A scintillation camera utilizing an NaI crystal of 38.7 em in diameter has been employed in examinations of 1200 patients for one year and nine months. The effective field of view is 34 cm in ...diameter, corresponding with approximate 70% larger areas than those of a standard scintillation camera with an NaI crystal of 30.5 cm in diameter. The performances of the large-area scintillation camera were examined regarding its linearity, resolution and uniformity by using Co-57 sources. The resolution tests with a lead bar phantom showed image discriminations of the bars of 0.64 cm wide at 5 and 10 em distant from the collimator. The uniformity was frequently checked by gamma-ray flood exposured on the detector surface, showing spontaneous shifts of uniformity with irregular intervals. The view of large-area scintillation camera covered bi-lateral lungs in three fourths of patients without an image distortion, which are shown with a diverging collimator. The large-area view was advantageous in a comparative study of regional respiratory functions of the bi-lateral lungs with Xe-133. The liver and spleen were also represented in one view of an A-P projection in most cases. The bi-lateral kidneys and the urinary bladder, however, came into one view only in one-fourth cases. The large-area scintillation camera was rather disadvantageous in the brain scintigrams, because they were not benefitted by the view much larger than the brain and the big detector was troublesome in fixing the head for the given projection.
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