Radionuclide imaging in orthopedic infections

Imaging in osteoarticular infection in adults

BACKGROUND

Osteoarticular infections are uncommon and required a multimodal approach for diagnosis. Imaging forms an important component of this multimodal approach.

OBJECTIVES

In this narrative review, we describe the different imaging modalities, features of osteoarticular infections present on these imaging approaches and recommendations for which imaging modality should be considered in different types of osteoarticular infections.

SOURCES

This narrative review was based on literature review from PubMed and was limited to bacterial infections in adult patients.

CONTENT

Imaging modalities include modalities that provide information on the anatomy or radionuclide imaging that provides information about the metabolic activity of the area of interest. Anatomical imaging includes plain radiographs (X-ray), computed tomography, and magnetic resonance imaging. Radionuclide approaches include three-phase bone scintigraphy, gallium scans, white blood cell scintigraphy, and 18F-fluorodeoxy-glucose positron emission tomography. The optimal radiological modality for diagnosis is influenced by multiple factors, including infection location, presence of metalware, timing of infection from any preceding surgery or fracture, antibiotic use, and patient comorbidities. Local availability of scanning modality, tracer supply, technical expertise, and patient access also influences choice.

IMPLICATIONS

A collaborative approach with imaging, pathology and clinical input in a multidisciplinary setting is paramount for the diagnosis of osteoarticular infections. Increasing research and improvements in technology will further improve the utility and accuracy of imaging approaches for imaging in osteoarticular infections.

Infections of Tumor Prostheses: An Updated Review on Risk Factors, Microbiology, Diagnosis, and Treatment Strategies

Several causes contribute to the high infection rate in tumor prostheses, including extensive tissue dissection and patients' immunosuppression due to the neoplastic disease. Most of these infections develop within the first 2 years following surgery with 70% of them occurring during the first year, while they are often associated with a low pathogen burden. The pathogenesis of infections in tumor prostheses is linked to bacteria developing in biofilms. Approximately half of them are caused by Staphylococcus spp., followed by Streptococcus spp., Enterococcus spp., and Enterobacteriaceae spp., while multiple pathogens may be isolated in up to 25% of the cases, with coagulase-negative Staphylococci (CoNS) and Enterococccus spp. being the most frequent pair. Although early detection and timely management are essential for complete resolution of these challenging infections, prompt diagnosis is problematic due to the highly varying clinical symptoms and the lack of specific preoperative and intraoperative diagnostic tests. Surgical management with one- or two-stage revision surgery is the mainstay for successful eradication of these infections. The recent advances in laboratory diagnostics and the development of biofilm-resistant prostheses over the past years have been areas of great interest, as research is now focused on prevention strategies. The aim of this study is to review and consolidate the current knowledge regarding the epidemiology, risk factors, microbiology, and diagnosis of infections of tumor prostheses, and to review the current concepts for their treatment and outcomes.

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.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

What Is the Value of Component Loosening Assessment of a Preoperatively Obtained Bone Scan Prior to Revision Total Knee Arthroplasty?

BACKGROUND

Bone scintigraphy (BS) is frequently ordered to investigate cause of failure following total knee arthroplasty (TKA). Its correlation of component loosening with intraoperative findings (IFs) at the time of revision TKA (rTKA) has not been well studied. This study investigated correlations between the preoperatively obtained radiologist report (RR) of BS, preoperatively documented surgeon prediction (SP) of component loosening, and operative reports documenting IFs.

METHODS

Our institutional database was retrospectively reviewed for all rTKA done after BS and revealed 96 eligible cases. The RR and SP cohorts were subdivided into all potential combinations of component loosening and were then compared with each other as well as IF. In addition to calculating the percentage correct of RR and SP compared with IF, the levels of agreement between RR and SP were compared using the kappa statistic.

RESULTS

Of the 96 cases, the RR correctly correlated with IF in 35 cases (37%), whereas the SP was correct in 66 cases (69%), indicating the preoperative interpretation of the surgeon regarding component loosening at rTKA was correct more frequently (P < .001). The kappa statistic between RR and IF was only 0.23 (95% confidence interval [CI] = 0.15-0.32), indicating minimal agreement. The kappa statistic between SP and IF was 0.57 (95% = CI 0.46-0.68), indicating weak agreement. Furthermore, the kappa statistic between RR and SP was 0.36 (95% CI = 0.27-0.45), also indicating minimal agreement.

CONCLUSIONS

In rTKA, there is weak agreement regarding component loosening between a radiologist's opinion of a preoperatively obtained bone scan and the surgeon's preoperative interpretation of clinical and radiographic data. While neither reliably accurately predicts what is found at the time of rTKA, the surgeon's preoperative interpretation is more closely correlated with actual IFs of component loosening.

Updates on Diabetic Foot and Charcot Osteopathic Arthropathy

PURPOSE OF REVIEW

Diabetes mellitus affects approximately 30.8 million people currently living in the USA. Chronic diabetes complications, including diabetic foot complications, remain prevalent and challenging to treat. We review clinical diagnosis and challenges providers may encounter when managing diabetic foot ulcers and Charcot neuroarthropathy.

