. 2021 Jun 1;9(4):283–297. doi: 10.1007/s40336-021-00435-y

Table 2.

Summary table on [¹⁸F]FDG PET/CT imaging in musculoskeletal infections/inflammations

Disease	Clinical indication	Patient preparation	Imaging protocol	Interpretation criteria	Pitfalls	Final report
Spinal Infections	Diagnosis of suspected primary or secondary spinal infections; Suspected recurrence; Evaluation of extent and complications; Evaluation of antibiotic efficacy	According to Joint EANM/ ESNR and ESCMID-endorsed consensus document	Whole body acquisitions (50–60’ after i.v. injection of 2.5–3 MBq/Kg of [¹⁸F]FDG)	Qualitative analysis (1) Location Vertebral body (2) Pattern Smooth and homogeneous uptake: no infection (3) Intensity of uptake Score 0 (no uptake): no infection; Score I (slightly increased uptake in the inter- or paravertebral region): no infection; Score II (clearly increased uptake with a linear or disciform pattern in the intervertebral space): discitis; Score III (Score II + involvement of ground or cover plate or both plates of the adjacent vertebrae): spondylodiscitis; Score IV (Score III + surrounding STs abscess): spondylodiscitis Semi-qualitative analysis ΔSUV_max between 25 and 43% could be useful for the assessment of therapy response	FP findings in Inflammatory or degenerative disc diseases; Bone tumours or metastases; Recent vertebral fractures; Post-surgical inflammation; FN findings in Low-virulence bacterial infections; Previous antimicrobial treatment; Epidural abscesses; Extensive arthrodesis	Presence/absence of lesions; Pattern of uptake; Location; Extent; Intensity of uptake; Comparison with previous [¹⁸F]FDG PET/CT if performed; Time between injection and image acquisition (in order to better compare SUV_max of basal and FU studies)
Diabetic foot infections	Detection of infection (mainly in forefoot) and evaluation of its extent; DD between osteomyelitis, soft tissue infections and Charcot; Therapy monitoring and follow-up	According to EANM/SNMMI procedural guidelines	Whole body or, preferably, segmental acquisitions (60’ after i.v. injection of 2.5–5.0 MBq/Kg of [¹⁸F]FDG)	Qualitative analysis (1) Location in forefoot osteomyelitis, mandatory correlation of FDG uptake with CT abnormalities in bone in mid-hindfoot osteomyelitis, necessary correlation with WBC scan and colloid scan (2) Pattern: focal/diffuse uptake higher than contralateral clearly involving the bone: osteomyelitis; focal/diffuse uptake detectable only on STs: soft tissue infections; diffuse uptake involving mid-hindfoot and associated to disruption of bony architecture on CT: suggestive of Charcot Semi-qualitative analysis Limited value for SUV_max or T/B ratios	Pre-existing orthopaedic comorbidities (fractures/ arthrosis/arthritis…); Difficult to achieve and accurate DD between non infected Charcot and Charcot with super-imposed infection	Presence/absence of lesions; Pattern of uptake; Location; Extent; Intensity of uptake; Evaluation of CT component; Comparison to previous [¹⁸F]FDG PET/CT, if performed; Time between injection and image acquisition (in order to better compare SUV_max of basal and FU studies)
Osteomyelitis and prosthetic joint infections	Diagnosis of chronic osteomyelitis, destructive septic arthritis, prosthetic joint infections, infected fractures; Therapy monitoring	According to EANM/SNMMI procedural guidelines	Whole body or segmental acquisitions (60’ after i.v. injection of 2.5–5.0 MBq/Kg of [¹⁸F]FDG)	Qualitative analysis For prosthetic joint infections, the most important criterion seems to be the location of the uptake rather than the pattern or SUV_max Several interpretation criteria have been proposed but none has been universally accepted Peripheral bone osteomyelitis (1) Location Increased uptake higher than Contralateral clearly involving the bone: osteomyelitis (2) Pattern: Focal/linear/diffuse uptake: focal uptake clearly involving a bone segment: osteomyelitis; Semi-qualitative analysis Limited value for SUV_max or T/B ratios	Difficult to achieve and accurate DD between aseptic prosthetic loosening, infection, inflammation, degenerative changes and malignancy; Recent fractures and presence of metallic hardware may decrease the accuracy of [¹⁸F]FDG PET/CT	Presence/absence of uptake; Pattern of uptake; Location; Extent; Intensity of uptake; Evaluation of CT component; Comparison to previous [¹⁸F]FDG PET/CT, if performed; Time between injection and image acquisition (in order to better compare SUV_max of basal and FU studies)

Disease

Clinical indication

Patient preparation

Imaging protocol

Interpretation criteria

Pitfalls

Final report

Spinal Infections

Diagnosis of suspected primary or secondary spinal infections;

Suspected recurrence;

Evaluation of extent and complications;

