Systems and methods for modeling are provided. The method can include acquiring scan data associated with a plurality of x-ray projections of an item. The method can further include determining at least one closed boundary curve associated with the item. For example, the method can determine a first maximum area based on the scan data and determine at least one edge of the first maximum area. The method can further generate a model of the item using the closed boundary curve and a first material specific parameter for a material within the closed boundary curve. The method can utilize the model to generate computed scan data, compare the computed scan data to the scan data, and determine a goodness of fit. The method can further adjust the model of the item by altering at least one of the closed boundary curve and the material specific parameter.