The Role of Fibroblast Activation Protein Inhibitor Positron Emission Tomography in Inflammatory and Infectious Diseases: An Updated Systematic Review.

The role of fibroblast activation protein inhibitor (FAPI) positron emission tomography/computed tomography (PET/CT) is emerging for the assessment of non-oncological diseases, such as inflammatory and infectious diseases, even if the evidence in the literature is still in its initial phases. We conducted a systematic search of Scopus, PubMed/MEDLINE, Embase, and Cochrane library databases for studies published before 31 December 2023 reporting infectious and inflammatory disease imaging with FAPI PET/CT. We included twenty-one studies for a total of 1046 patients. The most frequent disease studied was lung interstitial disease, investigated in six studies for a total of 200 patients, followed by bone and joint diseases in two studies and 185 patients, IgG4-related disease in 53 patients, and Crohn's disease in 30 patients. Despite the heterogeneity of studies in terms of study design and technical features, FAPI PET/CT showed a high detection rate and diagnostic role. Moreover, when compared with 2-[18F]FDG PET/CT (n = 7 studies), FAPI PET/CT seems to have better diagnostic performances. The presence of chronic inflammation and tissue remodeling, typical of immune-mediated inflammatory conditions, may be the underlying mechanism of FAPI uptake.

Incidental Findings Suggestive of COVID-19 Pneumonia in Oncologic Patients Undergoing 18F-FDG PET/CT Studies: Association Between Metabolic and Structural Lung Changes.

Although the novel coronavirus disease 2019 (COVID-19) can present as nonspecific clinical forms, subclinical cases represent an important route of transmission and a significant source of mortality, mainly in high-risk subpopulations such as cancer patients. A deeper knowledge of the metabolic shift in cells infected with severe acute respiratory syndrome coronavirus 2 could provide new insights about its pathogenic and host response and help to diagnose pulmonary involvement. We explored the potential added diagnostic value of 18F-FDG PET/CT scans in asymptomatic cancer patients with suspected COVID-19 pneumonia by investigating the association between metabolic and structural changes in the lung parenchyma. Methods:18F-FDG PET/CT studies acquired between February 19 and May 29, 2020, were reviewed to identify those cancer patients with incidental findings suggestive of COVID-19 pneumonia. PET studies were interpreted through qualitative (visual) and semiquantitative (measurement of SUVmax) analysis evaluating lung findings. Several characteristic signs of COVID-19 pneumonia on CT were described as COVID-19 Reporting and Data System (CO-RADS) categories (1-6). After comparing the SUVmax of pulmonary infiltrates among different CO-RADS categories, we explored the best potential cutoffs for pulmonary SUVmax against CO-RADS categories as the gold standard result to eliminate the possibility that the diagnosis of COVID-19 pneumonia exists. Results: On multimodal PET/CT imaging, CT signs classified as CO-RADS category 5 or 6 were found in 16 of 41 (39%) oncologic patients. SUVmax was higher in patients with categories 5 and 6 than in patients with category 4 (6.17 ± 0.82 vs. 3.78 ± 0.50, P = 0.04) or categories 2 and 3 (3.59 ± 0.41, P = 0.01). A specificity of 93.8% (95% CI, 71.7%-99.7%) and an accuracy of 92.9% were obtained when combining a CO-RADS score of 5 or 6 with an SUVmax of 2.45 in pulmonary infiltrates. Conclusion: In asymptomatic cancer patients, the metabolic activity in lung infiltrates is closely associated with several combined tomographic changes characteristic of COVID-19 pneumonia. Multimodal 18F-FDG PET/CT imaging could provide additional information during early diagnosis in selected predisposed patients during the pandemic. The prognostic implications of simultaneous radiologic and molecular findings in cancer patients and other subpopulations at high risk for COVID-19 pneumonia deserve further evaluation in prospective research.

Clinical relevance of incidental focal breast uptake on fluorine-18 fluorodeoxyglucose PET/computed tomography studies: an experience in a high-load center of Spain.