RECENT FINDINGS

Mechanisms controlling these diseases are being elucidated and not fully understood. Offloading is paramount to heal and manage diabetic foot ulcers and Charcot neuroarthropathy. Diabetic foot ulcers recur and the importance of routine surveillance and multidisciplinary approach is essential. Several predictors of failure in Charcot foot include a related diabetic foot ulcer, midfoot or rearfoot location of the Charcot event, and progressive bony changes on interval radiographs. Patients with diabetic foot ulcer and/or Charcot neuroarthropathy are in need of consistent and regular special multidisciplinary care. If not diagnosed early and managed effectively, morbidity and mortality significantly increase.

ICS classification system of infected osteosynthesis: Long-term results

The best treatment strategy for infected osteosyntheses is still debated. While hardware removal or eventually early device exchange may be necessary in most of the cases, temporary hardware retention until fracture healing can be a valid alternative option in others. Aim of the present study is to report the long-term results of 215 patients with infected osteosyntheses, treated according to the ICS (Infection, Callus, Stability) classification in two Italian hospitals. Patients classified as ICS Type 1 (N = 83) feature callus progression and hardware stability, in spite of the presence of infection; these patients were treated with suppressive antibiotic therapy coupled with local debridement in 18.1% of the cases, and no hardware removal until bone healing. Type 2 patients (N = 75) are characterized by the presence of infection and hardware stability, but no callus progression; these patients were treated as Type 1 patients, but with additional callus stimulation therapies. Type 3 patients (N = 57), showing infection, no callus progression and loss of hardware stability, underwent removal and exchange of the fixation device. Considering only the initial treatment, performed according to the ICS classification, at a minimum 5 years follow up, 89.3% achieved bone healing and 93.5% did not show infection recurrence. The ICS classification appears as a useful and reliable tool to help standardizing the decision-making process in treating infected osteosynthesis with the most conservative approach.

Imaging of Degenerative and Infectious Conditions of the Spine

: Imaging is important in the evaluation of patients with degenerative disease and infectious processes. There are numerous conditions that can manifest as low back pain (LBP) or neck pain in a patient, and in many cases, the cause may be multifactorial. Clinical history and physical examination are key components in the evaluation of such patients; however, physical examination has variable sensitivity and specificity. Although studies have demonstrated that uncomplicated acute LBP and/or radiculopathy are self-limited conditions that do not warrant any imaging, neuroimaging can provide clear anatomic delineation of potential causes of the patient's clinical presentation. Various professional organizations have recommendations for imaging of LBP, which generally agree that an imaging study is not indicated for patients with uncomplicated LBP or radiculopathy without a red flag (eg, neurological deficit such as major weakness or numbness in lower extremities, bowel or bladder dysfunction, saddle anesthesia, fever, history of cancer, intravenous drug use, immunosuppression, trauma, or worsening symptoms). Different imaging modalities have a complementary role in the diagnosis of pathologies affecting the spine. In this review, we discuss the standard nomenclature for lumbar disk pathology and the utility of various clinical imaging techniques in the evaluation of LBP/neck pain for potential neurosurgical management. The imaging appearance of spinal infections and potential mimics also is reviewed. Finally, we discuss advanced neuroradiological techniques that offer greater microstructural and functional information.

ABBREVIATIONS

ADC, apparent diffusion coefficientDTI, diffusion tensor imagingDWI, diffusion-weighted imagingDOM, diskitis-osteomyelitisLBP, low back painMRM, magnetic resonance myelographySNA, spinal neuroarthropathySPECT, single-positron emission computed tomographySTIR, short tau inversion recovery.

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.

Bone scan in painful knee arthroplasty: obsolete or actual examination?

ptic loosening, instability and infection are the major causes of TKA failure. For many years, nuclear medicine (NM) imaging was helpful to frame a painful total joint arthroplasty. The differentiation of septic from aseptic prosthetic loosening is critical. The latest AAOS guidelines to detect periprosthetic joint infection (PJI) restrict the role of NM scintigraphy. On the other hand, several studies suggest that NM imaging plays an important role in the evaluation of patients with painful prosthesis, but its specificity in differentiating aseptic loosening from infection is low. Moreover, scintigraphic exams showed different diagnostic accuracy in TKA compared to total hip arthroplasty (THA).

PURPOSE

To assess and discuss current knowledges about the diagnostic value of the various scans in TKA failure alone.

METHODS

We perform a pubmed/medline search to identify all papers published in the literature matching the following key words: "total knee arthroplasty", "bone", "scintigraphy", "imaging", "three-phase", "triple-phase", "99mTc-HDP", "99mTc-MDP", "99mTc-hydroxymethane diphosphonate", and "99m Tc-methylenediphosphonate", "leukocyte scanning", "labeled leukocyte scintigraphy", "antigranulocyte", "nuclear medicine", "septic loosening", "aseptic loosening" and "infection".

RESULTS

Three phases bone scintigraphy results an early diagnostic screening test or part of the preoperative tests for painful TKA and when PJI is suspected. Instead, leukocyte/bone marrow scintigraphy is superior to other scintigraphic tools in diagnosis of TKA infections. Granulocyte scintigraphy, seems to be an excellent choice when the diagnosis is unclear. Moreover, nuclear diagnostic tests showed different diagnostic accuracy between TKA and THA.

CONCLUSIONS

Although nuclear diagnostic tests for THA failure are superior in  diagnostic accuracy compared to TKA, NM scintigraphy is still an effective tool in the identification of chronic, low grade PJI. To date, scintigraphic exams have an higher levels of sensitivity, specificity and accuracy. Currently, leukocyte/bone marrow scintigraphy is considered the gold standard for this aim.  Nevertheless, further studies are needed to assess and improve the accuracy of the scintigraphic exams in order to discriminate the causes of failure for painful TKA.

