What limits spatial resolution in PET? Spatial resolution in PET is fundamentally limited by three physical factors: positron range, non-collinearity of annihilation photons, and detector size. Even with perfect reconstruction, these factors introduce unavoidable uncertainty in localising the annihilation event.…
What determines spatial resolution in PET? Spatial resolution in PET is determined by a combination of detector resolution, positron range, and non-collinearity of annihilation photons. Unlike SPECT, PET resolution is not limited by mechanical collimation but by fundamental physical processes…
What is time-of-flight (TOF) PET? Time-of-flight (TOF) PET is an advanced PET technique that improves image quality by using the small difference in arrival times of the two annihilation photons to better localise the annihilation event along the line of…
How does PET differ from SPECT? PET and SPECT are both tomographic nuclear medicine imaging techniques, but they differ fundamentally in how photons are detected and localised. SPECT detects single gamma photons emitted directly from the radionuclide and uses mechanical…
What is PET imaging? PET (Positron Emission Tomography) is a tomographic nuclear medicine imaging technique that detects pairs of gamma photons produced by positron annihilation and reconstructs their origin in three dimensions. PET imaging detects pairs of 511 keV photons…
What artefacts occur in SPECT imaging? SPECT artefacts are image distortions that arise from physical limitations, acquisition errors, or reconstruction inaccuracies. Common artefacts include attenuation artefacts, patient motion artefacts, centre-of-rotation errors, ring artefacts, and streak artefacts from limited angular sampling.…
What is centre-of-rotation (COR) and why is it important in SPECT? The centre of rotation (COR) in SPECT refers to the precise geometric axis around which the gamma camera rotates during image acquisition. Accurate alignment of this rotational axis with…
What is attenuation correction in SPECT? Attenuation correction in SPECT is the process of compensating for the reduction in detected photon counts caused by absorption and scatter within the patient’s body. Without correction, deeper structures appear artificially less active because…
What is iterative reconstruction in SPECT? Iterative reconstruction is a mathematical method used in SPECT to reconstruct tomographic images by repeatedly refining an estimated activity distribution until it best matches the measured projection data. Unlike filtered back projection, which applies…
What is filtered back projection in SPECT? Filtered back projection (FBP) is a mathematical reconstruction method used in SPECT to convert multiple projection images into cross-sectional slices. It works by “back projecting” each projection across the image space and applying…
