ABSTRACT
Objective To determine the measurement consistency of diffusion coefficient D, perfusion fraction f and pseudodiffusion coefficient D*in rectal cancers based on different ROIs. Methods Forty-three patients with histologically proven rectal cancers were examined using echo-planar DW-MRI with eight b values (0 to 1 000 s/mm2). Intravoxel incoherent motion parameters were measured on intravoxel incoherent motion map that contained the largest tumor cross-section, according to two distinct ROI protocols:freehand outline ROI and semi-automatic tumor center ROI. The two protocols were compared for differences in IVIM parameters and the interclass correlation coefficient (ICC) were also calculated. intra-and inter-observer variability using paired t test and Bland-Altman plot. Results The IVIM parameters(D, f and D*) obtained by ROIs for outlined and center analysis were (1.08 ± 0.24) × 10-3mm2/s, (0.16 ± 0.06), (26.59 ± 19.54) × 10-3mm2/s and (1.06 ± 0.27) × 10-3mm2/s, (0.17 ± 0.07), (30.79 ± 20.85) × 10-3mm2/s, respectively. No significant differences were observed between the means of the IVIM parameters (D, f, D*) calculated by the two methods (t=1.113,-0.259,-1.660;P=0.272, 0.797,0.104, respectively),and the relative ICC were 0.863, 0.469, 0.663, respectively. The intra-observer 95% limits of consistency of IVIM parameters were (-0.012—0.038) × 10-3mm2/s, (-0.003—0.007), (-0.923—1.166) × 10-3mm2/s with ROI outline tumor, respectively;(-0.024—0.044)×10-3mm2/s, (-0.005—0.015), (-1.670—4.195)×10-3mm2/s with center ROI, respectively. The inter-observer 95% limits of consistency of perfusion parameters were (-0.047—0.009) × 10-3mm2/s, (-0.015—0.009), (-7.206—3.190) × 10-3mm2/s with ROI outlined tumor, respectively;(-0.068—0.048) × 10-3mm2/s, (-0.005—0.041), (-17.657—0.779) × 10-3mm2/s with center ROI, respectively. Conclusions There was no statistically significant difference between the outlined ROI and tumor center ROI analysis of rectal cancers' IVIM parameters. The tumor analysis by outlined ROI protocol appropriately improves intra-and inter-observer consistency and can provide more reproducible and stable results.
ABSTRACT
Objective To determine the consistency between quantitative CT perfusion measurements of colorectal cancer obtained from single section with maximal tumor dimension and from average of whole tumor,and compare intra-and inter-observer consistency of the two analysis methods.Methods Twenty-two patients with histologically proven colorectal cancer were examined prospectively with 256-slice CT and the whole tumor perfusion images were obtained.Perfusion parameters were obtained from region of interest (ROI) inserted in single section showing maximal tumor dimension,then from ROI inserted in all tumor-containing sections by two radiologists.Consistency between values of blood flow (BF),blood volume (BV) and time to peak (TTP) calculated by two methods was assessed.Intra-observer consistency was evaluated by comparing repeated measurements done by the same radiologist using both methods after 3 months.Perfusion measurements were done by another radiologist independently to assess inter-observer consistency of both methods.The results from different methods were compared using paired t test and Bland-Altmnan plot.Results Twenty-two patients were examined successfully.The perfusion parameters BF,BV and TTP obtained by whole tumor perfusion and single-section analysis were (35.59 ± 14.59) ml · min-1 · 100 g-1,(17.55 ±4.21) ml · 100 g-1,(21.30 ±7.57) s and (34.64 ± 13.29)ml· min-1 · 100 g-1,(17.61 ±6.39)ml± · 100 g-1,(19.82 ±9.01)s,respectively.No significant differences were observed between the means of the perfusion parameters (BF,BV,TTP)calculated by the two methods (t =0.218,-0.033,-0.668,P ＞ 0.05,respectively).The intra-observer 95％ limits of consistency of perfusion parameters were BF-5.3％ to 10.0％,BV-13.8％ to 10.8％,TTP-15.0％ to 12.6％ with whole tumor analysis,respectively; BF-14.3％ to 16.5％,BV-24.2％ to 22.2％,TTP-19.0％ to 16.1％ with single section analysis,respectively.The inter-observer 95％ limits of consistency of perfusion parameters were BF-8.0％ to 8.3％,BV-10.9％ to 11.5％,TTP -14.5％ to 11.1％ with whole volume analysis,respectively; BF-10.2％ to 14.1％,BV-19.0％ to 17.6％,TTP-22.0％ to 24.0％ with single section analysis,respectively.Conclusion There was no statistically different between the single section and whole volume analysis of tumor perfusion CT.The whole volume perfusion analysis apparently improves intra-and inter-observer consistency and can reflect the whole tumor angiogenesis more accurately and repeatedly.