FDG-PET imaging in Pneumocystis carinii pneumonia

Fluorodeoxyglucose Positron Emission Tomography Imaging in Pneumocystis jiroveci Pneumonia

Fever or pyrexia of unknown origin (PUO) is commonly defined as body temperature higher than 38.3°C on several occasions for a period of at least 3 weeks with uncertain diagnosis after initial routine obligatory investigations. In most cases of PUO, there is an uncommon presentation of a common disease which includes infection, noninfectious inflammatory diseases, malignancy, and miscellaneous causes. We present an interesting case of a 48-year-old man with PUO, who is a known case of multiple myeloma on immunosuppressive therapy, where 18F-fluorodeoxyglucose positron emission tomography-computed tomography was able to detect occult cause of infective etiology.

Pneumocystis jirovecii Pneumonia in Children with Hematological Malignancies: Diagnosis and Approaches to Management

Pneumocystis jirovecii pneumonia (PJP) is an opportunistic infection that mostly affects children with suppressed cellular immunity. PJP was the most common cause of infectious death in children with acute lymphoblastic leukemia prior to the inclusion of cotrimoxazole prophylaxis as part of the standard medical care in the late 1980s. Children with acute leukemia, lymphomas, and those undergoing hematopoietic stem cell transplantation, especially allogeneic transplantation, are also at high risk of PJP. Persistent lymphopenia, graft versus host disease, poor immune reconstitution, and lengthy use of corticosteroids are significant risk factors for PJP. Active infection may be due to reactivation of latent infection or recent acquisition from environmental exposure. Intense hypoxemia and impaired diffusing capacity of the lungs are hallmarks of PJP, while computerized tomography of the lungs is the diagnostic technique of choice. Immunofluorescence testing with monoclonal antibodies followed by fluorescent microscopy and polymerase chain reaction testing of respiratory specimens have emerged as the best diagnostic methods. Measurement of (1-3)-β-D-glucan in the serum has a high negative predictive value in ruling out PJP. Oral cotrimoxazole is effective for prophylaxis, but in intolerant patients, intravenous and aerosolized pentamidine, dapsone, and atovaquone are effective alternatives. Ιntravenous cotrimoxazole is the treatment of choice, but PJP has a high mortality even with appropriate therapy.

Current Landscape of Imaging and the Potential Role for Artificial Intelligence in the Management of COVID-19

The clinical management of COVID-19 is challenging. Medical imaging plays a critical role in the early detection, clinical monitoring and outcomes assessment of this disease. Chest x-ray radiography and computed tomography) are the standard imaging modalities used for the structural assessment of the disease status, while functional imaging (namely, positron emission tomography) has had limited application. Artificial intelligence can enhance the predictive power and utilization of these imaging approaches and new approaches focusing on detection, stratification and prognostication are showing encouraging results. We review the current landscape of these imaging modalities and artificial intelligence approaches as applied in COVID-19 management.

PET/CT in nononcological lung diseases: current applications and future perspectives

Positron emission tomography (PET) combined with computed tomography (CT) is an established diagnostic modality that has become an essential imaging tool in oncological practice. However, thanks to its noninvasive nature and its capability to provide physiological information, the main applications of this technique have significantly expanded.(18)F-labelled fluorodeoxyglucose (FDG) is the most commonly used radiopharmaceutical for PET scanning and demonstrates metabolic activity in various tissues. Since activated inflammatory cells, like malignant cells, predominantly metabolise glucose as a source of energy and increase expression of glucose transporters when activated, FDG-PET/CT can be successfully used to detect and monitor a variety of lung diseases, such as infections and several inflammatory conditions.The added value of FDG-PET/CT as a molecular imaging technique relies on its capability to identify disease in very early stages, long before the appearance of structural changes detectable by conventional imaging. Furthermore, by detecting the active phase of infectious or inflammatory processes, disease progression and treatment efficacy can be monitored.This review will focus on the clinical use of FDG-PET/CT in nonmalignant pulmonary diseases.

Quantification of aging effects upon global knee inflammation by 18F-FDG-PET

OBJECTIVE

The goal of this study was to quantify aging effects upon the global knee joint and surrounding capsule and soft tissue inflammation using fluorine-18 fluorodeoxyglucose (18F-FDG) PET imaging.

