The Experimental Study Of Multimodal Imaging In The Rabbit Gastric VX2 Cancer Model And Biological Target Volum Delineation

Part I: Establishment and CT Comprehensive Evaluation of a Rabbit gastric VX2 cancer modelObjectiveTo establish the animal model of gastric VX2 cancer in rabbits, then to evaluate gastric VX2 cancer imaging features using computerted tomography（CT） which set up the experimental basis for this model. To establish the animal model of gastric ulcer in rabbitsthen to evaluate its imaging features using CT which set up the experimental basis for this model.Material and methodsVX2 tissue block were implanted into the anterior gastric wall for establishment of animal models in nine New Zealand rabbits. The tumors were allowed to grow for two weeks, then gastric VX2 cancer model weres scanned by CT every week. Three animal models were sacrificed randomly after they received CT scans. Anatomy probe and pathology examination of gastric tumor, and compare with the results of CT scans to evaluate the replication of the rabbit gastric VX2 Cancer model and stability.Acetic acid was implanted into the anterior gastric wall for establishment of animal models of gastric ulcer in six New Zealand rabbits. CT scan was complated at The 2 day and 1 week after model were established. For assessment of gastric ulcer model, three animal models were sacrificed randomly after they received CT scans.Anatomy probe and pathology examination of gastric tumor, and compare with the results of CT scans to evaluate the replication of the rabbit acetic acid gastric ulcer model and stability.ResultsAll of the 9 rabbits were successfully implanted with VX2 cancer in anterior gastric wall by operation. CT scans review that the tumor appears very clearly of necrosis area with slightly low density. Enhancement CT reviews that manifestation of reinforcement, obvious annular rim reinforcement, and necrotic area without reinforcement. Tumor around the hole in the stomach stiffness with mucosal fold disappears. At inoculation of 2 weeks, tumor volume were 0.7-2.0cm3（diameter 1.3 ¹.7cm）, at 3 weeks, tumor volume were 2.9-4.6cm3（diameter 2.0³.0cm）, at 4 weeks tumorvolume were 6.8-50.6cm3（diameter 3.4⁵.0cm） in diameter, in different levels of three rabbit apperace metastases of peritoneal（3 cases）, abdominal wall（2 cases）,retroperitoneal（2 cases） and liver（1 case）.At 2 w, CT showed kind of circular soft tissue mass density with boundary,enhanced CT show a little or no obvious arterial enhancement. At 3 weeks, CT showed irregular tumor of approximate circular, there began to appear a small amount of low density necrosis area in the center of tumor, enhanced CT circular reinforcement, part had no clear boundary. At 4 weeks, CT appeared different degree of necrosis, no clear boundary between tumor and surrounding tissue, some had abdominal wall infiltration and peritoneum metastases. Enhancement CT showed abdominal multiple nodules, strengthen the inequality. CT in the diagnosis of gastric cancer at 2 w and subsequently, the sensitivity of tumor was 100%（9/9 cases）, the abdominal wall（2/2 cases）, abdominal cavity 100%（3/3 cases）, liver metastases100%（1/1）, retroperitoneal lymph node metastasis 50%（1/2）. All of the 6 rabbits of gastric ulcer were successfully implanted with acetic acid in anterior gastric wall by operation.an was stability. 2 d CT scan revealed the density of stomach ulcer were approximatly the nomrmal gastric wall, the enhancementof the ulcer surrounding was slightly higher than the gastric wall. At 1 w, the density of stomach ulcer was slightly higher the normal surrounding site with no obvious strengthen.VX2 tumor section showed red or gray, less clear boundary, and growth rapidly.Gray-white or yello-white necrosis and liquefaction were always visible inside the tumor. HE staining showed that the tumor cells were in nested or diffuse distribution,VX2 tumor cells had different shapes, and the cytoplasm was small and the nuclei were deeply stained. The gastric ulcer showed gray-red solid bag, 1 week when the bag is a gray red, less light than at 2d. HE staining showed hemorrhage, necrosis and large numbers and lymphocytes infiltrated in mucosa..ConclusionThe rabbit gasric VX2 cancer model can be duplicated at highly successful rate.CT scans can accurately response the growth, necrosis and other pathological conditions and more real reaction of tumor metastasis of the tumor. Rabbit VX2 carcinoma model can be used for multimodal imaging diagnosis of gastric cancer and further research.CTevaluation is useful in screening