Feasibility of parametric imaging in multi-bed dynamic human FDG PET

Objectives The Gjedde-Patlak plot (GP plot) is commonly used in quantitative dynamic FDG PET studies. The uptake rate constant K_i (mL/min/100 mL) can be theoretically estimated by the GP plot without knowledge of the full time course of tissue tracer kinetics, and this serves as a basis for the use of the GP plot to quantify PET scans with multi-bed positions. Our objective was to investigate the feasibility of parametric imaging for voxel-wise quantification of multi-bed dynamic FDG PET.

Methods Twelve thoracic oncology FDG PET studies were performed on a GE Advance scanner at a single bed position. Dynamic images (256x256x35, voxel size 2x2x4.25 mm³) of 19 frames over 60 min (6x10s,3x20s,2x90s,2x150s,2x300s,4x600s) were reconstructed using an OSEM algorithm. To obtain the blood input function for the GP plot, ROIs of the left ventricle (LV) were drawn manually on the first 2 min images. The radioactivity distribution was used to calculate the center of mass of LV (mcLV). A volume (5x5x3) centered at mcLV was then copied to dynamic images to generate a time activity curve to be used for the input function. The GP plot with t* ≥ 10 min was used to generate K_i images. A 2 bed positions protocol was used to extract the samples from the continuous 10 to 60 min single-bed dynamic PET data without replacement. The SUV and K_i images calculated from the 10 to 60 min single-bed scans were used as reference for comparison.

Results The K_i images generated from the samples of the 2 bed positions protocol were comparable to those generated from the standard continuous single-bed position data acquisition protocol. The K_i images showed higher contrast than SUV images to distinguish tumors from normal tissue.

Conclusions The GP plot is a appropriate graphical method to generate reliable K_i images for voxel-wsie quantification of clinical dynamic FDG PET images obtained at multi-bed positions. Work in progress includes optimization of the data acquisition protocol, 4D image reconstruction, and the parametric imaging algorithm.

Research Support KA24 DA00042(DFW)