Rectal cancer: Short-term reproducibility of intravoxel incoherent motion parameters in 3.0T magnetic resonance imaging

Abstract

The aim of this study was to evaluate the short-term test-retest reproducibility of diffusion-weighted magnetic resonance imaging (DW-MRI) parameters of rectal cancer with 3.0T MRI.Twenty-six patients with rectal cancer underwent MRI, including diffusion-weighted imaging with 8 b values. Apparent diffusion coefficient (ADC) and intravoxel incoherent motion (IVIM) parameters (D, pure diffusion; f, perfusion fraction; D*, pseudodiffusion coefficient) were, respectively, calculated. The short-term test-retest reproducibility, the intra and interobserver variation of the IVIM parameters were assessed based on the repeatability coefficient and Bland-Altman limits of agreement.There was no significant intra or interobserver difference observed in the parameters on the same DW-MRI scan. The corresponding repeatability coefficient of intra- and interobserver analysis for ADC, D, f, and D* was 5.4%, 11.1%, 55.4%, and 40.3%; 10.9%, 41.6%, 134.0%, and 177.6%, respectively. The test-retest repeatability coefficient for ADC, D, f, and D* was 19.1%, 24.5%, 126.3%, and 197.4%, respectively, greater than the intraobserver values.ADC and D have better short-term test-retest reproducibility than f and D*. Considering the poor test-retest reproducibility for f and D,* variance in these 2 parameters should be interpreted with caution in longitudinal studies on rectal cancer in which treatment response and recurrence are monitored.

Figure 1

Twice-scanning images (including diffusion-weighted image [b = 1000 s/mm²], parametric IVIM color maps of rectal cancer [D, f, and D∗], plots of signal decay and biexponential fitting curves) of a 52-year-old male patient with middle-rectal cancer. Region of interests were manually drawn to contour the border of the rectal cancers on the slice (DWI images) with the maximum lesion size in twice-scanning. The upper line: the first examination images. The lower line: the second examination images.

Figure 2

Bland-Altman plot of repeatability of the DWI-derived parameters (ADC) for test and retest DWI imaging of rectal cancer. The horizontal full line represents the bias, and the dotted lines represent the 95% confidence interval. ADC = apparent diffusion coefficient, DWI = diffusion-weighted imaging, SD = standard deviation.

Figure 3

Bland-Altman plot of repeatability of the DWI-derived parameters (D) for test and retest DWI imaging of rectal cancer. The horizontal full line represents the bias, and the dotted lines represent the 95% confidence interval. ADC = apparent diffusion coefficient, DWI = diffusion-weighted imaging, SD = standard deviation.

Figure 4

Bland-Altman plot of repeatability of the DWI-derived parameters (f) for test and retest DWI imaging of rectal cancer. The horizontal full line represents the bias, and the dotted lines represent the 95% confidence interval. ADC = apparent diffusion coefficient, DWI = diffusion-weighted imaging, SD = standard deviation.

Figure 5

Bland-Altman plot of repeatability of the DWI-derived parameters (D∗) for test and retest DWI imaging of rectal cancer. The horizontal full line represents the bias, and the dotted lines represent the 95% confidence interval. ADC = apparent diffusion coefficient, DWI = diffusion-weighted imaging, SD = standard deviation.