Prospective comparison of whole-body (18)F-FDG PET/CT and MRI of the spine in the diagnosis of haematogenous spondylodiscitis

FDG-PET-CT as an early detection method for tuberculosis: a systematic review and meta-analysis

Tuberculosis (TB) causes major public health problems worldwide. Fighting TB requires sustained efforts in health prevention, diagnosis and treatment. Previous literature has shown that conventional diagnostic methods like X-ray and sputum microscopy often miss early or extrapulmonary TB due to their limited sensitivity. Blood tests, while useful, lack the anatomical detail needed for precise localization of TB lesions. A possible step forward in the fight against TB could be the use of Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) and Computed Tomography (CT). This meta-analysis discusses the current literature, including the methods, results and implications of using FDG-PET-CT in the early diagnosis of TB. Analysis of the studies showed that the sensitivity of FDG-PET-CT as a potential method for early detection of TB was 82.6%.

Multi-level tuberculosis of the spine identified by 18 F-FDG-PET/CT and concomitant urogenital tuberculosis: a case report from the spinal TB X cohort

BACKGROUND

Tuberculosis (TB) is caused by Mycobacterium tuberculosis (Mtb) and typically infects the lungs. However, extrapulmonary forms of TB can be found in approximately 20% of cases. It is suggested, that up to 10% of extrapulmonary TB affects the musculoskeletal system, in which spinal elements (spinal tuberculosis, STB) are involved in approximately 50% of the cases. STB is a debilitating disease with nonspecific symptoms and diagnosis is often delayed for months to years. In our Spinal TB X Cohort, we aim to describe the clinical phenotype of STB using whole-body 18 F-fluorodeoxyglucose positron emission tomography computed tomography (PET/CT) and to identify a specific gene expression profile for the different stages of dissemination on PET/CT. Here we report on the first patient recruited into our cohort who underwent PET/CT before treatment initiation, at 6-months and at 12-months - time of TB treatment completion.

CASE PRESENTATION

A 27-year-old immunocompetent male presented with severe thoracolumbar back pain for 9 months with severe antalgic gait and night sweats. Magnetic resonance imaging (MRI) of the whole spine revealed multilevel spinal disease (T5/6, T11/12, L3/4) in keeping with STB. After informed consent and recruitment into the Spinal TB X Cohort, the patient underwent PET/CT as per protocol, which revealed isolated multilevel STB (T4-7, T11/12, L3/4) with no concomitant lung or urogenital lesion. However, sputum and urine were Xpert MTB/RIF Ultra positive and Mtb was cultured from the urine sample. CT-guided biopsy of the T11/12 lesion confirmed drug-sensitive Mtb on Xpert MTB/RIF Ultra and the patient was started on TB treatment according to local guidelines for 12 months. The 6-month follow-up PET/CT revealed new and existing spinal lesions with increased FDG-uptake despite significant improvement of clinical features and laboratory markers. After 9 months of treatment, the patient developed an acute urethral stricture, most likely due to urogenital TB, and a suprapubic catheter was inserted. The 12-month PET/CT showed significantly decreased PET/CT values of all lesions, however, significant persistent spinal inflammation was present at the end of TB treatment. Clinically, the patient was considered cured by the TB control program and currently awaits urethroplasty.

CONCLUSIONS

In our case, PET/CT emerged as a valuable imaging modality for the initial assessment, surpassing MRI by revealing more comprehensive extensive disease. Subsequent PET/CT scans at 6-month uncovered new lesions and increased inflammation in existing ones, while by the end of TB treatment, all lesions exhibited improvement. However, the interpretation of FDG avidity remains ambiguous, whether it correlates with active infection and viable Mtb. or fibro- and osteoblast activity indicative of the healing process. Additionally, the absence of extraspinal TB lesions on PET/CT despite positive microbiology from sputum and urine maybe explained by paucibacillary, subclinical infection of extraspinal organs. The Spinal TB X Cohort endeavours to shed light on whole-body imaging patterns at diagnosis, their evolution midway through TB treatment, and upon treatment completion. Ultimately, this study aims to advance our understanding of the biology of this complex disease.

PET/CT and SPECT/CT for Infection in Joints and Bones: An Overview and Future Directions

Infections of the bones and joints, if misdiagnosed, may result in serious morbidity and even mortality. A prompt diagnosis followed by appropriate management may reduce the socioeconomic impact of bone and joint infections. Morphologic imaging such as ultrasound and plain radiographs form the first line investigations, however, in early infections findings may be negative or nonspecific. Nuclear medicine imaging techniques play a complementary role to morphologic imaging in the diagnosis of bone and joint infections. The availability of hybrid systems (SPECT/CT, SPECT/MRI, PET/CT or PET/MRI) offers improved specificity with ability to assess the extent of infection. Bone scans are useful as a gatekeeper wherein negative scans rule out sepsis with a good accuracy, however positive scans are nondiagnostic and more specific tracers should be considered. These include the use of labeled white blood cells and antigranulocyte antibodies. Various qualitative and quantitative interpretation criteria have been suggested to improve the specificity of the scans. PET has better image resolution and 18F-FDG is the major tracer for PET imaging with applications in oncology and inflammatory/infective disorders. It has demonstrated improved sensitivity over the SPECT based tracers, however, still suffers from lack of specificity. 18F-FDG PET has been used to monitor therapy in bone and joint infections. Other less studied, noncommercialized SPECT and PET tracers such as 111In-Biotin, 99mTc-Ubiquicidin, 18F-Na-Fluoride, 18F-labeled white blood cells and 124I-Fialuridine to name a few have shown great promise, however, their role in various bone and joint infections has not been established. Hybrid imaging with PET or PET/MRI offers huge potential for improving diagnostics in infections of the joints and bones.

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.

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.

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.

