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17-11-2011 | Bone health | Article

Flat-panel CT accurately assesses trabecular architecture of upper spine, femur


Free abstract

MedWire News: Use of a flat-panel fluoroscope device with computed tomography (CT) capability can successfully image trabecular architecture, research shows.

When the trabeculae are thick, such as in the femur, or when the signal-to-noise ratio is high, such as in the cervical spine, architecture and stiffness can be determined accurately, according to researchers.

"However, the reduction in signal-to-noise ratio due to extensive soft tissue layers when scanning the trunk and hip region will reduce the image quality," write Bert van Rietbergen (Eindhoven University of Technology, the Netherlands) and colleagues in the journal Bone.

The current standard for the detection of osteoporosis is the measurement of bone mineral density via dual X-ray absorptiometry or quantitative CT, but these measures are unable to evaluate the biomechanical strength of the trabecular bone or assess fracture risk.

Whole-body CT or magnetic resonance imaging can be used to assess the peripheral skeleton, but the resolution is not sufficient to assess the trabecular architecture of the hip and lower spine.

With the recent development of flat-panel CT devices, which use a very high number of pixels to overcome resolution issues, the researchers scanned 10 cadaver human C3 vertebrae, 12 T12 vertebrae, and 12 proximal femora while mimicking in vivo scan conditions.

The results of the scan were compared with scans of the same bones done with micro-CT imaging.

The flat-panel CT device was able to successfully determine the mean trabecular separation (TbSp) and number (TbN) at all sites. The accuracy of other parameters, however, depended on the site.

For T12, no other structural parameters could be accurately quantified and no finite element results could be obtained from segmented images. When using gray-level images, however, accurate determination of cancellous bone stiffness was possible.

For the C3 vertebrae and proximal femora, mean bone, volume fraction, TbSp, TbN, and anisotropy (at C3) could be determined accurately.

The finite element simulations based segmented images were accurate for the C3 vertebrae, but "severely underestimated bone stiffness for the femur," according to the investigators. This was improved, however, by using the gray value models.

"For the C3 vertebrae and the proximal femora, the trabecular architecture could be determined more accurately than for the T12 vertebrae," state Mulder and colleagues.

Based on these results, flat-panel CT image quality can accurately determine the trabecular structure and stiffness of clinically relevant bone sites, such as the upper spine and proximal femur.

In T12 vertebrae, where trabeculae are thin and there is noise related too soft tissue, image quality is still insufficient for an accurate and complete analysis, they conclude.

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