Infections of the Spine

Pyogenic infections of the bony spinal column and the intervertebral discs are on a steady rise in an aging western population. Despite advanced medical imaging, this clinical entity of devastating consequences if missed, still presents a diagnostic conundrum and is plagued by an unacceptably long diagnostic delay. The aim of this article is to raise awareness of the heterogeneity of spinal infections paralleling the complex structure of the spinal column and neighboring soft tissues. Emphasis is placed on the clinical presentation and management of septic facet joints and psoas muscle abscesses associated with lumbar spondylodiscitis.

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.

Charcot stage 0: A review and consideratons for making the correct diagnosis early

Charcot neuropathic osteoarthropathy (CN) is a rare disease (NIDDK, NIH Summary Report Charcot Workshop, 2008) that causes significant morbidity and mortality for affected patients. The disease can result in severe deformities of the foot and ankle that contribute to the development of ulcerations and amputations. Medical advances have failed to find ways to stop the progression of the disease. However, it is known that early detection of the CN has a substantial impact on patient outcomes. CN in the earliest stage is very difficult to recognize and differentiate from other similar presenting diseases. We intend to outline clinical considerations practitioners can use when evaluating a patient with early stage suspected CN.

Imaging of lumbar spinal surgery complications

Abstract

Lumbar spine surgery for spinal stenosis is a frequently performed procedure and was the fastest growing type of surgery in the US from 1980 to 2000. With increasing surgical invasiveness, postoperative complications also tend to be higher. Cross-sectional imaging techniques (CT and MRI) are more sensitive than radiographs and play an increasingly important role in evaluation of patients with lumbar spine surgery. Their use in patients with metallic implants is somewhat limited by artefacts, which can obscure pathology and decrease accuracy and reader confidence. Metal artefact reduction techniques have been developed, which can significantly improve image quality and enable early detection of postoperative complications. Complications can occur throughout postoperative course. Early complications include hardware displacement, incidental durotomy, postoperative collections—most commonly seroma, and less likely haematoma and/or infection. Incidental durotomy with CSF leak causing intracranial hypotension has characteristic MR brain findings and diagnosis of occult leak sites have been improved with use of dynamic CT myelography. Haematomas, even when compressing the thecal sac, are usually asymptomatic. Early infection, with nonspecific MR findings, can be diagnosed accurately using dual radiotracer studies. Delayed complications include loosening, hardware failure, symptomatic new or recurrent disc herniation, peri-/epidural fibrosis, arachnoiditis, and radiculitis.

Teaching Points

• CT and MRI play an increasingly important role in evaluation of patients with lumbar spine surgery

• Complications can occur throughout the postoperative course and early detection is critical

• Artefact reduction techniques can improve image quality for early and improved detection of complications

2015 Infectious Diseases Society of America (IDSA) Clinical Practice Guidelines for the Diagnosis and Treatment of Native Vertebral Osteomyelitis in Adultsa

These guidelines are intended for use by infectious disease specialists, orthopedic surgeons, neurosurgeons, radiologists, and other healthcare professionals who care for patients with native vertebral osteomyelitis (NVO). They include evidence and opinion-based recommendations for the diagnosis and management of patients with NVO treated with antimicrobial therapy, with or without surgical intervention.

Complementary roles of bone scintigraphy and MR imaging in the detection and long-term follow-up of primary non-Hodgkin's bone lymphoma in a child-case report

The aim of our report is to demonstrate the complementary roles of bone scintigraphy (BS), magnetic resonance imaging (MR), and positron emission tomography using 2-deoxy-2-[18F]fluoro-D-glucose (F-18-FDG PET/CT) in the diagnosis and treatment monitoring of a child with primary non-Hodgkin's lymphoma of bone (PLB). Increased blood flow, high tissue accumulation, and markedly increased uptake on the late BS pointed toward an active bone process in the left femoral region. Bone marrow infiltration of the left femur and cortical sclerosis, which were both demonstrated by MR imaging, were later confirmed as PLB by bone marrow biopsy. The normalizations of the flow and tissue phases of BS a year after treatment and during the entire follow-up were in keeping with inactive disease and clinical remission. However, even 8 years after treatment and complete remission, MR imaging demonstrated persistent unmodified bone marrow alteration and appreciable cortical involvement. A slightly increased metabolic activity of the left femoral epiphysis demonstrated by F-18-FDG PET/CT and mild activity in the same region on delayed BS were demonstrated in the late follow-up. Our results strongly suggest that BS and MR imaging should be included in the diagnostic algorithm of children with undefined bone symptoms. However, mild metabolic activity on the F-18-FDG PET/CT scan could not reliably differentiate between the presence or absence of disease in a patient with PLB in clinical remission.

Diagnostic work-up strategy for periprosthetic joint infections after total hip and knee arthroplasty: a 12-year experience on 320 consecutive cases

Background

Elective knee and hip arthroplasty is followed by infections in currently about 0.5–2.0 % of cases – a figure which is on the increase due to the rise in primary implants. Correct diagnosis early on is essential so that appropriate therapy can be administered. This work presents a retrospective analysis of the diagnoses of patients suffering infections after total hip or knee arthroplasty.