Imaging of Spondylodiscitis: An Update

Spondylodiscitis is an infection of the vertebral body and/or intervertebral disc, which can also involve the epidural space, posterior elements, and paraspinal soft tissues. Due to high morbidity and mortality, prompt diagnosis and treatment of spondylodiscitis is critical. However, diagnosis can be challenging due to nonspecific signs and symptoms. Magnetic resonance imaging with and without contrast is the imaging modality of choice due to high sensitivity and specificity. Intravenous administration of gadolinium contrast can better demonstrate the extent of soft tissue and bone abscesses. However, magnetic resonance imaging is less useful in the evaluation of treatment response. When magnetic resonance imaging cannot be performed or is not diagnostic, radionuclide imaging is a useful alternative. Although bone scintigraphy frequently is used as a screening test, false negative results can occur early in the course of the infection and in the elderly. This test is not useful for detecting the soft tissue infections that often accompany or mimic spondylodiscitis. Gallium-67 citrate improves the specificity of the bone scan, can detect infection earlier than the bone scan, may be more sensitive, especially in elderly patients, and identifies accompanying soft tissue infection. Performing SPECT and SPECT/CT improve accuracy. The 2-3 day delay between radiopharmaceutical administration, poor image quality, and relatively high patient radiation dose are significant disadvantages of gallium-67. Furthermore gallium-67 is no longer as readily available as it once was. ¹⁸F-FDG imaging is the radionuclide test of choice for spondylodiscitis. The procedure, completed in one day, is sensitive, has a high negative predictive value, and reliably differentiates degenerative from infectious vertebral body end-plate abnormalities. ¹⁸F-FDG has outperformed bone and gallium-67 imaging in comparative studies. ¹⁸F-FDG may be able to provide an objective means for monitoring response to treatment. The potential of other agents for diagnosing spondylodiscitis has been studied. Although indium-111biotin accurately diagnoses spondylodiscitis, this radiopharmaceutical has never been commercially available. Gallium-68 citrate and ^99mTc-radiolabeled antimicrobial peptides have been investigated, but their role in the diagnosis of spondylodiscitis has not been established. Labeled leukocyte scintigraphy has no role in the diagnosis of spondylodiscitis.

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.

Imaging in the Diagnosis of Nonspecific Pyogenic Spondylodiskitis

The prevalence of nonspecific pyogenic spondylodiskitis, associated with both a high morbidity and a high mortality, has increased in the last few decades. The diagnosis is often delayed because of the nonspecific clinical manifestation at the early stage. The reliability of radiographs is limited, particularly in early stage after the onset of infection. Computed tomography (CT) can reliably assess the bony condition with the possibility of spatial visualization. Contrast enhancement supports the detection of affected soft tissue. Magnetic resonance imaging (MRI) continues to be the gold standard in the diagnosis of spondylodiskitis. Sophisticated investigation protocols supported by gadolinium enhancement secure the diagnosis. MRI has a high resolution without radiation exposure. Different nuclear investigation techniques extend the diagnostic options. Reports of 18F-fluorodeoxyglucose-positron emission tomography (18-FDG-PET) are particularly promising to confirm the diagnosis. The drawback of the reduced image quality with respect to detailed anatomical information can be overcome by a combined simultaneous acquisition of CT or MRI. With respect to one of the greatest challenges, the differentiation between degenerative changes (Modic type 1) and infection at an early stage using differentiated MRI protocols and FDG-PET is promising. This overview presents a concise state-of-the-art look at radiologic investigations in case of suspected nonspecific pyogenic spondylodiskitis with the focus on a pragmatic approach.

Detection of Spinal Tuberculosis by F-18 FDG PET/CT as a Cause of Unusual Referred Pain in the Right Upper Quadrant of Abdomen

Tuberculous involvement of the spine (tuberculosis [TB] spine) can cause severe morbidity unless detected and treated early. Apart from the constitutional symptoms, it can present with back pain, kyphosis, gait abnormality, and paraplegia secondary to the bone or spinal cord involvement. There had been instances of TB spine presenting directly as abdominal pain due to psoas abscesses. Herein, we report a very rare clinical manifestation of TB spine as referred pain in the right upper abdominal quadrant due to right epidural phlegmon associated with T7 vertebra, detected by positron emission tomography.

Positron emission tomography-magnetic resonance imaging as a research tool in musculoskeletal conditions

Compared to positron emission tomography/computed tomography (PET/CT), the uptake of PET- magnetic resonance imaging (MRI) has been slow, even more so in clinical practice compared to the (pre-)clinical research setting. However, for applications in musculoskeletal (MSK) research, the combination of PET and MRI into a single modality offers attractive advantages over other imaging modalities. Most importantly, MRI has exquisite soft-tissue detail without the use of contrast agents or ionizing radiation, superior bone marrow visualization, and an extensive spectrum of distinct multiparametric assessment methods. In the preclinical setting, the introduction of PET inserts for small-animal MRI machines has proven to be a successful concept in bringing this technology to the lab. Initial hurdles in quantification have been mainly overcome in this setting. In parallel, a promising range of radiochemistry techniques has been developed to create multimodality probes that offer the possibility of simultaneously querying different metabolic pathways. Not only will these applications help in elucidating disease mechanisms, but they can also facilitate drug development. The clinical applications of PET/MRI in MSK are still limited, but encouraging initial results with novel radiotracers suggest a high potential for use in various MSK conditions, including osteoarthritis, rheumatoid arthritis, ankylosing spondylitis and inflammation and infection. Further innovations will be required to bring down the cost of PET/MRI to justify a broader clinical implementation, and remaining issues with quality control and standardization also need to be addressed. Nevertheless, PET/MRI is a powerful platform for MSK research with distinct qualities that are not offered by other techniques.

Pyogenic and Non-Pyogenic Spinal Infections: Diagnosis and Treatment

Spinal infection (SI) is an infection of vertebral bodies, intervening disc, and/or adjoining para-spinal tissue. It represents less than 10 % of all skeletal infections. There are numerous factors that predispose to developing a SI. Due to the low specificity of signs, delayed diagnosis is common. Hence, SI may be associated with poor outcomes. Diagnosis of SI must be supported by clinicopathological and radiological findings. MRI is a reliable modality of choice. Treatment options vary according to the site of the infection, disease progression, neurology, presence of instability, and general condition of the subject. Conservative treatment (orthosis/ bed-rest + antibiotics) is recommended during the early course with no/ lesser degree of neurological involvement and to medically unfit patients. Nevertheless, when conservative measures alone fail, surgical interventions must be considered. The use of concomitant antimicrobial drugs intravenously during initial duration followed by oral administration is a necessity. Controversies exist regarding the optimal duration of antimicrobial therapy, yet never given less than six weeks. Heterogeneity in clinical picture and associated co-morbidities with a range of treatment modalities are available; however, a common applicable guideline for SI does not exist. Managing SI must be tailored on a case-to-case basis.

