Absolute quantification of regional tissue concentration of radioactivity in positron emission tomography (PET) is a critical parameter-of-interest across various clinical and research applications and is affected by a complex interplay of factors including scanner calibration, data corrections, and image reconstruction. The emergence of long axial field-of-view (FOV) PET systems widens the dynamic range accessible to PET and creates new opportunities in reducing scan time and radiation dose, delayed or low radioactivity imaging, as well as kinetic modeling of the entire human. However, these imaging regimes impose challenging conditions for accurate quantification due to constraints from image reconstruction, low count conditions, as well as large and rapidly changing radioactivity distribution across a large axial FOV. We comprehensively evaluated the quantitative accuracy of the uEXPLORER total-body scanner in conditions that encompass existing and potential imaging applications (such as dynamic imaging and ultralow-dose imaging) using a set of total-body specific phantom and human measurements. Through these evaluations we demonstrated a relative count rate accuracy of ±3%–4% using the NEMA NU 2-2018 protocol, an axial uniformity spread of ±3% across the central 90% axial FOV, and a 3% activity bias spread from 17 to 474 MBq 18F-FDG in a 210 cm long cylindrical phantom. Region-of-interest quantification spread of 1% was found by simultaneously scanning three NEMA NU 2 image quality phantoms, as well as relatively stable volume-of-interest quantification across 0.2%–100% of total counts through re-sampled datasets. In addition, an activity bias spread of −2% to +1% post-bolus injections in human subjects was found. Larger bias changes during the bolus injection phase in humans indicated the difficulty in providing accurate PET data corrections for complex activity distributions across a large dynamic range. Our results overall indicated that the quantitative performance achieved with the uEXPLORER scanner was uniform across the axial FOV and provided the accuracy necessary to support a wide range of imaging applications.
High-spin structure of 109 In has been investigated with the 100 Mo( 14 N, 5n) 109 In reaction at a beam energy of 78 MeV using the in-beam γ spectroscopic method. The level scheme of 109 In has been modified considerably and extended by 46 new γ-rays to the highest excited state at 8.979 MeV and J π =(45/2 + ). The new level scheme consists of eight bands, six of which are identified as dipole bands. The configurations have been tentatively assigned with the help of the systematics of neighboring odd-A indium isotopes and the experimental aligned angular momenta. The dipole bands are then compared with the titled axis cranking calculation in the framework of covariant density function theory (TAC-CDFT). The results of theoretical calculation based on the configurations, which involve one proton hole at the g 9/2 orbital and two or four unpaired neutrons at g 7/2 , d 5/2 and h 11/2 orbitals, show that the shape of 109 In undergoes an evolution on both β and γ deformations and possible chirality is suggested in 109 In. ever, chirality in the indium isotopes has not been reported. J Config 1 J core J J x ( ) 0.30 MeV 0.65 MeV J Config 2 J core J J x ( ) 0.20 MeV 0.70 MeV J Config 3 FIG. 9: (Color online) The proton, neutron and core angular momentum vectors (Jπ, Jν and Jcore ) for Config 1-3 in 109 In at both the minimum and the maximum rotational frequencies in the TAC-RMF calculations.
High-spin states in 126Te have been investigated by using in-beam γ ray spectroscopy with the 124Sn(7Li, 1p4n)126Te reaction at a beam energy of 48 MeV. The previously known level scheme has been enriched, and a new negative-parity sequence has been established. The yrast positive-parity band shows a shape change between triaxial shape and collective oblate shape as a function of spin. In particular, three competitive minima appear in the potential energy surface for the Iπ = 8+ states, with one aligned state at γ = −120° and two triaxial states at γ ∼ 30° and −45°, respectively. The signature splitting behavior of the negative-parity band is discussed. The shape change with increasing angular momentum and the signature splitting can be interpreted well in terms of the Cranked Nilsson-Strutinsky-Bogoliubov and Cranked Nilsson-Strutinsky model calculations.
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