1. A method of imaging a patient using a positron emission tomography system, said method comprising: acquiring a plurality of frames of sinogram data wherein the sinogram data defines a line of response and a time-of-flight (TOF) measurement that localizes a positron annihilation within the patient; filtering the acquired sinogram data by numerically convolving a ramp filter in the frequency domain by a Fourier transform of a timing uncertainty profile using the TOF measurement; and back-projecting the filtered sinogram data to form an output image of the patient.