Lung perfusion assessment in children with long-COVID: A pilot study.

BACKGROUND: There is increasing evidence that chronic endotheliopathy can play a role in patients with Post-Covid Condition (PCC, or Long Covid) by affecting peripheral vascularization. This pilot study aimed at assessing lung perfusion in children with Long-COVID with 99m Tc-MAA SPECT/CT. MATERIALS AND METHODS: lung 99m Tc-MAA SPECT/CT was performed in children with Long-COVID and a pathological cardiopulmonary exercise testing (CPET). Intravenous injections were performed on patients in the supine position immediately before the planar scan according to the EANM guidelines for lung scintigraphy in children, followed by lung SPECT/CT acquisition. Reconstructed studies were visually analyzed. RESULTS: Clinical and biochemical data were collected during acute infection and follow-up in 14 children (6 females, mean age: 12.6 years) fulfilling Long-COVID diagnostic criteria and complaining of chronic fatigue and postexertional malaise after mild efforts, documented by CPET. Imaging results were compared with clinical scenarios during acute infection and follow-up. Six out of 14 (42.8%) children showed perfusion defects on 99m Tc-MAA SPECT/CT scan, without morphological alterations on coregistered CT. CONCLUSIONS: This pilot investigation confirmed previous data suggesting that a small subgroup of children can develop lung perfusion defects after severe acute respiratory syndrome coronavirus 2 infection. Larger cohort studies are needed to confirm these preliminary results, providing also a better understanding of which children may deserve this test and how to manage those with lung perfusion defects.

Utility of Lung Perfusion SPECT/CT in Detection of Pulmonary Thromboembolic Disease: Outcome Analysis.

PURPOSE: To evaluate the clinical outcome of Q-SPECT/CT in pulmonary thromboembolic disease. METHODS: From Jan 2020 to Jan 2021, 30 consecutive patients (M:F = 8:22; median age = 52 year (21-89)) suspected of having acute pulmonary embolism (PE) or chronic thromboembolic pulmonary hypertension (CTEPH) were referred for non-contrasted Q-SPECT/CT. All patients were COVID-19 PCR negative. MSKCC Q-SPECT/CT and/or PISAPED criteria were used to determine the presence of thromboembolic disease in Q-SPECT/CT. Final diagnosis was made based on composite reference standards that included at least 2-month clinical cardiorespiratory assessment and follow-up imaging. RESULTS: Q-SPECT/CT was positive in 19 patients: indeterminate in 1 and 10 were negative. Three false positive cases were observed during follow-up. Of the remaining 16 true positives, all patients' cardiorespiratory symptom were improved or stabilised after treatment with anticoagulants. The overall sensitivity, specificity, PPV, NPV and accuracy of Q-SPECT/CT were 100% (95% CI, 79.41-100%), 78.57% (95% CI, 49.20-95.34%), 84.21% (95% CI, 66.41-93.57%), 100% and 90.00% (95% CI, 73.47-97.89%) respectively. CONCLUSIONS: In the current COVID-19 pandemic, Q-SPECT/CT can be an alternative modality to detect pulmonary thromboembolic disease. Normal Q-SPECT/CT excludes pulmonary thromboembolic disease with high degree of certainty. However, false positive has been observed.

Identification and Follow-up of COVID-19 Related Matching Ventilation and Perfusion Defects on Functional Imaging Using VQ SPECT/CT.

