The diagnostic value of 18F-FDG-PET/CT and MRI in suspected vertebral osteomyelitis - a prospective study

Differentiation of Native Vertebral Osteomyelitis: A Comprehensive Review of Imaging Techniques and Future Applications

Native vertebral osteomyelitis, also termed spondylodiscitis, is an antibiotic-resistant disease that requires long-term treatment. Without proper treatment, NVO can lead to severe nerve damage or even death. Therefore, it is important to accurately diagnose the cause of NVO, especially in spontaneous cases. Infectious NVO is characterized by the involvement of 2 adjacent vertebrae and intervertebral discs, and common infectious agents include Staphylococcus aureus, Mycobacterium tuberculosis, Brucella abortus, and fungi. Clinical symptoms are generally nonspecific, and early diagnosis and appropriate treatment can prevent irreversible sequelae. Advances in pathologic histologic imaging have led physicians to look more forward to being able to differentiate between tuberculous and septic spinal discitis. Therefore, research in identifying and differentiating the imaging features of these 4 common NVOs is essential. Due to the diagnostic difficulties, clinical and radiologic diagnosis is the mainstay of provisional diagnosis. With the advent of the big data era and the emergence of convolutional neural network algorithms for deep learning, the application of artificial intelligence (AI) technology in orthopedic imaging diagnosis has gradually increased. AI can assist physicians in imaging review, effectively reduce the workload of physicians, and improve diagnostic accuracy. Therefore, it is necessary to present the latest clinical research on NVO and the outlook for future AI applications.

Value of 18 F-FDG PET/CT to Identify Occult Infection in Presumed Aseptic Pseudarthrosis after Spinal Fusion: Correlation with Intraoperative Cultures

Objective  Fluorine-18 fluorodeoxyglucose ( 18 F-FDG) positron emission tomography/computed tomography (PET/CT) has gained attention as an emerging tool in case of suspicion of infection on spine, whether native or instrumented. However, the diagnostic performance of 18 F-FDG PET/CT in clinically occult low-grade surgical site infection (SSI) after spinal fusion, an important risk factor for pseudarthrosis, remains unknown. Methods  We retrospectively identified all the presumed aseptic patients with pseudarthrosis confirmed by revision surgery who underwent preoperative 18 F-FDG PET/CT scans performed between April 2019 and November 2022. These patients were presumed aseptic because they did not have clinical signs or laboratory tests suggestive of SSI, preoperatively. The PET/CT images were analyzed in consensus by two nuclear medicine physicians blinded to the clinical, biological, and imaging information. Visual assessment of increased uptake around cage/intervertebral disk space (and/or hardware) higher than background recorded from the first normal adjacent vertebra was interpreted as positive. Image data were also quantitatively analyzed by the maximum standardized uptake value as an index of 18 F-FDG uptake, and the ratio between the uptake around cage/intervertebral disk space (and/or hardware) and background recorded from the first normal adjacent vertebra was calculated. The final diagnosis of infection was based on intraoperative cultures obtained during pseudarthrosis revision surgery. Results  Thirty-six presumed aseptic patients with surgically confirmed pseudarthrosis after spinal fusion underwent preoperative 18 F-FDG PET/CT scans. Cultures of samples from revisions found that 20 patients (56%) were infected. The most frequent isolated bacterium was Cutibacterium acnes ( C. acnes ) in 15 patients (75%), followed by coagulase-negative staphylococci (CNS) in 7 patients (33%). Two patients had co-infections involving both C. acnes and CNS. Of the 36 PET/CT studied in this study, 12 scans were true-negative, 10 true-positive, 10 false-negative, and 4 false-positive. This resulted in sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of 50%, 75%, 71%, 55%, and 61%, respectively. Conclusion  In presumed aseptic pseudarthrosis after spinal fusion, 18 F-FDG PET/CT offers good specificity (75%) but low sensitivity (50%) to identify occult SSI. The high prevalence (56%) of SSI, mostly caused by C. acnes (75%), found in our presumed aseptic cohort of patients supports the utility of systematic intraoperative cultures in revision cases for pseudarthrosis.

Application of Nuclear Medicine Techniques in Musculoskeletal Infection: Current Trends and Future Prospects

Nuclear medicine has become an indispensable discipline in the diagnosis and management of musculoskeletal infections. Radionuclide tests serve as a valuable diagnostic tool for patients suspected of having osteomyelitis, spondylodiscitis, or prosthetic joint infections. The choice of the most suitable imaging modality depends on various factors, including the affected area, potential extra osseous involvement, or the impact of previous bone/joint conditions. This review provides an update on the use of conventional radionuclide imaging tests and recent advancements in fusion imaging scans for the differential diagnosis of musculoskeletal infections. Furthermore, it examines the role of radionuclide scans in monitoring treatment responses and explores current trends in their application. We anticipate that this update will be of significant interest to internists, rheumatologists, radiologists, orthopedic surgeons, rehabilitation physicians, and other specialists involved in musculoskeletal pathology.

The routine clinical use of fluorodeoxyglucose PET/CT to confirm treatment response in pyogenic spine infection

OBJECTIVE

Response of pyogenic spine infection to antibiotic therapy is usually based on nonspecific symptoms and inflammation markers. Abnormalities on MRI persist too long to influence therapy. Is FDG-PET/CT a timely and robust predictor of successful therapy?

MATERIALS AND METHODS

Retrospective study. Sequential FDG-PET/CTs done to assess treatment response over a 4-year period. Recurrence of infection after stopping treatment was the endpoint.

RESULTS

One hundred seven patients enrolled. First treatment response scan showed no signs of infection in 69 patients (low risk). Twenty-four additional patients underwent additional treatment after an initial positive scan with low-risk pattern on follow-up imaging. After stopping antibiotics, none had clinical recurrence of infection. One had positive cultures at surgery for negative predictive value of 0.99. Thirty-eight patients had evidence of residual infection. Abnormalities in 28 were comparable to what is seen with untreated infection (high-risk). Twenty-seven received additional treatment until resolution. Antibiotics were stopped in 1 who suffered recurrence. Ten had low-grade/localized abnormalities consistent with infection (intermediate-risk). Signs of infection resolved in 3 after additional treatment. Of the remaining 7 patients who had minor residual abnormalities when antibiotics were stopped, 1 had recurrent infection for a positive predictive value of 0.14.

CONCLUSION

Risk stratification proposed: A low-risk scan with only inflammation at a destroyed joint indicates negligible risk of recurrence. Unexplained activity in bone, soft tissue or spinal canal indicates high risk with further antibiotics recommended. Most patients with subtle or localized findings (intermediate risk) did not experience recurrence. Stopping therapy could be considered under careful observation.

Active Lumbar Spondylodiscitis on [68Ga]Ga-PSMA-11 PET/CT Mimicking Bone Metastasis

We report a [68Ga]Ga-PSMA-11 positron emission tomography/computed tomography (PET/CT) scan of a 71-year-old man with metastatic castration-resistant prostate cancer (mCRPC) and concomitant active lumbar spondylodiscitis, both PSMA-positive on a PET/CT scan. This interesting image should advise colleagues to consider spondylodiscitis as a differential diagnosis of PSMA-positive findings in the spine, particularly if intervertebral space and soft tissue are involved.

