THE COMPOSITION OF BONE-MARROW FOR A DUAL-ENERGY QUANTITATIVE COMPUTED-TOMOGRAPHY TECHNIQUE - A CADAVER AND COMPUTER-SIMULATION STUDY

RATIONALE AND OBJECTIVES. The authors have been developing a dual-ener gy quantitative computed tomography (DEQCT) technique that requires ca libration standards that mimic the x-ray attenuation properties of bon e, red marrow, and yellow marrow. To resolve questions regarding the c ompositions of red and yellow marrow that appear in the literature, th e authors performed chemical analyses of bone marrow samples. The newl y derived compositions were used in a simulation study to test the acc uracy of the DEQCT technique. METHODS. Red marrow samples were extrude d from the vertebrae of cadavers of young boys. Yellow marrow samples were removed directly from the femurs of cadavers of elderly women. Th e fat, protein, water, and mineral contents of these samples were dete rmined. The compositions of 12 mixed marrow samples extruded from cada ver vertebrae also were measured. A computer simulation study was perf ormed in which calibration standards with the new compositions were em ployed to estimate the fat and bone contents of spongiosas containing the 12 mixed marrows. RESULTS AND CONCLUSIONS. The red marrow samples contained 3% to 6% fat, 6% to 8% protein, 82% to 86% water, and 0.5% t o 1% mineral. The yellow marrow samples contained 71% to 92% fat, 1% t o 2% protein, 7% to 26% water, and 0.2% to 0.4% mineral. The simulatio n study yielded good results in three cases and mediocre to poor resul ts in nine cases. An alternative approach was tried in which an averag e fat-free marrow was derived from the compositions of the 12 mixed ma rrows, and this substance, fat, and bone were used as the calibration standards. The DEQCT technique with these standards was applied to sim ulated spongiosas containing the 12 original mixed marrows plus nine a dditional mixed marrows. All of the estimates were in good agreement w ith the true compositions. The rms error of the mass fractions of fat was 0.03, and the rms error of the bone concentrations was 3.7 mg/mL.