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.

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

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.

Incremental value of FDG-PET/CT to monitor treatment response in infectious spondylodiscitis

OBJECTIVE

To assess the added value of serial 2-deoxy-2-[18F]fluoro-D-glucose (FDG) uptake analysis in predicting clinical response to treatment in infectious spondylodiscitis (IS). We sought to analyze changes in quantitative FDG-PET/CT parameters among patients with clinical response or treatment failure and to compare the sensitivity and specificity of serial FDG-PET/CT and MRI in predicting treatment response in IS.

MATERIALS AND METHODS

This retrospective study consisted of 68 FDG-PET/CT examinations in 34 patients performed before and after at least 2 weeks of antibiotic treatment. Serial MRI scans were available in 32 (94%) patients before and after treatment. FDG-avid lesions were quantified as maximum standardized uptake value (SUV_max), partial-volume corrected lesion metabolic volume (LMV), and partial-volume corrected lesion metabolic activity (LMA).

RESULTS

All FDG-PET/CT parameters significantly decreased in patients with clinical improvement (31/34, 91%, P < 0.001), while patients with disease progression did not show FDG-PET/CT improvement. FDG uptake decrease was similar between patients undergoing early assessment (< 6 weeks) compared with those performing FDG-PET/CT after 6 weeks of treatment. SUV_max, LMV, and LMA decrease over time was 39.0%, 97.4%, and 97.1%, respectively. In predicting clinical responses, SUV_max reduction > 15% and > 25% showed 94% and 89% sensitivity and 67% and 100% specificity compared with 37% and 50% of MRI, respectively. Low degree of agreement with clinical response was shown for MRI compared with FDG-PET/CT parameters using the Cohen kappa coefficient.

CONCLUSIONS

FDG-PET/CT monitoring is a valuable tool to predict clinical response to treatment in IS and has greater sensitivity and specificity compared with MRI.

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.

Comparison of the Diagnostic Value of MRI and Whole Body 18F-FDG PET/CT in Diagnosis of Spondylodiscitis

Spondylodiscitis is a spine infection for which a diagnosis by a magnetic resonance imaging (MRI) is considered the most appropriate imaging technique. The aim of this study was to compare the role of an ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) and an MRI in this field. For 56 patients with suspected spondylodiscitis for whom MRI and ¹⁸F-FDG PET/CT were performed, we retrospectively analyzed the results. Cohen’s κ was applied to evaluate the agreement between the two techniques in all patients and in subgroups with a different number of spinal districts analyzed by the MRI. Sensitivity, specificity, and accuracy were also evaluated. The agreements of the ¹⁸F-FDG PET/CT and MRI in the evaluation of the entire population, whole-spine MRI, and two-districts MRI were moderate (κ = 0.456, κ = 0.432, and κ = 0.429, respectively). In patients for whom one-district MRI was performed, ¹⁸F-FDG PET/CT and MRI were both positive and completely concordant (κ = 1). We also separately evaluated patients with suspected spondylodiscitis caused by Mycobacterium tuberculosis for whom the MRI and ¹⁸F-FDG PET/CT were always concordant excepting in 2 of the 18 (11%) patients. Sensitivity, specificity, and accuracy of the MRI and ¹⁸F-FDG PET/CT were 100%, 60%, 97%, and 92%, 100%, and 94%, respectively. Our results confirmed the ¹⁸F-FDG PET/CT diagnostic value in the diagnosis of spondylodiscitis is comparable to that of MRI for the entire spine evaluation. This could be considered a complementary technique or a valid alternative to MRI.

Clinical usefulness of FDG-PET/CT for identification of abnormal extra-cardiac foci in patients with infective endocarditis

The aim of the study was to evaluate the ability to detect extra-cardiac foci by means of whole-body ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) in patients with definite endocarditis (IE) according to the modified Duke criteria and investigate the clinical impact of the findings. From January 2011 to December 2015 we included 178 patients (mean age 66 ± 14 years, 25% female) with IE in this multicentre study. FDG-PET/CT was part of the work-up for extra-cardiac foci in the including hospitals and was performed at a median of 9 days (IQR 10) after IE was diagnosed. In 114 patients FDG-PET/CT identified 166 lesions: 52 (31%) infectious lesions, 21 (13%) cases of cancer, 7 (4%) cases of embolism, 60 (36%) reactive findings, and 26 (16%) other types of lesions. A total of 74 new extra-cardiac findings, not previously discovered by other modalities, were identified in 62 patients and resulted in additional investigations in 29 patients and a change in treatment in 18 patients (10%). The most frequent diagnoses discovered by FDG-PET/CT were colon polyps, cancer, and spondylodiscitis. There was a higher rate of findings leading to a change in treatment in patients above 67 years of age infected with other bacterial aetiologies than streptococci. FDG-PET/CT was useful to detect extra-cardiac foci. FDG-PET/CT findings may lead to unnecessary investigations. One out of 10 the patients with definite endocarditis had underwent a change in treatment regimen based on the FDG-PET/CT findings.

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.

Joint EANM/ESNR and ESCMID-endorsed consensus document for the diagnosis of spine infection (spondylodiscitis) in adults

PURPOSE

Diagnosis of spondylodiscitis (SD) may be challenging due to the nonspecific clinical and laboratory findings and the need to perform various diagnostic tests including serologic, imaging, and microbiological examinations. Homogeneous management of SD diagnosis through international, multidisciplinary guidance would improve the sensitivity of diagnosis and lead to better patient outcome.

METHODS

An expert specialist team, comprising nuclear medicine physicians appointed by the European Association of Nuclear Medicine (EANM), neuroradiologists appointed by the European Society of Neuroradiology (ESNR), and infectious diseases specialists appointed by the European Society of Clinical Microbiology and Infectious Diseases (ESCMID), reviewed the literature from January 2006 to December 2015 and proposed 20 consensus statements in answer to clinical questions regarding SD diagnosis. The statements were graded by level of evidence level according to the 2011 Oxford Centre for Evidence-based Medicine criteria and included in this consensus document for the diagnosis of SD in adults. The consensus statements are the result of literature review according to PICO (P:population/patients, I:intervention/indicator, C:comparator/control, O:outcome) criteria. Evidence-based recommendations on the management of adult patients with SD, with particular attention to radiologic and nuclear medicine diagnosis, were proposed after a systematic review of the literature in the areas of nuclear medicine, radiology, infectious diseases, and microbiology.

