Development of a non-radiometric method for measuring the arterial input function of a C-11-labeled PET radiotracer

: H. Umesha Shetty, Sami S. Zoghbi, Cheryl L. Morse, Aneta Kowalski, Jussi Hirvonen, Robert B. Innis, Victor W. Pike

Publisher: NATURE RESEARCH

: 2020

: Scientific Reports

: SCIENTIFIC REPORTS

: SCI REP-UK

: ARTN 17350

: 10

: 1

: 11

: 2045-2322

DOI: https://doi.org/10.1038/s41598-020-73646-4

: https://research.utu.fi/converis/portal/detail/Publication/50706687

Positron emission tomography (PET) uses radiotracers to quantify important biochemical parameters in human subjects. A radiotracer arterial input function (AIF) is often essential for converting brain PET data into robust output measures. For radiotracers labeled with carbon-11 (t(1/2)=20.4 min), AIF is routinely determined with radio-HPLC of blood sampled frequently during the PET experiment. There has been no alternative to this logistically demanding method, neither for regular use nor validation. A C-11-labeled tracer is always accompanied by a large excess of non-radioactive tracer known as carrier. In principle, AIF might be obtained by measuring the molar activity (A(m); ratio of radioactivity to total mass; Bq/mol) of a radiotracer dose and the time-course of carrier concentration in plasma after radiotracer injection. Here, we implement this principle in a new method for determining AIF, as shown by using [C-11]PBR28 as a representative tracer. The method uses liquid chromatography-tandem mass spectrometry for measuring radiotracer A(m) and then the carrier in plasma sampled regularly over the course of a PET experiment. A(m) and AIF were determined radiometrically for comparison. The new non-radiometric method is not constrained by the short half-life of carbon-11 and is an attractive alternative to conventional AIF measurement.

s41598-020-73646-4.pdf