Effect of region of interest on ADC and interobserver variability in thyroid nodules.

BACKGROUND: To determine the effect of region of interest (ROI) on tumor's apparent diffusion coefficient (ADC) and interobserver variability in thyroid nodules. METHODS: Thirty-three individuals with 45 pathologically-confirmed thyroid nodules were assessed by preoperative diffusion-weighted imaging (DWI) with b values of 0 and 400 s/mm2, respectively. Two readers evaluated the ADC values of lesions based on three ROI techniques: whole-volume, single-slice and small solid-sample groups. Interobserver variability was analyzed for all ROI techniques, and the mean ADCs of benign and cancerous thyroid nodules were compared. RESULTS: For the mean ADCs of non-cancerous thyroid nodules, average differences and limits of agreement (LOAs) between readers were 0.00 [- 0.17-0.17] × 10- 3 mm2/s for whole-volume ROI (ICC = 0.967), 0.00 [- 0.26-0.26] × 10- 3 mm2/s for single-slice ROI (ICC = 0.932) and - 0.02 [- 0.38-0.41] × 10- 3 mm2/s for small solid-sample ROI (ICC = 0.823). For the mean ADCs of cancerous thyroid nodules, average differences and LOAs between readers were - 0.05 [- 0.23-0.13] × 10- 3 mm2/s (ICC = 0.885), 0.01 [- 0.23-0.25] × 10- 3 mm2/s (ICC = 0.839) and - 0.07 [- 0.52-0.39] × 10- 3 mm2/s (ICC = 0.579) for the three ROI methods, respectively. The mean ADC values were more scattered in the small solid-sample ROI group in comparison with the whole-volume and single-slice groups, in noncancerous and cancerous specimens. Of all three ROI techniques, whole-volume ROI-determined ADC had the highest combined sensitivity (80.0%), specificity (88.3%) and Youden index (0.683), with a cut-off of 1.84 × 10- 3 mm2/s. CONCLUSIONS: The ROI method overtly affects ADC measurements in benign and cancerous thyroid nodules. Small solid-sample ROI yielded the worst interobserver variability of average ADC measurements.

[Functional MRI in chronic liver disease of hepatitis B patients].

OBJECTIVE: To estimate the correlations between functional MRI (fMRI) parameters and the severity of chronic liver lesions of hepatitis B patients. METHODS: 47 hepatitis B patients [6 with chronic hepatitis, 41 with cirrhosis (14 with Child-Pugh class A cirrhosis; 12 with class B cirrhosis; and 15 with class C cirrhosis)] and 10 normal volunteers, referred for measurements of apparent diffusion coefficient (ADC) values of the liver, perfusion imaging parameters, portal flow parameters and serum markers of hepatic fibrosis were included in the study. Diffusion-weighted imaging (DWI) with different b values and b value remainder was performed. Time to peak (TP), maximum slope of increase (MSI) and distribution volume (DV) were measured with dynamic contrast material-enhanced MR imaging. Portal velocity and portal flow with phase contrast (PC) were measured. The patients' serum hepatic fibrosis markers, including hyaluronic acid (HA), type-III-procollagen (PC III), laminin (LN) and type-IV-collagen (C IV), were measured and analyzed together with the fMRI results. RESULTS: (1) The mean ADC3 in Child A, B, C cirrhosis patients was significantly lower than that in the controls (P < 0.05 in Child A, and P < 0.05 in Child B). (2) There was a significant increase of time to peak and a decrease of maximum slope of increase (P < 0.01) in the Child A, B, C patients than in the normal controls. (3) There was a significant decrease in portal velocity in cirrhotic patients as compared to that of the controls and chronic hepatitis patients (P < 0.01). (4) The mean HA in Child A, B, C cirrhosis patients was significantly higher than that in chronic hepatitis patients and in the controls (P < 0.01); The mean LN in Child A, B, C cirrhosis was also significantly higher than that in chronic hepatitis patients and in normal controls (P < 0.01); The mean PC III in Child A, B, C cirrhosis was significantly higher than that in the normal controls (P < 0.01). CONCLUSION: fMRI parameters can reflect some changes of the livers, therefore fMRI parameters are of value in clinical diagnosis and treatment of chronic hepatitis B patients.