الفهرس 
Gross Anatomy of the SpineOnly 14 pages are availabe for public view
 |  | from | 162 |  |  |
| | | from | 162 | | |
Abstract
Vertebral compression fractures may be detected on radiographs, CT scans or radionuclide bone scans but in today’s clinical enviroment, the specific discrimination between benign and malignant vertebral compression fractures relies heavily on MR imaging features including the marrow-space signal intensity on various sequences, the location and extent of the signal abnormalities in the compressed vertebral body, involvement of the pedicles and neural arch structures, the presence of epidural or paravertebral soft tissue masses, multiplicity and contrast enhancement patterns.
Yet still confident diagnosis is not always possible because of the considerable overlap in the signal changes between acute to sub acute fractures from malignant fractures which isn’t acceptable as prognosis and management differ completely in these two entities.
Over the last decade, DWI of the vertebral body has received considerable attention as it provides unique tissue characterization that is complementary to that provided by conventional MR imaging and is sensitive to micro-structural changes. The reduced mobility of water in pathologic fractures is the result of tumor cell accumulation and subsequent reduction in the interstitial spaces that results in high signal intensity compared to normal bone marrow. On the other hand, the increased mobility of water attributed to an increase in the interstitial space in relation to edema or hemorrhage in benign fractures results in low signal intensity.
Studies furtherly proved that factors as T2 shine-through and perfusion effects could mask diffusion related signal patterns. Accordingly, semi-quantitative and quantitative measurements were introduced.
The NLNM ratio was employed for semi-quantitative diffusion measurement and it showed a statistically significant difference between the malignant and benign groups.
ADC represents the quantitative assessment of diffusion weighting. It expresses the diffusion of water protons in a ROI and is calculated by a regression analysis of the signal. It shows different figures in normal marrow, benign edema, malignancy and tumor necrosis and so it is considered a dependable parameter in distinguishing benign from malignant causes of vertebral compression fractures. It also plays an important role in monitoring the response of tissues to treatment by revealing even the slightest treatment-related changes in tissue characteristics.
To sum up, DWI has proven to be a powerful tool for evaluating bone marrow infiltration. Quantitative diffusion measurements seem to be highly specific and very sensitive to differentiate between malignant and benign skeletal processes by probing the microstructure of a biologic tissue. Changes in the microstructure result in alterations of the diffusivity of the tissue, which in turn may provide non-invasively acquired information for therapy monitoring.