Clinical usefulness of 18F-FDG PET/CT for initial staging and assessment of treatment efficacy in patients with lymph node tuberculosis

Utility of preoperative 18F-flurodeoxyglucose PET/CT scanning in preoperative evaluation and surgical planning for pulmonary tuberculosis

OBJECTIVE

The objective of this study was to investigate the utility of preoperative 18F-FDG PET/CT scanning in preoperative evaluation and surgical planning for pulmonary tuberculosis.

METHODS

The study involved a retrospective analysis of clinical data and preoperative chest 18F-FDG PET/CT data of 24 patients with pulmonary tuberculosis who underwent pneumonectomy at the Shanghai Public Health Clinical Center between December 2017 and January 2022.

RESULTS

All 24 patients successfully underwent chest 18F-FDG PET/CT imaging, and complete data pertaining to the maximum standardized uptake value, mean standardized uptake value, minimum standardized uptake value, total lesion glycolysis, and metabolic tumor volume were obtained. Surgical excision plans were finalized using the chest 18F-FDG PET/CT findings along with the conventional chest CT scans. Pneumonectomy was successfully completed in all 24 patients, and these included 13 cases of pulmonary lobectomy, two cases of total pneumonectomy, one case of combined pulmonary lobectomy, one case of segmentectomy, and seven cases of pulmonary wedge resection. The actual surgical procedures had a conformity rate of 100% to the preoperative surgical plans that were made. The intraoperative bronchial stump embedding rate was 69% (11/18 cases), the incidence rate of postoperative air leakage was 3.8% (1/24 cases), and there were no reported cases of postoperative bronchopleural fistula or death.

CONCLUSION

Preoperative 18F-FDG PET/CT scans had significant utility in surgical planning, the selection of surgical methods, and the formulation of postoperative antituberculosis treatment courses for patients with pulmonary tuberculosis. The use of 18F-FDG PET/CT shows considerable promise in being promoted clinically for the surgical management of patients with pulmonary tuberculosis.

Comparison of 18F-FDG-PET/CT scans in patients diagnosed with sarcoidosis and tuberculosis

Positron emission tomography/computed tomography (PET/CT) is widely used to differentiate benign and malignant lesions. However, increased fluorodeoxyglucose (FDG) uptake may occur under certain benign conditions, leading to potential false positives in malignancy assessments. Tuberculosis and sarcoidosis are 2 conditions that can exhibit FDG uptake, presenting with both lymph node and extrathoracic involvement, alongside pulmonary manifestations. This study aimed to explore the utility of PET/CT in distinguishing between thoracic and extrathoracic involvement in patients with sarcoidosis and tuberculosis. A retrospective analysis was conducted on patients diagnosed with sarcoidosis or tuberculosis, either pathologically or microbiologically, who underwent 18F-FDG-PET/CT as part of their diagnostic process. This study evaluated demographic data, PET/CT findings, involvement sites, and maximum standardized uptake values (SUVmax) in patients with tuberculosis and sarcoidosis. PET/CT images of 62 patients (44 with tuberculosis and 18 with sarcoidosis) were analyzed. The median patient age was 55 years. Lymph node involvement in the cervical, abdominal, retro-pancreatic, inguinal, and extrathoracic regions was significantly more prevalent in patients with sarcoidosis than in those with tuberculosis (50% vs 20.5%, P = .0031; 27.8% vs 4.5%, P = .018; 22.2% vs 0%, P = .005; 27.8% vs 6.8%, P = .039; and 66.7% vs 27.3%, P = .009, respectively). No statistically significant difference was found in SUV values between patients with tuberculosis and those with sarcoidosis with regard to mediastinal lymph node, extrathoracic lymph node, lung, and bone PET/CT involvement. In conclusion, 18F-FDG-PET/CT imaging does not appear to be a reliable method for differentiating sarcoidosis and tuberculosis from malignant lesions, as it is not feasible to distinguish between sarcoidosis and tuberculosis solely based on 18F-FDG-PET/CT SUVmax values. Nevertheless, the increased prevalence of extrathoracic lymph node involvement in sarcoidosis compared to tuberculosis may offer valuable insights for clinicians in differential diagnosis.

PET-CT outcomes from a randomised controlled trial of rosuvastatin as an adjunct to standard tuberculosis treatment

Adjunctive rosuvastatin for rifampicin-susceptible pulmonary tuberculosis (rs-PTB) shows no effect on microbiological or radiological outcomes in a phase IIb randomised, controlled trial (NCT04504851). We explore the impact of adjunctive rosuvastatin on 18F-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) imaging in a sub-study of 24 participants. Changes in standardised uptake value (SUVmax, SUVmean), Total Metabolic Volume, (TMV), Total Lesion Glycolysis (TLG), cavity diameter and volume, between week 0 and week 8 post-randomisation, are evaluated. Here we show no evidence of difference in the reduction in TLG [median 65.8% for the rosuvastatin group (Q1, Q3 38.6, 94.5) vs 64.3% for standard tuberculosis treatment group (Q1, Q3 -20.0, 81.7), P = 0.32], reduction in cavity volume on CT [median 3.2 cm3 (IQR 11.1, 0.5) for rosuvastatin, 2.2 cm3 (IQR 4.6, 0.7) for control (p = 0.72)], or any other PET-CT parameter measured. We show that the first 8-weeks of standard tuberculosis treatment results in a reduction in the volumetric indices (TLG and TMV), but had little change in SUVmax or SUVmean. Change in TLG and TMV holds promise as biomarkers of tuberculosis treatment response: future PET-CT studies should evaluate their role in predicting relapse-free cure, and the overall role of 18F-FDG-PET-CT as a tool for early-phase tuberculosis clinical trials.