Methods

320 patients with prosthetic joint infection (PJI) following knee or hip arthroplasty were identified. They comprised a) 172 patients with an infection after total hip arthroplasty (THA): 56 % females (n = 96) and 44 % males (n = 76) with a mean age of 70.9 (39–92) years; and 148 patients with an infection after total knee arthroplasty (TKA): 55 % females (n = 82) and 45 % males (n = 66) with a mean age of 70.7 (15–87) years.

Results

Although significantly more TKA than THA patients reported pain, erythema, a burning sensation and swelling, no differences between the two groups were observed with respect to dysfunction, fever or fatigue. However, significant differences were noted in the diagnosis of loosening (THA 55 %, TKA 31 %, p < 0.001) and suspected infection using conventional X-rays (THA 61 %, TKA 29 %, p < 0.001). FDG-PET-CT produced very good results in nearly 95 % of cases. There were no differences between THA and TKA patients regarding levels of inflammation markers. Histological evaluation proved to be significantly better than microbiological analysis.

Summary

The clinical picture may be non-specific and not show typical inflammatory symptoms for a long time, particularly in PJI of the hip. As imaging only provides reliable conclusions after the symptoms have persisted for a long time, morphological imaging is not suitable for the detection of early infections. FDG-PT-CT proved to be the most successful technique and is likely to be used more frequently in future. Nevertheless, there are currently no laboratory parameters which are suitable for the reliable primary diagnosis of PJI. Diagnosis requires arthrocentesis, and the fluid obtained should always be examined both microbiologically and histologically.

Positron emission tomography in spinal infections

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

Imaging and management of postoperative spine infection

Imaging evaluation of postoperative spinal infection is challenging. A systematic approach and keen understanding of multimodality imaging techniques, as well as knowledge of the patient's surgical procedure and clinical presentation, are critical for the radiologist to render an accurate diagnosis. Because of the overlap between diagnostic imaging findings in the postoperative spine and the infected spine, in those situations in which the index of clinical suspicion for spine infection is high, then immediate consideration ought to be given to performing a spine biopsy.

Osteomyelitis of the foot and ankle: diagnosis, epidemiology, and treatment

Osteomyelitis of the foot and ankle is a common, potentially devastating condition with diagnostic and treatment challenges. Understanding the epidemiology and pathogenesis of osteomyelitis can raise clinical suspicion and guide testing and treatments. History and physical examination, laboratory studies, vascular studies, histologic and microbiologic analyses, and various imaging modalities contribute to diagnosis and treatment. Treatment including empiric broad-spectrum antibiotics and surgery should take a multidisciplinary approach to optimize patient factors, ensure eradication of the infection, and restore function. Optimization of vascular status, soft tissues, limb biomechanics, and physiologic state of the patient must be considered to accelerate and ensure healing.

Usefulness of adding SPECT/CT to 99mTc-hexamethylpropylene amine oxime (HMPAO)-labeled leukocyte imaging for diagnosing prosthetic joint infections

OBJECTIVE

This study evaluated the usefulness of adding single-photon emission computed tomography (SPECT)/computed tomography (CT) (SPECT/CT) to technetium Tc 99m (Tc) hexamethylpropylene amine oxime (HMPAO)-labeled leukocyte imaging for diagnosing infections in hip or knee joint prostheses.

METHODS

The Tc-HMPAO-labeled leukocyte scans of 164 patients (71 with hip prostheses and 93 with knee prostheses) with clinically suspected prosthetic infections were reviewed retrospectively. Planar images were taken 4 to 6 and 21 to 26 hours after injecting the labeled leukocytes and SPECT/CT images were obtained 4 to 6 hours after the injection. The final diagnosis of infection was based on pathologic findings (n = 70), bacteriological data (n = 61), or clinical follow-up (n = 33).

RESULTS

Of the 164 patients, 89 patients had a diagnosis of prosthetic joint infections. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy of the planar images alone were 82.0%, 88.0%, 89.0%, 80.5%, and 84.8%, respectively. When the planar images were combined with SPECT, the sensitivity, specificity, PPV, NPV, and diagnostic accuracy were 91.0%, 88.0%, 90.0%, 89.2%, and 89.6%, respectively. When the planar images were combined with SPECT/CT, these values increased further to 93.3%, 93.3%, 94.3%, 92.1%, and 93.3%, respectively. Adding CT to SPECT resulted in a greater increase in sensitivity and specificity for hip prosthesis infections than for knee prosthesis infections. SPECT/CT mainly contributed by precisely localizing the anatomical site of the active inflammatory lesion and by delineating the extent of the lesion after diagnosis with SPECT.

CONCLUSIONS

Single-photon emission computed tomography/CT combined with Tc-HMPAO-labeled leukocyte imaging was useful for diagnosing prosthesis infections, particularly in hip prosthesis infections, as it improved diagnostic accuracy and provided anatomical localization data.

Quantitative simultaneous 111In∕99mTc SPECT-CT of osteomyelitis

PURPOSE

A well-established approach for diagnostic imaging of osteomyelitis (OM), a bone infection, is simultaneous SPECT-CT of 99mTc sulfur colloid (SC) and 111In white blood cells (WBC). This method provides essentially perfect spatial registration of the tracers within anatomic sites of interest. Currently, diagnosis is based purely on a visual assessment-where relative discordance between 99mTc and 111In uptake in bone, i.e., high 111In and low 99mTc, suggests OM. To achieve more quantitative images, noise, scatter, and crosstalk between radionuclides must be addressed through reconstruction. Here the authors compare their Monte Carlo-based joint OSEM (MC-JOSEM) algorithm, which reconstructs both radionuclides simultaneously, to a more conventional triple-energy window-based reconstruction (TEW-OSEM), and to iterative reconstruction with no compensation for scatter (NC-OSEM).

