Expanding role of 18F-fluoro-D-deoxyglucose PET and PET/CT in spinal infections

Imaging protocols for non-traumatic spinal cord injury: current state of the art and future directions

INTRODUCTION

Non-traumatic spinal cord injury (NTSCI) is a term used to describe damage to the spinal cord from sources other than trauma. Neuroimaging techniques such as computerized tomography (CT) and magnetic resonance imaging (MRI) have improved our ability to diagnose and manage NTSCIs. Several practice guidelines utilize MRI in the diagnostic evaluation of traumatic and non-traumatic SCI to direct surgical intervention.

AREAS COVERED

The authors review practices surrounding the imaging of various causes of NTSCI as well as recent advances and future directions for the use of novel imaging modalities in this realm. The authors also present discussions around the use of simple radiographs and advanced MRI modalities in clinical settings, and briefly highlight areas of active research that seek to advance our understanding and improve patient care.

EXPERT OPINION

Although several obstacles must be overcome, it appears highly likely that novel quantitative imaging features and advancements in artificial intelligence (AI) as well as machine learning (ML) will revolutionize degenerative cervical myelopathy (DCM) care by providing earlier diagnosis, accurate localization, monitoring for deterioration and neurological recovery, outcome prediction, and standardized practice. Some intriguing findings in these areas have been published, including the identification of possible serum and cerebrospinal fluid biomarkers, which are currently in the early phases of translation.

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.

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.

18F-NaF PET/CT in Presumed Aseptic Pseudarthrosis after Spinal Fusion: Correlation with Findings at Revision Surgery and Intraoperative Cultures

Background Conventional imaging is useful to assess interbody fusion by showing complete trabecular bony bridging, but has a low positive predictive value for pseudarthrosis. Because alterations of bone metabolism may precede structural anatomical changes on computed tomography (CT), we aimed to investigate the ability of fluorine 18 sodium fluoride positron emission tomography/computed tomography (18F-NaF PET/CT) to identify pseudarthrosis after spinal fusion using surgical revision as the reference standard.

Methods We retrospectively reviewed 18F-NaF PET/CT scans performed between February 2019 and September 2020 in patients experiencing pain after spinal fusion. We included the 18 patients who underwent revision surgery for suspicion of pseudarthrosis. Five consecutive patients who were clearly fused on CT served as the control group.

Results In the revision surgery group (n=18), visual assessment by 18F-NaF PET/CT revealed that all 22 cages with an increased 18F-NaF uptake around intercorporal fusion material had mobility at revision surgery, whereas none of the fused patients (n=5) showed uptake around cage/intervertebral disk space. Among the 18 patients with presumed aseptic pseudarthrosis, intraoperative cultures revealed surgical site infection (SSI) caused by Cutibacterium acnes (C. acnes) in seven patients (38.9%). There was a statistically significant difference in standardized uptake values and uptake ratios between the revision surgery and control groups (p=5.3× 10−6 and p=0.0002, respectively).

Conclusions 18F-NaF PET/CT imaging appeared as a useful tool to identify pseudarthrosis following spinal fusion. The unexpectedly high prevalence (38.9%) of SSI caused by C. acnes found in presumed aseptic patients supports the utility of intraoperative cultures in revision cases for pseudarthrosis, even without preoperative clinical suspicion of SSI.

[18F]FDG-PET Evaluation of Spinal Pathology in Patients in Oncology: Pearls and Pitfalls for the Neuroradiologist

[¹⁸F]FDG-PET is a widely used technique for specific evaluation of disease and treatment response in oncology. However, the principles behind [¹⁸F]FDG-PET imaging allow a wide-ranging array of benign and malignant pathologies to be identified on both initial and routine surveillance imaging. This is important for clinicians and radiologists, alike, in that effective and accurate evaluation of malignancy and metastatic disease, specifically involving the spine and central nervous system, is crucial. In this article, we review the normal and posttherapy appearance of the spine on [¹⁸F]FDG-PET, the various types and patterns of metastatic disease that involve the spine and spinal cord, and, finally, important spinal pathologies that may mimic malignancy on [¹⁸F]FDG-PET.

