Quantitative assessment of linearity of scintillation cameras

A method is proposed for quantifying the intrinsic linearity of a scintillation camera for quality assurance purposes. The distance between adjacent holes in the image of a Smith Orthogonal Hole phantom is utilized to calculate the percentage of nonlinearity, phi. For a perfectly linear camera, phi = 0. If phi is not 0, distortion is present. As the linearity distortion increases, the absolute value of phi increases. If phi is positive, the distortion is referred to as pincushion distortion. If phi is negative, barrel distortion is present. Results of this measurement in five cameras show that phi may be useful as a numerical index of linearity distortion.