| Chapter I Choose the most suitable contrast agentconcentrationObjective: To find the most suitable concentration of the contrast agentat different tube voltage conditions,when performe the pulmonaryangiography on rabbits.Materials and Methods:Ten normal rabbits,male and femaleunlimitied,are divided into A and B groups randomly.Take the iohexol300andnormal saline,in volume ratios of1:0,1:3,1:6,1:10,to formulate to obtain300mg/ml、75mg/ml、42.8mg/ml、27.3mg/ml of the contrast agent.Everyrabbit were carried out at different times for the four concentrations ofpulmonary CT angiography scan,rabbits of group A were under the scanningcondition of120KV,50mAs,and every rabbit of group B were scanned by thecondition of80KV,50mAs.Bolus tracking was used when CTPA wasperformed.CT values of the pulmonary artery were measured in differentconcentrations of the contrast agent and get the average value.Results: The average CT values from high to low concentration of therabbits’ pulmonary trunk in group A were608±32（HU）、243±28（HU）、179±10（HU）、146±16（HU）, The average CT values from high to lowconcentration of the rabbits’ pulmonary trunk in group B were869±54（HU）、445±61（HU）、231±18（HU）、175±9（HU）。Conclusion:1.Under the condition of120KV,50mAs, using a1:3ratio of theconcentration is better,,under conditions of80KV,50mAs,using theconcentration ratio of1:6is better.2.With the same concentration of contrast agent,the CT value of therabbits’ pulmonary trunk in group B is higher than that in group A. Chapter II Parameter optimization of the reconstructedimages of different iterative strengthObjective: Parameter optimization and the pulmonary embolismdetection ability of the reconstructed images of different iterative strength.Materials and Methods:10healthy rabbits, weighing3.5kg-4kg, wereanesthetized by injection of a concentration of1%sodium pentobarbitalthrough the ear vein. After bundling fixed supine anesthetized rabbits,isolated jugular vein,and inserted a18G needle.5-10gelatin sponge emboliwith saline were pushed into jugular vein. All the rabbits were underwent theCT scan under the condition of80KV,50mAs, the contrast agentconcentration42.8mg/ml, the amount1.5ml/kg, injection rate of1ml/s,followed by injection of saline2ml/kg, injection rate,1.5ml/s, using a bolustraking technology. Images were reconstructed by iterative reconstruction.Iterative strength choose1-5,acquired five groups of images. Measure thenoise of the images,and calculate the SNR and CNR, and grade the images byscores，measure the CT values of the pulmonary artery of the different imagesconstructed by different strength.Rabbits were killed by overdose sodiumpentobarbital, lung tissues were cut in slices and find the location of theemboli. We use the SPSS13.0software to analyze the data of noise、SNR、CNR.We use the one-way analysis cariance to analyze the data after thenormality test and the homogeneity test for variance.The detection ability wascompared by the R×C Chi-square test.Results: The noise of images reconstructed by the strength from1-5were14.86±1.11、12.56±0.98、11.37±1.51、9.36±0.70、8.15±0.57，SNR were3.32±0.47、4.15±0.62、4.88±0.75、5.59±0.37、6.02±0.60， CNR were9.45±1.10、11.47±0.91、12.67±0.85、14.59±1.09、15.46±0.79，the scores were2.50±0.53、3.13±0.99、5.38±0.51、4.35±0.46、3.75±0.71，the CT values of the pulmonary artery were228±10HU,228±13HU，228±14HU,228±12HU,228±14HU,the data passed the normality test and the homogeneity testfor variance,the noise、SNR、CNR of the five groups is different.Thesensitivity of the pulmonary embolism detection of the images from1-5were88.9%、88.9%、92.5%、92.5%、88.9%，and the specificity were84.6%、84.6%、92.3%、92.3%、92.3%,the result of the R×C Chi-square test showedthat the detection ability of five groups is undifferent.Conculusion:1.Comprehensive analysis of image quality of the five groups, the imageof strength3is better.2.There is no difference between the detection ability of different strengthof iterative reconstruction. Chapter III The exploration of the detection ability of rabbits’pulmonary embolism under the condion of low tube voltage andlow concentration of contrast agent that conbined with iterativereconstructionObjective: To investigate the detection capabilities for pulmonaryembolism of the low-kV tube voltage and low concentrations of contrastagents combined with the iterative reconstruction technique.Materials and Methods: The study was approved by the animal ethicscommittee of Hebei Medical University.10healthy rabbits, weighing3.5kg-4kg, were anesthetized with a concentration of1%sodiumpentobarbital,3ml/kg. After separation of the right vena jugularis externa,insert a18G catheter in it,and inject the gelatin sponge emboli with a20mlinjection syringe. We performe the first scan on the a second-generation dual-source CT,under the scheme A of80KV,50mAs, using the contrast agentconcentration42.8mg/ml (using iohexol and saline according to the volumeratio of1:6mixture), the amount1.5ml/kg, injection rate1ml/s, followed byinjection of saline2ml/kg, injection rate,1.5ml/s. The CT scan was triggeredby a bolus-tracking technique, with the region of interest placed in thepulmonary trunk, and image acquisition started2seconds after the attenuationreached the predefined hreshold of100HU. Then thin layer of images werereconstructed with iterative reconstruction, to optimize the image quality.After two to four hours of the first scan,the second scan was performed, underthe scheme B of the scanning conditions120KV,50mAs, the contrast agentconcentration75mg/ml the amount1.5ml/kg, injection rate1ml/s, followedby injection of saline2ml/kg, injection rate,1.5ml/s, using a bolus trakingtechnology. CTDIvol、DLP of two schemes were recorded,and then work outthe ED. Subsequently rabbits were sacrificed, their lungs were removed andplaced in fixative. Pathologic slices were obtained at1-mm intervals, HEstaining, to verify the presence and location of pulmonary artery brancheswith and without emboli. Two physicians reviewed the CT images, and findthe locations and number of the emboli,discuss the result to get the sameanswer when their opinions were different. Finally, the pathology results as thegold standard, comparing the two scans for emboli detection capabilities.Calculate the corresponding sensitivity, specificity, positive predictive value(PPV), negative predictive value (NPV).Results:One died because of the overdose anesthesia,one died during theprocedure.8rabbits were left, a total of40lungs,pathology results showed thepresence of gelatin sponge emboli in27lobes. Under80KV,50mAsconditions, combined with iterative reconstruction technique,25lobes showedthe presence of gelatin sponge emboli.The sensitivity, specificity, positivepredictive value (PPV), negative predictive value (NPV) were92.5%(25/27),92.3%(12/13),96.1%(25/26),85.7%(12/14). Associated with thepathological findings of the κ value was0.639. Under120kv,50mAsconditions,26lobes showed the presence of gelatin sponge emboli., the sensitivity, specificity, positive predictive value (PPV), negative predictivevalue (NPV) were96.2%(26/27),92.3%(12/13),96.2%(26/27),92.3%(12/13). Associated with the pathological findings of the κ value was0.813.Conclusions:1.Gelatin sponge is a good kind of embolic agent when building a rabbit’spulmonary embolism model.2.The ED of the two schemes is differect.Compared to the scheme B（12kV）,the schemeA’s（80kV） ED discreased about60%.3. Compared to the normal concentration of contrast agent and normaltube voltage, the detection ability of rabbits’ pulmonary embolism under thecondion of low tube voltage and low concentration of contrast agent thatconbined with iterative reconstruction was undifferent. |
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