst(P=0.000), Vfirst(P=0.000); camparing dose group 2(0.3mmol/Kg) to dose group3(0.5mmol/Kg) Efirst(P=0.031), Vfirst(P=0.002).(4)SImax and Emax showed statistical differences between the three dose groups(F=54.838, P=0.000; F=12.510, P=0.003). Camparing each two groups,there were statistical differences of SImax(P=0.035; P=0.000; P=0.000).As for Emax,there were statistical differences between dose groupl(0.2mmol/Kg) and dose group3(0.5mmol/Kg),and also between dose group2(0.3mmol/Kg) and dose group3(0.5mmol/Kg)(P=0.001; P=0.005). There were no statistical differences between dose group1(0.2mmol/Kg) and dose group2(0.3mmol/Kg) of Emax(P=0.334). Tpeak and Vmax showed no statistical differences between the three dose groups(F=0.065, P=0.937; F=1.505, P=0.273).(5) Ewash and SER showed statistical differences between the three dose groups(F=5.248, P=0.031; F=9.733, P=0.006). As for Ewash,there was statistical differences between dose group1(0.2mmol/Kg) and dose group3(0.5mmol/Kg)(P=0.010),and there were no statistical differences between other two groups. As for SER,there were statistical differences between dose group1(0.2mmol/Kg) and dose group3(0.5mmol/Kg) and also between dose group2(0.3mmol/Kg) and dose group3(0.5mmol/Kg)(P=0.002; P=0.041). There was no statistical difference between group1(0.2mmol/Kg) and group2(0.3mmol/Kg) in SER.Vwash showed no statistical differences between the three dose groups(x2=1.423, P=0.319). Mean signal intensity of each group was highly negative linear correlated with scan times after the peak(r=-0.972, P=0.000; r=-0.971, P=0.000; r=-0.989, P=0.000). Slopewash showed no statistical differences between the three dose groups(F=1.654, P=0.244).Conclusion Injection doses of contrast agent didn’t change the type of TIC,Tpeak,Vmax,Vwash and Slopewash. They are very important for evaluating responses to neoadjuvant chemotherapy,so that we could compare the datas of DCE among different medical centers.