Measuring myocardial blood flow with ⁸²rubidium using Gjedde-Patlak-Rutland graphical analysis

Area of Science:

• Nuclear cardiology
• Radiopharmaceutical imaging
• Quantitative myocardial perfusion imaging

Background:

• Myocardial blood flow (MBF) is crucial for assessing cardiac health.
• Current MBF measurement using ⁸²Rb involves complex non-linear modeling.
• Simpler, validated methods are needed for routine clinical use.

Purpose of the Study:

• To evaluate the feasibility of Gjedde-Patlak-Rutland (GPR) graphical analysis as a simplified method for MBF quantification.
• To compare GPR-derived MBF with established modeling techniques using ⁸²Rb PET.
• To assess the clinical applicability of GPR analysis for myocardial perfusion imaging.

Main Methods:

• Myocardial perfusion imaging was performed using ⁸²Rb PET with adenosine or regadenoson stress.
• Blood ⁸²Rb clearance into myocytes (K₁) was calculated using the modified Crone-Renkin equation.
• GPR analysis was applied to measure ⁸²Rb clearance into myocardium (Z) between 1-3 minutes post-injection.
• Myocardial extracellular fluid volume (ECV) was calculated as 1 - [Z/K₁].
• A modified Lortie equation was used to calculate MBF from Z (MBF_Z).

Main Results:

• Both adenosine and regadenoson equally increased MBF.
• Resting ECV was ~35 ml/100 ml, increasing to ~40 ml/100 ml post-stress.
• The ratio Z/K₁ averaged 0.62, leading to B_Z = 39 ml/min/100 ml.
• MBF_Z derived from GPR analysis correlated well with MBF from standard modeling (y = 0.43x + 22; r = 0.84).
• Stress/rest ratios also showed moderate correlation (r = 0.64).

Conclusions:

• GPR analysis is a promising, analytically simpler technique for measuring MBF with ⁸²Rb PET.
• The method yields MBF in units of ml/min/ml total tissue volume.
• Further development, including polar map display, is warranted for clinical implementation.