PET imaging in MSK infections

Musculoskeletal infections are highly feared, form a major burden on healthcare, and may lead to severe morbidity and mortality. The diagnosis may be difficult with non-specific symptoms requiring multiple diagnostic investigations. FDG-PET/CT is one of them showing good diagnostic accuracy in most musculoskeletal infections. However, one has to be aware of the non-specific FDG uptake in patients with metallic implants and in the postsurgical phase. In this chapter, the advantages and disadvantages of the use of FDG-PET/CT in musculoskeletal infections in described for several indications: infections in the peripheral bone, spine infections/spondylodiscitis, prosthetic joint infections, diabetic foot infections, and sternal bone/wound infections. Recent published guidelines and diagnostic flowcharts by delegates of the European Association of Nuclear Medicine in collaboration with delegates from other (clinical) societies, will be discussed. At the end of this chapter, recent developments in tracer and camera systems will be presented.</p

Long Axial Field-of-View PET for Ultra-Low-Dose Imaging of Non-Hodgkin Lymphoma during Pregnancy

Generally, positron emission tomography imaging is not often performed in the case of pregnant patients. The careful weighing of the risks of radiation exposure to the fetus and benefits for cancer staging and the swift onset of treatment for the mother complicates decision making in clinical practice. In oncology, the most commonly used PET radiotracer is 2-deoxy-2-[fluorine-18] fluoro-D-glucose (18F-FDG), a glucose analog which has established roles in the daily routines for, among other applications, initial diagnosis, staging, (radiation) therapy planning, and response monitoring. The introduction of long axial Field-of-View (LAFOV) PET systems allows for PET imaging with a reduced level of injected 18F-FDG activity while maintaining the image quality. Here, we discuss the first reported case of a pregnant patient diagnosed with follicular lymphoma using LAFOV PET imaging for the staging and therapy selection. The acquired PET images show diagnostic quality images with clearly distinguishable areas of lymphadenopathy, even with only 34 MBq of injected 18F-FDG activity, leading to a considerable decrease in the level of radiation exposure to the fetus

Importance of Blood Glucose Management Before 18F-FDG PET/CT in 322 Patients with Bacteremia of Unknown Origin

We investigated the effects of blood glucose levels on the performance of 18F-FDG PET/CT for detecting an infection focus in patients with bacteremia. Methods: A total of 322 consecutive patients with bacteremia who underwent 18F-FDG PET/CT between 2010 and 2021 were included. Logistic regression analysis was performed to evaluate the association between finding a true-positive infection focus on 18FFDG PET/CT and blood glucose level, type of diabetes, and use of hypoglycemic medication. C-reactive protein, leukocyte count, duration of antibiotic treatment, and type of isolated bacteria were considered as well. Results: Blood glucose level (odds ratio, 0.76 per unit increase; P=,0.001) was significantly and independently associated with 18F-FDG PET/CT outcome. In patients with a blood glucose level between 3.0 and 7.9mmol/L (54-142mg/dL), the true-positive detection rate of 18F-FDG PET/CT varied between 61% and 65%, whereas in patients with a blood glucose level between 8.0 and 10.9mmol/L (144-196mg/dL), the true-positive detection rate decreased to 30%- 38%. In patients with a blood glucose level greater than 11.0mmol/L (200mg/dL), the true-positive detection rate was 17%. In addition to C-reactive protein (odds ratio, 1.004 per point increase; P = 0.009), no other variables were independently associated with 18F-FDG PET/CT outcome. Conclusion: In patients with moderate to severe hyperglycemia, 18F-FDG PET/CT was much less likely to identify the focus of infection than in normoglycemic patients. Although current guidelines recommend postponing 18F-FDG PET/CT only in cases of severe hyperglycemia with glucose levels greater than 11mmol/L (200mg/dL), a lower blood glucose threshold seems to be more appropriate in patients with bacteremia of unknown origin and other infectious diseases.</p

PET/CT in Inflammatory and Auto-immune Disorders:Focus on Several Key Molecular Concepts, FDG, and Radiolabeled Probe Perspectives

