| Part ⅠApplication of assessment in T stage of rectal cancer using diffusion-weighted ImagingObjective: To explore the application value of diffusion-weighted imaging(DWI) in the preoperative T staging of rectal cancer. High-resolution T2 WI and high-resolution T2 WI combined DWI were obtained respectively to determine T staging of rectal cancer, including T3 stage, and comparing the two imaging methods in the accuracy of the preoperative T staging diagnosis of rectal cancer.Methods: 46 cases of rectal cancer without preoperative adjuvant radiation and chemotherapy were analyzed. All patients were imaged with a 3.0-T MRI system using a sixteen-channel phased-array surface coil. The standard imaging protocol consisted of routine pelvic axial T1-weighted fast spin echo and T2-weighted fat-suppressed, sagittal, axial and coronal high-resolution T2 WI fast spin echo. Axial diffusion-weighted images adopted SE-EPI sequence and b value was 0, 1000 s/mm2. T stage is divided into T1- T4. The T3 stage was further classified into T3a(<5mm), T3b(5-10mm), T3c(>10mm). All images were evaluated by two radiologists. Two radiologists interpret high-resolution T2 WI alone and identify T stage of tumor. More than 2 weeks after the first reading, the two readers reviewed high-resolution T2 WI combined with DWI and identify T stage of tumor. The sensitivity, specificity, and accuracy of T stage by high-resolution T2 WI alone and high-resolution T2 WI combined with DWI were calculated. Differences in diagnostic accuracy, sensitivity and specificity for each image set were evaluated with the χ2 test.Results:(1) The histopathologic examination revealed 10 p T2 stage, 12 p T3 astage, 14 p T3 bstage, 4 p T3 cstage and 6 p T4 stage tumors.(2) The accuracy of T2 stage, T3 a stage, T3 b stage, and T3 c stage were 82.6%, 69.6%, 80.4%, and 97.8% respectively by high-resolution T2 WI alone. The accuracy of T2 stage, T3 a stage, T3 b stage, and T3 c stage were 91.3%, 76.1%, 84.8%, and 100% respectively by high-resolution T2 WI combined with DWI. The accuracy of two image sets in the diagnosis of T4 stage was 100%.The overall accuracy of two image sets was 65.2%and 76.1%respectively.(3) The difference insensitivity, specificity, and accuracy of T3 c and T4 stage were not evaluated due to 100%. There were no significant differences in accuracy of T2 stage, T3 a stage, and T3 b stage between the two image sets(P=0.108,0.482,0.582 respectively).There was no significant difference in overall accuracy of two image sets(P=0.252).There were no significant differences in sensitivity of T2 stage, T3 a stage, and T3 b stage between the two image sets(P=0.329、0.408、0.699 respectively).There were no significant differences in specificity of T2 stage, T3 a stage, and T3 b stage between the two image sets(P=0.394、0.770、0.641 respectively).Conclusion: High-resolution T2 WI combined with DWI can improve the accuracy of MRI in T stage of rectal cancer. Compared with high-resolution T2 WI alone, there was no significant difference in accuracy. But there were two following clinical significance, the first side, DWI can effectively differentiate T2 stage from T3 a stage tumors, the second side, DWI identified direction that tumor breakthrough the muscularis propria and into the mesorectum and correctly measured extramural depth(EMD) on High-resolution T2 WI combined with DWI.PartⅡ Apparent diffusion coefficient value of DWI for rectal cancer:correlation with routinal histological featuresObjective: To evaluate the value of DWI as a potential noninvasive marker of tumor aggressiveness in rectal cancer, by analyzing the relationship between the pre-treatment tumorous apparent diffusion coefficient(ADC) and routinal histological features.Methods: 46 cases of rectal cancer without preoperative adjuvant radiation and chemotherapy were analyzed. All patients were imaged with a 3.0-T MRI system using a sixteen-channel phased-array surface coil. The standard imaging protocol consisted of routine pelvic axial T1-weighted fast spin echo and T2-weighted fat-suppressed, sagittal, axial and coronal high-resolution