A method of estimating random events in positron emission tomography list mode data, including obtaining time-of-flight (TOF) list mode count data that includes TOF information converting the obtained TOF list mode count data into four-dimensional (4D) raw sinogram count data, without using the TOF information, wherein the 4D raw sinogram count data includes random count values interpolating the 4D raw sinogram count data to generate 4D interpolated sinogram count data low-pass filtering the 4D interpolated sinogram count data to remove noise converting the low-pass filtered 4D interpolated sinogram count data into filtered 4D raw sinogram count data and generating, by a processor, five-dimensional (5D) TOF raw sinogram count data from the filtered 4D raw sinogram count data by effectively applying a TOF mask filter to the filtered 4D raw sinogram count data.
