Incidental extra-cardiac findings on 13N-ammonia myocardial perfusion PET/CT

Characterisation and management of expected and unexpected urgent findings from positron emission tomography with 18F-fluorodeoxyglucose integrated with computed tomography in cardiovascular disease

BACKGROUND

Cardiac 18F-fluorodeoxyglucose (FDG)-PET-CT plays an important role in the assessment of cardiovascular diseases. Effective management of urgent scan findings facilitates optimal patient care.

METHODS

We characterised the management of urgent, expected and unexpected findings in patients referred for cardiac [18F]fluorodeoxyglucose integrated with computed tomography (FDG-PET-CT) at the Royal Brompton Hospital (United Kingdom). Urgent findings are escalated by the reporting physicians/radiologists raising RadAlert notifications to the referring clinician. We characterised the indications and time to management (TTM) between the RadAlert and the resulting management. As controls, we characterised the TTM of 33 urgent findings identified before the RadAlert system was implemented.

RESULTS

Of the 1497 consecutive FDG-PET-CT scans screened (April 2021 to February 2023), 93 RadAlerts were suitable for analysis (TTM 7 days [interquartile range: 2-14]). Expected urgent findings included active cardiac sarcoidosis (56%; TTM 8 days [5-18]), heart transplant rejection (12%; 6 ± 4 days), infective endocarditis (9%; 2 days [1-12]), cardiac device infections (5%; 1 day [0-2]), acute myocarditis (2%; 5 and 14 days) and epicardial mass (1%; 1 day). TTM did not differ significantly between indications (P = 0.06). RadAlert cases had significantly shorter TTM than controls without RadAlert, P = 0.001. After the RadAlerts, 81% of patients had clinical reviews, and 55% had escalation of medical/surgical therapies. Unexpected findings (total N = 45; median TTM 6 days [1-10]) included malignancies (N = 3), infections (N = 2), pneumothorax (N = 1), benign diagnosis (N = 30), unclear diagnosis (N = 5) and 4 findings disappeared on repeat imaging.

CONCLUSIONS

Cardiac FDG-PET-CT identifies expected and unexpected findings in a range of cardiovascular diseases. Serious, unexpected findings are rare and can be effectively escalated by the RadAlert system.

Incidental Tongue Cancer Detected With Total-Body 13 N-NH 3 PET/CT

ABSTRACT

A 68-year-old man with chest tightness underwent cardiac blood perfusion imaging on total-body 13 N-NH 3 PET/CT. Incidentally, mildly increased 13 N-NH 3 activity was observed in the left side of the body of the tongue. Pathological diagnosis proved to be mucosal squamous cell carcinoma.

Extracardiac findings with increased perfusion during clinical O-15-H2O PET/CT myocardial perfusion imaging: A case series

BACKGROUND

Coincidental extracardiac findings with increased perfusion were reported during myocardial perfusion imaging (MPI) with various retention radiotracers. Clinical parametric O-15-H2O PET MPI yielding quantitative measures of myocardial blood flow (MBF) was recently implemented at our facility. We aim to explore whether similar extracardiac findings are observed using O-15-H2O.

METHODS AND RESULTS

All patients (2963) were scanned with O-15-H2O PET MPI according to international guidelines and extracardiac findings were collected. In contrast to parametric O-15-H2O MBF images, extracardiac perfusion was assessed using summed images. Biopsy histopathology and other imaging modalities served as reference standards. Various malignant lesions with increased perfusion were detected, including lymphomas, large-celled neuroendocrine tumour, breast, and lung cancer plus metastases from colonic and renal cell carcinomas. Furthermore, inflammatory and hyperplastic benign conditions with increased perfusion were observed: rib fractures, gynecomastia, atelectasis, sarcoidosis, pneumonia, chronic lung inflammation and fibrosis, benign lung nodule, chronic diffuse lung infiltrates, pleural plaques and COVID-19 infiltrates.

CONCLUSIONS

Malignant and benign extracardiac coincidental findings with increased perfusion are readily visible and frequently seen on O-15-H2O PET MPI. We recommend evaluating the summed O-15-H2O PET images in addition to the low-dose CT attenuation images.

Detection efficacy of analog [18F]FDG PET/CT, digital [18F]FDG, and [13N]NH3 PET/CT: a prospective, comparative study of patients with lung adenocarcinoma featuring ground glass nodules

OBJECTIVES

This prospective study compared the detection efficacy of analog ¹⁸F-fluoro-2-deoxyglucose (¹⁸F-FDG) positron emission tomography (PET)/computed tomography (CT) (aF PET/CT), digital [¹⁸F]FDG PET/CT (dF PET/CT), and digital ¹³N-ammonia (¹³N-NH₃) PET/CT (dN PET/CT) for patients with lung adenocarcinoma featuring ground glass nodules (GGNs).

METHODS

Eighty-seven patients with lung adenocarcinoma featuring GGNs who underwent dF and dN PET/CT were enrolled. Based on the GGN component, diameter, and solid-part size, 87 corresponding patients examined using aF PET/CT were included, with age, sex, and lesion characteristics closely matched. Images were visually evaluated, and the tumor to background ratio (TBR) was used for semi-quantitative analysis.

