Lung Perfusion Scintigraphy Early After COVID-19: A Single-Center Retrospective Study.

The incidence of thromboembolic complications in coronavirus disease 2019 (COVID-19) infection is well recognized. The present study retrospectively evaluated the type and prevalence of lung perfusion defects in early-post-COVID-19 patients with hypoxia and was aimed to identify the risk factors for mismatched perfusion defects. Methods: We analyzed SPECT/CT images of 54 early-post-COVID-19 patients (44 men and 10 women). Logistic regression analysis was used to examine the risk. Results: The mean age of the study population was 55.4 y (range, 34-76 y). All received prophylactic anticoagulation from the day of hospitalization to the date of perfusion scanning. The median interval between COVID-19-positive reports and lung perfusion scanning was 22 d. Lung perfusion defects (of any type) were observed in most (87%). Twenty-three subjects (42.6%) had mismatched perfusion defects. Mismatched perfusion defects were segmental in 14 subjects (25.9%) and subsegmental in 11 (20.4%). Higher age was a risk factor for mismatched perfusion defects (odds ratio, 1.06; 95% CI, 0.99-1.13; P = 0.06). Subjects with a serum D-dimer level of at least 2,500 ng/mL on the day before the scan were not at higher risk for having mismatched perfusion defects (odds ratio, 1.14; 95% CI, 0.34-3.9; P = 0.83). Conclusion: Despite prophylactic anticoagulation, mismatched perfusion defects suggestive of pulmonary thromboembolism were observed. Serum D-dimer level in patients early after COVID-19 is a poor predictor of mismatched perfusion defects. Confirmed evidence of pulmonary embolism by imaging studies should support the decision to extend anticoagulant prophylaxis in post-COVID-19 patients.

Comparative evaluation of 18F-FDOPA, 13N-AMMONIA, 18F-FDG PET/CT and MRI in primary brain tumors - A pilot study.

AIM: To determine the diagnostic reliability of 18F-FDOPA, 13N-Ammonia and 18F-FDG PET/CT in primary brain tumors and comparison with magnetic resonance imaging (MRI). MATERIALS AND METHODS: A total of 23 patients, 8 preoperative and 15 postoperative, undergoing evaluation for primary brain tumors were included in this study. Of them, 9/15 were operated for high grade gliomas (7/9 astrocytomas and 2/9 oligodendrogliomas) and 6/15 for low grade gliomas (5/6 astrocytomas and 1/6 oligodendroglioma). After PET study, 2 of 8 preoperative cases were histopathologically proven to be of benign etiology. 3 low grade and 2 high grade postoperative cases were disease free on 6 months follow-up. Tracer uptake was quantified by standardized uptake values (SUV(max)) and the SUV max ratio of tumor to normal symmetrical area of contra lateral hemisphere (T/N). 18F-FDOPA uptake was also quantified by SUV(max) ratio of tumor to striatum (T/S). Conventional MR studies were done in all patients. RESULTS: Both high-grade and low-grade tumors were well visualized with 18F-FDOPA PET. Sensitivity of 18F-FDOPA PET was substantially higher (6/6 preoperative, 3/3 low grade postoperative, 7/7 high grade postoperative) than with 18F-FDG (3/6 preoperative, 1/3 low grade postoperative, 3/7 high grade postoperative) and 13N-Ammonia PET (2/6 preoperative, 1/3 low grade postoperative, 1/7 high grade postoperative). FDOPA was equally specific as FDG and Ammonia PET in operated cases but was falsely positive in two preoperative cases. Sensitivity of FDOPA (16/16) was more than MRI (13/16). CONCLUSION: 18F-FDG uptake correlates with tumor grade. Though 18F-FDOPA PET cannot distinguish between tumor grade, it is more reliable than 18F-FDG and 13N-Ammonia PET for evaluating brain tumors. 18F-FDOPA PET may prove to be superior to MRI in evaluating recurrence and residual tumor tissue. 13N-Ammonia PET did not show any encouraging results.

Extensive tumor thrombus in a case of carcinoma lung detected by F18-FDG-PET/CT.

Tumor thrombus is a rare complication of solid cancers, mainly seen in cases of renal cell carcinoma, wilm's tumor, testicular carcinoma, adrenal cortical carcinoma and hepatocellular carcinoma.[1] Tumor thrombus in inferior vena cava is a rare complication of primary carcinoma lung. It should be identified so as to rule out venous thromboembolism and avoiding unnecessary anticoagulant therapy. We describe a case where F18-Fluorodeoxyglucose (FDG) positron emission tomography - computed tomography (PET/CT) helped to identify extensive tumor thrombus.

Tc-99m MDP bone scintigraphy in a case of Touraine-Solente-Gole syndrome.

Pachydermoperiostosis is a form of primary hypertrophic osteoarthropathy, also known as Touraine-Solente-Gole syndrome. It is a rare disease. In this report, we present the case of a 29-year-old man with this rare disorder, having significant findings on Tc-99m methylene diphosphonate bone scan.

Comparative study of (18)F-DOPA, (13)N-Ammonia and F18-FDG PET/CT in primary brain tumors.

AIM: To determine the diagnostic reliability of (18)F-FDOPA, (13)N-Ammonia and F18-FDG PET/CT in primary brain tumors. We evaluated the amino acid and glucose metabolism of brain tumors by using PET with (18)F-FDOPA, (13)N-Ammonia and F18-FDG PET/CT. MATERIALS AND METHODS: Nine patients undergoing evaluation for brain tumors were studied. Tracer uptake was quantified by the use of standardized uptake values and the ratio of tumor uptake to normal identical area of contra lateral hemisphere (T/N). In addition, PET uptake with (18)F-FDOPA was quantified by use of ratio of tumor uptake to striatum uptake (T/S). The results were correlated with the patient's clinical profile. RESULTS: Both high-grade and low-grade tumors were well visualized with (18)F-FDOPA. The sensitivity for identifying tumors was substantially higher with (18)F-FDOPA PET than with F18-FDG and (13)N-Ammonia PET as determined by simple visual inspection. The sensitivity for identifying recurrence in low grade gliomas is higher with (13)N-Ammonia than with F18-FDG. CONCLUSION: (18)F-FDOPA PET is more reliable than F18-FDG and (13)N-Ammonia PET for evaluating brain tumors.