Dynamic Contrast-enhanced CT's Characteristics Of Experimental Model Of Blunt Hepatic Injury In Rabbits

Objective: To evaluate the feasibility of the rabbit blunt hepatic injury(BHI) model for imaging study,and to analyze its imaging features with spiral computed tomography.Materials and methods:40 New Zealand white rabbits,the model of blunt hepatic injury in rallits was established with a steel ball falling down to the xiphoid process of animals. The CT scans were obtained by using GE Hispeed 2i spiral computed tomography. Plain CT scan and dynamic contrast-enhanced CT scan were performed. Scanning was performed with auralvein contrast enhancement by using a power-injected bolus with Iohexol based on the dosage 1.5ml/kg, injected at a rate of 0.3 ml/sec. A uniphasic injection was used, arterial phase with a scanning delay of 8-10 seconds from the time of initiation of the intravenous injection of contrast material, portal phase with 35-40 seconds,equilibrium phase with 120-150 seconds.CT was performed from the diaphragmatic dome to the pelvis.The first part:three experienced radiologists independently make three serial read of each of 40 rabbits liver images.To calculate the Kappa value of intra-and inter-rater reliability.The second part: the CT images were reviewed and interpreted by means of consensus by this three radiologists on the basis of a predetermined protocol without knowledge of the laparotomy or pathophyposition. This observations were included①Thenumber of the lesions detected on CT;②The size of the lesion;③Hepatic capsular laceration;④Active hemorrhage;⑤Major hepatic venous injury;⑥Hemoperitoneum;⑦A grading of the lesion by using the CT grades of injury severity for blunt hepatic trauma established by Mirvis et al;⑧The histopathological features of rabbit hepatic injury.The CT findings were compared with those of exploratory laparotomy and pathophyposition.Results:1. Radiologists1',2'and 3'plain kappa value of the first and the second,the first and the third,the second and the third are 0.5862,0.5333,0.5532;0.3622,0.5299,0.5467;0.4839,0.5394,0.5200 respectively; enhanced kappa value are 1.000,0.6538,0.6538;0.6538,0.6538,1.0000;0.7857,0.6538,0.6983 respectively.The plain kappa value for Radiologists 1,2,1,3,2,3are 0.4255,0.2713,0.2636;enhanced kappa value are 1.000,0.6538,0.6538..2. Thirty-one cases developed hepatic parenchymal laceration,among which 18 were multiple lacerations.There were 16 cases of traumatic hematoma,among which 7 were subcapsular and 9 were intraparenchymal,and 17 cases of hepatic capsular laceration.six cases showed active bleeding,while five cases had injury of major hepatic veins.16 cases showed peritoned fluid(blood) collection.3.Hepatic injuries were classified as CT gradeⅠin five rabbits, gradeⅡin fifteen rabbits,gradeⅢin nine rabbits,gradeⅣin five rabbits,gradeⅤin one rabbits and gradeⅥzero.Conlusion:1.The model of blunt hepatic injury is simple to be operated,physics-paramete easy to be controlled.The impact location is accurate and the reliability is very good.It is also a suitable model for imaging study.2. Contrast-enhanced CT is currently the diagnostic modality of choice for the evaluation of blunt liver trauma in hemodynamically stable patients.3. The major CT features of blunt liver trauma are lacerations, subcapsular and parenchymal hematomas, active hemorrhage, juxtahepatic venous injuries, hepatic capsular laceration and hemoperitoneum.4.The CT-based grading system reflective of the extent of parenchymal liver damage.The CT scan is very valuable in defining liver trauma, in judging trauma degree;also in estimating bleeding amount of abdominal cavity and in selecting proper mode of therapy.