Hybrid Modality Fusion of Planar Scintigrams and CT Topograms to Localize Sentinel Lymph Nodes in Breast Lymphoscintigraphy: Technical Description and Phantom Studies

Figure 2

Diagram of object magnification and minification for objects in different coronal planes relative to isocenter. Topograms differ from projection radiographs because the topogram is calibrated such that a “virtual” detector lies at a plane through the isocenter. The gray arrow represents a real object that is projected to isocenter during topogram reconstruction. This reconstruction technique causes objects that are physically closer to the X-ray source, relative to the gantry isocenter, to appear larger in the image, and vice versa when the object is physically closer than isocenter to the detectors (unlike projection radiographs, where objects closest to the detector are least affected by distortion).