MR patterns of bone marrow of calvarium and vertebral body in normal subjects; Pattern analysis according to age distribution

The purpose of this study is to illustrate MR patterns of bone marrow of calvarium and vertebral body in normal subjects according the age distribution and to understand the course of the fatty replacement from red marrow. We retrospectively evaluated MR examinations of the calvaria(n=71), cervical spine(n=71), thoracic spine(n=65), lmbar spine(n=68) in subjects without bone marrow abnormality whose age ranged 3 weeks to 74 years. Three distinctive patterns were categorized on T1-weighted images of the skull. In pattern 1, uniformly low signal intensity with or without very small areas of high intensity in frontal and occipital bones is noted. In pattern 2, frontal and occipital bones have uniformly high signal intensity, and patchy area of high intensity appears in parietal bone. In pattern 3, the entire skull has uniformly high signal intensity. In the spine, four patterns were categorized on T1-weighted MR images. In pattern 1, the vertebral body has uniformly low signal intensity expect for linear areas of high intensity superior and inferior to basivertebral vein. In pattern 2, bandlike and triangular areas of high signal intensity are found in the periphery. Pattern 3 and 4 have diffusely distributed areas of high signal intensity; pattern 3 consist of numerous indistinct dots measuring a few millimeter or less, and pattern 4 consist of fairly well marginated areas ranging in size from 5 to 1.5 cm. In the calvaria, 73% of pattern 1 were younger than 20 years, pattern 2 were evenly distributed, and 86% of pattern 3 were older than 40 years. In the spine, 87% of pattern 1 were younger than 40 years, 72% of pattern 3 were in 40 to 50 years, and 87% of pattern 4 were older than 50 years. Pattern 2 were evenly distributed in the cervical and thoracic spine, but in the thoracic spine 62% were younger than 30 years. It is concluded that younger age group shows mainly pattern 1, whereas elderly group has pattern 3 or 4 in the calvarial and vertebral body marrow. This suggests that conversion to fatty marrow begin locally and progress diffusely with age