Serial analysis of renal blood flow by positron tomography with rubidium-82

Abstract

To determine whether renal blood flow can be measured by positron-emission tomography (PET) during constant infusion of rubidium-82 (82Rb) using a steady-state kinetic model, studies were performed in 10 dogs at control (n = 10), during mild flow reduction (n = 7), during severe flow reduction (n = 10), and after reperfusion of the kidney (n = 3). PET data were quantified to determine mean concentration of 82Rb (Ct) in each transverse section of the kidney. The arterial concentration (Ca) of 82Rb was measured by well counting of arterial blood samples during the equilibrium scan. 82Rb renal uptake (Ct/Ca) correlated nonlinearly with microsphere renal blood flow according to a steady-state kinetic model (r = 0.90). 82Rb estimated flow was 3.16 +/- 1.36 ml X min-1 X g-1 at control and 1.56 +/- 0.57 and 0.37 +/- 0.59 during mild and severe flow reductions, respectively. Microsphere determined flow was 2.89 +/- 0.77 ml X min-1 X g-1 at control, 1.58 +/- 0.42 at mild reduction, and 0.27 +/- 0.49 at severe reduction. In the occlusion and reperfusion model, the 82Rb estimated flow during occlusion was 0.21 +/- 0.15 ml X min-1 X g-1 and on reperfusion went up to 2.13 +/- 1.08. The contralateral kidney demonstrated reductions in the 82Rb estimated flow of 3.02 +/- 1.62 ml X min-1 X g-1 (63%) and 2.92 +/- 0.89 (61%) during mild and severe flow reductions, respectively. We conclude that PET with 82Rb permits serial quantitative assessment of renal flood flow.

Measurement of kidney perfusion in critically ill Patients

“…The first technique makes use of a highly extracted blood flow tracer such as rubidium-82 [38]. This method has been used in animal models of renal artery obstruction, occlusion and reperfusion [39]. The second technique makes use of ultra-short-lived tracers, such as oxygen-15-labelled water (half-life of 2 min) [40].…”

Measurement of Kidney Perfusion in Critically Ill Patients

“…Th e fi rst technique makes use of a highly extracted blood fl ow tracer such as rubidium-82 [38]. Th is method has be en used in animal models of renal artery obstruction, occlusion and reperfusion [39]. Th e second techniq ue makes use of ultrashort-lived tracers, such as oxygen-15-label led water (half-life of 2 min) [40].…”

Scintigraphic Imaging of Renal Function

“…For the bolus injection technique, there are two classes of tracer: firstly, so-called ‘chemical’ microspheres, which have a high extraction and retention in tissue [9, 10, 11, 12, 13, 14], and secondly, highly diffusible tracers with perfusion-limited transport between tissue and blood, such as labelled water [14, 15, 16, 17, 18, 19]. The bolus injection approach can be based on either class of tracer but the steady-state technique must use an ultra-short-lived tracer [20, 21, 22, 23]. …”

“…Measurement of tissue perfusion at steady state makes use of ultra-short-lived tracers such as oxygen-15-labelled water [20], which has a half-life of 2 min, and rubidium-82 [21, 22, 23], which has a half-life of 75 s.…”

“…However, for the kidney, λ is only modest and so C τ /C a is a non-linear function of perfusion, as it is for labelled water, and equation 4 needs to be used [22, 23]. Unfortunately, however, λ, like E, is also likely to be inversely dependent on perfusion.…”