What Role Does PET/MRI Play in Musculoskeletal Disorders?

Musculoskeletal disorders of nononcological origin are one of the most frequent reasons for consultation. Patients suffering from musculoskeletal disorders also consult more than once for the same reason. This results in multiple clinical follow-ups after several radiological and serum examinations, the main ones including X-rays targeting the painful anatomical region and inflammatory serum parameters. As part of their work up, patients suffering from musculoskeletal disorders often require multisequence, multi-parameter MRI. PET/MRI is a promising imaging modality for their diagnosis, with the added advantage of being able to be performed in a single visit. PET/MRI is particularly useful for diagnosing osteomyelitis, spondylodiscitis, arthritis, many pediatric pathologies, and a wide range of other musculoskeletal pathologies. PET/MRI is already used to diagnose malignant bone tumors such as osteosarcoma. However, current knowledge of the indications for PET/MRI in nononcological musculoskeletal disorders is based on studies involving only a few patients. This review focuses on the usefulness of PET/MRI for diagnosing nononcological musculoskeletal disorders.

Contemporary Management of Staphylococcus aureus Bacteremia-Controversies in Clinical Practice

Staphylococcus aureus bacteremia (SAB) carries a high risk for excess morbidity and mortality. Despite its prevalence, significant practice variation continues to permeate clinical management of this syndrome. Since the publication of the 2011 Infectious Diseases Society of America (IDSA) guidelines on management of methicillin-resistant Staphylococcus aureus infections, the field of SAB has evolved with the emergence of newer diagnostic strategies and therapeutic options. In this review, we seek to provide a comprehensive overview of the evaluation and management of SAB, with special focus on areas where the highest level of evidence is lacking to inform best practices.

Vertebral osteomyelitis secondary to infective endocarditis detected by repeated magnetic resonance imaging: a case report

Background

Patients with infective endocarditis (IE) experience various symptoms, a major one being back pain, which is occasionally caused by concomitant vertebral osteomyelitis (VO). Magnetic resonance imaging (MRI) is generally used to detect VO; however, the sensitivity of detection using MRI is very low in the early stages of VO.

Case summary

A 60-year-old man visited our hospital with complaints of fever and persistent back pain over the past 7 days. A holosystolic heart murmur was auscultated, and an echocardiography revealed a vegetation on the posterior mitral leaflet. Blood cultures were positive for Streptococcus sanguinis. He was diagnosed with IE and treated with antimicrobials. A lumbar spine MRI on Day 1 showed no clear signs of vertebral infection, but the back pain continued and gradually worsened. Magnetic resonance imaging retest on Day 8 showed high signal intensity within the lumbar vertebral bodies and the disk on T2-weighted sequences, indicating VO. Intravenous antimicrobial therapy was extended, followed by oral antimicrobials, and a corset was put on to protect the lumbar spine to prevent bone degradation.

Discussion

For persistent back pain in IE patients, repeat MRIs at regular intervals of time can detect possible vertebral infection even if signs of vertebral infection were absent on the initial MRI.

Evaluating the use of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography in the workup of Staphylococcus aureus bacteraemia: a cost-utility analysis

OBJECTIVES

The use of positron emission tomography/computed tomography (PET/CT) in the evaluation of patients with Staphylococcus aureus bacteraemia can improve the diagnosis of infectious foci and guide clinical management. We aimed to evaluate the cost-utility of PET/CT among adults hospitalized with Staphylococcus aureus bacteraemia.

METHODS

A cost-utility analysis was conducted from the healthcare payer perspective using a probabilistic Markov cohort model assessing three diagnostic strategies: (a) PET/CT in all patients, (b) PET/CT in high-risk patients only, and (c) routine diagnostic workup. Primary outcomes were quality-adjusted life years (QALYs), costs in Canadian dollars, and an incremental cost-effectiveness ratio. Deterministic and probabilistic sensitivity analyses were conducted to evaluate parameter uncertainty.

RESULTS

Routine workup resulted in an average of 16.64 QALYs from the time of diagnosis at a lifetime cost of $209 060/patient. This was dominated by PET/CT in high-risk patients (i.e. greater effectiveness at lower costs) with average 16.88 QALYs at a cost of $199 552. Compared with PET/CT in high-risk patients only, PET/CT for all patients cost on average $11 960 more but resulted in 0.14 more QALYs, giving an incremental cost-effectiveness ratio of $83 500 (cost per additional QALY gained); however, there was a high degree of uncertainty comparing these two strategies. At a willingness-to-pay threshold of $50 000/QALY, PET/CT in high-risk patients was the most cost-effective strategy in 58.6% of simulations vs. 37.9% for PET/CT in all patients.

DISCUSSION

Our findings suggest that a strategy of using PET/CT in high-risk patients is more cost-effective than no PET/CT. Randomized controlled trials should be conducted to evaluate the use of PET/CT in different patient groups.

Debridement-Reconstruction-Docking Management System Versus Ilizarov Technique for Lower-Extremity Osteomyelitis

BACKGROUND

Osteomyelitis causes marked disability and is one of the most challenging diseases for orthopaedists to treat because of the considerable rate of infection recurrence. In this study, we proposed and assessed the debridement-reconstruction-docking (DRD) system for the treatment of lower-extremity osteomyelitis. This procedure comprises 3 surgical stages and 2 preoperative assessments; namely, pre-debridement assessment, debridement, pre-reconstruction assessment, reconstruction, and docking-site management. We evaluated the use of the DRD system compared with the Ilizarov technique, which is defined as a 1-stage debridement, osteotomy, and bone transport.

METHODS

This retrospective cohort included 289 patients who underwent either DRD or the Ilizarov technique for the treatment of lower-extremity osteomyelitis at a single institution between January 2013 and February 2021 and who met the eligibility criteria. The primary outcome was the rate of infection recurrence. Secondary outcomes included the external fixator index (EFI), refracture rate, and the Paley classification for osseous and functional results. An inverse-probability-weighted regression adjustment model was utilized to estimate the effect of the DRD system and Ilizarov technique on the treatment of lower-extremity osteomyelitis.

RESULTS

A total of 131 and 158 patients underwent DRD or the Ilizarov technique, respectively. The inverse-probability-weighted regression adjustment model suggested that DRD was associated with a significant reduction in infection recurrence (risk ratio [RR], 0.26; 95% confidence interval [CI], 0.13 to 0.50; p < 0.001) and EFI (-6.9 days/cm, 95% CI; -8.3 to -5.5; p < 0.001). Patients in the DRD group had better Paley functional results than those in the Ilizarov group (ridit score, 0.55 versus 0.45; p < 0.001). There was no significant difference between the 2 groups in the rate of refracture (RR, 0.87; 95% CI, 0.42 to 1.79; p = 0.71) and Paley osseous results (ridit score, 0.51 versus 0.49; p = 0.39).

CONCLUSIONS

In this balanced retrospective cohort of patients with lower-extremity osteomyelitis, the use of the DRD system was associated with a reduced rate of infection recurrence, a lower EFI, and better Paley functional results compared with the use of the Ilizarov technique.