Evaluation of antibiotic efficacy

According to Joint EANM/ ESNR and ESCMID-endorsed consensus document

Whole body acquisitions (50–60’ after i.v. injection of 2.5–3 MBq/Kg of [¹⁸F]FDG)

Qualitative analysis

(1) Location

Vertebral body

(2) Pattern

Smooth and homogeneous uptake: no infection

(3) Intensity of uptake

Score 0 (no uptake): no infection;

Score I (slightly increased uptake in the inter- or paravertebral region): no infection;

Score II (clearly increased uptake with a linear or disciform pattern in the intervertebral space): discitis;

Score III (Score II + involvement of ground or cover plate or both plates of the adjacent vertebrae): spondylodiscitis;

Score IV (Score III + surrounding STs abscess): spondylodiscitis

Semi-qualitative analysis

ΔSUV_max between 25 and 43% could be useful for the assessment of therapy response

FP findings in

Inflammatory or degenerative disc diseases;

Bone tumours or metastases;

Recent vertebral fractures;

Post-surgical inflammation;

FN findings in

Low-virulence bacterial infections;

Previous antimicrobial treatment;

Epidural abscesses;

Extensive arthrodesis

Presence/absence of lesions;

Pattern of uptake;

Location;

Extent;

Intensity of uptake;

Comparison with previous [¹⁸F]FDG PET/CT if performed;

Time between injection and image acquisition (in order to better compare SUV_max of basal and FU studies)

Diabetic foot infections

Detection of infection (mainly in forefoot) and evaluation of its extent;

DD between osteomyelitis, soft tissue infections and Charcot;

Therapy monitoring and follow-up

According to

EANM/SNMMI procedural guidelines

Whole body or, preferably, segmental acquisitions (60’ after i.v. injection of 2.5–5.0 MBq/Kg of [¹⁸F]FDG)

Qualitative analysis

(1) Location

in forefoot osteomyelitis, mandatory correlation of FDG uptake with CT abnormalities in bone

in mid-hindfoot osteomyelitis, necessary correlation with WBC scan and colloid scan

(2) Pattern:

focal/diffuse uptake higher than contralateral clearly involving the bone: osteomyelitis;

focal/diffuse uptake detectable only on STs: soft tissue infections;

diffuse uptake involving mid-hindfoot and associated to disruption of bony architecture on CT: suggestive of Charcot

Semi-qualitative analysis

Limited value for SUV_max or T/B ratios

Pre-existing orthopaedic comorbidities (fractures/ arthrosis/arthritis…);

Difficult to achieve and accurate DD between non infected Charcot and Charcot with super-imposed infection

Presence/absence of lesions;

Pattern of uptake;

Location;

Extent;

Intensity of uptake;

Evaluation of CT component;

Comparison to previous [¹⁸F]FDG PET/CT, if performed;

Time between injection and image acquisition (in order to better compare SUV_max of basal and FU studies)

Osteomyelitis and prosthetic joint infections

Diagnosis of chronic osteomyelitis, destructive septic arthritis, prosthetic joint infections, infected fractures;

Therapy monitoring

According to

EANM/SNMMI procedural guidelines

Whole body or segmental acquisitions (60’ after i.v. injection of 2.5–5.0 MBq/Kg of [¹⁸F]FDG)

Qualitative analysis

For prosthetic joint infections, the most important criterion seems to be the location of the uptake rather than the pattern or SUV_max

Several interpretation criteria have been proposed but none has been universally accepted

Peripheral bone osteomyelitis

(1) Location

Increased uptake higher than

Contralateral clearly involving the bone: osteomyelitis

(2) Pattern:

Focal/linear/diffuse uptake: focal uptake clearly involving a bone segment: osteomyelitis;

Semi-qualitative analysis

Limited value for SUV_max or T/B ratios

Difficult to achieve and accurate DD between aseptic prosthetic loosening, infection, inflammation, degenerative changes and malignancy;

Recent fractures and presence of metallic hardware may decrease the accuracy of [¹⁸F]FDG PET/CT

Presence/absence of uptake;

Pattern of uptake;

Location;

Extent;

Intensity of uptake;

Evaluation of CT component;

Comparison to previous [¹⁸F]FDG PET/CT, if performed;

Time between injection and image acquisition (in order to better compare SUV_max of basal and FU studies)

EANM European Association of Nuclear Medicine, ESNR European Society of Neuroradiology, ESCMID European Society of Clinical Microbiology and Infectious Disease, i.v. intra-venous, MBq Mega Bequerel, Kg Kilograms, [¹⁸F]FDG 18Fluorine fluorodeoxyglucose, p.i. post-injection, SUV_max standardized uptake value, T/B target/background, ΔSUV_max SUV_max before treatment- SUV_max after treatment, FP: false positive, FN false negative, FU follow-up, DD differential diagnosis, STs soft tissues, SNMMI Society of Nuclear Medicine and Molecular Imaging, CT computed tomography, PET/CT positron emission tomography/computed tomography, BPI bone/prosthesis interface