Relationship Between Pharmacokinetic Parameters and Imaging Duration in Dynamic ¹¹C-Acetate Cardiac PET/CT

  Objective  To evaluate the effect of imaging time on the pharmacokinetic parameters calculation of dynamic ¹¹C-acetate cardiac positron emission tomography (PET) scan and to investigate the feasibility of shortening the imaging time in clinical practice.

  Methods  This study was a retrospective analysis and 46 subjects who underwent ¹¹C-acetate PET/CT cardiac imaging at Peking Union Medical College Hospital (from a clinical study assessing myocardial tissue and metabolic characteristics in men with alcohol consumption) were included. Each subject was injected with 740 MBq ¹¹C-acetate before a 40-minute PET/CT scan, and time-activity curve in the left ventricle was collected as input function. Pharmacokinetic parameters (K₁ and k₂) calculated from the 40-minute dynamic data (53 frames) was regarded as the reference standard. The number of included dynamic image frames was sequentially reduced from the last frame, and the corresponding pharmacokinetic parameters of ¹¹C-acetate were calculated. Correlation, consistent analysis of trends and the relative differences on pharmacokinetic parameters between shortened data and reference standard were evaluated. The shortest acceptable scan time was determined based on the criterion that the R² of linear regression models was higher than 0.9 in all myocardial segments.

  Results  The R² between ¹¹C-acetate pharmacokinetic parameters and the reference standard was higher than 0.9 in all myocardial segments at scan time ≥17 min (37 frames) for both K₁ and k₂. The regression coefficients of K₁ values calculated from the shortened data and the reference standard in myocardium were distributed in the range of 0.982-1.007, and the regression coefficients of k₂ values calculated from the shortened data and the reference standard were distributed in the range of 0.783-1.000. When the scan time was reduced to 17 min (37 frames), the K₁ and k₂ values of left anterior descending branch, right coronary artery and left circumflex branch perfusion regions were significantly different from the reference standard (all P < 0.05). Left anterior descending branch perfusion region had the highest relative difference (RD) [K₁: (3.93±1.98)%; k₂: (13.79±6.40)%], while right coronary perfusion region had the lowest RD [K₁: (2.84±1.89)%; k₂: (9.74±5.62)%].

  Conclusions  For the male population with alcohol consumption or are healthy, shortening the scan time to 17 min (37 frames) during dynamic ¹¹C-acetate PET/CT cardiac imaging can obtain tracer pharmacokinetic parameters consistent with the reference standard, which can provide references for optimizing clinical image acquisition time.