METHODS

The authors created numerical phantoms of the foot and torso. Multiple bone-infection sites were modeled using high-count Monte Carlo simulation. Counts per voxel were then scaled to values appropriate for 111In WBC and 99mTc SC imaging. Ten independent noisy projection image sets were generated by drawing random Poisson deviates from these very low-noise images. Data were reconstructed using the two iterative scatter-compensation methods, TEW-OSEM and MC-JOSEM, as well as the uncorrected method (NC-OSEM). Mean counts in volumes of interest (VOIs) were used to evaluate the bias and precision of each method. Data were also acquired using a phantom, approximately the size of an adult ankle, consisting of regions representing infected and normal bone marrow, within a bone-like attenuator and surrounding soft tissue; each compartment contained a mixture of 111In and 99mTc. Low-noise data were acquired during multiple short scans over 29 h on a Siemens Symbia T6 SPECT-CT with medium-energy collimators. Pure 99mTc and 111In projection datasets were derived by fitting the acquired projections to the sum of 99mTc and 111In contributions, using the known half-lives. Uncontaminated data were scaled and recombined into six datasets with different activity ratios; ten Poisson noise realizations were then generated for each ratio. VOIs in each of the compartments were used to evaluate the bias and precision of each method with respect to reconstructions of uncontaminated datasets. In addition to the simulated and acquired phantom images, the authors reconstructed patient images with MC-JOSEM and TEW-OSEM. Patient reconstructions were assessed qualitatively for lesion contrast, spatial definition, and scatter.

RESULTS

For all simulated and acquired infection phantoms, the root-mean squared-error of measured 99mTc activity was significantly improved with MC-JOSEM and TEW-OSEM in comparison to NC-OSEM reconstructions. While MC-JOSEM trended toward outperforming TEW-OSEM, the improvement was only found to be significant (p<0.001) for the acquired bone phantom in which a wide range of 111In∕99mTc concentration ratios were tested. In all cases, scatter correction did not significantly improve 111In quantitation.

CONCLUSIONS

Compensation for scatter and crosstalk is useful for improving quality, bias, and precision of 99mTc activity estimates in simultaneous dual-radionuclide imaging of OM. The use of the more rigorous MC-based estimates provided marginal improvements over TEW. While the phantom results were encouraging, more subjects are needed to evaluate the usefulness of quantitative 111In∕99mTc SPECT-CT in the clinic.

SPECT/CT with a hybrid camera: a new imaging modality for the functional anatomical mapping of infections

Evaluation of: Bar-Shalom R, Yefremov N, Guralnik L et al. SPECT/CT using (67)Ga and (111)In-labeled leukocyte scintigraphy for diagnosis of infection. J. Nucl. Med. 47(4), 587-594 (2006). Labeled leukocytes and (67)Ga scan have been proved to be useful to image infectious and inflammatory processes. However, it is well known that nuclear imaging lacks precise anatomical landmarks. When highly specific tracers are used, the background activity may be too low to be used as a framework for spatial orientation. To overcome these drawbacks, the hybrid devices combining positron emission tomography/single photon emission computed tomography (SPECT) and computed tomography (CT) have been introduced, thereby providing a precise anatomical-functional correlation. The paper under evaluation highlights the emerging role of hybrid SPECT/CT to image infection with labeled leukocytes and (67)Ga. The authors suggest that fusion imaging can be of paramount value to locate the site of infection and to better define the extent of disease.

Diagnosis of bone infection by complementary role of technetium-99m MDP and technetium-99m hexamethylpropylene-amineoxime-leukocytes

Purpose:

Valuate complementary role of ^99mTc-MDP bone scan and ^99mTechnetium hexamethylpropylene-amineoxime (^99mTc-HMPAO) labeled leukocyte scintigraphy in diagnosis of bone infection.

Patients and Methods:

Ninety one sites suspected to have bone infection were divided in to two groups: Group I 49 sites with current endo-prothesis; and group II 42 sites with no prosthesis. All patients were subjected to serial images of ^99mTc-HMPAO labeled leukocyte (^99mTc-white blood cells (WBCs)), triple phase bone scan (^99mTc-MDP) and plain X-ray, in addition to clinical and bacteriological assessment, together with follow-up.

Results:

The overall sensitivity (Sn) was found to be 34.9%, 95.4%, and 86% for plain X-ray, ^99mTc-MDP, and ^99mTc-WBCs respectively. Concerning specificity (Sp) was found to be 47.9%, 45.8%, and 91.7% respectively for the three imaging modalities. ^99mTc-WBCs showed better Sn, Sp, and accuracy in group I (95%, 93.1% and 93.9%, respectively) compared to 40%, 41.4%, and 40.8% for plain X-ray and 90%, 62%, and 73.5% respectively for ^99mTc-MDP. On the other hand, ^99mTc-MDP proved to have best Sn 100% versus 78.3% and 30.4% for ^99mTc-WBCs and plain X-ray respectively. Yet, Sp and accuracy was found to best for ^99mTc-WBCs (89.5% and 83.3% respectively) compared to 57.9% and 42.9% for plain X-ray and 21.1% and 64.3% for ^99mTc-MDP.

