- Head and neck dedicated PET / CT had higher sensitivity (93.7%), specificity (76, 2%), negative predictive value (80%), accuracy (89.3%) butlowerpositive predictive value (23.8%), false negative rate (6.3%) thanwhoel body PET / CT (corresponding values were 90.9%; 66.7%; 50%; 88%; 33.3% and 9.1%, respectively).