PET and SPECT in osteomyelitis and prosthetic bone and joint infections: a systematic review

Multimodal positron emission tomography (PET) imaging in non-oncologic musculoskeletal radiology

Musculoskeletal (MSK) disorders are associated with large impacts on patient's pain and quality of life. Conventional morphological imaging of tissue structure is limited in its ability to detect pain generators, early MSK disease, and rapidly assess treatment efficacy. Positron emission tomography (PET), which offers unique capabilities to evaluate molecular and metabolic processes, can provide novel information about early pathophysiologic changes that occur before structural or even microstructural changes can be detected. This sensitivity not only makes it a powerful tool for detection and characterization of disease, but also a tool able to rapidly assess the efficacy of therapies. These benefits have garnered more attention to PET imaging of MSK disorders in recent years. In this narrative review, we discuss several applications of multimodal PET imaging in non-oncologic MSK diseases including arthritis, osteoporosis, and sources of pain and inflammation. We also describe technical considerations and recent advancements in technology and radiotracers as well as areas of emerging interest for future applications of multimodal PET imaging of MSK conditions. Overall, we present evidence that the incorporation of PET through multimodal imaging offers an exciting addition to the field of MSK radiology and will likely prove valuable in the transition to an era of precision medicine.

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.

Insights into Peptidoglycan-Targeting Radiotracers for Imaging Bacterial Infections: Updates, Challenges, and Future Perspectives

The unique structural architecture of the peptidoglycan allows for the stratification of bacteria as either Gram-negative or Gram-positive, which makes bacterial cells distinguishable from mammalian cells. This classification has received attention as a potential target for diagnostic and therapeutic purposes. Bacteria's ability to metabolically integrate peptidoglycan precursors during cell wall biosynthesis and recycling offers an opportunity to target and image pathogens in their biological state. This Review explores the peptidoglycan biosynthesis for bacteria-specific targeting for infection imaging. Current and potential radiolabeled peptidoglycan precursors for bacterial infection imaging, their development status, and their performance in vitro and/or in vivo are highlighted. We conclude by providing our thoughts on how to shape this area of research for future clinical translation.

SPECT/CT of Total Ankle Arthroplasty

Use of SPECT/CT (Single Photon Emission Computed Tomography/Computed Tomography) is increasing providing additional information in patients with inconclusive clinical examination and unremarkable imaging findings presenting with chronic pain after total ankle arthroplasty. To differentiate the cause of pain after total ankle arthroplasty can be challenging. SPECT/CT combines structural and metabolic imaging as a hybrid tool leading to higher specificity and overall diagnostic accuracy presumably in cases of gutter impingement, prosthetic loosening, and osteoarthritis of adjacent joints. Moreover, SPECT/CT can complement diagnostic work up in periprosthetic joint infections. Basal tracer enhancement has to be considered for the interpretation of imaging findings.

Glycolytic reprogramming underlies immune cell activation by polyethylene wear particles

Primary total joint arthroplasties (TJAs) are widely and successfully applied reconstructive procedures to treat end-stage arthritis. Nearly 50 % of TJAs are now performed in young patients, posing a new challenge: performing TJAs which last a lifetime. The urgency is justified because subsequent TJAs are costlier and fraught with higher complication rates, not to mention the toll taken on patients and their families. Polyethylene particles, generated by wear at joint articulations, drive aseptic loosening by inciting insidious inflammation associated with surrounding bone loss. Down modulating polyethylene particle-induced inflammation enhances integration of implants to bone (osseointegration), preventing loosening. A promising immunomodulation strategy could leverage immune cell metabolism, however, the role of immunometabolism in polyethylene particle-induced inflammation is unknown. Our findings reveal that immune cells exposed to sterile or contaminated polyethylene particles show fundamentally altered metabolism, resulting in glycolytic reprogramming. Inhibiting glycolysis controlled inflammation, inducing a pro-regenerative phenotype that could enhance osseointegration.

A comparative 18F-FDG and an anti-PD-L1 probe PET/CT imaging of implant-associated Staphylococcus aureus osteomyelitis

Background

Early and accurate diagnosis of infection-induced osteomyelitis, which often involves increased PD-L1 expression, is crucial for better treatment outcomes. Radiolabeled anti-PD-L1 nuclear imaging allows for sensitive and non-invasive whole-body assessments of PD-L1 expression. This study aimed to compare the efficacy of 18F-FDG and an 18F-labeled PD-L1-binding peptide probe (18F-PD-L1P) in PET imaging of implant-associated Staphylococcus aureus osteomyelitis (IAOM).

Methods

In this study, we synthesized an anti-PD-L1 probe and compared its efficacy with 18F-FDG and 18F-PD-L1P in PET imaging of implant-associated Staphylococcus aureus osteomyelitis (IAOM). The %ID/g ratios (i.e., radioactivity ratios between the infected and non-infected sides) of both probes were evaluated for sensitivity and accuracy in post-infected 7-day tibias and post-infected 21 days, and the intensity of 18F-PD-L1P uptake was compared with pathological changes measured by PD-L1 immunohistochemistry (IHC).

Results

Compared with 18F-FDG, 18F-PDL1P demonstrated higher %ID/g ratios for both post-infected 7-day tibias (P=0.001) and post-infected 21 days (P=0.028). The intensity of 18F-PD-L1P uptake reflected the pathological changes of osteomyelitic bones. In comparison to 18F-FDG, 18F-PDL1P provides earlier and more sensitive detection of osteomyelitis caused by S. aureus.

Conclusion

Our findings suggest that the 18F-PDL1P probe is a promising tool for the early and accurate detection of osteomyelitis caused by S. aureus.

Localization of osteomyelitis lesions for operative eradication of chronic osteomyelitis of the lower extremities by bone SPECT/CT: a feasibility study

PURPOSE

This study was performed to investigate the feasibility of bone single-photon emission tomography/computed tomography (SPECT/CT) for pre-operative planning of chronic osteomyelitis (COM) of the lower extremities by localization of osteomyelitis lesions.

METHODS

From January 2016 to January 2020, we surgically treated ten adult patients with Cierny-Mader type III COM in the tibia or femur for a mean duration of 24.4 months (range 7.0-70.0 months). We conducted pre-operative planning by bone SPECT/CT and localization of osteomyelitis lesions. The treatment consisted of intra-operative eradication of the infective focus and antibiotic administration. The clinical and radiological outcomes were retrospectively analyzed after a minimum of one year of follow-up.

RESULTS

The patients were surgically treated by thorough debridement, dead space management, and appropriate antibiotics without bone transport or an external fixator. The location of the hot uptake region on bone SPECT/CT coincided with that of the osteomyelitis lesion, which was confirmed intra-operatively in all patients. At an average of 16.5 ± 4.3 months (range, 13.0-25.0 months), clinical eradication of osteomyelitis was achieved in nine of the ten patients. One patient required amputation due to recurrence of osteomyelitis. A successful clinical outcome was achieved in eight patients; one suffered persistent ankle pain due to a destructive change in the ankle joint despite eradication of the infection.

