Effect of scintillation camera nonuniformity on ejection fraction measurements

Area of Science:

• Nuclear medicine imaging
• Medical physics

Background:

• Scintillation cameras are vital for nuclear cardiology.
• Image uniformity is critical for accurate quantitative analysis, such as ejection fraction (EF) measurement.
• Deviations in uniformity can lead to diagnostic errors.

Purpose of the Study:

• To evaluate the impact of image uniformity errors on ejection fraction (EF) measurements.
• To assess the effectiveness of energy correction and count skim arithmetic in mitigating these errors.
• To determine the acceptable limits of differential uniformity for reliable EF quantification.

Main Methods:

• Utilized a rotating cardiac phantom with variable ejection fraction (EF) settings.
• Acquired data with a scintillation camera under conditions of normal and degraded uniformity (analyzer window offset, photomultiplier tube de-tuning).
• Applied no correction, energy correction, and combined energy and count skim correction to assess their impact on EF values.

Main Results:

• Ejection fraction (EF) values were significantly erroneous when differential uniformity exceeded 10% (National Electrical Manufacturers Association [NEMA] protocols).
• Energy correction alone, or combined with count skim correction, effectively restored EF values to acceptable ranges.
• Image degradation effects on EF were often apparent only after analog image quality was already compromised.

Conclusions:

• Differential uniformity exceeding 10% can cause substantial errors in ejection fraction (EF) measurements.
• Implementing energy correction, alone or with count skim correction, is essential for accurate EF quantification in the presence of uniformity issues.
• While uniformity correction methods improve numerical results, they must be applied cautiously, as analog image quality may degrade before EF errors become obvious.