Diffusion-weighted MR imaging in differentiation between osteoporotic and neoplastic vertebral fractures.

PURPOSE: To assess the usefulness of magnetic resonance imaging (MRI) with spin-echo echo-planar diffusion-weighted imaging (SE-EPI-DWI) in differentiation between vertebral osteoporotic fractures and pathological neoplastic fractures. MATERIALS AND METHODS: Thirty-three patients with both osteoporotic or neoplastic vertebral fractures diagnosed with X-ray or TC were studied with MRI exam, (1.5 T unit) with DWI sequences. DWI sequences were qualitatively analyzed. Apparent diffusion coefficient (ADC) values were also determined and compared to the definitive histologic diagnosis. RESULTS: DWI of neoplastic lesions showed hyperintensity signal in 22 out of 23 cases. Mean ADC value of neoplastic fractures was 1.241 ± 0.4 × 10(-3) mm(2)/s; mean ADC value of osteoporotic fractures was 0.646 ± 0.368 × 10(-3) mm(2)/s. Neoplastic fractures showed ADC values significantly higher than osteoporotic ones (p < 0.001). DWI imaging and histology showed a significant correlation. CONCLUSION: DWI provides reliable information to support MRI diagnosis of neoplastic versus osteoporotic fractures. ADC value appears as a useful adjunctive parameter.

Metal-related artifacts in instrumented spine. Techniques for reducing artifacts in CT and MRI: state of the art.

The projectional nature of radiogram limits its amount of information about the instrumented spine. MRI and CT imaging can be more helpful, using cross-sectional view. However, the presence of metal-related artifacts at both conventional CT and MRI imaging can obscure relevant anatomy and disease. We reviewed the literature about overcoming artifacts from metallic orthopaedic implants at high-field strength MRI imaging and multi-detector CT. The evolution of multichannel CT has made available new techniques that can help minimizing the severe beam-hardening artifacts. The presence of artifacts at CT from metal hardware is related to image reconstruction algorithm (filter), tube current (in mA), X-ray kilovolt peak, pitch, hardware composition, geometry (shape), and location. MRI imaging has been used safely in patients with orthopaedic metallic implants because most of these implants do not have ferromagnetic properties and have been fixed into position. However, on MRI imaging metallic implants may produce geometric distortion, the so-called susceptibility artifact. In conclusion, although 140 kV and high milliamperage second exposures are recommended for imaging patients with hardware, caution should always be exercised, particularly in children, young adults, and patients undergoing multiple examinations. MRI artifacts can be minimized by positioning optimally and correctly the examined anatomy part with metallic implants in the magnet and by choosing fast spin-echo sequences, and in some cases also STIR sequences, with an anterior to posterior frequency-encoding direction and the smallest voxel size.