Synopsis

Keywords: Bone, Data Acquisition

Intravoxel incoherent motion (IVIM) and fat-water magnetic resonance imaging (FWMRI) are rarely used for vertebral and intervertebral disc. To search for predictive value of them in assessing the lumbar spine microenvironment changes, we performed a study with postmenopausal women combined the parameters with bone mineral density (BMD) and major fracture risk assessment (FRAX) score. We report that fat fraction (FF) has significant correlation with FRAX, FF was moderately negatively correlated with BMD; ADC_slow of intervertebral discs showed moderately negatively correlation with FRAX score and FF. IVIM and FWMRI have potential to become new biomarkers in predicting lumbar spine microenvironment changes.

Purpose

To investigate the predictive value of intravoxel incoherent motion (IVIM) and fat-water magnetic resonance imaging (FWMRI) parameters in evaluating the vertebral and intervertebral disc microenvironment changes in postmenopausal women.

Methods

In this study, all enrolled women underwent MRI and dual-energy X-ray absorptiometry (DXA) imaging. Major fracture risk was also evaluated for all participants using Fracture Risk Assessment Tool (FRAX) by a senior radiologist with International Society for Clinical Densitometry (ISCD) qualification. Participants were divided into premenopausal (n=10) and postmenopausal (n=10) group. The exclusion criteria were as follows: (1) spine surgery; (2) bone diseases; (3) malignant tumors; (4) long-term use of drugs that affect bone metabolism. MRI examinations were performed through a commercially available 3.0 T MRI system. Routine MR lumbar spine protocol was performed using a 32-channel spine matrix coil for pretreatment planning. IVIM images were acquired on the basis of ss-EPI method with 16 b values (0, 10, 20, 40, 80, 110, 140, 170, 200, 300, 400, 500, 600, 800, 1000, 1200s/mm²). As traditional monoexponentially ADC values are unable to distinguish the true diffusion and perfusion effects in tissues, a biexponential model was used to calculate the true apparent diffusion coefficient (ADC_slow), pseudo–apparent diffusion coefficient (ADC_fast) and perfusion fraction (f) maps. FWMRI images were obtained using a fat analysis and calculation technique（FACT) sequence. To overcome the limitations of traditional region-growing methods and multiresolution methods, variable projection was implemented for robust fat-water separation in this study (Hao et al. 2019; Cheng et al. 2017). FWMRI images were acquired with the following parameters: FOV = 400 x 300 mm, matrix = 256 x 192 x 22, pixel size = 1.56 x 1.56 x 8 mm3, contrast = 6, flip angle = 3°, Bandwidth = 900 Hz/pixel, TE = 1.73/3.26/4.79/6.32/7.85/9.38 ms, TR = 10.94 ms. IVIM images were measured with a region of interest-based approach on corresponding maps of the vertebral and intervertebral discs for ADC_slow, ADC_fast and f respectively. Bone marrow fat fraction (FF) and R2^* values of vertebral were measured on FWMRI images as shown in Figure 1. MRI parameters were tested for significant differences between two groups using T test for normal distributions or Mann-Whitney test if the data was not normally distributed as shown in Table 1. Spearman’s rank correlation was performed to test correlation between MRI parameters and BMD, FRAX score respectively as shown in Table 2.

Results

There were significant differences in FF of vertebral (P < 0.001) and ADC_slow of intervertebral discs (P = 0.003) between premenopausal and postmenopausal group. Moreover, there was significant correlation between bone marrow FF and FRAX (r = 0.824, P < 0.0001), and FF was moderately negatively correlated with BMD (r = -0.409, P = 0.073). ADC_slow of intervertebral discs showed moderately negatively correlation with FRAX score and FF.

Conclusions

IVIM and fat-water MRI parameters have potential to become new biomarkers in effectively predicting vertebral and intervertebral disc microenvironment changes in postmenopausal women.

Acknowledgements

None