title: qMRI relaxometry of mandibular bone marrow: a monomodal distribution in sickle cell disease.
abstract: OBJECTIVE
  To identify and characterize sickle cell disease (SCD)-related changes in the composition of mandibular bone marrow using qMRI relaxometry histograms.
  
  
  METHODS
  Thirteen SCD patients and 17 controls underwent brain MR imaging with the mixed turbo spin-echo (TSE) pulse sequence at 1.5T. The mandible was manually segmented and divided into body, angle, ramus, and condyle. T1 and T2 histograms of each mandible were modeled with Gaussian functions. The relaxation time histogram peaks were calculated, and the number of monomodal versus bimodal curves was compared.
  
  
  RESULTS
  SCD patients exhibited monomodal distributions on both T1 and T2 histograms, consistent with a composition of predominantly red hematopoietic marrow. Eighty-eight percent of mandibles in control subjects exhibited a bimodal distribution in T1 and all showed a bimodal distribution in T2, indicating mixed but predominantly yellow marrow composition. The second peak in control subjects was shorter in T1 and longer in T2, consistent with yellow marrow composition.
  
  
  CONCLUSIONS
  Instead of physiological fatty replacement, SCD patients exhibit red marrow persistence in the mandible, likely due to the increased demand for hematopoiesis. This phenomenon can be manifested by a monomodal curve in both T1 and T2 relaxometric histograms.
authors.affiliation: Department of Radiology, Boston University School of Medicine, Boston, Massachusetts, USA. joseph.h.liao@gmail.com
authors.forename: Joseph H
authors.initials: JH
authors.lastname: Liao
authors.forename: Hernan
authors.initials: H
authors.lastname: Jara
authors.forename: Rohini
authors.initials: R
authors.lastname: Nadgir
authors.forename: Elliott
authors.initials: E
authors.lastname: Elias
authors.forename: Nekou
authors.initials: N
authors.lastname: Nowrouzi
authors.forename: Naoko
authors.initials: N
authors.lastname: Saito
authors.forename: Martin H
authors.initials: MH
authors.lastname: Steinberg
authors.forename: Osamu
authors.initials: O
authors.lastname: Sakai
mesh_terms: D000328:Adult; D000465:Algorithms; D000755:Anemia, Sickle Cell / Q000150:complications* / Q000473:pathology*; D001853:Bone Marrow / Q000473:pathology*; D001855:Bone Marrow Diseases / Q000473:pathology*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008334:Mandible / Q000473:pathology*; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult