Combined labeled leukocyte and technetium 99m sulfur colloid bone marrow imaging for diagnosing musculoskeletal infection

Free TcO 4- in 99m Tc-PSMA Scan : A Case Report and Review of an Old Pitfall in the New Era of Modern Imaging

ABSTRACT

In a recent 99m Tc-HYNIC-PSMA study conducted at our department, we examined 2 patients with prostate cancer referred for initial staging on the same day. The whole-body scans revealed radiotracer uptake in the gastric mucosa and thyroid glands, alluding to high levels of free TcO 4- in the injected vial. The scans were repeated after confirming acceptable radiopharmaceutical purity of 97% (normal range, 95%-100%). Interestingly, 1 patient had liver metastases at presentation, which remained non-PSMA-avid after repeating the scan. We have reviewed this pitfall, which has been reported with many radiotracers, yet not reported with PSMA tracers.

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.

Current Trends in Total Ankle Replacement

Ankle arthritis can result in significant pain and restriction in range of motion. Total ankle replacement (TAR) is a motion-preserving surgical option used as an alternative to total ankle arthrodesis to treat end-stage ankle arthritis. There are several generations of TAR techniques based on component design, implant material, and surgical technique. With more recent TAR implants, an attempt is made to minimize bone resection and mirror the native anatomy. There are more than 20 implant devices currently available. Implant survivorship varies among prosthesis types and generations, with improved outcomes reported with use of the more recent third- and fourth-generation ankle implants. Pre- and postoperative assessments of TAR are primarily performed by using weight-bearing radiography, with weight-bearing CT emerging as an additional imaging tool. Preoperative assessments include those of the tibiotalar angle, offset, and adjacent areas of arthritis requiring additional surgical procedures. US, nuclear medicine studies, and MRI can be used to troubleshoot complications. Effective radiologic assessment requires an understanding of the component design and corresponding normal perioperative imaging features of ankle implants, as well as recognition of common and device-specific complications. General complications seen at radiography include aseptic loosening, osteolysis, hardware subsidence, periprosthetic fracture, infection, gutter impingement, heterotopic ossification, and syndesmotic nonunion. The authors review several recent generations of TAR implants commonly used in the United States, normal pre- and postoperative imaging assessment, and imaging complications of TAR. Indications for advanced imaging of TAR are also reviewed. ©RSNA, 2023 Supplemental material is available for this article. Test Your Knowledge questions for this article are available through the Online Learning Center.

Molecular Imaging of Periprosthetic Joint Infections

Infection is an infrequent complication of lower extremity prosthetic joint surgery. Approximately one third develop within 3 months (early), another third within 1 year (delayed), and the remainder more than 1 year (late) after surgery. The diagnosis of periprosthetic joint infection is not always straightforward. Pain, the most common symptom, is present in 90%-100% of patients. The presence of fever is more variable, ranging from less than 5% to more than 40% of patients with infection. Erythema and joint swelling are often present in acute infections, but are less common in chronic infections. Erythrocyte sedimentation rate, C-reactive protein and interleukin-6 levels are useful "rule out" tests, while peripheral blood leukocyte count and serum tumor necrosis factor α are not helpful. The diagnosis of periprosthetic joint infection often requires a combination of blood, synovial fluid, and tissue sample tests, as well as imaging. Plain radiographs lack sensitivity and specificity. Molecular imaging is useful for evaluating painful joint replacements. Bone scintigraphy is most useful as a screening test. If it is negative then infection and aseptic loosening are unlikely. Combined labeled leukocyte/bone marrow imaging is a very specific test for diagnosing lower extremity joint arthroplasty infection; sensitivity is more variable. Despite more than two decades of investigation, there still is no consensus on the value of ¹⁸F-FDG for diagnosing periprosthetic joint infection. Differing test probabilities, an inability to discriminate between infection and inflammation secondary to physiologic reactions, and lack of standardized interpretative criteria are obstacles to incorporating ¹⁸F-FDG into the routine diagnostic imaging workup of periprosthetic joint infection. Preliminary results for gallium-68 citrate, fluorine-18, and technetium-99m labeled antimicrobial fragments are encouraging but no large scale trials with these agents have been conducted. Limited data suggest that labeled leukocyte/bone marrow SPECT/CT and ¹⁸F-FDG-PET/CT are specific but not sensitive for diagnosing periprosthetic infection of shoulder arthroplasties. There are minimal data on molecular imaging for monitoring treatment response in periprosthetic infections.

The Use of Hexapod External Fixation in the Management of Charcot Foot and Ankle Deformities

Charcot neuroarthropathy (CN) and its sequela is a disabling pathology in the foot and ankle. The 2-stage computer hexapod-assisted technique is an effective tool to address midfoot Charcot and ankle-hindfoot deformities to restore function and decrease the risk of amputation secondary to ulceration and infection. Although this is not the only technique available, it is an excellent option in cases with significant angular deformity or subluxation, need to reduce shortening of the foot, and in the presence of soft tissue defects, with or without concurrent soft tissue or bone infection.

ACR Appropriateness Criteria® Imaging After Shoulder Arthroplasty: 2021 Update

Shoulder arthroplasty is a common orthopedic procedure with a complication rate reported to be as high as 39.8% and revision rates as high as 11%. Symptoms related to postoperative difficulties include activity-related pain, decreased range of motion, and apprehension. Some patients report immediate and persistent dissatisfaction, although others report a symptom-free postoperative period followed by increasing pain and decreasing shoulder function and mobility. Imaging plays an important role in diagnosing postoperative complications of shoulder arthroplasties. The imaging algorithm should always begin with radiographs. The selection of the next imaging modality depends on several factors, including findings on the initial imaging study, clinical suspicion of an osseous versus soft-tissue injury, and clinical suspicion of infection.The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Radiolabeled nanomaterials for biomedical applications: radiopharmacy in the era of nanotechnology

BACKGROUND

Recent advances in nanotechnology have offered new hope for cancer detection, prevention, and treatment. Nanomedicine, a term for the application of nanotechnology in medical and health fields, uses nanoparticles for several applications such as imaging, diagnostic, targeted cancer therapy, drug and gene delivery, tissue engineering, and theranostics.

RESULTS

Here, we overview the current state-of-the-art of radiolabeled nanoparticles for molecular imaging and radionuclide therapy. Nanostructured radiopharmaceuticals of technetium-99m, copper-64, lutetium-177, and radium-223 are discussed within the scope of this review article.

CONCLUSION

Nanoradiopharmaceuticals may lead to better development of theranostics inspired by ingenious delivery and imaging systems. Cancer nano-theranostics have the potential to lead the way to more specific and individualized cancer treatment.

The Role of Nuclear Medicine Imaging with 18F-FDG PET/CT, Combined 111In-WBC/99mTc-Nanocoll, and 99mTc-HDP SPECT/CT in the Evaluation of Patients with Chronic Problems after TKA or THA in a Prospective Study

Background: The aim of this prospective study was to assess the diagnostic value of nuclear imaging with ¹⁸F-FDG PET/CT (FDG PET/CT), combined ¹¹¹In-WBC/^99mTc-Nanocoll, and ^99mTc-HDP SPECT/CT (dual-isotope WBC/bone marrow scan) for patients with chronic problems related to knee or hip prostheses (TKA or THA) scheduled by a structured multidisciplinary algorithm. Materials and Methods: Fifty-five patients underwent imaging with ^99mTc–HDP SPECT/CT (bone scan), dual-isotope WBC/bone marrow scan, and FDG PET/CT. The final diagnosis of prosthetic joint infection (PJI) and/or loosening was based on the intraoperative findings and microbiological culture results and the clinical follow-up. Results: The diagnostic performance of dual-isotope WBC/bone marrow SPECT/CT for PJI showed a sensitivity of 100% (CI 0.74–1.00), a specificity of 97% (CI 0.82–1.00), and an accuracy of 98% (CI 0.88–1.00); for PET/CT, the sensitivity, specificity, and accuracy were 100% (CI 0.74–1.00), 71% (CI 0.56–0.90), and 79% (CI 0.68–0.93), respectively. Conclusions: In a standardized prospectively scheduled patient group, the results showed highly specific performance of combined dual-isotope WBC/bone marrow SPECT/CT in confirming chronic PJI. FDG PET/CT has an appropriate accuracy, but the utility of its use in the clinical diagnostic algorithm of suspected PJI needs further evidence.

Novel Application of 18F-NaF PET/CT Imaging for Evaluation of Active Bone Remodeling in Diabetic Patients With Charcot Neuropathy: A Proof-of-Concept Report

Charcot neuropathic osteoarthropathy (CN) is a serious and potentially limb-threatening complication for patients with diabetes mellitus and peripheral arterial disease. In recent decades, nuclear medicine-based approaches have been used for non-invasive detection of CN; however, to date, a positron emission tomography (PET) radionuclide specifically focused on targeted imaging of active bone remodeling has not been explored or validated for patients with CN. The radionuclide 18F-sodium fluoride (NaF) has historically been used as a bone imaging probe due to its high sensitivity for targeting hydroxyapatite and bone turnover, but has not been applied in the context of CN. Therefore, the present study focused on novel application of 18F-NaF PET/computed tomography (CT) imaging to three clinical cases of CN to evaluate active bone remodeling at various time courses of CN. PET/CT imaging in all 3 cases demonstrated focal uptake of 18F-NaF in the bones of the feet afflicted with CN, with bone retention of 18F-NaF persisting for up to 5 years following surgical reconstruction of the foot in two cases. On a group level, 18F-NaF bone uptake in the CN foot was significantly higher compared to the healthy, non-CN foot (p = 0.039). 18F-NaF PET/CT imaging may provide a non-invasive tool for monitoring active bone remodeling in the setting of CN, thereby offering novel opportunities for tracking disease progression and improving treatment and surgical intervention.

Screw penetration of the iliopsoas muscle causing late-onset pain after total hip arthroplasty: A case report

BACKGROUND

Postoperative pain following total hip arthroplasty (THA) may occur in a few patients but may pose a significant challenge to surgeons if the etiology is not identified. Herein, we report the case of a patient who developed late-onset pain following THA due to screw penetration of the iliopsoas tendon.

CASE SUMMARY

We report the case of a 77-year-old man who developed inguinal pain 7 years after THA. While the symptoms resembled that of iliopsoas impingement by the acetabular cup, the pain resolved only when the supplementary acetabular screw protruding through the ilium was decompressed. Decompression was performed using the pararectus approach. The patient was able to ambulate pain-free immediately after surgery.

CONCLUSION

A protruded screw through the ilium may penetrate the iliopsoas muscle, causing pain following THA. Pain may resolve with the decompression of the protruded screw.

Imaging update in arthroplasty

Imaging of metal implants has historically been difficult, regardless of the applied modality. The number of primary arthroplasties is increasing over the years. With it, we expect the number of symptomatic complications to increase as well. Acquiring accurate imaging for diagnosis and treatment planning for these cases is of paramount importance. Significant advancements have been made to reduce artifacts, leading to better imaging representation of arthroplasty. This review article would give a background on the current ways of imaging arthroplasty and metal implants, covering recent advances in imaging techniques.

SPECT/CT in the Evaluation of Suspected Skeletal Pathology

Dedicated multi-slice single-photon emission computed tomography/computed tomography (SPECT/CT) cameras have become widely available and are becoming a mainstay of clinical practice. The integration of SPECT and CT allow for precise anatomic location of scintigraphic findings. Fusion imaging with SPECT/CT can improve both sensitivity and specificity by reducing equivocal interpretation in comparison to planar scintigraphy or SPECT alone. This review article addresses the technique, basic science principles, and applications of integrated SPECT/CT in the evaluation of musculoskeletal pathology.

Hybrid imaging of complicating osteomyelitis in the peripheral skeleton

Diagnosing complicating osteomyelitis (COM) is clinically challenging. Laboratory tests are of limited utility, and other than isolation of the offending organism, diagnostic imaging tests are of paramount importance. Nuclear Medicine techniques play an important role in noninvasive evaluation of osteomyelitis, using both single-photon emission tomography (SPECT) and positron emission tomography (PET) radiopharmaceuticals. It is well-known that those conventional imaging modalities are not performing well in the distinction between soft-tissue and deep bone infection due to the lack of anatomical information. These difficulties have been overcome, to a great extent, with the introduction of in-line SPECT-CT and PET-CT systems which have revolutionized the field of diagnostic medical imaging. Hybrid imaging is especially useful in sites of suspected COM with underlying structural bone alterations. The first clinical studies with these integrated hybrid machines in the field of COM, including metallic implants imaging, are highly promising. In summary, WBC/AGA SPECT-CT and FDG-PET-CT seem to be the most accurate hybrid imaging modality for COM of the peripheral bone. However, there are still false positives, especially in aseptic tibial nonunions and/or metallic implants, as well as in the immediate postoperative setting. Furthermore, there is a lack of well-designed large multicentre prospective studies. Hopefully, in the future, the complementary use of morphological and functional hybrid imaging modalities may overcome some of the challenges faced in the assessment of COM.

Diagnosing a periprosthetic shoulder infection: A systematic review

Introduction

The aim of this study was to systematically review the literature regarding accurate shoulder prosthetic joint infection (PJI) diagnosis.

Methods

Using PRISMA guidelines, we analyzed 25 studies reporting on 5535 patients and 646 infections.

Results

Cutibacterium acnes (C. acnes) cultures were positive in 60% of patients. Serum markers WBC, CRP, ESR, and IL-6 appear to lack diagnostic reliability. Synovial IL-6 and alpha-defensin may be more accurate in detecting infections.

Conclusion

Synovial IL-6 and alpha-defensin appear to have greater utility than serum markers. These may be incorporated into new criteria to accurately diagnose shoulder PJI.

Level of evidence

IV.

Dual-tracer approach vs. dual time-point approach in leukocyte scintigraphy in treatment evaluation of persistent chronic prosthetic joint infection

BACKGROUND

Both dual time-point 99mTc-hexamethylpropylene amine oxime (HMPAO)-leukocyte scintigraphy and dual-tracer 99mTc-HMPAO-leukocyte scintigraphy (with the addition of 99mTc-nanocolloid bone marrow scintigraphy) have been used to diagnose prosthetic joint infection (PJI). A treatment evaluation of persistent PJI using these imaging protocols has yet to be presented.

OBJECTIVE

The purpose of this study was to compare the accuracy of dual time-point 99mTc-HMPAO-leukocyte scintigraphy to the dual-tracer alternative of single time-point 99mTc-HMPAO-leukocyte scintigraphy or single-photon emission computed tomography/computed tomography (SPECT/CT) combined with a 99mTc-nanocolloid bone marrow scintigraphy or SPECT/CT, for treatment evaluation of PJI.

MATERIAL AND METHODS

Thirty-one PJI patients under antibiotic treatment were included in this retrospective study. Examinations were organized into three settings. Setting one used dual time-point approach with delayed (2 h) and late (24 h) planar 99mTc-HMPAO-leukocyte scintigraphy, including both visual and semiquantitative analysis. Setting two used delayed (2 h) planar 99mTc-HMPAO-leukocyte scintigraphy combined with 99mTc-nanocolloid bone marrow scintigraphy and for setting three SPECT/CT replaced planar imaging.

RESULTS

Accuracy was 0.68 for visual evaluation and 0.55 for semiquantitative evaluation of setting one; 0.71 for setting two; and 0.68 for setting three. Sensitivity was 0.54 for visual evaluation and 0.31 for semiquantitative evaluation of setting one; 0.38 for setting two; and 0.46 for setting three. Specificity was 0.78 for visual evaluation and 0.72 for semiquantitative evaluation of setting one; 0.94 for setting two; and 0.83 for setting three.

CONCLUSION

No significant difference in accuracy, sensitivity, or specificity between the approaches for treatment evaluation of suspected persistent PJI in the hip or knee was observed.

[Diagnostic Imaging for Infections of the Hand]

Clinical signs of an infection of the hand can be subtle initially or in a chronic state. But even in a progressive stadium it might be difficult to define an involvement of soft tissue, joint or bone. This review article addresses the diagnostic options of radiologic imaging. Radiographs of the affected region are the basic diagnostics. Sonographics provides information about an abscess or effusion versus diffuse edema and phlegmon. Both are in most situations promptly available. In chronic cases and unclear findings, MRI is of value. With bone involvement and an implant related osteomyelitis suspected, CT is the most valid method.

Infected Nonunion of the Tibia Due to Paenibacillus turicensis in a Healthy Young Adult After an All-Terrain Vehicle Accident

We present the case of a 19-year-old man with an open fracture of the tibia and fibula secondary to an accident with an all-terrain vehicle. He underwent operative excisional irrigation, debridement, and fixation on the day of injury. His course was complicated by nonunion of the tibia fracture. Infection is a common factor in fracture nonunion, even in patients who receive appropriate surgical and antimicrobial management. Paenibacillus turicensis, an organism adapted to survive in the environment via spore formation, was responsible for nonunion in our patient. A brief discussion of this unusual organism, fracture nonunion, and the role of infection in etiology of nonunion follows.

Non-radioactive and sensitive tracking of neutrophils towards inflammation using antibody functionalized magnetic particle imaging tracers

White blood cells (WBCs) are a key component of the mammalian immune system and play an essential role in surveillance, defense, and adaptation against foreign pathogens. Apart from their roles in the active combat of infection and the development of adaptive immunity, immune cells are also involved in tumor development and metastasis. Antibody-based therapeutics have been developed to regulate (i.e. selectively activate or inhibit immune function) and harness immune cells to fight malignancy. Alternatively, non-invasive tracking of WBC distribution can diagnose inflammation, infection, fevers of unknown origin (FUOs), and cancer. Magnetic Particle Imaging (MPI) is a non-invasive, non-radioactive, and sensitive medical imaging technique that uses safe superparamagnetic iron oxide nanoparticles (SPIOs) as tracers. MPI has previously been shown to track therapeutic stem cells for over 87 days with a ~200 cell detection limit. In the current work, we utilized antibody-conjugated SPIOs specific to neutrophils for in situ labeling, and non-invasive and radiation-free tracking of these inflammatory cells to sites of infection and inflammation in an in vivo murine model of lipopolysaccharide-induced myositis. MPI showed sensitive detection of inflammation with a contrast-to-noise ratio of ~8-13.

Handling of Doubtful WBC Scintigraphies in Patients with Suspected Prosthetic Joint Infections

Despite the application of EANM recommendations for radiolabelled white-blood-cells (WBC) scintigraphy, some cases still remain doubtful based only on visual analysis. The aim of this study was to investigate the role of semi-quantitative analysis and bone marrow scan (BMS) in solving doubtful cases. We retrospectively evaluated all [^99mTc]HMPAO-WBC scintigraphies performed, in the last 7 years, for a suspected monolateral prosthetic joint infection (PJI). In doubtful cases, we used five different thresholds of increase of target-to-background (T/B) ratio, between delayed and late images, as criteria of positivity (5%, 10%, 15%, 20% and 30%). BMS were also analysed and sensitivity, specificity and accuracy of different methods were calculated according to final diagnosis. The sensitivity, specificity and accuracy were, respectively, 77.8%, 43.8% and 53.0% for the cut-off at 5%; 72.2%, 66.7% and 68.2% for the cut-off at 10%; 66.7%, 75.0% and 72.7% for the cut-off at 15%; 66.7%, 85.4% and 80.3% for the cut-off at 20%; 33.3%, 93.8% and 77.3% for the cut-off at 30%. BMS provided a significantly higher diagnostic performance than 5%, 10% and 15% thresholds. Conversely, we did not observe any statistically significant difference between BMS and the cut-off of more than 20%. Therefore, doubtful cases should be analysed semi-quantitatively. An increase in T/B ratio of more than 20% between delayed and late images, should be considered as a criterion of positivity, thus avoiding BMS.

Nuclear Imaging of Bacterial Infection: The State of the Art and Future Directions

Increased mortality rates from infectious diseases is a growing public health concern. Successful management of acute bacterial infections requires early diagnosis and treatment, which are not always easy to achieve. Structural imaging techniques such as CT and MRI are often applied to this problem. However, these methods generally rely on secondary inflammatory changes and are frequently not specific to infection. The use of nuclear medicine techniques can add crucial complementary information, allowing visualization of infectious pathophysiology beyond morphologic imaging. This review will discuss the current structural and functional imaging techniques used for the diagnosis of bacterial infection and their roles in different clinical scenarios. We will also present several new radiotracers in development, with an emphasis on probes targeting bacteria-specific metabolism. As highlighted by the current coronavirus disease 2019 epidemic, caused by the novel severe acute respiratory syndrome coronavirus 2, similar thinking may apply in imaging viral pathogens; for this case, prominent effects on host proteins, most notably angiotensin-converting enzyme 2, might also provide worthwhile imaging targets.

Should scintigraphy be completely excluded from the diagnosis of periprosthetic joint infection?

AIM

To analyse the diagnostic performance of bone and leukocyte scintigraphy for periprosthetic joint infection before excluding the test from routine practice, and to analyse the possible benefit of bone marrow scintigraphy in inconclusive cases.

MATERIALS AND METHODS

From 2012 to 2018, all patients with a total hip or knee arthroplasty who had a bone and leukocyte scintigraphy performed and underwent revision surgery were included. Bone marrow scintigraphy was indicated only in cases in which bone and leukocyte scintigraphy were inconclusive. Diagnosis of periprosthetic joint infection was confirmed by positive intraoperative cultures after revision surgery.

RESULTS

A total of 105 patients were included. Eighteen patients had total hip arthroplasties (18.1%) and 86 had total knee arthroplasties (81.9%). Mean age was 74 years. Nineteen cases were diagnosed with a periprosthetic joint infection. Bone and leukocyte scintigraphy had 64% sensitivity and 97% specificity. Bone marrow scintigraphy increased sensitivity and specificity to 88% and 100%, respectively.

CONCLUSION

Bone and leukocyte scintigraphy possesses high sensitivity and specificity for the diagnosis of chronic periprosthetic joint infection. The additional use of bone marrow scintigraphy significantly increases diagnostic performance. For these reasons, bone scintigraphy is reserved for inconclusive cases of chronic periprosthetic joint infection.

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

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

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.

Molecular Imaging of Infection: The First 50 Years

Despite significant advances in the understanding of microorganisms and an increased availability of antimicrobial therapy, infection remains a major cause of morbidity and mortality. The diagnosis can be challenging and imaging studies often are used for confirmation and localization. For nearly 50 years, molecular imaging agents have played an important role in the diagnosis of infection. Gallium-67 citrate was perhaps the first molecular imaging agent used for diagnosing and localizing infection. Poor imaging characteristics, along with a lack of specificity, and the long (usually 48-72 hours) interval between administration and imaging motivated investigators to search for alternatives. Currently the role of ⁶⁷Ga is limited to differentiating acute tubular necrosis from interstitial nephritis and as an alternative to ¹⁸F-FDG for indications, such as sarcoid, spondylodiscitis, and fever of unknown origin, when the latter is not available. The development, in the mid-1970s, of techniques for radiolabeling leukocytes that subsequently migrate to foci of infection was a significant advance and labeled leukocyte imaging still has a preeminent role in molecular imaging of infection. There are significant disadvantages to in-vitro labeled leukocyte imaging. Efforts devoted to developing in-vivo leukocyte labeling methods, however, met with only limited success. Over the past 20 years ¹⁸F-FDG has established itself as the molecular imaging agent of choice for fever of unknown origin, vasculitis, sarcoid, and spondylodiscitis. As useful as these agents are, their uptake is based on the host response to infection, not infection itself. Previous attempts at developing infection specific agents, including radiolabeled antibiotics, antibiotics, and vitamins like biotin were limited by poor results and/or limited availability and so investigators continue to focus on developing infection specific molecular imaging agents. Initial results with radiolabeled nucleoside analogs, sugars, and amino acids, and a renewed interest in radiolabeled antibiotics for both diagnosis and monitoring treatment are exciting and hold great promise for the future.

Clinical Applications for Radiotracer Imaging of Lower Extremity Peripheral Arterial Disease and Critical Limb Ischemia

Peripheral arterial disease (PAD) is an atherosclerotic occlusive disease of the non-coronary vessels that is characterized by lower extremity tissue ischemia, claudication, increased prevalence of lower extremity wounds and amputations, and impaired quality of life. Critical limb ischemia (CLI) represents the severe stage of PAD and is associated with additional risk for wound formation, amputation, and premature death. Standard clinical tools utilized for assessing PAD and CLI primarily focus on anatomical evaluation of peripheral vascular lesions or hemodynamic assessment of the peripheral circulation. Evaluation of underlying pathophysiology has traditionally been achieved by radiotracer-based imaging, with many clinical investigations focusing on imaging of skeletal muscle perfusion and cases of foot infection/inflammation such as osteomyelitis and Charcot neuropathic osteoarthropathy. As advancements in hybrid imaging systems and radiotracers continue to evolve, opportunities for molecular imaging of PAD and CLI are also emerging that may offer novel insight into associated complications such as peripheral atherosclerosis, alterations in skeletal muscle metabolism, and peripheral neuropathy. This review summarizes the pros and cons of radiotracer-based techniques that have been utilized in the clinical environment for evaluating lower extremity ischemia and common pathologies associated with PAD and CLI.

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.

Radiological Imaging Evaluation of the Failing Total Hip Replacement

Total hip replacements (THR) have been performed in the UK from the 1960s and since then we have seen surgical techniques, the design of implants, and imaging modalities rapidly develop. This paper will aim to review the different complications and imaging appearance which help to evaluate each problem. As for all investigations for bone and joints, a radiograph is the first imaging to be performed for any patient with a THR and can detect a majority of complications. CT is relatively low-cost, simple to perform and easily available making it an excellent tool to supplement radiographs when trying to evaluate a hip prosthesis. Single photon emission computed tomography with CT (SPECT-CT) is an emerging modality which has shown to combine the sensitivity that bone scintigraphy offers with the high specificity of CT. SPECT imaging also has the advantage of showing the bone's metabolic activity and is less prone to metal artifact than Magnetic resonance imaging (MRI). MRI has evolved to become an important diagnostic tool for the evaluation of THR in the post-operative period. Optimized pulse sequences and metal artifact reduction techniques have made MRI a useful tool in diagnosis of soft tissue abnormalities and is particularly useful in identifying adverse local tissue reactions in metal on metal implants. CT and MRI are accurate in identifying the diagnosis of most causes of THR complications except infection. Research confirms that leukocyte-marrow scintigraphy is the modality of choice for accurately diagnosing prosthetic joint infection and reassures us of its superiority over other nuclear medicine imaging. However, due to the limited availability and increased costs when performing leukocyte-marrow scintigraphy, CT and SPECT-CT would be a more preferred option when suspecting prosthesis infection. Ultrasound (US) has a limited role in the assessment of most THR complications but can be useful to identify peri-prosthetic fluid collections and the presence of soft tissue sinus tracts. Being aware of the imaging modalities that are available to orthopedic surgeons, and discussing these challenging cases with specialist radiologists will enable optimal management of THR complications.