T2 WI fast spin echo and axial diffusion-weighted images. The routinal histological features were p T stage, p N stage, tumor differentiation grade, EMD, and invasion of the mesorectal fascia(MRF) status. The T3 stage was further classified into T3a(<5mm), T3b(5-10mm), T3c(>10mm). Statistical analyses were used to assess differences of mean ADC values between different histological features. In addition, Receiver operating characteristic curve(ROC) analysis was performed, and the diagnostic cutoffs of the ADC values, to distinguish between T stage(T2-3a VS T3b-4), N stage(N0 VS N1-2), EMD(<5mm VS ≥5mm), MRF status(free or involved), and tumor differentiation grade(well differentiated VS non-well differentiated) according to prognosis.Results:(1) With the increase of T stage, N stage, and the EMD, the mean ADC values gradually reduce. There was no significant difference between these different group. The diagnostic cutoffs of the ADC values to distinguish T2-3a was 0.934×10-3mm2/s, and area under the curve(AUC) was 0.819.The diagnostic cutoffs of the ADC values to distinguish N0 was 0.97×10-3mm2/s, and AUC was 0.800.The diagnostic cutoffs of the ADC values to distinguish EMD<5mm was 1.106×10-3mm2/s, and AUC was 0.692.(2) With the decrease of tumor differentiation grade, the mean ADC values gradually reduce. There was no significant difference between differentiation grades. The diagnostic cutoffs of the ADC values to distinguish well differentiated was 0.976×10-3mm2/s, and AUC was 0.793.(3) The mean ADC value of MRF status free was higher than that of MRF status involved. There was significant difference between MRF status. The diagnostic cutoffs of the ADC values to distinguish well differentiated was 0.97×10-3mm2/s, and AUC was 0.792.Conclusion: Lower ADC values were associated with more aggressive tumor behavior. Significant correlations were found between mean ADCs and p T stage, p N stage, differentiation grade, EMD, and MRF status. ADC value may represent a useful biomarker for assessing the routinal histological features of rectal cancer.PartⅢ Apparent diffusion coefficient value of DWI for rectal cancer:correlation with angiogenesisObjective: To evaluate the correlation of tumour ADC values with microvessel density(MVD) and vascular endothelial growth factor(VEGF) in rectal cancer.Methods: 46 cases of rectal cancer without preoperative adjuvant radiation and chemotherapy were analyzed. All patients were imaged with a 3.0-T MRI system using a sixteen-channel phased-array surface coil. The standard imaging protocol consisted of routine pelvic axial T1-weighted fast spin echo and T2-weighted fat-suppressed, then sagittal, axial and coronal high-resolution T2 WI fast spin echo, last axial diffusion-weighted images. All cases achieved complete postoperative pathological results, including immune histochemical methods of MVD and VEGF. Statistical analyses were used to assess correlation of MVD and VEGF, correlation of tumour mean ADC values with MVD and VEGF, and differences of MVD and VEGF between different histological features.Results:(1) With the increase of T stage, N stage, and decrease of tumor differentiation grade, the MVD gradually increase. There was significant difference between different N stage, and There was no significant difference between different T stage and differentiation grade.(2) VEGF staining was found in 38 of 46 tumors(82.6%). Mean score of VEGF expression was 3.51±1.13.With the increase of T stage, N stage, and decrease of tumor differentiation grade, the mean score of VEGF expression gradually increase. There was significant difference between different differentiation grade. In addition, there was correlation between MVD and VEGF.(3) In this study, With the increase of MVD and Mean score of VEGF expression, the mean ADC values gradually decrease. The mean ADC values showed correlation with the MVD and Mean score of VEGF expression.Conclusion: MVD and VEGF expression may reflect histological features of rectal cancer. Tumour mean ADC values may reflect angiogenic activity of rectal cancer. |
PDF Full Text Request