FDG-PET imaging to detect and characterize underlying causes of fever of unknown origin: an unavoidable path for the foreseeable future

Diagnostic value of FDG-PET/CT in fever of unknown origin

Background

Fever of unknown origin (FUO) is a challenging clinical problem in medicine that needs collaboration of various diagnostic techniques to establish the accurate diagnosis. We evaluated the diagnostic performance of 18F-FDG PET/CT in patients who presented themselves with FUO. Our study included 40 patients with FUO who underwent PET/CT examination and their results were compared to the results of laboratory, histopathological, microbiological investigations and/or response to therapy.

Results

The final diagnosis included malignancy in 20 patients (50%), infectious causes in 7 patients (17.5%) and non-infectious inflammatory causes in 6 patients (15%). Fever resolved without diagnosis in 4 patients (10%), while no definite diagnosis was reached in 3 patients (7%). PET/CT successfully contributed to diagnosis of 35 out of 40 patients with diagnostic accuracy of 87.5%. The sensitivity, specificity, positive predictive value and negative predictive value of PET/CT in our study were 93.5%, 66.7%, 90.6% and 75%, respectively.

Conclusion

PET/CT is a useful tool to investigate and diagnose the cause of FUO. It provides information that can guide the treatment strategy of the patients.

Diagnostic value of F-18 FDG PET/CT in fever or inflammation of unknown origin in a large single-center retrospective study

Cause determination is challenging in fever or inflammation of unknown origin (FUO/IUO) despite today’s diagnostic modalities. We evaluated the value of F-18 FDG PET/CT in an unselected patient collective. This retrospective nonrandomized single-center study enrolled 300 male and female patients with FUO/IUO. PET/CT findings were compared with final clinical outcomes to determine the sensitivity, specificity, clinical significance, etiological distribution of final diagnoses, impact on treatment, role of white-blood cell count (WBC), and C-reactive protein (CRP). In 54.0% (162/300) PET/CT was the decisive exanimation for establishing the final diagnosis, in 13.3% (40/300) the findings were equivocal and indecisive, in 3.3% (10/300) PET/CT findings were false positive, while in 29.3% (88/300) a normal F-18 FDG pattern was present. Statistical analysis showed a sensitivity of 80.2% and a specificity of 89.8% for the contribution of PET/CT to the final diagnosis. CRP levels and WBC were not associated with PET/CT outcome. PET/CT let to new treatment in 24.0% (72/300), treatment change in 18.0% (54/300), no treatment change in 49.6% (149/300), and in 8.3% (25/300) no data was available. Our study demonstrates the utility of F-18 FDG PET/CT for source finding in FUO/IUO if other diagnostic tools fail.

[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.

Unparalleled and revolutionary impact of PET imaging on research and day to day practice of medicine

Positron emission tomography (PET) imaging is the most quantitative modality for assessing disease activity at the molecular and cellular levels, and therefore, it allows monitoring its course and determining the efficacy of various therapeutic interventions. In this scientific communication, we describe the unparalleled and revolutionary impact of PET imaging on research and day to day practice of medicine. We emphasize the critical importance of the development and synthesis of novel radiotracers (starting from the enormous impact of F-Fluorodeouxyglucose (FDG) introduced by investigators at the University of Pennsylvania (PENN)) and PET instrumentation. These innovations have led to the total-body PET systems enabling dynamic and parametric molecular imaging of all organs in the body simultaneously. We also present our perspectives for future development of molecular imaging by multiphoton PET systems that will enable users to extract substantial information (owing to the evolving role of positronium imaging) about the related molecular and biological bases of various disorders, which are unachievable by the current PET imaging techniques.

Total-Body PET Imaging of Musculoskeletal Disorders

Imaging of musculoskeletal disorders, including arthritis, infection, osteoporosis, sarcopenia, and malignancies, is often limited when using conventional modalities such as radiography, computed tomography (CT), and MR imaging. As a result of recent advances in Positron Emission Tomography (PET) instrumentation, total-body PET/CT offers a longer axial field-of-view, higher geometric sensitivity, and higher spatial resolution compared with standard PET systems. This article discusses the potential applications of total-body PET/CT imaging in the assessment of musculoskeletal disorders.