Purpose: Available clinical data have revealed that coronavirus disease 2019 (COVID-19) is associated with a risk of pulmonary microthrombosis and small airway disease. These patients present with varying degrees of perfusion abnormalities. The purpose of this study was to evaluate the use of a ventilation/perfusion single-photon emission computed tomography/computed tomography (VQ SPECT/CT) in the detection and follow-up of persistent lung perfusion abnormalities that were suspected to be due to pulmonary microthrombosis, small airway disease, or both. Methods: A retrospective study was conducted at the department of nuclear medicine of Universitas Academic Hospital in Bloemfontein, South Africa. We reviewed the studies of 78 non-hospitalized patients with COVID-19 infection referred to our department from July 2020 to June 2021 for a perfusion only SPECT/CT study or a VQ SPECT/CT study. Pulmonary embolism was suspected in all 78 cases. Results: Seventy-eight patients were studied. The median (interquartile range) age was 45 (41-58) years, and the majority (n = 69; 88.5%) were females. Twenty-two (28.2%) of these patients had matching VQ defects with mosaic attenuation on CT. All nine of the patients who had follow-up studies had these abnormalities persistently, even after 1 year. Conclusion: We confirm that the VQ scan is a safe and effective tool to identify and follow-up recovered COVID-19 patients with persistent ventilation and perfusion abnormalities suspicious of small airway disease and pulmonary microthrombosis.

Lung perfusion assessed by SPECT/CT after a minimum of three months anticoagulation therapy in patients with SARS-CoV-2-associated acute pulmonary embolism: a retrospective observational study.

BACKGROUND: Anticoagulant treatment is recommended for at least three months after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-related acute pulmonary embolism (PE), but the persistent pulmonary clot burden after that time is unknown. METHODS: Lung perfusion was assessed by ventilation-perfusion (V/Q) SPECT/CT in 20 consecutive patients with SARS-CoV-2-associated acute PE after a minimum of three months anticoagulation therapy in a retrospective observational study. RESULTS: Remaining perfusion defects after a median treatment period of six months were observed in only two patients. All patients (13 men, seven women, mean age 55.6 ± 14.5 years) were on non-vitamin K direct oral anticoagulants (DOACs). No recurrent venous thromboembolism or anticoagulant-related bleeding complications were observed. Among patients with partial clinical recovery, high-risk PE and persistent pulmonary infiltrates were significantly more frequent (p < 0.001, respectively). INTERPRETATION: Temporary DOAC treatment seems to be safe and efficacious for resolving pulmonary clot burden in SARS-CoV-2-associated acute PE. Partial clinical recovery is more likely caused by prolonged SARS-CoV-2-related parenchymal lung damage rather than by persistent pulmonary perfusion defects.

Extensive Nonsegmental Pulmonary Perfusion Defects on SPECT/CT as an Early Sign of COVID-19 Infection.

We describe a hospitalized patient with confirmed coronavirus disease 2019 in whom the initial chest computed tomography (CT) was negative, while subsequent perfusion single-photon emission computed tomography/computed tomography imaging revealed extensive nonsegmental perfusion defects in addition to newly developing parenchymal densities. Possible reasons for these findings and their relationship to the multisystem severe acute respiratory syndrome coronavirus 2 infection are discussed in this article.

Covid-19 manifestation on Tl-201 myocardial perfusion SPECT/CT

A 67 years old woman was referred to nuclear medicine center for myocardial perfusion imaging (MPI) for assessment of ischemic heart dieses (IHD).She had a history of atypical chest pain and dyspnea since about 10 days before admission. The MPI SPECT/CT was performed by stress/redistribution Tl-201 protocol. MPI was interpreted as relatively good coronary flow with no appreciable stress induced ischemia. SPECT-CT images revealed multifocal, bilateral and peripheral ground-glass opacities in lungs with subtle background uptake of Tl-201. Considering Covid-19 outbreak, the first diagnosis based on chest CT was Covid-19. This case emphasizing importance of attention to non-cardiac findings in patients undergoing myocardial perfusion imaging, especially review of lung window images in SPECT/CT protocols in the era of covid-19.

Unusual perfusion patterns on perfusion-only SPECT/CT scans in COVID-19 patients.

