The sponsor will provide [123I]mIBG as a single dose in a ready-to-use vial. All patients greater than or equal to 18 years of age and children with a weight of greater than or equal to 70 kg will receive an intravenous injection of 370 ±10% MBq (333 to 407 MBq [9.0 to 11 mCi]) of [123I]mIBG. Children <16 years of age (with a weight of 8-70 kg) will receive an activity of [123I]mIBG calculated on the basis of a reference activity for an adult scaled to body weight. Each investigator is responsible for obtaining the appropriate thyroid blockade agent and for its administration in accordance with national and local regulations and guidelines. Approximately 24 (± 6) hours following administration of [123I]mIBG all patients will return to the clinic for scintigraphic imaging. Imaging will be performed as per the standard procedures of the investigational site. This should include at a minimum total body planar scintigraphy. Single photon emission computed tomography (SPECT) may be performed following planar scintigraphy, as appropriate.