Multiple Linear Analysis for Generating Parametric Images of Irreversible Radiotracer

Kim, Su Jin; Lee, Jae Sung; Lee, Won Woo; Kim, Yu Kyeong; Jang, Sung June; Son, Kyu Ri; Kim, Hyo Cheol; Chung, Jin Wook; Lee, Dong Soo

Abstract

PURPOSE: Biological parameters can be quantified using dynamic PET data with compartment modeling and Nonlinear Least Square (NLS) estimation. However, the generation of parametric images using the NLS is not appropriate because of the initial value problem and excessive computation time. In irreversible model, Patlak graphical analysis (PGA) has been commonly used as an alternative to the NLS method. In PGA, however, the start time (t*, time where linear phase starts) has to be determined. In this study, we suggest a new Multiple Linear Analysis for irreversible radiotracer (MLAIR) to estimate fluoride bone influx rate (Ki).
METHODS
[18F]Fluoride dynamic PET scans was acquired for 60 min in three normal mini-pigs. The plasma input curve was derived using blood sampling from the femoral artery. Tissue time-activity curves were measured by drawing region of interests (ROIs) on the femur head, vertebra, and muscle. Parametric images of Ki were generated using MLAIR and PGA methods. RESULT: In ROI analysis, estimated Ki values using MLAIR and PGA method was slightly higher than those of NLS, but the results of MLAIR and PGA were equivalent. Patlak slopes (Ki) were changed with different t* in low uptake region. Compared with PGA, the quality of parametric image was considerably improved using new method.
CONCLUSION
The results showed that the MLAIR was efficient and robust method for the generation of Ki parametric image from [18F]Fluoride PET. It will be also a good alternative to PGA for the radiotracers with irreversible three compartment model.