Influence of OSEM and segmented attenuation correction in the calculation of standardised uptake values for [18F]FDG PET

Abstract

Standardised Uptake Values (SUVs) are widely used in positron emission tomography (PET) as a semi-quantitative index of fluorine-18 labelled fluorodeoxyglucose uptake. The objective of this study was to investigate any bias introduced in the calculation of SUVs as a result of employing ordered subsets-expectation maximisation (OSEM) image reconstruction and segmented attenuation correction (SAC). Variable emission and transmission time durations were investigated. Both a phantom and a clinical evaluation of the bias were carried out. The software implemented in the GE Advance PET scanner was used. Phantom studies simulating tumour imaging conditions were performed. Since a variable count rate may influence the results obtained using OSEM, similar acquisitions were performed at total count rates of 34 kcps and 12 kcps. Clinical data consisted of 100 patient studies. Emission datasets of 5 and 15 min duration were combined with 15-, 3-, 2- and 1-min transmission datasets for the reconstruction of both phantom and patient studies. Two SUVs were estimated using the average (SUVavg) and the maximum (SUVmax) count density from regions of interest placed well inside structures of interest. The percentage bias of these SUVs compared with the values obtained using a reference image was calculated. The reference image was considered to be the one produced by filtered back-projection (FBP) image reconstruction with measured attenuation correction using the 15-min emission and transmission datasets for each phantom and patient study. A bias of 5%-20% was found for the SUVavg and SUVmax in the case of FBP with SAC using variable transmission times. In the case of OSEM with SAC, the bias increased to 10%-30%. An overall increase of 5%-10% was observed with the use of SUVmax. The 5-min emission dataset led to an increase in the bias of 25%-100%, with the larger increase recorded for the SUVmax. The results suggest that OSEM and SAC with 3 and 2 min transmission may be reliably used to reduce the overall data acquisition time without compromising the accuracy of SUVs.

Standards for PET Image Acquisition and Quantitative Data Analysis

“…However, it has been shown that SUV results are determined primarily by several factors, parameters, or settings that can and should be standardized (45). Table 1 provides an overview of factors affecting SUVs and their impact on SUVs, which have been extensively discussed in numerous articles (9,14,17,22,(25)(26)(27)(28)34,45,49,50). Following is a short review of some published recommendations for quantitative PET.…”

Reproducibility of 18F-FDG and 3′-Deoxy-3′-18F-Fluorothymidine PET Tumor Volume Measurements

“…To obtain this index of activity accumulation, a region of interest (ROI) should be determined, usually drawn manually or using some fixed threshold. Although an ROI is not the only factor that can affect the accuracy of SUVs, the type and size of an ROI are large contributors to the variability of such measurements, as has been previously demonstrated (2,3). A popular alternative is the use of the pixel with the maximum activity value, usually referred to as the maximum SUV (SUV max ).…”

Blind source separation for the computational analysis of dynamic oncological PET studies

“…BGO-vs. LSO-based tomographs, etc.) or data processing prior to image formation, such as attenuation and scatter corrections, efficiency normalization methods, etc., while some studies already indicated dependence on the image reconstruction method (31). Therefore, the utility of information provided by the SUVs largely depends on its integration with all available clinical and instrumental data (32), and ICA could be an alternative to the SUV-based evaluation for studies that require dynamic PET acquisitions.…”