Imaging Assessment of the Postoperative Spine: An Updated Pictorial Review of Selected Complications

Imaging of the postoperative spine requires the identification of several critical points by the radiologist to be written in the medical report: condition of the underlying cortical and cancellous bone, intervertebral disc, and musculoskeletal tissues; location and integrity of surgical implants; evaluation of the success of decompression procedures; delineation of fusion status; and identification of complications. This article presents a pictorial narrative review of the most common findings observed in noninstrumented and instrumented postoperative spines. Complications in the noninstrumented spine were grouped in early (hematomas, pseudomeningocele, and postoperative spine infection) and late findings (arachnoiditis, radiculitis, recurrent disc herniation, spinal stenosis, and textiloma). Complications in the instrumented spine were also sorted in early (hardware fractures) and late findings (adjacent segment disease, hardware loosening, and implant migration). This review also includes a short description of the most used diagnostic techniques in postoperative spine imaging: plain radiography, ultrasound (US), computed tomography (CT), magnetic resonance (MR), and nuclear medicine. Imaging of the postoperative spine remained a challenging task in the early identification of complications and abnormal healing process. It is crucial to consider the advantages and disadvantages of the imaging modalities to choose those that provide more accurate spinal status information during the follow-up. Our review is directed to all health professionals dealing with the assessment and care of the postoperative spine.

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.

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.

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.

[Modern radiological diagnostics in spine surgery]

BACKGROUND

Radiological imaging is important in the preoperative diagnosis of many forms of spinal pathology and plays a fundamental role in the assessment of p.o. effects, which can be verified on the spinal column as well as on the surrounding soft tissues, depending on the imaging method used.

AIM

The article provides an overview of the current status and possibilities of radiological diagnostic methods for the verification of possibly recommended spine surgery in the context of degenerative, inflammatory-infectious, post-traumatic or p.o. pathologies and changes in the spine: X‑rays, computed tomography (CT), magnetic resonance imaging (MRI). The supplementary nuclear medicine procedures (scintigraphy, PET[-CT], SPECT, etc.) which may be required for special questions are not discussed.

MATERIAL AND METHODS

The merits and limitations of the techniques used in the investigation of advanced degenerative spinal pathologies and post-traumatic conditions are discussed, with multidetector CT being the focus of attention in spinal clearance for traumatic injuries. In most cases of spinal infection, MRI images, as a central diagnostic tool, show typical findings such as destruction of adjacent endplates, bone marrow and intervertebral disc abnormalities, and paravertebral or epidural abscesses. However, it is not always easy to diagnose a spinal infection, especially if atypical MR patterns of infectious spondylitis are present. Knowledge of them means misdiagnosis and improper treatment can be avoided.

RESULTS

It is shown that high-quality modern radiological examinations are essential for diagnosis and p.o. management, as these provide answers to the main questions in the treatment: Is the entity/injury stable or unstable, acute or old, benign or malign; is there a myelopathy or p.o. complication?

DISCUSSION

The main indications for p.o. diagnostic imaging, difficulties such as metal artefact formation, and potential pitfalls are analyzed. Entity-specific radiological image patterns, imaging algorithms and differential diagnostic peculiarities are presented and discussed based on current literature and selected case studies.

Management of spinal infection: a review of the literature

Spinal infection (SI) is defined as an infectious disease affecting the vertebral body, the intervertebral disc, and/or adjacent paraspinal tissue and represents 2–7% of all musculoskeletal infections. There are numerous factors, which may facilitate the development of SI including not only advanced patient age and comorbidities but also spinal surgery. Due to the low specificity of signs, the delay in diagnosis of SI remains an important issue and poor outcome is frequently seen. Diagnosis should always be supported by clinical, laboratory, and imaging findings, magnetic resonance imaging (MRI) remaining the most reliable method. Management of SI depends on the location of the infection (i.e., intraspinal, intervertebral, paraspinal), on the disease progression, and of course on the patient’s general condition, considering age and comorbidities. Conservative treatment mostly is reasonable in early stages with no or minor neurologic deficits and in case of severe comorbidities, which limit surgical options. Nevertheless, solely medical treatment often fails. Therefore, in case of doubt, surgical treatment should be considered. The final result in conservative as well as in surgical treatment always is bony fusion. Furthermore, both options require a concomitant antimicrobial therapy, initially applied intravenously and administered orally thereafter. The optimal duration of antibiotic therapy remains controversial, but should never undercut 6 weeks. Due to a heterogeneous and often comorbid patient population and the wide variety of treatment options, no generally applicable guidelines for SI exist and management remains a challenge. Thus, future prospective randomized trials are necessary to substantiate treatment strategies.

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.

