Advances in nuclear medicine imaging, particularly positron emission tomography (PET/CT) and single-photon emission computed tomography (SPECT/CT), have played a crucial role in routine clinical practice, allowing the quantification of disease processes with high accuracy using intrinsic quantitative evaluation techniques (Bateman et al. 2016; Kusmirek et al. 2020). The contribution of nuclear medicine to noninvasive cardiothoracic imaging covers a wide range of indications. This chapter focuses on the quantitative aspects of nuclear medicine applied to routine diagnosis and clinical research, particularly in thoracic neoplasms, myocardial perfusion, and cardiac inflammation imaging.