# Nuclear Science and Techniques

《核技术》(英文版) ISSN 1001-8042 CN 31-1559/TL     2019 Impact factor 1.556

Nuclear Science and Techniques ›› 2017, Vol. 28 ›› Issue (11): 167

• LOW ENERGY ACCELERATOR, RAY AND APPLICATIONS •

### Quantification of the impact of TOF and PSF on PET images using the noise-matching concept: clinical and phantom study

M. Shekari 1,2  P. Ghafarian 3,4  S. Ahangari 1,2  M. R. Ay 1,2

1. 1 Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, Tehran, Iran
2 Research Center for Molecular and Cellular Imaging, Tehran University of Medical Sciences, Tehran, Iran
3 Chronic Respiratory Diseases Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran
4 PET/CT and Cyclotron Center, Masih Daneshvari Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran
• Contact: P. Ghafarian E-mail:pardis.ghafarian@sbmu.ac.ir
• Supported by:

This work was supported by the Tehran University of Medical Sciences, Tehran, Iran (No. 24166), and the Masih Daneshvari Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.

M. Shekari, P. Ghafarian, S. Ahangari, M. R. Ay. Quantification of the impact of TOF and PSF on PET images using the noise-matching concept: clinical and phantom study.Nuclear Science and Techniques, 2017, 28(11): 167
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Abstract:

This study was to assess quantitatively the accuracy of 18F-FDG PET/CT images reconstructed by TOF + PSF and TOF only, considering the noise-matching concept to minimize probable bias in evaluating algorithm performance caused by noise. PET images of similar noise level were considered. Measurements were made on an in-house phantom with hot inserts of Φ10–37 mm, and oncological images of 14 patients were analyzed. The PET images were reconstructed using the OSEM, OSEM + TOF and OSEM + TOF + PSF algorithms. Optimal reconstruction parameters including iteration, subset, and FWHM of post-smoothing filter were chosen for both the phantom and patient data. In terms of quantitative accuracy, the recovery coefficient (RC) was calculated for the phantom PET images. The signal-to-noise ratio (SNR), lesion-to-background ratio (LBR), and SUVmax were evaluated from the phantom and clinical data. The smallest hot insert (Φ10 mm) with 2:1 activity concentration ratio could be detected in the PET image reconstructed using the TOF and TOF + PSF algorithms, but not the OSEM algorithm. The relative difference for SNR between the TOF + PSF and OSEM showed significantly higher values for smaller sizes, while SNR change was smaller for Φ22–37 mm inserts both 2:1 and 4:1 activity concentration ratio. In the clinical study, SNR gains were 1.6 ± 0.53 and 2.7 ± 0.74 for the TOF and TOF + PSF, while the relative difference of contrast was 17 ± 1.05 and 41.5 ± 1.85% for the TOF only and TOF + PSF, respectively. The impact of TOF + PSF is more significant than that of TOF reconstruction, in smaller inserts with low activity concentration ratio. In the clinical PET/CT images, the use of the TOF + PSF algorithm resulted in better SNR and contrast for lesions, and the highest SUVmax was also seen for images reconstructed with the TOF + PSF algorithm.