Transplanted Kidneys Fibrosis And Rejection:Evaluation With Reduced Field Of View Intravoxel Incoherent Motion Diffusion-weighted Magnetic Resonance Imaging

Part 1:The evaluation of transplanted kidneys fibrosis with reduced field of view intravoxel incoherent motion diffusion-weighted magnetic resonance imagingPurpose:To determine whether reduced field of view intravoxel incoherent motion diffusion-weighted imaging(rFOV DWI)with multi-b values allows classifying the fibrosis extent in transplanted kidneys.Materials and Methods:Both multi-b rFOV DWI and biopsy were performed on 175 renal transplantation recipients.These patients were grouped according to Banff interstitial fibrosis(ci score).Group ciO included 36 patients with ci 0(<5%of cortex occupied by fibrosis).Group ci1 included 66 patients with ci 1(5%-25%cortex fibrotic).Group ci2 included 39 patients with ci 2(26%-50%cortex fibrotic).Group ci3 included 34 patients with ci 3(>50%cortex fibrotic).The 82 patients followed up in our hospital were divided into stable eGFR group(visits of eGFR ≧45ml/min/1.73m2)and the impaired eGFR group(multiple visits of eGFR<45ml/min/1.73m2).Total apparent diffusion coefficient(ADCT),pure diffusion ADC(ADCD),the pseudo-perfusion(ADCP)and perfusion fraction(FP)of transplanted kidney were calculated and compared among these groups.The diagnostic performance of DWI parameters and renal function related indicators in the diagnosis of renal allograft fibrosis was evaluated.Results:The cortical ADCT(P<0.001)values were statistically significant.The cortical ADCTvalues(1.45±0.18 × 10-3 mm2/s)in group Banff ci 3 were significantly lower than that in group ci0(1.57±0.13 × 10-3 mm2/s),cil(1.58±0.15 × 10-3 mm2/s,both P<0.001).The cortical ADCT values in group ci2(1.49±0.18 × 10-3 mm2/s)were significantly lower than the groups ci0 and ci1(P<0.001).There was no statistical difference in cortical ADCT values between groups ci3 and ci2 or cil and ci0.In addition,it is worth noting that although there was no statistical difference in cortical FP between the groups(P = 0.054),this parameter showed a decreasing trend as the degree of fibrosis increased.Cortical ADCT values(r =-0.286,P<0.001)were mildly inversely correlated with Banff fibrosis scores.The area under the curve of cortical ADCT for the diagnosis of renal allograft fibrosis ci2-3 was 0.68.When the cutoff value of cortical ADCT was 1.50 ×10-3mm2/s,the sensitivity was 58%and the specificity was 73%.Combined with baseline eGFR diagnosis of renal fibrosis ci2-3,the diagnostic sensitivity of baseline eGFR alone was improved(89%vs 74%).There was no significant difference in all DWI parameters between the stable eGFR group and the impaired eGFR group.Conclusions:Given the limitations of allograft biopsy,multi-b rFOV DWI can be used for non-invasive evaluation of transplanted renal fibrosis,which can be used as an important supplement before transplanted kidney biopsy.In addition,DWI may not be able to predict long-term renal function changes in the transplanted kidney.Part 2:The identification of transplanted kidneys rejection type with reduced field of view intravoxel incoherent motion diffusion-weighted magnetic resonance imagingPurpose:To determine whether reduced field of view intravoxel incoherent motion diffusion-weighted imaging(rFOV DWI)with multi-b values allows identifying the subtypes of transplanted kidney rejection.Materials and Methods:Multi-b rFOV DWI and biopsy were performed on 93 renal transplantation recipients.These patients were grouped according to KDIGO CKD guide and Banff criteria.Group 1 included 29 patients without abnormal pathologic findings.Group 2 included 32 patients with acute rejection.Group 3 included 32 patients with chronic rejection.Acute rejection group was further calssified as acute cell rejection,acute humoral rejection,and acute mixed rejection groups.Total apparent diffusion coefficient(ADCT),pure diffusion ADC(ADCD),the pseudo-perfusion(ADCP)and perfusion fraction(FP)of kidney were calculated and compared among these groups.The diagnostic performance of DWI parameters and renal function related indicators in the diagnosis of renal allograft rejection was evaluated.Results:The cortical ADCT value(1.59±0.13 x 10-3 mm2/s)in group without abnormal pathologic findings was significantly higher than that(1.51±0.16 x 10-3 mm2/s)in group with acute rejection(P<0.05).The medullary ADCT value(1.27±0.18× 10-3 mm2/s)in group with chronic rejection was significantly lower than that(1.38±0.12 × 10-3 mm2/s,P<0.05)in group without abnormal pathologic findings.In addition,although there was no statistical difference in cortical FP between the group without abnormal pathologic findings and the group with chronic rejection(P=0.062),this parameter showed a decreasing trend as chronic rejection happened.The area under the curve of medullary ADCT for the diagnosis of renal allograft rejection was 0.66.When the diagnostic threshold of cortical ADCT was 1.22 × 10-3mm2/s,the sensitivity was 41%and the specificity was 97%.Combined with baseline eGFR for the diagnosis of renal allograft rejection,the diagnostic specificity of baseline eGFR alone was improved(93%vs 83%).There was no significant difference in all DWI parameters among the subtypes of rejection.Conclusions:Given a high degree of specificity in identifying renal allograft rejection,multi-b rFOV DWI can be used to non-invasive identification of rejection,which can be used as an important supplement before transplanted kidney biopsy.However,it was not able to distinguish the subtypes of rejection.