Renal blood flow measurement by positron emission tomography using ¹⁵O-labeled water

Renal blood flow measurement by positron emission tomography using ¹⁵O-labeled water.

Background

Only few noninvasive methods have the potential to quantitate renal blood flow (RBF) in humans. Positron emission tomography (PET) is a clinical imaging method that can be used to measure the tissue blood flow noninvasively. The purpose of this study was to validate PET measurement of RBF using ¹⁵O-labeled water (H₂¹⁵O), a tracer that allows repeated measurements at short time intervals.

Methods

RBF was measured in six pigs by PET and by radioactive microspheres (MS). Three measurements were performed in each pig at baseline (BL), during vascular expansion and dopamine infusion (DA; 20 μg · kg^-1 · min^-1 intravenously), and during angiotensin II (Ang II) infusion (50 ng · kg^-1 · min^-1 intravenously). RBF was estimated from aortic and renal tracer kinetics using a model adapted from the blood flow model described by Kety and Smith.

Results

PET and MS values correlated strongly (y = 0.79x + 42, r = 0.93, P < 0.0001) over the RBF range from 100 to 500 mL · min^-1 · 100 g^-1. Pharmacologically induced changes were significant and were measured equally well by PET and MS: 38 and 39%, respectively, below BL (P < 0.005 and P < 0.05) under Ang II, and 47 and 48%, respectively, above BL (P < 0.005 and P < 0.01) under DA. A Bland and Altman representation showed a low average difference of -17 ± 45 mL · min^-1 · 100 g^-1 (mean ± SD).

Conclusion

To our knowledge, this study provides the first validation of RBF measurement by PET using H₂¹⁵O over a large range of RBF values (100 to 500 mL · min^-1 · 100 g^-1), which correspond to RBF values in both healthy subjects and in patients suffering from chronic renal failure.