Chronic immune diseases mainly include autoimmune and inflammatory diseases. Managing chronic inflammatory and autoimmune diseases has become a significant public health concern, and therapeutic advancements over the past 50 years have been substantial. As therapeutic tools continue to multiply, the challenge now lies in providing each patient with personalized care tailored to the specifics of their condition, ushering in the era of personalized medicine. Precise and holistic imaging is essential in this context to comprehensively map the inflammatory processes in each patient, identify prognostic factors, and monitor treatment responses and complications. Imaging of patients with inflammatory and autoimmune diseases must provide a comprehensive view of the body, enabling the whole-body mapping of systemic involvement. It should identify key cellular players in the pathology, involving both innate immunity (dendritic cells, macrophages), adaptive immunity (lymphocytes), and microenvironmental cells (stromal cells, tissue cells). As a highly sensitive imaging tool with vectorized molecular probe capabilities, PET/CT can be of high relevance in the management of numerous inflammatory and autoimmune diseases. Relying on key molecular concepts of immunity, the clinical usefulness of FDG-PET/CT in several relevant inflammatory and immune-inflammatory conditions, validated or emerging, will be discussed in this review, together with radiolabeled probe perspectives.</p

Imaging fungal infections in children

Fungal infections in children rarely occur, but continue to have a high morbidity and mortality despite the development of newer antifungal agents. It is essential for these infections to be diagnosed at the earliest possible stage so appropriate treatment can be initiated promptly. The addition of high-resolution computer tomography (HR CT) has helped in early diagnosis making; however, it lacks both sensitivity and specificity. Metabolic changes precede anatomical changes and hybrid imaging with positron emission tomography (PET) integrated with imaging modalities with high anatomical resolution such as CT or magnetic resonance imaging (MRI) is likely to detect these infections at an earlier stage with higher diagnostic accuracy rates. Several authors presented papers highlighting the advantages of PET/CT in imaging fungal infections. These papers, however, usually involve a limited number of patients and mostly adults. Fungal infections behave different in children than in adults, since there are differences in epidemiology, imaging findings, and response to treatment with antifungal drugs. This paper reviews the literature and explores the use of hybrid imaging for diagnosis and therapy decision making in children with fungal infections

Insulinoma Manifesting Early Postpartum:Case Report and Review of the Literature

Objective: Insulinomas are insulin-producing neuroendocrine tumors. Insulinomas presenting during pregnancy and the early postpartum period are very rare. Methods: A 33-year-old woman with hypoglycemia early postpartum is described. Abdominal computed tomography and endoscopic ultrasound showed 2 lesions of the pancreas. An 11C-5-hydroxy-L-tryptophan (11CHTP) positron emission tomography-computed tomography (PET-CT) scan demonstrated additional uptake in lymph nodes and liver, suggesting malignant insulinoma. Six months after pylorus-preserving pancreatoduodenectomy and excision of liver and lymph node metastases, tumor progression was noted on repeated 11C-HTP PET-CT scans without recurrent hypoglycemia. She was enrolled in a clinical trial and was randomized for dual pan-class I phosphoinositide 3-kinase inhibitor and mammalian target of rapamycin inhibitor treatment, on which there was no tumor progression during 21 months follow-up. A systematic search of PubMed and Medline with the search strategy ‘insulinoma AND pregnancy’ OR ‘insulinoma AND postpartum’ was performed to identify English-, Dutch-, and German-language publications. All publications about (malignant) insulinoma during pregnancy and in the early postpartum period (≤3 months postpartum) were reviewed in addition to the described case report. Results: Insulinoma manifesting during pregnancy or early after delivery has been described in 31 cases, including only 3 cases of malignant insulinoma. Management of malignant insulinoma requires an individualized approach; optimal medical treatment is evolving. Conclusion: The usefulness of 11C-HTP PET-CT in the diagnosis of malignant insulinoma was demonstrated in the present case. Hypoglycemia may particularly become manifest in the postpartum period when insulin action increases consequent to decreased levels of placenta-derived counterregulatory hormones after delivery.</p