CONCLUSION

Bone SPECT/CT is a feasible method for the localization and eradication of osteomyelitis lesions in COM of the lower extremities and has favourable clinical outcomes. It can also be applied in cases of distorted bony structures caused by previous trauma or surgery, or in the presence of implants.

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

Background

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

Methods

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

Results

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

Conclusions

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

ACR Appropriateness Criteria® Suspected Osteomyelitis, Septic Arthritis, or Soft Tissue Infection (Excluding Spine and Diabetic Foot): 2022 Update

Musculoskeletal infections involve bones, joints, and soft tissues. These infections are a common clinical scenario in both outpatient and emergent settings. Although radiography provides baseline findings, a multimodality approach is often implemented to provide more detailed information on the extent of infection involvement and complications. MRI with intravenous contrast is excellent for the evaluation of musculoskeletal infections and is the most sensitive for diagnosing osteomyelitis. MRI, CT, and ultrasound can be useful for joint and soft tissue infections. When MRI or CT is contraindicated, bone scans and the appropriate utilization of other nuclear medicine scans can be implemented for aiding in the diagnostic imaging of infection, especially with metal hardware and arthroplasty artifacts on MRI and CT. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer-reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances in which peer-reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

[18F]Fluoride Positron-Emission Tomography (PET) and [18F]FDG PET for Assessment of Osteomyelitis of the Jaw in Comparison to Computed Tomography (CT) and Magnetic Resonance Imaging (MRI): A Prospective PET/CT and PET/MRI Pilot Study

To investigate imaging features of osteomyelitis of the jaw (OMJ) using [18F]fluoride positron emission tomography (PET) and [18F]fluorodeoxyglucose (FDG)-PET compared with computed tomography (CT) and magnetic resonance imaging (MRI) to assess extent and disease activity. Six female patients (55.3 ± 10.0 years) were enrolled for assessment of symptomatic OMJ. 4/6 patients underwent [18F]FDG-PET/MRI and [18F]fluoride-PET/CT, one patient MRI and [18F]fluoride-PET/CT and another patient only [18F]FDG-PET/MRI. Image analysis was performed by two radiologists, an oral and maxillofacial surgeon, and a nuclear medicine specialist. The extent of affected jawbone was analyzed both qualitatively and quantitatively, including the PET tracer uptake, CT-Hounsfield-Units (HU) and MRI parameters in affected and healthy jawbone. All patients had trabecular sclerosis in the affected jawbone compared to healthy jawbone (560 ± 328 HU vs. 282 ± 211 HU; p > 0.05), while 3/6 patients had cortical erosions. Bone marrow edema and gadolinium enhancement were documented in 5/6 patients. In affected jawbone, [18F]fluoride-uptake was increased in all patients compared to healthy jawbone (SUVmean 15.4 ± 4.2 vs. 2.1 ± 0.6; p < 0.05), and [18F]FDG-uptake was moderately higher (SUVmean 1.9 ± 0.7 vs. 0.7 ± 0.2; p > 0.05). The extent of regions with increased metabolic activity was less than the extent of morphologic changes in all patients. Information on jawbone metabolism and inflammation is different from morphologic changes and therefore has the potential to provide a more accurate and objective assessment of the extent and activity of OMJ.

Systematic review: investigating the added diagnostic value of gadolinium contrast agents for osteomyelitis in the appendicular skeleton

OBJECTIVE

Osteomyelitis is an infection of the bone marrow. MRI with gadolinium-based contrast is frequently performed for cases of suspected osteomyelitis. The objective of this systematic review is to examine the diagnostic accuracy of contrast-enhanced vs non-contrast-enhanced MRI for osteomyelitis in the appendicular skeleton.

MATERIALS AND METHODS

We conducted a systematic review of MRI in the diagnosis of osteomyelitis by searching MEDLINE and EMBASE from January 2000 to March 2020. There were 21 studies that met the inclusion criteria for the systematic review for a total of 1095 patients. Analytic methods were based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses. Evidence was evaluated using the STARD criteria for evaluation of completeness and transparency of reporting.

RESULTS

For diagnosing osteomyelitis in the appendicular skeleton, MRI with gadolinium-based contrast has 89% sensitivity (95% CI, 86-92%), 79% specificity (95% CI, 75-83%), and 90% overall diagnostic accuracy ([SE] = 0.03). For diagnosing osteomyelitis in the appendicular skeleton, MRI without gadolinium-based contrast has a 92% sensitivity (95% CI, 87-96%), 89% specificity (95% CI, 84-93%), and 96% overall diagnostic accuracy ([SE] = 0.03). The median score of included studies was 85% utilizing the STARD criteria with excellent interobserver agreement of 83.4%. Limitations included small sample size of studies, with retrospective designs.

CONCLUSION

No evidence was found to suggest an added diagnostic value of gadolinium contrast for the diagnosis of osteomyelitis in the appendicular skeleton. For routine cases of suspected non-spinal osteomyelitis, non-contrast MRI of the area of interest is the next most appropriate study after radiographs.

Simultaneous 18F-FDG-PET/MRI for the detection of periprosthetic joint infections after knee or hip arthroplasty: a prospective feasibility study

Purpose

This study investigated the diagnostic value of simultaneous 18F-fluordeoxyglucose positron emission tomography/magnetic resonance imaging (PET/MRI) in suspected periprosthetic joint infection (PJI) of the hip and knee.

Methods

Sixteen prostheses from 13 patients with suspected PJI were prospectively examined using PET/MRI. Image datasets were evaluated in consensus by a radiologist and a nuclear physician for the overall diagnosis of ‘PJI’ (yes/no) and its anatomical involvement, such as the periprosthetic bone margin, bone marrow, and soft tissue. The imaging results were compared with the reference standard obtained from surgical or biopsy specimens and subjected to statistical analysis.

Results

Using the reference standard, ten out of the 13 prostheses (ten hips, threes knees) were diagnosed with PJI. Using PET/MRI, every patient with PJI was correctly diagnosed (sensitivity, 100%; specificity, 100%). Considering the anatomical regions, the sensitivity and specificity were 57% and 50% in the periprosthetic bone margin, 75% and 33% in the bone marrow, and 100% and 100% in the soft tissue.

Conclusion

PET/MRI can be reliably used for the diagnosis of PJI. However, assessment of the periprosthetic bone remains difficult due to the presence of artefacts. Thus, currently, this modality is unlikely to be recommended in clinical practice.

Bone and Joint Infections: The Role of Imaging in Tailoring Diagnosis to Improve Patients' Care

Imaging is needed for the diagnosis of bone and joint infections, determining the severity and extent of disease, planning biopsy, and monitoring the response to treatment. Some radiological features are pathognomonic of bone and joint infections for each modality used. However, imaging diagnosis of these infections is challenging because of several overlaps with non-infectious etiologies. Interventional radiology is generally needed to verify the diagnosis and to identify the microorganism involved in the infectious process through imaging-guided biopsy. This narrative review aims to summarize the radiological features of the commonest orthopedic infections, the indications and the limits of different modalities in the diagnostic strategy as well as to outline recent findings that may facilitate diagnosis.

