Theory of scintigraphic imaging
Modulation transfer function

1. Scintigraphic imaging

Scintigraphy , or gammagraphy, is a physico-electronic method of imaging the distribution of radioactivity (radio indicator) in an object (in an organism) based on external detection of outgoing gamma radiation. From a physical and technical point of view, the methodology of scintigraphy is described in detail in Chapter 4 " Radioisotope scintigraphy " of the monograph " Nuclear physics and physics of ionizing radiation ". There are also defined and analyzed important physical parameters of scintillation cameras - positional resolution, homogeneity and linearity of the field of view, detection sensitivity, dead time, energy resolution. Here we focus in more detail on the analysis of positional resolution in scintigraphy.

For each imaging method, the most important parameter is the resolution , or ( spatial or positional ) resolution, which indicates what details in the subject we are able to distinguish by the imaging method. Spatial resolution is usually given in length units - millimeters.
For scintigraphic imaging, we can define positional resolution in two ways:

  1. The spatial resolution of a scintigraphic image is called the smallest distance [mm] of two point radioactive sources in the displayed object, which are still distinguishable from each other in the scintigraphic image as two images.

  2. By spatial resolution we mean the width of the profile in the image of a point or line source in the middle of the maximum height of the profile, recalculated to the spatial scale in the object [mm].

Definition II is more appropriate for the physical determination of resolution. using a line source, the image of which we can run independently multiple profiles, or add these profiles and thus achieve smaller statistical fluctuations. Spatial resolution is thus given as the half-width of the image profile of a point or line source; it is called FWHM (Full Width at Half Maximum).

4. Modulation transfer functions