METHODS

This reanalysis of a prospective study included 64 patients who had undergone 18F-FDG-PET for evaluation of hip joint prostheses, and whose scans included the knee joints in the field of view. Mean patient age was 53 years (range: 33-84 years). A fixed-sized three-dimensional region of interest was placed around each knee joint, paying close attention to exclude the popliteal vessels. 18F-FDG-avid regions in each knee joint were then segmented using an adaptive contrast-oriented thresholding method, and metabolically active volume (MAV), mean standardized uptake value (SUV mean), partial volume-corrected SUV mean (cSUV mean), and partial volume-corrected mean metabolic volumetric product (cMVP mean = cSUV mean × MAV) of the segmented regions were calculated. Finally, global knee inflammation (GKI) for each knee joint was calculated as the sum of cMVP mean in all segmented regions. Association of GKI with age was assessed with Pearson's correlation and linear regression methods, and GKI was compared between patients at different ages - between patients younger than 55 years and those older than 55 years - using the unpaired t-test.

RESULTS

The correlation coefficient of GKI with advancing age was 0.57 (P = 0.02). In the linear regression model, considering GKI as the dependent variable and age and sex as independent covariates, the β coefficient of age was 2.1 (95% confidence interval: 1.1-3.2). For patients aged younger than 55 years versus those aged older than 55 years, the mean GKI was 157 and 190 cm3, respectively (P = 0.01).

CONCLUSION

Through the use of novel quantitative techniques, we were able to calculate GKI and demonstrate a significant increase in the entity of joint inflammation with advancing age. As degenerative disease is age-related and inflammation is implicated in its pathogenesis, our findings further support this association. These preliminary data suggest that this approach can potentially provide a means to objectively quantify the degree of inflammation in various joint disorders, and possibly in other knee degenerative/inflammatory diseases.

Pneumocystis jirovecii pneumonia: still a concern in patients with haematological malignancies and stem cell transplant recipients

The risk of patients with ALL and recipients of an allogeneic HSCT developing Pneumocystis jirovecii pneumonia is sufficiently high to warrant guidelines for the laboratory diagnosis, prevention and treatment of the disease. In this issue, the European Conference on Infections in Leukemia (ECIL) presents its recommendations in three companion papers.

Assessment of Therapy Response by FDG PET in Infection and Inflammation

Positron emission tomography (PET) is a well-known imaging modality in assessing the treatment response to chemotherapy or radiotherapy in various malignancies. A systematic review of the literature reveals a few publications reporting evaluation of the treatment response in benign conditions using PET/computed tomography. PET holds a promising future role in the follow-up of inflammatory or infectious diseases. In this article, [(18)F]Fluorodeoxyglucose PET as a tool in the evaluation, treatment, and follow-up of infectious and inflammatory diseases is discussed.

Late-onset Pneumocystis jirovecii pneumonia post-fludarabine, cyclophosphamide and rituximab: implications for prophylaxis

Objective

Fludarabine, cyclophosphamide and rituximab (FCR) therapy for lymphoid malignancies has historically been associated with a low reported incidence of Pneumocystis jirovecii pneumonia (PJP). However, prophylaxis was routinely used in early studies, and molecular diagnostic tools were not employed. The objective of this study was to review the incidence of PJP during and post‐FCR in the era of highly sensitive molecular diagnostics and ¹⁸F‐fluorodeoxyglucose (FDG) positron emission tomography (PET)–computerised tomography (CT).

Methods

All patients treated with standard FCR at the Peter MacCallum Cancer Centre (March 2009 to June 2012) were identified from a medications management database. Laboratory‐confirmed PJP cases during this time were identified from an electronic database.

Results

Overall, 66 patients were treated with a median of 5.5 FCR cycles. Eight PJP cases were identified, 6 of whom had received chemotherapy prior to FCR. In 5 cases, ¹⁸F‐FDG PET demonstrated bilateral ground‐glass infiltrates. Median CD4⁺ lymphocyte counts at time of PJP diagnosis and 9–12 months following FCR were 123 and 400 cells/μL, respectively. In patients receiving no prophylaxis, 9.1% developed PJP during FCR. The rate following FCR was 18.4%, with median onset at 6 months (2.4–24 months).

Conclusion

Given the high rate of late‐onset PJP, consideration should be given for extended PJP prophylaxis for up to 12 months post‐FCR, particularly in pretreated patients. Further evaluation of the role of CD4⁺ monitoring is warranted to quantify risk of disease development and to guide duration of prophylaxis.

