Method of measuring modulation transfer function using metal wire in computed tomography

The current scanning parameters for computed tomography (CT) such as multi-detector row CT are becoming more complicated, and there are many cases in which the selected parameters directly affect image quality. Therefore, to evaluate the effectiveness and validity of the selected parameter, quantitative image quality evaluations are indispensable. Among the items of evaluation, modulation transfer function (MTF) is one of the most important in evaluating the resolution property. Several guidelines for performance evaluation for CT have been reported since the era of early CT diffusion. In those guidelines, it is recommended that the resolution property needs to be measured by the wire method, in which a phantom designed to support a thin metal wire along an axis perpendicular to the slice plane is used. However, the academic papers describing the wire method are so old that the detailed methodology corresponding to currently available CT specifications cannot be conducted. However, the fundamental principles are still effective. In this study, we examined the calculation method, phantom design and allocation, wire material, and other factors suitable for current CT specifications, and derived some recommendations from them.