Diagnostic Performance of Single-Photon Emission Computed Tomography/Computed Tomography in Aseptic Loosening: A Systematic Review and Meta-Analysis

BACKGROUND

The aim of this study is to evaluate the diagnostic value and clinical applicability of single-photon emission computed tomography/computed tomography (SPECT/CT) in aseptic loosening (AL) of prostheses by meta-analysis.

METHOD

Literature on the diagnostic value of SPECT/CT in AL of prostheses was obtained by computer and manual review. The quality of the included studies was evaluated according to the Quality Assessment Diagnostic Accuracy Studies 2. Pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio, and other indicators were calculated, and a forest map and summary receiver operating characteristic were drawn to calculate the area under the curve. Meta-regression analysis was performed to identify the sources of heterogeneity and corresponding subgroup analysis was performed. A Fagan plot, likelihood ratio point plot, and Deek's funnel plot were drawn and analyzed.

RESULTS

A total of 15 studies were included. The meta-analysis results showed that the pooled sensitivity and specificity of SPECT/CT for the diagnosis of aseptic prosthetic loosening were 0.94, 95% confidence interval [CI] (0.90-0.96) and 0.89, 95% CI (0.78-0.95), respectively while the pooled positive likelihood ratio and pooled negative likelihood ratio were 8.65, 95% CI (4.18-17.90) and 0.07, 95% CI (0.04-0.11), respectively. The pooled diagnostic odds ratio was 130.36, 95% CI (45.18-376.19), and the area under the curve was 0.97, 95% CI (0.95-0.98).

CONCLUSION

As a diagnostic method for AL, SPECT/CT has high diagnostic sensitivity and specificity as well as high diagnostic efficiency. It has good clinical application value and should be a primary choice in the diagnosis of AL after joint replacement.

PET/MRI in paediatric disease

Nuclear medicine and molecular imaging have a small but growing role in the management of paediatric and neonatal diseases. During the past decade, combined PET/MRI has emerged as a clinically important hybrid imaging modality in paediatric medicine due to diagnostic advantages and reduced radiation exposure compared to alternative techniques. The applications for nuclear medicine, radiopharmaceuticals and combined PET/MRI in paediatric diagnosis is broadly similar to adults, however there are some key differences. There are a variety of clinical applications for PET/MRI imaging in children including, but not limited to, oncology, neurology, cardiovascular, infection and chronic inflammatory diseases, and in renal-urological disorders. In this article, we review the applications of PET/MRI in paediatric and neonatal imaging, its current role, advantages and disadvantages over other hybrid imaging techniques such as PET/CT, and its future applications. Overall, PET/MRI is a powerful imaging technology in diagnostic medicine and paediatric diseases. Higher soft tissue contrasts and lower radiation dose of the MRI makes it the superior technology compared to other conventional techniques such as PET/CT or scintigraphy. However, this relatively new hybrid imaging has also some limitations. MRI based attenuation correction remains a challenge and although methodologies have improved significantly in the last decades, most remain under development.

Assessing the optimal imaging modality in the diagnosis of jaw osteomyelitis. A meta-analysis

Osteomyelitis is an inflammatory infectious disease that affects bone and bone marrow. Histopathology remains the gold standard method for diagnosis, but imaging modalities also play an important role. We systematically reviewed five articles with comparative studies on plain films, computed tomography (CT) scan, magnetic resonance imaging (MRI), cone beam computed tomography (CBCT), positron emission tomography (PET), single photon-emission computed tomography (SPECT), scintigraphy, and SPECT/CT. Scintigraphy and SPECT/CT has the highest sensitivity of 100%. PET is only to be used in cases of follow up. Orthopantomography (OPG) is the most common initial diagnostic tool despite its low sensitivity. CT provides the necessary specificity needed for radionuclide imaging, which has the highest negative predictive value of 100% and a positive predictive value >95%. SPECT/CT with 100% sensitivity and 85% specificity can be considered as the imaging modality of choice for initial diagnosis and follow up.

Utility of positron emission tomography imaging in the diagnosis of chronic Q fever: A Systematic Review

Chronic Q fever is a diagnostic challenge. Diagnosis relies on serology and/or the detection of DNA from blood or tissue samples. PET-CT identifies tissues with increased glucose metabolism, thus identifying foci of inflammation. Our aim was to review the existing literature on the use of PET-CT to help diagnose chronic Q fever. A literature search was conducted in PubMed and Google Scholar to ascertain publications that included the terms 'Positron Emission Tomography' and 'PET CT' in combination with subheadings 'chronic Q fever' and 'Coxiella burnetii' within the search. To broaden our search retrieval, we used the terms 'chronic Q fever' and 'PET-CT'. Published literature up to 16^th April 2020 was included. 274 articles were initially identified. Post-exclusion criteria, 46 articles were included. Amongst case reports and series, the most frequent focus of infection was vascular, followed by musculoskeletal then cardiac. 79.5% of patients had a focus detected with 55.3% of these having proven infected prosthetic devices. Amongst the retrospective and prospective studies, a total of 394 positive sites of foci were identified with 186 negative cases. Some had follow-up scans (53), with 75.5% showing improvement or resolution. Average timeframe for documented radiological resolution post-initiating treatment was 8.86 months. PET-CT is a useful tool in the management of chronic Q fever. Knowledge of a precise focus enables for directed surgical management helping reduce microbial burden, preventing future complications. Radiological resolution of infection can give clinicians reassurance on whether antimicrobial therapy can be ceased earlier, potentially limiting side effects.

Fewer-Angle SPECT/CT Blood Pool Imaging for Infection and Inflammation

A new protocol for rapid SPECT/CT blood pool imaging consisting of fewer image-angle acquisitions (fewer-angle SPECT/CT, or FASpecT/CT) was evaluated for localization of focal sites of soft-tissue inflammation, infection, and osteomyelitis. Methods: Immediately after dynamic flow and standard planar blood pool imaging with ^99mTc-methylene diphosphonate, FASpecT/CT was performed with a dual-head γ-camera consisting of 6 steps over 360°, 12 total images with 30° of separation between angles, and 30 s per image, requiring a total imaging time of approximately 3 min. Images were reconstructed using iterative ordered-subset expectation maximization. Before use in a patient-care setting, various FASpecT/CT acquisition protocols were modeled using a phantom to determine the minimum number of stops and the stop duration required to produce a reliable image. Results: FASpecT/CT images provided excellent 3-dimensional localization of spine osteomyelitis, soft-tissue infection of the foot, and tendonitis of the hand and foot using a 3-min image acquisition time. The FASpecT/CT acquisition protocol required 1.3-3.5 min, including camera movement time. This was a reduction of 72%-90% from the time required for the standard 60-angle, 20-s SPECT/CT acquisition. Conclusion: The ability of FASpecT/CT blood pool images to help localize focal sites of hyperemia and inflammation can increase exam sensitivity and specificity. Additionally, using a FASpecT/CT protocol decreases imaging time by up to 90%.

