Objective

To determine if the quantitative MRI techniques T2 and T1ρ mapping are sensitive to ischemic injury to epiphyseal cartilage in vivo in a piglet model of Legg-Calvé-Perthes disease using a clinical 3T MRI scanner. We hypothesized that T2 and T1ρ relaxation times would be increased in the epiphyseal cartilage of operated vs contralateral-control femoral heads 1 week following onset of ischemia.

Design

Unilateral femoral head ischemia was surgically induced in eight piglets. Piglets were imaged 1 week post-operatively in vivo at 3T MRI using a magnetization-prepared 3D fast spin echo sequence for T2 and T1ρ mapping and a 3D gradient echo sequence for cartilage segmentation. Ischemia was confirmed in all piglets using gadolinium contrast-enhanced MRI. Median T2 and T1ρ relaxation times were measured in the epiphyseal cartilage of the ischemic and control femoral heads and compared using paired t-tests. Histological assessment was performed on a subset of five piglets.

Results

T2 and T1ρ relaxation times were significantly increased in the epiphyseal cartilage of the operated vs control femoral heads (ΔT2 = 11.9 ± 3.7 ms, 95% CI = [8.8, 15.0] ms, P < 0.0001; ΔT1ρ = 12.8 ± 4.1 ms, 95% CI = [9.4, 16.2] ms, P < 0.0001). Histological assessment identified chondronecrosis in the hypertrophic and deep proliferative zones within ischemic epiphyseal cartilage.

Conclusions

T2 and T1ρ mapping are sensitive to ischemic injury to the epiphyseal cartilage in vivo at clinical 3T MRI. These techniques may be clinically useful to assess injury and repair to the epiphyseal cartilage to better stage the extent of ischemic damage in Legg-Calvé-Perthes disease.

中文翻译：

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定量 T2 和 T1ρ 绘图对 Legg-Calvé-Perthes 病体内仔猪模型中骨骺软骨缺血性损伤敏感

客观的

使用临床 3T MRI 扫描仪确定定量 MRI 技术 T2 和 T1ρ 映射是否对 Legg-Calvé-Perthes 病仔猪模型体内骨骺软骨缺血性损伤敏感。我们假设缺血发生后 1 周，手术股骨头骨骺软骨的 T2 和 T1ρ 松弛时间会增加，与对侧对照股骨头相比。

设计

通过手术使八头仔猪发生单侧股骨头缺血。术后 1 周，使用磁化准备的 3D 快速自旋回波序列进行 T2 和 T1ρ 映射，并使用 3D 梯度回波序列进行软骨分割，在 3T MRI 中对仔猪进行体内成像。使用钆对比增强 MRI 证实所有仔猪均出现缺血。测量缺血股骨头和对照股骨头的骨骺软骨中的中位 T2 和 T1ρ 松弛时间，并使用配对t检验进行比较。对五只仔猪的子集进行组织学评估。

结果

与对照股骨头相比，手术股骨头骨骺软骨的 T2 和 T1ρ 松弛时间显着增加（ΔT2 = 11.9 ± 3.7 ms，95% CI = [8.8, 15.0] ms，P < 0.0001；ΔT1ρ = 12.8 ± 4.1 ms ，  95 % CI = [9.4, 16.2] 毫秒，P  < 0.0001）。组织学评估发现缺血性骨骺软骨内的肥厚区和深层增殖区存在软骨坏死。

结论

T2 和 T1ρ 映射对临床3T MRI 中体内骨骺软骨的缺血性损伤敏感。这些技术在临床上可能有助于评估骨骺软骨的损伤和修复，以更好地分期 Legg-Calvé-Perthes 病的缺血性损伤程度。