List-mode image reconstruction for real-time PET imaging

Real-Time 3D PET Image with Pseudoinverse Reconstruction

“…Pseudoinverse axial rebinning was much faster than FORE, with just a moderately worse performance in terms of noise/resolution. As has been noted in previous works [3], there is a 2D-PINV matrix that would be fully equivalent to FBP. However, in the construction of the 2D-PINV, it is also possible to add geometrical information and physics effects, which introduce blurring to the TORs.…”

“…The workflow of the reconstruction process is represented schematically in Figure 3. As it has been shown in previous works [3], the pseudoinverse of the SRM can be used for list-mode data reconstruction. In a 3D problem, each column of the PINV of the SRM, A † (:, i), contains the region of the image that would produce a coincidence in the given LOR i.…”

“…In many applications of PET such as first-shot tests for chemicals [1] or PET image-guided surgery or biopsy [2], it is crucial to obtain images as quickly as possible. The frame rate achievable will depend on the sensitivity of the acquisition system, the hardware used for data acquisition, and the software employed for data processing and image reconstruction [3]. State-of-the-art PET systems [4][5][6] can process up to 10 million coincidences per second, providing useful images in very short time frames.…”

“…Then, for each axial slice, coordinates (x, y) of the image are updated event by event using each row of the transaxial SRM pseudoinverse A † xy (xy, ρθ). Although this is fast and feasible for a 2D case as presented by Selivanov and Lecompte [3], it takes longer than reconstructing with the whole sinogram, except for when the number of coincidences is very small. In our case, reading the list-mode coincidences and histograming them in a sonogram is faster than event by event reconstruction, even for frames as small as 0.1 s for the preclinical SuperArgus PET-CT scanner introduced in Section 2.2.1.…”

“…On other hand, iterative reconstructions provide better results than analytical methods [9,18], thanks to the incorporation in the reconstruction process of the physics effects involved in the emission, transport, and detection of PET radiation [14] such as positron range [19], non-collinearity, depth-of-interaction (DOI) in the crystals [13], geometrical considerations of the scanner [18,20], etc. However, iterative methods with realistic SRM are slow, and therefore, their application to real-time fully 3D PET imaging is still challenging [3,7].One of the most common approaches to speeding-up the reconstruction process involves introducing axial rebinning of the data, followed by 2D reconstructions [7,21,22]. The simplest method for axial rebinning of PET data is single-slice rebinning (SSRB) [23], where the activity is assigned to the central axial coordinate z of both crystals z 1 , z 2 .…”