Metabolic characterization of structural lung changes in patients with findings suggestive of incidental COVID-19 pneumonia on 18F-FDG PET/CT. Pathophysiological insights from multimodal images obtained during the pandemic.

PURPOSE: To evaluate the metabolic uptake of different tomographic signs observed in patients with incidental structural findings suggestive of COVID-19 pneumonia through 18F-FDG PET/CT. MATERIALS AND METHODS: We retrospectively analyzed 596 PET/CT studies performed from February 21, 2020 to April 17, 2020. After excluding 37 scans (non-18F-FDG PET tracers and brain studies), we analyzed the metabolic activity of several structural changes integrated in the CO-RADS score using the SUVmax of multimodal studies with 18F-FDG. RESULTS: Forty-three patients with 18F-FDG PET/CT findings suggestive of COVID-19 pneumonia were included (mean age: 68±12.3 years, 22 male). SUVmax values were higher in patients with CO-RADS categories 5-6 than in those with lower CO-RADS categories (6.1±3.0 vs. 3.6±2.1, p=0.004). In patients with CO-RADS 5-6, ground-glass opacities, bilaterality and consolidations exhibited higher SUVmax values (p-values of 0.01, 0.02 and 0.01, respectively). Patchy distribution and crazy paving pattern were also associated with higher SUVmax (p-values of 0.002 and 0.01). After multivariate analysis, SUVmax was significantly associated with a positive structural diagnosis of COVID-19 pneumonia (odds ratio=0.63, 95% confidence interval=0.41-0.90; p=0.02). The ROC curve of the regression model intended to confirm or rule out the structural diagnosis of COVID-19 pneumonia showed an AUC of 0.77 (standard error=0.072, p=0.003). CONCLUSIONS: In those patients referred for standard oncologic and non-oncologic indications (43/559; 7.7%) during pandemic, imaging with 18F-FDG PET/CT is a useful tool during incidental detection of COVID-19 pneumonia. Several CT findings characteristic of COVID-19 pneumonia, specifically those included in diagnostic CO-RADS scores (5-6), were associated with higher SUVmax values.

[Iatrogenic lung microembolism detected by 18FDG PET/CT]. / Microembolia pulmonar iatrogénica detectada mediante 18F-FDG PET/TC.

We present the cases of two oncology patients: a male with Hodgkin's disease after completion of chemotherapy, and a woman recently diagnosed of melanoma, who underwent positron emission tomography/computed tomography (PET/CT) with 18F-FDG for therapeutic monitoring and initial staging, respectively. In both cases, hypermetabolic foci of 18F-FDG in lung parenchyma were found, without morphologic abnormalities in CT. These findings would have been consistent with lung pathology in the absence of any anatomic correlation. Combined PET/CT interpretation was of lung microembolisms probably originated at the injection site.

[Follow-up of children and young adults with differentiated thyroid cancer treated with radioiodine]. / Seguimiento de niños y jóvenes adultos con cáncer diferenciado de tiroides (CDT) tratados con radioyodo.

This is a retrospective study carried out in a group of 30 patients with differentiated thyroid cancer (age at diagnosis equal to or less than twenty years old). The aim of the study is to evaluate outcome after 131I therapy. Patients were classified into three groups on the basis of initial surgery, pathology and scintigraphic results: group I (thyroid extent), group II (locoregional extent), and group III (distant metastatic disease). Clinical parameters, 131I scans, serum thyroglobulin determinations and 131I therapeutic administered doses were evaluated in the follow-up. Some other complementary techniques such as chest X-ray and pulmonary function tests are also described. Scintigraphic absence of thyroid tissue has been observed in 83% of the cases; high thyroglobulin level is still detectable in 34% of the patients as a single evidence of disease, and 21% remain without any abnormal clinical, scintigraphic or analytical findings. Total doses administered have increased in groups I, II and III respectively, and have also been inversely proportional to the extension of lymph node surgery. At present, all the patients are alive and in good general condition. According to the results obtained, we conclude that children and young adults with DTC should undergo periodical 131I therapeutic doses in case of positive scans (once total thyroidectomy has been realized, with or without lymph node resection depending on the extension of disease). In our experience, the use of radioiodine is effective and safe in the follow-up of children and youngs with DTC.