Intravoxel incoherent motion (IVIM) detects femoral head ischemia in a piglet model of Legg-Calvé-Perthes disease.

Abstract

There is a clinical need for alternatives to gadolinium contrast-enhanced magnetic resonance imaging (MRI) to facilitate early detection and assessment of femoral head ischemia in pediatric patients with Legg-Calvé-Perthes disease (LCPD), a juvenile form of idiopathic osteonecrosis of the femoral head. The purpose of this study was to determine if intravoxel incoherent motion (IVIM), a noncontrast-enhanced MRI method to simultaneously measure tissue perfusion and diffusion, can detect femoral head ischemia using a piglet model of LCPD. Twelve 6-week-old piglets underwent unilateral hip surgery to induce complete femoral head ischemia. The unoperated, contralateral femoral head served as a perfused control. The bilateral hips of the piglets were imaged in vivo at 3T MRI using IVIM and contrast-enhanced MRI 1 week after surgery. Median apparent diffusion coefficient (ADC) and IVIM parameters (diffusion coefficient: D_s; perfusion coefficient: D_f; perfusion fraction: f; and perfusion flux: f*D_f) were compared between regions of interest comprising the epiphyseal bone marrow of the ischemic and control femoral heads. Contrast-enhanced MRI confirmed complete femoral head ischemia in 11/12 piglets. IVIM perfusion fraction (f) and flux (f*Df) were significantly decreased in the ischemic versus control femoral heads: on average, f decreased 47 ± 27% (Δf = -0.055 ± 0.034; p = 0.0003) and f*Df decreased 50 ± 27% (Δf*Df = -0.59 ± 0.49 × 10^-3 mm²/s; p = 0.0026). In contrast, IVIM diffusion coefficient (D_s) and ADC were significantly increased in the ischemic versus control femoral heads: on average, D_s increased 78 ± 21% (ΔD_s = 0.60 ± 0.14 × 10^-3 mm²/s; p < 0.0001) and ADC increased 60 ± 36% (ΔADC = 0.50 ± 0.23 × 10^-3 mm²/s; p < 0.0001). In conclusion, IVIM is sensitive in detecting bone marrow ischemia in a piglet model of LCPD.