| Objective:This study combined fluorine-18-deoxyglucose (FDG) PET/CT andcontrast-enhanced ultrasound (CEUS) to acquire images and data prior and subsequent toradiofrequency ablation (RFA) to observe early changes in rabbit VX2tumors and todetermine whether there is significant difference between the standard uptakevalues(SUV)measured before and after RFA treatment. In this study, we acquire imagesand data prior and subsequent to radiofrequency ablation(RFA) using PET/CT combinedwith CEUS so as to evaluate sensitivity and specificity of the combination of PET/CT andCEUS in assessing the response to RFA.The advantage and dis advantage of these twomethods compared to CT and MRI were also discussed and the correlation between thelevel of residual tumor’s biochemical indicators and rapid tumor progress were studied.Methods:Nine3-4months old New Zealand rabbits weight between2400~3100grams withVX2tumors in hind limbs were randomly divided into two groups and fed separately for2weeks. US shows the volume of VX2tumors ranges between1.5～3.5cm3, In thetreatment group (n=7),20tumor underwent RF ablation and rabbits that did not receiveRFA constituted a control group (n=2) with total5tumors. RFA was performed14daysafter VX2implantation.30w(watt) was chose as the starting power, and the power wasincreased by10w per minute to a maximum value of70w, the average duration time was184±50.4s. The control group was only preformed needle puncture with no ablation.PET/CT and CEUS examination was applied in each groups2days before and14daysafter treatment. Choose13MHZ linear probe, ultrasound contrast agent SonoVue for (0.5ml/kg).18F-FDG dose for PET/CT scan was37MBq/kg.The animals were sacrificed at4 weeks after operation. The specimens were evaluated histologically,including HE staining,VEGF,CD31and MMP-9immunohistochemical staining as well as transmission electronmicroscope observation. Data analysis was performed by SPSS11.7statistical software,measurement data was represented by mean±standard deviation, said CEUS and PET/CTresult comparison was performed by matched-sample comparison t test. There was asignificant difference when P<0.05.Results:Success rate of animal model establishment was100%, the total number of tumorblocks was20, of which15was ablated. The success rate of CEUS and PET/CT imagingboth were100%. All animals’ food intake were found to reduce after ablation in theexperimental group and recovered gradually.2cases of skin burn have occurred.Theimmune-histochemical results were consistent with gross pathological and transmissionelectron microscopy observation.12tumors showed "holding ball" sign, the enhancementlasts about3~6s, and cleaned up at8~15s after injection. Tumors with centralnecrosis showed bagel-like enhancement. Blood flow signals lasts7~10s in the targetarea after ablation, the ablation area showed low echo signal with perfusion defect zone.Ultrasound showed preoperative tumor has an average diameter of2.3±1.6cm, and apostoperative average tumor diameter of1.9±1.55cm,diameter was reduced significantly(P <0.05) after treatment.High18-FDG uptake area reduced after RFA procedure.Expression of MMP-9, VEGF and CD31decreased significantly at2days and2weeksafter operation.The sensitivity of CEUS was87.3%and specificity was76.5%.Thesensitivity of PET/CT was84.2%and specificity was86.3%.The sensitivity(92.2%) andspecificity(90.7%) of the CEUS and PET/CT combination is significantly higher than bothPET/CT and CEUS group (P <0.05).Conclusions:Radiofrequency ablation is an effective treatment for rabbit VX2tumor and the CEUScan facilitate the manifestation of low volume and low velocity blood flow signals with aintuitive, convenient, real-time dynamic observation.The display of the remaining smalllesions found in the necrosis area after interventional treatment is superior thanconventional conventional Color Doppler ultrasound. The postoperative SUV values oftumor tissue was significantly reduced compared with preoperative values (P <0.05). Inthis study, sensitivities of PET/CT and CEUS showed no obvious difference, but thespecificity of PET/CT was significantly higher than CEUS’s (P <0.05).The combinationof PET/CT and CEUS can further improve the sensitivity and specificity for the detection of residual tumor or recurrence, which is safe and effective in monitoring the therapy effectof radiofrequency ablation,18F-FDG PET/CT and CEUS is useful in the assessment ofRFA therapeutic response and completeness, PET/CT and CEUS possess their ownadvantages,and the combination of them can increase the detection rate of residual tumorand recurrence. |
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