MRI heterogeneity of articular cartilage in strong magnetic fields: Dependence on proteoglycan content

Shadi F. Othman, James M. Williams, Dale R. Sumner, Richard L. Magin

Research output: Contribution to journalArticle

Abstract

Articular cartilage is a thin heterogeneous tissue (typical thickness of less than 2 mm) composed of collagen, proteoglycan, and water that coats skeletal joint surfaces. Its physical and chemical integrity are essential for maintaining normal joint articulation. MR imaging techniques are being developed to visualize articular cartilage for the purpose of assessing changes in its structure that occur with age and the onset of joint disease. Emerging high-field MR systems (greater than 4 T) have a higher signal-to-noise ratio, which can be used to improve the spatial resolution for imaging articular cartilage beyond that available in most clinical systems. In this study, we examined the effect of changing the proteoglycan content of articular cartilage on high-resolution (40 X 40 X 100 μm) T1- and T2-weighted images acquired at 11.74 T (500 MHz for protons). Susceptibility artifacts were observed near the cartilage-bone interface that were verified by separating the cartilage from the bone. MR image heterogeneity of articular cartilage was observed as a function of depth and in the transverse directions of the sample. Enzymatic depletion of cartilage proteoglycan demonstrated that the MR image heterogeneity is due in part to variation of the proteoglycan content in different regions of the cartilage. The apparent diffusion coefficient (ADC) was measured as a function of depth in the cartilage. The ADC varied from the subchondral bone to the articular surface for both normal and digested cartilage. In addition, the ADC increased by 20% after 6 hours of enzymatic digestion of proteoglycan. These results suggest a role for high-field MRI of articular cartilage in the management and staging of osteoarthritis and other joint diseases.

Original languageEnglish (US)
Pages (from-to)33-43
Number of pages11
JournalConcepts in Magnetic Resonance Part B: Magnetic Resonance Engineering
Volume23
Issue number1
DOIs
StatePublished - Oct 2004

Keywords

  • Apparent diffusion coefficient
  • Articular cartilage
  • Collagen
  • Heterogeneity
  • MR imaging
  • MR microscopy
  • Magic angle
  • Proteoglycan
  • Susceptibility

ASJC Scopus subject areas

  • Radiological and Ultrasound Technology
  • Radiology Nuclear Medicine and imaging
  • Spectroscopy
  • Physical and Theoretical Chemistry

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