Conclusion:

Combined imaging with ^99mTc-WBCs and ^99mTc-MDP proved to be effective in early detection of bone infection in the presence or absence of prosthesis.

Indexing severity of diabetic foot infection with 99mTc-WBC SPECT/CT hybrid imaging

OBJECTIVE

Management of diabetic foot infection (DFI) has been hampered by limited means of accurately classifying disease severity. New hybrid nuclear/computed tomography (CT) imaging techniques elucidate a combination of wound infection parameters not previously evaluated as outcome prognosticators. Our aim is to determine if a novel standardized hybrid image-based scoring system, Composite Severity Index (CSI), has prognostic value in DFI.

RESEARCH DESIGN AND METHODS

Masked retrospective (99m)Tc-white blood cell (WBC) single photon emission CT (SPECT)/CT image interpretation and independent chart review of 77 patients (101 feet) suspected of DFI-associated osteomyelitis at a large municipal hospital between January 2007 and July 2009. CSI scores were correlated with probability of favorable outcome (no subsequent amputation/readmission after therapeutic intervention) during median 342-day follow-up.

RESULTS

CSI ranged from 0-13. Receiver operating characteristic accuracy for predicting favorable outcome was 0.79 (optimal cutoff CSI, ≤2; odds ratio of therapeutic failure for CSI >2, 15.1 [95% CI 4.4-51.5]). CSI of 0 had a 92% chance of favorable outcome, which fell progressively to 25% as indices rose to ≥7. Image-based osteomyelitis versus no osteomyelitis assessment was less accurate than CSI at predicting outcome (P = 0.016). In patients with intermediate severity (CSI 3-6), treatment failure decreased from 68 to 36% when antibiotic duration was extended to ≥42 days (P = 0.026).

CONCLUSIONS

(99m)Tc-WBC SPECT/CT hybrid image-derived wound infection parameters incorporated into a standardized scoring system, CSI, has prognostic value in DFI.

The Clinical Usefulness of (99m)Tc HMPAO Leukocyte/(99m)Tc Phytate Bone Marrow Scintigraphy for Diagnosis of Prosthetic Knee Infection: A Preliminary Study

PURPOSE

The preferred radionuclide imaging procedure for diagnosing prosthetic joint infection is combined radiolabeled leukocyte/(99m)Tc sulfur colloid bone marrow scintigraphy, which has an accuracy of over 90 %. Unfortunately, sulfur colloid is no longer available in South Korea. In this study, we evaluated the usefulness of (99m)Tc phytate, a substitute for (99m)Tc sulfur colloid, when combined with radiolabeled leukocyte scintigraphy in suspected prosthetic knee infections.

METHODS

Eleven patients (nine women, two men; mean age 72 ± 6 years) with painful knee prostheses and a suspicion of infection underwent both (99m)Tc HMPAO leukocyte scintigraphy (LS) and (99m)Tc phytate bone marrow scintigraphy (BMS). The combined images were interpreted as positive for infection when radioactivity in the LS at the site of clinical interest clearly exceeded that of the BMS (discordant); they were interpreted as negative when the increased activity in the LS was consistent with an increased activity in the BMS (concordant). The final diagnosis was made with microbiological or intraoperative findings and a clinical follow-up of at least 12 months.

RESULTS

Five of eleven patients were diagnosed as having an infected prosthesis. The overall sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy of the combined LS/BMS were 100 %, 83 %, 83 %, 100 % and 91 %, respectively.

CONCLUSION

We find that combined (99m)Tc HMPAO LS/(99m)Tc phytate BMS shows comparable diagnostic performance to other studies utilizing sulfur colloid. Combined (99m)Tc HMPAO LS/(99m)Tc phytate BMS is therefore expected to be an acceptable alternative to combined radiolabeled LS/(99m)Tc sulfur colloid BMS for diagnosing prosthetic knee infections.

Intact versus Fragmented 99mTc-Monoclonal Antibody Imaging of Infection in Patients with Septically Loosened Total Knee Arthroplasty

OBJECTIVE: This prospective study compared the diagnostic accuracy of imaging using an intact murine antigranulocyte antibody 99mTc-besilesomab, and a murine antibody Fab' fragment 99mTc-sulesomab, in patients with suspected septically loosened total knee arthroplasty. METHODS: Images from 20 patients who underwent three-phase bone scintigraphy followed by imaging using 99mTc-besilesomab ( n = 10) or 99mTc-sulesomab ( n = 10) were evaluated and compared. Final diagnosis was determined by microbiological evaluation of aspirated synovial fluid, intraoperative samples through the clinical course, or by long-term follow-up. RESULTS: Prosthesis infection was shown in 18 patients. At 4 and 24 h after intravenous injection, absolute uptake of 99mTc-besilesomab was significantly higher than 99mTc-sulesomab in infected knee joints. Infected-to-healthy knee activity ratios were similar at 4 and 24 h for 99mTc-besilesomab and 99mTc-sulesomab. CONCLUSIONS: Both 99mTc-besilesomab and 99mTc-sulesomab had similar diagnostic accuracy for the detection of septic arthroplasty. If repeated use of immunoscintigraphy is needed for follow-up, 99mTc-sulesomab should be preferred over 99mTc-besilesomab since it is known to be well tolerated and without side effects or incompatibility reactions.

