Intravoxel Incoherent Motion (IVIM) Detects Femoral Head Ischemia in a Piglet Model of Legg-Calvé-Perthes Disease.

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 non-contrast-enhanced MRI method to simultaneously measure tissue perfusion and diffusion, can detect femoral head ischemia using a piglet model of LCPD. Twelve six-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 one 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 vs. 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 mm 2 /s; p=0.0026). In contrast, IVIM diffusion coefficient (D s ) and ADC were significantly increased in the ischemic vs. control femoral heads: on average, D s increased 78±21% (ΔD s =0.60±0.14×10 -3 mm 2 /s; p<0.0001) and ADC increased 60±36% (ΔADC=0.50±0.23×10 -3 mm 2 /s; p<0.0001). In conclusion, IVIM is sensitive in detecting bone marrow ischemia in a piglet model of LCPD. This article is protected by copyright. All rights reserved.