Characteristics of diffusion-weighted and blood oxygen level-dependent magnetic resonance imaging in...

Diffusion-weighted (DW) and blood oxygen level-dependent (BOLD) magnetic resonance imaging are classical sequences of functional MR, but the exploration in non-transplanted kidney disease is limited.

To analyze the characteristics of apparent diffusion coefficient (ADC) and R₂* value using DW and BOLD imaging in tubulointerstitial nephritis (TIN).

Four acute TIN, thirteen chronic TIN patients, and four controls were enrolled. We used multiple gradient-echo sequences to acquire 12 T2*-weighted images to calculate the R₂* map. DW imaging acquired ADC values by combining a single-shot spin-echo echo-planar imaging pulse sequence and the additional motion probing gradient pulses along the x,y, z-axes with two b values:0 and 200, as well as 0 and 800 s/mm². ATIN patients performed DW and BOLD magnetic resonance at renal biopsy(T₀) and the third month(T₃). We assessed the pathological changes semiquantitatively, and conducted correlation analyses within functional MR, pathological and clinical indexes.

In ATIN, ADCs were significantly lower(b was 0,200 s/mm², 2.86 ± 0.19 vs. 3.39 ± 0.11, b was 0,800 s/mm², 1.76 ± 0.12 vs. 2.16 ± 0.08, P < 0.05) than controls, showing an obvious remission at T₃. Cortical and medullary R₂* values (CR₂*,MR₂*) were decreased, significant difference was only observed in MR₂*(T₀ 24.3 ± 2.1vs.T₃ 33.1 ± 4.1,P < 0.05). No relationship was found between functional MR and histopathological indexes.MR₂* had a close relationship with eGFR (R = 0.682,P = 0.001) and serum creatinine(R = -0.502,P = 0.012). Patients with lower ADC when b was 0,200 s/mm² showed more increase of ADC(R = -0.956,P = 0.044) and MR₂*(R = -0.949,P = 0.05) after therapy. In CTIN group, lowered MR₂* and MR₂*/CR₂* provided evidence of intrarenal ischemia. CTIN with advanced CKD (eGFR< 45) had significantly lower ADC_b200 value.

We observed the reduction and remission of ADC and R₂* values in ATIN case series. ATIN patients had concurrently decreased ADC_b800 and MR₂*. The pseudo normalization of CR₂* with persistently low MR₂* in CTIN suggested intrarenal hypoxia.