Objective: A line scan spectroscopic imaging method providing variable T2- weighted spectra from many small voxels along selected tissue columns was applied to study the chemical composition of hematopoietic and fatty marrow in the knees of adults and children. Materials and Methods: Line scan Carr-Purcell-Meiboom-Gill (CPMG) spectroscopic imaging sequences were implemented on a 1.5 T clinical scanner. Variable T2-weighted proton spectra from 128 locations along 20 cm long, 5 mm2 columns oriented superiorly to inferiorly through knees were collected from eight healthy adults and eight children. Results: In adult yellow marrow, olefinic protons, water, a composite lipid proton peak, and methyl/methylene protons contributed 6.4 ± 0.4, 4.2 ± 1.5, 7.2 ± 0.5, and 82.2 ± 1.9% (mean ± SD) to the spectra, respectively. Marrow spectra were largely independent of position along the column. Marrow spectra of normal children showed distinct positional dependences. Epiphyseal marrow spectra of children (8-16 years old) resembled adult spectra but with more water (mean 15 vs. 4%). Metaphyseal marrow had higher, variable water content, reflecting the extent of marrow conversion and generally obscuring the olefinic proton peak. Conclusions: Spectroscopic imaging of columns is a time-efficient method for sampling extensive regions of bone marrow with high spatial resolution. It should prove useful for proton spectroscopic studies of hematologic pathologies and conditions requiring the monitoring of lipid composition.
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