Imaging tests for the detection of osteomyelitis: a systematic review

BACKGROUND

Osteomyelitis is an infection of the bone. Medical imaging tests, such as radiography, ultrasound, magnetic resonance imaging (MRI), single-photon emission computed tomography (SPECT) and positron emission tomography (PET), are often used to diagnose osteomyelitis.

OBJECTIVES

To systematically review the evidence on the diagnostic accuracy, inter-rater reliability and implementation of imaging tests to diagnose osteomyelitis.

DATA SOURCES

We conducted a systematic review of imaging tests to diagnose osteomyelitis. We searched MEDLINE and other databases from inception to July 2018.

REVIEW METHODS

Risk of bias was assessed with QUADAS-2 [quality assessment of diagnostic accuracy studies (version 2)]. Diagnostic accuracy was assessed using bivariate regression models. Imaging tests were compared. Subgroup analyses were performed based on the location and nature of the suspected osteomyelitis. Studies of children, inter-rater reliability and implementation outcomes were synthesised narratively.

RESULTS

Eighty-one studies were included (diagnostic accuracy: 77 studies; inter-rater reliability: 11 studies; implementation: one study; some studies were included in two reviews). One-quarter of diagnostic accuracy studies were rated as being at a high risk of bias. In adults, MRI had high diagnostic accuracy [95.6% sensitivity, 95% confidence interval (CI) 92.4% to 97.5%; 80.7% specificity, 95% CI 70.8% to 87.8%]. PET also had high accuracy (85.1% sensitivity, 95% CI 71.5% to 92.9%; 92.8% specificity, 95% CI 83.0% to 97.1%), as did SPECT (95.1% sensitivity, 95% CI 87.8% to 98.1%; 82.0% specificity, 95% CI 61.5% to 92.8%). There was similar diagnostic performance with MRI, PET and SPECT. Scintigraphy (83.6% sensitivity, 95% CI 71.8% to 91.1%; 70.6% specificity, 57.7% to 80.8%), computed tomography (69.7% sensitivity, 95% CI 40.1% to 88.7%; 90.2% specificity, 95% CI 57.6% to 98.4%) and radiography (70.4% sensitivity, 95% CI 61.6% to 77.8%; 81.5% specificity, 95% CI 69.6% to 89.5%) all had generally inferior diagnostic accuracy. Technetium-99m hexamethylpropyleneamine oxime white blood cell scintigraphy (87.3% sensitivity, 95% CI 75.1% to 94.0%; 94.7% specificity, 95% CI 84.9% to 98.3%) had higher diagnostic accuracy, similar to that of PET or MRI. There was no evidence that diagnostic accuracy varied by scan location or cause of osteomyelitis, although data on many scan locations were limited. Diagnostic accuracy in diabetic foot patients was similar to the overall results. Only three studies in children were identified; results were too limited to draw any conclusions. Eleven studies evaluated inter-rater reliability. MRI had acceptable inter-rater reliability. We found only one study on test implementation and no evidence on patient preferences or cost-effectiveness of imaging tests for osteomyelitis.

LIMITATIONS

Most studies included < 50 participants and were poorly reported. There was limited evidence for children, ultrasonography and on clinical factors other than diagnostic accuracy.

CONCLUSIONS

Osteomyelitis is reliably diagnosed by MRI, PET and SPECT. No clear reason to prefer one test over the other in terms of diagnostic accuracy was identified. The wider availability of MRI machines, and the fact that MRI does not expose patients to harmful ionising radiation, may mean that MRI is preferable in most cases. Diagnostic accuracy does not appear to vary with the potential cause of osteomyelitis or with the body part scanned. Considerable uncertainty remains over the diagnostic accuracy of imaging tests in children. Studies of diagnostic accuracy in children, particularly using MRI and ultrasound, are needed.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42017068511.

FUNDING

This project was funded by the National Institute for Health Research Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 23, No. 61. See the NIHR Journals Library website for further project information.

The Role of Imaging Techniques to Define a Peri-Prosthetic Hip and Knee Joint Infection: Multidisciplinary Consensus Statements

Diagnosing a peri-prosthetic joint infection (PJI) remains challenging despite the availability of a variety of clinical signs, serum and synovial markers, imaging techniques, microbiological and histological findings. Moreover, the one and only true definition of PJI does not exist, which is reflected by the existence of at least six different definitions by independent societies. These definitions are composed of major and minor criteria for defining a PJI, but most of them do not include imaging techniques. This paper highlights the pros and cons of available imaging techniques—X-ray, ultrasound, computed tomography (CT), Magnetic Resonance Imaging (MRI), bone scintigraphy, white blood cell scintigraphy (WBC), anti-granulocyte scintigraphy, and fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT), discusses the added value of hybrid camera systems—single photon emission tomography/computed tomography (SPECT/CT), PET/CT and PET/MRI and reports consensus answers on important clinical questions that were discussed during the Third European Congress on Inflammation/Infection Imaging in Rome, December 2019.

Comparison of histopathology and preoperative 18F-FDG-PET/CT of osteomyelitis aiming for image guided surgery: A preliminary trial

OBJECTIVE

There are currently no robust methods for accurately localizing the infection focus of osteomyelitis. Accumulation of fluorodeoxyglucose (FDG) is nonspecific, and it is well-known that it can indicate inflammatory cells and sites of inflammation, and its effectiveness in detecting osteomyelitis has been reported recently. However, the optimal cut-off value for the Standardized Uptake Value (SUV) in detecting the focus of osteomyelitis through 18F-FDG-PET/CT is not known. We investigated the optimal SUV cut-off values using 18F-FDG positron emission tomography (PET)computed tomography (CT) to visualize the infection focus of osteomyelitis accurately.

PATIENTS AND METHODS

Initially, we investigated a case where osteomyelitis was bacteriologically detected after orthopedic surgery on lower limb. Based on the surgical pathology, we explored the optimal SUV cut-off value of the 18F-FDG PET/CT image taken before surgery. The SUV cut-off value was varied, using the GE Rainbow Color Scale on a dedicated workstation. We searched for the most accurate visualization of the extent of the infectious lesion. Subsequently, using the SUV cut-off value decided on the basis of the first case studied, we investigated the accuracy for diagnosing osteomyelitis. A total of sixteen patients underwent 18F-FDG PET/CT for suspected osteomyelitis (one case involved the upper extremity and 15 cases the lower one). All patients underwent surgery. The final diagnosis was made by means of bacteriologic culture of surgical specimens and histopathologic analysis. We compared surgical pathology and preoperative 18F-FDG PET/CT.

RESULTS

In the first case studied, the infection was most accurately localized with a SUV with a lower level of 2.00 and an upper of 8.00. Upon comparing the pathological findings and the 18F-FDG PET/CT, we set a SUV with a lower level of 2.00 and an upper level of 8.00. In thirteen cases, infection was detected with positive pathological findings. Preoperative 18F-FDG PET/CT showed high accumulation in these cases. In the remaining three cases, no infection was detected on either pathological findings nor 18F-FDG PET/CT findings.