LEVEL OF EVIDENCE

Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Value of [18F]FDG PET/CT in Diagnosis and Management of Spondylodiscitis

Vertebral osteomyelitis is the third most common form of osteomyelitis in patients over 50 years of age.Whereas prompt (pathogen-directed) therapy is crucially associated with better outcomes, the heterogeneous clinical presentation of disease with unspecific symptoms often delays adequate treatment initiation. Diagnosis requires a careful investigation of medical history, clinical findings and diagnostic imaging, including magnetic resonance imaging and nuclear medicine techniques.Due to its high sensitivity, [18F]FDG PET/CT is becoming increasingly important in diagnosis and management of spondylodiscitis, especially in the postoperative setting with presence of spinal hardware or other implantable devices in which MRI is limited.

Risk Factors for the In-Hospital Mortality in Pyogenic Vertebral Osteomyelitis: A Cross-Sectional Study on 9753 Patients

BACKGROUND

Pyogenic vertebral osteomyelitis represents a clinical challenge associated with significant morbidity and mortality. The aim of this study was to analyze potential risk factors for the in-hospital mortality of vertebral osteomyelitis (VO) patients.

METHODS

Based on the International Classification of Diseases, 10th Revision (ICD-10) codes for VO ("M46.2-", "M46.3-", and "M46.4-") data for total case numbers, secondary diagnoses, and numbers of in-hospital deaths were extracted from the Institute for the Hospital Remuneration System (InEK GmbH). Odds ratios (OR) for death were calculated for several secondary diseases and factors of interest.

RESULTS

Despite age, certain comorbidities were found to be strongly associated with increased mortality risk: Heart failure (OR = 2.80; 95% CI 2.45 to 3.20; p < 0.01), chronic kidney disease (OR = 1.83; 95% CI 1.57 to 2.13; p < 0.01), and diabetes with complications (OR = 1.86; 95% CI 1.46 to 2.38; p < 0.01). Among the complications, acute liver failure showed the highest risk for in-hospital mortality (OR = 42.41; 95% CI 23.47 to 76.62; p < 0.01). Additionally, stage III kidney failure (OR = 9.81; 95% CI 7.96 to 12.08; p < 0.01), sepsis (OR = 5.94; 95% CI 5.02 to 7.03; p < 0.01), acute respiratory failure (OR = 5.31; 95% CI 4.61 to 6.12; p < 0.01), and systemic inflammatory response syndrome (SIRS) (OR = 5.19; 95% CI 3.69 to 5.19; p < 0.01) were associated with in-hospital mortality. When analyzing the influence of pathogens, documented infection with Pseudomonas aeruginosa had the highest risk for mortality (OR = 2.74; 95% CI 2.07 to 3.63; p < 0.01), followed by Streptococci, Escherichia coli, and Staphylococcus aureus infections.

CONCLUSIONS

An early assessment of individual patient risk factors may be beneficial in the care and treatment of VO to help reduce the risks of mortality. These findings emphasize the importance of closely monitoring VO patients with chronic organ diseases, early detection and treatment of sepsis, and tailored empirical antibiotic therapy. The identification of specific pathogens and antibiotic susceptibility testing should be prioritized to improve patient outcomes in this high-risk population.

Positron Emission Tomography-Computed Tomography and Magnetic Resonance Imaging Assessments in a Mouse Model of Implant-Related Bone and Joint Staphylococcus aureus Infection

Osteomyelitis is an infection of the bone, associated with an inflammatory process. Imaging plays an important role in establishing the diagnosis and the most appropriate patient management. However, data are lacking regarding the use of preclinical molecular imaging techniques to assess osteomyelitis progression in experimental models. This study aimed to compare structural and molecular imaging to assess disease progression in a mouse model of implant-related bone and joint infections caused by Staphylococcus aureus. In SWISS mice, the right femur was implanted with a resorbable filament impregnated with S. aureus (infected group, n = 10) or sterile culture medium (uninfected group, n = 6). Eight animals (5 infected, 3 uninfected) were analyzed with magnetic resonance imaging (MRI) at 1, 2, and 3 weeks postintervention, and 8 mice were analyzed with [18F]fluorodeoxyglucose (FDG)-positron emission tomography (PET)-computed tomography (CT) at 48 h and at 1, 2, and 3 weeks postintervention. In infected animals, CT showed bone lesion progression, mainly in the distal epiphysis, although some uninfected animals presented evident bone sequestra at 3 weeks. MRI showed a lesion in the articular area that persisted for 3 weeks in infected animals. This lesion was smaller and less evident in the uninfected group. At 48 h postintervention, FDG-PET showed higher joint uptake in the infected group than in the uninfected group (P = 0.025). Over time, the difference between groups increased. These results indicate that FDG-PET imaging was much more sensitive than MRI and CT for differentiating between infection and inflammation at early stages. FDG-PET clearly distinguished between infection and postsurgical bone healing (in uninfected animals) from 48 h to 3 weeks after implantation. IMPORTANCE Our results encourage future investigations on the utility of the model for testing different therapeutic procedures for osteomyelitis.

Value of [18F]FDG PET/CT in diagnosis and management of spondylodiscitis

Vertebral osteomyelitis is the third most common form of osteomyelitis in patients over 50 years of age.Whereas prompt (pathogen-directed) therapy is crucially associated with better outcomes, the heterogeneous clinical presentation of disease with unspecific symptoms often delays adequate treatment initiation. Diagnosis requires a careful investigation of medical history, clinical findings and diagnostic imaging, including magnetic resonance imaging and nuclear medicine techniques.Due to its high sensitivity, [¹⁸F]FDG PET/CT is becoming increasingly important in diagnosis and management of spondylodiscitis, especially in the postoperative setting with presence of spinal hardware or other implantable devices in which MRI is limited.

The use of MRI, PET/CT, and nuclear scintigraphy in the imaging of pyogenic native vertebral osteomyelitis: a systematic review and meta-analysis

BACKGROUND CONTEXT

Native vertebral osteomyelitis (NVO) is a severe infection with an increasing incidence globally. Although there is no widely agreed upon reference standard for diagnosis of the disease, imaging plays a crucial role. Magnetic resonance imaging (MRI) is currently the imaging modality of choice. In recent years, advances in imaging have allowed for a larger role for alternative imaging techniques in the setting of NVO.

PURPOSE

Our aim was to evaluate the diagnostic accuracy of MRI, PET/CT, and nuclear imaging, namely 67Gallium and 99mTechnetium scintigraphy, in the diagnosis of pyogenic NVO.

STUDY DESIGN/SETTING

We conducted a systematic review of five medical databases and included all studies from 1970 to September 2021 that compared imaging techniques and provided sufficient data for diagnostic test accuracy meta-analysis.

METHODS

Abstract screening, full text review, and data extraction were done by a pair of independent reviewers. Nonnative and nonpyogenic patients were excluded. A bivariate random effect model was used for meta-analysis.

RESULTS

Twenty studies were included in the meta-analysis, encompassing a total of 1,123 imaging studies. The meta-analysis sensitivity and specificity of MRI were 90% and 72% respectively; those of PET/CT were 93% and 80%; those of 67Ga were 95% and 88%; those of 99mTc were 86% and 39%; and the sensitivity and specificity of combined Ga and Tc were 91% and 92% respectively in the setting of suspected NVO.

