V/P SPECT images allow clear identification of segmentaland sub-segmental perfusion defects, as in Figure 2 from a woman with extensive PE.
Figure 3 shows a well-delineated segmental perfusion defect. Followup after three days showed an almost normal pattern, confirming the diagnosis of PE. Importantly, mismatch findings without a segmental character do not indicate PE. Such findings are often observed in patients with heart failure, mediastinal adenopathy,postradiation therapy, and so forth (click the image to enlarge).