Chair for Computer Aided Medical Procedures & Augmented Reality
Lehrstuhl für Informatikanwendungen in der Medizin & Augmented Reality

P. Matthies, M. Mesri, F. Pinto, J. Wuestemann, O. S. Grosser
Patient specific scatter reduction in SIRT gamma camera images
International Conference on Monte Carlo Techniques for Medical Applications, Naples, Italy, October 2017 (bib)

Selective internal radiation therapy (SIRT) is an interventional treatment modality for advanced liver malignancies. The hepatic tumors are treated via radioembolization using resin or glass microspheres containing the beta-emitting radionuclide yttirum-90 (90Y). The continuous spectrum of the produced Bremsstrahlung can be used for clinical imaging. However, the image quality suffers from low contrast due to difficulties in selecting the optimum collimator, energy window settings and scatter corrections. By applying Monte Carlo simulations, additional information about the intracorporal scattering can be obtained. Discrimination against scattered photons which lost their positional information can be used to improve image quality. The simulated ratio of primary (unscattered) to scattered photons can be used to margin the energy windows to energies, where the amount of primary photons exceeds the amount of scattered photons. Energy windows for 90Y Bremsstrahlung imaging shall be adjusted to include the highest amount of primary events compared to scattered events. However, a higher septal penetration occurs for photons of higher energies, therefore the collimator needs to be adjusted as well. Thicker septa will lead to a decreased ratio for higher energies, since more of these photons will be collimated. The lower sensitivity may result in longer acquisition times.
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