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Review
. 2021;9(4):299-339.
doi: 10.1007/s40336-021-00445-w. Epub 2021 Jul 10.

State of the art of 18F-FDG PET/CT application in inflammation and infection: a guide for image acquisition and interpretation

Massimiliano Casali #  1 , Chiara Lauri #  2 , Corinna Altini #  3 , Francesco Bertagna #  4 , Gianluca Cassarino #  5 , Angelina Cistaro #  6 , Anna Paola Erba #  7 , Cristina Ferrari #  3 , Ciro Gabriele Mainolfi #  8 , Andrea Palucci #  9 , Napoleone Prandini #  10 , Sergio Baldari  11 , Francesco Bartoli  7 , Mirco Bartolomei  12 , Adriana D'Antonio  8 , Francesco Dondi  4 , Patrizia Gandolfo  10 , Alessia Giordano  8 , Riccardo Laudicella  11 , Michela Massollo  6 , Alberto Nieri  12 , Arnoldo Piccardo  6 , Laura Vendramin  5 , Francesco Muratore  13 , Valentina Lavelli  3 , Domenico Albano #  4 , Luca Burroni #  9 , Alberto Cuocolo #  8 , Laura Evangelista #  5 , Elena Lazzeri #  7 , Natale Quartuccio #  14 , Brunella Rossi #  15 , Giuseppe Rubini #  3 , Martina Sollini #  16 , Annibale Versari #  1 , Alberto Signore #  2
Affiliations
Review

State of the art of 18F-FDG PET/CT application in inflammation and infection: a guide for image acquisition and interpretation

Massimiliano Casali et al. Clin Transl Imaging. 2021.

Abstract

Aim: The diagnosis, severity and extent of a sterile inflammation or a septic infection could be challenging since there is not one single test able to achieve an accurate diagnosis. The clinical use of 18F-fluorodeoxyglucose ([18F]FDG) positron emission tomography/computed tomography (PET/CT) imaging in the assessment of inflammation and infection is increasing worldwide. The purpose of this paper is to achieve an Italian consensus document on [18F]FDG PET/CT or PET/MRI in inflammatory and infectious diseases, such as osteomyelitis (OM), prosthetic joint infections (PJI), infective endocarditis (IE), prosthetic valve endocarditis (PVE), cardiac implantable electronic device infections (CIEDI), systemic and cardiac sarcoidosis (SS/CS), diabetic foot (DF), fungal infections (FI), tuberculosis (TBC), fever and inflammation of unknown origin (FUO/IUO), pediatric infections (PI), inflammatory bowel diseases (IBD), spine infections (SI), vascular graft infections (VGI), large vessel vasculitis (LVV), retroperitoneal fibrosis (RF) and COVID-19 infections.

Methods: In September 2020, the inflammatory and infectious diseases focus group (IIFG) of the Italian Association of Nuclear Medicine (AIMN) proposed to realize a procedural paper about the clinical applications of [18F]FDG PET/CT or PET/MRI in inflammatory and infectious diseases. The project was carried out thanks to the collaboration of 13 Italian nuclear medicine centers, with a consolidate experience in this field. With the endorsement of AIMN, IIFG contacted each center, and the pediatric diseases focus group (PDFC). IIFG provided for each team involved, a draft with essential information regarding the execution of [18F]FDG PET/CT or PET/MRI scan (i.e., indications, patient preparation, standard or specific acquisition modalities, interpretation criteria, reporting methods, pitfalls and artifacts), by limiting the literature research to the last 20 years. Moreover, some clinical cases were required from each center, to underline the teaching points. Time for the collection of each report was from October to December 2020.

Results: Overall, we summarized 291 scientific papers and guidelines published between 1998 and 2021. Papers were divided in several sub-topics and summarized in the following paragraphs: clinical indications, image interpretation criteria, future perspectivess and new trends (for each single disease), while patient preparation, image acquisition, possible pitfalls and reporting modalities were described afterwards. Moreover, a specific section was dedicated to pediatric and PET/MRI indications. A collection of images was described for each indication.

Conclusions: Currently, [18F]FDG PET/CT in oncology is globally accepted and standardized in main diagnostic algorithms for neoplasms. In recent years, the ever-closer collaboration among different European associations has tried to overcome the absence of a standardization also in the field of inflammation and infections. The collaboration of several nuclear medicine centers with a long experience in this field, as well as among different AIMN focus groups represents a further attempt in this direction. We hope that this document will be the basis for a "common nuclear physicians' language" throughout all the country.

