Clinical Application Of Reduced Field-of-View Diffusion-Weighted Imaging(DWI) In The Assessment Of Rectal Carcinoma Invasiveness

Part? Comparison of Reduced Field-of-View Diffusion-Weighted Imaging(DWI)and Conventional DWI Techniques in the Assessment of Rectal Carcinoma at 3.0 T: Image Quality and Histological T StagingPurpose: To compare image quality(IQ)of reduced field-of-view(r FOV)and full FOV(f FOV)DWI sequences at 3 T,with histological T staging of rectal cancer as a reference standard.Materials and methods: 81 patients with rectal cancer received magnetic resonance(MR)scans(3.0 T),including both r FOV and f FOV DWI sequences.The signal-to-noise ratio(SNR)and contrast-to-noise ratio(CNR)were quantitatively evaluated using the paired t test.Two radiologists independently assessed subjective IQ parameters,including image sharpness,distortion,artifacts,lesion conspicuity and overall subjective IQ of both sequences.The Wilcoxon signed rank test was used to compare subjective IQ scores and tumor apparent diffusion coefficients(ADCs)between DWI sequences.Spearman correlation analysis was used to correlate ADC values and corresponding T staging of rectal cancer.The differences of sensitivity,specificity and accuracy from DWI and T2 WI sequences in assessment of rectal cancer were evaluated by the Mc Nemar test.The diagnostic performances of DWI and T2 WI sequences were analyzed by AUC,and the AUC values were compared by Z tests.Results: CNR was significantly higher in r FOV DWI than in f FOV DWI(7.15±2.77 vs.5.39±2.08,P<0.001).SNR was significantly higher in r FOV DWI than in f FOV DWI(44.17±11.01 vs.34.76±13.30,P<0.001).The subjective IQ parameters of r FOV DWI sequence were rated superior to those of f FOV DWI sequence by both readers(P<0.001).No significant differences between mean tumor ADC values of both sequences(0.991±0.121 vs.0.100±0.126×10-3 mm2/s,P=0.617)were noted.Apart from T1 stage,T staging of rectal cancer was inversely correlated with ADC values of r FOV DWI(r=-0.688,P<0.001)and f FOV DWI sequences(r=-0.641,P<0.001).The values of sensitivity and accuracy of T2WI+r FOV DWI sequence were significantly different from that of T2WI+f FOV DWI and T2 WI sequences respectively(P<0.05).The AUC value of T2WI+r FOV DWI sequence was significantly higher than that of T2WI+f FOV DWI and T2 WI sequences respectively(P=0.0002 and P=0.0005).Conclusion: rFOV DWI sequence provided significantly better IQ and lesion conspicuity than f FOV DWI sequence.In addition,r FOV and f FOV DWI sequences can be used in evaluation of histological T staging of rectal cancer.Based on the conventional MR scanning,the diagnostic performance of r FOV DWI was better than f FOV DWI in assessment of T staging of rectal cancerPart? Rectal Cancer Invasiveness:Whole-Lesion Diffusion-Weighted Imaging(DWI)Histogram Analysis by Comparison of Reduced Field-of-View and Conventional DWI TechniquesPurpose: To explore the efficacy of whole-lesion histogram analysis of apparent diffusion coefficient(ADC)for discriminating between histological T stages of rectal carcinoma by comparison of reduced field-of-view(FOV)and conventional DWI techniques.Materials and methods: 102 patients with rectal cancer were enrolled in this retrospective study.All patients received preoperative MR scan at 3T,including reduced and full FOV DWI sequences.Histogram parameters from two DWI methods were calculated and correlated with histological T stage of rectal cancer.The diagnostic performance of individual parameter for differentiating stage p T1-2 and p T3-4 tumors from both DWI techniques was assessed by receiver operating characteristic curve analysis.Results: There were significant differences for the parameters of ADCmean,50 th,75th,90 th,95th percentiles,skewness and kurtosis of both DWI sequences in patients with p T1-2 as compared to those with p T3-4 tumors(P<0.05),in addition to parameters including ADCmin(P=0.015)and 25 th percentile(P=0.006)from r FOV DWI.Correlations were noted between T staging and above histogram parameters from both DWI techniques.The correlation coefficients were-0.601,-0.582,-0.726,-0.741,-0.647,0.560,0.682 for r FOV DWI and-0.309,-0.356,-0.449,-0.424,-0.362,0.423,0.499 for f FOV DWI respectively,besides parameters of ADCmin(0.370)and 25 th percentile(-0.425)from r FOV DWI.The AUCs of 75 th and 90 th percentiles from r FOV DWI were significantly higher than that from f FOV DWI(P=0.0410 and P=0.0208 respectively).Conclusion: The 75 th and 90 th percentiles from r FOV DWI may be optimum for differentiating p T1-2 from p T3-4 stage of rectal cancer.The diagnostic performance of r FOV DWI is better than f FOV DWI in assessment of rectal cancer invasiveness.