CONCLUSIONS

The infection focus of osteomyelitis was accurately visualized by setting the SUV cut-off lower level to 2.00 and upper level to 8.00. We believe that this 18F-FDG PET/CT technique is helpful for image guided surgery of osteomyelitis.

Assessing the interactions between radiotherapy and antitumour immunity

Immunotherapy, specifically the introduction of immune checkpoint inhibitors, has transformed the treatment of cancer, enabling long-term tumour control even in individuals with advanced-stage disease. Unfortunately, only a small subset of patients show a response to currently available immunotherapies. Despite a growing consensus that combining immune checkpoint inhibitors with radiotherapy can increase response rates, this approach might be limited by the development of persistent radiation-induced immunosuppression. The ultimate goal of combining immunotherapy with radiotherapy is to induce a shift from an ineffective, pre-existing immune response to a long-lasting, therapy-induced immune response at all sites of disease. To achieve this goal and enable the adaptation and monitoring of individualized treatment approaches, assessment of the dynamic changes in the immune system at the patient level is essential. In this Review, we summarize the available clinical data, including forthcoming methods to assess the immune response to radiotherapy at the patient level, ranging from serum biomarkers to imaging techniques that enable investigation of immune cell dynamics in patients. Furthermore, we discuss modelling approaches that have been developed to predict the interaction of immunotherapy with radiotherapy, and highlight how they could be combined with biomarkers of antitumour immunity to optimize radiotherapy regimens and maximize their synergy with immunotherapy.

Molecular Imaging of Diabetic Foot Infections: New Tools for Old Questions

Diabetic foot infections (DFIs) are a common, complex, and costly medical problem with increasing prevalence. Diagnosing DFIs is a clinical challenge due to the poor specificity of the available methods to accurately determine the presence of infection in these patients. However, failure to perform an opportune diagnosis and provide optimal antibiotic therapy can lead to higher morbidity for the patient, unnecessary amputations, and increased healthcare costs. Novel developments in bacteria-specific molecular imaging can provide a non-invasive assessment of the infection site to support diagnosis, determine the extension and location of the infection, guide the selection of antibiotics, and monitor the response to treatment. This is a review of recent research in molecular imaging of infections in the context of DFI. We summarize different clinical and preclinical methods and the translational implications aimed to improve the care of patients with DFI.

Diagnostic Value of Bone SPECT/CT in Patients with Suspected Osteomyelitis

Objectives

The aim of our retrospective study was to evaluate the contribution of single photon emission computed tomography/computed tomography (SPECT/CT) to three phase bone scintigraphy/SPECT for the assessment of osteomyelitis (OM) and patient’s management.

Methods

Eighty-five patients who were suspected as having OM were included in this study. Tc-99m MDP three phase bone scintigraphy and SPECT/CT were performed to the region of suspected OM. SPECT/CT findings were compared with the findings of planar images/SPECT. Both planar bone scan/SPECT and SPECT/CT findings were divided into two groups: With OM and without OM. In all patients, scintigraphic diagnosis was confirmed by clinical follow up, laboratory findings, microscopic-bacteriological examinations, radiological, surgical, and pathological findings.

Results

SPECT/CT changed the diagnosis and treatment planning in 14/85 (16.5%) patients. SPECT/CT was significantly superior to planar scan/SPECT imaging for determining OM (kappa value was 0.626 for planar scan/SPECT, 0.929 for SPECT/CT). SPECT/CT was statistically more successful in detection of chronic OM, and useful in differentiating chronic OM from acute OM (kappa value was 0.541 for planar scan/SPECT, 0.944 for SPECT/CT).

Conclusion

SPECT/CT increases accuracy of the diagnosis in the evaluation of OM when it is compared to three phase bone scintigraphy/SPECT. SPECT/CT can change the diagnosis and management of the patients.

Cost-Effectiveness Study of One-Stage Treatment of Chronic Osteomyelitis with Bioactive Glass S53P4

This study was set up to evaluate the costs of a one-stage treatment of chronic osteomyelitis using bioactive glass S53P4 versus a two-stage treatment using gentamicin-loaded PMMA beads. Furthermore, a cost-effectiveness analysis was performed from a hospital’s perspective together with the evaluation of clinical outcome. A treatment group (n = 25) receiving one-stage surgery with bioactive glass was retrospectively compared with a two-stage control group (n = 25). An assessment was made of all costs included from first outpatient visit until one year after treatment. Bootstrap simulation and sensitivity analyses were performed. The primary endpoint was cost-effectiveness with clinical outcome as the secondary endpoint. The base case analyses shows dominance of the one-stage treatment with bioactive glass S53P4 due to lower costs and a better clinical outcome. Sensitivity analyses confirm these findings. This study is the first in its kind to show one-stage treatment of chronic osteomyelitis with bioactive glass S53P4 to be cost-effective.

Diagnosis of peripheral bone and prosthetic joint infections: overview on the consensus documents by the EANM, EBJIS, and ESR (with ESCMID endorsement)

OBJECTIVES

Peripheral bone infection (PBI) and prosthetic joint infection (PJI) are two different infectious conditions of the musculoskeletal system. They have in common to be quite challenging to be diagnosed and no clear diagnostic flowchart has been established. Thus, a conjoined initiative on these two topics has been initiated by the European Society of Radiology (ESR), the European Association of Nuclear Medicine (EANM), the European Bone and Joint Infection Society (EBJIS), and the European Society of Clinical Microbiology and Infectious Diseases (ESCMID). The purpose of this work is to provide an overview on the two consensus documents on PBI and PJI that originated by the conjoined work of the ESR, EANM, and EBJIS (with ESCMID endorsement).

METHODS AND RESULTS

After literature search, a list of 18 statements for PBI and 25 statements for PJI were drafted in consensus on the most debated diagnostic challenges on these two topics, with emphasis on imaging.

CONCLUSIONS

Overall, white blood cell scintigraphy and magnetic resonance imaging have individually demonstrated the highest diagnostic performance over other imaging modalities for the diagnosis of PBI and PJI. However, the choice of which advanced diagnostic modality to use first depends on several factors, such as the benefit for the patient, local experience of imaging specialists, costs, and availability. Since robust, comparative studies among most tests do not exist, the proposed flowcharts are based not only on existing literature but also on the opinion of multiple experts involved on these topics.

KEY POINTS

• For peripheral bone infection and prosthetic joint infection, white blood cell and magnetic resonance imaging have individually demonstrated the highest diagnostic performance over other imaging modalities. • Two evidence- and expert-based diagnostic flowcharts involving variable combination of laboratory tests, biopsy methods, and radiological and nuclear medicine imaging modalities are proposed by a multi-society expert panel. • Clinical application of these flowcharts depends on several factors, such as the benefit for the patient, local experience, costs, and availability.

