Rodent rhabdomyosarcoma: comparison between total choline concentration at H-MRS and [18F]-fluoromethylcholine uptake at PET using accurate methods for collecting data.
OBJECTIVE
To compare choline concentration/amount at proton magnetic resonance spectroscopy (H-MRS) and [18F]-fluoromethylcholine (FCH) uptake at positron emission tomography (PET) in a tumour animal model.


METHODS
Twenty-two rats bearing grafted syngenic rhabdomyosarcoma in both thighs were examined on a 3T MR system and on a small animal PET system. Total choline concentration was measured on proton MR spectra using a so-called 'best internal fitting' volume of interest. Choline uptake was expressed as mean and maximum standardized uptake value (SUV and SUVmax, respectively) and as the percent of injected dose (%ID) after tumour delineation on fused PET-MR images. Data sets were displayed on standard scatter plots.


RESULTS
Thirty-six tumours were available for analysis. The area under the curve of the 3.2 ppm choline peak ranged from 69 to 476 (mean, 192) in arbitrary units. Mean SUV values ranged from 0.05 to 0.49 (mean, 0.19) and the %ID from 0.05 to 2.28 (mean, 0.54). Scatter plots failed to reveal quantitative relationship between choline concentration and uptake. Empirically data-driven cut-off lines applied to choline amount (choline concentration x tumour volume) versus choline uptake suggested a paradoxically negative relationship.


CONCLUSIONS
Total choline concentration did not correlate with FCH uptake in a tumour experimental model. A negative feedback of high values of total choline amount on cellular FCH uptake seemed to be present.
Rommel
Denis
D
Cliniques Universitaires Saint-Luc, Department of Radiology and Medical Imaging, Université Catholique de Louvain, Avenue Hippocrate, 10, 1200 Brussels, Belgium. denis.rommel@uclouvain.be
Bol
Anne
A
Abarca-Quinones
Jorge
J
Peeters
Frank
F
Robert
Annie
A
Labar
Daniel
D
Galant
Christine
C
Gregoire
Vincent
V
Duprez
Thierry
T
D000818:Animals; D002794:Choline / Q000031:analogs & derivatives*; D004195:Disease Models, Animal; D005462:Fluorine Radioisotopes; D009682:Magnetic Resonance Spectroscopy; D049268:Positron-Emission Tomography / Q000379:methods*; D051381:Rats; D012208:Rhabdomyosarcoma / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000601:surgery
D005462:Fluorine Radioisotopes; C516370:fluoromethylcholine; D002794:Choline