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Objective@#To evaluate the value of T2WI signal intensity related parameters that can be obtained by magnetic resonance imaging (MRI) for predicting pathological complete response (pCR) after neoadjuvant chemoradiotherapy (nCRT) in patients with locally advanved rectal cancer (LARC).@*Methods@#Signal Intensity of Tumor (SIT) and Signal Intensity of Tumor/Muscle (SIT/M) of MR T2WI before and after neoadjuvant chemoradiotherapy of 101 patients with locally advanced rectal cancer were evaluated by two experienced readers independently. Signal Intensity of Tumor Reduction Rate (SITRR) and Signal Intensity of Tumor/Muscle Reduction Rate (SIT/MRR) were calculated. The difference of related parameters of T2WI tumor signal intensity between the pCR and the non-pCR group were analyzed. Receiver operating characteristic (ROC) analysis was used to assess the diagnostic performance for predicting pCR.@*Results@#Of the 101 patients, 18 were in pCR group and 83 were in non-pCR group. In all patients, the SITpre, SITpost, SITRR, SIT/Mpre, SIT/Mpost and SIT/MRR measured by reader 1 were 197.0 (133.0), 144.2 (69.7), 0.4% (0.5%), 2.6 (0.6), 3.0 (2.3) and 0.4 (0.2)% in pCR group, and 227.0 (99.0), 205 (95.4), 0.1% (0.6%), 2.6 (0.6), 2.6 (1) in non-pCR group, respectively. SITpre, SITpost, SITRR, SIT/Mpre, SIT/Mpost and SIT/MRR measured by reader 2 were 193.0 (135.0), 143.0 (69.8), 0.4% (0.2%), 2.6 (0.6), 1.5 (0.5) and 0.39% (0.2%) in pCR group, and 234.0(108.0), 203(96.5), 0.1% (0.3%), 2.6 (0.6%), 1.7 (0.7) and 0.25% (0.2%) in non-pCR group, respectively. Between the pCR and non-pCR group, there were significant differences in SITpost, SIT/Mpost and SIT/MRR measured by both readers (all P<0.01), but there was no significant differences in SITpre and SIT/Mpre (P>0.05). The difference of SITRR measured by reader 1 was not statistically significant (P=0.415), while the difference of SITRR measured by reader 2 was statistically significant (P=0.001). In patients with rectal non-mucinous adenocarcinoma, SITpost, SIT/Mpost, SITRR and SIT/MRR measured by two physicians were still statistically significant between the pCR and non-pCR group (all P<0.01), but SITpre and SIT/Mpre had no significant difference (P>0.05). ROC curve analysis showed that in all patients, the area under curve (AUC) of SITpost, SIT/Mpost and SIT/MRR for predicting pCR to neoadjuvant chemoradiotherapy in locally advanced rectal cancer was 0.694-0.762, the sensitivity was 68.2%-77.3%, and the specificity was 63.6%-77.3%. In rectal non-mucinous adenocarcinoma patients, the AUC, sensitivity and specificity was 0.704-0.764, 62.7%-78.9% and 66.2%-84.2%, respectively.@*Conclusions@#T2WI signal intensity related parameters are potential predictors for pCR in locally advanced rectal cancer after neoadjuvant chemoradiptherapy. The predictive value is higher in non-mucinous adenocarcinoma.