Septic arthritis of unilateral lumbar facet joint with contiguous abscess, without prior intervention

A 40-year-old female patient presented with persistent severe back pain radiating to the right leg, abdominal pain and constipation. Other clinical symptoms included nausea, vomiting and high-grade fever. Clinical examination showed generalised abdominal and lower back tenderness. There was no sensory loss or motor weakness in lower limbs, however investigations showed raised inflammatory markers. Radiographs of the lumbar spine and hip joint were normal. MRI revealed a septic arthritis of the right L3/4 facet joint, associated with a large abscess extending anteriorly to the right paraspinal muscles and posteriorly into the right posterolateral aspect of the epidural space in the central spinal canal, with moderate compression of the dural sac. Unlike any other reported similar case, this septic arthritis developed without prior medical intervention. The patient was treated successfully with ultrasound guided drainage of the facet joint/abscess and antibiotics.

Tc-99m Labeled HMPAO white Blood Cell Scintigraphy in Pediatric Patients

OBJECTIVE

(99m)Tc labeled hexamethylpropylene amine oxime (HMPAO) white blood cell (WBC) scintigraphy is a frequently used option for acute infection, particularly in pediatric patients. This scintigraphy is applied to detect sites of infection/inflammation in patients with fever of unknown origin, to find and follow up osteomyelitis, and to detect suspicion of acute appendicitis. The aim of this retrospective study was to evaluate the value of (99m)Tc-HMPAO labeled WBC scintigraphy in pediatric patients.

MATERIAL AND METHODS

The study was conducted between January 2006 and December 2008 and included 13 patients (5 boys, 8 girls; mean age 6.9±6.2 years). Those patients who had suspicion of bone infection (n=7), fever of unknown origin (n=3), and suspicion of acute appendicitis (n=3) were evaluated retrospectively. (99m)Tc-HMPAO labeled WBC scintigraphy imaging was performed to all patients. Diagnosis was done according to operation and pathological results or clinical follow-up.

RESULTS

(99m)Tc-HMPAO labeled WBC scintigraphy has been found to be true positive in 6 cases, true negative in 6 cases, and false negative in one patient who had fewer unknown origin. The false negative case has been found to have encephalitis with MRI.

CONCLUSION

Leukocyte scintigraphy has been described as a useful diagnostic tool in the diagnosis of suspicion of bone infection, fever of unknown origin and suspicion of acute appendicitis. (99m)Tc-HMPAO labeled WBC scintigraphy is a rapid and very accurate method for detecting those pathologies. Our results showed that WBC scintigraphy might be reliably used for diagnosis of suspected bone infection and acute appendicitis, fever of unknown origin, and acute appendicitis, in pediatric patient population.

CONFLICT OF INTEREST

None declared.

'Fungal spondylodiscitis in a non-immunocompromised patient'

Spondylodiscitis is an inflammatory disease, usually infectious, of one or more vertebral bodies and of corresponding intervertebral discs. The fungal aetiology is rare (less than 5% of cases), affecting mostly immunocompromised individuals. It is often a delayed diagnosis by the indolence of symptoms, presenting itself as a serious infection, which may result in important functional consequences. The authors present the case of a 75-year-old male, with constitutional complaints and intense back pain. Prior recent history of left hemicolectomy due to diverticulitis with multiple surgical complications, resulted in prolonged intensive care unit hospitalisation, and, later on, an episode of fungal endophthalmitis. The diagnosis of spondylodiscitis L5/S1 was performed by MRI. The patient underwent surgical disco-vertebral debridement and isolation of a Candida albicans was seen in the collected surgical material. No evidence of an immunossupressive status was found. Treatment was complemented with liposomal amphotericin B in the maximum recommended dose.

Management of bone infections in adults: the surgeon's and microbiologist's perspectives

Bone infection in adults is a potentially devastating complication following trauma or surgery. The clinician should diagnose osteomyelitis based on certain clinical manifestations and on laboratory and imaging findings. For pathogen identification, the treating surgeon should take appropriate tissue samples. Close collaboration with microbiologists is of paramount importance to dictate the appropriate duration and type of antibiotics to be administered. Treatment of acute osteomyelitis requires surgical debridement and prolonged course of antibiotics. Debate exists regarding the maintenance or the removal of any internal fixation device. Treatment of chronic osteomyelitis is more complicated. For its eradication the treatment course is often prolonged and frustrating. Based on the current literature an algorithm of treatment for both acute and chronic bone infections is recommended.

Validity of preoperative ultrasound-guided aspiration in the revision of hip prosthesis

Preoperative diagnosis of septic loosening hip prosthesis is often challenging. Culture test on joint samples obtained during revision surgery is the diagnostic gold standard while the role of preoperative hip aspiration is still controversial. The aims of this prospective randomized study were to compare the sensitivity, specificity and accuracy of preoperative ultrasound-guided and fluoroscopic-guided aspiration, and to identify associated laboratory parameters or scintigraphy that could help in predicting septic loosing hip prosthesis. Sixty patients affected by persistent pain after hip prosthesis randomly received fluoroscopic-guided or ultrasound-guided hip aspiration before revision surgery. The results of culture tests of joint fluid presurgically and at surgery were compared. In addition, associated blood inflammatory markers and scintigraphy were evaluated. Ultrasound-guided aspiration showed a better sensitivity (69% vs. 27%), specificity (94% vs. 75%) and accuracy (83% vs. 40%) than fluoroscopic-guided aspiration. The combination of ultrasound-guided aspiration and C-reactive protein represents the best model to predict septic loosening hip prosthesis preoperatively.

