Optimization of acquisition and processing parameters in sentinel lymph node scintigraphy using SPECT/CT Monte Carlo simulation

Although single photon emission computed tomography/computed tomography (SPECT/CT) systems have been in use to enhance the detection of sentinel lymph nodes SLNs with lymphoscintigraphy, recently no study has focused on optimization of acquisition and processing parameters of SPECT/CT imaging of SLN detection in breast cancer examinations using simulations. The purpose of this study was to carry out SLN detectability optimization with a SPECT Monte Carlo simulation for the first time. SIMIND Monte Carlo simulation program was used to model The Symbia T6; Siemens, Erlangen, Germany SPECT/CT system that was equipped with LMEGP and LEHR collimators. In order to simulate SPECT imaging of a realistic patient with breast cancer, a voxel-based anthropomorphic phantom by ZUBAL torso phantom was constructed. Image reconstructions with or without attenuation and scatter corrections were performed with CASToR software. Quality of reconstructed images was evaluated according to SLN contrast with respect to background. Reconstruction with attenuation correction was found to be the optimum reconstruction method for both collimators. SPECT imaging with LMEGP collimator yielded competitive results over LEHR collimator in terms of SLN contrast. The results of the study are in agreement with the literature. The method presented in this study will enable optimization of acquisition and processing parameters of SLN SPECT imaging such as different gamma camera(s), collimator settings, patient dimensions, and reconstruction correction methods (attenuation, scatter) in breast cancer examinations realistically, accurately and at a lower cost than physical phantom or patient studies.