Identification Of Inflammatory And Metastatic Lymph Nodes By Diffusion-weighted Imaging: A Experimental Study

Part IThe establishment of Animal models of inflammatory and metastatic lymph node and parameter selection of diffusion-weighted imaging[Objective]To establish animal models of benign and malignant lymph nodes with New Zealand white rabbits. To image the lymph nodes with diffusion-weighted imaging taking different b value (300,600 and 900), and to select the optimal parameters.[Materials and Methods]The establishment of metastasis model:New Zealand white rabbits 6, irrespective of gender, body weight 2.0～2.5kg, after thawing and washing with saline, VX2 tumor tissues were cut into pieces of about 1mm3 with surgical scissors for the ophthalmology for reservation. After Skin preparation of operation area (New Zealand white rabbits were the lateral rectus muscle shares both thighs Office) and successful anesthesia, New Zealand white rabbits were fixed laterally on the operating table, operation area was disinfected (including the surgical field 8cm range), and then cover the area with shop-hole towel. According to conventional incision procedures, cut rabbit femoral lateral rectus fascia skin layer for 1.5cm, and separate to the subfascial layer. Appropriate VX2 tissues were placed subfascially with forceps and then close incisions, disinfection and pad dressing were preceded in turn.The same surgical procedures were made on the opposite side. Intramuscular injection (40U/day) of penicillin to prevent infection for consecutive three days after operation. VX2 tumor inoculation as oncology Group(1-6) was established on the same day. Tumor growth enlargement of lymph nodules were observed every day. Established model of inflammation group:New Zealand white rabbits were 6, of either gender, weighing 2.0～2.5kg. Removing the egg white from several fresh eggs and the left egg yolk liquid approximately 5ml was mixed with equivalent amount of saline. After Skin preparation of operation area (New Zealand white rabbits were the lateral rectus muscle shares both thighs Office) without anesthesia, New Zealand white rabbits were fixed laterally on the operating table, operation area was disinfected, and then covered the area with shop-hole towel.Intramuscular injection of the 2 ml mixture of egg yolk and saline were administered slowly. The same procedure was repeated on the contralateral part. After injection, wound disinfection was carried out. Intramuscular injection (40U/day) of penicillin was administered for the three consecutive days to prevent infection. From the first day after inoculation, growth and the popliteal lymph node enlargement were observed every day.GE Signal Excite 1.5TMR, and Shanghai-time company dedicated rabbits coil sequences were used. Scanning sequences included cross sectional SET1 sequence, sagittal SET1 sequence, cross-sectional FSET2 sequence, sagittal FSET2 sequence and diffusion sequence. Rabbits of the inflammatory group and the transfer of group underwent diffusion-weighted imaging with different b value (300,600,900) respectively. Comparison was made according to signal to noise ratio and optimal b value and the best images were selected.Rabbits were sacrificed after the scan, Specimens of lymph node (HE staining) was obtained through biopsy.[Results]1,In inflammatory group,10 days after inoculation of egg yolk, swollen popliteal lymph nodes can be detected; 28 days after inoculation of VX2 tumor, the to the enlarged metastatic lymph nodes could be detected. T1-weighted imaging, T2-weighted imaging could showed the popliteal lymph nodes, respectively.2,FSE T2WI imaging showed enlarged popliteal lymph nodes in the New Zealand white rabbits, lymph node, regardless of inflammatory or metastatic, showed high signal in diffusion-weighted imaging. Taking 600 as b value, minimal influence was observed on the diffusion-weighted imaging in experiment with the best image quality.[Conclusion]1,Popliteal lymph node metastasis model.was established with VX2 tumor inoculation in bilateral lateral rectus muscle of the New Zealand white rabbits. Popliteal lymph node inflammatory model was established with intramuscular injection of egg yolk in bilateral lateral rectus muscle of the New Zealand white rabbits.New Zealand white rabbits.2,FSE T2WI imaging showed enlarged popliteal lymph nodes in the New Zealand white rabbits clearly. Which were high signal in diffusion-weighted imaging. When b value was set as 300,600 and 900 respectively, lymph node signal value decreased as b value increased, Taking 600 as b value, minimal influence was observed on the diffusion-weighted imaging in experiment with the best image quality.Part IIDifferential diagnosis of inflammatory and metastatic lymph nodes with Diffusion-weighted imaging:A experimental study[Objective]To explore the possibility differential diagnosis of benign and malignant lymph nodes with diffusion-weighted imaging, and to provide proof for early detection of tumor metastasis.[Materials and Methods]1,Magnetic resonance scanning was performed on the animal models established in part one.2,MRI examination:the same scan parameters as part one.3,DWI image analysis and calculation of ADC values:4,Statistical analysis:Statistical analysis of data with The SPSS 10.0 software.[Results]1,Inflammatory and metastatic lymph nodes were both high signal in diffusion-weighted imaging.2,,When b value was 600, the ADC value of the diffusion-weighted imaging for metastatic lymph nodes was (0.957±0.216)×10-3mm/s, the ADC value for inflammatory lymph nodes was(1.210±0.109) x 10-3mm/s, P<0.05.There was significant statistical difference in the two ADC values. According to ROC curve, taking ADC value of 1.107×10-3mm/s as the threshold value, the sensitivity was 91%,and specificity was 75% for the differential diagnosis of inflammatory and metastatic lymph nodes.[Conclusion]When b value was 600, the ADC value of metastatic lymph nodes in the diffusion-weighted imaging was (0.957±0.216)×10-3mm/s, the ADC value of inflammatory lymph nodes was(1.210±0.109)×10-3mm/s, P<0.05.There wassignificant differences in ADC values between the two groups. According to ROC curve, taking ADC value of 1.107×10-3mm/s as the threshold value, the sensitivity was 91% and specificity was 75% for the differential diagnosis of inflammatory and metastatic lymph nodes. Therefore, the ADC value of the lymph nodes with diffusion-weighted imaging measurements is a effective measure for differential diagnosis in inflammatory metastatic lymph node lesions.