The use of detective quantum efficiency (DQE) in evaluating the performance of gamma camera systems

The imaging properties of an imaging system can be described by its detective quantum efficiency (DQE). Using the modulation transfer function calculated from measured line spread functions and the normalized noise power spectrum calculated from uniformity images, DQE was calculated with the number of photons emitted from a plane source as a measure for the incoming SNR2. Measurements were made with 99mTc, using three different pulse height windows at 2 cm and 12 cm depths in water with high resolution and all purpose collimators and with two different crystal thicknesses. The results indicated that at greater depths a 15% window is the best choice. The choice of collimator depends on the details in the organ being investigated. There is a break point at 0.5 cycles cm-1 and 1.2 cycles cm-1 at 12 cm and 2 cm depths, respectively. A difference was found in DQE between the two crystal thicknesses, with a slightly better result for the thick crystal for measurements at 12 cm depth. At 2 cm depth, the thinner crystal was slightly better for frequencies over 0.5 cm-1. The determination of DQE could be a method to optimize the parameters for different nuclear medicine investigations. The DQE could also be used in comparing different gamma camera systems with different collimators to obtain a figure of merit.