⁸² Rb tissue kinetics in humans

Area of Science:

• Nuclear medicine
• Radiopharmaceutical kinetics
• Organ perfusion imaging

Background:

• Rubidium-82 (82Rb) is a potassium analogue used in myocardial perfusion imaging.
• Understanding 82Rb kinetics in organs beyond the heart is crucial for interpreting imaging data.
• Spleen, liver, and kidney exhibit unique physiological characteristics that may influence tracer uptake.

Purpose of the Study:

• To compare the kinetic behavior of 82Rb in the spleen, liver, and kidney.
• To evaluate the impact of different vasodilators (adenosine and regadenoson) on organ perfusion and 82Rb extraction.
• To characterize the relationship between perfusion and tracer extraction efficiency in these organs.

Main Methods:

• Myocardial stress/rest perfusion imaging with 82Rb was performed in 78 patients using adenosine or regadenoson.
• Hepatic arterial (HAP), splenic (SP), and renal (RP) perfusions were measured using Gjedde-Patlak-Rutland analysis.
• Tissue 82Rb extraction efficiency (E) and extracellular fluid volume (ECV) were calculated.

Main Results:

• Regadenoson increased splenic and renal perfusion, while adenosine decreased them; hepatic perfusion increased with both agents.
• Resting extraction efficiency (E) was high in the kidney (69%) and low in the spleen (26%) and liver (estimated 23%).
• Adenosine increased kidney E to 91% and spleen E to 49%; splenic ECV correlated with SP.

Conclusions:

• Kidney, spleen, and liver demonstrate distinct 82Rb tissue kinetics.
• The kidney exhibits high 82Rb extraction, while the spleen and liver show lower extraction.
• The spleen's erectile nature influences its perfusion and volume dynamics.