Role of PET/CT in Workup of Fever without a Source

Fever without source is a febrile illness without localizing signs or initial obvious cause. Early workup will often include chest radiography and computed tomography (CT) of the abdomen and pelvis, with or without CT of the chest. To evaluate localizing signs or symptoms or to further evaluate findings from initial studies, targeted imaging according to body part can be performed by using radiography, ultrasonography, CT, or magnetic resonance (MR) imaging. Nuclear medicine studies can provide imaging of the whole body and may be helpful when the clinical and conventional imaging workup findings are negative or equivocal in identifying a source of fever. Nuclear medicine studies can be used to detect pathologic changes early in a disease course, even in the absence of an anatomic abnormality. Gallium 67 scintigraphy, indium 111- and technetium 99m-labeled leukocyte scintigraphy, and fluorine 18 fluorodeoxyglucose positron emission tomography (PET)/CT studies are all useful in the evaluation of fever, but the radiopharmaceutical cost for PET/CT is much lower than that for radiolabeled leukocyte studies. The increased use of bundled payments for inpatient admissions requires updated cost evaluations for the preferred nuclear medicine study. For inpatients in whom the findings from the initial clinical workup and imaging studies are nondiagnostic, PET/CT examination may be preferable to radiolabeled leukocyte studies because of its high sensitivity and lower cost. Negative findings at PET/CT can be helpful in excluding a suspected site of infection, and positive findings at PET/CT can be helpful in confirming a suspected site of infection or in identifying an unexpected cause of fever. (©)RSNA, 2016.

Multidisciplinary management of spontaneous spinal infections: is there a correlation between timing, type of treatment and outcome?

BACKGROUND

Spontaneous spinal infections (SSIs) represent a rare and serious pathological entity. We tried to study a correlation between type of treatment, timing of treatment and clinical outcome through a multivariate analysis of an observational cohort study with the aim to define what is the optimal clinico-therapeutic management.

METHODS

We performed a retrospective observational cohort study on all consecutive patients observed in our Institute in a period of 13 years; from 2001 to 2014 we enrolled 50 consecutive patients with symptomatic spontaneous spinal infections (no previous surgery or recent infection in other site), confirmed with diagnostic imaging. The inclusion parameters were: diagnostic imaging, signs and symptoms positive for SSI, no history of recent infection or surgery. Of each parameter analyzed, we calculated mean and standard deviation and when necessary correlation (ρ), covariance (σ) and relation coefficient between type of treatment, timing of treatment and clinical outcome.

RESULTS

Our results suggest that an increase of one day from the onset of symptoms and the start of therapy leads to an increase in the Oswestry Disability Index Scale both at 6 months than at 1 year, with a statistical relevance, so our experience shows a statistically significant correlation and a positive co-variance between timing and outcome at 6 months and 1 year.

CONCLUSIONS

SSI are rare, very difficult to diagnose and represent a significant clinical problem. If not properly managed, they may lead to significant impact in the quality of life. The most relevant problem is not the treatment, conservative or surgical, but early diagnosis, so a careful physical, laboratory and imaging examination is fundamental, with an important help provided by isolation of the pathogen and histology. In our experience early diagnosis has a fundamental role. In the light of this, current treatment protocols may require a prompt and multidisciplinary management including infectivologists, neuroradiologists and spine surgeons.

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.

FDG PET Assessment of Osteomyelitis: A Review

This article discusses the role of [(18)F]Fluorodeoxyglucose (FDG) PET and PET/computed tomography in diagnosis and therapeutic response assessment for the management of patients with osteomyelitis, to increase awareness of imaging pitfalls and to improve understanding of specific technical and diagnostic challenges in patients with posttraumatic chronic osteomyelitis, spinal infections, prosthetic joint infections, and diabetic foot infections. This article focuses on the usefulness of modern imaging modalities in the setting of suspected infection or inflammation and on the role of FDG-PET in the management of patients with suspected or confirmed infection in the bones.

Assessment of Therapy Response by FDG PET in Infection and Inflammation

Positron emission tomography (PET) is a well-known imaging modality in assessing the treatment response to chemotherapy or radiotherapy in various malignancies. A systematic review of the literature reveals a few publications reporting evaluation of the treatment response in benign conditions using PET/computed tomography. PET holds a promising future role in the follow-up of inflammatory or infectious diseases. In this article, [(18)F]Fluorodeoxyglucose PET as a tool in the evaluation, treatment, and follow-up of infectious and inflammatory diseases is discussed.

Efficacy of vancomycin-releasing biodegradable poly(lactide-co-glycolide) antibiotics beads for treatment of experimental bone infection due to Staphylococcus aureus

BACKGROUND

Clinical experience and animal studies have suggested that positron emission tomography (PET) using fluorine-18-labeled fluorodeoxyglucose ((18)F-FDG) may be promising for imaging of bone infections. In this study, we aimed to establish the accuracy of (18)F-FDG PET scanning for monitoring the response to poly(lactide-co-glycolide) (PLGA) vancomycin beads for treatment of bone infection.

METHODS

PLGA was mixed with vancomycin and hot-compress molded to form antibiotic beads. In vitro, elution assays and bacterial inhibition tests were employed to characterize the released antibiotics. In vivo, cylindrical cavities were made in six adult male New Zealand white rabbits, and Staphylococcus aureus or saline was injected into the cavity to create a bone infection. After 2 weeks, the infection was confirmed by bacterial cultures, and the defect was filled with PLGA vancomycin beads. The treatment response was monitored by (18)F-FDG PET.