CONCLUSIONS

67Ga has the highest sensitivity for NVO, and its specificity is augmented when combined with 99mTc. MRI and PET/CT are both highly sensitive modalities, although the specificity of PET/CT is slightly better. MRI remains an appropriate initial test depending on the availability of other modalities.

The Epidemiology of Spondylodiscitis in Germany: A Descriptive Report of Incidence Rates, Pathogens, In-Hospital Mortality, and Hospital Stays between 2010 and 2020

BACKGROUND

Spondylodiscitis can lead to significant morbidity and mortality. Understanding its up-to-date epidemiological characteristics and trends is important to improve patient care.

METHODS

This study analyzed trends in the incidence rate of spondylodiscitis cases in Germany between 2010 and 2020, as well as the pathogens, in-hospital mortality rate, and length of hospital stay. Data were obtained from the Federal Statistical Office and the Institute for the Hospital Remuneration System database. The ICD-10 codes "M46.2-", "M46.3-" and "M46.4-" were evaluated.

RESULTS

The incidence rate of spondylodiscitis increased to 14.4/100,000 inhabitants, with 59.6% cases occurring in patients 70 years or older and affecting mainly the lumbar spine (56.2%). Absolute case numbers increased from 6886 by 41.6% to 9753 in 2020 (IIR = 1.39, 95% CI 0.62-3.08). Staphylococci and Escherichia coli were the most coded pathogens. The proportion of resistant pathogens was 12.9%. In-hospital mortality rates increased to a maximum of 64.7/1000 patients in 2020, intensive care unit treatment was documented in 2697 (27.7%) cases, and the length of stay per case was 22.3 days.

CONCLUSION

The sharply increasing incidence and in-hospital mortality rate of spondylodiscitis highlights the need for patient-centered therapy to improve patient outcomes, especially in the geriatric, frail population, which is prone to infectious diseases.

Implant Imaging: Perspectives of Nuclear Imaging in Implant, Biomaterial, and Stem Cell Research

Until now, very few efforts have been made to specifically trace, monitor, and visualize implantations, artificial organs, and bioengineered scaffolds for tissue engineering in vivo. While mainly X-Ray, CT, and MRI methods have been used for this purpose, the applications of more sensitive, quantitative, specific, radiotracer-based nuclear imaging techniques remain a challenge. As the need for biomaterials increases, so does the need for research tools to evaluate host responses. PET (positron emission tomography) and SPECT (single photon emission computer tomography) techniques are promising tools for the clinical translation of such regenerative medicine and tissue engineering efforts. These tracer-based methods offer unique and inevitable support, providing specific, quantitative, visual, non-invasive feedback on implanted biomaterials, devices, or transplanted cells. PET and SPECT can improve and accelerate these studies through biocompatibility, inertivity, and immune-response evaluations over long investigational periods at high sensitivities with low limits of detection. The wide range of radiopharmaceuticals, the newly developed specific bacteria, and the inflammation of specific or fibrosis-specific tracers as well as labeled individual nanomaterials can represent new, valuable tools for implant research. This review aims to summarize the opportunities of nuclear-imaging-supported implant research, including bone, fibrosis, bacteria, nanoparticle, and cell imaging, as well as the latest cutting-edge pretargeting methods.

Advanced Imaging for Detection of Foci of Infection in Staphylococcus aureus Bacteremia- Can a Scan Save Lives?

Bloodstream infection or sepsis is a common cause of mortality globally. Staphylococcus aureus (S. aureus) is of particular concern, through its ability to seed metastatic infections in almost any organ after entering the bloodstream (S. aureus bacteraemia), often without localising signs. A positive blood culture for S. aureus bacteria should lead to immediate and urgent identification of the cause. Failure to detect a precise focus of infection is associated with higher mortality, sometimes despite appropriate antibiotics. This is likely due to the limited ability to effectively target therapy in occult lesions. Early detection of foci of metastatic S. aureus infection is therefore key for optimal diagnosis and subsequent therapeutic management. 18F-FDG-PET/CT and MRI offer us invaluable tools in the localisation of foci of S. aureus infection. Crucially, they may identify unexpected foci at previously unsuspected locations in the body, for example vertebral osteomyelitis in the absence of back pain. S. aureus bloodstream infections are further complicated by their microbiological recurrence; 18F-FDG-PET/CT provide a means of localising, thus enabling source control. More evidence is emerging as to the utility of 18F-FDG-PET/CT in this setting, perhaps even to the point of reducing mortality. 18 F-FDG-PET/MRI may have a similar impact. The available evidence demonstrates a need to investigate the impact of 18F-FDG-PET/CT and MRI scanning in clinical management and outcomes of S. aureus infection further in a randomised prospective clinical trial.

[A vertebral polymicrobial osteomyelitis with atypicial microorganisms: A case report]

Vertebral Osteomyelitis (VO) is a rare disease, which has seen a gradual increase in its incidence over the past years. Here, we report a case, showing how difficult it can be to diagnose and manage a therapy in case of atypical microorganism. A 68-year-old man was hospitalized for a VO documented by blood cultures at Bacteroides fragilis. He first progressed favorably, but an increase in lumbar pain prompted, after an IRM, a percutaneous needle biopsy (PNB) that documented a recurrent VO at Corynebacterium striatum. In the face of this multi-microbial VO with atypicals microorganisms, a first PNB could have been discussed despite the positive blood cultures. This case report illustrates the complexity of management of VO, and its evolution according to the latest recommendations (interest of RMI during the follow-up, place of the TEP-scan, terms and conditions of immobilization, antibiotic administration methods).

Prognostic value of 18F-FDG PET/CT in malignant pleural mesothelioma: a meta-analysis

BACKGROUND

Several FDG PET/CT parameters have been utilized to evaluate the prognosis in malignant pleural mesothelioma (MPM). However, there are still controversial results due to the low incidence of MPM.

PURPOSE

To assess the prognostic value of 18F-FDG PET/CT in MPM.

MATERIAL AND METHODS

A systematic literature search was performed in PubMed, Embase, Medline, and The Cochrane Library to identify eligible studies from inception to 12 February 2020. The pooled hazard ratios (HRs) and 95% confidence intervals (CIs) of several variables, such as maximum standardized uptake value (SUV_max), the reduction of SUV_max after treatment (ΔSUV_max), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and the reduction of TLG after treatment (ΔTLG), were calculated. Meta-regression with subsequent subgroup analyses were conducted to determine the heterogeneity of cutoff values, treatment regimen, study design, uptake time, and scanners across various studies.

RESULTS

In total, 19 eligible studies including 1819 patients were enrolled in the meta-analysis. The univariate analysis showed that the pooled HRs (95% CI) of SUV_max, ΔSUV_max, MTV, TLG, and ΔTLG were 1.29 (1.16-1.42), 1.12 (1.05-1.19), 1.15 (1.00-1.33), 1.47 (1.23-1.76), and 1.27 (1.12-1.45), respectively. The multivariate analysis showed that the pooled HRs (95% CI) of SUV_max, ΔSUV_max, MTV, and TLG for overall survival (OS) were 1.20 (1.08-1.33), 1.10 (1.02-1.19), 0.95 (0.81-1.11), and 1.13 (1.08-1.18), respectively.