and monitoring the experimental animal. The rabbit of acetic acid gastric ulcer modelcan be duplicated at highly successful rate and stable, the establishment of the gastric ulcer model could be used as control study of rabbit gastric VX2 cancer.Part II: Experimental Study of multimodal imaging in the rabbit gastric VX2 cancer model and acetic acid gastric ulcer modelObjectiveAssessment rabbit gasrric VX2 gastric tumor and metastasis of animal model useing Ultrosound, CT and PET/CT technology, ¹⁸F-FDG, ¹⁸F-FLT and ¹⁸F-FMISO multiple tracers used to evaluate the sugar metabolism, tumor proliferation and lack of oxygen of the tumor. Comparison of rabbit VX2 gastric cancer model and gastric ulcer model with multimodality imaging techniques in the diagnosis. Evaluation the relationship of ¹⁸F-FDG,¹⁸F-FLT and ¹⁸F-FMISO PET/CT imaging of rabbit gastric VX2 cancer with Glut-1, Ki67 and HIF-1αimmunohistochemical study, providing the usefullness of the variety of tracer basis for the growth situation of tumor.Material and methodsTwenty-four rabbits were all successfully implanted with VX2 cancer in anterior gastric wall by operation.12 rabbits were establish the model of gastric ulcer.Multimodality imagings were consecutive at 1 week, 2 weeks, 3 weeks.4 weeks, by Doppler ultrasound, PET/CT scans(¹⁸F-FMISO,¹⁸F-FLT and¹⁸F-FDG) and enhanced CT, each time after imaging examination were randomly executed 6 rabbits. When the gastric ulcer model was established, rabbits at 2d and 1 week received color Doppler ultrasound, PET/CT scans and enhanced CT. Six rats were randomly sacrificed at each time of examination. Pathological examination was performed, and the results were compared with imagings. HE staining was performed and interpretation of the results of the organization. immunohistochemistry staining of VX2 gastric cancer with Glut-1, Ki67 and HIF-1, using double blind method for diagnose pathology results, each immune section observation of five fields（×400）,and take the average value as staining intensity score..Results24 tumor bearing rabbits were removed and 2 rabbits were killed. A total of 22 rabbits were included in the study because 2 rabbits died of anesthetic accident and infection. The successful model of gastric ulcer was established in 12 rabbits. VX2 tumor of the gastric at 1 week, the tumor volume was 0.3±0.1cm3（0⁰.4cm3）; at 2week, the tumor volume was 1.4 ± 0.6cm3（0.7².3cm3）; at 3 weeks, the tumor volume was 3.1±1.1cm3（2.0⁴.6cm3）; at 4 weeks, the tumor volume was 17.7±11.6m3（6.8³7.57cm3）. Ultrasound could clearly show VX2 gastric cancer from the beginning of the first week. Rabbit gastric VX2 cancer uptake¹⁸F-FDG well, at 1week, only 2 rabbit of 5 had a few of radioactive uptake, SUVmax=1.2, SUVmax=1.0,respectively; at 2 week, the SUVmax of VX2 tumor was 2.8± 0.3（2.4³.2）; at 3weeks, the SUVmax of VX2 tumor was 4.3±0.9（3.1⁵.6）; at 4 weeks, the SUVmax of VX2 tumor was 7.2 ± 0.8（6.0⁸.3）; VX2 tumor volume size and SUVmax of¹⁸F-FDG imaging had positive correlation（P<0.01, r =0.782）. No abnormal¹⁸F-FMISO and¹⁸F-FLT uptake of rabbit gastric VX2 cancer. 33%（2/6 cases） of rabbit gastric ulcer had slightly higher ¹⁸F-FDG uptake at 2d imaging, at 1 week imaging, ¹⁸F-FDG uptake was seen in inflammation. No abnormal ¹⁸F-FLT radioactivity uptake was found in the gastric ulcer. Gastric ulcer package¹⁸F-FMISO uptake increased, the 2d SUVmax was 5.6±1.2（4.8⁷.5）, and 1 week SUVmax was5.0±1.6（3.9⁷.1）, 1 week inflammatory package block of tracer uptake was slightly lower than that of 2d, but there had no significant difference（t=3.078,P=0.200）.1week after tumor inoculation, only 60%（3/5 cases） of the models showed gastric tumor by enhanced CT with no obvious enhancement. But, at 2⁴ weeks, tumors were seemed clearly, enhanced scan see various arterial phase of enhancement. At 2d,gastric ulcer package block CT scan shown to be approximated ulcer site density than the surrounding normal gastric wall, around the ulcer, slightly higher than gastric wall of annular enhancement. At 1 week, mass density of ulcer was higher than that of the surrounding normal gastric wall density, no obvious signs of strengthening. The staining of Ki67, HIF-1α and Glut-1 of VX2 tumor were satisfied. Glut-1, Ki67,HIF-1α immunohistochemical indicators of VX2 at 1 week in the staining score was4⁵; in the 2 week score for 4⁶; 3 weeks score for 5⁶, 4 weeks when the score was3⁴. Glut-1 and SUVmax had no correlatinship（P=0.77, r=-0.36）, so do Ki67（P=0.76,r=-0.37）and HIF-1α（P=0.814,r=-0.29）.ConclusionUltrosound can relatively early show the tumor of rabbit