RESULTS

The biodegradable beads released high concentrations of vancomycin (well above the breakpoint sensitivity concentration) for treatment of bone infection. In bacterial inhibition tests, the diameter of the sample inhibition zone ranged from 6.5 to 10 mm, which was equivalent to 12.5-100 % relative activity. (18)F-FDG PET results showed that uncomplicated bone healing was associated with a temporary increase in (18)F-FDG uptake at 2 weeks, with return to near baseline at 6 weeks. In the infected animals, localized infection resulted in intense continuous uptake of (18)F-FDG, which was higher than that in uncomplicated healing bones. Bone infection was confirmed with positive bacterial cultures. In vancomycin-treated animals, data showed rapidly decreasing amounts of (18)F-FDG uptake after treatment.

CONCLUSIONS

In vitro and in vivo analyses showed that the use of biodegradable PLGA vancomycin beads successfully eradicated S. aureus infection in damaged bone.

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.

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.

Quantitative in vivo fusion assessment by (18)F-fluoride PET/CT following en bloc spondylectomy

PURPOSE

The purpose of this retrospective analyses was to evaluate the bone viability in the ventral column of the spine following large segmental defect reconstructions. Osseous integration of implants following spinal fusion procedures is an essential precondition to provide adequate mechanical strength to any applied forces and subsequently satisfying patient outcomes. Although CT scan is the non-invasive gold standard for fusion assessment, it lacks the ability to visualize bone viability and, therefore, discrepancy remains about sensitivity and specificity of CT as evaluation tool of spinal fusion.

METHODS

A novel modality, (18)F Fluoride PET/CT, specifically allows quantitative in vivo evaluation of metabolic activity of the osseous integration. Bone viability following large segmental reconstructions in patients after mono- and multi-level en bloc spondylectomies (EBS) was analyzed. Spinal fusion was assessed on plain radiographs and CT scans according to the FDA fusion criteria as well as (18)F PET/CT.

RESULTS

A total of eight patients underwent (18)F PET/CT were included (one 4-level-, one 3-level, two 2-level and four 1-level EBS). The average follow-up between EBS and radiographic studies was 24.8 months. On plain radiographs and CT scans, successful fusion was confirmed in all patients. However, (18)F PET/CT showed non-union in all cases. The metabolic bone activity within the cage was fourfold decreased compared to the reference vertebra, whereas the metabolic activity of the adjacent endplates was 1.6-fold increased compared to the reference vertebra.

CONCLUSION

This study suggests a discrepancy between fusion rates assessed by plain radiographs and CT scan compared to (18)F PET/CT.

Positron emission tomography in spinal infections

Magnetic resonance imaging is the imaging method of choice for diagnosing infection of the spine in unoperated cases. 2-[(18)F]-fluoro-2deoxy-d-glucose positron emission tomography/computed tomography study is recommended to distinguish between spinal infection and common Modic change in patients with metallic implants and prosthetic replacements and for differentiating tuberculous from pyogenic spondylitis in ambiguous cases, reflecting the activity of the infection. Also, it seems to have a strong clinical impact in more than half of patients with infectious spondylitis, while it is superior to other imaging techniques in revealing residual disease after treatment and early response to therapy. New tracers as well as new hybrid modalities are under investigation.

Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Interpretation Criteria for Assessment of Antibiotic Treatment Response in Pyogenic Spine Infection

PURPOSE

The objective of the study was to determine if fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) can assess the response of patients with pyogenic spine infection to antibiotic treatment in a clinically useful time frame.

METHODS

Twenty-eight patients with suspected pyogenic spine infection had baseline (18)F-FDG PET/CT. Patients with proven or probable infection were divided into good and poor responders to antibiotic therapy based on clinical criteria. These patients had a follow-up (18)F-FDG PET/CT 6-8 weeks later.

RESULTS

Six of 28 patients were deemed negative for infection based on (18)F-FDG PET/CT. Two patients were excluded because of discrepancies in interpretation. Of the 20 patients deemed positive for infection, 13 had a pathogen isolated and all showed (18)F-FDG uptake in bone and/or soft tissue at baseline. Patients with a poor clinical response to treatment had persistent (18)F-FDG uptake in bone and/or soft tissue on follow-up. Patients with good clinical response had uptake confined to the margins of the destroyed disc. None of these patients had recurrent infection, even if antibiotics had already been discontinued at the time of the follow-up scan.

CONCLUSIONS

(18)F-FDG uptake confined to the margins of a destroyed disc after antibiotic therapy of pyogenic spine infection must not be considered indicative of persistent infection and likely represents mechanically induced inflammation. (18)F-FDG uptake in bone or soft tissue does indicate active infection. Quantification of activity could not reliably differentiate patients with active infection from those without active infection and those who had had a successful response to therapy. The pattern of activity is critical to accurate interpretation.