AIM: We aimed to determine the frequency and clinical significance of breast incidental uptake (BIU) detected through fluorine-18 fluorodeoxyglucose (18F-FDG) PET/computed tomography (CT) in a single, high-load center. PATIENTS AND METHODS: In this retrospective study, we analyzed a total of 13 763 PET/CT studies performed from January 2017 to January 2020. After excluding 3148 scans, the maximum standardized uptake value (SUVmax) and maximum diameter (cm) of each BIU were measured. Clinical management, ultrasound/mammography and pathology reports were analyzed. RESULTS: We found BIU in 27 scans of 26 patients (0.3% of the studies). Mean age was 62.2 years and 88.5% were women; 84.6% underwent PET/CT for oncological indications. Ultrasound/mammography was consequently performed in 23 patients (88.5%), and histological correlations were available for Breast Imaging Reporting and Data System categories 4 and 5. Finally, lesions were benign in 14 patients (60.9%; two of them with low/intermediate risk of malignancy) and malignant in nine patients (39.1%). The remaining three patients had no ultrasound/mammography reports. Mean SUVmax of benign and malignant lesions were 2.6 ± 1.4 and 5.8 ± 3.5, respectively (P = 0.002). Considering a SUVmax cut-off value of 4.0, the sensitivity and specificity for differentiating benign vs. malignant lesions were 67 and 93%, respectively. Benign lesions were smaller than malignant in CT (maximum diameter:1.3 ± 0.5 cm vs. 2.0 ± 1.0 cm, P = 0.02). CONCLUSION: Although BIU detected by 18F-FDG PET/CT is infrequently found, the risk of malignancy remains very high (39.1%). Both SUVmax and maximum diameter were greater in malignant than in benign lesions. An exhaustive study with ultrasound/mammography and selective histopathological correlation is mandatory after BIU findings, even in small lesions.

Assessment of extra-parenchymal lung involvement in asymptomatic cancer patients with COVID-19 pneumonia detected on 18F-FDG PET-CT studies.

BACKGROUND: Lung involvement in patients with coronavirus disease 2019 (COVID-19) undergoing PET-CT has been previously reported. However, FDG uptake outside lung parenchyma was poorly characterized in detail. We evaluated the extra-parenchymal lung involvement in asymptomatic cancer patients with COVID-19 pneumonia through 18F-FDG PET-CT. METHODS: A total of 1079 oncologic 18F-FDG PET-CT were performed between February 2 and May 18, 2020. Confirmed COVID-19 pneumonia was defined as characteristic ground-glass bilateral CT infiltrates and positive genetic/serologic tests. Nonmetastatic extra-parenchymal lung PET-CT findings were evaluated through qualitative (visual), quantitative (measurements on CT), and semiquantitative (maximum standardized uptake value: SUVmax on PET) interpretation. Clinical data, blood tests, and PET-CT results were compared between patients with and without COVID-19 pneumonia. RESULTS: A total of 23 18F-FDG PET-CT scans with pulmonary infiltrates suggestive of COVID-19 and available laboratory data were included: 14 positive (cases) and 9 negative (controls) for COVID-19 infection, representing a low prevalence of COVID-19 pneumonia (1.3%). Serum lactate dehydrogenase and D-dimers tended to be increased in COVID-19 cases. Extra-parenchymal lung findings were found in 42.9% of patients with COVID-19, most frequently as mediastinal and hilar nodes with 18F-FDG uptake (35.7%), followed by incidental pulmonary embolism in two patients (14.3%). In the control group, extra-pulmonary findings were observed in a single patient (11.1%) with 18F-FDG uptake located to mediastinal, hilar, and cervical nodes. Nasopharyngeal and hepatic SUVmax were similar in both groups. CONCLUSION: In cancer patients with asymptomatic COVID-19 pneumonia, 18F-FDG PET-CT findings are more frequently limited to thoracic structures, suggesting that an early and silent distant involvement is very rare. Pulmonary embolism is a frequent and potentially severe finding raising special concern. PET-CT can provide new pathogenic insights about this novel disease.

Not All Heart Uptakes on 99mTc-DPD Scintigraphy Are Amyloidosis: Chloroquine-Induced Cardiomyopathy.

ABSTRACT: This was the case of a 61-year-old woman with a medical history significant for hypertension and rheumatoid arthritis treated with chloroquine for the last 10 years. She was admitted to our hospital for heart failure symptoms. Echocardiography revealed severe concentric left ventricular hypertrophy. Serum and urine immunofixation electrophoresis and serum light chain assay were negative. No late gadolinium enhancement was observed on cardiovascular magnetic resonance. 99mTc-99mTc-DPD (3,3-diphosphono-1,2-propanodicarboxylic acid) scintigraphy showed myocardial uptake (Perugini score 2/3). Genetic testing excluded hereditary transthyretin cardiac amyloidosis. Endomyocardial biopsy analysis did not show findings suggestive of amyloidosis but consistent with chloroquine toxicity. Chloroquine-mediated cardiotoxicity is rare, and there are very few reports about bone scintigraphy imaging features.

Incidental and simultaneous finding of pulmonary thrombus and COVID-19 pneumonia in a cancer patient derived to 18F-FDG PET/CT. New pathophysiological insights from hybrid imaging.

Cancer patients require a careful clinical follow-up during the coronavirus disease 2019 (COVID-19) pandemic. Although hybrid fluorine-18 Fluorodeoxyglucose (18F-FDG) positron emission tomography-computed tomography (PET/CT) is not routinely used in the management of COVID-19 patients, it could play a complementary role of other laboratory and radiological data in selected cases. We describe an asymptomatic cancer patient derived to 18F-FDGPET/CT with simultaneous findings of COVID-19 pneumonia and pulmonary thrombus, discussing its possible mechanisms and prognostic implications.