Post-tuberculosis treatment paradoxical reactions

Paradoxical reactions (PR) to tuberculosis (TB) treatment are common during treatment, but have also been described after treatment. A presentation with recurrent signs or symptoms of TB after cure or completion of prior treatment needs to be differentiated between microbiological relapse and a paradoxical reaction. We searched all published literature on post-treatment PR, and present a synthesis of 30 studies, focusing on the epidemiology, diagnosis and management of this phenomenon. We report an additional case vignette. The majority of studies were of lymph node TB (LN-TB), followed by central nervous system TB (CNS-TB). A total of 112 confirmed and 42 possible post-treatment PR cases were reported. The incidence ranged between 3 and 14% in LN-TB and was more frequent than relapses, and between 0 and 2% in all TB. We found four reports of pulmonary or pleural TB post-treatment PR cases. The incidence did not differ by length of treatment, but was associated with younger age at initial diagnosis, and having had a PR (later) during treatment. Post-treatment PR developed mainly within the first 6 months after the end of TB treatment but has been reported many years later (longest report 10 years). The mainstays of diagnosis and management are negative mycobacterial cultures and anti-inflammatory treatment, respectively. Due to the favourable prognosis in LN-TB recurrent symptoms, a short period of observation is warranted to assess for spontaneous regression. In CNS-TB with recurrent symptoms, immediate investigation and anti-inflammatory treatment with the possibility of TB retreatment should be undertaken.

Role of [18F]FDG - PET/CT Scan in Cervical Tuberculosis

Background

Distribution and quantification of extra-pulmonary tuberculosis and elicitation of response antitubercular therapy via F18-Fluorodeoxyglucose Positron Emission-based Tomography/ Computed Tomography(F18-FDG PET/CT).

Materials and Methods

This was a prospective Pilot study. In this study 30 patients of age between 15 to 36 years(mean 26.8±6.13years) were included. PET/CT scan was performed at the time of presentation(baseline) and after 2 months of anti-tubercular therapy to evaluate bacterial activity in different levels of cervical lymph nodes and changes in various parameters of lymph nodes such as size, conglomeration and abscess formation were included in the evaluation.

Result

In this study, 18 patients were of 18 to 30 years(60.0%), 3 patients were below 18 years(10.0%) and 9 patients above 30 years(30%). The female proportion was higher in our study population(53.3%). Node-positive status, conglomeration, and abscess were evaluated clinically. Maximum percentages were found in level II and level V groups. While minimum percentage was found in level I and level VI. We also found that in all patients of tubercular cervical lymphadenopathy, tubercular bacterial activity was found at some distant sites also the common sites were the lung(56.7%), mediastinum(53.3%), abdomen(36.7%) and bone(23.3%). The response of antitubercular therapy by F18 - FDG PET/CT scan after 2 months of treatment was checked. There was a significant change in standardized uptake value(SUV-max) pre-treatment and post-treatment at all distant sites except the bony site.

Conclusion

F18-FDG PET/CT scan is a non-invasive tool in monitoring the response of antitubercular chemotherapy in patients of extrapulmonary and multiorgan lymphadenopathy.

Does PET-CT Have a Role in the Evaluation of Tuberculosis Treatment in Phase 2 Clinical Trials?

Positron emission tomography-computed tomography (PET-CT) has the potential to revolutionize research in infectious diseases, as it has done with cancer. There is growing interest in it as a biomarker in the setting of early-phase tuberculosis clinical trials, particularly given the limitations of current biomarkers as adequate predictors of sterilizing cure for tuberculosis. PET-CT is a real-time tool that provides a 3-dimensional view of the spatial distribution of tuberculosis within the lung parenchyma and the nature of lesions with uptake (ie, whether nodular, consolidative, or cavitary). Its ability to provide functional data on changes in metabolism, drug penetration, and immune control of tuberculous lesions has the potential to facilitate drug development and regimen selection for advancement to phase 3 trials in tuberculosis. In this narrative review, we discuss the role that PET-CT may have in evaluating responses to drug therapy in active tuberculosis treatment and the challenges in taking PET-CT forward as predictive biomarker of relapse-free cure in the setting of phase 2 clinical trials.

Clinical application of Mycobacterium RT-PCR assay using various specimens for the rapid detection of lymph node tuberculosis: A diagnostic accuracy study

To evaluate the diagnostic accuracy of the Capital Bio Mycobacterium real-time polymerase chain reaction assay Capital Bio assay for lymph node (LN) tuberculosis (LNTB), and to further compare the effect of different types of LN specimens on the detection capability of the test. We retrospectively analyzed the medical records of LNTB patients who met the inclusion criteria. The sensitivity, specificity, positive predictive value, negative predictive value, and area under the curve of Capital Bio assay were calculated to evaluate its diagnostic accuracy compared with the final clinical diagnosis as reference standard. Three hundred sixty-four patients were included in the study. The overall sensitivity, specificity, positive predictive value, negative predictive value, and area under the curve of the Capital Bio assay for LNTB were 74.4%, 100.0%, 100.0%, 34.9%, and 0.87, respectively. For the pus specimens, these values for Capital Bio assay were 93.2%, 100.0%, 100.0%, 27.3%, 0.97, respectively. For the core needle biopsy specimens, these values were 65.9%, 100.0%, 100.0%, 33.3%, and 0.83, respectively. For the fine-needle aspiration specimens, these values were 60.0%, 100.0%, 100.0%, 53.9%, and 0.80, respectively. For the tissue, these values were 59.3%, 100.0%, 100.0%, 33.3%, 0.80, respectively. The Capital Bio assay had good effective for the diagnosis of LNTB. Compared to LN fine-needle aspiration and core needle biopsy specimens and tissue specimens, pus specimens were more suitable for molecular testing and had the best diagnostic efficacy.

