title: Advances of 3T MR imaging in visualizing trabecular bone structure of the calcaneus are partially SNR-independent: analysis using simulated noise in relation to micro-CT, 1.5T MRI, and biomechanical strength.
abstract: OBJECTIVE
  To investigate differences in magnetic resonance imaging (MRI) of trabecular bone at 1.5T and 3.0T and to specifically study noise effects on the visualization and quantification of trabecular architecture using conventional histomorphometric and nonlinear measures of bone structure.
  
  
  METHODS
  Sagittal MR images of 43 calcaneus specimens (donor age: 81 +/- 10 years) were acquired at 1.5T and 3.0T using gradient echo sequences. Noise was added to obtain six sets of images with decreasing signal-to-noise ratios (SNRs). Micro-CT images were obtained from biopsies taken from 37 calcaneus samples and bone strength was determined. Morphometric and nonlinear structure parameters were calculated in all datasets.
  
  
  RESULTS
  Originally, SNR was 1.5 times higher at 3.0T. In the simulated image sets, SNR was similar at both fields. Trabecular dimensions measured by microCT were adequately estimated by MRI, with residual errors (e(r)), ranging from 16% to 2.7% at 3.0T. Comparing e(r) at similar SNR, 3.0T consistently displayed lower errors than 1.5T (eg, bone fraction at SNR approximately 4: e(r)[3.0T] = 15%; e(r)[1.5T] = 21%, P < 0.05).
  
  
  CONCLUSIONS
  The advances of 3.0T compared to 1.5T in visualizing trabecular bone structure are partially SNR-independent. The better performance at 3.0T may be explained by pronounced susceptibility, enhancing the visualization of thin trabecular structures.
authors.affiliation: Department of Radiology, Technische Universität München, Munich, Germany. jsb@roe.med.tum.de
authors.forename: Jan S
authors.initials: JS
authors.lastname: Bauer
authors.forename: Roberto
authors.initials: R
authors.lastname: Monetti
authors.forename: Roland
authors.initials: R
authors.lastname: Krug
authors.forename: Maiko
authors.initials: M
authors.lastname: Matsuura
authors.forename: Dirk
authors.initials: D
authors.lastname: Mueller
authors.forename: Felix
authors.initials: F
authors.lastname: Eckstein
authors.forename: Ernst J
authors.initials: EJ
authors.lastname: Rummeny
authors.forename: Eva-Maria
authors.initials: EM
authors.lastname: Lochmueller
authors.forename: Christoph W
authors.initials: CW
authors.lastname: Raeth
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Link
mesh_terms: D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002111:Calcaneus / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000503:physiopathology; D019245:Compressive Strength; D055119:Elastic Modulus; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010024:Osteoporosis / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical; D014057:Tomography, X-Ray Computed / Q000379:methods*