RESULTS

A diagnostic flow chart was developed based on the 20 consensus statements, scored by level of evidence according to the Oxford Centre for Evidence-based Medicine criteria.

CONCLUSIONS

This consensus document was developed with a final diagnostic flow chart for SD diagnosis as an aid for professionals in many fields, especially nuclear medicine physicians, radiologists, and orthopaedic and infectious diseases specialists.

Comparing the Diagnostic Accuracies of F-18 Fluorodeoxyglucose Positron Emission Tomography and Magnetic Resonance Imaging for the Detection of Spondylodiscitis: A Meta-analysis

STUDY DESIGN

A meta-analysis.

OBJECTIVE

The aim of this study was to compare the diagnostic accuracies of F-18 fluorodeoxyglucose (F-18 FDG) positron emission tomography (PET) and magnetic resonance imaging (MRI) for the detection of spondylodiscitis through a meta-analysis.

SUMMARY OF BACKGROUND DATA

There is no meta-analysis study that compares the diagnostic accuracies of F-18 FDG PET and MRI for the detection of spondylodiscitis.

METHODS

The MEDLINE and EMBASE databases were searched from the earliest available date of indexing to January 10, 2018 for studies comparing the diagnostic performance F-18 FDG PET with that of MRI for the detection of spondylodiscitis. We determined the sensitivities and specificities across studies, calculated the positive and negative likelihood ratios (LR+ and LR-), and constructed the summary receiver operating characteristic curves.

RESULTS

In the seven studies (212 patients) selected, the pooled sensitivity and specificity of F-18 FDG PET were 0.95 (95% confidence interval [CI]: 0.87-0.98) and 0.88 (95% CI: 0.73-0.95), respectively. The LR syntheses showed an overall LR+ of 7.6 (95% CI: 3.4-17.2) and LR- of 0.05 (95% CI: 0.02-0.14). The pooled diagnostic odds ratio was 141 (95% CI: 44-444). The pooled sensitivity and specificity of MRI were 0.85 (95% CI: 0.65-0.95) and 0.66 (95% CI: 0.48-0.80), respectively. The LR syntheses showed an overall LR+ of 2.5 (95% CI: 1.5-4.2) and LR- of 0.22 (95% CI: 0.08-0.60). The pooled diagnostic odds ratio was 11 (95% CI: 3-42). In the meta-regression analysis, no variable was identified as the source of the study heterogeneity.

CONCLUSION

The current meta-analysis shows that F-18 FDG PET has better diagnostic accuracy than MRI for the detection of spondylodiscitis. Further large multicenter studies would be necessary to substantiate the diagnostic accuracies of F-18 FDG PET and MRI for spondylodiscitis.

LEVEL OF EVIDENCE

2.

Added value of [18F]fluorodeoxyglucose positron emission tomography/computed tomography for the diagnosis of post-operative instrumented spine infection

PURPOSE

Post-operative instrumented spine infection (PISI) is an infrequent complication. Diagnosis of spinal implant infection can be difficult, especially in case of chronic infection.

METHODS

This retrospective study attempts to evaluate the diagnostic performance of [¹⁸F]fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) in PISI. Imagings were performed between April 2010 and June 2018 among patients referred for suspected chronic spinal implant infection. PET/CT were performed more than 12 weeks after surgery. PET/CT images were re-interpreted independently by two nuclear medicine physicians without knowledge of the patient's conditions. PET/CT data were analyzed both visually and semi-quantitatively (SUV_max). MRI results were collected from medical records. The final diagnosis of infection was based on bacteriological cultures or a twelve-month follow-up.

RESULTS

Forty-nine PET/CT were performed in 44 patients (22 women, median age 65.0 years). Twenty-two patients had a diagnosis of infection during follow-up. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for PET/CT were 86.4%, 81.5%, 79.2%, and 88.0%. Sensitivity, specificity, PPV and NPV were 66.7%, 75.0%, 66.0%, 75.0% respectively for MRI and 50.0%, 92.6%, 84.6% and 69.4% for serum C-reactive protein (CRP). Although these values were higher for PET/CT than for MRI or CRP, the differences were not statistically significant. In this setting, false positives with PET/CT can be observed in case of previous spine infection or adjacent segments disc disease. False negatives can result of extensive instrumented arthrodesis or infection with low virulence bacteria.

CONCLUSION

PET/CT is useful for the diagnosis of PISI. These results should be evaluated in further prospective study.

Diagnostic value of FDG-PET versus magnetic resonance imaging for detecting spondylitis: a systematic review and meta-analysis

BACKGROUND CONTEXT

Spondylitis is a rare infection in bone requiring multiple diagnostic strategies for verification.

PURPOSE

This study aimed to compare the diagnostic values of ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET) and magnetic resonance imaging (MRI) in detecting spondylitis.

METHODS

Online PubMed, Embase, and Cochrane Library databases were systematically searched through September 2017 for studies comparing the diagnostic values of ¹⁸F-FDG-PET and MRI. The summary sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and summary receiver operating characteristic (SROC) curve were calculated using Stata software. The ratio of these indexes between ¹⁸F-FDG-PET and MRI was also determined.

RESULTS

The summary results for ¹⁸F-FDG-PET were as follows: sensitivity=0.96 [95% confidence intervals (CI), 0.84-0.99]; specificity=0.90 (95% CI, 0.79-0.96); PLR=9.83 (95% CI, 4.39-22.03); NLR=0.05 (95% CI, 0.01-0.19); DOR=124.08 (95% CI, 39.04-394.34); and area under the SROC=0.97 (95% CI, 0.95-0.98). The summary sensitivity, specificity, PLR, NLR, DOR, and area under the SROC for MRI were 0.76 (95% CI, 0.65-0.84), 0.62 (95% CI, 0.45-0.77), 2.01 (95% CI, 1.36-2.98), 0.39 (95% CI, 0.27-0.56), 5.08 (95% CI, 2.66-9.69), and 0.77 (95% CI, 0.73-0.80), respectively. The summary results of sensitivity (p=.034), specificity (p=.006), PLR (p<.001), DOR (p<.001), and area under the SROC (p<.001) were higher in ¹⁸F-FDG-PET than in MRI. However, NLR (p=.003) was lower in ¹⁸F-FDG-PET than in MRI.