Molecular Imaging of Tuberculosis

Despite the introduction of many novel diagnostic techniques and newer treatment agents, tuberculosis (TB) remains a major cause of death from an infectious disease worldwide. With about a quarter of humanity harboring Mycobacterium tuberculosis, the causative agent of TB, the current efforts geared towards reducing the scourge due to TB must be sustained. At the same time, newer alternative modalities for diagnosis and treatment response assessment are considered. Molecular imaging entails the use of radioactive probes that exploit molecular targets expressed by microbes or human cells for imaging using hybrid scanners that provide both anatomic and functional features of the disease being imaged. Fluorine-18 fluorodeoxyglucose (FDG) is the most investigated radioactive probe for TB imaging in research and clinical practice. When imaged with positron emission tomography interphase with computed tomography (PET/CT), FDG PET/CT performs better than sputum conversion for predicting treatment outcome. At the end of treatment, FDG PET/CT has demonstrated the unique ability to identify a subset of patients declared cured based on the current standard of care but who still harbor live bacilli capable of causing disease relapse after therapy discontinuation. Our understanding of the pathogenesis and evolution of TB has improved significantly in the last decade, owing to the introduction of FDG PET/CT in TB research. FDG is a non-specific probe as it targets the host inflammatory response to Mycobacterium tuberculosis, which is not specifically different in TB compared with other infectious conditions. Ongoing efforts are geared towards evaluating the utility of newer probes targeting different components of the TB granuloma, the hallmark of TB lesions, including hypoxia, neovascularization, and fibrosis, in TB management. The most exciting category of non-FDG PET probes developed for molecular imaging of TB appears to be radiolabeled anti-tuberculous drugs for use in studying the pharmacokinetic characteristics of the drugs. This allows for the non-invasive study of drug kinetics in different body compartments concurrently, providing an insight into the spatial heterogeneity of drug exposure in different TB lesions. The ability to repeat molecular imaging using radiolabeled anti-tuberculous agents also offers an opportunity to study the temporal changes in drug kinetics within the different lesions during treatment.

Kimura disease, a rare cause of inguinal lymphadenopathy: A case report

Kimura’s disease (KD) is a rare chronic granulomatous disease of unknown etiology that mainly involves damage to lymph nodes, soft tissues, and salivary glands. The clinical symptoms are mainly painless subcutaneous soft tissue masses, often involving head and neck lymph nodes and salivary glands, and are mainly characterized by diffuse eosinophilic infiltration, lymphocyte, and vascular proliferation. There are few reports in the literature that KD affects only inguinal lymph nodes. We report in this study a 41-year-old male patient who presented to the hospital for medical help with soft tissue masses in the groin. Magnetic resonance imaging (MRI) showed multiple abnormal soft tissue nodules around the iliac vessels in the left groin, and a contrast-enhanced scan showed obvious homogeneous enhancement. Diffusion-weighted imaging showed limited movement of water molecules and showed an obvious high signal. Fluoro18-labeled deoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) was recommended for further evaluation of the patient’s general condition, and the results showed that except for the radioactive uptake in the lesions in the left groin region, no obvious abnormality was found in the rest of the body. Based on these imaging findings, the patient was first suspected to have malignant lesions, and then the patient underwent histopathological examination, which was confirmed to be KD. Our case study suggests that KD affects only the inguinal lymph nodes is rare and should be considered as one of the imaging differential diagnoses for lymphadenopathy such as lymphoma, metastases, and Castleman’s disease.

[ 18 F]FDG Positron Emission Tomography for Initial Staging and Healing Assessment at the End of Therapy in Lymph Nodes and Bone Tuberculosis

Objective: In extra-pulmonary tuberculosis, therapeutic management is difficult in the absence of reliable tool to affirm healing at the end of treatment. In this prospective multicenter study, we evaluated [¹⁸F]FDG-PET for this purpose.

Methods: Forty-two patients out of 55 included patients could be analyzed. Additionally to usual biological, histological and morphological explorations, [¹⁸F]FDG-PET was performed at diagnosis (PET1), at the end of treatment (PET2), indeed 6 months later. Then patients were followed until 12 months after end of prescribed treatment.

Results: PET1 was positive in 97.6% of patients and discovered unknown injured sites in 52.7% of cases. PET2 was positive in 83.3% of uncured patients, and in 82.3% of cured patients. The sum and mean value of SUV_max measured in PET/CT lesions decreased between PET1 and PET2 in all patients. Mean value of SUV_max (MSUV) and sum value of SUVmax on PET2 showed the highest AUC on ROC curves for the diagnosis of healing at the end of prescribed treatment; MSUV 3.5 on PET2 had a sensitivity of 76.5% and a specificity of 80.0% to affirm healing at the end of prescribed treatment.

Conclusions: [¹⁸F]FDG-PET/CT was useful at diagnosis, discovering unknown lesions in 52.7% of cases. MSUV on PET2 was the best criteria to affirm healing at the end of prescribed treatment.

