Speaker
Description
Limited-angle positron emission tomography (PET) is attracting increasing interest for a variety of applications, such as organ-specific PET, in-vivo verification in particle therapy, and cost-effective total-body PET (TB-PET). Various simulation studies have indicated that the artefacts that arise in limited-angle PET images due to missing lines-of-response (LOR) can be mitigated by means of time-of-flight (TOF) reconstruction, provided that the system coincidence resolving time (CRT) is about 200 ps FWHM. Here, we put this hypothesis to an experimental test for the first time. We investigate how the loss of angular information affects PET images of a Derenzo-like phantom, for various levels of angular coverage, by successively removing more and more detector modules from a full-ring monolithic-scintillator PET setup. This is done with the phantom placed isocentrically and at 20 cm radial offset. The detectors have a 1.7 mm full-width-at-half-maximum (FWHM) spatial resolution, a 212 ps FWHM CRT, and 4.7 mm FWHM depth-of-interaction (DOI) resolution. The images reconstructed from these experimental datasets are analyzed and several metrics quantifying the degree of image distortion are calculated, viz. the structural similarity index measure (SSIM), the normalized root mean square deviation (NRMSD), the signal-to-noise ratio (SNR), the eccentricity, and the peak-to-valley ratio (PVR) of the hot rods in the phantom. It is found that a partial ring with an angular coverage of two-thirds yields images that approach the quality of those of a full ring if both TOF and DOI are used in the reconstruction. However, complete removal of limited-angle artefacts is not yet achieved at a CRT of 200 ps FWHM. Moreover, the beneficial effect of DOI is found to be at least as important as that of TOF if the phantom is placed at 20 cm radial offset.
| Track | FTMI |
|---|---|
| Presentation type | Oral |