Optimization of PET / CT oncology protocol with FDG-¹⁸F based on multiparameter analysis

The increasing availability of high performance equipment, reconstruction software and quantitative methods have provided new opportunities to improve image capturing and management of patients. Currently, new and effective strategies that reduce dose exposure, yet do not compromise diagnostics are underway and have become essential to protocol optimization. This study describes a method to achieve consistent clinical image quality in ¹⁸F-FDG scans accounting for patient habitus, dose regimen, image acquisition and processing techniques. Data was acquired from 58 adults, male and female, which were evaluated retrospectively. Images of the liver were acquired in list-mode during 360 s on a high-performance PET/CT scanner. The scans were reconstructed at incremental 30 s intervals and correlations between different patient-dependent parameters (PDP) and image and data quality were evaluated. Patient Noise Equivalent Count Rate (NECR) and coefficient of variation (CV) were used as metrics in our analysis. Based on the strongest PDP correlations, optimized acquisition protocols and dose regimens were identified for different reconstruction methods. Results: The strongest correlation of patient data quality was found between NECR per unit activity (NECRN) and body mass (BM): increasing BM causes NECRN to decrease exponentially (R² = 0.72). Patient body mass was also found to be the strongest PDP determinant of image quality (R² = 0.82 in OSEM3D and R² = 0.86 in PSF, p < 0.001). If a linear dose regimen is used, increasing ¹⁸F-FDG proportionally to BM, image quality degrades with increasing patient body mass when standard acquisition time is used. The adoption of different schemes for three body mass ranges (< 60 kg, 60–90 kg, > 90 kg) in clinical routine allows improved image quality with both PSF and OSEM3D reconstruction methods. In conclusion, this study has demonstrated a methodology for determining the time of image acquisition from FDGF18 activity administered in order to obtain high quality standard images. The proposed methodology may be used by PET/CT centers to develop protocols to standardize PET/CT imaging procedures, and achieve better patient management and cost-effective operations and at a reduced radiation dose. (author)