State of the art of 18F-FDG PET/CT application in inflammation and infection: a guide for image acquisition and interpretation

AIM

The diagnosis, severity and extent of a sterile inflammation or a septic infection could be challenging since there is not one single test able to achieve an accurate diagnosis. The clinical use of 18F-fluorodeoxyglucose ([18F]FDG) positron emission tomography/computed tomography (PET/CT) imaging in the assessment of inflammation and infection is increasing worldwide. The purpose of this paper is to achieve an Italian consensus document on [18F]FDG PET/CT or PET/MRI in inflammatory and infectious diseases, such as osteomyelitis (OM), prosthetic joint infections (PJI), infective endocarditis (IE), prosthetic valve endocarditis (PVE), cardiac implantable electronic device infections (CIEDI), systemic and cardiac sarcoidosis (SS/CS), diabetic foot (DF), fungal infections (FI), tuberculosis (TBC), fever and inflammation of unknown origin (FUO/IUO), pediatric infections (PI), inflammatory bowel diseases (IBD), spine infections (SI), vascular graft infections (VGI), large vessel vasculitis (LVV), retroperitoneal fibrosis (RF) and COVID-19 infections.

METHODS

In September 2020, the inflammatory and infectious diseases focus group (IIFG) of the Italian Association of Nuclear Medicine (AIMN) proposed to realize a procedural paper about the clinical applications of [18F]FDG PET/CT or PET/MRI in inflammatory and infectious diseases. The project was carried out thanks to the collaboration of 13 Italian nuclear medicine centers, with a consolidate experience in this field. With the endorsement of AIMN, IIFG contacted each center, and the pediatric diseases focus group (PDFC). IIFG provided for each team involved, a draft with essential information regarding the execution of [18F]FDG PET/CT or PET/MRI scan (i.e., indications, patient preparation, standard or specific acquisition modalities, interpretation criteria, reporting methods, pitfalls and artifacts), by limiting the literature research to the last 20 years. Moreover, some clinical cases were required from each center, to underline the teaching points. Time for the collection of each report was from October to December 2020.

RESULTS

Overall, we summarized 291 scientific papers and guidelines published between 1998 and 2021. Papers were divided in several sub-topics and summarized in the following paragraphs: clinical indications, image interpretation criteria, future perspectivess and new trends (for each single disease), while patient preparation, image acquisition, possible pitfalls and reporting modalities were described afterwards. Moreover, a specific section was dedicated to pediatric and PET/MRI indications. A collection of images was described for each indication.

CONCLUSIONS

Currently, [18F]FDG PET/CT in oncology is globally accepted and standardized in main diagnostic algorithms for neoplasms. In recent years, the ever-closer collaboration among different European associations has tried to overcome the absence of a standardization also in the field of inflammation and infections. The collaboration of several nuclear medicine centers with a long experience in this field, as well as among different AIMN focus groups represents a further attempt in this direction. We hope that this document will be the basis for a "common nuclear physicians' language" throughout all the country.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40336-021-00445-w.

Role of 18F-FDG PET/CT in the Assessment of Response to Antitubercular Chemotherapy and Identification of Treatment Endpoint in Patients With Tuberculosis of the Joints: A Pilot Study

AIMS

The aim of this study was to explore the utility of 18F-FDG PET/CT in the assessment of response to antitubercular treatment (ATT) and identification of treatment endpoint.

PATIENTS AND METHODS

Forty patients (mean age, 35.3 years; 27 men) with clinically, radiologically, and histopathologically proven joint tuberculosis prospectively underwent clinical, biochemical, and PET/CT evaluation at baseline and after ~6, 12, and 18 months of ATT. Two patients were lost to follow-up, and 1 defaulted treatment. The remaining 37 were followed up until complete response (CR) was achieved. Images were visually and quantitatively (SUVmax ratio and metabolically active disease volume [MV]) evaluated by 2 experienced nuclear medicine physicians.

RESULTS

Knee (n = 18) and ankle (n = 7) were the most frequently involved sites. The median MV and SUVmax ratio at baseline were 85.10 mL and 7.21, respectively. Five patients had noncontiguous vertebral involvement, 12 had pulmonary lesions, 2 had abscesses, 6 had mediastinal, and 30 had local lymph nodal involvement. Complete response was seen in 1/39, 11/37, and 30/37 patients after 6, 12, and 18 months of ATT. Significant reductions in visual analog scale score, tenderness, joint swelling, SUVmax ratios, and MVs (Friedman test, P < 0.001) were seen after each follow-up. The median time-to-CR in skeletal lesions was significantly longer than extraskeletal lesions (591 vs 409 days; Wilcoxon signed-rank test, P < 0.001). Time-to-CR in joint lesions positively correlated with MV at first follow-up (Pearson = 0.452, P = 0.005) and negatively correlated with percentage change in MV (first follow-up from baseline) (Pearson = -0.620, P < 0.001). ROC analysis yielded a cutoff of ≤71% reduction in MV at first follow-up (80.8% sensitivity, 81.8% specificity) to predict extension of ATT beyond 12 months. Using ROC analysis at second follow-up, a cutoff of ≤12.67 mL (for CR) was derived and was validated in patients at the third follow-up, with an accuracy of 84.4%. Patients with CR in PET/CT maintained disease-free state during a mean follow-up of 271 days.

CONCLUSIONS

18F-FDG PET/CT is an excellent tool in estimating total disease burden, assessing response to ATT and identification of treatment endpoint in joint tuberculosis.