Labeled white blood cell/bone marrow single-photon emission computed tomography with computed tomography fails in diagnosing chronic periprosthetic shoulder joint infection

BACKGROUND

Shoulder periprosthetic joint infections (PJI) caused by low-virulent bacteria pose a diagnostic challenge. Combined labeled leukocyte (WBC) and technetium 99m sulfur colloid bone marrow imaging (WBC/BM) is considered the radionuclide imaging gold standard for diagnosing lower limb PJI. However, it is laborious and expensive to perform, and documentation on shoulder arthroplasties is lacking. This study investigated WBC/BM single-photon emission computed tomography-computed tomography diagnostic performance in shoulder PJI.

METHOD

All patients with a failed arthroplasty referred to a highly specialized shoulder department were scheduled for a diagnostic program including a WBC/BM. If an arthroplasty was revised, biopsy specimens were obtained and cultured for 14 days. The diagnostic performance of WBC/BM imaging was determined using biopsy specimens as a reference.

RESULTS

Of the 49 patients who underwent a WBC/BM scan, 29 (59%) were revised. Infection was present in 11 patients, in whom 2 WBC/BM scans were true positive. The WBC/BM scan in 9 patients was false negative. The remaining 18 patients all had a true negative WBC/BM scan. WBC/BM showed a sensitivity 0.18 (95% confidence interval [CI], 0.00-0.41) and specificity 1.00 (95% CI, 1.00-1.00) in detecting shoulder PJI. The positive predictive value was 1.00 (95% CI, 1.00-1.00), and negative predictive value was 0.67 (95% CI, 0.49-0.84). No patients infected with Cutibacterium (formerly Propionibacterium) acnes resulted in a positive WBC/BM, nor had they preoperative or perioperative signs of infection.

CONCLUSION

A positive WBC/BM was found only in patients with obvious PJI. Hence, the scan added nothing to the preoperative diagnosis. The WBC/BM single-photon emission computed tomography-computed tomography scan cannot be recommended as a screening procedure when evaluating failed shoulder arthroplasties for possible infection.

Immuno-Imaging to Predict Treatment Response in Infection, Inflammation and Oncology

Background: Molecular nuclear medicine plays a pivotal role for diagnosis in a preclinical phase, in genetically susceptible patients, for radio-guided surgery, for disease relapse evaluation, and for therapy decision-making and follow-up. This is possible thanks to the development of new radiopharmaceuticals to target specific biomarkers of infection, inflammation and tumour immunology. Methods: In this review, we describe the use of specific radiopharmaceuticals for infectious and inflammatory diseases with the aim of fast and accurate diagnosis and treatment follow-up. Furthermore, we focus on specific oncological indications with an emphasis on tumour immunology and visualizing the tumour environment. Results: Molecular nuclear medicine imaging techniques get a foothold in the diagnosis of a variety of infectious and inflammatory diseases, such as bacterial and fungal infections, rheumatoid arthritis, and large vessel vasculitis, but also for treatment response in cancer immunotherapy. Conclusion: Several specific radiopharmaceuticals can be used to improve diagnosis and staging, but also for therapy decision-making and follow-up in infectious, inflammatory and oncological diseases where immune cells are involved. The identification of these cell subpopulations by nuclear medicine techniques would provide personalized medicine for these patients, avoiding side effects and improving therapeutic approaches.

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.

Lengthen, Alignment, and Beam Technique for Midfoot Charcot Neuroarthropathy

Charcot neuroarthropathy is a disabling pathology in the foot and ankle. Midfoot Charcot is most common and results in progressive deformity. We describe a 2-step approach to surgical reconstruction, referred to as the lengthen, alignment, and beam technique. There is an initial surgery involving acute equinus correction through Achilles tendon lengthening and gradual correction with hexapod external fixation to align the deformity, followed by minimally invasive medial and lateral column beaming. This surgical protocol allows for adequate reduction of deformity. The second stage allows for rigid intramedullary fixation extending beyond the pathologic joints via a minimally invasive technique.

Radionuclide bone SPECT/CT in the evaluation of knee pain: comparing two-phase bone scintigraphy, SPECT and SPECT/CT

OBJECTIVE:

To assess the role of single photon emission computed tomography (SPECT/CT) in the evaluation of knee pain as well as comparing bone scintigraphy (BS), SPECT and SPECT/CT, and assessing the incremental value of SPECT/CT.

METHODS:

BS, SPECT and SPECT/CT of patients with knee pain (39 patients, 65 knees, 105 lesions) were directly compared for lesion detection, localisation and characterisation using lesion-based, knee-based and patient-based analyses in this retrospective study.

RESULTS:

Lesion detection: BS (91.4%), SPECT (100%) and SPECT/CT (100%). SPECT and SPECT/CT detected significantly more lesions than BS (p < 0.05). Lesion localisation: BS (38.5-41.7%), SPECT (74.4-83.3%) and SPECT/CT (100%). SPECT localised significantly more lesions than BS; SPECT/CT localised significantly more lesions than BS and SPECT (p < 0.01). Lesion characterisation: BS (23.0-52.1%), SPECT (30.8-56.2%) and SPECT/CT (92.3-96.9%). SPECT/CT characterised significantly more lesions than BS and SPECT (p < 0.01). Characterisation of non-arthropathy lesions: BS (6.25%), SPECT (12.5%) and SPECT/CT (93.75%). SPECT/CT characterised significantly more non-arthropathy lesions than BS and SPECT (p < 0.01). BS and SPECT detected none, while SPECT/CT detected 100% of the causative/contributing/associated conditions that co-existed with osteoarthritis. Therefore SPECT/CT detected not only just osteoarthritis but also the causative/contributing/associated conditions.

