Imaging ¹²³I with a scintillation camera. A study of detection performance and quality factor concepts

Image quality, resolution and sensitivity of a scintillation camera equipped with various collimators have been investigated using high purity ¹²³I. Pulse height distributions of ¹²³I from a thyroid phantom partly in air and partly immersed in water demonstrated the substantial septa penetration of the 440 and 529 keV gamma rays of ¹²³I with high resolution collimators. Line spread functions were recorded and the modulation transfer function was evaluated from them. The two concepts of 'figure of merit' also used were Q_B=S_a mod MTF mod ², where S_a is the plane sensitivity and Q_C=S²/(S+2B), where S is the true signal from the object and B is the total background or noise due to septa penetration and scatter.