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

PURPOSE

To prospectively compare (18)F-FDG PET/CT and MRI in the diagnosis of haematogenous spondylodiscitis

METHODS

The study included 26 patients (12 women, 14 men; mean age 59 ± 17 years) with clinical symptoms of infection of the spine. Patients who had had prior spinal surgery or any type of antibiotic therapy in the previous 3 months were excluded from the study. Whole-body PET/CT 60 min after injection of 4.07 MBq/kg of (18)F-FDG and an MRI scan of the spine was performed in all patients. SUVmax in an area surrounding the lesions with the suspicion of infection as well as a background SUVmean in a preserved area of the spine were calculated for quantification. Infection was diagnosed by microbiological documentation in cultures of image-guided spinal puncture fluid or blood. Infection was excluded if symptoms were absent without antimicrobial therapy during a follow-up of at least 6 months.

RESULTS

Spondylodiscitis was confirmed in 18 of the 26 patients. Staphylococcus aureus was found in 8 patients, Mycobacterium tuberculosis in 4, Escherichia coli in 2 and other pathogens in 4. Of the remaining 8 patients, the diagnoses were degenerative spondyloarthropathy in 5 and vertebral fracture in 3. The sensitivity, specificity, and positive and negative predictive value were 83%, 88%, 94% and 70% for (18)F-FDG PET/CT, and 94%, 38%, 77% and 75% for MRI, respectively. The accuracies of (18)F-FDG PET/CT and MRI were similar (84% and 81%, respectively). The combination of (18)F-FDG PET/CT and MRI detected the infection in 100% of the patients with spondylodiscitis. (18)F-FDG uptake, quantified in terms of SUVmax corrected by the background SUVmean, was significantly higher in patients with spondylodiscitis than in those without infection (p < 0.001).

CONCLUSION

Due to its high specificity, (18)F-FDG PET/CT should be considered as a first-line imaging procedure in the diagnosis of spondylodiscitis. Quantification of uptake in terms of SUVmax was able to discriminate infection of the spine from other processes in this series of patients.

Radiation-induced DNA damage and the relative biological effectiveness of 18F-FDG in wild-type mice

Clinically, the most commonly used positron emission tomography (PET) radiotracer is the glucose analog 2-[(18)F] fluoro-2-deoxy-D-glucose ((18)F-FDG), however little research has been conducted on the biological effects of (18)F-FDG injections. The induction and repair of DNA damage and the relative biological effectiveness (RBE) of radiation from (18)F-FDG relative to 662 keV γ-rays were investigated. The study also assessed whether low-dose radiation exposure from (18)F-FDG was capable of inducing an adaptive response. DNA damage to the bone marrow erythroblast population was measured using micronucleus formation and lymphocyte γH2A.X levels. To test the RBE of (18)F-FDG, mice were injected with a range of activities of (18)F-FDG (0-14.80 MBq) or irradiated with Cs-137 γ-rays (0-100 mGy). The adaptive response was investigated 24h after the (18)F-FDG injection by 1 Gy in vivo challenge doses for micronucleated reticulocyte (MN-RET) formation or 1, 2 and 4 Gy in vitro challenges doses for γH2A.X formation. A significant increase in MN-RET formation above controls occurred following injection activities of 3.70, 7.40 or 14.80 MBq (P < 0.001) which correspond to bone marrow doses of ~35, 75 and 150 mGy, respectively. Per unit dose, the Cs-137 radiation exposure induced significantly more damage than the (18)F-FDG injections (RBE = 0.79 ± 0.04). A 20% reduction in γH2A.X fluorescence was observed in mice injected with a prior adapting low dose of 14.80 MBq (18)F-FDG relative to controls (P < 0.019). A 0.74 MBq (18)F-FDG injection, which gives mice a dose approximately equal to a typical human PET scan, did not cause a significant increase in DNA damage nor did it generate an adaptive response. Typical (18)F-FDG injection activities used in small animal imaging (14.80 MBq) resulted in a decrease in DNA damage, as measured by γH2A.X formation, below spontaneous levels observed in control mice. The (18)F-FDG RBE was <1.0, indicating that the mixed radiation quality and/or low dose rate from PET scans is less damaging than equivalent doses of gamma radiation.

