The rim sign: FDG-PET/CT pattern of pulmonary infarction

Post-RFA Pulmonary Vein Stenosis Mimicking Lymphangitic Carcinomatosis in a Patient With History of Liposarcoma

ABSTRACT

A 58-year-old man with resected liposarcoma exhibited persistent irregular interlobular septal thickening of lung on CT concerning lymphangitic metastasis. FDG PET/CT was positive in these foci. There was a narrowing of the pulmonary veins, which had not been seen on the imaging conducted prior to radiofrequency ablation therapy for atrial fibrillation. Lung perfusion scanning demonstrated more extensive hypoperfusion. This case highlights the diagnostic pitfalls of interstitial thickening of the lung in cancer patients. Meticulous history review and nuclear imaging helped distinguish the postablation pulmonary venous stenosis from metastatic spread to the lung interstitium.

Augmentation of literature review of COVID-19 radiology

We suggest an augmentation of the excellent comprehensive review article titled “Comprehensive literature review on the radiographic findings, imaging modalities, and the role of radiology in the coronavirus disease 2019 (COVID-19) pandemic” under the following categories: (1) “Inclusion of additional radiological features, related to pulmonary infarcts and to COVID-19 pneumonia”; (2) “Amplified discussion of cardiovascular COVID-19 manifestations and the role of cardiac magnetic resonance imaging in monitoring and prognosis”; (3) “Imaging findings related to fluorodeoxyglucose positron emission tomography, optical, thermal and other imaging modalities/devices, including ‘intelligent edge’ and other remote monitoring devices”; (4) “Artificial intelligence in COVID-19 imaging”; (5) “Additional annotations to the radiological images in the manuscript to illustrate the additional signs discussed”; and (6) “A minor correction to a passage on pulmonary destruction”.

A Frequently Missed Pulmonary Infarction: Clinical and 18F-FDG PET/CT Manifestation of Hilar Tumor-Induced Pulmonary Infarction

PURPOSE

This study aimed to summarize the clinical and 18F-FDG PET/CT manifestations of hilar tumor-induced pulmonary infarction.

METHODS

A retrospective analysis was performed on patients with hilar masses who underwent FDG PET/CT scans between July 2015 and January 2021 and had complete clinical data. Pulmonary infarction was confirmed by concurrent chest CT and imaging follow-up or pathology.

RESULTS

A total of 58 patients (mean age, 56 [SD, 13] years; 44 males) with 122 infarcts were included in the study. Hilar masses were mostly associated with small cell lung cancer (64%). The most common clinical manifestations were cough (64%) and hemoptysis (36%). Most patients (62%) had multiple pulmonary infarcts. The CT findings of pulmonary infarcts included the "Hampton hump" (48%) and patchy consolidation (52%). The density of infarcts included "bubbly consolidation" (61%) and "homogenous consolidation" (39%). The metabolic activity of 95 infarcts (78%) was higher than lung parenchyma, with the SUVmax of 3.3 (SD, 1.1). The metabolic patterns on PET/CT were "rim sign," "mismatch between PET and CT," and "no metabolism." Pulmonary vein involvement was found in 25 patients (43%), pleural effusion in 22 patients (38%), and the pleural curvilinear sign in 8 patients (14%).

CONCLUSIONS

The clinical manifestations of hilar tumor-induced pulmonary infarction are not specific, and 18F-FDG PET/CT could be an effective diagnostic tool.

Prediction of Pulmonary Embolism Following Resection of Pulmonary Infarction: A Case Series

Purpose: Pulmonary nodules suspected to be cancerous are rarely diagnosed as pulmonary infarction (PI). This study examined the clinical, radiological, and laboratory data in cases diagnosed with PI to determine their potential utility as preoperative diagnostic markers. We also assessed factors affecting the postoperative course.

Methods: A total of 603 cases of peripheral pulmonary nodules undiagnosed preoperatively were resected at Hokkaido University Hospital from 2012 to 2019. Of these, we reviewed cases with a postoperative diagnosis of PI. We investigated clinical symptoms, preoperative laboratory data, radiological characteristics, and postoperative complications.

Results: Four patients (0.7%) were diagnosed with PI. All patients had a smoking history. One patient received systemic steroid administration, and none had predisposing factors for thrombosis. One case showed chronologically increased nodule size. Three cases showed weak uptake of ¹⁸F-fluorodeoxyglucose. One patient with preoperative high D-dimer levels developed a massive pulmonary embolism (PE) in the postoperative chronic phase and was treated with anticoagulants.

Conclusions: Preoperative diagnosis of PI is difficult, and we could not exclude lung cancer. However, if a patient diagnosed with PI has a high D-dimer level, we recommend postoperative physical examination for deep venous thrombosis. Prophylactic anticoagulation therapy should be considered to avoid fatal PE.

FDG PET/CT Suggesting Pulmonary Artery Involvement of Takayasu Arteritis

Pulmonary artery involvement can occur in about half of the patients suffering Takayasu arteritis. Increased FDG activity in the aorta and its main branches in patients with Takayasu arteritis on PET/CT had been well-reported. However, the FDG PET/CT appearance of pulmonary artery involvement in Takayasu arteritis is less known. We present FDG PET/CT findings in a 37-year-old patient with known Takayasu arteritis. The images showed rim-like FDG activity in opacities in the left lung, which was later proven due to narrowed left main pulmonary artery.

