[Validation of Changes over Time in Sensitivity Calibrations of SPECT Quantification for Different Radionuclides]

Area of Science:

• Medical Imaging
• Nuclear Medicine
• Radiopharmacy

Background:

• Accurate quantitative analysis in single-photon emission computed tomography (SPECT) relies on the standardized uptake value (SUV).
• The SUV calculation necessitates a precise becquerel calibration factor (BCF) to convert measured counts per second (cps) to radioactivity in megabecquerels (MBq).
• Variations in BCF over time or with different radionuclides and collimators can impact SUV accuracy.

Purpose of the Study:

• To investigate the temporal stability and reproducibility of the BCF.
• To assess how different radionuclides and collimator types influence BCF measurements.
• To determine the reliability of BCF for quantitative SPECT imaging.

Main Methods:

• Monthly calculation of BCF (cps/MBq) using radioactivity measurements from syringe formulations and dispensed sources.
• Utilizing planar acquisition counts and dose calibrator readings for BCF determination.
• Calculating relative errors of BCF against the maximum value over a 44-month period.

Main Results:

• Average BCF values were determined for various radionuclide-collimator combinations (e.g., 46.0 for 123I-LPHR, 124.1 for 131I-MELP).
• Standard deviation of BCF remained low (<3.4) across all tested conditions, indicating minimal variation.
• Relative errors of BCF were generally below 10%, and often below 5% for specific combinations, demonstrating good stability.

Conclusions:

• The BCF, when measured using planar acquisition, demonstrates significant stability and reproducibility.
• These findings support the consistent use of BCF across a diverse range of radionuclides and collimators in SPECT imaging.
• The study validates the reliability of BCF measurements for accurate quantitative SPECT analysis over extended periods.