Hybrid FDG-PET/MR imaging of chronic osteomyelitis: a prospective case series

Background

Magnetic resonance imaging (MRI) and 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography paired with computed tomography (PET/CT) are two commonly used imaging modalities in the complicated diagnostic workup of osteomyelitis. Diagnosis using these modalities relies on, respectively, anatomical (MRI) and metabolic (PET) signs. With hybrid PET/MRI being recently available, our goal is to qualitatively compare hybrid FDG PET/MRI to FDG PET/CT in the diagnosis and operative planning of chronic osteomyelitis.

Methods

Five patients with suspected chronic osteomyelitis in an extremity underwent an ¹⁸F-FDG single-injection/dual-imaging protocol with hybrid PET/CT and hybrid PET/MR. Images and clinical features were evaluated using a standardized assessment method. Standardized uptake value (SUV) measurements were performed on all images. Concordant and discordant findings between PET/MRI and PET/CT were analysed.

Results

The consensus diagnoses based on PET/MRI and PET/CT images were identical for all five patients. One discrepancy between PET/MRI and PET/CT was found in the assessment of the features in one patient. PET signal intensities and target-to-background ratios were on average highest for PET/MRI. On PET/MRI, the location of infection based on FDG uptake could clearly be correlated with certain soft tissue structures (oedema, fluid collection, or muscle), which is paramount for surgical planning.

Conclusions

In the presented cases, FDG PET/MRI led to the same diagnosis and provided at least the same diagnostic information as PET/CT. PET/MRI was able to provide additional soft-tissue information for the physician planning treatment. Because of this, we suggest that PET/MRI could be used for osteomyelitis diagnosis and treatment planning.

Single-photon Emission Computed Tomography-Computed Tomography Using 99mTc-labeled Leukocytes for Evaluating Infection Associated with a Cranial Implant in a Rhesus Macaque (Macaca mulatta)

An adult male rhesus macaque (Macaca mulatta) that was enrolled in a study evaluating cognition and memory presented with suppurative exudate along the margins of a long-standing cranial implant that included a stainless-steel head post, plastic left-sided recording cylinder, and acrylic over a previously placed right-sided recording cylinder. Both cylinders were located at the level of the prefrontal cortex. After treatment comprising systemic antibiotics and daily cleaning with povidone-iodine for several months, the macaque underwent single-photon emission computed tomography-computed tomography (SPECT-CT) in which his neutrophils were labeled with ^99mTc-hexamethylpropylene amine oxime ( 99m Tc-HMPAO) to evalu- ate for active infection below the implant. Soft tissue inflammation and osteomyelitis were found at the site of the previous right-sided recording cylinder. Cephalosporin and tetracycline antibiotics were administered for 12 wk. Follow-up SPECT-CT imaging was then performed to evaluate response to medical treatment. Results indicated no change in the degrees of soft tissue inflammation and osteomyelitis associated with the right-sided recording cylinder site. SPECT-CT imaging was used to guide the surgical removal of the implant and debridement of the infected tissue. On removal of the entire cranial implant, the osteomyelitis and soft tissue inflammation observed on the pre- and posttreatment SPECT-CT scans were confirmed. In addition, a large cavitary defect through the calvarium with suppurative exudate was discovered below the base of the head post. Infection in this defect was not apparent on SPECT; however, the bony defect was confirmed on reevaluation of the CT images. We concluded that the infection in this defect was silent on SPECT due to the limited vascularization of the sur-rounding bone and the chronicity of the infection. This case study is the first to describe the use of SPECT-CT for evaluating soft tissue inflammation and osteomyelitis beneath a cranial implant in a NHP.

Dual-isotope imaging allows in vivo immunohistochemistry using radiolabelled antibodies in tumours

While radiolabelled antibodies have found great utility as PET and SPECT imaging agents in oncological investigations, a notable shortcoming of these agents is their propensity to accumulate non-specifically within tumour tissue. The degree of this non-specific contribution to overall tumour uptake is highly variable and can ultimately lead to false conclusions. Therefore, in an effort to obtain a reliable measure of inter-individual differences in non-specific tumour uptake of radiolabelled antibodies, we demonstrate that the use of dual-isotope imaging overcomes this issue, enables true quantification of epitope expression levels, and allows non-invasive in vivo immunohistochemistry. The approach involves co-administration of (i) an antigen-targeting antibody labelled with zirconium-89 (89Zr), and (ii) an isotype-matched non-specific control IgG antibody labelled with indium-111 (111In). As an example, the anti-HER2 antibody trastuzumab was radiolabelled with 89Zr, and co-administered intravenously together with its 111In-labelled non-specific counterpart to mice bearing human breast cancer xenografts with differing HER2 expression levels (MDA-MB-468 [HER2-negative], MDA-MB-231 [low-HER2], MDA-MB-231/H2N [medium-HER2], and SKBR3 [high-HER2]). Simultaneous PET/SPECT imaging using a MILabs Vector4 small animal scanner revealed stark differences in the intratumoural distribution of [89Zr]Zr-trastuzumab and [111In]In-IgG, highlighting regions of HER2-mediated uptake and non-specific uptake, respectively. Normalisation of the tumour uptake values and tumour-to-blood ratios obtained with [89Zr]Zr-trastuzumab against those obtained with [111In]In-IgG yielded values which were most strongly correlated (R = 0.94; P = 0.02) with HER2 expression levels for each breast cancer type determined by Western blot and in vitro saturation binding assays, but not non-normalised uptake values. Normalised intratumoural distribution of [89Zr]Zr-trastuzumab correlated well with intratumoural heterogeneity HER2 expression.

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.

Consensus document for the diagnosis of prosthetic joint infections: a joint paper by the EANM, EBJIS, and ESR (with ESCMID endorsement)

Background

For the diagnosis of prosthetic joint infection, real evidence-based guidelines to aid clinicians in choosing the most accurate diagnostic strategy are lacking.

Aim and Methods

To address this need, we performed a multidisciplinary systematic review of relevant nuclear medicine, radiological, orthopaedic, infectious, and microbiological literature to define the diagnostic accuracy of each diagnostic technique and to address and provide evidence-based answers on uniform statements for each topic that was found to be important to develop a commonly agreed upon diagnostic flowchart.

Results and Conclusion

The approach used to prepare this set of multidisciplinary guidelines was to define statements of interest and follow the procedure indicated by the Oxford Centre for Evidence-based Medicine (OCEBM).

Electronic supplementary material

The online version of this article (10.1007/s00259-019-4263-9) contains supplementary material, which is available to authorized users.

Consensus document for the diagnosis of peripheral bone infection in adults: a joint paper by the EANM, EBJIS, and ESR (with ESCMID endorsement)

Introduction

In adults with a suspicion of peripheral bone infection, evidence-based guidelines in choosing the most accurate diagnostic strategy are lacking.

