In sinograms, what axis represents the activity across the detector?

In sinograms, the horizontal axis represents the angle of rotation or the projection angle, while the vertical axis indicates the detector's response or the activity along the detector. Each point on the vertical axis corresponds to a specific location on the detector, measuring the intensity or amount of detected radiation at that point. As the gamma rays emitted from a radiopharmaceutical in the patient's body interact with the detector, the results are plotted in a format that allows for visualization and reconstruction of the PET image.

The concept of the sinogram is crucial in the process of tomographic reconstruction because it compiles all the projection data from different angles, indicating how activity is distributed across the detector as it rotates around the scanned object. Understanding the arrangement of the axes in a sinogram is fundamental for interpreting PET data and subsequent image reconstruction processes.