Renal tubular dilation and fibrosis after unilateral ureter obstruction revealed by relaxometry and spin-lock exchange MRI,NMR in Biomedicine

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Renal tubular dilation and fibrosis after unilateral ureter obstruction revealed by relaxometry and spin-lock exchange MRI
NMR in Biomedicine ( IF 2.7 ) Pub Date : 2021-05-08 , DOI: 10.1002/nbm.4539
Feng Wang _{1,

2,

3} , Tadashi Otsuka ₄ , Keiko Takahashi ₄ , Chikage Narui ₄ , Daniel C Colvin ₁ , Raymond C Harris _{3,

4} , Takamune Takahashi _{3,

4} , John C Gore _{1,

2,

5}

Affiliation

We evaluated the use of quantitative MRI relaxometry, including the dispersion of spin-lock relaxation with different locking fields, for detecting and assessing tubular dilation and fibrosis in a mouse model of unilateral ureter obstruction (UUO). C57BL/6 J and BALB/c mice that exhibit different levels of tubular dilation and renal fibrosis after UUO were subjected to MR imaging at 7 T. Mice were imaged before UUO surgery, and at 5, 10 and 15 days after surgery. We acquired maps of relaxation rates and fit the dispersion of spin-lock relaxation rates R_1ρ at different locking fields (frequencies) to a model of exchanging water pools, and assessed the sensitivity of the derived quantities for detecting tubular dilation and fibrosis in kidney. Histological scores for tubular dilation and fibrosis, based on luminal space and positive fibrotic areas in sections, were obtained for comparison. Histology detected extensive tubular dilation and mild to moderate fibrosis in the UUO kidneys, in which enlargement of luminal space, deposition of collagen, and reductions in capillary density were observed in the cortex and outer stripe of the outer medulla. Relaxation rates R₁, R₂ and R_1ρ clearly decreased in these regions of UUO kidneys longitudinally. While R₁ showed the highest detectability to tubular dilation and overall changes in UUO kidneys, S_ρ, a parameter derived from R_1ρ dispersion data, showed the highest correlation with renal fibrosis in UUO. While relaxation parameters are sensitive to tubular dilation in UUO kidneys, S_ρ depends primarily on the average exchange rate between water and other chemically shifted resonances such as hydroxyls and amides, and provides additional specific information for evaluating fibrosis in kidney disease.

中文翻译：

弛豫测量和自旋锁交换 MRI 显示单侧输尿管梗阻后肾小管扩张和纤维化

我们评估了定量 MRI 松弛测量的使用，包括不同锁定场的自旋锁定松弛的分散，用于检测和评估单侧输尿管梗阻 (UUO) 小鼠模型中的管状扩张和纤维化。对 UUO 后表现出不同水平的肾小管扩张和肾纤维化的 C57BL/6 J 和 BALB/c 小鼠进行 7 T 的 MR 成像。在 UUO 手术前以及手术后 5、10 和 15 天对小鼠进行成像。我们获取了弛豫率图，并将不同锁定场（频率）下的自旋锁弛豫率R _{1 ρ}的离散度拟合到交换水池模型，并评估了导出量用于检测肾小管扩张和纤维化的灵敏度。获得基于管腔空间和切片中阳性纤维化区域的肾小管扩张和纤维化的组织学评分以进行比较。组织学检测发现UUO肾脏存在广泛的肾小管扩张和轻度至中度纤维化，其中在皮质和外髓质的外条纹中观察到管腔空间扩大、胶原沉积和毛细血管密度减少。在 UUO 肾脏的这些区域中，松弛率R ₁ 、 R ₂和R _{1 ρ}纵向明显下降。虽然R ₁显示出对 UUO 肾脏中肾小管扩张和整体变化的最高可检测性，但源自R _{1 ρ}分散数据的参数S _ρ显示出与 UUO 肾纤维化的最高相关性。虽然弛豫参数对 UUO 肾脏中的肾小管扩张敏感，但S _ρ主要取决于水与其他化学位移共振（例如羟基和酰胺）之间的平均交换率，并为评估肾脏疾病的纤维化提供了额外的具体信息。

更新日期：2021-07-02

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