CONCLUSION:

SPECT/CT added significant incremental value to BS and SPECT irrespective of whether evaluation was lesion-based, knee-based or patient-based. SPECT/CT represents a viable alternative to MRI, and addition of SPECT/CT to BS and SPECT should be considered in the evaluation of knee pain.

ADVANCES IN KNOWLEDGE:

Incremental value of bone SPECT/CT in knee pain.

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.

One-day protocol versus two-day protocol in acquisition of scintigraphy with "in vitro" labelled white blood cells for diagnosis of osteoarticular infection

INTRODUCTION

It is difficult to determine osteoarticular infection and differentiate inflammation from infection with laboratory and imaging procedures (CT, MRI, US). Labelled white-blood-cell scintigraphy (WBCS) is the nuclear medicine test of choice but it takes two days, sometimes finds it difficult to differentiate soft tissue from bone infection and therefore causes interobserver variability, which decreases its specificity.

OBJECTIVE

To demonstrate the usefulness of the one-day protocol with time decay-corrected acquisition in WBCS to diagnose osteoarticular infection and to reduce interobserver variability. The role of SPECT/CT in WBCS in locating the infected focus was also evaluated.

METHODS

110 patients with suspected osteoarticular infection were studied prospectively. Planar images were obtained with time decay-corrected acquisition at 30min, 4h, 8h and 24h. WBCS planar images were grouped in two protocols: One-day protocol: experts evaluated 30min, 4h and 8h images. Two-day protocol: experts evaluated 30min, 4h and 24h images. Both protocols were classified as: SPECT/CT was performed in 72 patients. Kappa index was calculated to evaluate interobserver variability.

RESULTS

Infection was confirmed in 34 cases. Sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy were 97.1%, 97.4%, 94.3%, 98.7%, and 97.3% for the one-day protocol and 94.1%, 97.4%, 94.1%, 97.4%, and 96.4% for two-days-protocol. SPECT/CT contributed to diagnosis in 45/50 patients with planar WBCS positive. Kappa index: 0.8 for one-day protocol and 0.79 for two-day protocol, respectively.

CONCLUSION

One-day protocol with time decay-corrected acquisition WBCS and SPECT/CT enables early and accurate diagnosis of osteoarticular infection.

White cell and marrow imaging: subtracting uncertainty

A subtraction method for assessments of dual-isotope indium-111 (In)-labelled white cell and Tc-nanocoll was proposed, and following a pilot study was introduced in routine service to improve the confidence of reporters. This technical note describes a simple technique to produce subtraction images from routinely acquired images to investigate and exclude post joint replacement infection. Labelled leucocytes (with In) show areas of increased white cell accumulation, whereas Tc-nanocoll images show bone marrow distribution. Images resulting from the subtraction protocol highlight any areas of white cell activity which is not concurrent with the marrow distribution indicative of infection. Fusion images produced from these images sets also assists in localization of white cell accumulation(s). Key to the success of this technique is the use of simultaneous acquisition of both white cell and marrow images; thus removing any issues with patient movement and/or repositioning. Reporting clinicians convey a clear preference for the inclusion of the subtracted and fused images at clinical review.

What is the Accuracy of Nuclear Imaging in the Assessment of Periprosthetic Knee Infection? A Meta-analysis

BACKGROUND

In the assessment of possible periprosthetic knee infection, various imaging modalities are used without consensus regarding the most accurate technique.

QUESTIONS/PURPOSES

To perform a meta-analysis to compare the accuracy of various applied imaging modalities in the assessment of periprosthetic knee infection.

METHODS

A systematic review and meta-analysis was conducted with a comprehensive search of MEDLINE and Embase^® in accordance with the PRISMA and Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) recommendations to identify clinical studies in which periprosthetic knee infection was investigated with different imaging modalities. The sensitivity and specificity of each imaging technique were determined and compared with the results of microbiologic and histologic analyses, intraoperative findings, and clinical followup of more than 6 months. A total of 23 studies, published between 1990 and 2015, were included for meta-analysis, representing 1027 diagnostic images of symptomatic knee prostheses. Quality of the included studies showed low concerns regarding external validity, whereas internal validity indicated more concerns regarding the risk of bias. The most important concerns were found in the lack of uniform criteria for the diagnosis of a periprosthetic infection and the flow and timing of the included studies. Differences among techniques were tested at a probability less than 0.05 level. Where there was slight overlap of confidence intervals for two means, it is possible for the point estimates to be statistically different from one another at a probability less than 0.05. The z-test was used to statistically analyze differences in these situations.

RESULTS

Bone scintigraphy was less specific than all other modalities tested (56%; 95% CI, 0.47-0.64; p < 0.001), and leukocyte scintigraphy (77%; 95% CI, 0.69-0.85) was less specific than antigranulocyte scintigraphy (95%; 95% CI, 0.88-0.98; p < 0.001) or combined leukocyte and bone marrow scintigraphy (93%; 95% CI, 0.86-0.97; p < 0.001). Fluorodeoxyglucose positron emission tomography (FDG-PET) (84%; 95% CI, 0.76-0.90) was more specific than bone scintigraphy (56%; 95% CI, 0.47-0.64; p < 0.001), and less specific than antigranulocyte scintigraphy (95%; 95% CI, 0.88-0.98; p = 0.02) and combined leukocyte and bone marrow scintigraphy (93%; 95% CI, 0.86-0.97; p < 0.001). Leukocyte scintigraphy (88%; 95% CI, 0.81-0.93; p = 0.01) and antigranulocyte scintigraphy (90%; 95% CI, 0.78-0.96; p = 0.02) were more sensitive than FGD-PET (70%; 95% CI, 0.56-0.81). However, because of broad overlapping of confidence intervals, no differences in sensitivity were observed among the other modalities, including combined bone scintigraphy (93%; 95% CI, 0.85-0.98) or combined leukocyte and bone marrow scintigraphy (80%; 95% CI, 0.66-0.91; p > 0.05 for all paired comparisons).

