Fast Monte Carlo based joint iterative reconstruction for simultaneous 99mTc/ 123I SPECT imaging

Area of Science:

• Nuclear Medicine
• Medical Imaging
• Radiochemistry

Background:

• Simultaneous 99mTc/123I SPECT enables dual physiological function assessment under identical conditions.
• Accurate separation of 99mTc and 123I is challenging due to close energy levels.
• Existing scatter correction methods inadequately model physical factors and patient-specific distributions.

Purpose of the Study:

• To develop and evaluate a novel Monte Carlo (MC) simulation-based joint ordered-subset expectation-maximization (JOSEM) algorithm (MC-JOSEM) for simultaneous 99mTc/123I SPECT.
• To simultaneously correct for scatter, cross talk, and detector response within the reconstruction algorithm.
• To assess the performance of MC-JOSEM for simultaneous brain perfusion (99mTc-HMPAO) and neurotransmission (123I-altropane) SPECT.

Main Methods:

• Developed MC-JOSEM, a fast MC simulation-based algorithm for multiple-radionuclide and multiple-energy JOSEM iterative reconstruction.
• Modeled photon transport, including scatter and detector response, using MC simulations of 99mTc and 123I.
• Compared MC-JOSEM with standard non-scatter-corrected OSEM (NSC-OSEM) and scatter-corrected OSEM (SC-OSEM) using simulated simultaneous dual-radionuclide brain SPECT data.

Main Results:

• MC-JOSEM significantly reduced bias and standard deviation in 99mTc and 123I activity estimates compared to NSC-OSEM and SC-OSEM.
• Relative bias for 99mTc activity estimates with MC-JOSEM ranged from -2.4% to 1.2%, compared to 7.2% to 103.6% for OSEM methods.
• MC-JOSEM improved 123I dopamine binding potential (BP) quantitation, achieving results 50.5% closer to the reference and a higher signal-to-noise ratio (SNR) (23.6 vs. 18.3).

Conclusions:

• MC-JOSEM demonstrates superior performance for quantitative tasks in simultaneous 99mTc/123I SPECT compared to conventional OSEM methods.
• The algorithm effectively corrects for scatter, cross talk, and detector response, enabling more accurate assessment of brain perfusion and neurotransmission.
• MC-JOSEM represents a significant advancement for dual-radionuclide SPECT imaging, improving diagnostic accuracy in neuroimaging applications.