CONCLUSIONS

¹⁸F-FDG-PET had a higher diagnostic value compared with MRI in detecting spondylitis.

Clinical indications, image acquisition and data interpretation for white blood cells and anti-granulocyte monoclonal antibody scintigraphy: an EANM procedural guideline

INTRODUCTION

Radiolabelled autologous white blood cells (WBC) scintigraphy is being standardized all over the world to ensure high quality, specificity and reproducibility. Similarly, in many European countries radiolabelled anti-granulocyte antibodies (anti-G-mAb) are used instead of WBC with high diagnostic accuracy. The EANM Inflammation & Infection Committee is deeply involved in this process of standardization as a primary goal of the group.

AIM

The main aim of this guideline is to support and promote good clinical practice despite the complex environment of a national health care system with its ethical, economic and legal aspects that must also be taken into consideration.

METHOD

After the standardization of the WBC labelling procedure (already published), a group of experts from the EANM Infection & Inflammation Committee developed and validated these guidelines based on published evidences.

RESULTS

Here we describe image acquisition protocols, image display procedures and image analyses as well as image interpretation criteria for the use of radiolabelled WBC and monoclonal antigranulocyte antibodies. Clinical application for WBC and anti-G-mAb scintigraphy is also described.

CONCLUSIONS

These guidelines should be applied by all nuclear medicine centers in favor of a highly reproducible standardized practice.

Bone SPECT/CT in Postoperative Spine

Back pain is a common problem and the diagnosis and treatment depend on the clinical presentation, yet overlap between pain syndromes is common. Imaging of patients with chronic back pain in both pre- and postoperative scenarios include radiological, radionuclide, and hybrid techniques. In general, these techniques have their own advantages and limitations. The aim of surgery is to eliminate pathologic segmental motion and accompanying symptoms, especially pain. However, surgical procedures are not without complications and localizing the cause of the pain is often challenging. Radiobisphosphonate bone SPECT/CT is reported to be useful in evaluating benign orthopedic conditions and it often provides valuable information such as accurate localization and characterization of bone abnormalities. In this review, routinely used spinal surgical techniques and procedures are discussed, as well as the acute and delayed complications related to spinal surgery, the role of conventional imaging, and the potential uses of radionuclide bone SPECT/CT to diagnose pseudoarthrosis, cage subsidence, loosening and misalignment, hardware failure, and postoperative infection.

Spondylodiscitis in Paediatric Patients: The Importance of Early Diagnosis and Prolonged Therapy

Background: Spondylodiscitis (SD), the concurrent infection of a vertebral disc and the adjacent vertebral bodies, is a very severe disease that can lead to death or cause spinal deformities, segmental instabilities, and chronic pain, which significantly reduces the quality of life for affected patients. Early diagnosis and treatment are essential in order to reduce the risk of negative outcomes. The two cases of SD that are described in this paper might be useful for informing paediatric approaches to children with SD. Case presentation: The cases that are reported here are about two children of approximately 2 and 3 years of age, in whom SD involving the L4⁻L5 and L3⁻L4 interspaces, had a subacute or chronic course. The clinical manifestations were mild, fever was absent, and the lumbar pain lasted for a long time and was the predominant symptom. Moreover, laboratory tests were in the normal range or only slightly abnormal, as were the standard radiographs of the lumbar spine. In both of the cases, SD confirmation was obtained through magnetic resonance imaging (MRI) and MRI was also used to evaluate the response to therapy. In both of our patients, tuberculosis was excluded based on tuberculin skin testing and the Quantiferon TBgold tests being negative. This finding led to the prescription of a broad-spectrum antibiotic therapy, including a drug that was potentially effective against Staphylococcus aureus (Sa). The strict monitoring of the spinal damage with MRI avoided the need for aspirations or biopsies; invasive procedures that are ethically acceptable in pediatric age only in a few selected cases, when the empirical antibiotic is associated with a worsening of spinal damage; or the vertebral osteomyelitis lesion mimics a tumoral lesion. Conclusions: Although rare, SD represents an important disease in children. In toddlers and preschool children, it can have a subacute or chronic course, in which only back pain, irritability, and walking difficulties are the signs and symptoms of the disease. MRI remains the best method for confirming the diagnosis and for evaluating therapy efficacy. Antibiotics are the drugs of choice. Although the duration has not been established, antibiotics should be administered for several weeks.

Imaging of Spondylodiscitis

Spondylodiscitis is an infection of the vertebral body or disc and may also involve the epidural space, posterior elements, and paraspinal soft tissues. It is a cause of morbidity and mortality, and warrants early diagnosis and prompt treatment. Diagnosis can be difficult because of nonspecific signs and symptoms. Magnetic resonance imaging is sensitive and specific and is the imaging modality of choice for spondylodiscitis. Gadolinium contrast can show the extent of soft tissue and bone phlegmon and abscess. The test is less useful for evaluating treatment response. When magnetic resonance imaging cannot be performed or is not diagnostic, radionuclide imaging is a useful alternative. Although bone scintigraphy frequently is used as a screening test, false-negative results can occur, especially in the elderly. This test is not useful for detecting soft tissue infections that accompany or mimic spondylodiscitis. Gallium-67 citrate improves the specificity of the bone scan, can detect infection earlier than the bone scan, may be more sensitive, especially in elderly patients, and identifies accompanying soft tissue infection. Performing SPECT and SPECT/CT improves accuracy. The 2- to 3-day delay between radiopharmaceutical administration and the relatively poor image quality are significant disadvantages of gallium-67. Indium-111 biotin, alone or in combination with streptavidin, accurately diagnoses spondylodiscitis; unfortunately, this agent is not widely available. Currently, ¹⁸F-FDG imaging is the radionuclide test of choice for spondylodiscitis. The procedure, which is completed in a single session, is sensitive, has a high negative predictive value, and reliably differentiates degenerative from infectious vertebral body end plate abnormalities. In comparative investigations, ¹⁸F-FDG has outperformed bone and gallium-67 imaging. Preliminary data suggest that ¹⁸F-FDG may be able to provide an objective means to measure response to treatment. Gallium-68 citrate and 99mTc-radiolabeled antimicrobial peptides have been investigated, but their role in spondylodiscitis has yet to be established.