Splenic uptake on FDG PET/CT correlates with Kikuchi-Fujimoto disease severity

Kikuchi-Fujimoto disease (KFD) is usually self-limiting, but prolonged systemic symptoms often result in frequent hospital visits, long admission durations, or missed workdays. We investigated the role of fluorine-18 fluoro-2-deoxy-D-glucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) in assessing KFD severity. We reviewed the records of 31 adult patients with pathologically confirmed KFD who underwent ¹⁸F-FDG PET/CT between November 2007 and April 2018 at a tertiary-care referral hospital. Disease severity was assessed using criteria based on clinical manifestations of advanced KFD. Systemic activated lymph nodes and severity of splenic activation were determined using semi-quantitative and volumetric PET/CT parameters. The median of the mean splenic standardized uptake value (SUV_mean) was higher in patients with severe KFD than those with mild KFD (2.38 ± 1.18 vs. 1.79 ± 0.99, p = 0.058). Patients with severe KFD had more systemically activated volume and glycolytic activity than those with mild KFD (total lesion glycolysis: 473.5 ± 504.4 vs. 201.6 ± 363.5, p = 0.024). Multivariate logistic regression showed that myalgia (odds ratio [OR] 0.035; 95% confidence interval [CI] 0.001–0.792; p = 0.035), total lymph node SUV_max (cutoff 9.27; OR 24.734; 95% CI 1.323–462.407; p = 0.032), and spleen SUV_mean (cutoff 1.79; OR 37.770; 95% CI 1.769–806.583; p = 0.020) were significantly associated with severe KFD. ¹⁸F-FDG PET/CT could be useful in assessing KFD severity.

Lung Injury on Antiretroviral Therapy in Adults With Human Immunodeficiency Virus/Tuberculosis

BACKGROUND

Immune restoration on antiretroviral therapy (ART) can drive inflammation in people living with human immunodeficiency virus (HIV) who have pulmonary tuberculosis (TB), but its effects on the lungs have not been assessed. We evaluated associations between pulmonary inflammation, recovery of pathogen-specific CD4 T-cell function, and lung injury prior to and after ART initiation in adults with HIV and pulmonary TB.

METHODS

This was a prospective cohort study in South Africa, following adults with HIV and pulmonary TB prior to and up to 48 weeks after ART initiation. Pulmonary-specific inflammation was defined as total glycolytic activity (TGA) on [18]F-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) at baseline and 4 weeks after ART initiation. Spirometry, respiratory symptom tests, and flow cytometry were performed at the same times to assess lung involvement and the frequency of mycobacteria-specific CD4 T-cells. In addition, we evaluated lung function longitudinally up to 48 weeks after ART initiation.

RESULTS

Greater lung TGA on FDG PET-CT was associated with worse lung function and respiratory symptoms prior to ART initiation, and nearly half of subjects experienced worsening lung inflammation and lung function at Week 4 of ART. Worsening Week 4 lung inflammation and pulmonary function were both associated with greater increases in pathogen-specific functional CD4 T-cell responses on ART, and early decreases in lung function were independently associated with persistently lower lung function months after TB treatment completion.

CONCLUSIONS

Increases in pulmonary inflammation and decreases in lung function are common on ART, relate to greater ART-mediated CD4 T-cell restoration, and are associated with the persistent impairment of lung function in individuals with HIV/TB.

Novel Quantitative PET Imaging Techniques in Tuberculosis

The role of fluorodeoxyglucose (FDG)-PET/computed tomography (CT) in tuberculosis (TB) continues to expand in disease detection, assessment of the extent of the disease, and treatment response monitoring. This article reviews available data regarding the use of FDG-PET/CT in patients with TB. A new method of quantification for patients with TB is introduced. This method produces robust parameters that represent the total disease burden.

Mycobacterial Lymphadenitis in a Human Immunodeficiency Virus-Infected Patient: Usefulness of 18F-Fluorodeoxyglucose Positron Emission Tomography for Diagnosis and Monitoring the Response to Treatment

Lymphadenitis, due to typical or atypical Mycobacterium, is a clinical condition frequently associated with human immunodeficiency virus (HIV) infection. Differential diagnosis between benign and malignant causes may be a challenge for clinicians. In this regard, the role of positron emission tomography (PET) with ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) has still not been fully explored. We describe a case of 30-year-old male, infected by HIV, with mycobacterial lymphadenitis, in which ¹⁸FDG-PET and PET-derived parameters resulted useful for guiding diagnosis and monitoring the response to treatment.

Usefulness of FDG PET/CT in the management of tuberculosis

Background

The aim of our study is to describe the FDG-PET/CT findings in patients with tuberculosis and to correlate them with the patient’s prognosis.

Methods

We retrospectively collected data from patients with tuberculosis, who had an FDG-PET/CT performed prior to treatment initiation from 2010 to 2015.

Results

Forty-seven out of 504 patients with active tuberculosis diagnosis (9.33%) underwent an FDG-PET/CT. The reasons for performing the FDG-PET/CT were: characterization of a pulmonary nodule (24; 51.1%), study of fever of unknown origin (12; 25.5%), study of lymph node enlargement (5; 10.6%) and others (6; 12.8%). Median age was 64 (IQR 50–74) years and 31 (66%) patients were male. Twenty-six (55.3%) patients had an immunosuppressant condition. According to the FDG-PET/CT, 48.6% of the patients had more than 1 organ affected and 46.8% had lymph node involvement. Median SUVmax of the main lesion was 5 (IQR 0.28–11.85). We found an association between the FDG accumulation and the size of the main lesion with a correlation coefficient of 0.54 (p<0.002). Patients with an unsuccessful outcome had a higher ratio SUVmax main lesion / SUVmean liver (1.92 vs 7.67, p<0.02).

Conclusions

In our cohort, almost half of the patients had more than 1 organ affected and 46.8% of them had lymph node involvement. FDG uptake was associated with the size of the main lesion and seems to be related to the treatment outcome. The extent of its potential to be used as an early predictor of treatment success still needs to be defined.