Aim and methods

To provide an evidence-based, multidisciplinary consensus document on the diagnostic management of adult patients with PBIs, we performed a systematic review of relevant infectious, microbiological, orthopedic, radiological, and nuclear medicine literature. Delegates from four European societies (European Bone and Joint Infection Society, European Society of Microbiology and Infectious Diseases, European Society or Radiology, and European Association of Nuclear Medicine) defined clinical questions to be addressed, thoroughly reviewed the literature pertinent to each of the questions, and thereby evaluated the diagnostic accuracy of each diagnostic technique. Inclusion of the papers per statement was based on a PICO (Population/problem – Intervention/indicator – Comparator – Outcome) question following the strategy reported by the Oxford Centre for Evidence-based Medicine. For each statement, the level of evidence was graded according to the 2011 review of the Oxford Centre for Evidence-based Medicine. All approved statements were addressed taking into consideration the available diagnostic procedures, patient acceptance, tolerability, complications, and costs in Europe. Finally, a commonly agreed-upon diagnostic flowchart was developed.

Electronic supplementary material

The online version of this article (10.1007/s00259-019-4262-x) contains supplementary material, which is available to authorized users.

A new perspective on current prosthetic joint infection classifications: introducing topography as a key factor affecting treatment strategy

Periprosthetic joint infection (PJI) is a relatively frequent and devastating complication following prosthetic joint implantation. Several classification systems have been presented by various authors and are routinely used in clinical practice to help in early diagnosis and treatment. The most widely accepted classifications of periprosthetic infections rely on the timing of clinical presentation. Unfortunately, these schemes possess important shortcomings which limit their usefulness in clinical practice, as data reported in literature are contrasting, with success rate ranging from 60 to 80%, irrespectively of prosthetic infection timing. An attempt is made by us to update the current knowledge on PJIs by looking them from a different perspective, introducing a topographic principle in their classification. Our approach is based on the theory that identifying the exact location of the bacterial colonization may allow to decide whether to conservatively treat the patient or to perform a more radical intervention. The aim is to improve the understanding of the aetiology of this serious complication, lead to the appropriate treatment strategy according to the stage of the disease thus enhancing the outcomes of surgical management. Such a strategy, if widely accepted, could guide research studies on the management of PJIs. The availability of investigations like scintigraphy could aid in identifying pathogenetic processes and their exact location, which may be missed on conventional radiographs, and could enable orthopaedic surgeons to have a better understanding of PJI patterns.

Charcot Neuroarthropathy: From the Laboratory to the Bedside

BACKGROUND

The diabetic Charcot foot syndrome is a serious and potentially limbthreatening lower-extremity complication of diabetes.

INTRODUCTION

The present review provides a concise account of the advances made over the last twentyfive years in understanding the pathogenesis and management of Charcot neuroarthropathy (CN).

METHODS

In this study, the widely known pathogenetic mechanisms underpinning CN are brought into focus, particularly the role of RANKL/RANK/OPG system and advanced glycation end production in the pathogenesis of CN. Furthermore, other potential triggering factors, namely nitric oxide, endothelial dysfunction, macro calcifications and body weight that influence CN have also been discussed.

RESULTS

The wide range of diagnostic tools available to clinicians for accurate staging of this pathology has been examined, particularly radiological and nuclear medicine imaging. Additionally, the difficult differential diagnosis between osteomyelitis and CN is also elucidated.

CONCLUSION

The review concludes with the comprehensive summary of the major promising therapeutic strategies, including conservative treatment involving orthopedic devices, pharmacological approach, and the most common surgical techniques currently employed in the diagnosis and treatment of this acute disease.

New Imaging, Diagnostic, and Assessment Techniques in Orthopedic Trauma

This article examines new imaging, diagnostic, and assessment techniques that may affect the care of patients with orthopedic trauma and/or infection. Three-dimensional imaging has assisted in fracture assessment preoperatively, whereas improvement in C-arm technology has allowed real-time evaluation of implant placement and periarticular reduction before leaving the operating room. Advances in imaging techniques have allowed earlier and more accurate diagnosis of nonunion and infection. Innovations in bacteriologic testing have improved the sensitivity and specificity of perioperative and peri-implant infections. It is critical that surgeons remain up to date on the options available for optimal patient care.

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.

SPECT/CT in the Postoperative Painful Knee

This review summarizes the role of SPECT/CT in patients with a painful postoperative knee and describes typical diagnostic criteria in these patients. Pain after knee surgery is common and is influenced by the underlying pathology, the type of surgery, and the patient. Knee joint-preserving surgery includes osteotomy, ligament reconstruction, meniscus surgery, and cartilage repair procedures, often used in combination. Knee arthroplasty procedures consist of unicondylar, patellofemoral, and primary or revision total knee prosthesis. In patients with pain after knee joint-preserving surgery, MRI remains the reference standard. After ligament reconstruction, CT can evaluate postoperative tunnel positioning, and bone SPECT/CT can contribute by assessing overloading or biodegradation problems. After meniscal or cartilage surgery, SPECT/CT can be particularly helpful to identify compartment overloading or nonhealing chondral or osteochondral lesions as cause of pain. SPECT/CT arthrography can assess cartilage damage at an early stage due to altered biomechanical forces. After corrective osteotomy of the knee, SPECT/CT can reveal complications such as overloading, nonunion, or patellofemoral problems. After arthroplasty, conventional radiographs lack both sensitivity to detect aseptic loosening and specificity in differentiating aseptic from infectious loosening. Secondly, hardware-induced artifacts still hamper CT and MRI, despite improving and increasingly available metal artifact reduction techniques. Bone scintigraphy is a proven useful adjunct to conventional radiography and MRI to reveal the pain generator and is less hampered by artifacts from metallic implants compared with CT and MRI. Nevertheless, the optimal imaging strategy in evaluating complications after knee arthroplasty is still a matter of debate. Although the evidence of the use of BS SPECT/CT is still limited, it is growing steadily. In particular, recent data on specific uptake patterns in tibial and femoral zones after total knee arthroplasty and the impact of integrating biomechanics into the assessment of SPECT/CT appear promising, but more research is needed.

The role of hybrid bone SPECT/CT imaging in the work-up of the limping patient: a symptom-based and joint-oriented review

A vast spectrum of lower limb bone and joint disorders (hip, knee, ankle, foot) present with a common clinical presentation: limping. Too often this symptom generates an inefficient cascade of imaging studies. This review attempts to optimise the diagnostic effectiveness of bone scintigraphy using the hybrid SPECT/CT technique in relation to the diagnostic clues provided by other imaging modalities, discusses the appropriate clinical indications, optimal scintigraphic procedures and illustrates updated image pattern-oriented reporting. Frequent lower limb bone and joint pathologies that can now be reliably diagnosed using hybrid bone SPECT/CT imaging will be reviewed. Bone SPECT/CT can be an effective problem-solving tool in patients with persistent limping when careful history taking, clinical examination, and first-line imaging modalities fail to identify the underlying cause.

