Which type of breast cancers is undetectable on ring-type dedicated breast PET?

To assess the factors causing tumor undetectability on ring-type dedicated breast positron emission tomography (DbPET). A total of 265 patients (288 tumors) underwent DbPET and contrast-enhanced magnetic resonance imaging (MRI) in a prone position. The distance between the shallowest part of the breast tumor and the front end of the pectoralis major muscle on MRI was considered as the tumor-to-chest wall distance. Twenty-four tumors (8.3%) were not visualized via DbPET. The tumor-to-chest wall distance for undetectable tumors was shorter than that of the detectable tumors (23.0 mm vs 38.5 mm, P