Evaluation of Spatial Resolution
Bar Phantom
Qualitative evaluation of the spatial resolution of an imaging device can be
made by visual inspection of the images obtained using bar phantoms. Bar
phantoms consist of four sets of parallel lead bar strips arranged perpen-
dicular to each other in four quadrants in a lucite holder (Fig. 10.3A). The
widths and spacings of the strips are the same within each quadrant but
differ in different quadrants. The Hine–Duley phantom consists of five
groups of lead strips of different thicknesses and spacings arranged in par-
allel fashion in a lucite holder (Fig. 10.3B). In all bar phantoms, the thick-
ness of lead should be sufficient to stop photons of a given energy for which
spatial resolution is being estimated.
The bar phantom is placed over the detector of a gamma camera. A^57 Co
flood source (described later under Quality Control) is placed on the top
of it and an image is taken. For evaluation of spatial resolution for differ-
122 10. Performance Parameters of Gamma Cameras
Fig. 10.2. Effect of source-to-collimator distance on overall system resolution for
various types of collimators. (A) High sensitivity parallel hole. (B) Diverging.
(C) All purpose parallel hole. (D) Converging. (E) High resolution parallel hole.
(F) Pinhole. (From Rollo FD, Harris CC. Factors affecting image formation. In:
Rollo FD, ed.Nuclear Medicine Physics. Instrumentation and Agents. St. Louis:
Mosby; 1977:407. Modified from Moyer RA. J Nucl Med 1974, 15:59.)