9. Marrow Flashcards
Bone marrow consists of three components
(1) Trabecular Bone - the support structure,
(2) Red Marrow - for making blood, and
(3) Yellow Marrow -fat for a purpose unknown at this time.
Marrow Conversion
yellow marrow increases with age - complete at 20s
You are born with red marrow
Red to yellow = extremeties to axial skeleton (feet and hands first
Red marrow can be found in
the humeral heads and femoral heads as a normal variant in adults.
Yellow marrow increases with age
as trabecular bone decreases with osteoporosis, yellow marrow replaces it
Marrow on T1
Yellow is bright. Red is darker than yellow (near iso-intense to muscle).
Red marrow should never be darker than a normal disk or muscle on T1
think about muscle as your internal contro
Red marrow increases if there is a need for ?
more hematopoiesis (reconversion - occurs in exact reverse order of normal conversion)
Marrow turns yellow with?
Stress / degenerative change in the spine
Three most classic marrow questions
- What is the normal pattern of conversion ?
- What is the normal pattern o f REconversion?
- What areas are spared/ normal variants?
What is the normal pattern of conversion ?
The epiphyses convert to fatty marrow almost immediately after ossification. Distal then proceeds medial / proximal (diaphysis first, then metaphysis).
What is the normal pattern of Reconversion?
This occurs in the reverse
order of normal marrow conversion, beginning in the axial
skeleton and heading peripheral. The last to go are the more
distal long bones. Typically, the epiphyses are spared unless
the hematopoietic demand is very high.
What areas are spared/ normal variants?
Patchy areas of red marrow may be seen in the proximal femoral metaphysis of teenagers. Distal femoral sparing is seen in teenagers and menstruating women.
Leukemia
Proliferation of leukemic cells results in replacement of red marrow
Marrow will look darker than muscle (and normal disks) on Tl. On STIR, marrow may be brighter than muscle because of the increased water content. T2 is variable, often looking like diffuse red marrow.
They can show leukemia in two main ways
(1) Lucent metaphyseal bands in a kid
(2)Tl-weighted MRl showing marrow darker than adjacent disks and muscle. Remember that Red Marrow is still 40% fat and should be brighter than muscle on Tl.
Most infiltrative conditions affect the marrow diffusely. The exceptions are multiple myeloma, which has a
predilectionforfocal “speckled” deposits, and Waldenstrom’s macroglohulinemia, which causes infarcts.
Leukemia
Lucent metaphyseal bands in a kid
Leukemia
Chloroma (Granulocytic Sarcoma)
Just say “destructive mass in a bone o f a leukemia patient. ” It’s some kind of colloid tumor.
