Influence of reconstruction parameters of positron emission tomograph scanning on the effect of partial volume of the pathological lesion

In this work, the following tasks were solved: to perform a comparative analysis of data processing methods when calculating recovery factors; to evaluate the influence of time-of-flight technology and PSF function on the recovery factor and the forecast of recovery factor deviation for potential pathological foci with a diameter of 6–8 mm; to evaluate the influence of parameters of iterative reconstruction algorithms, Gaussian filter and axial filters on the recovery factor. The calculation of the recovery factors was carried out on the basis of quantitative characteristics obtained in the analysis of reconstructions of images of the IEC phantom with six spheres installed inside and filled with a radiopharmaceutical. Eight series of experiments with background / sphere activity ratios 1/3, 1/4, 1/6, 1/8, 1/12, 1/14, 1/16, 1/20 were carried out with the same concentration of activity in the spheres during each separate experiment. The forecast of the effect of the partial volume effect on lesions with a diameter of 6 to 8 mm was carried out, taking into account the used reconstruction algorithms. It is advisable to use the results obtained to harmonize diagnostic protocols for scanning with positron emission tomographs using the input parameters of reconstruction algorithms and filters, which will minimize the error in the quantitative assessment of a radiopharmaceutical when analyzing the dynamics of the development of a pathological process, as well as the response of pathology to therapy.

Influence of detectors efficiency normalization on small animal PET image quality

LabPET GE 4 (a small animal positron emission tomograph) image acquisition is done by 1536 independents channels. Differences in the rate counting of each channel must be corrected so as not compromise image quality. Equipment user manual recommends that normalization of the detectors efficiency be made as often as possible and always whenever there are hardware or software parameters changes - included, but not limited to channels parameters adjustments, electronic cards replacements, channels activation or inactivation or software update. This work evaluates the normalization effects on the image quality parameters. PET image acquisition were performed using recommended parameters by the NEMA NU 4-2008 standards. Image was reconstructed in different ways using different normalization files. The tests performed indicated that the image quality parameters do not vary significantly with different normalization data. Therefore, a daily routine of normalizations is not justified, suggesting a periodical frequency of one month or more for this procedure.

Study of the time reversal symmetry in the decay of ortho-Positronium atoms using the J-PET detector

The Jagiellonian Positron Emission Tomograph (J-PET) is a novel device based on organic scintillators being developed at Jagiellonian University in Kraków, Poland. J-PET is an axially symmetric and high acceptance scanner that can be used as a multi-purpose detector system. It is well suited to pursue tests of discrete symmetries in decays of positronium in addition to medical imaging. J-PET enables measurement of both momenta and polarization vectors of annihilation photons. The latter is a unique feature of the J-PET detector which allows study of the time reversal symmetry violation operator constructed solely from the annihilation photons momenta before and after scattering within the detector.

Studies of discrete symmetries in decays of positronium atoms

A positronium - a bound state of electron and positron - is an eigenstate of parity and charge conjugation operators which decays into photons. It is a unique laboratory to study discrete symmetries whose precision is limited, in principle, by the effects due to the weak interactions expected at the level of 10−14 and photon-photon interactions expected at the level of 10−9. The Jagiellonian Positron Emission Tomograph (J-PET) is a detector for medical imaging as well as for physics studies involving detection of electronpositron annihilation into photons. The physics case covers the areas of discrete symmetries studies and genuine multipartite entanglement. The J-PET detector has high angular and time resolution and allows for determination of spin of the positronium and the momenta and polarization vectors of annihilation quanta. In this article, we present the potential of the J-PET system for studies of discrete symmetries in decays of positronium atoms.