A comparison of PET imaging characteristics of various copper radioisotopes.
OBJECTIVE
PET radiotracers which incorporate longer-lived radionuclides enable biological processes to be studied over many hours, at centres remote from a cyclotron. This paper examines the radioisotope characteristics, imaging performance, radiation dosimetry and production modes of the four copper radioisotopes, ( 60)Cu,( 61)Cu,( 62)Cu and( 64)Cu, to assess their merits for different PET imaging applications.


METHODS
Spatial resolution, sensitivity, scatter fraction and noise-equivalent count rate (NEC) are predicted for( 60)Cu,( 61)Cu,( 62)Cu and( 64)Cu using a model incorporating radionuclide decay properties and scanner parameters for the GE Advance scanner. Dosimetry for( 60)Cu,( 61)Cu and( 64)Cu is performed using the MIRD model and published biodistribution data for copper(II) pyruvaldehyde bis(N(4)-methyl)thiosemicarbazone (Cu-PTSM).


RESULTS
(60)Cu and( 62)Cu are characterised by shorter half-lives and higher sensitivity and NEC, making them more suitable for studying the faster kinetics of small molecules, such as Cu-PTSM.( 61)Cu and( 64)Cu have longer half-lives, enabling studies of the slower kinetics of cells and peptides and prolonged imaging to compensate for lower sensitivity, together with better spatial resolution, which partially compensates for loss of image contrast.( 61)Cu-PTSM and( 64)Cu-PTSM are associated with radiation doses similar to [(18)F]-fluorodeoxyglucose, whilst the doses for( 60)Cu-PTSM and( 62)Cu-PTSM are lower and more comparable with H(2) (15)O.


CONCLUSIONS
The physical and radiochemical characteristics of the four copper isotopes make each more suited to some imaging tasks than others. The results presented here assist in selecting the preferred radioisotope for a given imaging application, and illustrate a strategy which can be extended to the majority of novel PET tracers.
Williams
Heather Ann
HA
Christie Hospital NHS Trust, North Western Medical Physics, Wilmslow Road, Manchester, M20 4BX, United Kingdom. hwilliams@physics.org
Robinson
Simon
S
Julyan
Peter
P
Zweit
Jamal
J
Hastings
David
D
D003198:Computer Simulation; D003301:Copper Radioisotopes / Q000032:analysis / Q000493:pharmacokinetics*; D006207:Half-Life; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008954:Models, Biological; D049268:Positron-Emission Tomography / Q000379:methods*; D011829:Radiation Dosage; D011874:Radiometry; D019275:Radiopharmaceuticals / Q000032:analysis / Q000493:pharmacokinetics
D003301:Copper Radioisotopes; D019275:Radiopharmaceuticals