The Value Of Magnetic Resonance Imaging In The Preoperative Diagnosis Of Rectal Cancer

Part 1 The value of apparent diffusion coefficient in the staging of preoperative primary rectal cancerObjective:To explore the performance of apparent diffusion coefficient?ADC?value in the T staging of preoperative primary rectal cancer.Material and Methods:MRI including T2-weighted imaging?T2WI?and diffusion-weighted magnetic resonance imaging?DWI?of 34 surgically resected rectal cancer in33 patients were retrospectively analyzed.Pathologic examinations revealed 15 T1?T2?Group A?and 19 T3?T4?Group B?rectal cancers.Two experienced radiologists reviewed images and classified T stages of tumor on T2WI by mutual agreement.The diagnostic sensitivity,specificity,positive predictive value?PPV?and negative predictive value?NPV?of T2WI in T staging were evaluated.Two experienced radiologists drew regions of interest?ROI?on the DWI images and ADC map to calculate mean ADC value of each tumor,and interobserver agreement between the two radiologists was calculated.Receiver operating characteristic analysis was performed for ADC value.ROC curve was used to analyze and compare the difference of ADC value and T2WI in differentiating T1?2 group and T 3?4 group..Results:On T2WI,the specificity,sensitivity,PPV and NPV was 40%,100%,100% and 67.7% respectively.The mean ADC value of Group A was?1.102±0.173?*10^-3mm²/s,which is statistically higher than that in Group B of 0.880±0.008*10^-3mm²/s?p<0.05?,and the interobserver agreement is perfect with intraclass correlation coefficient?ICC?being 0.853.The area under curve?AUC?of ADC was 0.902,sensitivity 84.2%and specificity 86.7%.The ADC threshold for differentiating Group A from Group B was 0.923*10^-3mm²/s.The difference in T staging between T2WI and ADC value is statistically significant?p<0.05?.Conclusion:Compared to traditional T2WI,ADC value can be used to improve the specificity in judging whether the lesion is involved the muscularis propria layer or not.Part 2 A Diffusion Kurtosis Imaging Study of Rectal Adenocarcinoma Association with Histopathologically Prognostic Factors: Preliminary FindingsPurpose: To evaluate the correlation between diffusion kurtosis imaging?DKI?-derived parameters and prognostic factors for rectal adenocarcinoma.Materials and Methods: This study was approved by the local institute review board,and written informed consent was obtained from each patient.Data from 56 patients?median age: 59.5 years;range,31-86 years?with rectal adenocarcinoma between April 2014 and September 2015 were finally involved in this prospective study.DKI?b = 0,700,1400,2100 sec/mm²?and conventional diffusion-weighted imaging?DWI??b = 0,1000 sec/mm²?were performed.Kurtosis and diffusivity from DKI and apparent diffusion coefficients?ADC?from DWI were measured by two radiologists.Student's t test,receiver operating characteristics curves?ROC?and Spearman correlation were used for statistical analysis.Results: Kurtosis was significantly higher in high-grade than in low-grade rectal adenocarcinomas based on both the number of poorly differentiated clusters?PDCs??1.136±0.086 vs 0.988±0.060,respectively;p<0.05?and WHO grades?1.103±0.086 vs 1.034±0.103,respectively;p<0.05?.In PDC grading,the diffusivity and ADC were significantly lower in high-grade tumors than in low-grade tumors?1.187±0.150 vs 1.306±0.129 and 1.020±0.113 vs 1.108±0.097,respectively;p<0.05?and showed similar correlations with histologic grades?r=-0.486 and r=-0.406,respectively;p>0.05?.Compared to both diffusivity and ADC,kurtosis showed significanly higher specificity [83.3%?20/24?vs 70.8%?17/24?and 70.8%?17/24?,respectively] and sensitivity [96.8%?31/32?vs 84.4%?27/32?and 81.3%?26/32?,respectively].Kurtosis showed a better correlation with PDC grades than with WHO grades?r=0.797 vs r=0.293,respectively;p<0.05?.Kurtosis was significant higher in pN1-2 than in pN0 tumors?1.086±0.103 vs 1.009±0.086,respectively;p<0.05?.Conclusion: Kurtosis derived from DKI demonstrated a higher correlation with histologic grades compared to diffusivity and ADC.It also showed better performance in differentiating between high-and low-grade rectal adenocarcinomas and between pN1-2 and pN0 tumors.Part 3 The correlation between ADC value derived from multi-b values diffusion weighted imaging and prognosis factors of rectal cancerObjective:To explore correlation between ADC value derived from multi-b values diffusion weighted imaging and prognosis factors of rectal cancer.Materials&Methods:Between January 2015 and July 2015,48 patients pathologically proven rectal adenocarcinoma were selected for MR imaging during almost seven days before surgery.Magnetic Resonance imaging?MRI?protocols included T2-Weighted MRI and conventional diffusion-weighted MRI?DWI?at b values of 0,1000 sec/mm² and DWI at b values of 0,700,1400,2100 sec/mm².ADC values from conventional DWI and mean ADC values?mADC?from multi-b values of tumor were measured by two blinded experienced radiologists and compared to prognostic factors including T staging,N staging,and grading according to both World Health Organization?WHO?standard and standard based on numbers of poorly differentiated clusters.And interobserver agreement between the two radiologists was calculated.Results:Among 48 patients,4 were diagnosed to be T1 tumors,10 were T2 tumors,29 were T3 tumors and 5 were T4 tumors.24 patients were staged as N0,13 were N1 while others were N2.Pathologic examinations according to WHO grading standard revealed 0 G1,37 G2 and 11 G3 tumors.Tumors were classified as G1,G2 and G3?n=11,16 and 21?respectively based on numbers of poorly differentiated clusters.The ADC values and mADC values were different in the same patient respectively?p<0.05?.The ADC values and mADC values of different T stages and N stages were not equal though not statistically significant?p>0.05?.Correlations between both ADC values and mADC values and grades based on WHO standard were not significantly different?p>0.05?,while there were significant negative correlations between both ADC values?r=-0.569?and mADC?r=-0.826?values and grades based on numbers of poorly differentiated clusters.And two correlation coefficients were different respectively?p<0.05?.The interobserver agreements of both ADC values and mADC values were perfect with intraclass correlation coefficient?ICC?being 0.992 and 0.995.Conclusion:There were significant negative correlations between both ADC values and mADC values and grades based on numbers of poorly differentiated clusters,of which the correlation between mADC and grades based on numbers of poorly differentiated clusters was signififcantly higher.