18F-FDG PET/CT as a Noninvasive Biomarker for Assessing Adequacy of Treatment and Predicting Relapse in Patients Treated for Pulmonary Tuberculosis

Microbial culture is the gold standard for determining the effectiveness of tuberculosis treatment. End-of-treatment (EOT) ¹⁸F-FDG PET/CT findings are variable among patients with negative microbial culture results after completing a standard regimen of antituberculous treatment (ATT), with some patients having a complete metabolic response to treatment whereas others have residual metabolic activity (RMA). We herein determine the impact of findings on EOT ¹⁸F-FDG PET/CT on tuberculosis relapse in patients treated with a standard regimen of ATT for drug-sensitive pulmonary tuberculosis (DS-PTB). Methods: Patients who completed a standard regimen of ATT for DS-PTB and were declared cured based on a negative clinical and bacteriologic examination were prospectively recruited to undergo EOT ¹⁸F-FDG PET/CT. Images were assessed for the presence of RMA. Patients were subsequently followed up for 6 mo looking for symptoms of tuberculosis relapse. When new symptoms developed, relapse was confirmed with bacteriologic testing. Repeat ¹⁸F-FDG PET/CT was done in patients who relapsed. Results: Fifty-three patients were included (mean age, 37.81 ± 11.29 y), with 62% being male and 75% HIV-infected. RMA was demonstrated in 33 patients (RMA group), whereas 20 patients had a complete metabolic response to ATT (non-RMA group). There was a higher prevalence of lung cavitation in the RMA group (P = 0.035). The groups did not significantly differ in age, sex, presence of HIV infection, body mass index, or hemoglobin level (P > 0.05). On follow-up, no patients in the non-RMA group developed tuberculosis relapse. Three patients in the RMA group developed relapse. All patients who developed tuberculosis relapse had bilateral disease with lung cavitation. Conclusion: A negative EOT ¹⁸F-FDG PET/CT result is protective against tuberculosis relapse. Nine percent of patients with RMA after ATT may experience tuberculosis relapse within 6 mo of completing ATT. Bilateral disease with lung cavitation is prevalent among patients with tuberculosis relapse.

Severe disseminated tuberculosis in HIV-negative refugees

In high-income countries, the presentation of tuberculosis is changing, primarily because of migration, and understanding the specific health needs of susceptible populations is becoming increasingly important. Although disseminated tuberculosis is well documented in HIV-positive patients, the disease is poorly described and less expected in HIV-negative individuals. In this Grand Round, we report eight HIV-negative refugees, who presented with extensively disseminated tuberculosis. We discuss the multifactorial causes, such as deprivations during long journeys, precarious living conditions, and the experience of violence, which might add to nutritional factors and chronic disorders, eventually resulting in a state of predisposition to immune deficiency. We also show that disseminated tuberculosis is often difficult to diagnose when pulmonary symptoms are absent. Communication difficulties between refugees and health-care workers are another major hurdle, and every effort should be made to get a valid patient history. This medical history is crucial to guide imaging and other diagnostic procedures to establish a definite diagnosis, which should be confirmed by a positive tuberculosis culture. Because many of these patients are at risk for multidrug-resistant tuberculosis, drug susceptibility testing is imperative to guide therapy. In the absence of treatment guidelines for this entity, clinicians can determine treatment duration according to recommendations provided for extrapulmonary tuberculosis and affected organs. Paradoxical expansion of tuberculous lesions during therapy should be treated with corticosteroids. In many cases, treatment duration must be individualised and might even exceed 12 months.

Updates on 18F-FDG-PET/CT as a clinical tool for tuberculosis evaluation and therapeutic monitoring

Tuberculosis (TB) is currently the world's leading cause of infectious mortality. The complex immune response of the human body to Mycobacterium tuberculosis (M.tb) results in a wide array of clinical manifestations, thus the clinical and radiological diagnosis can be challenging. ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG-PET) scan with/without computed tomography (CT) component images the whole body and provides a metabolic map of the infection, enabling clinicians to assess the disease burden. ¹⁸F-FDG-PET/CT scan is particularly useful in detecting the disease in previously unknown sites, and allows the most appropriate site of biopsy to be selected. ¹⁸F-FDG-PET/CT is also very valuable in assessing early disease response to therapy, and plays an important role in cases where conventional microbiological methods are unavailable and for monitoring response to therapy in cases of multidrug-resistant TB or extrapulmonary TB. ¹⁸F-FDG-PET/CT cannot reliably differentiate active TB lesion from malignant lesions and false positives can also be due to other infective or inflammatory conditions. ¹⁸F-FDG PET is also unable to distinguish tuberculous lymphadenitis from metastatic lymph node involvement. The lack of specificity is a limitation for ¹⁸F-FDG-PET/CT in TB management.

Delays in the Diagnosis and Treatment of Tuberculous Lymphadenitis in Low-Incidence Countries: A Systematic Review

Early detection and treatment of tuberculosis (TB) is essential to achieve the goals appointed in the WHO End TB Strategy. Tuberculous lymphadenitis (TBLA) is the most common manifestation of extrapulmonary TB, but the diagnosis can be challenging in low-incidence countries due to sparse and inconsistent clinical features, resulting in delay. We aimed to summarize and discuss the current literature on patient delay, health care delay, and total delay (i.e., time to first health care contact, diagnosis, and treatment) in patients with TBLA in TB low-incidence countries. A systematic review using PubMed was conducted, searching for studies set in TB low-incidence countries (defined as <20 per 100,000 citizens) that reported on health care seeking behaviour, patient delay, health care delay, and/or total delay. Studies were categorized by type of delay and compared. We identified 11 heterogeneous studies with highly variable observations. Mean patient delay varied from 55 to 154 days (range, 14-1,461), mean health care delay from 44 to 94 days (range, 7-224) and median total delay from 77.5 to 122 days (range, 0-2,820). Evidently, more comprehensive insights into the diagnostic pathway and delay in TBLA patients are warranted.

