Exponential dosing to standardize myocardial perfusion image quality with rubidium-82 PET

Background: ⁸²Rb PET is commonly performed using the same injected activity in all patients, resulting in lower image quality in larger patients. This study compared ⁸²Rb dosing with exponential vs proportional functions of body weight on the standardization of myocardial perfusion image (MPI) quality.

Methods: Two sequential cohorts of N = 60 patients were matched by patient weight. Rest and dipyridamole stress ⁸²Rb PET was performed using 0.1 MBq·kg^-2 exponential and 9 MBq·kg^-1 proportional dosing. MPI scans were compared qualitatively with visual image quality scoring (IQS) and quantitatively using the myocardium-to-blood contrast-to-noise ratio (CNR) and blood background signal-to-noise ratio (SNR) as a function of body weight.

Results: Average (min-max) patient body weight was 81 ± 18 kg (46-137 kg). Proportional dosing resulted in decreasing CNR, SNR, and visual IQS with increasing body weight (P < 0.05). Exponential dosing eliminated the weight-dependent decreases in these image quality metrics that were observed in the proportional dosing group.

Conclusion: ⁸²Rb PET dosing as an exponential (squared) function of body weight produced consistent stress perfusion image quality over a wide range of patient weights. Dramatically lower doses can be used in lighter patients, with the equivalent population dose shifted toward the heavier patients to standardize diagnostic image quality.