The Applied Research Of Diffusion Weighted Imaging Quantitative Assessment In The Staging And Grading Of Rectal Cancer

Objective：1. To assess the value of diffusion-weighted imaging (DWI) in combination withT2-weighted imaging (T2WI) for diagnosing the T-staging and N-staging of rectal cancer.2. To assess the value of apparent diffusion coefficient of clinic, pathology andprognosis in patients with rectal cancer.3. Preliminary study of intravoxel incoherent motion imaging in reflecting tissuemicrocapillary perfusion and tissue diffusivity between rectal cancer and normal rectalwall.Methods：1. The T2WI and DWI findings of58patients with pathological proved rectaladenocarcinoma were retrospectively analyzed, T-staging and N-staging of rectal cancerdiagnosed by T2WI alone and DWI with T2WI were perform a comparison with ofpathology.2. The MRI and DWI findings of109patients with pathological proved rectal adenocarcinoma were retrospectively analyzed. DWI with b=0s/mm2and b=1000s/mm2were acquired. Mean tumor ADCs were measured and compared between subgroupsstratified by histologic differentiation grades, T-stage, N-stage, mesorectal fascia statusand presence of lymphangiovascular or perineral invasion.3. DWI was performed in28patients with pathological proved good-moderatedifferentiated and moderate differentiated rectal adenocarcinoma using different b-value（0,50,100,150,200,500,800and1000s/mm2）, the diffusion coefficient D and theperfusion fraction f derived from intravoxel incoherent motion with bi-exponential modelin rectal cancer group and normal rectal wall group were calculated and compared, ADCin rectal cancer group and normal rectal wall group were measured in DWI with b=0s/mm2and b=1000s/mm2.Results：1. T-staging and N-staging of rectal cancer diagnosed by T2WI alone agreed withpathological stage were both70.1%（k=0.518for T-staging，k=0.534for N-staging）,17cases were diagnosed wrong in T-staging,9overstaged were and8understaged,17caseswere diagnosed wrong in N-staging,8overstaged were and9understaged. T-staging andN-staging of rectal cancer diagnosed by DWI with T2WI agreed with pathological stagewere higher than T2WI alone,79.3%（k=0.662）for T-staging and74.1%（k=0.586）forN-staging,12cases were diagnosed wrong in T-staging,7overstaged were and5understaged,15cases were diagnosed wrong in N-staging,8overstaged were and7understaged.2. Mean tumor ADCs were significantly different when comparing groups stratifiedby histologic differentiation grades, T-stage, mesorectal fascia status and presence oflymphangiovascular invasion. Tukey’s post hoc test showed that the differences of meanADCs between good-moderate differentiated group and moderate differentiatedgroup(P=0.996), moderate-poor differentiated group and poor differentiatedgroup(P=0.957) were not significant.The differences among other groups of differentiationgrades differed significantly(P＜0.05).In the T-stage groups, the mean ADCs of T1stagetumor was significantly higher than that of T3stage tumor(P＜0.05).There were no significant differences among other T-stage groups(P＞0.05). There were no significantdifferences among N0, N1and N2in N-stage groups.3. f, D and ADC in rectal cancer group and normal rectal wall group were10.65(±4.83)%versus15.56(±7.88)%,0.909(±0.131)×10-3mm2/s versus1.287(±0.128)×10-3mm2/s and0.981(±0.096)×10-3mm2/s versus1.393(±0.113)×10-3mm2/s, thedifferences all differed significantly(P=0.005, P=0.000and P=0.000), D in rectal cancergroup and normal rectal wall group were both lower than ADC.Conclusion：1. The addition of DWI to T2WI provides better preoperative diagnosis of T-stagingand N-staging in rectal cancer, DWI is an important auxiliary means in preoperativestaging of rectal cancer.2. ADC values can reflect pathologic and prognostic features of rectal cancer.3. IVIM imaging could show the signal attenuation pattern of rectal cancer, andprovide diffusion and perfusion characteristics of rectal cancer.