CONCLUSIONS

Based on current evidence, antigranulocyte scintigraphy and combined leukocyte and bone marrow scintigraphy appear to be highly specific imaging modalities in confirming periprosthetic knee infection. Bone scintigraphy was a highly sensitive imaging technique but lacks the specificity needed to differentiate among various conditions that cause painful knee prostheses. FDG-PET may not be the preferred imaging modality because it is more expensive and not more effective in confirming periprosthetic knee infection.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Indium-111 labeled leukocyte accumulation in extremity soft tissue sarcoma

Nuclear medicine labeled leukocyte whole-body scintigraphy is commonly used to identify a source of infection in a patient with fever of unknown origin. White blood cells can also localize to other sites of inflammation, including sometimes tumors. A patient with a large myxofibrosarcoma in his left forearm was scanned due to chronic low-grade fever and persistent leukocytosis. This case demonstrates focal white blood cell activity in an extremity soft tissue sarcoma.

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.

Diagnostic performance of 18F-FDG-labeled white blood cell PET/CT for cyst infection in patients with autosomal dominant polycystic kidney disease: a prospective study

OBJECTIVES

Cyst infection (CI) is a common problem in patients with autosomal dominant polycystic kidney disease (ADPKD) and the accurate detection of infected cysts is very important. We evaluated the diagnostic performance of fluorine-18 fluorodeoxyglucose-labeled white blood cell (WBC) PET/computed tomography (CT) for detection of infected cysts in patients with ADPKD.

PATIENTS AND METHODS

Seventeen patients with ADPKD (male : female, 6 : 11; age, 53±9 years) and suspected CI were enrolled in this prospective study. Patients were classified as having definite/probable/possible CI. All patients underwent WBC PET/CT within 2 days of starting antibiotic treatment. The degree of WBC accumulation was evaluated qualitatively by nuclear medicine physicians. The diagnostic performance of WBC PET/CT was evaluated by sensitivity, specificity, positive predictive values, and negative predictive values. These values were compared with those generated from CT scans and MRI.

RESULTS

Seven patients were classified as having renal CI (definite 6, probable 1). In this group, WBC PET/CT showed six positive findings and one equivocal finding. Seven patients were diagnosed with possible infection. In this group, WBC PET/CT showed six negative findings and one indeterminate finding. The diagnostic performance of WBC PET/CT showed advantages over CT or MRI scans (sensitivity 85.7%, specificity 87.5%, positive predictive value 85.7%, negative predictive value 87.5%).

CONCLUSION

This prospective study shows that WBC PET/CT can provide an accurate diagnosis of CI in patients with ADPKD.

The Accuracy of Imaging Techniques in the Assessment of Periprosthetic Hip Infection: A Systematic Review and Meta-Analysis

BACKGROUND

Various imaging techniques are used for excluding or confirming periprosthetic hip infection, but there is no consensus regarding the most accurate technique. The objective of this study was to determine the accuracy of current imaging modalities in diagnosing periprosthetic hip infection.

METHODS

A systematic review and meta-analysis of the literature was conducted with a comprehensive search of MEDLINE and Embase to identify clinical studies in which periprosthetic hip infection was investigated with different imaging modalities. The sensitivity and specificity of each imaging technique were determined and compared with the results of microbiological and histological analysis, intraoperative findings, and clinical follow-up of >6 months.

RESULTS

A total of 31 studies, published between 1988 and 2014, were included for meta-analysis, representing 1,753 hip prostheses. Quality assessment of the included studies identified low concerns with regard to external validity but more concerns with regard to internal validity including risk of bias (>50% of studies had insufficient information). No meta-analysis was performed for radiography, ultrasonography, computed tomography, and magnetic resonance imaging because of insufficient available clinical data. The pooled sensitivity and specificity were 88% (95% confidence interval [CI], 81% to 94%) and 92% (95% CI, 88% to 96%), respectively, for leukocyte scintigraphy; 86% (95% CI, 80% to 90%) and 93% (95% CI, 90% to 95%) for fluorodeoxyglucose positron emission tomography (FDG PET); 69% (95% CI, 58% to 79%) and 96% (95% CI, 93% to 98%) for combined leukocyte and bone marrow scintigraphy; 84% (95% CI, 70% to 93%) and 75% (95% CI, 66% to 82%) for antigranulocyte scintigraphy; and 80% (95% CI, 72% to 86%) and 69% (95% CI, 64% to 73%) for bone scintigraphy.

CONCLUSIONS

Of the currently used imaging techniques, leukocyte scintigraphy has satisfactory accuracy in confirming or excluding periprosthetic hip infection. Although not significantly different, combined leukocyte and bone marrow scintigraphy was the most specific imaging technique. FDG PET has an appropriate accuracy in confirming or excluding periprosthetic hip infection, but may not yet be the preferred imaging modality because of limited availability and relatively higher cost.

LEVEL OF EVIDENCE

Diagnostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

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

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