title: Bone marrow segmentation based on a combined consideration of transverse relaxation processes and Dixon oscillations.
abstract: The aim of this study was to demonstrate that gradient-echo sampling of single spin echoes can be used to isolate the signal from trabecular bone marrow, with high-quality segmentation and surface reconstructions resulting from the application of simple post-processing strategies. Theoretical expressions of the time-domain single-spin-echo signal were used to simulate signals from bone marrow, non-bone fatty deposits and muscle. These simulations were compared with and used to interpret signals obtained by the application of the gradient-echo sampling of a spin-echo sequence to image the knee and surrounding tissues at 1.5 T. Trabecular bone marrow has a much higher reversible transverse relaxation rate than surrounding non-bone fatty deposits and other musculoskeletal tissues. This observation, combined with a choice of gradient-echo spacing that accentuates Dixon-type oscillations from chemical-shift interference effects, enabled the isolation of bone marrow signal from surrounding tissues through the use of simple image subtraction and thresholding. Three-dimensional renderings of the marrow surface were then readily generated with this approach - renderings that may prove useful for bone morphology assessment, e.g. for the measurement of femoral anteversion. In conclusion, understanding the behavior of signals from bone marrow and surrounding tissue as a function of time through a spin echo facilitates the segmentation and reconstruction of bone marrow surfaces using straightforward post-processing strategies that are typically available on modern radiology workstations.
authors: Department of Radiology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.
authors: Mukund
authors: M
authors: Balasubramanian
authors: Department of Radiology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.
authors: Delma Y
authors: DY
authors: Jarrett
authors: Department of Radiology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.
authors: Robert V
authors: RV
authors: Mulkern
mesh_terms: D001853:Bone Marrow / Q000033:anatomy & histology*; D003198:Computer Simulation; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D013113:Spin Labels; D013997:Time Factors
chemical_list: D013113:Spin Labels
keywords: irreversible; reversible; three-dimensional models; trabeculae; transverse relaxation