1798 symptoms [1]. Particularly in the early clinical stages, no abnormal intensity is observed in the spinal cord on con- ventional MR images, despite the clinical manifestations. In fact, absolute surgical indications for cervical spondylosis with myelopathy remain to be established [2]. Therefore, in the clinical situation, an objective method of using MR imaging to estimate damage in patients with cervical spon- dylosis is desirable. In addition to conventional morphologic MR imaging, diffusion tensor imaging (DTI) has been proposed for evalu- ating microstructural changes in the brain. Signal changes in DTI are based on the diffusion of water molecules in tissues, and characteristic quantitative values, such as the fractional anisotropy (FA) and apparent diffusion coefficient (ADC), can be calculated [3]. In short, the FA value is used most frequent- ly to measure diffusion anisotropy, and the ADC is a scalar value that reflects molecular diffusivity when motion is re- stricted, for example by fluid viscosity. DTI can be used with higher sensitivity and specificity than conventional MR im- aging to estimate white matter changes in neurodegenerative disease [4] or demyelinated lesions [5]. In the spinal cord, DTI with FA or ADC measurements shows promise for detecting and quantifying the pathology of spinal cord abnormalities. Reduced FA and increased ADC have been observed in the spinal cord at compressed sites and are presumably explained by microstructural changes [6, 7]. Recently, a more advanced form of diffusion analysis, q-space imaging (QSI) analysis, has emerged. This technique does not require the assumption of a Gaussian shape and model of water molecules. It has shown promise for evaluating brain and spinal disorders in vivo [8–13] because it can provide additional and different diffusion metrics, namely the root mean square displacement (RMSD) and diffusional kurtosis (DK) [14–20], which give in vivo microstructural information that complements the ADC and FA values. For example, increased ADC can indicate either decreased viscosity of the tissue or spatial dilatation of the water movement space [21]. It is difficult to distinguish between these phenomena by using ADC values only. How- ever, the RMSD values reflect the real extent of water mole- cule movement. We therefore hypothesized that QSI analysis would be able to provide more information on structural and pathological changes in the spinal cord in vivo. Our aim was to investigate the use of RMSD and mean DK metrics derived from QSI data to estimate spinal cord compression in patients with early cervical spondylosis. Materials and methods Subjects Between 28 October 2010 and 25 February 2011, a total of 50 consecutive patients at our institution (22 male, 28 Eur Radiol (2012) 22:1797–1802 female; mean age 58 years; age range 20–86 years) with clinical signs and symptoms suggestive of early cervical myelopathy participated in this study. Informed consent was obtained from each patient. We obtained ethics approv- al from the institutional review board before the study. Exclusion criteria were as follows: (a) the presence of other intraspinal disease; (b) the presence of abnormal intensity in the spinal cord on conventional MR imaging (T1- or T2- weighted imaging); (c) a history of surgery to the neck for any disease; and (d) unsatisfactory image quality for calcu- lating diffusion metrics. Image acquisition All images were acquired by using 3-T MR (Achieva; Philips Medical Systems, Best, Netherlands). After turbo spin-echo T1- and T2-weighted sagittal and axial imaging, diffusion tensor and q-space image data were acquired. Imaging parameters for sagittal images were as follows: repetition time (ms)/echo time (ms) 612.5/7.7 for T1- weighted imaging (T1WI) and 3,000/90 for T2-weighted imaging (T2WI); echo train length 4 for T1WI and 21 for T2WI; number of signals acquired 2; section thickness/gap 4/0.4 mm; 12 sections; field of view 220 ×220 mm; matrix 512 × 512. Imaging parameters for axial images were as follows: repetition time (ms)/echo time (ms) 606.9/9.9 for T1WI and 4300/90 for T2WI; echo train length 5 for T1WI and 17 for T2WI; number of signals acquired 2; section thickness/gap 5/0.5 mm; 20 sections; field of view 160× 160 mm; matrix 512 × 512. Parameters used for the diffusion tensor imaging and QSI were as follows: repetition time (ms)/echo time (ms) 6,996/73; number of signals acquired 1; section thickness/gap 3/0 mm; 30 sections; field of view 80 ×80 mm; matrix 64 ×64 (128 × 128 reconstructed); imag- ing time approximately 7 min; and six b values (0, 400, 800, 1,200, 1,600 and 2,000 s/mm2) with diffusion encoding in 6 directions for every b value. Corresponding q values for each b value were 175.9, 248.8, 304.7, 351.9 and 393.4 cm–1, respectively. Gradient length (δ) and time between the two leading edges of the diffusion gradient (Δ) were 10.7 and 36.3 ms, respectively. Diffusion tensor, q-space and kurtosis imaging analysis of the spinal cord Diffusion tensor, q-space and kurtosis analyses were per- formed by using the free software dTV II FZR and Volume- One 1.72 (Image Computing and Analysis Laboratory, De- partment of Radiology, The University of Tokyo Hospital, Tokyo, Japan) [7] on an independent Windows PC. First, FA and ADC maps, based on the conventional mono-exponential model, were calculated (Fig. 1). Because the q-space image data included multiple b value data, FA