Surgical site infections following spine surgery: eliminating the controversies in the diagnosis

Surgical site infection (SSI) following spine surgery is a dreaded complication with significant morbidity and economic burden. SSIs following spine surgery can be superficial, characterized by obvious wound drainage or deep-seated with a healed wound. Staphylococcus aureus remains the principal causal agent. There are certain pre-operative risk factors that increase the risk of SSI, mainly diabetes, smoking, steroids, and peri-operative transfusions. Additionally, intra-operative risk factors include surgical invasiveness, type of fusion, implant use, and traditional instead of minimally invasive approach. A high level of suspicion is crucial to attaining an early definitive diagnosis and initiating appropriate management. The most common presenting symptom is back pain, usually manifesting 2–4 weeks and up to 3 months after a spinal procedure. Scheduling a follow-up visit between weeks 2 and 4 after surgery is therefore necessary for early detection. Inflammatory markers are important diagnostic tools, and comparing pre-operative with post-operative levels should be done when suspecting SSIs following spine surgery. Particularly, serum amyloid A is a novel inflammatory marker that can expedite the diagnosis of SSIs. Magnetic resonance imaging remains the diagnostic modality of choice when suspecting a SSI following spine surgery. While 18F-fluorodeoxyglucose-positron emission tomography is not widely used, it may be useful in challenging cases. Despite their low yield, blood cultures should be collected before initiating antibiotic therapy. Samples from wound drainage should be sent for Gram stain and cultures. When there is a high clinical suspicion of SSI and in the absence of superficial wound drainage, computed tomography-guided aspiration of paraspinal collections is warranted. Unless the patient is hemodynamically compromised, antibiotics should be deferred until proper specimens for culture are secured.

Multifocal infections of the musculoskeletal system: description of a safe one-step procedure for eradication of associated spinal infections

BACKGROUND

The aim of this study was to evaluate the clinical outcome after radical surgical treatment of multifocal infections involving the spine.

METHODS

The study demonstrates a retrospective chart review of seven patients who had more than three different abscesses in the musculoskeletal system and at least one of them in the area of the spinal column. All patients had a sepsis.

RESULTS

Beside different musculoskeletal abscesses four patients had a spondylodiscitis in the cervical spine segments C4/5 or C5/6. Six patients had inflammatory processes in the lumbar spine with epidural abscesses, diffuse thoracolumbar paravertebral abscesses and a spondylodiscitis in different segments. In all cases we performed a radical surgical treatment of all related inflammatory focuses. Prompt radical surgical treatment of the spine included decompression, debridement and in the cases of spondylodiscitis a fusion of the involved segments. For more than one focus at the spine, a surgical one-step procedure was performed. An antibiotic therapy was administered for six to eight weeks. In follow up examinations no signs of ongoing inflammatory processes were seen in imaging studies or laboratory tests.

CONCLUSIONS

In the event of multiple abscesses of the musculoskeletal system involving the spine an early correct diagnosis and radical surgical treatment is recommended. We strongly favor a surgical single-stage procedure for treatment of multiple infections of the spine. In addition to a radical debridement and a sufficient decompression, the segmental fusion of affected areas in spondylodiscitis is essential. At the same time a surgical therapy of all other infected sites should be performed.

The use of (18)F-FDG-PET/CT for diagnosis and treatment monitoring of inflammatory and infectious diseases

FDG-PET, combined with CT, is nowadays getting more and more relevant for the diagnosis of several infectious and inflammatory diseases and particularly for therapy monitoring. Thus, this paper gives special attention to the role of FDG-PET/CT in the diagnosis and therapy monitoring of infectious and inflammatory diseases. Enough evidence in the literature already exists about the usefulness of FDG-PET/CT in the diagnosis, management, and followup of patients with sarcoidosis, spondylodiscitis, and vasculitis. For other diseases, such as inflammatory bowel diseases, rheumatoid arthritis, autoimmune pancreatitis, and fungal infections, hard evidence is lacking, but studies also point out that FDG-PET/CT could be useful. It is of invaluable importance to have large prospective multicenter studies in this field to provide clear answers, not only for the status of nuclear medicine in general but also to reduce high costs of treatment.

18F-FDG PET/CT evaluation of children and young adults with suspected spinal fusion hardware infection

BACKGROUND

Evaluation of the child with spinal fusion hardware and concern for infection is challenging because of hardware artifact with standard imaging (CT and MRI) and difficult physical examination. Studies using (18)F-FDG PET/CT combine the benefit of functional imaging with anatomical localization.

OBJECTIVE

To discuss a case series of children and young adults with spinal fusion hardware and clinical concern for hardware infection. These people underwent FDG PET/CT imaging to determine the site of infection.

MATERIALS AND METHODS

We performed a retrospective review of whole-body FDG PET/CT scans at a tertiary children's hospital from December 2009 to January 2012 in children and young adults with spinal hardware and suspected hardware infection. The PET/CT scan findings were correlated with pertinent clinical information including laboratory values of inflammatory markers, postoperative notes and pathology results to evaluate the diagnostic accuracy of FDG PET/CT. An exempt status for this retrospective review was approved by the Institution Review Board.

