Abstract
1972
Objectives Investigate the benefit of TOF-PET for small lesion detectability with uMI510, which isproduced by Shanghai United Imaging Healthcare and has a superb temporal-spatial resolution. The uMI510 image quality with TOF was first evaluated by an acquisition of NEMA IEC body phantom for calculating the contrast recovery coefficient (CRC) and background variability. The clinical image quality was also characterized with TOF images ofclinical small lesions.
Methods Phantom study We use a standard NEMA body IEC phantom (NU2-2007) to describe the small lesion contrast recovery versus background noise in the phantom study.A CT scan with 120 KV, 180 mAs and 5-mm slice thickness was performed for attenuation correction followed by a PET emission scan with 11min. Patients study 54 patient studies were selected for this investigation with the standard imaging protocol. Patients included 26 males and 28 females (age range 17-87 years; mean±SD = 65.63±14.61). The injected doses per kilogram of patient weight were 0.37 MBq/kg.PET emission data were acquired with 3D-mode for 3 min/bed position.Total 116 small lesions were selected for analysis. The study was approved by the local Ethics Committee and written informed consent was obtained from all subjects prior to the study. In data processing, both TOF + point-spread functions (PSF) and non-ToF + PSF3D attenuation-weighted ordered-subset-expectation-maximization (3D AW-OSEM)were used withall necessary corrections, including normalization, scatter, random, attenuation and dead-time losses.
Results Phantom study The phantom results indicated that TOF provides better CRC over all the iterations while the background variability is very similar. Especially, a higher CRC with ToF information can be achieved even if fewer number of iteration was used. With ToF information, the CRC of the two hot small spheres are improved more significantly than that of the two larger hot spheres. Clinical study A preliminary visual evaluation of TOF and non-TOF PET/CT images was performed by an experienced nuclear medicine physician blinded to thereconstruction methods., TOF significantly increased the SUVmean, SNR and contrast of all the lesions (p<0.01). The combination of TOF, PSF and 3D AW-OSEM can improve the SUVmean by 12.06±4.12%, SNR by 18.53±13.32% and contrast by 12.88±2.59%. The same analysis was also performed for the lesions in the thorax and abdomen.
Conclusions In this work, the TOF benefit was demonstrated through phantom and patient studies with uMI-510. With TOF information, small lesions were imaged with higher CRC, SUV, SNR, contrast and contrast gain,compared with non-TOF at the same iteration. We believe that TOF leads to a similar CRC versus noise trade-off with non-TOF, while fewer number of iteration was adopted.
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