Validation of Tc and Lu quantification parameters for a Monte Carlo modelled gamma camera.

Area of Science:

• Nuclear Medicine
• Medical Imaging Physics
• Computational Modeling

Background:

• Monte Carlo (MC) simulations are crucial for modeling complex physical phenomena in nuclear medicine.
• Accurate quantification of radiotracer activity and absorbed dose in SPECT/CT imaging relies on validated MC models.
• Validation of MC simulations with experimental data from gamma cameras is essential for reliable clinical application.

Purpose of the Study:

• To validate the calibration factor (CF) and recovery coefficient (RC) from the SIMIND Monte Carlo code for a Siemens Symbia Intevo Excel SPECT-CT system.
• To ensure optimal SPECT quantification for Technetium-99m (Tc-99m) and Lutetium-177 (Lu-177) imaging.
• To establish the reliability of MC simulations for patient activity and organ dose assessment.

Main Methods:

• Phantom experiments were conducted using Tc-99m and Lu-177 in various geometries (Petri dish, capillary, cylinder, Jaszczack phantom).
• Spatial resolution, sensitivity, CF, and RC were measured using a gamma camera.
• Experimental results were compared with those obtained from SIMIND MC simulations under identical conditions.

Main Results:

• Good agreement was observed between simulated and experimental data for spatial resolution and CF.
• Measured planar spatial resolution for Tc-99m was 8.3 mm (SIMIND: 7.8±0.1 mm) and for Lu-177 was 11.8±0.6 mm (SIMIND: 12.4±0.4 mm).
• Calibration factors showed close correspondence, and recovery coefficients were determined for various volumes to correct partial volume effects.

Conclusions:

• The SIMIND Monte Carlo code is validated for simulating both planar and SPECT images acquired with the Siemens Symbia Intevo SPECT-CT system.
• The validated model supports accurate quantification of Tc-99m and Lu-177 for diverse nuclear medicine procedures.
• This facilitates improved patient dosimetry and treatment planning in clinical practice.