Clinical utility of FDG-PET and PET/CT in non-malignant thoracic disorders

There have been several endeavors made to investigate the potential role of 2-deoxy-2-[(18)F]fluoro-D-glucose positron emission tomography (FDG-PET) (and tracers) and PET-computed tomography imaging in various benign disorders, particularly those related to thoracic structures. These various conditions can be broadly categorized into three groups: (a) infectious diseases (mycobacterial, fungal, bacterial infection), (b) active granulomatous disease such as sarcoidosis, and (c) other non-infectious/inflammatory conditions or proliferative disorders (e.g., radiation pneumonitis, post-lung transplant lymphoproliferative disorders, occupational pleuropulmonary complications, and post-surgical conditions), all of which can demonstrate varying degrees of FDG uptake on PET scans based upon the degree of inflammatory activity. This article reviews the current state of this very important application of FDG-PET imaging.

Pneumocystis jirovecii pneumonia in non-HIV-infected patients: new risks and diagnostic tools

PURPOSE OF REVIEW

Non-HIV-infected populations are increasingly identified as being at risk for developing Pneumocystis jirovecii pneumonia (PJP). These patients typically present with severe disease and poorly tolerate invasive diagnostic procedures. This review examines recently reported risks for PJP in non-HIV populations and summarizes new diagnostic techniques.

RECENT FINDINGS

PJP is associated with immunomodulatory drug therapies, including monoclonal antibody therapies such as tumour necrosis factor α antagonists, and calcineurin inhibitors. Underlying disease states include solid-organ transplantation, connective tissue and rheumatologic disorders, inflammatory bowel disease, haematological malignancies, and solid tumours. Modern diagnostic techniques [conventional PCR, quantitative PCR, (1→3)-β-D-glucan assays, and PET] are reviewed with respect to predictive value and clinical utility. In particular, current literature regarding validation and specificity of molecular diagnostic techniques is summarized, including application to minimally invasive specimens.

SUMMARY

HIV-negative populations at risk for PJP can be identified. Conventional PCR increases diagnostic sensitivity but may detect asymptomatic colonization. Quantitative PCR demonstrates potential for distinguishing colonization from infection, but clinical validation is required. Serum (1→3)-β-D-glucan may be elevated in PJP, although standardized cut-off values for clinical infection have not been determined. Further validation of serum markers and molecular diagnostic methods is necessary for early and accurate diagnosis in non-HIV populations.

Combined PET and X-ray computed tomography imaging in pulmonary infections and inflammation

PURPOSE OF REVIEW

This review addresses issues relating to the use of the relatively new combined PET and X-ray computed tomography (PET/CT) modality for imaging pulmonary infections and inflammation, as well as assessing its potential for this purpose.

RECENT FINDINGS

Accurate definition and monitoring of the extent of lung infection is difficult using conventional chest radiograph, CT scan, MRI, and radioisotope scintigraphy. In the last decade, PET/CT using radiolabeled fluorodeoxyglucose has been added to the imaging armamentarium, mostly for imaging lung cancer. To date, very few data are available on the application of this technique for imaging pulmonary infections and inflammation; however, this situation is changing, and there is now more interest in using PET/CT for this purpose. In addition, there are new tracers on the horizon which remain to be exploited.

SUMMARY

This review addresses some of these issues and outlines the potential to use PET/CT for noncancer pulmonary indications.

Role of modern imaging techniques for diagnosis of infection in the era of 18F-fluorodeoxyglucose positron emission tomography

During the past several years, it has become quite evident that positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) imaging can play a major role in the management of patients with suspected infection. Particularly, several groups have demonstrated that this powerful imaging methodology is very effective in the evaluation of osteomyelitis, infected prostheses, fever of unknown origin, and AIDS. In view of its extraordinary sensitivity in detecting disease activity and the ability to quantitate the degree of FDG uptake, PET might prove to be an appropriate modality for monitoring disease activity and evaluating response to therapy. FDG-PET has many advantages over existing imaging techniques for the diagnosis of infectious diseases. These include feasibility of securing diagnostic results within 1.5 to 2 h, excellent spatial resolution, and accurate anatomical localization of sites of abnormality. The availability of PET/computed tomography as a practical tool has further enhanced the role of metabolic imaging in many settings. In the future, this modality is very likely to be employed on a routine basis for detecting, characterizing, and monitoring patients with suspected and proven infection.