**5.9. Imaging allograft function**

A rather unspecific but reasonable approach is to simply determine graft function as a surro‐ gate for stable function or (acute) graft affection.

Especially scintigraphic methods have been established for the assessment of renal function. Primarily, two types of imaging are common: static and dynamic. 99mTc-dimercaptosuccinic acid (DMSA) is the tracer used in static imaging allowing on the one hand identification of pathological conditions such as anatomical abnormalities or scarring, on the other hand accu‐ rate assessment of the differential function of the kidneys [57]. DMSA uptake correlates with the effective renal plasma flow, glomerular filtration rate, and creatinine clearance. Therefore, DMSA has been successfully applied in the evaluation of renal function in living donors (before and after transplantation) and in kidney recipients [58]. For dynamic imaging 99mTc-mercap‐ toacetyltriglycine (MAG-3) and diethylenetriaminepentaacetic acid (DTPA) are the most com‐ monly used tracers, whereas MAG-3 is going to replace DTPA because of superior extraction efficiency. It was proposed that MAG-3 scintigraphy can be useful for discrimination of AR from ATN [59]. Despite a reasonable perfusion and tracer extraction in ATN as assessed in these studies, tracer excretion rate is low, whereas one of the typical findings in AR is impaired perfusion. This fact was already taken into account by Hilson *et al.* in the seventies who de‐ veloped a DTPA-based perfusion index which allows separation of rejection from ATN and, particularly, rejection from healthy kidneys [60]. These findings are somehow discrepant to typical findings in ultrasound when assessing RI which reflects renal perfusion as well. High RIs can be observed in ATN as well as in AR denying a differentiation of these entities by ultrasound-based measure of renal perfusion. Potentially, the modified renal perfusion index using 18F-fluoride developed by us can be used for further clarification [61]. Aside from this recent studies using PET for the evaluation of renal function other approaches have been emerged. Renal blood flow for instance was successfully measured with H2 15O in rats and man [62,63]. Furthermore, we established 18F-fluoride clearance for assessment of renal function in different renal failure models including AR [43,46]. As said before, decreased renal function is not disease specific but can assist in the differential diagnoses of AR.

**Author details**

Alexander Grabner1

Münster,, Germany

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Stefan Reuter1\*

, Dominik Kentrup1

\*Address all correspondence to: sreuter@uni-muenster.de

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1 Department of Internal Medicine D, Experimental Nephrology, University of Münster,

2 Department of Nuclear Medicine, University of Münster, Münster,, Germany

3 European Institute for Molecular Imaging, University of Münster, Münster, Germany

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