CONCLUSION

SUV_max, ΔSUV_max, TLG, and ΔTLG are significant prognostic indicators for OS, while more clinical studies are needed to confirm the prognostic value of MTV in MPM.

Diagnostic accuracy of fluorine-18 fluorodeoxyglucose positron emission tomography for suspected primary and postoperative pyogenic spondylitis

OBJECTIVE

Fluorine-18 fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET) and PET/CT have been suggested for confirming or excluding musculoskeletal infection but the diagnostic value of this tool for pyogenic spondylitis remains to be confirmed. This meta-analysis was performed to verify the accuracy of ¹⁸F-FDG PET and PET/CT in diagnosing suspected pyogenic spondylitis by performing a systematic review and meta-analysis.

METHODS

We conducted a comprehensive literature search of PubMed, Embase and Cochrane Library to retrieve diagnostic accuracy studies in which suspected pyogenic spondylitis was assessed with ¹⁸F-FDG PET or PET/CT. The pooled sensitivity, specificity, likelihood ratios, diagnostic odds ratio (DOR), summarized receiver operating characteristic curve (sROC) and the area under the sROC (AUC) were calculated by using Stata software.

RESULTS

A total of 18 eligible studies (660 patients) with suspected pyogenic spondylitis were included in the quantitative analysis. ¹⁸F-FDG PET and PET/CT illustrated relatively high sensitivity (0.91, 95% CI: 0.84-0.95) and specificity (0.90, 95% CI: 0.79-0.95) for the diagnosis of pyogenic spondylitis. The pooled DOR and AUC were 86.00 (95% CI, 31.00-240.00) and 0.96 (95% CI, 0.94-0.97), respectively. For diagnosing pyogenic spondylitis without previous spine surgery, the pooled sensitivity, specificity, DOR and AUC were 0.93 (95% CI, 0.85-0.97), 0.91 (95% CI, 0.77-0.97), 136 (95% CI, 35-530) and 0.97 (95% CI, 0.95-0.98), respectively. For diagnosing postoperative pyogenic spondylitis, the pooled sensitivity, specificity, DOR and AUC were 0.85 (95% CI, 0.71 to 0.93), 0.87 (95% CI, 0.66 to 0.96), 38 (95% CI, 9 to 167) and 0.92 (95% CI, 0.89 to 0.94), respectively.

CONCLUSION

¹⁸F-FDG PET and PET/CT presented satisfactory accuracy for diagnosing pyogenic spondylitis. The diagnostic effect of this nuclear imaging method for pyogenic spondylitis without previous spine surgery seems to be better than that for the postoperative ones. However, whether ¹⁸F-FDG PET and PET/CT could become a routine in patients with suspected pyogenic spondylitis remains to be confirmed.

LEVEL OF EVIDENCE

Level I evidence, a summary of meta-analysis.

The Role of Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in the Management of Brucellosis: An Observational Cohort Study

Background

Diagnosis of focal infection in brucellosis is important to direct optimal treatment. Fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) may be helpful in this aspect.

Methods

The clinical and imaging data of all patients with brucellosis, who underwent FDG PET/CT as part of the investigation in Rambam Health Care Campus, where FDG PET/CT became the recommended imaging modality for suspected focal infection in brucellosis since 2016, were analyzed retrospectively. The detection of focal infection as well as management modification before and after FDG PET/CT were recorded.

Results

FDG PET/CT was performed in 30 episodes of brucellosis occurring in 27 patients: 20 primary episodes and 10 suspected relapse episodes. The mean age of the patients was 50 ± 15.07 years. Focal disease was diagnosed in 18 of 30 (60%) episodes, of which 8 (26.6%) were diagnosed for the first time by FDG PET/CT, all of whom had spinal infection, with a concomitant additional focus in 5. Overall, multifocal disease was diagnosed in 10 of 18 (55.5%) of patients with focal disease. Management modification following FDG PET/CT was recorded in 17 of 30 (56.6%) episodes, mainly by treatment extension in spinal infection and withholding treatment in patients with suspected relapse but no evidence of active disease by FDG PET/CT.

Conclusions

FDG PET/CT was found to be helpful in the diagnosis of focal infection in brucellosis. Multifocal disease seems more prevalent than previously described. The clinical impact of adding FDG PET/CT to the diagnostic workup of brucellosis should be evaluated in future studies.

Diagnostic value of hybrid FDG-PET/MR imaging of chronic osteomyelitis

Background

Magnetic resonance imaging (MRI) and 2-[¹⁸F]-fluoro-2-deoxy-d-glucose (¹⁸F-FDG) Positron Emission Tomography, paired with Computed Tomography (PET/CT) are commonly used modalities in the complicated diagnostic work-up of osteomyelitis. PET/MRI is a relatively novel hybrid modality with suggested applications in bone infection imaging, based on expert opinion and previous qualitative research. ¹⁸F-FDG PET/MRI has the advantages of reduced radiation dose, more soft tissue information, and is deemed more valuable for surgical planning compared to ¹⁸F-FDG PET/CT. The goal of this study is to quantitatively assess the diagnostic value of hybrid ¹⁸F-FDG PET/MRI for chronic osteomyelitis.

Methods

A retrospective analysis was performed by a nuclear medicine physician and radiologist on 36 patients with ¹⁸F-FDG PET/MRI scans for suspected osteomyelitis. Sensitivity, specificity, and accuracy were determined with the clinical assessment by the orthopaedic surgeon (based on subsequent intraoperative microbiology or long-term follow-up) as the ground truth. Standardized uptake values (SUV) were measured and analysed by means of receiver operating characteristics (ROC).

Results

This first study to quantitatively report the diagnostic value of ¹⁸F-FDG PET/MRI yielded a sensitivity, specificity, and accuracy of 78%, 100%, and 86% respectively. Area under the ROC curve was .736, .755, and .769 for the SUVmax, target to background ratio, and SUVmax_ratio respectively. These results are in the same range and not statistically different compared to diagnostic value for ¹⁸F-FDG PET/CT imaging of osteomyelitis in literature.

Conclusions

Based on the aforementioned advantages of ¹⁸F-FDG PET/MRI and the diagnostic value reported here, the authors propose ¹⁸F-FDG PET/MRI as an alternative to ¹⁸F-FDG PET/CT in osteomyelitis diagnosis, if available.

PET/MRI in Pediatric Neuroimaging: Primer for Clinical Practice

Modern pediatric imaging seeks to provide not only exceptional anatomic detail but also physiologic and metabolic information of the pathology in question with as little radiation penalty as possible. Hybrid PET/MR imaging combines exquisite soft-tissue information obtained by MR imaging with functional information provided by PET, including metabolic markers, receptor binding, perfusion, and neurotransmitter release data. In pediatric neuro-oncology, PET/MR imaging is, in many ways, ideal for follow-up compared with PET/CT, given the superiority of MR imaging in neuroimaging compared with CT and the lower radiation dose, which is relevant in serial imaging and long-term follow-up of pediatric patients. In addition, although MR imaging is the main imaging technique for the evaluation of spinal pathology, PET/MR imaging may provide useful information in several clinical scenarios, including tumor staging and follow-up, treatment response assessment of spinal malignancies, and vertebral osteomyelitis. This review article covers neuropediatric applications of PET/MR imaging in addition to considerations regarding radiopharmaceuticals, imaging protocols, and current challenges to clinical implementation.

