Browsing by Author "Diale, Boitshoko Phenyo"

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    Influence of acquisition time and smoothing parameters on Ga-68 wholebody PET/CT image quality
    (Stellenbosch : Stellenbosch University, 2020-12) Diale, Boitshoko Phenyo; Moalosi, Tumelo C. G.; Mix, Michael; Ellmann, Annare; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Medical Imaging and Clinical Oncology. Nuclear Medicine.
    ENGLISH SUMMARY : PET/CT image optimization has been extensively investigated for 18F–FDG PET imaging. Although 68Ga–tracers are already widely used in PET, optimized imaging and reconstruction are still missing. The aim of this research was to optimize image quality for 68Ga scans under the constraint that the administered dose to a patient and acquisition time are limited. Materials and Methods : A Gemini TF Big Bore PET/CT system manufactured by Philips was used to acquire the images. The experimental data was formulated by retrospectively collecting data from patient scans, who had undergone wholebody (WB) PET/CT using 68Ga–DOTANOC for oncological imaging. The patient data sets were analyzed for this study to plan phantom measurements which simulated a typical activity distribution like in the patient scans. The NEMA (IEC) body phantom filled with low contrast and high contrast activity ratios was scanned on the Gemini TF Big Bore PET/CT scanner using the patient acquisition protocol. The data was reconstructed using a default WB reconstruction protocol with different smoothing parameters and varying scan acquisition times for low and high contrast data. Additionally a HN protocol with smaller voxel sizes was also used on high contrast data. The set images were analyzed using R Studio. Image quality parameters such as coefficient of variation (COV%), contrast to noise ratio (CNR), signal to noise ratio (SNR), recovery coefficient (RC%) and uniformity in terms of standardized uptake value (SUV) were acquired. Results: For low contrast COV%, CNR, SNR values varied as follows: 0.89 – 0.99%, 0.96 – 1.08, 0.99 – 1.05, respectively. Values for high contrast varied as follows: 1.03 – 1.16%, 0.84 – 0.91, 0.80 – 0.97. When comparing COV%, CNR and SNR, low contrast images appeared to be superior to high contrast images. The RC% was found to be consistent in both low contrast and high contrast irrespective of the smoothing parameter. Conclusion: The results obtained from the phantom study demonstrated the Philips Gemini TF Big Bore PET scanner’s stability of good uniformity when assessing maximum activity concentration among the different acquisitions, and ability of the scanner to detect or recover radioactivity in low and high contrast images for all reconstruction parameters. From the phantom study results, incorporating the smoothing reconstruction parameter ”smooth” on low contrast images, allowed the reduction of acquisition time to 180 seconds while maintaining acceptable image quality.