EJNMMI physics · 2025
Regional impact of time-to-equilibrium on indirect Patlak whole-body parametric imaging: a multi-tissue class analysis at the entire body level.
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Sivapathasundaram Abarnaa, Buffon Agnieszka, Ghidaglia Jérôme, Jentreau Yannick, Gomez Léa, Jamet Axelle, Beau Maïwenn, Da Fonseca Natacha, Harnais Kevin, Onephandara Stéphane, Makhlouf Widad, En Nourhi Karim, Durand Emmanuel, Faure Sylvain, Besson Florent L
Аннотация
PURPOSE: Patlak parametric imaging is widely employed for kinetic modeling due to its simplicity and robustness. The time-to-equilibrium (t*), which must be defined to estimate kinetic parameters, is currently set empirically and uniformly across the entire body. In this study, we evaluate the regional impact of varying t* values on kinetic parameter estimates using a multi-tissue segmentation approach at the whole-body level.
METHODS: Data from 53 patients who underwent one-hour dynamic 18 F-FDG PET/CT scans were retrospectively analyzed. Parametric maps of the net influx rate (Ki) and blood distribution volume (dv) were calculated for four t* values (10, 20, 30, and 45 min) using in-house software (PET KinetiX). Voxel-wise Ki and dv values were extracted from 10 predefined tissue structures through automated segmentation. Using t* = 30 min as the widely accepted reference, relative mean errors and relative absolute mean errors of Ki and dv estimated at t*shifts = 10, 20 and 45 min were calculated for each tissue. Pearson correlation coefficients between Ki or dv reference values and those estimated at t* shifts = 10, 20, and 45 min were also computed.
RESULTS: Compared to the reference t*30, Ki estimates ranged from - 21.4% (liver) to 7.3% (SAT) at t*10, and from - 13.8% (lungs) to 2.4% (brain) at t*20. Median absolute bias was 12.8% at t*10 (6.5% brain to > 25% liver) and 8.6% at t*20 (3.2% brain to > 15% lungs and liver). At t*45, Ki was consistently overestimated, with a median bias of 19.4% (2.7% brain to > 33% lungs and liver) and median absolute bias of 19.8% (5.5% brain to > 33% lungs and liver). For dv, biases ranged from - 25.2% (brain) to 8.6% (spleen) at t*10; - 13.7% (brain) to 5.7% (lungs) at t*20; - 15.5% (liver) to 8.8% (brain) at t*45. Median absolute biases were 14.0% at t*10 (9.8% heart to 25.2% brain), 9.4% at t*20 (7.7% heart to 14.1% brain), and 15% at t*45 (12.4% skeletal muscle to 18.5% brain). Regardless of t*, Ki values exhibited strong linear correlations (r > 0.7) across all organs, whereas dv correlations showed greater variability, falling below 0.7 in 80% of organs at t*45.
CONCLUSION: Kinetic parameter sensitivity to time-to-equilibrium (t*) varies across organs in Patlak whole-body parametric imaging, underscoring the necessity of adopting flexible or adaptive t* values at the whole-body level.
METHODS: Data from 53 patients who underwent one-hour dynamic 18 F-FDG PET/CT scans were retrospectively analyzed. Parametric maps of the net influx rate (Ki) and blood distribution volume (dv) were calculated for four t* values (10, 20, 30, and 45 min) using in-house software (PET KinetiX). Voxel-wise Ki and dv values were extracted from 10 predefined tissue structures through automated segmentation. Using t* = 30 min as the widely accepted reference, relative mean errors and relative absolute mean errors of Ki and dv estimated at t*shifts = 10, 20 and 45 min were calculated for each tissue. Pearson correlation coefficients between Ki or dv reference values and those estimated at t* shifts = 10, 20, and 45 min were also computed.
RESULTS: Compared to the reference t*30, Ki estimates ranged from - 21.4% (liver) to 7.3% (SAT) at t*10, and from - 13.8% (lungs) to 2.4% (brain) at t*20. Median absolute bias was 12.8% at t*10 (6.5% brain to > 25% liver) and 8.6% at t*20 (3.2% brain to > 15% lungs and liver). At t*45, Ki was consistently overestimated, with a median bias of 19.4% (2.7% brain to > 33% lungs and liver) and median absolute bias of 19.8% (5.5% brain to > 33% lungs and liver). For dv, biases ranged from - 25.2% (brain) to 8.6% (spleen) at t*10; - 13.7% (brain) to 5.7% (lungs) at t*20; - 15.5% (liver) to 8.8% (brain) at t*45. Median absolute biases were 14.0% at t*10 (9.8% heart to 25.2% brain), 9.4% at t*20 (7.7% heart to 14.1% brain), and 15% at t*45 (12.4% skeletal muscle to 18.5% brain). Regardless of t*, Ki values exhibited strong linear correlations (r > 0.7) across all organs, whereas dv correlations showed greater variability, falling below 0.7 in 80% of organs at t*45.
CONCLUSION: Kinetic parameter sensitivity to time-to-equilibrium (t*) varies across organs in Patlak whole-body parametric imaging, underscoring the necessity of adopting flexible or adaptive t* values at the whole-body level.