PURPOSE: We aimed at examining both the incidence and extent of different lung perfusion abnormalities as well as the relationship between them on Tc-99m macroaggregated albumin (MAA) perfusion-only SPECT/CT scans in COVID-19 patients. METHODS: Ninety-one patients (71.4 ± 13.9 years; range: 29-98 years, median age: 74 years; 45 female and 46 male) with confirmed SARS-CoV-2 virus infection were included in this retrospective study. After performing perfusion-only Tc-99m MAA SPECT/CT scans, visual, semi-quantitative assessment of the subsequent perfusion abnormalities was carried out: mismatch lesions (MM; activity defects on SPECT images identical to apparently healthy parenchyma on CT images), matched lesions (MA; activity defects with corresponding parenchymal lesions on CT scans), and reverse mismatch lesions (RM; parenchymal lesions with preserved or increased tracer uptake). Lesion-based and patient-based analysis were performed to evaluate the extent, severity, and incidence of each perfusion abnormality. Statistical tests were applied to investigate the association between the experienced perfusion impairments. RESULTS: Moderately severe parenchymal lesions were detected in 87 (95.6%) patients. Although, 50 (54.95%) patients were depicted to have MM lesions, the whole patient cohort was mildly affected by this abnormality. MA lesions of average moderate severity were seen in most of the patients (89.01%). In 65 (71.43%) patients RM lesions were found with mild severity on average. Positive association was detected between total CT score and total RM score and between total CT score and total MA score. Significantly higher total CT scores were experienced in the subgroup, where RM lesions were present. CONCLUSIONS: Heterogeneous perfusion abnormalities were found in most of COVID-19 patients: parenchymal lesions with normal, decreased or increased perfusion and perfusion defects in healthy lung areas. These phenomena may be explained by the failure of the hypoxic pulmonary vasoconstriction mechanism and presence of pulmonary thrombosis and embolism.

99mTc-Vitamin C SPECT/CT imaging in SARS-CoV-2 associated pneumonia.

We present the first 99mTc-Vitamin C single-photon emission computed tomography/computed tomography (SPECT/CT) images obtained in patients with SARS-CoV-2 (COVID-19) infection. The CT portion of SPECT/CT images showed mostly peripheral patchy and ground-glass opacities in both lungs, which are consistent with a diagnosis of SARS-CoV-2-associated pneumonia in both patients. 99mTc-Vitamin C SPECT images showed increased tracer uptake corresponding to abnormal lung findings seen on CT in patient 1 who was newly diagnosed and treatment naïve. However, no abnormal uptake corresponding to lung CT findings was seen in patient 2 who received anti-SARS-CoV-2 treatment.

[Long-term follow-up study of post-COVID-19 patients].

AIM: To evaluate dynamic changes in the lungs, hemostasis system, immune system in different terms after coronavirus pneumonia. MATERIALS AND METHODS: Ventilation-perfusion single-photon emission computed tomography/computed tomography (CT), functional methods of lung investigation, evaluation of hemostasis system, immune status and specific humoral immune response were performed and evaluated in different terms after coronavirus pneumonia. A total of 71 patients were examined according to this protocol. We examined patients with the lesion volume not less than 50% according to chest CT. All patients were divided into 2 groups depending on the distance from the acute stage of coronavirus pneumonia. Group 1 included patients who were examined early (3060 days after hospital discharge), group 2 included patients who were examined later (61180 days after hospital discharge). RESULTS: We obtained gradual regression of pathologically-modified tissue from 67.3% during the inpatient phase to 30.9% during the early period and to 19.7% during the late period of examination, according to CT scan of the chest organs. The same tendency was demonstrated by diffusion capacity of the lungs. Perfusion scintigraphy data showed a decrease in perfusion deficit from 26.012.8% during the early period of examination to 19.46.2% during the late period of examination. On the contrary, ventilatory scintigraphy demonstrates the increase of isotope passage time through the alveolar-capillary membrane over time (from 48.231.3 minutes in the early period to 83.637.2 minutes in the late period). An increase in D-dimer was detected in 24% of patients in the early group. The levels of inflammatory markers, indices of immune status, and specific humoral immune response did not differ in the two described groups. CONCLUSION: The results demonstrate gradual regression of pathological changes caused by coronavirus infection.