99mTc-prulifloxacin in artificially infected animals

Aim: The radiosynthesis of 99mTc-Prulifloxacin (99mTc-PRN) was assessed in terms of stability, binding with Staphylococcus aureus (S. aureus), biodistribution in rats (RT) and scintigraphic profile in rabbits (RB). Animals, material, methods: 99mTc-PRN was synthesized by mixing 25 μg of stannous fluoride (SnF2) with 18.5 MB of sodium pertechnetate. Thereafter, 0.5 mg of the prufloxacin (PRN) was added to the reaction mixture and the pH was set at 5.1 with 0.01 mol/l HCl. The reaction mixture was incubated at room temperature. The same process was repeated by increasing the concentration of the stannous fluoride from 25 to 250 μg, sodium pertechnetate from 18,5 to 185 MBq and the PRN from 0.5 to 5 mg. The radiochemical stability of the 99mTc-PRN was investigated in higher concentration of the cystein. In-vitro binding investigation was performed using living and heat killed S. aureus to verify specificity of the 99mTc-PRN. Biodistribution was evaluated in artificially infected rats and scintigraphic precision in rabbits at different interval. Results: The 99mTc-RPN prepared by mixing 2 mg of PRN, 74 MBq sodium pertechnetate, 100 μg stannous fluoride at pH 5.4, appeared to be more than 90% stable with a maximum radiochemical yield of 98.15 ± 0.25% at 30 min. The 99mTc-PRN showed higher stability in serum and satisfactory in-vitro binding to living as compared to heat killed S. aureus. 14.25 ± 0.15% of the injected dose was accumulated in the infected muscle of the model RT. Infected to normal muscle ratio was 5.12 and inflamed to normal muscle was 1.2. The biodistribution was validated by the scintigraphic localization of infection in rabbits. Conclusion: This investigation of 99mTc-PRN confirmed its momentous radiochemical immovability in saline, serum, preferential in-vitro binding to living bacteria, higher uptake in the infected muscle of model RT and precise localization in the infected muscle of model RB.

68Ga-Pentixafor PET/CT Imaging of Chemokine Receptor CXCR4 in Chronic Infection of the Bone: First Insights

Because of its role in infection and inflammatory processes, the chemokine receptor CXCR4 might be a potent target in imaging of infectious and inflammatory diseases. The aim of this pilot study was to determine whether the CXCR4 ligand ⁶⁸Ga-pentixafor is suitable for imaging chronic infection of the bone. Methods: The study comprised 14 patients with suspected infection of the skeleton who underwent ⁶⁸Ga-pentixafor PET/CT between April 2015 and February 2017 in our facility. ⁶⁸Ga-pentixafor PET/CT results were retrospectively evaluated against a histologic, bacteriologic, and clinical standard. The results were also compared with available bone scintigraphy, white blood cell scintigraphy, and ¹⁸F-FDG PET/CT results. Results:⁶⁸Ga-pentixafor PET/CT was positive in 9 of 14 patients. Diagnoses included osteitis or osteomyelitis of peripheral bone, osteomyelitis of the maxilla, and infected endoprostheses. Target-to-background ratios were 5.1-15 (mean, 8.7). Eight of 9 cases were true-positive as confirmed by pathology, bacteriology, or clinical observation. All negative cases were confirmed as true-negative by other imaging modalities and follow-up. Conclusion: Imaging of CXCR4 expression with ⁶⁸Ga-pentixafor PET/CT appears suitable for diagnosing chronic infection of the skeleton. The findings of this study reveal a possible diagnostic gain in suspected chronic infections that are difficult to diagnose by other imaging modalities.

Accuracy of diagnostic imaging modalities for peripheral post-traumatic osteomyelitis - a systematic review of the recent literature

AIMS

Post-traumatic osteomyelitis (PTO) is difficult to diagnose and there is no consensus on the best imaging strategy. The aim of this study is to present a systematic review of the recent literature on diagnostic imaging of PTO.

METHODS

A literature search of the EMBASE and PubMed databases of the last 16 years (2000-2016) was performed. Studies that evaluated the accuracy of magnetic resonance imaging (MRI), three-phase bone scintigraphy (TPBS), white blood cell (WBC) or antigranulocyte antibody (AGA) scintigraphy, fluorodeoxyglucose positron emission tomography (FDG-PET) and plain computed tomography (CT) in diagnosing PTO were considered for inclusion. The review was conducted using the PRISMA statement and QUADAS-2 criteria.

RESULTS

The literature search identified 3358 original records, of which 10 articles could be included in this review. Four of these studies had a comparative design which made it possible to report the results of, in total, 17 patient series. WBC (or AGA) scintigraphy and FDG-PET exhibit good accuracy for diagnosing PTO (sensitivity ranged from 50-100%, specificity ranged from 40-97% versus 83-100% and 51%-100%, respectively). The accuracy of both modalities improved when a hybrid imaging technique (SPECT/CT & FDG-PET/CT) was performed. For FDG-PET/CT, sensitivity ranged between 86 and 94% and specificity between 76 and 100%. For WBC scintigraphy + SPECT/CT, this is 100% and 89-97%, respectively.

CONCLUSIONS

Based on the best available evidence of the last 16 years, both WBC (or AGA) scintigraphy combined with SPECT/CT or FDG-PET combined with CT have the best diagnostic accuracy for diagnosing peripheral PTO.

Radiologic Approach to Musculoskeletal Infections

Imaging is often used to establish a diagnosis of musculoskeletal infections and evaluate the full extent and severity of disease. Imaging should always start with radiographs, which provide an important anatomic overview. MRI is the test of choice in most musculoskeletal infections because of its superior soft tissue contrast resolution and high sensitivity for pathologic edema. However, MRI is not always possible. Alternative imaging modalities including ultrasound scan, computed tomography, and radionuclide imaging may be used. This article reviews the individual imaging modalities and discusses how specific musculoskeletal infections should be approached from an imaging perspective.

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.

Spectrum of Benign Articular and Periarticular Findings at FDG PET/CT

Whole-body fluorine 18 fluorodeoxyglucose (FDG) positron-emission tomography (PET)/computed tomography (CT) is performed primarily for oncologic indications; however, FDG uptake is not specific for malignancy. Herein we focus on causes of increased FDG uptake in and around joints, as lesions in these locations are commonly benign. A combination of primary intra-articular processes and osseous processes that may occur near the joint space will be discussed. Causes of intra-articular and periarticular increased FDG activity can be broadly divided into infectious, inflammatory, degenerative, and benign neoplastic categories. A familiarity with the full range of these processes is important to avoid misinterpretation, in turn decreasing unnecessary follow-up studies, procedures, and treatments. Differentiation from malignancy is often possible on the basis of a different level of FDG activity, divergent response to therapy, or differing changes over time, in comparison with a patient's known primary cancer. Recognizing an intra-articular lesion location can also be critical, as intra-articular metastases are rare. In some cases, benign FDG-avid articular and periarticular entities have a specific appearance at FDG PET/CT and a correct diagnosis may be made without any additional workup. In most other cases, comparison with prior studies and/or additional imaging can afford an accurate diagnosis. This review is meant to introduce the reader to a spectrum of benign FDG-avid articular and periarticular processes that may be encountered at oncologic FDG PET/CT to increase confidence and diagnostic accuracy. (©)RSNA, 2016.