Diagnosis of vertebral osteomyelitis

Native vertebral osteomyelitis (NVO) is a potentially fatal infection which has seen a gradual increase in its incidence over the past decades. The infection is insidious, presenting with symptoms of back pain. Fever is present in about 60 % of patients. Prompt diagnosis of NVO is important to prevent the development of complications. Numerous laboratory and imaging tools can be deployed to accurately establish the diagnosis. Imaging techniques such as magnetic resonance, nuclear imaging, and computed tomography are essential in diagnosing NVO but can also be useful in image-guided biopsies. Laboratory tools include routine blood tests, inflammatory markers, and routine culture techniques of aspirated specimens. Recent advances in molecular techniques can assist in identifying offending pathogen(s). In this review, we detail the arsenal of techniques that can be utilized to reach a diagnosis of NVO.

Klebsiella Discitis in a 15-Year-Old Male Diagnosed With Plasma Microbial Cell-Free DNA Next-Generation Sequencing Test: A Case Report

Spinal discitis (SD) is a rare condition, particularly in the pediatric population. The course of SD may be acute or chronic, and the non-specificity of symptoms leads to great delays in diagnosis. The most commonly isolated causative organism is Staphylococcus aureus whereas gram-negative infections are hardly ever reported in the literature. Comorbidities that increase the risk of bacteremia such as diabetes, chronic kidney disease, HIV, and cancer are major risk factors for SD. Hereby, we present an atypical case of SD in a previously healthy 15-year-old male with an unusual organism, Klebsiella aerogenes, diagnosed by plasma microbial cell-free DNA with negative blood cultures. The clinical course was complicated by antibiotic resistance and subsequent development of a ventral epidural abscess requiring readmission followed by surgical drainage of the abscess with a prolonged course of antibiotics.

Individualizing the use of [18F]FDG-PET/CT in patients with complicated Staphylococcus aureus bacteremia: experiences from a tertiary care center

Purpose

[¹⁸F]FDG-PET/CT scanning can help detect metastatic infectious foci and reduce mortality in patients with Staphylococcus aureus bacteremia (SAB), but it is unknown if patients with SAB and an indication for prolonged treatment because of possible endovascular, orthopaedic implant, or other metastatic infection still need [¹⁸F]FDG-PET/CT.

Methods

In a retrospective single-center cohort study, we included all consecutive adult patients with SAB between 2013 and 2020 if an [¹⁸F]FDG-PET/CT scan was performed and antibiotic treatment was planned for ≥ 6 weeks prior to [¹⁸F]FDG-PET/CT. We aimed to identify patients for whom treatment was adjusted due to the results of [¹⁸F]FDG-PET/CT, and assessed concordance of [¹⁸F]FDG-PET/CT and clinical diagnosis for infected prosthetic material.

Results

Among 132 patients included, the original treatment plan was changed after [¹⁸F]FDG-PET/CT in 22 patients (16.7%), in the majority (n = 20) due to diagnosing or rejecting endovascular (graft) infection. Antibiotic treatment modifications were shortening in 2, iv-oral switch in 3, extension in 13, and addition of rifampicin in 4 patients. Ninety additional metastatic foci based on [¹⁸F]FDG-PET/CT results were found in 69/132 patients (52.3%). [¹⁸F]FDG-PET/CT suggested vascular graft infection in 7/14 patients who lacked clinical signs of infection, but showed no infection of prosthetic joints or osteosynthesis material in eight patients who lacked clinical signs of such an infection.

Conclusion

[¹⁸F]FDG-PET/CT can help refine treatment for SAB in patients with clinically suspected endovascular infection or vascular grafts, even if 6 weeks treatment is already indicated, but can be safely omitted in other patients who are clinically stable.

Supplementary Information

The online version contains supplementary material available at 10.1007/s15010-021-01740-4.

ACR Appropriateness Criteria® Suspected Spine Infection

Spine infection is both a clinical and diagnostic imaging challenge due to its relatively indolent and nonspecific clinical presentation. The diagnosis of spine infection is based upon a combination of clinical suspicion, imaging evaluation and, when possible, microbiologic confirmation performed from blood cultures or image-guided percutaneous or open spine biopsy. With respect to the imaging evaluation of suspected spine infection, MRI without and with contrast of the affected spine segment is the initial diagnostic test of choice. As noncontrast MRI of the spine is often used in the evaluation of back or neck pain not responding to conservative medical management, it may show findings that are suggestive of infection, hence this procedure may also be considered in the evaluation of suspected spine infection. Nuclear medicine studies, including skeletal scintigraphy, gallium scan, and FDG-PET/CT, may be helpful in equivocal or select cases. Similarly, radiography and CT may be appropriate for assessing overall spinal stability, spine alignment, osseous integrity and, when present, the status of spine instrumentation or spine implants. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Spine Infections: the role of Fluorodeoxyglucose Positron Emission Tomography (FDG PET) in the context of the actual diagnosis guideline

Spondylodiscitis is an infectious process that requires numerous health care professionals to be clearly diagnosed and eventually successfully treated. It implies a variety of microbiological agents and conditions; during the diagnostic workup, it is difficult to correctly identify them, and the clinician has to rapidly choose the correct treatment to avoid permanent injuries to the patient. In this context, we conducted a review to better understand the most suitable use of Positron Emission Tomography with 18-Fluoro-deossi-glucose (FDG PET) in a patient suspected of spondylodiscitis, based on current guidelines and literature.. We wanted to review the role of FDG PET in the spondylodiscitis diagnosis and follow up in the context of the current guidelines.

The Diagnostic Value of Fluorine-18 Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography for the Detection of Surgical Site Infection after Spine Surgery

STUDY DESIGN

Retrospective case series.

OBJECTIVE

The purpose of this study was to assess the diagnostic yield of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (F-18 FDG PET/CT) for surgical site infection (SSI) after spine surgery.

SUMMARY OF BACKGROUND DATA

Diagnosis of SSI in the spine based on F-18 FDG PET/CT requires experienced nuclear medical physicians for a detailed analysis of F-18 FDG distribution pattern. It has also been reported that increases in the maximal standardized uptake values of F-18 FDG (SUVmax) closely correlated with SSI, suggesting potential of more objective and quantitative diagnosis.

METHODS

We assessed the diagnostic yield of F-18 FDG PET/CT (pattern-based diagnosis by nuclear medical physicians and SUVmax-based diagnosis) for SSI in 52 subjects who underwent spine surgery. The 52 subjects included 11 nonimplant and 41 implant cases. F-18 FDG PET/CT was performed in 33 and 19 cases in early (≤12 weeks after the surgery) and late (>12 weeks) phases, respectively. The final diagnosis of SSI was based on the results of pathogen identification, plain radiography, and CT and/or magnetic resonance imaging or response to antibiotics and/or reoperation.

