The Value Of Diffusion-weighted Imaging Combined With Conventional Magnetic Resonance Imaging Sequences In The Classification Of Benign And Malignant Tumors Of Rectum

Objective:To explore the clinical application value of diffusion-weighted imaging?DWI?combined with conventional magnetic resonance imaging?MRI?sequences in the classification of benign and malignant tumors of rectum.Materials and methods:From April 2012 to March 2016,the clinical data and MRI images of 83 patients with pathologically proven primary rectal tumor who had undergone preoperative conventional MRI and DWI were reviewed retrospectively.Among of these patients,54 were male and 29 were female.Their age ranged from 17 to 83 years with an average of?57.1±14.8?years.Inclusion criteria:?1?the final pathological diagnose was primary rectal tumors;?2?the clinic data and MRI images were completely;?3?the patient received no neoadjuvant chemotherapy before MRI;?4?the interval between MRI and surgery was no more than 2 weeks.Exclusion criteria:?1?image quality was poor;?2?the final pathological diagnoses were not primary rectal tumors.The postoperative pathological results were as following: adenocarcinoma?AC?in 56 cases,mucinous adenocarcinoma?MC?in 15 cases,and 12 cases of adenoma and polyp?A-P?.MRI features of all the cases were analyzied,including morphology,signal,enhanced features and apparent diffusion coefficient value?ADC?.We compared age,sex and MRI features of rectal adenocarcinoma,mucinous carcinoma and adenoma-polyps.Statistical analyses were performed using One-Way Analysis of Variance?ANOVE?or Kruskal-Wallis H test.And,in order to obtain the optimal cut-off value and its sensitivity and specificity in diagnosis for diffetenting multiple groups in AC,MC and A-P,a receiver operating characteristic?ROC?analysis was appplied to the mean ADC values.A P value less than 0.05 was considered statistically significant.Results:1.The age and sex: the age of MC<A-P<AC,and only the difference between MC and AC had statistically significant?P<0.01?;the male and female ratio of AC,MC and A-P were 37/19,13/2 and 4/8,respectively,and only the difference between MC and A-P had statistically significant?P<0.0125?.2.The MRI features: MC and AC were both intestinal wall thickening type predominant,and mean length of the lesions in MC was significantly greater than that in AC?P < 0.01?,while,the differences of thickness or circumference had no statistically significant?P>0.05?;A-P was mass type predominant,the max diameter of A-P was lower than that of MC with statistically significant?P<0.01?,lower than that of AC without statistically significant?P > 0.05?.The SI of AC was mainly isointense or hypointense on T₁ WI,slightly higher on T₂ WI,markedly hyperintense on DWI;After enhancement,the edge of tumor was blur or burr shape,the solid part was obviously enhanced during arterial phase and decreased during venous and delayed phase,the cystic and necrotic were no enhanced,and postoperative pathological T stage was most T4?24/56,42.9%?.The SI of MC was mainly isointense or hypointense on T₁ WI,hyperintense on T₂ WI,isointense or slightly hyperintense on DWI,and some of the bowel wall thickening type showed three layered structure like concentric circle or sandwich;After enhancement,the mucin part of tumor was delayed heterogeneous enhanced,the submucosal layer enhanced weak which appeared as intermediate space sign,the solid part was obviously sustained homogenous enhanced,postoperative pathological T stage was most T4?13/15,86.7%?.The SI of A-P was mainly isointense or hypointense on T₁ WI,slightly hyperintense on T₂ WI,hyperintense on DWI,and sustained enhancement on enhanced MRI.The mean ADC value of tumor was AC < A-P < MC,all the differences between AC and A-P,AC and MC,A-P and MC had statistically significant?P<0.01?.When the cut-off value was 1.23×10^-3 mm2/s,the sensitivity and specificity of ADC value to differentiate AC from A-P were 96.4% and 91.7%,respectively,and the area under the ROC curve was 0.971.When the cut-off value was 1.68×10^-3 mm2/s,the sensitivity and specificity of ADC value to differentiate A-P from MC were 93.3% and 100%,respectively,and the area under the ROC curve was 0.989.Conclusion:AC showed obvious hyperintense on DWI with lower ADC value,obvious and fast enhanced during arterial phase and decreased during the later phase with a vague or a rough edge,and local T stage was advanced.MC was hyperintense on T₂ WI with high ADC value,and its most common form was a long segment intestinal submucosa thickening with an intermediate space enhancement,and it was easy to invasion with adjacent structures or organs.A-P has an average ADC value of 1.30±0.21×10^-3 mm2/s which between that of AC and that of MC,and the most common form of A-P was a polypoid tumor protruding into the rectal lumen with abundant blood supply and a clear edge,and confined to the muscularis propria.