Diagnostic challenges in pyogenic spinal infection: an expanded role for FDG-PET/CT

In a preliminary investigation of FDG-PET/CT for assessment of therapy response of pyogenic spine infection, it was concluded that activity confined to the margins of a destroyed or degenerated joint with bone-on-bone contact represents nonseptic inflammation, regardless of the intensity of uptake. Only activity in bone, soft tissue, or within the epidural space represents active infection. The purpose of this investigation was to assess the performance of these pattern-based interpretation criteria in a series of problem cases of proven or suspected spine infection. Eighty-two FDG-PET/CTs were done for initial diagnosis because other imaging failed to provide a definitive diagnosis and 147 FDG-PET/CTs were done to assess treatment responses. Pattern-based interpretations were compared with the clinical diagnosis based on bacterial cultures and outcomes after cessation or withholding of antibiotic therapy. Pattern-based interpretation criteria achieved a sensitivity and specificity of 98 and 100%, respectively, for initial diagnosis and a specificity of 100% for assessment of treatment response. The same data was analyzed using intensity of activity as the primary factor. Sensitivity and specificity using the intensity-based criteria were 93 and 68%, respectively, for initial diagnosis, and the specificity of a negative interpretation for therapy response was 55%. Differences from pattern-based criteria are highly significant. Pattern-based criteria perform well in problem cases with equivocal MR and for treatment response because they correctly eliminate activity from nonspecific inflammation associated with destroyed joints with bone-on-bone contact. Response occurs within a timeframe that is useful for managing antibiotic therapy.

Spondylodiscitis following endovascular abdominal aortic aneurysm repair: imaging perspectives from a single centre's experience

OBJECTIVE

Very few reports have previously described spondylodiscitis as a potential complication of endovascular aortic aneurysm repair (EVAR). We present to our knowledge the first case series of spondylodiscitis following EVAR based on our institution's experience over an 11-year period. Particular attention is paid to the key imaging features and challenges encountered when performing spinal imaging in this complex patient group.

MATERIALS AND METHODS

Of 1,847 patients who underwent EVAR at our institution between January 2006 and January 2017, a total of 9 patients were identified with imaging features of spondylodiscitis (0.5%). All cross-sectional studies before and after EVAR were assessed by a Consultant Musculoskeletal Radiologist and a Musculoskeletal Radiology Fellow to evaluate for features of spondylodiscitis.

RESULTS

All 9 patients had single-level spondylodiscitis involving lumbosacral levels adjacent to the aortic/iliac stent graft. Eight out of nine patients had an extensive anterior paravertebral phlegmon/abscess that was contiguous with the infected stent graft and native aneurysm sac ± anterior vertebral body erosion. Epidural disease was present in only 3 out of 9 patients and was a minor feature. MRI was non-diagnostic in 3 out of 9 patients owing to susceptibility artefact. ¹⁸F-FDG PET/CT accurately depicted the spinal level involved and adjacent paravertebral disease in patients with non-diagnostic MRI and was adopted as the follow-up modality in 3 out of 5 surviving patients.

CONCLUSION

Spondylodiscitis is a rare complication post-EVAR. Imaging features of disproportionate anterior paravertebral disease and anterior vertebral body bony involvement suggest direct spread of infection posteriorly to the adjacent vertebral column. Use of MRI versus ¹⁸F-FDG PET/CT as the optimal imaging modality should be directed by the type of stent graft deployed.

Spondylodiscitis: Diagnosis and Treatment Options

BACKGROUND

A recent population-based study from Denmark showed that the incidence of spondylodiscitis rose from 2.2 to 5.8 per 100 000 persons per year over the period 1995-2008; the age-standardized incidence in Germany has been estimated at 30 per 250 000 per year on the basis of data from the Federal Statistical Office (2015). The early diagnosis and treatment of this condition are essential to give the patient the best chance of a good outcome, but these are often delayed because it tends to present with nonspecific manifestations, and fever is often absent.

METHODS

This article is based on a systematic search of Medline and the Cochrane Library for the period January 2009 to March 2017. Of the 788 articles identified, 30 publications were considered.

RESULTS

The goals of treatment for spondylodiscitis are to eliminate infection, restore functionality of the spine, and relieve pain. Magnetic resonance imaging (MRI) remains the gold standard for the radiological demonstration of this condition, with 92% sensitivity and 96% specificity. It also enables visualization of the spatial extent of the infection and of abscess formation (if present). The most common bacterial cause of spondylodiscitis in Europe is Staphylococcus aureus, but tuberculous spondylodiscitis is the most common type worldwide. Antibiotic therapy is a pillar of treatment for spondylodiscitis and should be a part of the treatment in all cases. Neurologic deficits, sepsis, an intraspinal empyema, the failure of conservative treatment, and spinal instability are all indications for surgical treatment.

CONCLUSION

The quality of life of patients who have been appropriately treated for spondylodiscitis has been found to be highly satisfactory in general, although back pain often persists. The risk of recurrence increases in the presence of accompanying illnesses such as diabetes mellitus, renal failure, or undrained epidural abscesses.

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

Purpose

The aim of this study was to determine the diagnostic value of ¹⁸F–fluorodeoxyglucose (FDG) positron emission tomography and computed tomography (PET/CT) and magnetic resonance imaging (MRI) in diagnosing vertebral osteomyelitis.

Methods

From November 2015 until December 2016, 32 patients with suspected vertebral osteomyelitis were prospectively included. All patients underwent both ¹⁸F–FDG-PET/CT and MRI within 48 h. All images were independently reevaluated by two radiologists and two nuclear medicine physicians who were blinded to each others’ image interpretation. ¹⁸F–FDG-PET/CT and MRI were compared to the clinical diagnosis according to international guidelines.