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Objective@#To compare the diagnostic value of T2 weighted imaging (T2WI), diffusion-weighted imaging (DWI), and T2WI+ DWI magnetic resonance imaging (MRI) for staging of rectal cancers for improving the accuracy of tumor staging.@*Methods@#From January 2011 to December 2013, 120 cases of rectal cancers proved by colonoscopy without receiving any anti-tumor treatment were enrolled retrospectively. The MRI data for these patients were divided into three groups, ie., T2WI, DWI and T2WI+ DWI, for evaluating the tumor stages. The results were compared with histopathologic findings. The sensitivity and specificity were calculated and compared with chi-square test. The nodal staging was predicted by using T2WI+ DWI.@*Results@#The accuracy for prediction of tumor staging was 83.3%, 65.0% and 92.5% for T2WI, DWI, and T2WI+ DWI respectively. The specificity for evaluating T1 and T2 stage, and the sensitivity for evaluating T3 by DWI was significantly lower than those using T2WI and T2WI+ DWI in rectal cancers. The sensitivity for evaluation of T2 by DWI was lower than that using T2WI+ DWI (63.0% vs. 88.9%). The sensitivity for evaluation T2 and specificity for T3 by T2WI+ DWI was higher than thouse using T2WI only (88.9% vs. 51.9%, 94.0% vs. 72.0%). The accuracy for prediction of nodal staging by using T2WI+ DWI was 62.1% (72/116).@*Conclusions@#T2WI is the key sequence for staging of rectal cancers. Although the diagnostic accuracy was not good by using DWI alone, the combination of T2WI and DWI can improve the accuracy significantly for tumor staging in rectal cancers, whereas the nodal staging was still a hard task for radiologists.
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Objective To compare the predictive value of radiomics signature extracted from MRI plain and enhancement sequence for the disease-free survival (DFS) of rectal cancer. Methods We retrospectively analyzed fifty-one patients with rectal adenocarcinoma confirmed by biopsy from October 2010 to December 2013 in Cancer Hospital Chinese Academy of Medical Sciences.All patients underwent neoadjuvant chemotherapy(nCRT)followed total mesorectal excision(TME),and MRI scans were performed before nCRT.Follow-up time for the survival patients were more than 3 years.The image segmentation was performed on the T2WI sequence of the small FOV and the multi-phase enhancement sequence venous phase,respectively.Least absolute shrinkage and selection operator(LASSO)Cox regression was applied to extract radiomics features and the imaging signature was constructed. According to the radiomics score of each patient,the patients were divided into the high risk group with shorter DFS and the low risk group with longer DFS. A 3-year DFS was calculated for radiomics signature using the Kaplan-Meier product limit method with univariate log-rank analysis testing for differences in the training and validation cohort, respectively. And the predictive ability of the model was evaluated by concordance index (C-index). Results The training set and the validation set were 36 and 15 cases, respectively. During follow-up 32 patients experienced relapse(26 distant,3 local and 3 both),and 19 cases were censored.Twelve features were extracted in the enhanced sequence.The radiomics signatures were significant for DFS in the training set and the validation set(P=0.000 2 and 0.009 1,respectively).The C-index of the model were 0.904 and 0.700 in the training set and the validation set, respectively. The model has the better ability to predict survival.Two features were extracted in the plain sequence.The radiomic signature was significant for DFS in the training set(P=0.005 0),while the radiomics signature was not significant for DFS in the validation set (P=0.767 0). The C-index of the model were 0.711 and 0.500 in the training set and the validation set, respectively.Conclusions Radiomics signature extracted from MRI venous phase enhancement sequence superior to plain sequence for predicting the DFS of rectal cancer before nCRT.
