Utility of FDG-PET/CT for the Detection and Characterization of Sternal Wound Infection Following Sternotomy

Role and applications of 18F-FDG PET/CT in the assessment of osteoarticular infection and inflammation - Part I

18F-FDG PET/CT has been positioned over time as a useful tool in the evaluation of osteoarticular infections, overcoming conventional explorations like MRI or bone scintigraphy in some indications. Its ability to provide functional and anatomical images simultaneously and its excellent resolution contributes to a more precise and personalised approach in the treatment of osteoarticular diseases such as spondylodiscitis. In addition, it has proven valuable in patients with suspected infection that is complex to diagnose or treat, improving detection in subclinical stages. However, some limitations have been identified, such as difficulty in the differential diagnosis of infection vs. inflammation (as in diabetic foot) or in the interpretation of patients with osteosynthesis materials. In this manuscript, we present a brief review providing general and practical information about the role of 18F-FDG PET/CT in infectious osteoarticular pathology, while part 2 discusses the role of 18F-FDG PET/CT in osteoarticular inflammation.

EANM/SNMMI guideline/procedure standard for [18F]FDG hybrid PET use in infection and inflammation in adults v2.0

INTRODUCTION

Hybrid [18F]FDG PET imaging is currently the method of choice for a wide variety of infectious and inflammatory disorders and was recently adopted in several clinical guidelines. A large amount of evidence-based articles, guidelines and appropriate use criteria have been published since the first version of this guideline in 2013.

PURPOSE

To provide updated evidence-based information to assist physicians in recommending, performing and interpreting hybrid [18F]FDG PET examinations for infectious and inflammatory disorders in the adult population.

METHODS

A systematic literature search of evidence-based articles using whole-body [18F]FDG hybrid imaging on the indications covered within this guideline was performed. All systematic reviews and meta-analyses published within the last 10 years until January 2023 were identified in PubMed/Medline or Cochrane. For each indication covered in this manuscript, diagnostic performance was provided based on meta-analyses or systematic reviews. If not available, results from prospective or retrospective studies were considered based on predefined selection criteria. RESULTS AND CONCLUSIONS: Hybrid [18F]FDG PET is extremely useful in the work-up and management of adults with infectious and inflammatory diseases, as supported by extensive and rapidly growing evidence-based literature and adoption in clinical guidelines. Practical recommendations are provided describing evidence-based indications as well as interpretation criteria and pitfalls. Monitoring treatment response is the most challenging but insufficiently studied potential application in infection and inflammation imaging.

Radiologic Manifestations of Mycobacterium chimaera Infection After Open Heart Surgery

PURPOSE

The objective of this study is to identify and detail the radiologic manifestations of surgical site and disseminated Mycobacterium chimaera ( MC) infection. The aim is to facilitate early identification and diagnosis of MC, considering its indolent nature and the challenges involved in clinically and pathologically establishing the diagnosis.

PATIENTS AND METHODS

This was a retrospective cohort study reviewing computed tomography (CT), positron emission tomography (PET)/CT, and magnetic resonance imaging examinations in patients over the age of 18 years with a history of open heart surgery and a clinical or pathologic diagnosis of MC. Two radiology residents, a fellowship-trained nuclear medicine radiologist, and a fellowship-trained cardiothoracic radiologist performed consensus reads to determine the imaging findings seen in MC infection.

RESULTS

Twenty-five patients were included. Localized, surgical site infection was more common than disseminated disease. Typical CT findings included peristernal soft tissue thickening, sinus tracts often extending to the cutaneous surface, slowly enlarging fluid collections, and sternal osteolysis. PET/CT findings demonstrated hypermetabolic activity in nearly all patients localized to sites of infection. Imaging findings for disseminated infection included hepatosplenomegaly, lymphadenopathy, involvement of the central nervous system, discitis/osteomyelitis, and distant abscesses.

CONCLUSIONS

Imaging plays a vital role in suggesting possible surgical sites and disseminated MC infection acquired from open heart surgery. Radiologists must keep a high index of suspicion given the indolent nature and subtle imaging change over time. PET/CT is most useful in diagnosis and helps in differentiating between a sterile postoperative fluid collection or scarring and active MC infection and helps provide a target for debridement.

Computed Tomography Scanning for Sternal Wound Infections: A Systematic Review

Background

Sternal wound infection (SWI) has always been a significant risk in patients who undergo sternotomies as part of their cardiac surgical procedures. Computed tomography (CT) imaging is often used to diagnose and assess sternal wound infections. Its purpose includes identifying and locating infection and any sternal dehiscence.

Methods

A systematic literature review across PubMed, Embase, and Ovid was performed according to PRISMA guidelines to identify relevant articles that discussed the utility of CT scanning for SWI, common features identified, patient outcomes and sensitivity/specificity (Figure 1).

Results

25 papers were included. 100% (n=25) of the papers were published in peer-reviewed journals. CT scans in SWIs can be seen as a beneficial aid in diagnosing as well as determining the components of infection. Commonalities were identified such as fluid collection in the mediastinum, free gas, pleural effusions, and sternal dehiscence which point towards the presence of sternal wound infection.

