Differentiation of Osteoporotic and Neoplastic Vertebral Fractures by Chemical Shift {In-Phase and Out-of Phase} Magnetic Resonance Imaging and Diffusion Weighted Sequence

Abstract

In elderly population neoplastic wedging of the spine may be an early manifestation of underlying malignancy and differentiating benign wedging due to underlying osteoporosis from malignant wedging has been an important and sought after goal of imaging. Other challenging clinical case scenario is the occurrence of benign osteoporotic vertebral collapse in a patient already known to have underlying malignancy .Although magnetic resonance imaging (MRI) is a sensitive method for assessing bone marrow, it lacks specificity. The problem is that abnormal signal intensity in benign compression fractures on conventional MR imaging can be similar to that seen in vertebrae with underlying malignancy. Although certain morphologic signs may be helpful for assessing the cause of the fracture yet these lack specificity. The presence of both fat and water in normal marrow results in suppression of signal intensity on the opposed-phase images. In benign osteoporotic collapse, no marrow replacement has occurred, thus the existence of normal marrow fat should result in suppression of signal intensity on the opposed-phase images; while in malignant collapse the normal fat-containing marrow is replaced with tumoral process which should result in lack of suppression on the opposed phase images. Diffusion-weighted sequences are sensitive to molecular motion because random motion of water molecules in gradient fields produces phase dispersion and, therefore, signal attenuation. The current review will focus on the advent of both modalities and the value to order them in proper clinical setting.