Results

For ¹⁸F–FDG-PET/CT, sensitivity, specificity, PPV, and NPV in diagnosing vertebral osteomyelitis were 100%, 83.3%, 90.9%, and 100%, respectively. For MRI, sensitivity, specificity, PPV, and NPV were 100%, 91.7%, 95.2%, and 100%, respectively. MRI detected more epidural/spinal abscesses. An important advantage of ¹⁸F–FDG-PET/CT is the detection of metastatic infection (16 patients, 50.0%).

Conclusion

¹⁸F–FDG-PET/CT and MRI are both necessary techniques in diagnosing vertebral osteomyelitis. An important advantage of ¹⁸F–FDG-PET/CT is the visualization of metastatic infection, especially in patients with bacteremia. MRI is more sensitive in detection of small epidural abscesses.

Recurrent surgical site infection of the spine diagnosed by dual (18)F-NaF-bone PET/CT with early-phase scan

We report a case of a 31-year-old man who showed recurrently elevated level of the serum inflammatory marker C-reactive protein (CRP) after spinal operation. He underwent (18)F-flurodeoxyglucose ((18)F-FDG) positron emission tomography/computed tomography (PET/CT) and dual (18)F-sodium-fluoride ((18)F-NaF) PET/CT with an additional early-phase scan to find a hidden inflammation focus. Only mildly increased (18)F-FDG was found at the surgical site of T11 spine on (18)F-FDG PET/CT. In contrast, dual (18)F-NaF bone PET/CT with early-phase scan demonstrated focal active inflammation at the surgical site of T11 spine. After a revision operation of the T11 spine, serum CRP level decreased to the normal range without any symptom or sign of inflammation. Inflammatory focus in the surgical site of the spine can be detected with using dual (18)F-NaF bone PET/CT scan with early-phase scan.

Radionuclide Imaging of Musculoskeletal Infection: A Review

There are numerous imaging tests for diagnosing musculoskeletal infection. Radiographs are routinely performed, because even when not diagnostic, they provide an anatomic overview of the region of interest that could influence subsequent procedure selection and interpretation. MRI is sensitive and provides superb anatomic detail. Bone scintigraphy accurately diagnoses osteomyelitis in bones not affected by underlying conditions. (67)Ga is used primarily for spondylodiskitis. Although in vitro labeled leukocyte imaging is the radionuclide test of choice for complicating osteomyelitis such as diabetic pedal osteomyelitis and prosthetic joint infection, it is not useful for spondylodiskitis. Antigranulocyte antibodies and antibody fragments have limitations and are not widely available. (111)In-biotin is useful for spondylodiskitis. Radiolabeled synthetic fragments of the antimicrobial peptide ubiquicidin are promising infection-specific agents. (18)F-FDG is the radiopharmaceutical of choice for spondylodiskitis. Its role in diabetic pedal osteomyelitis and prosthetic joint infection is not established. Preliminary data suggest (68)Ga may be useful in musculoskeletal infection. (124)I-fialuridine initially showed promise as an infection-specific radiopharmaceutical, but subsequent investigations were disappointing. The development of PET/CT and SPECT/CT imaging systems, which combine anatomic and functional imaging, has revolutionized diagnostic imaging. These hybrid systems are redefining the diagnostic workup of patients with suspected or known infection and inflammation by improving diagnostic accuracy and influencing patient management.

A comparison of the diagnostic value of MRI and 18F-FDG-PET/CT in suspected spondylodiscitis

Purpose

The purpose of this study was to evaluate the diagnostic value of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography and computed tomography (PET/CT scan) and magnetic resonance imaging (MRI) in diagnosing spondylodiscitis and its complications, such as epidural and paraspinal abscesses.

Methods

From January 2006 to August 2013 patients with a clinical suspicion of spondylodiscitis, with an infection, or with fever of unknown origin were retrospectively included if ¹⁸F-FDG-PET/CT and MRI of the spine were performed within a 2-week time span. Imaging results were compared to the final clinical diagnosis and follow-up data were collected.

Results

Sixty-eight patients were included of whom 49 patients were diagnosed with spondylodiscitis. MRI showed an overall sensitivity of 67 % and specificity of 84 %. Diagnostic accuracy was 58 %, when MRI was performed within 2 weeks after the start of symptoms and improved to 82 %, when performed more than 2 weeks after onset of symptoms. ¹⁸F-FDG-PET/CT showed a sensitivity of 96 % and a specificity of 95 %, with no relation to the interval between the scan and the start of symptoms.

Conclusions

As compared to MRI, ¹⁸F-FDG-PET/CT has superior diagnostic value for detecting early spondylodiscitis. After 2 weeks both techniques perform similarly.

Use of Simultaneous 18F-FDG PET/MRI for the Detection of Spondylodiskitis

The diagnosis of spondylodiskitis is often challenging. MRI is quite sensitive but lacks specificity, and distinction from erosive osteochondritis is often difficult. We sought to assess the diagnostic value of (18)F-FDG PET combined with MRI (combined (18)F-FDG PET/MRI) in patients with suspected spondylodiskitis and an inconclusive clinical or MRI presentation.

METHODS

In a prospective study, 30 patients with previous inconclusive MRI results and suspected spondylodiskitis underwent combined (18)F-FDG PET/MRI, including precontrast and postcontrast standard spine MRI sequences. The image datasets were evaluated on dedicated workstations by 2 radiology residents and 1 board-certified nuclear medicine physician independently and then in consensus. Because of severe susceptibility artifacts, only 28 of 30 image datasets were evaluable, with a total of 29 regions of suspected spondylodiskitis. SUV ratios (affected disk/reference disk) were determined. The imaging results were compared with histopathology or clinical follow-up as a reference standard and subjected to statistical analysis.

RESULTS

The reference standards identified spondylodiskitis in 12 disks and excluded spondylodiskitis in 17 disks. For MRI alone, the sensitivity was 50%, the specificity was 71%, the positive predictive value was 54%, and the negative predictive value was 67%. Adding the PET data resulted in sensitivity, specificity, positive predictive value, and negative predictive value of 100%, 88%, 86%, and 100%, respectively. In a receiver operating characteristic curve analysis, an SUVmax ratio threshold of 2.1 resulted in 92% sensitivity and 88% specificity (area under the receiver operating characteristic curve, 0.95). Neither the level of C-reactive protein nor the leukocyte count at the time of PET/MRI was related to the reference standard diagnosis of spondylodiskitis.