RESULTS

Ultimately, 40 and 47 patients with pure GGNs (pGGNs) and mixed GGNs (mGGNs), respectively, were included. dF PET/CT revealed more positive lesions and higher tracer uptake in GGNs than did aF PET/CT (53/87 vs. 26/87, p < 0.05; TBR: 3.08 ± 4.85 vs. 1.42 ± 0.93, p < 0.05), especially in mGGNs (44/47 vs. 26/47, p < 0.05; TBR: 4.48 ± 6.17 vs. 1.78 ± 1.16, p < 0.05). However, dN PET/CT detected more positive lesions than did dF PET/CT (71/87 vs. 53/87, p < 0.05), especially in pGGNs (24/40 vs. 9/40, p < 0.05).

CONCLUSIONS

dF PET/CT provides superior detection efficacy over aF PET/CT for patients with lung adenocarcinoma featuring GGNs, particularly mGGNs. dN PET/CT revealed superior detection efficacy over dF PET/CT, particularly in pGGNs. aF, dF, and dN PET/CT are valuable non-invasive examinations for lung cancer featuring GGNs, with dN PET/CT offering the best detection performance.

KEY POINTS

• Digital PET/CT provides superior detection efficacy over analog PET/CT in patients with lung adenocarcinoma featuring GGNs. • dN PET/CT can offer more help in the early detection of malignant GGN.

Incidental Findings on 18F-Fluorocholine PET/CT for Parathyroid Imaging

Introduction   ¹⁸ F-choline positron emission tomography/computed tomography (PET/CT) is an upcoming imaging technique for the localization of hyperfunctioning parathyroid glands. However, ¹⁸ F-choline is a nonspecific tracer that also accumulates in malignancies, inflammatory lesions, and several other benign abnormalities. The aim of this study was to determine the occurrence and relevance of incidental findings on ¹⁸ F-choline PET/CT for parathyroid localization.

Materials and Methods   ¹⁸ F-choline PET/CTs performed in our center for parathyroid localization from 2015 to 2019 were reviewed. Abnormal uptake of ¹⁸ F-choline, with or without anatomical substrate on the co-registered low-dose CT and also incidental findings on CT without increased ¹⁸ F-choline uptake were recorded. Each finding was correlated with follow-up data from the electronic medical records.

Results  A total of 388 ¹⁸ F-choline PET/CTs were reviewed, with 247 incidental findings detected in 226 patients (58%): 82 ¹⁸ F-choline positive findings with corresponding pathology on CT, 16 without CT substrate, and 149 ¹⁸ F-choline negative abnormalities on CT. Malignant lesions were detected in 10/388 patients (2.6%). Of all 98 detected ¹⁸ F-choline positive lesions, 15 were malignant (15.3%), concerning 4 metastases and 11 primary malignancies: breast carcinoma ( n  = 7), lung carcinoma ( n  = 2), thyroid carcinoma ( n  = 1), and skin melanoma ( n  = 1).

Conclusion  Clinically relevant incidental findings were observed in a substantial number of patients. In 15.3% of the incidental ¹⁸ F-choline positive findings, the lesions were malignant. These data contribute to better knowledge of ¹⁸ F-choline distribution, enhance interpretation of ¹⁸ F-choline PET/CT, and guide follow-up of incidental findings. Attention should especially be paid to breast lesions in this particular patient group with hyperparathyroidism in which women are typically over-represented.

Prevalence and variability in reporting of clinically actionable incidental findings on attenuation-correction CT scans in a veteran population

BACKGROUND

Myocardial perfusion imaging (MPI) often employs attenuation-correction computed tomography (CTAC) to reduce attenuation artifacts and improve specificity. While there is no specific guideline on how they should be reported, incidental noncardiac findings identified on these scans may be clinically significant. The prevalence of these findings in veterans is not currently known. In addition, variability in reporting these findings may depend on the interpreting physician's specialty.

METHODS

To guide future decision-making, CTACs in veterans referred for MPI were prospectively evaluated in a quality-control project for a set of prespecified actionable incidental findings by cardiologists and a radiologist.

RESULTS

On the 771 scans performed over eight months, 285 incidental noncardiac findings were identified by the interpreting cardiologists and 378 were identified by the interpreting radiologist. Pulmonary nodules were the most common occurring in 20% of studies read by the radiologist. Interreader agreements between cardiologists and the radiologist were poor for pulmonary nodules ≥ 10 mm and hiatal hernias; fair for pulmonary nodules < 10 mm, extracardiac masses, and aortic aneurysms; and moderate for pleural plaques.

CONCLUSION

Incidental noncardiac findings on CTACs are common in our veteran population. Overall interobserver agreement in identifying these findings between cardiologists and radiologists is fair. Specific guidelines are needed on how CTACs should be read and reported.

Review of cardiovascular imaging in the Journal of Nuclear Cardiology 2017. Part 1 of 2: Positron emission tomography, computed tomography, and magnetic resonance

Several original articles and editorials have been published in the Journal of Nuclear Cardiology in 2017. It has become a tradition at the beginning of each year to summarize some of these key articles in 2 sister reviews. In this first part one, we will discuss some of the progress made in the field of heart failure (cardio-oncology, myocardial blood flow, viability, dyssynchrony, and risk stratification), inflammation, molecular and hybrid imaging using advancement in positron emission tomography, computed tomography, and magnetic resonance imaging.