Bone Marrow MR Imaging

MRI is ideal for bone marrow screening because of its high-resolution images with great soft-tissue contrast. Sequences that are more frequently used in MR imaging of the bone marrow.

• T1 FSE  A routine T1-weighted image without fat suppression is one of the most important sequences for distinguishing between normal and abnormal marrow.  Normal bone marrow is composed of both fatty and hematopoietic elements. Although fatty marrow contains more fat cells than hematopoietic marrow, both types of marrow appear hyperintense relative to skeletal muscle on T1-weighted imaging because they contain a higher proportion of fat cells relative to skeletal muscle. Abnormal marrow is iso - hypointense to skeletal muscle on T1-weighted imaging because the replacement of fatty marrow elements by the pathologic process causes loss of the normal fat signal.  T1-weighted images, red marrow is considerably darker than fatty marrow and has a signal intensity similar to or slightly higher than muscle.
• STIR are extremely sensitive for detecting fluid and so areas with bone marrow oedema appear as hyperintense relative to the background of normal signal suppressed fatty marrow. STIR images have additive T1 and T2 characteristics, which means that tissues with long T1 and long T2 values will appear brighter on STIR than on T2-weighted spin echo images.
• T2  FSE Not primarily used for assessing bone marrow abnormality because both fat and fluid appear bright on T2w sequence. Thus, a pathologic marrow lesion could potentially be overlooked against the background of normal bright fatty marrow.  Use of T2 is confined to evaluation of an associated neural element compression.The vertebral bodies on T2-weighted images are darker than the intervertebral discs, unless the discs are degenerated. T2-weighted fast spin echo images have replaced conventional T2-weighted spin echo images in most institutions, because they offer comparable image quality at shorter imaging time
• Contrast-enhanced T1-weighted images.In the adult, enhancement of normal marrow on MR images acquired after the intravenous administration of a gadolinium chelate is hardly perceptible on visual inspection and is easily differentiated from enhancement associated with marrow lesions.  Precontrast and postcontrast T1-weighted images must be acquired and viewed with the same imaging parameters. Image subtraction and postcontrast T1-weighted images obtained with fat suppression facilitate the detection of abnormal enhancement

Source: DR Balaji Anvekar