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Are lesion features reproducible between 18F-FDG PET/CT images when acquired on analog or digital PET/CT scanners?



To compare lesion features extracted from 18F-FDG PET/CT images acquired on analog and digital scanners, on consecutive imaging data from the same subjects.


Whole-body 18F-FDG PET/CT images from 55 oncological patients were acquired twice after a single 18F-FDG injection, with a digital and an analog PET/CT scanner, alternately. Twenty-nine subjects were examined first on the digital, and 26 first on the analog equipment. Image reconstruction was performed using manufacturer standard clinical protocols and protocols that fulfilled EARL1 specifications. Twenty-five features based on lesion standardized uptake value (SUV) and geometry were assessed. To compare these features, intraclass correlation coefficient (ICC), relative difference (RD), absolute value of RD (|RD|), and repeatability coefficient (RC) were used.


In total, 323 18F-FDG avid lesions were identified. High agreement (ICC > 0.75) was obtained for most of the lesion features pulled out from both scanners’ imaging data, especially when reconstruction protocols fulfilled EARL1 specifications. For EARL1 reconstruction images, the features frequently used in clinics, SUVmax, SUVpeak, SUVmean, metabolic tumor volume, and total lesion glycolysis, reached an ICC of 0.92, 0.95, 0.87, 0.98, and 0.98, and a median RD (digital-analog) of 3%, 5%, 4%, − 3% and 1%, respectively. Using standard reconstruction protocols, the ICC were 0.84, 0.93, 0.80, 0.98, and 0.98, and the RD were 20%, 11%, 13%, − 7%, and 7%, respectively.


Under controlled acquisition and reconstruction parameters, most of the features studied can be used for research and clinical work. This is especially important for multicenter studies and patient follow-ups.

Key Points

Using manufacturer standard clinical reconstruction protocols, lesions SUV was significantly higher when using the digital scanner, especially the SUVmax that was approximately 20% higher.

High agreement was obtained for the majority of the lesion features when using reconstruction protocols that fulfilled EARL1 specifications.

Longitudinal patient studies can be performed interchangeably between digital and analog scanners when both fulfill EARL1 specifications.

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Fig. 1
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Fig. 4



Absolute value of RD


Full width at half maximum


Intraclass correlation coefficient


Metabolic tumor volume


Repeatability coefficient


Relative difference


Region of interest


Standardized uptake value


Total lesion glycolysis


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We are grateful to the patients who took part in the study. We would also like to thank Dr John Lee from the Communications Department at Champalimaud Centre for the Unknown, for his help in the English editing, and all staff from the Nuclear Medicine-Radiopharmacology department at Champalimaud Foundation.


The authors state that this work has not received any funding.

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Correspondence to Cláudia S. Constantino.

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The scientific guarantor of this publication is Durval C. Costa, MD, MSc, PhD, FRCR, head of Nuclear Medicine-Radiopharmacology department at Champalimaud Foundation, Lisbon, Portugal.

Conflict of interest

The authors of this manuscript declare no relationships with any companies, whose products or services may be related to the subject matter of the article.

Statistics and biometry

One of the authors has significant statistical expertise (Francisco P. M. Oliveira is an experienced statistician; he has a degree in Mathematics, a MSc in Computational Methods, and a PhD in Biomedical Engineering). No complex statistical methods were necessary for this paper.

Informed consent

Written informed consent was obtained from all subjects (patients) in this study.

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Institutional Review Board approval was obtained.


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• cross-sectional and observational study

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Constantino, C.S., Oliveira, F.P.M., Silva, M. et al. Are lesion features reproducible between 18F-FDG PET/CT images when acquired on analog or digital PET/CT scanners?. Eur Radiol 31, 3071–3079 (2021).

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  • 18F-FDG PET/CT
  • Computer-assisted image analysis
  • Image reconstruction
  • Diagnostic imaging
  • Reproducibility of results