Minimisation of acquisition time in a TOF PET/CT scanner without compromising image quality

• Autor(a) principal: Oliveira, Joana
• Data de Publicação: 2017
• Outros Autores: Parafita, Rui, Branco, Susana
• Idioma: eng
• Título da fonte: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Texto Completo: http://hdl.handle.net/10400.21/7785
• topic: PET/CT; TOF; 68Ga; Acquisition time; Image quality

Introduction - Significant improvements have been made in Positron Emission Tomography/Computed Tomography (PET/CT) to enhance the image quality, namely, the development of time-of-flight (TOF) technology. This technique is useful to localize the emission point of the beta plus-emitter (β+) radiopharmaceutical inside the body, allowing better lesion contrast, especially for large patients, improving structural details and leading to a short scan time. The main goal of this study is to verify the shortest acquisition time per bed position, in a TOF PET scanner, without compromising the image quality, in both phantom and clinical imaging. Methods - For that purpose, images of a torso NEMA phantom were acquired with different acquisition times per bed position (30, 45, 60, 80 and 120 s) in a TOF PET/CT scanner (GEMINI TF 16, Philips), using Gallium-68 (68Ga) citrate. Clinical images were also acquired of an aleatory patient (male, 64 y) with 68Ga-prostate specific membrane antigen (68Ga-PSMA). Image quality parameters, such as signal-to-noise ratio (SNR), noise, contrast, contrast-to-noise ratio (CNR), contrast recovery coefficient (CRC) and quantification in terms of standardized uptake value (SUV) were acquired. Results - The increased contrast and CRC in larger spheres and with longer acquisition times produces an increase on the noise, leading to a decrease in SNR and CNR. In phantom imaging, SUVmax varied between 1.1 and 1.6 for background (normal uptake) and between 2.1 and 8.0 for spheres (abnormal uptake). A strong correlation was found for both SUVmax and SUVmean between the different acquisition times (R>0.7). Inpatient imaging, spleen showed higher SNR, contrast, noise, and CNR than liver. Median SUVmax was 7.1 for liver, 9.8 for spleen and 1.8 for bone. Conclusions - A time between 45 and 60 s per bed position is proposed for future clinical practices, allowing schedule more scans per day, contributing to an optimization of protocols without compromising the image quality.