Prospective Serial FDG PET/CT During Treatment of Extrapulmonary Tuberculosis in HIV-Infected Patients: An Exploratory Study

PURPOSE

The aim of this study was to prospectively describe evolution of F-FDG uptake of extrapulmonary tuberculosis (TB) throughout the course of TB treatment in HIV patients to evaluate F-FDG PET/CT as a monitoring tool of treatment response.

METHODS

We performed baseline FDG PET/CT, PET-2 after 2 months, and PET-3 at the end of TB treatment in 18 HIV/TB patients. We correlated evolution of FDG uptake with clinical outcome of patients.

RESULTS

After 2 months of treatment, 78% of the patients had a significant metabolic response. Lymph node (LN) metabolic response was heterogeneous, with 57% of LN sites showing decreased SUVmax and 41% showing unchanged FDG uptake. Organs other than LNs showed more homogeneous response. The FDG PET/CT performed at the end of TB treatment showed a complete response of all infected organs and a drastic response in terms of active LNs in 95% of the patients (SUVmax mean decrease = 85%, median = 100%). A complete metabolic response after TB treatment was seen in only 47% of patients.

CONCLUSIONS

In difficult-to-treat entities such as extrapulmonary TB in HIV patients, FDG PET/CT is a potential tool in monitoring TB treatment response and should be explored in larger studies.

18F-FDG PET/CT for invasive fungal infection in immunocompromised patients

BACKGROUND

Opportunistic invasive fungal infections (IFIs) comprise a heterogeneous spectrum of pathogens, whose early diagnosis remains challenging. Candida spp. and Aspergillus spp, the most frequent pathogens in immunocompromised patients, frequently affect lungs, liver, bone and skin.

AIM

To evaluate the impact of 18F-FDG PET/CT in the management of immunocompromised patients with IFI.

DESIGN

A single-center retrospective study included 51 immunocompromised patients with IFI diagnosis undergoing 83 18F-FDG PET/CTs.

METHODS

Twenty-nine 18F-FDG PET/CTs were performed for primary work-up in 29 treatment-naïve patients. Fifty-four PET/CTs were performed during follow-up to confirm IFI suspicion in 22 patients who had anti-fungal drug therapy before PET/CT. When available, histological and/or microbiological criteria were used to assess IFI diagnosis.

RESULTS

Aspergillus spp. and Candida spp. were the most frequent microorganisms responsible for IFI in our population. 18F-FDG PET/CT sensitivity, specificity, positive and negative predictive values, and global accuracy were 93%, 81%, 95%, 72% and 90%, respectively. 18F-FDG PET/CT influenced the diagnostic work-up at primary staging in 16/29 patients (55%) by assessing the extent of infection and targeting the diagnostic procedure. 18F-FDG PET/CT results during treatment induced anti-fungal drugs dosage increase and/or new drugs addition in 8/54 cases (15%) and contributed to the reduction of anti-fungal drugs dosage or treatment withdraws in 17 cases (31%).

CONCLUSIONS

We recommend the utilization of 18F-FDG PET/CT to improve the primary staging work-up of immunocompromised patients with IFI and to assess treatment effectiveness or disease relapse. Both 18F-FDG PET/CT and conventional imaging should be integrated into a well-defined imaging diagnostic algorithm considering the clinical context and both strengths and limitations of each diagnostic modality.

Delayed diagnosis of extrapulmonary tuberculosis presenting as fever of unknown origin in an intermediate-burden country

Background

Tuberculosis (TB), especially extrapulmonary tuberculosis (EPTB), is an important cause of fever of unknown origin (FUO) in TB-burdened areas. Little information is known about patients with EPTB with clinical features presenting as FUO and about the factor of delaying the diagnosis.

Methods

We retrospectively analyzed EPTB patients who were referred with FUO at 3 university-affiliated hospitals over 8 years (2010–2017). The subjects were assigned to groups of early diagnosis and delayed diagnosis within 3 days of an initial comprehensive evaluation from the referral. Clinical and laboratory variables were compared between the groups.

Results

A total of 95 patients with febrile EPTB were included. Localizing symptoms and/or signs suggestive of anatomy were identified in 62.1% of the patients. Concurrent lung involvement by TB was presented by 49.5% (47/95) of the patients, and only 23.4% of them showed typical findings of pulmonary TB on simple chest X-ray. Most of the patients showed abnormal lesions on cross-sectional CT (98.9%) and MRI (100%). The clinical variables and blood test results of patients were not significantly different between the two groups. The less typical imaging finding of EPTB on CT (38.5% vs. 79.0%) and MRI (37.5% vs. 79.0%) in the delayed diagnosis group was a risk factor for delayed diagnosis.

Conclusion

Febrile EPTB referred as FUO showed nonspecific clinical manifestations. The active application of cross-sectional imaging tests according to clinical clues or randomly in the absence of local manifestations, combined with invasive diagnostic approaches even for atypical presentations may lead to an earlier diagnosis of febrile EPTB.