Acute saddle pulmonary embolism on 18F-FDG PET/CT: diagnosis by functional imaging

18F-labelled fluoro-2-deoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) is used extensively in the setting of cancer staging and in assessing cancer treatment response. Oncology patients have a sevenfold risk of developing pulmonary embolism (PE) due to underlying activation of the haemostatic system and anti-cancer therapy inducing a hypercoagulable state. The diagnosis of PE on 18F-FDG PET/CT is challenging, particularly in the absence of intravenous contrast. The case of a female patient undergoing treatment for advanced diffuse large B-cell lymphoma is presented. The ancillary signs of PE are illustrated on consecutive non-contrast-enhanced 18F-FDG PET/CT scans. The signs include the "rim sign" relating to regions of pulmonary infarction and abnormal cardiac uptake indicating right heart strain. The diagnosis was confirmed on CT pulmonary angiography which demonstrated extensive PE, including a saddle embolus.

Pulmonary Artery Sarcoma Detected on 18F-FDG PET/CT With Unusual Findings

A 32-year-old woman, who presented with "sharp pain" in the right chest for more than 1 month and worsening dyspnea and fever for 10 days, was initially thought to have a pulmonary embolism. Cardiac ultrasound showed an ill-defined echogenic mass within the pulmonary trunk. F-FDG PET/CT was performed for further evaluation. PET/CT showed an intense hypermetabolism in the main, bilateral proximal, and the right main pulmonary arteries, suggesting the presence of a malignant lesion. Biopsy confirmed the lesion as a primary pulmonary artery sarcoma.

Predictors of Pulmonary Infarction

In the setting of acute pulmonary embolism (PE), pulmonary infarction is deemed to occur primarily in individuals with compromised cardiac function.The current study was undertaken to establish the prevalence of pulmonary infarction in patients with acute PE, and the relationship between infarction and: age, body height, body mass index (BMI), smoking habits, clot burden, and comorbidities.The authors studied prospectively 335 patients with acute PE diagnosed by computed tomographic angiography (CT) in 18 hospitals throughout central Italy. The diagnosis of pulmonary infarction on CT was based on Hampton and Castleman's criteria (cushion-like or hemispherical consolidation lying along the visceral pleura). Multivariable logistic regression was used to model the relationship between covariates and the probability of pulmonary infarction.The prevalence of pulmonary infarction was 31%. Patients with infarction were significantly younger and with significantly lower prevalence of cardiovascular disease than those without (P < 0.001). The frequency of infarction increased linearly with increasing height, and decreased with increasing BMI. In logistic regression, the covariates significantly associated with the probability of infarction were age, body height, BMI, and current smoking. The risk of infarction grew with age, peaked at approximately age 40, and decreased afterwards. Increasing body height and current smoking were significant amplifiers of the risk of infarction, whereas increasing BMI appeared to confer some protection.Our data indicate that pulmonary infarction occurs in nearly one-third of the patients with acute PE. Those with infarction are often young and otherwise healthy. Increasing body height and active smoking are predisposing risk factors.

The incidence of pulmonary embolism and associated FDG-PET findings in IV contrast-enhanced PET/CT

RATIONALE AND OBJECTIVES

Most fluorine-18 fluorodeoxyglucose (FDG)-positron emission tomography with computed tomography (PET/CT) studies are performed on cancer patients. These patients are at increased risk of pulmonary embolism (PE). In this retrospective review, we determined the rate of PE, and the prevalence of associated FDG-PET findings on intravenous (IV) contrast-enhanced PET/CT.

MATERIALS AND METHODS

We identified all PET/CT studies performed at our institution with a reported finding of PE between January 2005 and October 2012. The medical record was reviewed for symptoms, which were identified after the diagnosis of PE, and whether the patients received treatment. The prevalence of associated FDG-PET findings was determined.

RESULTS

A total of 65 total cases of PE (of 182,72 total PET/CT examinations) were identified of which 59 were previously unknown. This gives an incidental PE (IPE) rate of 0.32%. Of the patients where sufficient clinical information was available, 34 of 36 (94%) were treated either with therapeutic anticoagulation or inferior vena cava filter, and 30 of 36 (83%) were asymptomatic in retrospect. Of the patients with IPE, we found nine (15.2%) with associated focal pulmonary artery hypermetabolism, three (5.1%) with hypermetabolic pulmonary infarction, and one with increased isolated right ventricular FDG uptake (1.7%). One case of chronic PE demonstrated a focal hypometabolic filling defect in a pulmonary artery on PET.

CONCLUSIONS

We found IPE in 0.32% of PET/CT scans. Focal pulmonary artery hypermetabolism or hypometabolism, and hypermetabolic pulmonary artery infarction with the "rim sign" were uncommonly associated with PE. These findings could raise the possibility of IPE in non-IV contrast-enhanced PET/CT studies.