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DOI: 10.1148/radiol.2492071681
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(Radiology 2008;249:624-630.)
© RSNA, 2008

Neuroradiology

Variability in Absolute Apparent Diffusion Coefficient Values across Different Platforms May Be Substantial: A Multivendor, Multi-institutional Comparison Study1

Makoto Sasaki, MD, Kei Yamada, MD, Yoshiyuki Watanabe, MD, Mieko Matsui, MD, Masahiro Ida, MD, Shunrou Fujiwara, PhD, and Eri Shibata, MD For the Acute Stroke Imaging Standardization Group-Japan (ASIST-Japan) Investigators

1 From the Advanced Medical Research Center, Iwate Medical University, 19-1 Uchimaru, Morioka 020-8505, Japan (M.S., S.F., E.S.); Department of Radiology, Kyoto Prefectural University of Medicine, Kyoto, Japan (K.Y.); Department of Radiology, National Cardiovascular Center, Osaka, Japan (Y.W.); Department of Radiology, Nishi-Kobe Medical Center, Kobe, Japan (M.M.); and Department of Radiology, Ebara Hospital, Tokyo, Japan (M.I.). Received September 23, 2007; revision requested January 4, 2008; revision received May 9; accepted May 27; final version accepted June 9. Supported in part by a Research Grant for Cardiovascular Diseases (17C-3) from the Ministry of Heath, Labor and Welfare of Japan and by a Grant-in-Aid for Advanced Medical Science Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan. Address correspondence to M.S. (e-mail: masasaki{at}iwate-med.ac.jp).

Purpose: To determine whether and to what degree absolute apparent diffusion coefficient (ADC) values vary between different imagers, vendors, field strengths, and intraimager conditions.

Materials and Methods: Informed consent and institutional review board approval were obtained. Diffusion-weighted (DW) images with nearly identical parameters were obtained at 1.5 and 3.0 T from 12 healthy volunteers at seven institutions by using 10 magnetic resonance (MR) imagers provided by four different vendors. ADC maps were generated from isotropic DW maps, and images with a b value of 0 sec/mm2 were generated by using in-house software. The mean pixel values for the brain tissues were calculated for evaluating the differences among coil systems, imagers, vendors, and magnetic field strengths.

Results: The absolute ADC values of gray and white matter from the same vendor varied substantially: 4%–9% at 1.5 and 3.0 T. With the exception of one vendor, the intervendor variability at 1.5 T was as high as 7%. Moreover, there was substantial intraimager variability, up to 8%, depending on the coil systems in certain imagers.

Conclusion: There is significant variability in ADC values depending on the coil systems, imagers, vendors, and field strengths used for MR imaging. The relative ADC values may be more suitable than absolute ADC values for evaluating diffusion abnormalities in patients enrolled in multicenter acute ischemic stroke trials.

© RSNA, 2008