The potential of imaging tools as correlates of infection and disease for new TB vaccine development

The development of an improved vaccine to stimulate an effective response against Mycobacterium tuberculosis (MTB) infection and disease will be a major breakthrough in the fight against TB. A lack of tools to adequately track the progression or resolution of events in TB pathogenesis that occur at bacterial loads below the threshold for culture in human samples seriously hampers vaccine development and evaluation. In this review we discuss recent studies that use new imaging applications, modalities and analysis techniques to provide insight into the dynamic processes of MTB infection and disease that are challenging to monitor. These include early infection, the spectrum of latency and subclinical disease, the paucibacillary state induced by treatment, and events leading to recurrence, including relapse.

The role of FDG PET/CT in therapy control of aortic graft infection

PURPOSE

¹⁸F-FDG PET/CT (PET/CT) is a useful tool for the diagnosis of aortic graft infection (AGI), but has rarely been used to influence therapeutic decisions during follow-up. We aimed to study the role of PET/CT in the long-term monitoring of patients.

METHODS

Participants of the prospective Vascular Graft Infection Cohort Study (VASGRA) were included if they had microbiologically proven AGI. We quantified the metabolic activity in PET/CT by using maximum standardized uptake value (SUV_max) and further classified it as being focal or diffuse. Multivariable linear regression models were fit using generalized estimating equations to investigate factors associated with SUV_max over time.

RESULTS

Sixty-eight participants with AGI contributed to 266 PET/CTs including 36 examinations performed after stop of antimicrobial therapy. Higher C-reactive protein (CRP) (adjusted coefficient per log₁₀ mg/L 0.05 [95% C.I. 0.02-0.08]) was associated with higher SUV_max. CRP, metabolic and clinical findings informed the decision to either start (medians of SUV_max 7.1 and CRP 31.5 mg/L; 100% focal uptake), escalate (SUV_max 9.5; CRP 31.5; 100% focal uptake), continue (SUV_max 6.0; CRP 9.95 mg/L; 90% focal uptake), or stop (SUV_max 4.3; CRP 3.5 mg/L; 61% focal uptake) antibiotic treatment. Of note, decisions to escalate or continue antibiotic treatment were taken despite normal CRP values in 12.5 and 35.7% of PET/CTs, respectively.

CONCLUSIONS

Consecutive PET/CTs could influence the clinical decision-making in patients with AGI in the near future. More studies on the use of PET/CT in case of aortic graft infection may offer the potential for individualized treatment approaches. CLINICALTRIALS.

GOV IDENTIFIER

NCT01821664.

Tuberculosis

Tuberculosis (TB) is currently the world's leading cause of infectious mortality. Imaging plays an important role in the management of this disease. The complex immune response of the human body to Mycobacterium tuberculosis results in a wide array of clinical manifestations, making clinical and radiological diagnosis challenging. ¹⁸F-FDG-PET/CT is very sensitive in the early detection of TB in most parts of the body; however, the lack of specificity is a major limitation. ¹⁸F-FDG-PET/CT images the whole body and provides a pre-therapeutic metabolic map of the infection, enabling clinicians to accurately assess the burden of disease. It enables the most appropriate site of biopsy to be selected, stages the infection, and detects disease in previously unknown sites. ¹⁸F-FDG-PET/CT has recently been shown to be able to identify a subset of patients with latent TB infection who have subclinical disease. Lung inflammation as detected by ¹⁸F-FDG-PET/CT has shown promising signs that it may be a useful predictor of progression from latent to active infection. A number of studies have identified imaging features that might improve the specificity of ¹⁸F-FDG-PET/CT at some sites of extrapulmonary TB. Other PET tracers have also been investigated for their use in TB, with some promising results. The potential role and future perspectives of PET/CT in imaging TB is considered. Literature abounds on the very important role of ¹⁸F-FDG-PET/CT in assessing therapy response in TB. The use of ¹⁸F-FDG for monitoring response to treatment is addressed in a separate review.

Monitoring Response to Therapy

Monitoring response to treatment is a key element in the management of infectious diseases, yet controversies still persist on reliable biomarkers for noninvasive response evaluation. Considering the limitations of invasiveness of most diagnostic procedures and the issue of expression heterogeneity of pathology, molecular imaging is better able to assay in vivo biologic processes noninvasively and quantitatively. The usefulness of ¹⁸F-FDG-PET/CT in assessing treatment response in infectious diseases is more promising than for conventional imaging. However, there are currently no clinical criteria or recommended imaging modalities to objectively evaluate the effectiveness of antimicrobial treatment. Therapeutic effectiveness is currently gauged by the patient's subjective clinical response. In this review, we present the current studies for monitoring treatment response, with a focus on Mycobacterium tuberculosis, as it remains a major worldwide cause of morbidity and mortality. The role of molecular imaging in monitoring other infections including spondylodiscitis, infected prosthetic vascular grafts, invasive fungal infections, and a parasitic disease is highlighted. The role of functional imaging in monitoring lipodystrophy associated with highly active antiretroviral therapy for human immunodeficiency virus is considered. We also discuss the key challenges and emerging data in optimizing noninvasive response evaluation.

Metabolic Imaging of Infection

Metabolic imaging has come to occupy a prominent place in the diagnosis and management of microbial infection. Molecular probes available for infection imaging have undergone a rapid evolution starting with nonspecific agents that accumulate similarly in infection, sterile inflammation, and neoplastic tissue and then extending to more targeted probes that seek to identify specific microbial species. This focus review describes the metabolic and molecular imaging techniques currently available for clinical use in infection imaging and those that have demonstrated promising results in preclinical studies with the potential for clinical applications.