Non-diverging analytic expression for the on-axis sensitivity of converging collimators: experimental verification

Area of Science:

• Medical physics
• Nuclear medicine imaging
• Radiation detection

Background:

• Converging collimators are crucial components in nuclear medicine imaging.
• Accurate sensitivity calculations are essential for image quality and dose optimization.
• Existing formulas for collimator sensitivity have limitations, particularly near the focal locus.

Purpose of the Study:

• To derive and validate a new analytical formula for the sensitivity of converging collimators.
• To assess the accuracy of the new formula and its approximation compared to existing methods.
• To identify optimal use cases for the derived formulae based on theoretical predictions.

Main Methods:

• Derivation of an analytical formula for converging collimator sensitivity.
• Comparison of predictions from the new formula, a simplified version, and a common reference formula.
• Validation against Monte Carlo simulations and experimental data.

Main Results:

• Excellent agreement between all formulae and validation data far from the focal locus.
• Markedly superior agreement for the new formula and its approximation near the focal locus.
• The new formula demonstrates significant accuracy improvements in critical regions.

Conclusions:

• The new analytical formula provides highly accurate sensitivity predictions for converging collimators.
• The formula is particularly advantageous around the focal locus for collimators of any focal length.
• It is also recommended for use over a substantial field-of-view for short focal length collimators.