Abstract
Purpose: To evaluate the apparent diffusion coefficient (ADC) test-retest repeatability of the normal pancreas based on diffusion-weighted imaging (DWI).Methods: Twenty-six healthy volunteers (mean 47.6 years; 13 men) were included and scanned twice with reposition for a DWI sequence at 3.0-T. Two readers measured the ADCs of pancreatic head, body and tail for two DWIs, independently. The mean ADCs of the pancreatic head, body and tail were calculated as the global pancreatic ADC. Test-retest repeatability and agreement of ADC measurement were evaluated by the Bland-Altman analysis, intra-class correlation coefficient (ICC) and coefficient of variation (CV).Results: The global pancreatic ADC showed the best test-retest repeatability (mean difference ± limits of agreement were 0.05 ± 0.25×10-3 mm2/s; ICC, 0.79; CV, 6%). Test-retest repeatabilities for ADC of pancreatic head, body or tail were scattered, with mean difference ± limits of agreement between two tests were 0.03 ± 0.47, 0.05 ± 0.42 and 0.06 ± 0.31 (×10-3 mm2/s) (ICCs, 0.81, 0.52 and 0.68; CVs, 9%, 8% and 8%), respectively. Both intra-observer repeatability and inter-observer reproducibility were acceptable for global pancreatic ADC between measurements of the two DWIs.Conclusions:The best test-retest repeatability of ADC in the normal pancreas was only for the whole pancreas with a CV of 6%. Cautions should be taken in interpreting longitudinal clinical changes in ADC values of the normal pancreas for the measurements do have an inherent variability by locations.
Highlights
Magnetic resonance imaging (MRI) is an important tool for the diagnosis and evaluation of various abdominal diseases with quantitative and qualitative methods
The mean coefficient of variation (CV) for the twice apparent diffusion coefficient (ADC) measurements were between 3% and 7% for the four groups
The current study demonstrated that ADCs of the normal pancreas and test-retest repeatability were dependent on the different anatomical regions of the pancreas
Summary
Magnetic resonance imaging (MRI) is an important tool for the diagnosis and evaluation of various abdominal diseases with quantitative and qualitative methods. For the imaging of the pancreas, MRI is widely used to detect and differentiate pancreatic diseases [1]. As a quantitative MRI technology, diffusion-weighted imaging (DWI) with derived apparent diffusion coefficient (ADC) was introduced to quantify water diffusion in vivo [2]. With a quasi-exponential growth of research applications as well as clinical practice, DWI provides additional information on the pancreas as a supplement to conventional MRI techniques such as T1/T2-weighted imaging [3]. Pancreatic cancer had lower ADC than the normal pancreas [4,5,6]. In order to detect a meaningful difference in ADC, it is desirable that the uncertainty of the ADC measurement should be lower than the difference between the normal and abnormal pancreatic tissues
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