Correlation of biexponential diffusion parameters with arterial spin-labeling perfusion MRI: results in transplanted kidneys.

PURPOSE: The purpose of the present study was to explore the correlation between diffusion parameters assessed by biexponential analysis and the tissue perfusion measured by arterial spin labeling (ASL) imaging in renal allografts. MATERIAL AND METHODS: Seventeen recipients of renal allograft (11 men and 6 women; mean [SD] age, 53.6 [14.1] years) were included in this study. For diffusion-weighted imaging, a paracoronal echo-planar imaging sequence was acquired with 16 b values (range, b = 0-750 s/mm²) and 6 averages at 1.5 T. For the quantitative assessment of transplanted kidney perfusion, a flow-sensitive alternating inversion recovery true fast imaging with steady precession-ASL technique was applied. No respiratory gating was used. For quantitative analysis, region of interest measurements were performed on parameter maps. The Spearman correlation coefficients were calculated to determine the association between mean serum creatinine levels, estimated glomerular filtration rate, the apparent diffusion coefficient (ADC) of pure diffusion, the ADC of pseudodiffusion, the monoexponential ADC, the fraction of pseudodiffusion, and the tissue perfusion ASL values. RESULTS: In the renal cortex, the fraction of pseudodiffusion was 17.4% ± 4.0%, the apparent diffusion coefficient of pure diffusion was 160.7 ± 15.0 × 10⁻5 mm²/s, the monoexponential ADC was 193.2 ± 16.7 × 10⁻5 mm²/s, and the ADC of pseudodiffusion was 1421.0 ± 237.7 × 10⁻5 mm²/s. Mean cortical perfusion of renal allografts, as assessed with ASL imaging, was 247.2 ± 75.0 mL/100 g/min. There was a significant correlation between ASL perfusion and the fraction of pseudodiffusion (r = 0.68; P < 0.005) but not with the other diffusion coefficients. Both ASL perfusion and the fraction of pseudodiffusion exhibited a significant correlation with serum creatinine levels (r = 0.51 and r= 0.53, respectively; P < 0.05) and estimated glomerular filtration rate (r = 0.63 and r = 0.54, respectively; P < 0.05). CONCLUSIONS: This is the first study that shows a significant correlation between renal allograft perfusion, as assessed with ASL perfusion measurements, and the fraction of pseudodiffusion derived from biexponential diffusion-weighted imaging measurements.

Autotransplantation for the treatment of severe renal artery stenosis in a solitary kidney after repeated percutaneous transluminal angioplasty: a case report.

A 66-year-old female suffering from massive atherosclerosis with a long history of renal artery stenosis in the left solitary kidney was admitted to reevaluate an in-stent restenosis. Advanced peripheral arterial disease had formerly been treated by aortobifemoral bypass surgery and a highly eccentric infrarenal abdominal aortic stenosis of 70 - 80% had been treated by patch angioplasty. In this patient several percutaneous transluminal renal angioplasties after a former stent deployment had resulted in recurrent in-stent restenoses. The renal artery stenosis was reevaluated and a re-angioplasty attempt was unsuccessful due to technical failure. Blood pressure remained difficult to manage. Renal function decreased as a result of presumed acute renal failure. A further progression of the renal artery stenosis was found. Autotransplantation to the left iliac fossa was done, because aortorenal bypass was considered impossible. Renal function normalized and follow-up Doppler ultrasonography examinations revealed a newly developed ostial anastomotic stenosis of 60 - 70%. While medical therapy and percutaneous transluminal angioplasty with stent deployment are common treatment options, surgical interventions are reserved for cases of complex stenoses. Autotransplantation as a complex option in the treatment of renal artery stenosis seems to be an adequate alternative in patients with severe, generalized atherosclerosis after failure of interventional procedures and the impossibility of standard surgical techniques.