MRI In The Diagnosis Of Small Gastric Stromal Tumors And The Evaluation Value Of Risk Classification

Objective: Application MRI to display the structure of gastric wall,to evaluate the diagnostic value of conventional MRI and diffusion weighted imaging in small gastric stromal tumors,and to make a preliminary differential diagnosis.To analyze the MRI features of gastric stromal tumors,and to explore the correlation between different imaging signs and different risk of gastric stromal tumors.Methods: 40 patients with suspected small gastric stromal tumors in the Second Hospital of Tianjin Medical University from July 2017 to December 2019 were studied.All cases were subjected to conventional MRI and DWI scans and the images were analyzed.Record the origin of gastric wall layer,location,diameter,growth pattern,signal,T2 WI and DWI of the tumors,and measure the average ADC value to evaluate the diagnostic accuracy of MRI for small gastric stromal tumors.Differential diagnosis was performed by analyzing MRI signs.In addition,48 patients with gastric stromal tumors confirmed by pathology and immunohistochemistry were collected,and were examined by conventional MRI and DWI.The tumor size,location,morphology,growth pattern,necrosis,ADC value and relative ADC value were recorded.The correlation between MRI signs and different risks(very low-low risk group and intermediate-high risk group)were compared.Results: MRI can show 2 to 3 layers of normal stomach wall anatomy.The overall detection rate of MRI in 40 patients with suspected small gastric stromal tumors was 92.5%,of which the detection rate of T2 WI and DWI was 85.0% and 92.5%,respectively.The sensitivity,specificity,positive predictive value and negative predictive value of T2 WI in the diagnosis of small gastric stromal tumors were 92.6%,30.8%,73.6% and 66.7%,respectively.The sensitivity,specificity,positive predictive value,and negative predictive value of DWI for the diagnosis of small gastric stromal tumors were 96.3%,15.4%,70.3%,and 66.7%,respectively.Among the 40 cases,3 cases were not shown on MRI,the other 37 cases(26 cases in gastric stromal tumor group and 11 cases in non gastric stromal tumor group)had no significant statistical significance in tumor size,growth pattern,T2 WI and DWI tumor display(P>0.05),while the tumor location,signal uniformity and ADC value were the important features to distinguish small gastric stromal tumors and other non gastric stromal tumors(P<0.05).Small GISTs are more common in the fundus or body,with cystic necrosis,and ADC values are lower than non stromal tumors.There was no significant difference in the location of GISTs between the very low risk group and intermediate-high risk group(P>0.05).The tumor size,morphology,growth pattern,presence or absence of necrosis,ADC value and r ADCm value were significantly different in MRI features(P<0.05).The low-risk GISTs were small in diameter,usually round or ovoid,with more endophytic growth patter and less cystic necrosis.With the increase of biological risk of tumors,tumors are large in diameter,irregular in shape,and show an exophytic growth pattern or dumbbell,cystic necrosis are common.The average ADC value and r ADCm value of very low-low risk GISTs were higher than those of intermediate-high risk GISTs,but there was no significant difference in ROC curve between them(P>0.05).Conclusion:(1)When the stomach is moderately full,the normal gastric wall can show the 2-3 layers structure of the stomach on T2 WI,which can show the location,size,shape and signal of the submucosal tumor of the stomach.(2)T2WI and DWI sequence can detect small gastric stromal tumors with high sensitivity.T2 WI combined with DWI can improve the diagnostic value of small gastric stromal tumors.MRI can be a valuable diagnostic and follow-up tool for small gastric stromal tumors.(3)The location of the tumor,the presence of cystic necrosis and ADC value can be further distinguished from other non gastric stromal tumors.(4)The location of tumors cannot be assessed for risk classification of GISTs,but tumor size,morphology,growth pattern,presence of cystic necrosis,and ADC values are important signs for identifying low-risk and medium-high-risk GISTs.The diameter is ≥5 cm,irregular lobulated,and show an exophytic growth pattern or dumbbell,and cystic necrosis,the lower ADC value indicates a higher risk,which provides imaging reference for the preoperative diagnosis of GISTs and the selection of treatment options.