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Figure 6 A NOGA unipolar voltage (UV) map from a 69-year-old man with an inferior infarction six years ago and an anteroseptal infarction five years ago. The single-photon emission computed tomography (SPECT) images reveal an anteroseptal perfusion defect; the positron emission tomography (PET) polar map shows normal glucose uptake (blue) anteriorly but no glucose uptake (orange) apicoseptally. Viability assessment with the NOGA system (anteroseptal view at a slight craniocaudal angle on the UV map) provided the following information: the territory of the fixed perfusion defect is precisely depicted by voltage values <6 mV. The truly non-viable myocardium, as demonstrated by PET, is characterized by voltage values <4.5 mV; the green zone (4.5–6.0 mV) indicates viable myocardium that may benefit from revascularization.