No abstract

No abstract

The Fan-beam Gamma Camera THE EDITOR, Sir, Conventiona'l gamma' ra'y imaging systems produce a two-dimensional ma'p of a tjhree-dimensional distribution of gamma emitting material. The map, represent'ing the activity distribution integrated over a certain depth, is obtained by either (i) a single collimated detector scanning in a raster pattern over the distribution (such as a rectilinear scanner) or (ii) a large area detector, with pinhole or multihole collimation, viewing the entire distribution (the Anger gamma camera). The collimator limits the angle of acceptance of the y-rays in two dimensions, locat'ing the direction from whence they originate and hence a meaningful map of the activity distribution is obtained.This letter introduces a device employing a slit collimator which limits the angle of acceptance of the y-rays in only one direction. Each point in the activity distribution is thus emitting into an appreciable solid angle and one feels intuitively that the sensitivity of such a device is inherently greater than conventional gamma cameras. This remains to be seen.

A comparison is made between the performance of three transverse axial single-photon emission tomographic machines, namely a rotating gamma-camera and two different scanning systems. Each system has been evaluation in terms of the spatial resolution, sensitivity and efficiency. The functional dependence of the volume sensitivity on the size of the emitting object has been derived using a theoretical model of the photon emission, attenuation and detection. The model is shown to predict this size dependence well and is consistent with the experimental observations.

No abstract