Fig. 6From: Analytic time-of-flight positron emission tomography reconstruction: two-dimensional caseThe two-dimensional convolution kernel is only a function of radial distance r. The blue curve is for the conventional ramp filter. The yellow and orange curves (on the top of each other) are for the σ = 0.5: one is computed with the true H and the other is computed square-root function approximationBack to article page