Comparison of BMIPP-SPECT/CT to 18FDG-PET/CT for Imaging Brown or Browning Fat in a Preclinical Model.

Obesity is a leading cause of preventable death and morbidity. To elucidate the mechanisms connecting metabolically active brown adipose tissue (BAT) and metabolic health may provide insights into methods of treatment for obesity-related conditions. 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18FDG-PET/CT) is traditionally used to image human BAT activity. However, the primary energy source of BAT is derived from intracellular fatty acids and not glucose. Beta-methyl-p-iodophenylpentadecanoic acid (BMIPP) is a fatty acid analogue amenable to in vivo imaging by single photon emission computed tomography/CT (SPECT/CT) when radiolabeled with iodine isotopes. In this study, we compare the use of 18FDG-PET/CT and 125I-BMIPP-SPECT/CT for fat imaging to ascertain whether BMIPP is a more robust candidate for the non-invasive evaluation of metabolically active adipose depots. Interscapular BAT, inguinal white adipose tissue (iWAT), and gonadal white adipose tissue (gWAT) uptake of 18FDG and 125I-BMIPP was quantified in mice following treatment with the BAT-stimulating drug CL-316,243 or saline vehicle control. After CL-316,243 treatment, uptake of both radiotracers increased in BAT and iWAT. The standard uptake value (SUVmean) for 18FDG and 125I-BMIPP significantly correlated in these depots, although uptake of 125I-BMIPP in BAT and iWAT more closely mimicked the fold-change in metabolic rate as measured by an extracellular flux analyzer. Herein, we find that imaging BAT with the radioiodinated fatty acid analogue BMIPP yields more physiologically relevant data than 18FDG-PET/CT, and its conventional use may be a pivotal tool for evaluating BAT in both mice and humans.

Imaging Pulmonary Blood Vessels and Ventilation-Perfusion Mismatch in COVID-19.

COVID-19 hypoxemic patients although sharing a same etiology (SARS-CoV-2 infection) present themselves quite differently from one another. Patients also respond differently to prescribed medicine and to prone Vs supine bed positions. A severe pulmonary ventilation-perfusion mismatch usually triggers moderate to severe COVID-19 cases. Imaging can aid the physician in assessing severity of COVID-19. Although useful for their portability X-ray and ultrasound serving on the frontline to evaluate lung parenchymal abnormalities are unable to provide information about pulmonary vasculature and blood flow redistribution which is a consequence of hypoxemia in COVID-19. Advanced imaging modalities such as computed tomography, single-photon emission tomography, and electrical impedance tomography use a sharp algorithm visualizing pulmonary ventilation-perfusion mismatch in the abnormal and in the apparently normal parenchyma. Imaging helps to access the severity of infection, lung performance, ventilation-perfusion mismatch, and informs strategies for medical treatment. This review summarizes the capacity of these imaging modalities to assess ventilation-perfusion mismatch in COVID-19. Despite having limitations, these modalities provide vital information on blood volume distribution, pulmonary embolism, pulmonary vasculature and are useful to assess severity of lung disease and effectiveness of treatment in COVID-19 patients.

Investigation of perfusion defects by Q-SPECT/CT in patients with mild-to-moderate course of COVID-19 and low clinical probability for pulmonary embolism.

