This study investigated the sensitivity of T1ρ and T2 relaxation time mapping to detect acute ischemic injury to the secondary ossification center (SOC) and epiphyseal cartilage of the femoral head in a piglet model of Legg–Calvé–Perthes disease. Six piglets underwent surgery to induce global right femoral head ischemia and were euthanized 48 h later. Fresh operated and contralateral-control femoral heads were imaged ex vivo with T1, T2, and T1ρ mapping using a 9.4T magnetic resonance imaging scanner. The specimens were imaged a second time after a freeze/thaw cycle and then processed for histology. T1, T2, and T1ρ measurements in the SOC, epiphyseal cartilage, articular cartilage, and metaphysis were compared between operated and control femoral heads using paired t tests. The effects of freeze/thaw, T1ρ spin-lock frequency, and fat saturation were also investigated. Five piglets with histologically confirmed ischemic injury were quantitatively analyzed. T1ρ was increased in the SOC (101 ± 15 vs. 73 ± 16 ms; p = 0.0026) and epiphyseal cartilage (84.9 ± 9.2 vs. 74.3 ± 3.6 ms; p = 0.031) of the operated versus control femoral heads. T2 was also increased in the SOC (28.7 ± 2.0 vs. 22.7 ± 1.7; p = 0.0037) and epiphyseal cartilage (57.4 ± 4.7 vs. 49.0 ± 2.7; p = 0.0041). No changes in T1 were detected. The sensitivities of T1ρ and T2 mapping in detecting ischemic injury were maintained after a freeze/thaw cycle, and T1ρ sensitivity was maintained after varying spin-lock frequency and applying fat saturation. In conclusion, T1ρ and T2 mapping are sensitive in detecting ischemic injury to the SOC and epiphyseal cartilage of the femoral head as early as 48 h after ischemia induction.
Bibliographical noteFunding Information:
We thank Kathy Stuebner, Kelly Bergsrud, Andrea Chehadeh, Sara Pracht, and Amber Winter in the University of Minnesota Veterinary Clinical Investigation Center and Katalin Kovacs, Paula Overn, and Flaviu Tabaran in the University of Minnesota Masonic Cancer Center Comparative Pathology Shared Resource for their assistance. This study was supported by the National Institutes of Health, including the National Institute of Arthritis and Musculoskeletal and Skin Diseases (K01AR070894 and T32AR050938), Office of Research Infrastructure Programs (K01OD021293), and National Institute of Biomedical Imaging and Bioengineering (P41EB027061), as well as the W. M. Keck Foundation. Harry K. W. Kim was supported by the Scottish Rite for Children. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
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PubMed: MeSH publication types
- Journal Article
- Research Support, Non-U.S. Gov't
- Research Support, N.I.H., Extramural