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Objective@#To study the measurement reproducibility of parameters derived from introvoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI)-MRI of rectal cancer between- and within- radiologists.@*Methods@#Clinical data of 34 patients with rectal cancer were prospective analyzed. Conventional MRI sequences, IVIM DWI-MRI with sixteen b values and dynamic contrast enhancement (DCE)-MRI sequences of rectum were acquired by GE 3.0-T MRI imager. The IVIM sequence images with b value=1000 sec/mm2 were selected to measure the maximum axial section of tumor by a radiologist with 15 year-experiences in gastrointestinal cancer imaging.Two radiologists (radiologist 1 and radiologist 2 with 2 and 10 years of experience in gastrointestinal cancer imaging, respectively) independently draw a freehand region of interest (ROI) that contained the largest available tumor area on the selected section. Monoexponential apparent diffusion coefficient (ADC) and biexponential IVIM metrics maps and IVIM parameters were generated automatically by the software. The repeated measurement was performed at an interval of one week. The average values of each measurement were used for statistical analysis. ADC values and IVIM parameters obtained between- and within- radiologists were analyzed by Wilcoxon signed-rank test. Intraclass correlation coefficients (ICC) and Bland-Altaman plots were used to analyze the parameter reproducibility of two measurements between- and within- radiologists.@*Results@#The first and second measured ADC (×10-3mm2/s), true diffusivity (D, ×10-3mm2/s), false diffusivity (D*, mm2/s) and perfusion fraction (f, %) by radiologist 1 were 0.997, 0.692, 0.043, 34.6 and 0.993, 0.691, 0.038, 32.8, respectively. The first and second measured ADC (×10-3mm2/s), D (×10-3mm2/s), D* (mm2/s), f (%) by radiologist 2 were 0.987, 0.651, 0.046, 32.8 and 0.996, 0.689、0.041, 32.7, respectively. No statistically significant differences were observed in ADC and IVIM parameters obtained between- and within- radiologists (P>0.05). The ADC values and the f values of two times were significantly correlated between- and within- radiologists. The D values were significantly correlated within a radiologist, and the correlation of D* values within a radiologist was significantly higher than that between radiologists. The 95% limits of agreement (LoA) of ADC values and f values were smaller than those of D values and D* values between- and within- radiologists. The 95% LoA of ADC values was the least, while that of D* values varied most.The 95% LoA of f values and D values kept steady within a radiologist, and 95% LoA of f values was slightly smaller than that of D values. The 95% LoA of IVIM parameters (ADC, D, f, D* values) within radiologists 2 were better than those within radiologist 1.@*Conclusions@#The reproducibilities of ADC and f values are the best, while the reproducibility of D* values is relatively poorer in rectal cancer. Measurement reproducibility of parameters derived from IVIM may be improved by increasing radiologists’ experiences in drawing ROI.
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Objective To evaluate the value of MRI texture analysis (TA) in prediction of treatment response neoadjuvant chemoradiotherapy (nCRT) in locally advanced rectal cancer patients. Methods Fifty nine histopathologically-proven rectal adenocarcinoma patients through biopsy treated with nCRT before total mesorectal excision were enrolled in this retrospective study.The first MRI examination (pre-nCRT MRI)was performed before nCRT,and the second one(early nCRT MRI)was performed at the third week of nCRT. The texture parameters values were measured, including mean value, standard deviation, skewness, kurtosis, uniformity, energy, and entropy. Tumoral downstaging was determined by comparing the pre-nCRT clinical T stage(cT stage) with the ypT stage. The patients were divided into downstaging and non downstaging group based on postoperative T staging. Parameters were compared between pre-and early nCRT in terms of averages using Wilcoxon signed-rank test. Downstaging and non downstaging groups were analyzed using Mann-Whitney U test.Multivariate logistic regression analysis was performed using the statistically significant parameters between the two groups as independent variables. ROC analysis was performed on the new independent variables obtained by multi-parameter logistic regression analysis and the single parameter independent variables. The diagnostic efficiency of the parameters were evaluated. Results T-downstaging were found in 28 patients after nCRT. The stdDeviation, kurtosis, and uniformity were significantly different between pre-and early nCRT (P<0.05). There was no significant difference in mean value, skewness, energy, and entropy between pre-and early nCRT (P>0.05). The pre-nCRT, uniformity, energy, entropy and the early nCRT mean value, entropy were significantly different in patients with downstaging vs. non downstaging (P<0.05). For the pre-nCRT stdDeviation,uniformity,energy,entropy and the early nCRT mean value,entropy,ROC analysis showed an area under curve(AUC) of 0.69, 0.76, 0.68, 0.67 and 0.65, 0.68, respectively. The multivariate logistic regression analysis for the four pre-nCRT independent variables(stdDeviation,uniformity,energy,entropy) achieved logical variable 1,and the logical variable 1 achieved an AUC of 0.78 to discriminate patients with T-downstaging from patients with non downstaging.The multivariate logistic regression analysis for the two early nCRT independent variables(mean value,entropy)achieved logical variable 2,and the logical variable 2 achieved an AUC of 0.69 to predict T-downstaging.Conclusion Pre-and early nCRT MRI TA in rectal cancer have the efficacy to predict treatment response.