CONCLUSION

In patients with inconclusive clinical or MRI findings, the use of (18)F-FDG PET/MRI significantly increased diagnostic certainty for the detection of spondylodiskitis.

Infectious Discitis and Spondylodiscitis in Children

In children, infectious discitis (D) and infectious spondylodiscitis (SD) are rare diseases that can cause significant clinical problems, including spinal deformities and segmental instabilities. Moreover, when the infection spreads into the spinal channel, D and SD can cause devastating neurologic complications. Early diagnosis and treatment may reduce these risks. The main aim of this paper is to discuss recent concepts regarding the epidemiology, microbiology, clinical presentation, diagnosis, and treatment of pediatric D and SD. It is highlighted that particular attention must be paid to the identification of the causative infectious agent and its sensitivity to antibiotics, remembering that traditional culture frequently leads to negative results and modern molecular methods can significantly increase the detection rate. Several different bacterial pathogens can cause D and SD, and, in some cases, particularly those due to Staphylococcus aureus, Kingella kingae, Mycobacterium tuberculosis, Brucella spp., the appropriate choice of drug is critical to achieve cure.

Diagnostic value of F-18 FDG PET/CT in patients with spondylodiscitis: Is dual time point imaging time worthy?

PURPOSE

In this retrospective study, we aimed to investigate the value of FDG-PET/CT in the diagnosis of spondylodiscitis (SD), the significance of dual time point imaging (DTPI) for SD diagnosis and the worth of SUVmax data for distinguishing tuberculous vs. non-tuberculous SD.

MATERIALS AND METHODS

32 patients with suspected SD were scanned with FDG-PET/CT. For quantitative analysis maximum standardized uptake value (SUVmax) of the lesion area was measured. Nineteen patients had DTPI of FDG-PET/CT. The final diagnoses were achieved by histopathological, microbiological, and clinical results.

RESULTS

Specific pathogens were isolated in 21 patients; other patients were accepted as nonspecific bacterial SD. In all patients, FDG-PET/CT results were compatible with SD diagnosis. The SUVmax data for tuberculous and non-tuberculous SD and DTPI results were statistically insignificant.

CONCLUSION

FDG-PET/CT is a successful modality for SD diagnosis; additionally, DTPI protocol for FDG-PET/CT in SD diagnosis and SUVmax data for differentiation between non-tbc SD and tbc SD are useless.

PET/CT imaging of Mycobacterium tuberculosis infection

Tuberculosis has a high morbidity and mortality worldwide. Mycobacterium tuberculosis (Mtb) has a complex pathophysiology; it is an aerobic bacillus capable of surviving in anaerobic conditions in a latent state for a very long time before reactivation to active disease. In the latent tuberculosis infection, the individual has no clinical evidence of active disease, but exhibits a hypersensitive response to proteins of Mtb. Only some 5–10 % of latently infected individuals appear to have reactivation of tuberculosis at any one time point after infection, and neither imaging nor immune tests have been shown to predict tuberculosis reactivation reliably. The complex pathology of the organism provides multiple molecular targets for imaging the infection and targeting therapy. Positron emission tomography (PET) integrated with computer tomography (CT) provides a unique opportunity to noninvasively image the whole body for diagnosing, staging and assessing therapy response in many infectious and inflammatory diseases. PET/CT is a powerful noninvasive tool that can rapidly provide three-dimensional views of disease deep within the body and conduct longitudinal assessment over time in one particular patient. Some PET tracers, such as ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG), have been found to be useful in various infectious diseases for detection, assessing disease activity, staging and monitoring response to therapy. This tracer has also been used for imaging tuberculosis. ¹⁸F-FDG PET relies on the glucose uptake of inflammatory cells as a result of the respiratory burst that occurs with infection. Other PET tracers have also been used to image different aspects of the pathology or microbiology of Mtb. The synthesis of the complex cell membrane of the bacilli for example can be imaged with ¹¹C-choline or ¹⁸F-fluoroethylcholine PET/CT while the uptake of amino acids during cell growth can be imaged by 3′-deoxy-3′-[¹⁸F]fluoro-l-thymidine. PET/CT provides a noninvasive and sensitive method of assessing histopathological information on different aspects of tuberculosis and is already playing a role in the management of tuberculosis. As our understanding of the pathophysiology of tuberculosis increases, the role of PET/CT in the management of this disease would become more important. In this review, we highlight the various tracers that have been used in tuberculosis and explain the underlying mechanisms for their use.

Interest of [(18)F]fluorodeoxyglucose positron emission tomography/computed tomography for the diagnosis of relapse in patients with spinal infection: a prospective study

Relapse after treatment of a spinal infection is infrequent and difficult to diagnose. The aim of this study was to assess the diagnostic performance of [(18)F]fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) in this setting. Thirty patients (21 men, nine women; median age 61.2 years) with a suspected spinal infection relapse were prospectively included between March 2010 and June 2013. The initial diagnosis of spinal infection was confirmed by positive bacterial cultures. The patients underwent [(18)F]FDG PET/CT and magnetic resonance imaging (MRI) 1 month after antibiotic treatment interruption. PET/CT data were interpreted both visually and semi-quantitatively (SUVmax). The patients were followed for ≥12 months and the final diagnosis of relapse was based on new microbiological cultures. Seven patients relapsed during follow up. Sensitivity, specificity, positive predictive value and negative predictive value were 66.6%, 61.9%, 33.3% and 86.6%, respectively for MRI and 85.7, 82.6, 60.0 and 95.0 for PET/CT. Although these values were higher for PET/CT than for MRI, the difference was not statistically significant (p=0.3). [(18)F]FDG PET/CT may be useful for diagnosing a relapse of spinal infections, in particular if metallic implants limit the performance of MRI.

Infections of the spine and spinal cord

Predisposing factors for developing spinal infections include: immunodeficiency; drug abuse; the widespread use of broad-spectrum antibiotics, corticosteroids, and immunosuppressive drugs; diabetes mellitus; and spinal surgery. Infections can be bacterial, fungal, parasitic, or viral in origin. This chapter reviews current knowledge in clinical and imaging findings in the most common spinal infections divided according to the compartment primarily involved.