Department of Veterinary Clinical Sciences, University of Minnesota, St. Paul, Minnesota, USA.
Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA.
J Orthop Res. 2022 Feb;40(2):484-494. doi: 10.1002/jor.25044. Epub 2021 Apr 16.
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.
本研究旨在探讨 T1ρ 和 T2 弛豫时间mapping 技术探测小猪 Legg-Calvé-Perthes 病模型中继发骨化中心（SOC）和股骨头骺软骨急性缺血损伤的灵敏度。6 头小猪接受手术诱导右侧股骨头整体缺血，并在 48 小时后安乐死。使用 9.4T 磁共振成像扫描仪对新鲜手术侧和对侧正常股骨头进行 T1、T2 和 T1ρ mapping 成像。对标本进行第二次冷冻/解冻循环成像，然后进行组织学处理。使用配对 t 检验比较手术侧和正常侧股骨头 SOC、骺软骨、关节软骨和干骺端的 T1、T2 和 T1ρ 测量值。还研究了冷冻/解冻、T1ρ 自旋锁定频率和脂肪饱和的影响。对 5 头具有组织学证实缺血损伤的小猪进行了定量分析。与正常侧股骨头相比，SOC（101 ± 15 比 73 ± 16 ms；p = 0.0026）和骺软骨（84.9 ± 9.2 比 74.3 ± 3.6 ms；p = 0.031）中 T1ρ 增加。SOC（28.7 ± 2.0 比 22.7 ± 1.7；p = 0.0037）和骺软骨（57.4 ± 4.7 比 49.0 ± 2.7；p = 0.0041）中 T2 也增加。未检测到 T1 变化。冷冻/解冻循环后，T1ρ 和 T2 mapping 探测缺血性损伤的灵敏度保持不变，改变自旋锁定频率和应用脂肪饱和后 T1ρ 灵敏度保持不变。总之，T1ρ 和 T2 mapping 技术在缺血后 48 小时内即可灵敏地探测到头骨 SOC 和骺软骨的缺血性损伤。
