A pinhole is used as the simplest objective with no lens and a single very small aperture.

(Scintillation Camera, Scintillation Gamma Camera, Gamma Scintillation Camera or Anger Gamma Camera) A gamma camera is an imaging device used in nuclear medicine to scan patients who have been injected, inhaled, or ingested with small amounts of radioactive materials emitting gamma rays. The gamma camera records the quantity and distribution of the radionuclide that is attracted to a specific organ or tissue of interest.
The first gamma camera was developed and introduced by Hal O. Anger in 1957/58. The structure hasn't changed by today. A gamma camera consists of:

Through this design the simultaneous registration of gamma ray photons is possible, the computer further allows dynamic imaging.

See also Pinhole, Elution, Center of Rotation, First Pass Scintigraphy, and Anger Hal Oscar.

In nuclear medicine a hot spot describes a strong activity enrichment in one or more ranges of the organ or body part which is examined.
A pinhole collimator may be used if images of a hot spot and the surrounding with very high resolution are necessary. Zoom magnification or a converging collimator also may be used to improve resolution and assign the hot spot.