Positron emission tomography in malignancies of the liver, pancreas and biliary tract - indications and potential pitfalls

Value of 18F-FDG PET/CT Combined with Lung HRCT in Diagnosis of Solitary Pulmonary Intravascular Metastasis

Background

Solitary pulmonary intravascular metastasis is a rare complication of malignant tumors, and accurate diagnosis can improve clinical decision-making, but diagnosing it effectively using conventional techniques is difficult.

Purpose

To explore the value of ¹⁸F-FDG PET/CT combined with lung high-resolution computed tomography (HRCT) in the diagnosis of solitary pulmonary intravascular metastasis.

Methods

¹⁸F-FDG PET/CT, lung HRCT, and follow-up data of 18,143 cancer patients were retrospectively analyzed to select patients with pulmonary vessel involvement besides the primary tumor only. The histopathological or imaging follow-up results were used as the diagnostic criteria for pulmonary intravascular metastasis.

Results

A total of 13 patients with 17 pulmonary intravascular metastases were found, of which 9 patients had a single lesion and 4 had double. The SUVmax was 1.1–5.4 (average, 2.4 ± 1.4), and the length of hypermetabolic metastasis was 5.1–24.1 mm (average, 10.7 ± 6.5 mm). All the intravascular metastases were located in the terminal pulmonary vessels. Strip or branched pulmonary vessels enlargement with increased metabolism was the main imaging manifestation (15/17, 88.2%), while the other 2 cases only showed strip metabolic enhancement without abnormalities in pulmonary vessels (2/17, 11.8%). Four pulmonary intravascular metastases were confirmed by pathology, and the other 13 cases were diagnosed by imaging follow-up.

Conclusion

¹⁸F-FDG PET/CT combined with lung HRCT is an effective technique for the diagnosis of solitary pulmonary intravascular metastasis. High-strip or branched FDG uptake in the distal pulmonary vessel accompanied by corresponding morphological changes in patients with malignant tumors can be used as a specific diagnostic indicator.

The Diagnostic Value of FDG PET/CT and Thin-Slice High-Resolution Chest CT in Pulmonary Intravascular Metastasis

OBJECTIVE. Pulmonary intravascular metastasis is a special type of pulmonary metastasis of malignancies; however, few relevant studies have been performed. This study aimed to determine the characteristics of pulmonary intravascular metastasis and improve understanding of the disease by retrospective analysis of FDG PET/CT and thin-layer high-resolution CT (HRCT) imaging of the chest in patients with tumors. MATERIALS AND METHODS. We identified all patients who underwent FDG PET/CT at two hospitals between January 2016 and February 2019 and conducted a comparative analysis of HRCT and PET/CT images. In total, 84 patients (38 women and 46 men) ranging in age from 35 to 82 years old (mean age, 54.7 ± 14.5 [SD] years) participated in the study. Patient characteristics were summarized, and diagnosis was confirmed by chest CT or PET/CT follow-up. RESULTS. A total of 260 pulmonary intravascular metastases were found, which were classified as type I (no significant abnormality, n = 5), type II (abrupt and uneven thickening of the pulmonary vessel, n = 118), type III (simultaneous invasion of adjacent pulmonary vessel, n = 121), and type IV (large strip-shaped high-density mass, n = 16). The majority were located in peripheral pulmonary vessels (94.2% [245/260]). FDG up-take was increased in 252 lesions, and the mean SUV_max was 4.6 ± 2.5. CONCLUSION. The combination of PET/CT and chest HRCT is an effective approach for detecting pulmonary intravascular metastasis. The linear pattern of FDG uptake, abnormal pulmonary blood vessel morphology, and location (below the lung segment) are specific indicators for the diagnosis of pulmonary intravascular metastasis and should be recognized by clinicians and radiologists.

Contrast-Enhanced Ultrasound in the Assessment of Patients with Indeterminate Abdominal Findings at Positron Emission Tomography Imaging

Widespread use of fluorodeoxyglucose-positron emission tomography (PET) in cancer imaging may result in a number of indeterminate and false-positive findings. We investigated the role of contrast-enhanced ultrasound (CEUS) as a second-level option after inconclusive PET. We reviewed CEUS images acquired over 4 y, selecting the examinations performed specifically to better assess an unclear PET image. Final diagnosis was confirmed by biopsy, surgery, further imaging or follow-up. Seventy CEUS examinations were performed after a PET scan (44 PET examinations, 19 PET-computer tomography [CT] examinations and 7 PET-CECT examinations). The target organ was the liver in 54 cases, spleen in 12, gallbladder in 2 and pancreas and kidney in one each. In 6 of 70 cases, CEUS was performed because of a negative PET (no uptake) despite an abnormal finding on the CT images of the PET-CT study; CEUS allowed a correct diagnosis in all of these. In 20 of 70 cases, the PET findings were categorized as indeterminate and non-specific (non-specific fluorodeoxyglucose uptake in PET report with no standardized uptake value given); CEUS reached a correct diagnosis in 19 of the 20 cases with one false negative. In 34 of 70 cases, PET was indeterminate, but specific (fluorodeoxyglucose uptake with a standardized uptake value provided); CEUS reached a correct diagnosis in 30 of these 34 cases. In 10 of 70 cases, PET was categorized as determinate but to be investigated because of discrepancy with clinical or imaging findings; CEUS a definitive diagnosis in 9 of 10 cases. CEUS proved to be effective option in the assessment of cancer patients with indeterminate PET findings.