Detection of renal allograft rejection using blood oxygen level-dependent and diffusion weighted magnetic resonance imaging: a retrospective study

Abstract

Background: Acute rejection (AR) and acute tubular necrosis (ATN) are main causes of early renal allograft dysfunction. Blood oxygen level-dependent magnetic resonance imaging (BOLD MRI) and Diffusion weighted (DW) MRI can provide valuable information about changes of oxygen bioavailability and water diffusion by measuring R2* or apparent diffusion coefficient (ADC) respectively. We aimed to determine the value of BOLD MRI and DW MRI in detecting causes for early allograft dysfunction in renal allograft recipients.

Methods: Fifty patients received renal allografts from deceased donors were analyzed, including 35 patients with normal renal function (control group), 10 AR patients and 5 ATN patients. Cortical R2* (CR2*) and medullary R2* (MR2*) were measured by BOLD MRI. Ten diffusion gradient b values (0, 5, 10, 20, 50, 100, 200, 400, 800, 1200s/mm2) were used in DW MRI. ADC values were measured in renal cortex (CADC) and medulla (MADC). CADCl and MADCl were measured under low b values (b ≤ 200 s/mm2), while CADCh and MADCh were measured under high b values (b > 200 s/mm2).

Results: MR2* was significantly lower in AR group (18.2 ± 1.5/s) than control group (23.8 ± 5.0/s, p = 0.001) and ATN group (25.8 ± 5.0/s, p = 0.004). There was a tendency of lower levels on CADCl, MADCl, CADCh or MADCh in AR group than in control group. There were no differences on ADC values between AR group and ATN group.

Conclusions: BOLD MRI was a valuable method in detection of renal allografts with acute rejection.

Figure 1

The representative R2* maps and ADC maps of renal allografts in AR group, ATN group and control group. A, the representative R2* map (A1) and ADC maps (A2, ADC map of low b values; A3, ADC map of high b values) of normal control allograft; B, the representative R2* map (B1) and ADC maps (B2, ADC map of low b values; B3, ADC map of high b values) of AR allograft; C, the representative R2* map (C1) and ADC maps (C2, ADC map of low b values; C3, ADC map of high b values) of ATN allograft. In R2* maps, the coronal section of the kidney is shown. The change of color from blue to green, orange, and then red represents the change of R2* value from lower to higher. There were more blue regions in the medulla of AR allograft (B1) and more green regions in the medulla of ATN allograft (C1), compared with normal control allograft (A1). In ADC maps, the transverse section of the kidney is shown. The change of color from green to orange, and then red represents the change of ADC value from lower to higher. There were less red regions and more green regions in AR allograft (B2, B3) and ATN allograft (C2, C3) compared with normal control allograft (A2, A3), regardless of low or high b values.