RESULTS

Twenty-five FDG PET/CT scans were performed in 20 patients. Spinal fusion hardware infection was confirmed surgically and pathologically in six patients. The most common FDG PET/CT finding in patients with hardware infection was increased FDG uptake in the soft tissue and bone immediately adjacent to the posterior spinal fusion rods at multiple contiguous vertebral levels. Noninfectious hardware complications were diagnosed in ten patients and proved surgically in four. Alternative sources of infection were diagnosed by FDG PET/CT in seven patients (five with pneumonia, one with pyonephrosis and one with superficial wound infections).

CONCLUSION

FDG PET/CT is helpful in evaluation of children and young adults with concern for spinal hardware infection. Noninfectious hardware complications and alternative sources of infection, including pneumonia and pyonephrosis, can be diagnosed. FDG PET/CT should be the first-line cross-sectional imaging study in patients with suspected spinal hardware infection. Because pneumonia was diagnosed as often as spinal hardware infection, initial chest radiography should also be performed.

Spinal infection: state of the art and management algorithm

INTRODUCTION

Spinal infection is a rare pathology although a concerning rising incidence has been observed in recent years. This increase might reflect a progressively more susceptible population but also the availability of increased diagnostic accuracy. Yet, even with improved diagnosis tools and procedures, the delay in diagnosis remains an important issue. This review aims to highlight the importance of a methodological attitude towards accurate and prompt diagnosis using an algorithm to aid on spinal infection management.

METHODS

Appropriate literature on spinal infection was selected using databases from the US National Library of Medicine and the National Institutes of Health.

RESULTS

Literature reveals that histopathological analysis of infected tissues is a paramount for diagnosis and must be performed routinely. Antibiotic therapy is transversal to both conservative and surgical approaches and must be initiated after etiological diagnosis. Indications for surgical treatment include neurological deficits or sepsis, spine instability and/or deformity, presence of epidural abscess and upon failure of conservative treatment.

CONCLUSIONS

A methodological assessment could lead to diagnosis effectiveness of spinal infection. Towards this, we present a management algorithm based on literature findings.

Imaging findings of Pott's disease

Tuberculosis (TB) continues to be an important public health problem in developed countries especially in deprived socioeconomic groups, older people, immunocompromised patients, drug-therapy resistant cases and the immigrant population. The spine is the most frequent location of musculoskeletal TB. The wide range of clinical presentations results in difficulties and delays in diagnosis. Advanced disease mimics other infections and malignancy. The diagnosis of spinal infections relies on three main factors: clinical symptoms, imaging and bacteriological culture. Advanced imaging such as Magnetic Resonance Imaging (MRI), Multidetector Computed Tomography (MDCT) and Fluor18-Deoxiglucose Positron Emission Tomography combined with CT (F-18 FDG PET-CT) demonstrate lesion extent, serve as guide for biopsy with aspiration for culture, assist surgery planning and contribute to follow-up. Diagnosis of TB cannot be established solely on the basis of clinical tests or imaging findings and biopsy may be required. Differential diagnosis between tuberculous and pyogenic spondylitis is of clinical importance, but may be difficult on the basis of radiological findings alone. Findings not pathognomonic but favoring tuberculous etiology include: slow progression of lesions with late preservation of disk space, involvement of several contiguous segments, large intraosseous and paraspinal abscesses containing calcifications, and body collapse with kyphotic deformity. In this essay the highlights of TB imaging are reviewed through published literature. In addition, we review retrospectively the radiological findings of 48 patients with tuberculous spondylitis treated from 1993 to 2010. There were 23 male and 25 female patients with a mean age of 53 years.

Fluorine-18 fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography scan contributes to the diagnosis and management of brucellar spondylodiskitis

Background

Limited data suggest that fluorine-18 fluoro-2-deoxy-D-glucose (F-18 FDG) positron emission tomography combined with computed tomography (PET/CT) scan may be useful for diagnosing infections of the spine. Brucellar spondylodiskitis might be devastating and current imaging techniques lack sensitivity and specificity. The aim of this prospective study was to determine the role of F-18 FDG PET/CT scan in the diagnosis of brucellar spondylodiskitis and in monitoring the efficacy of its treatment.

Methods

Ten consecutive patients with brucellar spondylitis were prospectively evaluated with PET/CT. Baseline evaluation included also magnetic resonance imaging (MRI) of the affected spine, indices of inflammation, the slide agglutination test (SAT), and the standard hematology and biochemistry. All cases were treated with suitable antibiotics until resolution or significant improvement of clinical and radiological (MRI) findings. Upon completion of treatment, they were re-evaluated with follow-up PET/CT scan. The maximum standardized uptake values (SUV) were measured and compared with SAT.

