A Preliminary Study Of Spectral CT In The Diagnosis Of Extramural Vascular Invasion In Rectal Cancer

Objective: To investigate the clinical feasibility and related factors of spectral CT in the diagnosis of extramural vascular invasion(EMVI)in rectal cancer.Methods: A total of 59 patients with rectal cancer admitted to the hospital from April 2021 to May 2022 were selected as the research object.Based on the existence of rectal cancer EMVI,the patients were divided into two groups: rectal cancer EMVI positive group(n=35)and negative group(n=24).All patients underwent enhanced abdominal scanning with spectral CT imaging,and underwent rectal cancer resection.Conventional scanning method was used in the plain scanning phase,and spectral CT mode was used in the delayed phase,venous phase and arterial phase.At the same time,according to the postoperative pathological diagnosis results,the preoperative diagnostic efficiency of spectral CT imaging for rectal EMVI was evaluated,and then combined with the postoperative clinicopathological data of patients,the relationship between rectal EMVI and clinicopathological factors was analyzed.The post-processing workstation of dual-source and dual-energy CT imaging was used to post-process and analyze the images.The iodine concentration in delayed phase,venous phase and arterial phase of rectal cancer combined with EMVI negative group and positive group were measured respectively.The region of interest(ROI)was measured three times at the largest lesion level and two adjacent levels,and the average value was taken.The iodine concentration of abdominal aortic branches at the same level was measured and recorded,and the standardized iodine concentration(NIC)was calculated.Through post-processing venous phase of thin layer to obtain the appropriate reconstruction image after image,and then in the first sacral vertebra vertebral level measurement on rectal vein pipe diameter,and use the receiver-operating characteristic(ROC)curve in the rectum vein diameter,delay,venous phase were analyzed,and the NIC of rectal cancer EMVI specific degrees,sensitivity,and to predict the optimal threshold.Results :(1)all patients completed the examination successfully.Among 35 patients with EMVI positive rectal cancer,25 cases were accurately diagnosed by spectral CT imaging,and the detection rate was71.43%.Among the 24 patients with negative EMVI of rectal cancer,20 cases were diagnosed with EMVI,the detection rate was 83.33%,and the accuracy rate was 76.27%(45/59)in 45 cases.(2)By univariate analysis,positive EMVI of rectal cancer was associated with lymph node metastasis,tumor stage,tumor differentiation degree and tumor maximum diameter.(3)The NIC of delayed phase,venous phase and arterial phase in EMVI positive group were(0.57±0.03),(0.51±0.03)and(0.28±0.09)respectively.The NIC of delayed phase,venous phase and arterial phase in EMVI negative group were(0.45±0.03),(0.41±0.03)and(0.24±0.06),respectively.In delayed phase and venous phase,the NIC value of positive group was significantly higher than that of negative group(P<0.05).In the arterial phase,although the NIC of the positive group was slightly higher than that of the negative group,there was no significant difference between the two groups(P>0.05).At the same time,the diameter of superior rectal vein in EMVI positive group and negative group was(0.53±0.08)cm and(0.42±0.12)cm,respectively,and the comparison between the two groups was statistically significant(P<0.05).(4)In the ROC curve,when the area under the curve(AUC)value of NIC in the venous phase was 0.796 and the threshold was 0.45,the specificity and sensitivity were 69.6% and 78.6%,respectively.The AUC value of NIC in the delay period was 0.863.If the threshold was 0.54,the specificity and sensitivity were 95.7% and 64.3%,respectively.At the same time,when the AUC value of the diameter of the superior rectal vein was 0.706 and the threshold was 0.41 cm,the specificity and sensitivity were 52.2% and 92.9%,respectively.Conclusions: 1.From the perspective of morphology,spectral CT imaging has a high accuracy in evaluating EMVI status of rectal cancer;2.2.Positive EMVI of rectal cancer is related to lymph node metastasis,T stage of tumor,tumor differentiation degree and maximum diameter of tumor.3.The NIC values of delayed phase,venous phase and arterial phase in EMVI positive rectal cancer group were higher than those of EMVI negative rectal cancer group.There was statistically significant difference in NIC values between delayed phase and venous phase,but there was no difference in NIC values in arterial phase.At the same time,when the threshold values of delayed phase and venous phase were 0.54 and 0.45,respectively,the specificity and sensitivity of energy CT imaging in differentiating EMVI negative from positive rectal cancer were higher.4.From the perspective of the diameter of the superior rectal vein,the EMVI positive group of rectal cancer was significantly higher than the negative group,and the specificity and sensitivity were higher when the threshold was 0.41 cm.Therefore,spectral CT imaging can evaluate the EMVI status of rectal cancer according to the morphological results on the one hand,and quantitatively analyze the difference of NIC on the other hand,so as to accurately evaluate the EMVI status of rectal cancer.