| Objective:Lymphatic metastasis is the main mode of metastasis of rectal cancer,which is closely related to the prognosis of patients.The preoperative imaging evaluation of lymph node involvement has a guiding role in the treatment of rectal cancer.However,the sensitivity of various preoperative examination methods is not ideal,and it cannot effectively assist the lymph node dissection during operation.It is of practical value to explore tracers that can develop lymph nodes before and during operation.The purpose of this study was to investigate the feasibility and effect of dual tracer of iodixanol-carbon nanoparticles(CNPs)suspension in lymphatic metastasis models of rectal cancer before and during operation.Methods:Firstly,human colorectal cancer HCT116 cell line was cultured to prepare a cell suspension,and the HCT116 cell suspension was injected under the rectal mucosa of nude mice to establish an orthotopic transplantation model of rectal cancer lymphatic metastasis.The in vivo imaging system was used to continuously observe the growth and metastasis of xenograft tumors,and the histology of the orthotopic transplantation model was verified.Next,the iodixanol-CNPs suspension was prepared by using the excellent adsorption properties of CNPs,and the basic physical-chemical properties of iodixanol-CNPs suspension were measured by scanning electron microscopy and laser particle size analyzer.The dynamic adsorption experiment and membrane dialysis method were used to investigate the adsorption and in vitro release performance of iodixanol by CNPs.Interstitial lymphography was performed using iodixanol-CNPs and iodixanol,and the experimental data were fitted to the adsorption isotherm model and the release kinetic model.Finally,the interstitial lymphography was performed by using the iodixanol-CNPs suspension,iodixanol solution,and CNPs suspension,respectively.The enhancement characteristics of CT lymphography were evaluated by micro-CT scanning and image collection.After scanning,the localization of preoperative CT lymphography was compared with the intraoperative lymph node biopsy Combined with histological examination,the value of CT lymphography in the diagnosis of lymphatic metastasis was evaluated.Results:(1)4×106 red fluorescent protein labeled HCT116 cells were injected under the mucosa of the posterior wall of nude mice,and the success rate of visual xenograft model was 100%.(2)The expression of fluorescent protein of tumor cells was detected in all nude mice 1-7 weeks after transplantation.After orthotopic transplantation,the volume of transplanted tumor increased and the integrated optical density increased with time.The metastasis of caudal mesenteric lymph nodes and para-aortic lymph nodes increased in a time-dependent manner in nude mice.(3)The result of lymph nodes expressing fluorescent proteins to determine metastasis was consistent with histological examination.At the beginning of 4 weeks after orthotopic transplantation,lymphadenopathy was evident,with para-aortic lymph nodes,liver and lung metastasis.(4)The prepared iodixanol-CNPs suspension was black,relatively uniform in size,and slightly aggregated.The average particle size was(190.87±1.73)nm,and the zeta potential was(-10.21±0.36)mV.(5)The process of adsorption of iodixanol onto CNPs was consistent with the uniform monolayer adsorption described by Langmuir isotherm model.(6)The release rate of iodixanol loaded CNPs was slower than that of free iodixanol in PBS with pH 7.4.The best in vitro release fit was the Higuchi model,which showed that iodixanol loaded CNPs had a certain sustained release effect.(7)In the iodixanol group,the enhancement of lateral pelvic lymph node was observed at 5 min and 30 min,and the enhancement was cleared at 1 h.In the dual tracer group,the enhancement of lateral pelvic lymph node was observed at 2 h,3 h,and 5 h.The best angiographic effect was obtained at 3 h,and the enhancement was cleared at 24 h.In the CNPs group,there were no enhanced lymph nodes at each interval.(8)41 enhanced lymph nodes were detected by indirect CT lymphography,of which 18 were in the iodixanol group and 23 in the dual tracer group,which were consistent with the location of the lymph node biopsy.(9)The sensitivity and positive predictive value of the caudal mesenteric lymph nodes metastasis in both groups were 100%when the uneven density,the irregular shape,and the filling defect were used as the diagnostic criteria.The sensitivity of lateral pelvic lymph node metastasis in the dual tracer group and iodixanol group(78.6%vs.81.8%),specificity(77.8%vs 85.7%),accuracy(78.3%vs.83.3%),positive predictive value(84.6%vs 90.0%),and negative predictive value(70%vs.75%)Conclusion:Indirect CT lymphography with iodixanol-CNPs suspension could not only locate the lymph nodes and evaluate the metastasis before operation,but also assist in intraoperative biopsy with black-stained lymph nodes.It was an economic and easy method to carry out,which could provide new ideas for preoperative evaluation and intraoperative dissection of lymphatic metastasis. |
PDF Full Text Request