Infected tumor prostheses

Infection of tumor prostheses has been a major concern because of the extensive soft tissue dissection, long operating times, and patients' immunosuppression by cancer and adjuvant treatments. Infections most often present within 2 years postoperatively, with approximately 70% of postoperative deep infections presenting within 12 months after surgery. They are typically low organism burden infections, the pathogenesis of which is related to bacteria growing in biofilms. Staphylococci are the most common pathogens involved in prosthetic joint infections, accounting for approximately 50% of infections overall, followed by streptococci, enterococci, Enterobacteriaceae species, Pseudomonas aeruginosa, and anaerobe species. Multiple pathogens may be isolated in approximately 25% of cases, with the most common combination being coagulase-negative Staphylococcus and group-D Streptococcus. Early diagnosis and appropriate treatment are necessary. However, diagnosis may be challenging because clinical symptoms are highly variable and numerous preoperative and intraoperative diagnostic laboratory tests are nonspecific. In most cases, a 1- or 2-stage revision surgery is necessary for eradicating the megaprosthetic infection. Prevention of infection is important. The future will see technical advances for infections of tumor prostheses in areas such as microbiological diagnostics and biofilm-resistant prostheses.

Percutaneous vertebral body cement augmentation for back pain related to occult osteomyelitis/diskitis

Although complications related to vertebroplasty or kyphoplasty are few, we treated 2 patients with vertebroplasty or kyphoplasty for pain, presumed to be due to vertebral compression fractures, which were subsequently found to be due to occult osteomyelitis/diskitis. The onset of their infections appeared to have preceded their vertebral body augmentation procedures and was possibly due to prior interventional procedures for histories of back pain.An 86-year-old woman had had 3 prior kyphoplasty procedures for fractures at T10, T11, and L1. She reported continued severe pain, and subsequent magnetic resonance imaging was misinterpreted for another fracture at T12, resulting in her fourth kyphoplasty. She became septic and had some improvement with antibiotics, but she declined specialty care and died. A 74-year-old man with chronic back pain had recently undergone lumbar facet joint injections. Computed tomography and subsequent bone scan found uptake at both L2 and L3. Despite abnormal erythrocyte sedimentation rate and C-reactive protein level and normal radiographic vertebral height, he underwent a vertebroplasty. His pain increased, and subsequent workup found L2-3 diskitis. He recovered with antibiotics and specialty care. Similar to prior reports of spondylodiskitis, both patients had multiple medical comorbidities.This article emphasizes the need for clinical reevaluation and scrutiny in the interpretation of imaging studies, including for infection in patients with continued pain after spinal procedures. The differential diagnosis of infectious etiology is an important consideration prior to vertebral cement augmentation for presumed fragility fracture.

SPECT-CT with 67Ga-citrate in the management of spondylodiscitis

Spondylodiscitis affects a small proportion of all patients with locomotor system infections, however its early diagnosis is important due to its potential morbidity. Magnetic resonance imaging is the diagnostic method of choice. Nonetheless, it has certain limitations and is not suitable for all patients. The conventional scintigraphic studies for evaluating spondylodiscitis are those performed with (99m)Tc-HDP and (67)Ga-citrate. However, their poor image resolution is a disadvantage of these techniques. The use of hybrid Single Photon Emission Computed Tomography-Computed Tomography (SPECT-CT) improves detection of the disease by combining functional and anatomical images. We present 9 patients with suspicion of spondylodiscitis who underwent sequential bone scintigraphy with (99m)Tc-HDP and SPECT-CT with (67)Ga-citrate, with positive findings confirmed by clinical monitoring for at least 6 months.

The Additional Value of Tc 99m HMPAO White Blood Cell SPECT in the Evaluation of Bone and Soft Tissue Infections

OBJECTIVE

The aim of this prospective study was to evaluate the additional value of Tc 99m HMPAO white blood cell (WBC) SPECT for bone and soft tissue infections.

MATERIALS AND METHODS

Thirty-eight patients with suspected bone and joint infection were included in the study. Patients were assigned into 2 groups according to the presence of orthopedic implants. All patients had multiphase bone scan (BS) with Tc 99m methylene diphosphonate and WBC scintigraphy. The planar images of BS and WBC images were evaluated together. SPECT WBC images were evaluated separately.

RESULTS

Group 1 had 30 patients including 12 patients with diabetic foot, 17 patients with suspected relapse of chronic osteomyelitis and 1 with septic arthritis. In 19 of 30 patients, BS and planar WBC images were similar with SPECT images in terms of final diagnosis. In the remaining 11 patients, planar BS+planar WBC images and SPECT WBC images were discordant. Group 2 included 8 patients with suspected infection of orthopedic implants. There was no difference between planar BS+planar WBC images and SPECT WBC in 6 of 8 patients. SPECT WBC images changed the diagnosis of 13 (34.2%) patients in the whole group. SPECT WBC images did not have any contribution in the evaluation of the 6 patients who had reactive changes.

CONCLUSION

SPECT images made significant contribution in discriminating soft tissue infection from osteomyelitis and improved diagnosis in terms of localization and the extent of disease.

CONFLICT OF INTEREST

None declared.