OBJECTIVE: Pulmonary embolism is a severe source of mortality and morbidity in patients with severe and critical coronavirus disease 2019. It is not yet clear whether the tendency to thrombosis is increased in the mild-to-moderate course of COVID-19. Our research aims to show the clinical benefit of Q-SPECT/CT in diagnosing PD in outpatients treated with mild-to-moderate course of COVID-19 and to determine the frequency of perfusion defects in these patients having relatively lower risk. METHODS: All patients who underwent Q-SPECT/CT with suspicion of embolism were examined retrospectively. Only patients with low clinical probability and mild-to-moderate course of COVID-19 for PE were included in the study. The patients were evaluated comparatively as those with and without perfusion defects. Patients were divided into laboratory suspicion, clinical suspicion, or clinical and laboratory suspicion. RESULTS: In outpatients with mild-to-moderate COVID-19 with low clinical probability for PE, PD without CT abnormality was detected with a rate of 36.6% with Q-SPECT/CT performed for complaints of high D-dimer and/or dyspnea. None of the patients had PD at more proximal level than the segment level. PD with no concomitant CT abnormality was observed with a rate of 56.5% in patients with both clinical and laboratory suspicion. For D-dimer = 0.5 mg/dL cut-off sensitivity is 85%, for D-dimer = 1.5 mg/dL cut-off specificity 81%. CONCLUSION: Thrombosis tendency is also present in outpatients with mild-to-moderate COVID-19, and these patients should also be offered anticoagulant prophylaxis during the COVID-19 period.

Renal Infarcts-A Perplexing Case in the Middle of the COVID-19 Pandemic.

Renal infarction is a rare finding in children. Associations between SARS-CoV-2 infections and thromboembolic events including renal infarcts have been described in adults. Although a similar association in children has not yet been described with this pandemic, the pediatric literature is still evolving with the recognition of new manifestations including the post-infectious Multisystem Inflammatory Syndrome in Children (MIS-C). We report the rare event of multiple renal infarcts in a 6-year-old boy manifesting several features of MIS-C 9 weeks following a self-limiting febrile illness characteristic of COVID-19. An underlying Factor V Leiden mutation was identified in this child but felt to be insufficient on its own to explain his clinical presentation. As SARS-CoV-2 testing was delayed, the failure to identify viral RNA or antibodies may not exclude the virus' potential role in precipitating the infarct in this host. Given that renal infarcts have been described in adult patients with COVID-19, reporting this perplexing case where SARS-CoV-2 may have played a role, may help identify this potential complication.

Clinical utility of perfusion (Q)-single-photon emission computed tomography (SPECT)/CT for diagnosing pulmonary embolus (PE) in COVID-19 patients with a moderate to high pre-test probability of PE.

PURPOSE: We reviewed the clinical utility of perfusion (Q)-single-photon emission computed tomography (SPECT)/CT for diagnosing pulmonary embolus (PE) in patients hospitalized with severe acute respiratory syndrome coronavirus 2 (SARS-CoV2). METHODS: Following the World Health Organization's declaration of a global pandemic, our department policy recommended Q-only SPECT/CT for all patients undergoing nuclear medicine evaluation for suspected PE to reduce the risk of aerosolization of respiratory droplets. We performed a retrospective review of sequential patients admitted with COVID-19 imaged with Q-SPECT/CT between March 17, 2020, and June 30, 2020, at Memorial Sloan Kettering Cancer Center. We recorded patient demographics, clinical symptoms, Wells score (to stratify patients according to pre-test probability for PE prior to Q-SPECT/CT), and noted ancillary imaging findings on CT. RESULTS: Of the 33 patients imaged with Q-SPECT/CT, 6 patients (3 men, 3 women) had a laboratory confirmed diagnosis of COVID-19 (mean age, 55, ± 11.4 years, range 33-68). All patients had a current diagnosis of malignancy and had a moderate or high pre-test probability for PE (mean Wells score 2.8, range 2-4). Q-SPECT/CT was positive in 4/6 (67%) of patients. Distribution of pulmonary emboli was bilateral and segmental in 75% of patients. Ancillary acute findings on SPECT/CT included bilateral parenchymal ground glass opacities (n = 5), pleural effusions (n = 2), and pneumomediastinum (n = 1). CONCLUSION: Q-SPECT/CT has clinical utility for diagnosing PE in patients with COVID-19 where there is a contraindication for iodinated contrast media and a moderate or high pre-test probability for PE.