Application of Computed Tomography Imaging in Diagnosis of Endocrine Nerve of Gastric Cancer and Nursing Intervention Effect

In this article, some parameters and characteristics of computed tomography (CT) images in patients with gastric cancer are analyzed and the application of CT images in the diagnosis of gastric cancer endocrine nerves and the impact of nursing intervention on the quality and mental state of CT images of patients with gastric cancer are discussed. First, all patients were scanned with CT, and the CT values of the normal stomach wall and all lesions at different single-energy levels were recorded separately. Second, the improved back propagation network model was applied to realize the diagnosis of gastric cancer through the analysis of various features of CT images. The effect of nursing intervention on the image quality and mental state of CT imaging of patients with gastric cancer was studied. The results show that the energy spectrum curve of CT images and the improved back propagation network model are helpful for the initial diagnosis and identification of gastric cancer. Nursing intervention has a good influence on the clinical examination, image diagnosis, and psychological state of patients with gastric cancer, and it is easy for patients to undergo image diagnosis and examination according to correct operating procedures.

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.

Diagnostic Value of 18F-FDG-PET/CT in Patients with FUO

Conventional diagnostic imaging is often ineffective in revealing the underlying cause in a considerable proportion of patients with fever of unknown origin (FUO). The aim of this study was to assess the diagnostic value of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG-PET/CT) in patients with FUO. We retrospectively reviewed ¹⁸F-FDG-PET/CT scans performed on 50 consecutive adult patients referred to our department for further investigation of classic FUO. Final diagnosis was based on histopathological and microbiological findings, clinical criteria, or clinical follow-up. Final diagnosis was established in 39/50 (78%) of the patients. The cause of FUO was infection in 20/50 (40%), noninfectious inflammatory diseases in 11/50 (22%), and malignancy in 8/50 (16%) patients. Fever remained unexplained in 11/50 (22%) patients. ¹⁸F-FDG-PET/CT scan substantially contributed to the diagnosis in 70% of the patients, either by identifying the underlying cause of FUO or by directing to the most appropriate site for biopsy. Sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) of ¹⁸F-FDG-PET/CT for active disease detection in patients with FUO were 94.7%, 50.0%, 84.0%, 85.7%, and 75.0%, respectively. In conclusion, whole-body ¹⁸F-FDG-PET/CT is a highly sensitive method for detection of the underlining cause of FUO or for correctly targeting suspicious lesions for further evaluation.

Localization of acute pyelonephritis in pyrexia of unknown origin using FDG PET/CT

Objectives

Acute pyelonephritis presents with high-grade fever, dysuria, flank pain, leukocytosis, and microscopic hematuria. Urine culture aids in the diagnosis of this infection. It can be complicated or uncomplicated. Complicated pyelonephritis includes uncontrolled diabetes, transplant, pregnancy, acute or chronic renal failure, structural abnormality of the urinary tract, immunocompromised state, and hospital-acquired infections. Gram-negative bacteria commonly involved are Escherichia, Klebsiella, Proteus, and Enterobacter. The FDG PET/CT helps detect occult causes of fever, such as skeletal tuberculosis, thyroiditis, and lymphoma, when other investigations are inconclusive. We present three cases of pyrexia of unknown origin (PUO) in whom FDG PET/CT helped localize the focus of infection in the kidneys.

Methods

The ¹⁸F-FDG PET/CT was performed on all three cases and images were acquired using the Biograph Horizon PET/CT system.

Results

A cortical-based focus of FDG uptake was localized in the kidneys. The focus of abnormality was persistent following diuretic administration at 1-hour delayed regional image. Two cases had supportive evidence of pyelonephritis on DMSA scan. One case also had frank pus drained after DJ stenting of the affected side. All of them responded to treatment.

Conclusion

Physiologic excretion of FDG in the urinary tract may interfere with the detection of the focus of infection in the kidneys on FDG PET/CT. However, occult infection in the kidneys may be detected with adequate precautions, such as the use of diuretics and delayed imaging, as illustrated in this case report. Routine investigations were noncontributory in all three cases presenting with PUO. However, FDG PET provided a diagnostic clue for pyelonephritis.