Quantitative18F-fluorocholine positron emission tomography for prostate cancer: correlation between kinetic parameters and Gleason scoring.
BACKGROUND
The use of radiolabeled choline as a positron emission tomography (PET) agent for imaging primary tumors in the prostate has been evaluated extensively over the past two decades. There are, however, conflicting reports of its sensitivity and the relationship between choline PET imaging and disease staging is not fully understood. Moreover, relatively few studies have investigated the correlation between tracer uptake and histological tumor grade. This work quantified18F-fluorocholine in tumor and healthy prostate tissue using pharmacokinetic modeling and stratified uptake parameters by histology grade. Additionally, the effect of scan time on the estimation of the kinetic exchange rate constants was evaluated, and the tracer influx parameters from full compartmental analysis were compared to uptake values quantified by Patlak and standardized uptake value (SUV) analyses.18F-fluorocholine was administered as a 222 MBq bolus injection to ten patients with biopsy-confirmed prostate tumors, and dynamic PET data were acquired for 60 min. Image-derived arterial input functions were scaled by discrete blood samples, and a 2-tissue, 4-parameter model accounting for blood volume (2T4k+Vb) was used to perform fully quantitative compartmental modeling on tumor, healthy prostate, and muscle tissue. Subsequently, all patients underwent radical prostatectomy, and histological analyses were performed on the prostate specimens; kinetic parameters for tumors were stratified by Gleason score. Correlations were investigated between compartmental K1and Kiparameters and SUV and Patlak slope; the effect of scan time on parameter bias was also evaluated.


RESULTS
Choline activity curves in seven tumors, eight healthy prostate regions, and nine muscle regions were analyzed. Net tracer influx was generally higher in tumor relative to healthy prostate, with the values in the highest grade tumors markedly higher than those in lower grade tumors. Influx terms from Patlak and full compartmental modeling showed good correlation within individual tissue groups. Kinetic parameters calculated from the entire 60-min scan data were accurately reproduced from the first 30 min of acquired data (R2≈ 0.9).


CONCLUSIONS
Strong correlations were observed between Kiand Patlak slope in tumor tissue, and K1and SUV were also correlated but to a lesser degree. Reliable estimates of all kinetic parameters can be achieved from the first 30 min of dynamic18F-choline data. Although SUV, K1, Ki, and Patlak slope were found to be poor differentiators of low-grade tumor compared to healthy prostate tissue, they are strong indicators of aggressive disease.
A*STAR-NUS Clinical Imaging Research Centre, Centre for Translational Medicine (MD6), 14 Medical Drive, #B1-01, Singapore, 117599, Singapore. dnrjds@nus.edu.sg.|Department of Diagnostic Radiology, National University Hospital, Singapore, Singapore. dnrjds@nus.edu.sg.
Joshua D
JD
Schaefferkoetter
Department of Urology, National University Health System, Singapore, Singapore.
Ziting
Z
Wang
A*STAR-NUS Clinical Imaging Research Centre, Centre for Translational Medicine (MD6), 14 Medical Drive, #B1-01, Singapore, 117599, Singapore.
Mary C
MC
Stephenson
A*STAR-NUS Clinical Imaging Research Centre, Centre for Translational Medicine (MD6), 14 Medical Drive, #B1-01, Singapore, 117599, Singapore.
Sharmili
S
Roy
Siemens Healthcare Molecular Imaging, Knoxville, TN, 37919, USA.
Maurizio
M
Conti
Siemens Healthcare Molecular Imaging, Knoxville, TN, 37919, USA.
Lars
L
Eriksson
A*STAR-NUS Clinical Imaging Research Centre, Centre for Translational Medicine (MD6), 14 Medical Drive, #B1-01, Singapore, 117599, Singapore.|Department of Diagnostic Radiology, National University Hospital, Singapore, Singapore.
David W
DW
Townsend
Department of Pathology, National University Health System, Singapore, Singapore.
Thomas
T
Thamboo
Department of Urology, National University Health System, Singapore, Singapore.
Edmund
E
Chiong
Choline; Histology; PET; Prostate cancer; Tracer kinetic modeling