Conclusion

CT scanning is a novel and emerging methodology for imaging in SWI and post-sternotomy complications, hence increased research is required to expand the literature on this area as well as the creation of guidelines and cut-offs or signs for radiology professionals to identify and determine the extent of infection.

18F-FDG/PET-CT imaging findings after sternotomy

BACKGROUND

The clinical diagnosis of deep sternal wound infection (DSWI) is supported by imaging findings including 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT). To avoid misinterpretation due to normal post-surgery inflammation we assessed normal imaging findings in non-infected patients after sternotomy.

METHODS

This is a prospective cohort study including non-infectious patients with sternotomy. All patients underwent 18F-FDG-PET/CT at either 5 weeks (group 1), 12 weeks (group 2) or 52 weeks (group 3) post-surgery. 18F-FDG uptake was scored visually in five categories and assessed quantitatively.

RESULTS

A total of 44 patients were included. Sternal mean SUVmax was 7.34 (± 1.86), 5.22 (± 2.55) and 3.20 (± 1.80) in group 1, 2 and 3, respectively (p < 0.01). Sternal mean SUVmean was 3.84 (± 1.00), 2.69 (± 1.32) and 1.71 (± 0.98) in group 1, 2 and 3 (p < 0.01). All patients in group 1 had elevated uptake whereas group 2 and 3 showed 2/15 (13%) and 11/20 (55%) patients respectively with no elevated uptake. Group 3 still showed an elevated uptake pattern in in 9/20 (45%) and in 3/9 (33%) with a high-grade diffuse uptake pattern.

CONCLUSION

This study shows significant lower sternal 18F-FDG at 55 weeks compared to 5 weeks post-sternotomy however elevated uptake patterns may persist.

[18F]FDG-PET CT for the evaluation of native valve endocarditis

BACKGROUND

We examined the use of [18F]FDG-PET/CT for the diagnosis of native valve endocarditis (NVE).

METHODS

PET/CT images in patients with suspected NVE were retrospectively reviewed independently by two experienced physicians blinded to all clinical information. The gold standard consisted of surgical findings, when available, or the modified Duke criteria.

RESULTS

Fifty four subjects were included, 31 (57%) with a diagnosis of NVE. [18F]FDG-PET/CT correctly identified 21/31 (67.7%) subjects, yielding a sensitivity and specificity of 68% (95% CI 49-83%) and 100% (95% CI 85-100%), respectively. The sensitivity and specificity of the modified Duke criteria were 48% and 74%, respectively. Positive and negative predictive values of PET were 100% (95% CI 84-100%) and 70% (95% CI 51-84%), respectively. Modifying the Duke criteria to include [18F]FDG-PET positivity as a major criterion increased sensitivity to 77% without affecting specificity and led to the correct reclassification of 8/18 (44.4%) subjects from Possible IE to Definite IE.

CONCLUSION

The addition of a positive [18F]FDG-PET/CT as a major criterion in the modified Duke Criteria improved performance of the criteria for the diagnosis of NVE, particularly in those subjects with Possible IE.

ACR Appropriateness Criteria® Nontraumatic Chest Wall Pain

Chest pain is a common reason that patients may present for evaluation in both ambulatory and emergency department settings, and is often of musculoskeletal origin in the former. Chest wall syndrome collectively describes the various entities that can contribute to chest wall pain of musculoskeletal origin and may affect any chest wall structure. Various imaging modalities may be employed for the diagnosis of nontraumatic chest wall conditions, each with variable utility depending on the clinical scenario. We review the evidence for or against use of various imaging modalities for the diagnosis of nontraumatic chest wall pain. 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.

Detection of Native and Prosthetic Valve Endocarditis: Incremental Attributes of Functional FDG PET/CT over Morphologic Imaging

PURPOSE OF REVIEW

The clinical and incremental value of functional imaging with ¹⁸F-fluorodeoxyglucose-positron emission tomography/computed tomography (FDG PET/CT) for the diagnosis and management of patients with suspected native and prosthetic valve infective endocarditis (IE).

RECENT FINDINGS

The diagnosis of IE is challenging because of the highly variable clinical presentations, especially in the case of prosthetic valve endocarditis (PVE). FDG PET/CT has been shown to play an important role for the diagnosis of PVE as a major Duke criterion. Whether FDG PET/CT could play a similar role in patients with suspected native valve endocarditis (NVE) is less well established. It is increasingly recognized that IE is a multisystem disorder, and identification of extra-cardiac manifestations on whole-body FDG PET/CT impacts management and prognosis of patients with IE. Finally, FDG PET/CT provides incremental prognostic value over other clinical and para-clinical parameters, enabling prediction of in-hospital mortality, IE recurrence, hospitalization, and new onset heart failure and embolic events. FDG PET/CT plays a key role in the investigation of patients with suspected IE, enabling detection of valvular infection and extra-cardiac manifestations of the infection which has important prognostic implications.