RESULTS

SUVmax-based diagnosis was performed with a cut off value of 5.0 as determined by receiver operating characteristic analysis. Both pattern-based and SUVmax-based diagnoses demonstrated excellent diagnostic yields with high sensitivity (97% and 90%), specificity (100% and 100%), and accuracy (98% and 94%). High diagnostic yields (accuracy of ≥90%) were consistently observed irrespective of presence or absence of implantation or interval between surgery and F-18 FDG PET/CT.

CONCLUSION

F-18 FDG PET/CT can be the procedure of choice for investigation of SSI in the spine when other imaging fails to provide a definitive diagnosis.Level of Evidence: 4.

[Infections of the spine : Pyogenic spondylodiscitis and implant-associated vertebral osteomyelitis]

Pyogenic (unspecific) spondylodiscitis and implant-associated vertebral osteomyelitis (IAVO) are important diseases with the risk of neurological and septic complications. An early diagnosis is essential in which magnetic resonance imaging (MRI), histopathology and microbiological identification of the pathogen play key roles. The goals of conservative treatment in uncomplicated spondylodiscitis are antibiotic infection control and pain management. In the case of sepsis, neurological deficits, segmental instability or epidural abscesses surgical treatment of the infection with stabilization of the spine should be considered. In IAVO the formation of a mature biofilm represents the transition from acute to chronic infection. Acute infections can be treated by extensive debridement in combination with biofilm-active antibiotic treatment while retaining the implant. In chronic infections implant removal or exchange in combination with several weeks of antibiotic treatment is often necessary.

Improvement of image quality using amplitude-based respiratory gating in PET-computed tomography scanning

OBJECTIVES

This study sought to provide data supporting the expanded clinical use of respiratory gating by assessing the diagnostic accuracy of breathing motion correction using amplitude-based respiratory gating.

METHODS

A respiratory movement tracking device was attached to a PET-computed tomography scanner, and images were obtained in respiratory gating mode using a motion phantom that was capable of sensing vertical motion. Specifically, after setting amplitude changes and intervals according to the movement cycle using a total of nine combinations of three waveforms and three amplitude ranges, respiratory motion-corrected images were reconstructed using the filtered back projection method. After defining areas of interest in the acquired images in the same image planes, statistical analyses were performed to compare differences in standardized uptake value (SUV), lesion volume, full width at half maximum (FWHM), signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR).

RESULTS

SUVmax increased by 89.9%, and lesion volume decreased by 27.9%. Full width at half maximum decreased by 53.9%, signal-to-noise ratio increased by 11% and contrast-to-noise ratio increased by 16.3%. Optimal results were obtained when using a rest waveform and 35% duty cycle, in which the change in amplitude in the respiratory phase signal was low, and a constant level of long breaths was maintained.

CONCLUSIONS

These results demonstrate that respiratory-gated PET-CT imaging can be used to accurately correct for SUV changes and image distortion caused by respiratory motion, thereby providing excellent imaging information and quality.

Molecular imaging in MSK radiology: Where are we going?

Musculoskeletal (MSK) pathologies are one of the leading causes of disability worldwide. However, treatment options and understanding of pathogenetic processes are still partially unclear, mainly due to a limited ability in early disease detection and response to therapy assessment. In this scenario, thanks to a strong technological advancement, structural imaging is currently established as the gold-standard of diagnosis in many MSK disorders but each single diagnostic modality (plain films, high-resolution ultrasound, computed tomography and magnetic resonance) still suffer by a low specificity regarding the characterization of inflammatory processes, the quantification of inflammatory activity levels, and the degree of response to therapy. To overcome these limitations, molecular imaging techniques may play a promising role. Starting from the strengths and weaknesses of structural anatomical imaging, the present narrative review aims to highlight the promising role of molecular imaging in the assessment of non-neoplastic MSK diseases with a special focus on its role to monitor treatment response.

[The application of fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography in inflammation and infectious disease]

2-［ 18F］-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography ( 18F-FDG PET/CT) combining positron emission tomography with computed tomography is used to evaluate the body's glucose metabolic changes under different conditions. In addition to its established role in oncological imaging, 18F-FDG PET/CT has clinical utility in suspected inflammation and infection. The technique can identify the source of infection in a timely fashion ahead of morphological changes, map the extent and severity of inflammation, guide the site for tissue biopsy and assess therapy response. This article reviewed the use of 18F-FDG PET/CT in infection and inflammation, such as fever of unknown origin, sarcoidosis, vessel vasculitis, osteomyelitis, joint prosthesis or implant-related complications, human immunodeficiency virus-related infections, and other indications, such as inflammatory bowel disease, so as to provide reference for clinicians to select 18F-FDG PET/CT to help them in the diagnosis and treatment of inflammatory diseases.

A Retrospective Study of predicting risk of Metastasis among FDG-avid Bone Lesions in 18F-FDG PET/CT

Purpose: We evaluated the imaging and clinical features for discriminating the possibility of metastasis among FDG-avid bone lesions in 18F-FDG PET/CT in patients who have received bone biopsy.

Methods: The retrospective study included patients who underwent both ¹⁸F-FDG PET/CT and bone biopsy for FDG-avid bone lesions. Bone lesions maximum standardized uptake value (SUVmax), CT findings, alongside with common clinical features were analyzed.

Results: From the 338 patients enrolled in the final study, all of them were received bone biopsy. Biopsies confirm metastasis in 256 cases (75.74%) and benign tissue in 82 cases (24.26%). Metastasis group had higher bone SUVmax than benign group (median 7.9 vs 4.5, p <0.001). A cutoff bone SUVmax of 5 achieved an AUC of 0.748 in all patients. Lytic CT feature and higher age were more likely frequent in metastasis group. Moreover, in patients without obvious CT abnormality (45, 13.31%), the AUC was 0.743 by a SUVmax cutoff of 5.38, whilst in patients with a solitary bone lesion (74, 21.89%), the AUC was 0.803 by a SUVmax cutoff of 4.3.

Conclusions: SUVmax is a promising and valuable metabolic indicator for predicting risk of metastasis among FDG-avid bone lesions in 18F-FDG PET/CT, ancillary clinical and imaging features may increase the probability of a metastatic bone lesion.

Potential Applications of PET/CT/MR Imaging in Inflammatory Diseases: Part I: Musculoskeletal and Gastrointestinal Systems

During the past decades, the role of fludeoxyglucose (FDG)-PET and hybrid PET/computed tomography (CT) has been established clinically in the diagnostic workup of a multitude of infectious and inflammatory disorders. In recent years, the fusion of MR imaging to PET has also been increasingly explored, and this may be especially useful in musculoskeletal and gastrointestinal inflammatory diseases due to exceptional soft tissue contrast and reduced radiation dose. This article outlines the current potential for hybrid molecular imaging in the musculoskeletal system and the gastrointestinal tract with special focus on the potential for fused PET/CT/MR imaging.

