WHAT IT IS
The FOM is a performance index used to assess and compare the efficiency of liquid scintillation counters. It reflects the instrument’s capability to detect true radioactive events while minimizing the influence of background noise. A higher FOM signifies better instrument performance, especially for detecting low-activity or trace isotopes.
HOW IT WORKS
How Is FOM (E²/B) Calculated in LSC
Efficiency (E) – Represents the proportion of true decay events detected relative to the total decay events occurring in the sample, expressed as a percentage.
Background (B) – Refers to the count rate attributed to background radiation or noise unrelated to the sample's radioactivity, measured in counts per minute (CPM).
FOM Formula – FOM= E2/B. Squaring the efficiency emphasizes its importance in determining the instrument’s sensitivity.
IMPACT ON PERFORMANCE
Sensitivity Assessment: The FOM provides a reliable measure of the instrument’s ability to detect low-activity isotopes.
Instrument Comparison: Allows for objective comparison of performance between different LSC models or configurations.
Optimization: Guides the selection of operating parameters, such as quench correction and energy range, to maximize detection capability.
Quality Control: Serves as a benchmark for maintaining consistent performance during routine operation.
CHALLENGES AND LIMITATIONS
Background Interference: High background radiation levels can lower the FOM, requiring shielding and careful setup.
Quenching Effects: Chemical or optical quenching can reduce efficiency, impacting the FOM.
Aging Components: Detector degradation over time may reduce efficiency, necessitating regular maintenance or calibration.
Sample Variability: Complex matrices or heterogeneous samples can introduce variability in efficiency and background counts.
Environmental Sensitivity: Factors like temperature and humidity can influence background noise and detector performance.