To compare the coefficient of variation (CV) and long-term reproducibility of apparent diffusion coefficient (ADC) in a simple fluid-filled phantom and abdominal organs simultaneously.
Retrospective institutional review board–approved and Health Insurance Portability and Accountability Act–compliant study sequentially selected 100 patients who underwent clinically indicated abdominal magnetic resonance imaging. A subset of 58 patients had repeat scans within 2 to 5 months after the initial magnetic resonance imaging. Two diffusion-weighted imaging techniques (b-values 0–750 mm2/s) were performed to compare the ADC values. Mean ADC values were calculated for 10 locations and the reference phantom. The CV and Bland-Altman plots were calculated for the phantom and soft tissues at each session and location.
There were no significant differences in the mean ADC values between repeated acquisitions. However, ADC values were statistically higher using dual-b-value than multi-b-value diffusion-weighted imaging. The CV for the phantom was 8.6 versus 10.8 for dual-b-value and multi-b-value, respectively. The CVs for the soft tissues had a wider range compared with that of the phantom (liver, 12.6 vs 9.0; spleen, 11.7 vs 11.2; gallbladder, 11.0 vs 13.6; head of pancreas, 14.6 vs 14.7; body of pancreas, 13.4 vs 13.0; tail of pancreas, 14.8 vs 16.3; right kidney, 9.1 vs 9.6; left kidney, 9.3 vs 9.3; right paraspinal muscle, 7.9 vs 7.5; left paraspinal muscle, 7.3 vs 7.3, respectively).
A change in ADC less than 11% falls into the range of measurement variability. Paraspinal muscle could potentially be used as an internal reference parameter.
From the *The Russell H. Morgan Department of Radiology and Radiological Sciences, Johns Hopkins University; and †Center for Applied Medical Imaging, Siemens Corporate Research, Baltimore, MD.
Received for publication July 6, 2012; accepted August 30, 2012.
Reprints: Ihab R. Kamel, MD, PhD, Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, 600 N. Wolfe St, Nelson Basement MRI 143, Baltimore, MD 21287 (e-mail: firstname.lastname@example.org).
The authors report no conflicts of interest.