gastric VX2 tumor, but not comprehensive to assessthe metastases of gastric VX2 cancer because of the misdiagnosis. The sensitivity of enhanced CT for early VX2 gastric cancer detection was slightly higher than that of PET/CT, can hint metastases clearly, but for some metastases, enhanced CT could be easily missed diagnosis. ¹⁸F-FDG, ¹⁸F-FLT and¹⁸F-FMISO The sensitivity of¹⁸F-FDG imaging and CT for early diagnosis at 1 week of gastric VX2 cancer is lower than Ultrosound, but for the assessment of metastases,¹⁸F-FDG is more comprehensive. In the multiple tracers of PET/CT imaging, tumor and its metastases uptake¹⁸F-FDG, but, there have no uptake of¹⁸F-FLT and¹⁸F-FMISO in tumor and its metastases of gastric. The expression of Glut-1, Ki67,HIF-1 alpha three kinds of immunohistochemistry in VX2 gastric cancer were higher,at 2³ weeks, the expression was the highest. Glut-1, Ki67, HIF-1α were decreased at 4 weeks. Few gastric ulcers had slightly higher ¹⁸F-FDG uptake in inflammation.No abnormal ¹⁸F-FLT radioactivity uptake was found in the gastric ulcer. Gastric ulcer package¹⁸F-FMISO uptake increased.PartⅢ: biological target volum delineation of Rabbit gastric VX2 cancer useing multimodalite imagingsObjectiveMeasure the VX2 tumor size of gastric cancer by PET/CT and enhanced CT,respectively, and compare the outcomes with real tumor size measure by histology.Compare the usefulness and value of PET/CT and enhanced CT in targeting delineations. Taking SUVmax and tumor size as quantitative index, we establish a mathematical model for the delineation of biological target volum.Material and methodsWe selected 13 VX2 models from the 22 VX2 rabbits with VX2 tumor imaging clearly and without planting metastasis of surrounding a tumor-burdened. Measure tumor long axis and short axis on CT imaging, calculation the tumor volume, and compared with the actual size of tumor. Measure tumor long axis and short axis on¹⁸F- FDG PET imaging（SUVmax = 2.5 and 40% SUVmax value） in 3D sketch and record, calculation of tumor volume, and compared with the actual size of tumor. On the basis of tumor size calculate the best SUV values used to measure the tumor size.Taking SUV and tumor size as quantitative indexes by the multiple linear regression analysis to establish mathematical model of target sketch. Measure the VX2 cancer infiltration depth, sketch infiltration depth of¹⁸F-FDG imaging target outline mathematical model.ResultsCT measurement volume were slightly larger than that of histological measurement in 4 VX2 gastric tumor in 13 rabbits, 7 rabbits were smaller than that of histological measurement, and 2 rabbits had the same volume as the histological measurement. Taking SUVmax = 2.5 as the boundary values, volume of 4 rabbits were slightly larger than the tissue volume measurement; 6 rabbits were than histological volume measurement, mainly concentrated in smaller tumor volume, increased radioactive uptake of relatively weak organization; 3 and surveying the same volume. Taking 40%SUVmax as the boundary value, the tumor volume of 6rabbits is slightly larger than the real tissue volume. The reasons were mainly concentrated in larger tumor size, and the higher uptake of¹⁸F-FDG; 4 rabbits had less volume than histological measurement; 3 rabbits surveying the same volume.The most excellent SUV values of 13 rabbits gastric VX2 cancer to target biological volume was 47.0±12.2%（30%⁶0%）. On the basis of SUVmax value and tumor size as a quantitative index, %SUVmax linear regression model is established as %SUVmax=72.842-4.329 SUVmax. The depth of tumor invasion was 0.3±0.2cm（0.0⁰.7cm） in 13 rabbits with VX2 tumor. VX2 tumor invasion depth was positively correlated with tumor size（P=0.043, r=0.998）. The suitable SUVmax percent for Extended boundary outline because of tumor invasion was 67.4±17.1%（50%⁸5%）,which extended the %SUVmax 20.4±18.5（0²0）.ConclusionPET/CT imaging could be more accurate estimation of tumor size and volume compared with CT, and take %SUVmax=72.842-4.329 SUVmax as the PET/CT SUV delineation of the target biological volume value can be more precise delineation. CT is easy to underestimate the size of the tumor. Taking SUVmax=2.5 as the boundary value of the outline is prone to overestimate the volume of tumor have abnormally increased SUVmax, and underestimate the SUVmax increased less tumor. And40%SUVmax is prone to underestimate the SUVmax abnormally increased tumor volume, overestimate volume of tumors that have less increased SUV.For CTV of VX2 tumor target delineation, increase about 20.4%SUVmax could be suitable.