Apparent diffusion coefficient and fractional anisotropy in the vertebral bone marrow

Abstract

Purpose: To assess the state of cancellous tissue we analyzed the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) in vertebral bone marrow.Materials and Methods: With 1.5 T magnetic resonance imaging (MRI), single-shot diffusion echo planar imaging was used with b factors of 0 and 1000 s/mm 2 , diffusionsensitizing gradient in six directions, sensitivity encoding technique, effective TE of 74 msec, and TR of 1800 msec. ADC and FA were determined in the lumbar vertebral body of 11 normal subjects (age 31 632-635 years), and then compared with the bone mineral density (BMD) obtained with dual-energy x-ray absorptiometry (DXA). Moreover, fat fraction (FF) of the bone marrow was measured with spectral presaturation with inversion recovery (SPIR) in the same subject.Results: A strong negative correlation was found between ADC and BMD for low or moderate FF in vertebral bone marrow. Moreover, a significant positive correlation was noted between ADC and FF in this region. There was a positive correlation between FA and BMD, and no correlation between FA and FF in the vertebral bone marrow.Conclusion: Diffusion analyses with ADC and FA make it possible to obtain more detailed information on the structure of cancellous tissue and bone metabolism.

Diffusion tensor imaging and magnetic resonance spectroscopy assessment of cancellous bone quality in femoral neck of healthy, osteopenic and osteoporotic subjects at 3T: Preliminary experience

“…A good agreement between our FA versus T-score results and Ueda et al results obtained in vertebrae [24] was observed in the healthy group. Unlike the contradictory results obtained in vertebral cancellous bone [17,[22][23][24], a clear relationship between MD and T-score was found in the femoral neck.…”

“…Unlike the contradictory results obtained in vertebral cancellous bone [17,[22][23][24], a clear relationship between MD and T-score was found in the femoral neck. These differences between our MD results and those obtained in vertebrae, are due to a slower water dynamic investigated in this study compared to that in vertebral bone [17,[22][23][24].…”

“…Because the results discussed here highlight a strong correlation between FA and T-score, they underline the greatest potential of a DTI rather than a DWI approach [17,[22][23][24]46], to assess osteoporosis in cancellous bone.…”

“…In particular, since the amount of bone-marrow water compared to bone-marrow fat is higher in vertebrae than in the femoral neck, water dynamic in the femoral neck is more restricted than in vertebrae. As a consequence, to optimize the measurements of water with a slower dynamic, higher b-values compared to those employed to perform DWI in vertebrae [17,[22][23][24]45,46] were used. In this work, by selecting b = 2500 s/mm 2 , we measured an averaged MD approximately equal to 3 * 10 −4 s/mm 2 in the femoral neck.…”

“…Diffusion weighted imaging (DWI) has also been used to investigate vertebral bone although so far it has failed to show a clear relationship between apparent diffusion coefficient (ADC) and BMD [17,[22][23][24]. A more accurate investigation of trabecular bone architecture than that provided by DWI could potentially be found with diffusion tensor imaging (DTI) methods [25] as recently suggested in in vitro investigations [26].…”