Simulations to Evaluate Accuracy and Patient Dose in Neutron-Stimulated, Emission-Computed Tomography (NSECT) for Diagnosis of Breast Cancer

Abstract

Abstract : We are developing a tomographic technique called Neutron Stimulated Emission Computed Tomography (NSECT) for early detection of breast cancer. NSECT is sensitive to metabolic changes in trace element concentrations that are seen in tumors at very early stages of development. Detecting and measuring these element concentrations has the potential to detect breast cancer very early. Using neutrons as the imaging radiation leads to significant concerns about patient dose due to their higher weighting factor. While preliminary experiments show that it is possible to perform NSECT scans with patient dose comparable to mammography, one of the key aspects of successful clinical translation is to deliver the minimum dose possible. This project aims at evaluating the effects of NSECT dose-reduction techniques on the accuracy of detecting breast cancer. Four dose-reduction techniques are under evaluation: reducing neutron flux; reducing spatial projections; reducing angular positions; and using multiple detectors. As separate evaluation of each factor using experimental studies is prohibitively time consuming, these evaluations are performed using Monte-Carlo simulations as a feasible alternative. In the first year of the study, we developed a Monte Carlo simulation of the NSECT tomographic scanning system in GEANT4 along with phantoms of benign and malignant breast tissue. The simulated system has now been used to generate simulated data from NSECT scans of the benign and malignant breast. The simulations have been tested and validated against experimentally acquired data from several different types of phantoms. Tomographic images are reconstructed using a maximum-likelihood algorithm, which has been used to generate diagnostic images of a single-element disease model based on iron distribution. These results demonstrate that NSECT has the ability to detect cancer-marking elements in the breast at reasonable levels of patient dose.