kollimator

Kollimator (collimator) is a device that narrows a beam of particles or waves to improve directionality and reduce stray radiation. By restricting the angles at which rays can reach a detector or a target, a kollimator enhances spatial resolution and contrast in imaging and helps limit dose outside the region of interest in therapeutic settings.

Most kollimators are made from dense metals such as lead or tungsten and consist of an array of channels or holes. The geometry—parallel, converging, or diverging channels, or a pinhole—defines the accepted range of incident directions. The design trades off sensitivity (how many rays pass) against resolution and scatter rejection.

In medical imaging, external kollimators are used with X-ray tubes and gamma cameras. Parallel-hole collimators provide uniform sensitivity over a field of view, while pinhole collimators offer higher resolution for small organs at the expense of sensitivity. Diverging and converging variants suit specific imaging geometries. In radiography and CT, beam-shaping collimators define the field size and reduce patient exposure. In nuclear medicine, practical choices depend on the need for whole-body imaging versus high-resolution regional studies.

In radiation therapy and interventional radiology, multi-leaf collimators (MLCs) and static collimators shape high-energy beams to conform to tumor outlines, sparing healthy tissue. Limitations include reduced photon flux and potential for increased acquisition time or dose to the patient if the field is narrowed excessively. Kollimators thus balance resolution, sensitivity, and safety across applications.