Rabbit model of Staphylococcus aureus implant-associated spinal infection

Post-surgical implant-associated spinal infection is a devastating complication commonly caused by Staphylococcus aureus. Biofilm formation is thought to reduce penetration of antibiotics and immune cells, contributing to chronic and difficult-to-treat infections. A rabbit model of a posterior-approach spinal surgery was created, in which bilateral titanium pedicle screws were interconnected by a plate at the level of lumbar vertebra L6 and inoculated with a methicillin-resistant S.aureus (MRSA) bioluminescent strain. In vivo whole-animal bioluminescence imaging (BLI) and ex vivo bacterial cultures demonstrated a peak in bacterial burden by day 14, when wound dehiscence occurred. Structures suggestive of biofilm, visualized by scanning electron microscopy, were evident up to 56 days following infection. Infection-induced inflammation and bone remodeling were also monitored using ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) and computed tomography (CT). PET imaging signals were noted in the soft tissue and bone surrounding the implanted materials. CT imaging demonstrated marked bone remodeling and a decrease in dense bone at the infection sites. This rabbit model of implant-associated spinal infection provides a valuable preclinical in vivo approach to investigate the pathogenesis of implant-associated spinal infections and to evaluate novel therapeutics.

Summary: A model of post-surgical methicillin-resistant Staphylococcus aureus implant-associated spinal infection was created in rabbits, recapitulating acute infection as well as chronic low-burden infection, with structures suggestive of biofilm formation and bone remodeling.

Imaging in the investigation and management of Staphylococcus aureus bacteraemia: a role for advanced imaging techniques

Staphylococcus aureus bacteraemia (SAB) continues to affect ∼25,000 patients in the UK per year with a high crude mortality of 30% at 90 days. Prompt source control improves outcomes in sepsis and SAB and is included in sepsis guidelines. A recent clinical trial of adjunctive antibiotic treatment in SAB found that the majority of recurrences of SAB were associated with a failure of source management. In this condition, the ability to control the source of infection may be limited by the ability to detect a focus of infection. Echocardiogram is now a routinely used tool to detect such unknown foci in the form of unexpected infectious vegetations. We review the literature to explore the utility of advanced imaging techniques, such as [18F]fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) and magnetic resonance imaging (including whole-body MRI), to detect foci which may otherwise be missed. As unknown foci are associated with increased mortality, we propose that increasing the detection of foci could enable improved source control and result in improved outcomes in SAB.

Real-world experience of the role of 18F FDG PET-computed tomography in chronic spinal implant infection

OBJECTIVES

The presence of postinstrumentation back pain in patients after undergoing spinal surgery is a well established phenomenon. So too is the presence of infection, both overt and subclinical which can be a source of pain. The accurate assessment of infection in patients with spinal implants in situ and no overt radiological or biochemical abnormalities frequently presents a diagnostic challenge. We present our experience spanning 5 years of using 2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography (18F FDG PET)-computed tomography (CT) scans to aid the diagnostic process in treating presumed low-grade chronic implant infection.

METHODS

We undertook a retrospective analysis of all patients with spinal implants in place who were referred for 18F FDG PET-CT imaging over a 5-year period. All available images, case notes and laboratory results were reviewed.

RESULTS

Data pertaining to 49 patients were analysed, with infection diagnosed on 18F FDG PET-CT in 24 (45%) of those sent for scanning. Fifteen patients in the cohort underwent revision surgery, and 11 of whom had been diagnosed as infected on PET-CT. Confirmation of infection with positive microbiological sampling occurred in 8/11 giving a positive predictive value of 0.72 in our series.

CONCLUSION

We present a real-world experience of using 18F FDG PET-CT as a diagnostic tool in the evaluation of patients with chronic pain after undergoing spinal implantation. We have found PET-CT to be a promising modality and would recommend multicentre collaboration to ensure reproducibility across more centres.

Role of 18F-flurodeoxyglucose in orthopaedic implant-related infection: review of literature and experience

Infection and inflammation are a common occurrence with orthopaedic procedures. Anatomical modalities can show the transformation in the disease process; however, these may occur later when compared with functional imaging modalities that are more likely to identify early disease patterns. Various molecular imaging modalities such as three-phase bone scintigraphy, labelled leucocyte scintigraphy, as well as radiolabelled antibiotics and immunoglobulins have been considered and have played key roles in assisting clinical decision-making. While 18F-flurodeoxyglucose (FDG) PET/computed tomography (CT) has been relatively well established in cancer pathways, it has the potential to contribute to surgical decision making for possible osteomyelitis post-metal implant surgery. In this article, we present a review of recently used tracers, and share our experience with using 18F-FDG PET/CT studies in a few diverse clinical settings related to post-metal implant osteomyelitis.

Diagnostic performance of 18F-FDG PET/CT in patients with spinal infection: a systematic review and a bivariate meta-analysis

PURPOSE

Diagnosis of spinal infection (SI) is challenging and usually requires multiple tests. We aimed to perform a systematic review and a bivariate meta-analysis on the diagnostic role of ¹⁸F-FDG PET/CT in patients with SI.

METHODS

A comprehensive literature search of studies published through February 2019 in PubMed/MEDLINE and Cochrane library databases was carried out. Studies investigating the diagnostic performance of ¹⁸F-FDG PET/CT in patients with SI were eligible for inclusion in the qualitative analysis. For the quantitative analysis, pooled sensitivity, specificity, positive and negative likelihood ratio (LR+ and LR-) and diagnostic odds ratio (DOR) of ¹⁸F-FDG PET/CT in patients with suspected SI were calculated on a per examination-based analysis. Pooled data were presented with 95% confidence intervals (95% CI).

RESULTS

Twenty-six articles (833 patients) using ¹⁸F-FDG PET/CT were eligible for the qualitative analysis. Twelve studies (396 patients) were selected for the meta-analysis. Overall, ¹⁸F-FDG PET/CT demonstrated a very good diagnostic performance in patients with SI and several studies underlined the value of ¹⁸F-FDG PET/CT in assessing the response to treatment. The bivariate meta-analysis on ¹⁸F-FDG PET/CT in patients with suspected SI provided the following results: sensitivity 94.8% (95% CI 88.9-97.6%) and specificity 91.4% (95% CI 78.2-96.9%). The pooled LR+, LR- and DOR were 4.7 (95% CI 2.9-7.7), 0.11 (95% CI 0.07-0.16) and 63.4 (95% CI 28.9-139), respectively. No significant heterogeneity or publication bias was found.

CONCLUSION

¹⁸F-FDG PET/CT demonstrated a very good diagnostic performance in patients with SI and can be used in patients in which MRI cannot be performed or is non-diagnostic or inconclusive. Several studies underlined the value of ¹⁸F-FDG PET/CT in assessing the response to treatment in patients with SI. Overall, larger multicentre and prospective studies and cost-effectiveness analyses are warranted.

The role of 18F-FDG PET/CT in early infectious discitis: a case report after a negative MRI

We present the case of a 70 years old woman with infectious discitis which was detected using Fluorine fluodeoxiglucose positron emission tomography/computed tomography (18F-FDG PET/CT), after a negative magnetic resonance imaging. A Streptococuss gallolyticus (bovis gender bacteria) grow on culture. In addition 18F-FDG PET also demonstrated infectious endocarditis which was confirmed by transesophageal echocardiography and a colonic neoplasm. Here we have highlighted the potential role of 18F-FDG PET/CT study in patients with a clinical history suggestive of infectious discitis with a negative or indifferent magnetic resonance imaging.