Friday, February 14, 2014

Age related changes of Spinal Bone Marrow in T1 MRI



·   Human beings are born with red / hematopoietic marrow in their entire skeleton, which gets gradually replaced by fat as age progresses, and reaches the mature state by the age of 25years.
·          
    In adult pattern the red marrow is seen in the axial skeleton and proximal appendicular skeleton.
·          
    The red / hematopoietic marrow SI in neonates may be slightly lower than that of the skeletal muscle; thereafter marrow the signal intensity increases. So if the Marrow SI is found to be lower than of the normal skeletal muscle it almost always indicate a marrow pathology.
·           
    Under 40yrs of age, the axial skeleton contains fat only at the basivertebral vein region.
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    The replacement of the red to yellow marrow can occur in 3 patterns :
1.      Bandlike pattern along the endplate.
2.      Small foci of replacement.
3.      Larger globular areas of fatty replacement.
·              
    Near complete fatty replacement may be seen in some elderly patients and in cases of malnutrition or osteoporosis.
·           
    Conditions increasing the need for hematopoiesis like Chronic hypoxia, Anemia etc can cause reversal of fatty replcament, back to red marrow. These are usually seen as patches of T1 hypointensity.
·          

In cases of Sickle cell disease where the yellow marrow,can convert back to red marrow OR may never convert Yellow.
     
    The red marrow contains 40% of fat and yellow marrow contains 80% of fat !!!


      Ref  : AJR article MRI of spinal bone marrow -Part I. 2011.

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