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

Area of Science:

• Nuclear Medicine
• Radiopharmacology
• Medical Imaging Physics

Background:

• Myocardial perfusion imaging (MPI) using Rubidium-82 PET (⁸²Rb PET) often employs a fixed injected activity.
• This approach leads to suboptimal image quality, particularly in heavier patients, impacting diagnostic accuracy.
• Standardizing MPI quality across diverse patient weights is crucial for reliable cardiac assessments.

Purpose of the Study:

• To compare the efficacy of exponential versus proportional body weight-based dosing strategies for ⁸²Rb PET.
• To evaluate the impact of these dosing methods on myocardial perfusion image quality metrics.
• To determine an optimal dosing function for consistent diagnostic quality in ⁸²Rb PET.

Main Methods:

• Two patient cohorts (N=60 each) were matched by weight for sequential ⁸²Rb PET scans.
• Dosing protocols included an exponential function (0.1 MBq·kg^-2) and a proportional function (9 MBq·kg^-1).
• Image quality was assessed quantitatively (CNR, SNR) and qualitatively (visual IQS) in relation to patient body weight.

Main Results:

• Proportional dosing showed significant decreases in CNR, SNR, and visual IQS with increasing patient weight (P<0.05).
• Exponential dosing effectively eliminated these weight-dependent declines in image quality metrics.
• Patient weights ranged from 46-137 kg, with an average of 81±18 kg.

Conclusions:

• ⁸²Rb PET dosing using an exponential (squared) function of body weight ensures consistent stress perfusion image quality.
• This method allows for reduced doses in lighter patients and increased doses in heavier patients.
• Standardizing diagnostic image quality across a wide range of patient weights is achievable with exponential dosing.