Results

In all patients there was an increased F-18 FDG activity in the infected spine region detected by the initial MRI. F-18 FDG PET/CT provided additional information, compared to MRI, in 4 (40%) patients. More specifically it revealed additional spine lesions (in 3 patients), lymphadenitis, arthritis, organomegaly, as well as new paravertebral soft tissue involvement and epidural masses. This additional information had an impact on the duration of treatment in these patients. At the end of treatment all patients had a complete clinical response; 5 patients had positive serology, 6 patients had residual MRI findings, while 9 had a positive PET/CT but with significantly decreased FDG uptake compared to baseline (median 2.6, range 1.4 – 4.4 vs. median 5.5, range 2.8 – 9.4, p = 0.005). During the follow up period (median 12.5 months) no relapses have been observed. No significant association was observed between the SUV and SAT.

Conclusions

Our study suggests that in patients with brucellar spondylodiskitis F-18 FDG PET/CT scan can provide additional information on the spread of the infection, compared to MRI. Successful treatment is associated with a significant decrease in SUVmax values; thus, PET/CT scan may be a complementary method for determining the efficacy of treatment.

Two-step labeling of Staphylococcus aureus with Lysostaphin-Azide and DIBO-Alexa using click chemistry

Specific bacteria imaging is highly desirable in clinical diagnostics. Probes enabling rapid and specific diagnostics of bacteria are limited. Current clinical infection diagnostics is time consuming and invasive, relies on microbiological cultures. We investigated the potential of Lysostaphin as a specific probe to label staphylococci in a new labeling protocol. We used azido (N(3))-modified Lysostaphin-N(3) and DIBO-dye in a two-step bacteria-labeling protocol. N(3) and DIBO (di-benzocyclooctyne) are the counterparts of the "click" chemistry. In the first step, Lysostaphin-N(3) binds specifically to Staphylococcus aureus. In the second step, N(3) clicks to DIBO thus achieving the selective for S. aureus labeling. Such a two-step approach effectively distinguishes S. aureus from Escherichia coli; non-toxic and was proven to work in vivo. The two-step labeling protocol is a promising approach for diagnostic imaging of staphylococcal infections in clinical settings.

Spinal fusion-hardware construct: Basic concepts and imaging review

The interpretation of spinal images fixed with metallic hardware forms an increasing bulk of daily practice in a busy imaging department. Radiologists are required to be familiar with the instrumentation and operative options used in spinal fixation and fusion procedures, especially in his or her institute. This is critical in evaluating the position of implants and potential complications associated with the operative approaches and spinal fixation devices used. Thus, the radiologist can play an important role in patient care and outcome. This review outlines the advantages and disadvantages of commonly used imaging methods and reports on the best yield for each modality and how to overcome the problematic issues associated with the presence of metallic hardware during imaging. Baseline radiographs are essential as they are the baseline point for evaluation of future studies should patients develop symptoms suggesting possible complications. They may justify further imaging workup with computed tomography, magnetic resonance and/or nuclear medicine studies as the evaluation of a patient with a spinal implant involves a multi-modality approach. This review describes imaging features of potential complications associated with spinal fusion surgery as well as the instrumentation used. This basic knowledge aims to help radiologists approach everyday practice in clinical imaging.

Progress in diagnosis and treatment of cervical postoperative infection

Postoperative infection is the commonest complication that causes failure of spinal surgery. Although the rate of infection after cervical surgery is lower than that after lumbar surgery, the absolute number of cases is increasing. In recent years, new techniques, such as serum amyloid A and fludeoxyglucose ((18) F) positron emission tomography (18F-FDG PET), have emerged and gradually been employed in the diagnosis of postoperative infection, updating the ability to identify the presence of infection. Most patients with cervical postoperative infection require re-operation. There are three principles for such surgery: thorough debridement, adequate drainage and ensuring stability of the spine. Some severe cases even need emergency surgery. This article aims to discuss the controversial issues in diagnosis and treatment of cervical postoperative infection, as well as progress in related studies.

PET/CT imaging in infectious conditions

New aggressive pathogens are responsible for the increasing incidence and difficult management of infections. Modern epidemics such as diabetes are frequently complicated by severe infections with subsequent high morbidity. Diagnosis (essentially early detection of infection) and also management decision making pose clinical challenges. Many resources are invested in developing precise, noninvasive diagnostic tests and efficient therapies for infectious processes. Nuclear medicine procedures are part of the evaluation armamentarium of patients with suspected or confirmed infection. Their strength relies on the fact that they are noninvasive tests that provide both functional as well as metabolic information early in the course of disease. Their limitations relate to the need for specific radiotracers and the rather low resolution of images. These limitations have been largely overcome by the hybrid PET/CT and SPECT/CT technology. PET/CT, primarily using FDG, is redefining the diagnostic work up and is currently leading to changes in the management of patients with suspected or known infections. The main indications for FDG PET/CT in infection, as well as updated literature results, are presented in the following review.