Comparison of PET/CT images acquired with PET NEMA phantom and SPECT tomographic phantom for quality control purposes

In this master's thesis, performance tests were conducted on a PET/CT system using the NEMA IEC Body phantom and the Jaszczak phantom to investigate their applicability for quality control. Image quality parameters such as contrast recovery, background variability, homogeneity, noise, and cold sphere contrast were evaluated. With the NEMA IEC Body phantom, contrast recovery was measured using hot spheres of different diameters (10, 13, 17, 22, 28, and 37 mm), and background variability was calculated through multiple ROI measurements according to NEMA NU-2 standards. This phantom provided reproducible and standardized quantitative results, making it suitable for PET/CT image quality assessment. The Jaszczak phantom was tested in order to examine its potential for PET/CT quality control. Homogeneity, noise, and cold sphere contrast were analyzed. However, the results demonstrated that the Jaszczak phantom, while widely used in SPECT imaging, does not offer reliable or reproducible measurements for PET/CT. In particular, its design is not optimized for the high sensitivity and quantitative accuracy required in PET, leading to limitations in evaluating contrast and noise performance. All acquisitions were carried out under clinical PET/CT protocols, and the findings were compared with relevant literature. The results confirmed that the NEMA IEC Body phantom is the appropriate standard for PET/CT quality control, while the Jaszczak phantom is unsuitable for this purpose. This study emphasizes the necessity of using NEMA-based phantoms for PET/CT quality assurance and demonstrates the limitations of applying SPECT-oriented phantoms such as the Jaszczak in PET imaging.