The term in vivo refers to measuring or imaging the distribution of a radiopharma­ceutical in a living organism. Such procedures have been known for a long time, but the most commonly used imaging device, the so-called gamma camera (see Section 12.4.1), was developed by Hal Anger in Berkeley in 1957. While the gamma camera detects single photons, the pair of photons emitted when a positron meets an electron (annihilation radiation, as discussed in Section 5.3.3) can also be imaged using a so-called PET (discussed further in Section 12.6).

12.1.3 Therapy with Unsealed Radioactive Preparations

If it is possible to deposit beta — or alpha-emitting radiopharmaceuticals into or close to the organ or tissue to be deactivated or destroyed, then this short-range radiation will affect only a few layers of cells, or, when evenly distributed in an organ, it will irradiate the targeted organ selectively. This procedure requires radiopharmaceuticals accumulating specifically in the target organ, and preferably nowhere else in the body.