Supplementary information: The online version contains supplementary material available at 10.1007/s40336-021-00445-w.

Keywords: FDG; Imaging; Infection; Inflammation; PET.

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Conflict of interest statement

Conflict of interestThe authors declare no conflict of interest.

Figures

Fig. 1
Fig. 1
Axial views of [18F]FDG PET/CT images (top) and low-dose CT scan (bottom) of a diabetic patient with suspected osteomyelitis of right foot. The scan identified a focal uptake on a cutaneous/subcutaneous ulcer of the soft tissues of plantar surface without bone involvement, thus ruling out the diagnosis of osteomyelitis
Fig. 2
Fig. 2
>50-year-old female with Giant Cell Arteritis (GCA). MIP (A, B) and axial PET/CT views before and after steroid treatment. Baseline (A, C): pathologic tracer uptake at ascending aorta, descending aorta, thoracic aorta, aortic arc, anonymous artery, subclavian arteries, common carotid arteries and abdominal aorta. Vascular tracer uptake greater than the hepatic one (grade 3 according to Meller reference scale). After treatment (B, D): no pathological uptake 3 months after steroid and immunosuppressive therapy (ongoing)
Fig. 3
Fig. 3
A male patient with a recent history of ischaemic stroke, with a suspicion for cardiac sarcoidosis. A MR showed a late enhancement in the septum, while B at PET images, a high and diffused FDG uptake was found in the anterior and lateral wall of the left ventricle. Moreover, in the lateral wall a focal FDG uptake was found. The pattern of focal-on-diffused uptake was compatible with active sarcoidosis
Fig. 4
Fig. 4
Initial evaluation of a > 30-year-old woman from Argentina with FUO and recent finding of pulmonary bilateral consolidations. 18F-FDG PET/CT shows moderate/high radiotracer uptake in solid/sub-solid consolidations localized in the upper areas of both lungs. Mild 18F-FDG uptake coexists in enlarged hilar and mediastinal lymph nodes. Histopathologic evaluation establishes the diagnosis of sarcoidosis
Fig. 5
Fig. 5
> 50-year-old woman with non-Hodgkin lymphoma, stage III, and secondary immunosuppression due to CHT and myelofibrosis. CT transaxial (A) and 18F-FDG PET/CT fused transaxial (B) imaging show mild pericardial and pleural effusion. The patient had fever without response to antibiotic therapy and pancytopenia. CT transaxial scan after contrast media injection (C) and 18F-FDG PET/CT fused transaxial (D) imaging after 6 months of corticosteroid therapy show persistent pericardial and pleural effusion and multiple pulmonary nodular lesions, later diagnosed as aspergillomas, which show intense 18F-FDG uptake. Typical Aspergillus lesion in left pulmonary hilar region, SUVmax 6.0
Fig. 6
Fig. 6
> 30-year-old man with HIV with fever and severe weight loss. CT transaxial (A) and 18F-FDG PET-TC fused transaxial (B) imaging show diffused and intense splenic 18F-FDG uptake (SUVmax 4.2), greater than liver. Further finding is a focal intense 18F-FDG uptake (SUVmax 9.0) localized at superior pole of the spleen, without consensual alterations at CT scan. These findings, along with mild diffused lymph nodal uptake (SUVmax 4.1), are suggestive for lymphomatous disease, but the patient was eventually diagnosed with disseminated histoplasmosis. CT transaxial (C) and 18F-FDG PET-TC fused transaxial (D) imaging after 1 month of follow-up show mild peritoneal effusion, persistent inhomogeneous and intense 18F-FDG splenic uptake, greater than liver, without focal hypermetabolic areas
Fig. 7
Fig. 7
Left panel: axial PET, CT and fused PET/CT (1a, 1b, 1c), sagittal PET, CT and fused PET/CT (2a, 2b, 2c) and coronal PET, CT and fused PET/CT (3a, 3b, 3c) images of a 18F-FDG PET/CT scan performed in a 59 year old male patient for oral carcinoma follow-up. Images revealed intense tracer uptake on diffused interstitial alterations with ground-glass appearance on both lungs; subsequent RT-PCR revealed COVID-19 positivity. Right panel: axial PET, CT and fused PET/CT (1a, 1b, 1c), sagittal PET, CT and fused PET/CT (2a, 2b, 2c) and coronal PET, CT and fused PET/CT (3a, 3b, 3c) images of a 18F-FDG PET/CT scan performed in the same patient for restaging of oral carcinoma purpose and after completion of COVID-19 specific therapy; images demonstrated complete disappearance of pathological uptake and resolution of interstitial alterations
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