Practice of ¹⁸F-FDG-PET/CT in ICU Patients:A Systematic Review

18F-FDG-PET/CT imaging has become a key tool to evaluate infectious and inflammatory diseases. However, application of 18F-FDG-PET/CT in patients in the intensive care unit (ICU) is limited, which is remarkable since the development of critical illness is closely linked to infection and inflammation. This limited use is caused by perceived complexity and risk of planning and executing 18F-FDG-PET/CT in such patients. The aim of this systematic review was to investigate the feasibility of 18F-FDG-PET/CT in ICU patients with special emphasis on patient preparation, transport logistics and safety. Therefore, a systematic search was performed in PubMed, Embase, and Web of Science using the search terms: intensive care, critically ill, positron emission tomography and 18F-FDG or derivates. A total of 1183 articles were found of which 10 were included. Three studies evaluated the pathophysiology of acute respiratory distress syndrome, acute lung injury and acute chest syndrome. Three other studies applied 18F-FDG-PET/CT to increase understanding of pathophysiology after traumatic brain injury. The remaining four studies evaluated infection of unknown origin. These four studies showed a sensitivity and specificity between 85%-100% and 57%-88%, respectively. A remarkable low adverse event rate of 2% was found during the entire 18F-FDG-PET/CT procedure, including desaturation and hypotension. In all studies, a team consisting of an intensive care physician and nurse was present during transport to ensure continuation of necessary critical care. Full monitoring during transport was used in patients requiring mechanical ventilation or vasopressor support. None of the studies used specific patient preparation for ICU patients. However, one article described specific recommendations in their discussion. In conclusion, 18F-FDG-PET/CT has been shown to be feasible and safe in ICU patients, even when ventilated or requiring vasopressors. Specific recommendations regarding patient preparation, logistics and scanning are needed. Including 18F-FDG-PET/CT in routine workup of infection of unknown origin in ICU patients showed potential to identify source of infection and might improve outcome.</p

[18F]FDG-PET/CT in mechanically ventilated critically ill patients with COVID-19 ARDS and persistent inflammation.

Purpose: We report the findings of four critically ill patients who underwent an [18F]FDG-PET/CT because of persistent inflammation during the late phase of their COVID-19.Methods: Four mechanically ventilated patients with COVID-19 were retrospectively discussed in a research group to evaluate the added value of [18F]FDG-PET/CT.Results: Although pulmonary PET/CT findings differed, bilateral lung anomalies could explain the increased CRP and leukocytes in all patients. This underscores the limited ability of the routine laboratory to discriminate inflammation from secondary infections. Based on PET/CT findings, a secondary infection/inflammatory focus was suspected in two patients (pancreatitis and gastritis). Lymphadenopathy was present in patients with a detectable SARS-CoV-2 viral load. Muscle uptake around the hips or shoulders was observed in all patients, possibly due to the process of heterotopic ossification.Conclusion: This case series illustrates the diagnostic potential of [18F]FDG-PET/CT imaging in critically ill patients with persistent COVID-19 for the identification of other causes of inflammation and demonstrates that this technique can be performed safely in mechanically ventilated critically ill patients.</p

[¹⁸F]FDG-PET/CT in mechanically ventilated critically ill patients with COVID-19 ARDS and persistent inflammation

Purpose: We report the findings of four critically ill patients who underwent an [18F]FDG-PET/CT because of persistent inflammation during the late phase of their COVID-19. Methods: Four mechanically ventilated patients with COVID-19 were retrospectively discussed in a research group to evaluate the added value of [18F]FDG-PET/CT. Results: Although pulmonary PET/CT findings differed, bilateral lung anomalies could explain the increased CRP and leukocytes in all patients. This underscores the limited ability of the routine laboratory to discriminate inflammation from secondary infections. Based on PET/CT findings, a secondary infection/inflammatory focus was suspected in two patients (pancreatitis and gastritis). Lymphadenopathy was present in patients with a detectable SARS-CoV-2 viral load. Muscle uptake around the hips or shoulders was observed in all patients, possibly due to the process of heterotopic ossification. Conclusion: This case series illustrates the diagnostic potential of [18F]FDG-PET/CT imaging in critically ill patients with persistent COVID-19 for the identification of other causes of inflammation and demonstrates that this technique can be performed safely in mechanically ventilated critically ill patients.</p