Quantification of image quality and partial volume effect along the axial field-of-view of uMI Panorama GS PET/CT...

The comprehensive knowledge of how the distinct physical decay characteristics of each radionuclide shape their image quality performance is essential for tailoring acquisition protocols and ensuring optimal clinical applications. Understanding the spatial dependence of the contrast recovery coefficient (CRC) is a prerequisite for robust quantitative image analyses and accurate clinical interpretations, since the partial volume effect (PVE) and the count rate vary along the axial field of view (AFOV). Image quality assessments with various radionuclides were performed on the uMI Panorama GS PET/CT system, with the CRC profile across its extended AFOV also evaluated.

Following the NEMA NU 2-2018 standard, the image quality was assessed using the NEMA IEC (NEC) Body Phantom with ¹⁸F, ⁶⁴Cu, ⁶⁸Ga, ⁸⁹Zr, ¹²⁴I, and ⁹⁰Y. The CRC, the background variability (BV), and the lung residual error were measured to quantify the image quality. CRCs were sequentially measured at four axial offsets: 1/2, 1/4, 1/8, and 1/16 of the AFOV. The impact of the radionuclide-specific PSF (point spread function) modeling on the CRC was evaluated by comparing PET images reconstructed with and without PSF modeling.

The assessment demonstrated comparable image qualities for ¹⁸F, ⁶⁴Cu, ⁶⁸Ga, ⁸⁹Zr, ¹²⁴I, while ⁹⁰Y showed a similar CRC but a higher BV and a higher lung residual error, attributable to its low positron branching ratio. The BV and lung residual error increased with increasing axial distance from the AFOV center, whereas CRCs for larger spheres remained stable across AFOV positions; small-sphere CRC measurements exhibited increased dispersion toward the periphery due to reduced count statistics. The PSF modeling significantly improved CRCs for ⁶⁸Ga and ¹²⁴I, consistent with their long positron ranges.

All investigated radionuclides were effectively imaged on the uMI Panorama GS PET/CT system. The AFOV uniformity was quantitatively evaluated based on CRC measurements obtained at multiple positions along the AFOV.