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dGEMRIC as a function of BMI
C Tiderius1, M Hori, A Williams
1Department of Radiology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02115, USA.
Osteoarthritis and Cartilage
|June 20, 2006
Summary
Body Mass Index (BMI) affects contrast agent concentration in delayed gadolinium-enhanced MRI of cartilage (dGEMRIC). Adjusting for this bias reveals no correlation in healthy knees but a negative correlation in osteoarthritis knees.
Area of Science:
- Biomedical Imaging
- Radiology
- Orthopedics
Background:
- Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) assesses glycosaminoglycan (GAG) distribution.
- Standard dGEMRIC protocols assume uniform plasma contrast agent levels post-injection, irrespective of body composition.
- Adipose tissue has lower extracellular water, potentially altering contrast distribution and affecting dGEMRIC accuracy.
Purpose of the Study:
- To investigate the relationship between Body Mass Index (BMI) and plasma levels of the contrast agent Gd-DTPA(2-).
- To evaluate the impact of BMI-related contrast dosing bias on dGEMRIC measurements.
- To determine the correlation between corrected dGEMRIC values and BMI in asymptomatic and osteoarthritis (OA) knees.
Main Methods:
- Plasma Gd-DTPA(2-) concentrations were measured at serial time points after intravenous injection in individuals with varying BMIs (21.5–46.5).
- dGEMRIC imaging was performed on asymptomatic volunteers and patients with osteoarthritis.
- Statistical analyses were conducted to assess correlations between BMI, plasma contrast levels, and dGEMRIC values, with adjustments for dosing bias.
Main Results:
- Obese individuals exhibited higher plasma Gd-DTPA(2-) concentrations compared to leaner individuals, indicating a potential dosing bias.
- A subject with BMI 45 had 1.4 times higher contrast concentration than a subject with BMI 20, leading to up to 20% bias in dGEMRIC.
- After correcting for dosing bias, dGEMRIC showed no correlation with BMI in asymptomatic knees.
- In OA knees, a negative correlation was observed between dGEMRIC and BMI in non-narrowed femoral compartments (R=0.57, P=0.004).
Conclusions:
- Body Mass Index (BMI) is a significant factor contributing to dosing bias in dGEMRIC.
- A correction factor for BMI should be considered in dGEMRIC studies with a wide range of patient BMIs.
- dGEMRIC is not correlated with BMI in healthy knees, but shows a negative correlation in osteoarthritis knees, suggesting altered cartilage composition in obesity within OA.
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