Quantitative Assessments of Tumor Activity in a General Oncologic PET/CT Population: Which Metric Minimizes Tracer Uptake Time Dependence?

Semra Ince, Richard Laforest, Malak Itani, Vikas Prasad, Paul Robert Derenoncourt, John P. Crandall, Saeed Ashrafinia, Anne M. Smith, Richard Wahl, Tyler J. Fraum

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

In oncologic PET, the SUV and standardized uptake ratio (SUR) of a viable tumor generally increase during the postinjection period. In contrast, the net influx rate (Ki), which is derived from dynamic PET data, should remain relatively constant. Uptake-time-corrected SUV (cSUV) and SUR (cSUR) have been proposed as uptake-time-independent, static alternatives to Ki. Our primary aim was to quantify the intrascan repeatability of Ki, SUV, cSUV, SUR, and cSUR among malignant lesions on PET/CT. An exploratory aim was to assess the ability of cSUR to estimate Ki. Methods: This prospective, single-center study enrolled adults undergoing standard-of-care oncologic PET/CT. SUV and Ki images were reconstructed from dynamic PET data obtained before (~35–50 min after injection) and after (~75–90 min after injection) standard-of-care imaging. Tumors were manually segmented. Quantitative metrics were extracted. cSUVs and cSURs were calculated for a 60-min postinjection reference uptake time. The magnitude of the intrascan test–retest percent change (test–retest j%Dj) was calculated. Coefficients of determination (R2) and intraclass correlation coefficients (ICC) were also computed. Differences between metrics were assessed via the Wilcoxon signed-rank test (a, 0.05). Results: This study enrolled 78 subjects; 41 subjects (mean age, 63.8 y; 24 men) with 116 lesions were analyzed. For both tracers, SUVmax and maximum SUR (SURmax) had large early-to-late increases (i.e., poor intrascan repeatability). Among [18F]FDG-avid lesions (n 5 93), there were no differences in intrascan repeatability (median test–retest j%Dj; ICC) between the maximum Ki (Ki,max) (13%; 0.97) and either the maximum cSUV (cSUVmax) (12%, P 5 0.90; 0.96) or the maximum cSUR (cSURmax) (13%, P 5 0.67; 0.94). For DOTATATE-avid lesions (n 5 23), there were no differences in intrascan repeatability between the Ki,max (11%; 0.98) and either the cSUVmax (13%, P 5 0.41; 0.98) or the cSURmax (11%, P 5 0.08; 0.94). The SUVmax, cSUVmax, SURmax, and cSURmax were all strongly correlated with the Ki,max for both [18F]FDG (R2, 0.81–0.92) and DOTATATE (R2, 0.88–0.96), but the cSURmax provided the best agreement with the Ki,max across early-to-late time points for [18F]FDG (ICC, 0.69–0.75) and DOTATATE (ICC, 0.90–0.91). Conclusion: Ki,max, cSUVmax, and cSURmax had low uptake time dependence compared with SUVmax and SURmax.

Original languageEnglish
Pages (from-to)1349-1356
Number of pages8
JournalJournal of Nuclear Medicine
Volume65
Issue number9
DOIs
StatePublished - Sep 1 2024

Keywords

  • corrected SUV
  • metabolic rate
  • Patlak slope
  • PET

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