| Objective An augmented reality navigation system was designed and developed to assist accurate ablation of liver tumors,and its feasibility and practical value were verified.Materials and methods The system integrates image segmentation,3D reconstruction,image registration,location and tracking,respiratory motion compensation and AR display.Through an abdominal phantom experiment and animal experiment of 7 dogs,the navigation accuracy and visualization effect of the system are verified.In phantom experiment,the navigation system was used to simulate the liver tumor puncture,and the navigation accuracy,including target location error,user manual error and target registration error,was calculated.In the canine animal experiment,a comparative study was carried out between navigation puncture and routine CT-guided steeper puncture of canine liver implant tumors.The differences of puncture time,puncture times,CT scanning times,total radiation dose and puncture accuracy between the two methods were recorded and compared.Results In phantom experiment,30 puncture times were completed under the navigation system.Target registration error(TRE)is(4.24 ±1.63)mm,user error(UE)is(3.32± 1.19)mm,target positioning error(TPE)is(4.24 ± 1.65)mm.A single sample t-test was used to analyze the critical value of TPE(4.24 ±1.65)mm)and 5mm(P <0.05).The results showed that the navigation error of AR was small,and its accuracy met the requirements of percutaneous puncture.Single factor(ANOVA)variance analysis was used to study the effects of three tracks on UE with no significantdifference(P = 0.116)and the effect of operator’s skills and paths on TPE was studied.There was no significant difference between TPEs(P = 0.288,0.304)..By means of paired t-test analysis,there was no significant difference in the effect of two different operators on UE(t = 1.335,P = 0.203).In the canine experiment,14 artificial implanted tumors were successfully implanted into the liver of 7 Beagle dogs,and the navigation puncture and the routine CT-guided steep hand puncture were performed on 14 liver tumors,respectively.In two ways,The puncture time ratio(t = 6.936,P=0.000 < 0.01),the puncture times ratio(t = 6.450,P = 0.000 < 0.01),CT scanning times ratio(t = 6.450,P= 0.000 < 0.01),the total radiation dose ratio(t=2.523,P=0.025<0.05),the precision ratio of puncture was(t = 3.315,P = 0.006 <0.01).In the aspect of augmented reality display,with the help of Microsoft HoloLens holographic glasses,the navigation system can realize the three-dimensional display effect,and the operator can obtain the "perspective" ability with the aid of the navigation system.Intuitively perceiving the relative position relationship between ablation needle and tumor is helpful to improve the accuracy of puncture.Conclusion In this study,the AR navigation system meets the requirements of ideal navigation accuracy,effectively improves the puncture efficiency,reduces the puncture times,and reduces the CT scanning times.At the same time,it can realize "visualization" and real-time positioning navigation of puncture operation.It is an effective auxiliary method to guide liver tumor puncture and ablation by CT. |
