Spectrum of Benign Articular and Periarticular Findings at FDG PET/CT

Incidental FAPI Localization in Benign Bone Lesions in a Case of Carcinoma Stomach

ABSTRACT

Recently developed radiolabeled FAPI (fibroblast-activation protein inhibitors) have attracted researcher's attention in diagnosing various tumors because of its high specificity and better tumor-to-background ratio. Increasing use of 68 Ga-FAPI PET/CT has resulted in reporting of incidental benign findings as well. We hereby present a case of suspected carcinoma stomach showing increased uptake in primary tumor in stomach as well as incidental uptake in benign subchondral cysts in bilateral shoulder joints and right hip joint on 68 Ga-FAPI PET CT scan.

Value of subspecialist second opinion reads of 18 F-FDG PET-CT examinations for patients with breast cancer

OBJECTIVES

Determine if subspecialist second opinion review alters reporting of malignancy on 18 F-FDG PET/CT for patients with breast cancer.

METHODS

This IRB-approved retrospective study compared 248 s opinion reads of 18 F-FDG PET/CT exams performed for patients with breast cancer against the original outside institution reports. Subspecialist reviews documented if malignant findings on the outside report were believed to be malignant and noted additional malignant findings not described on the outside report. Reference standard for malignancy or benignity was determined by pathology or follow-up imaging.

RESULTS

Of 248 cases, 27 (11%) had discrepancies in the presence or absence of extra-axillary nodal or distant metastases. Of these 27, 14 (52%) had biopsy or imaging follow-up as a reference standard for malignancy/benignity. In cases with reference standard proof, the subspecialist second opinion review was correct in 13/14 (93%) of cases. This included eleven cases that the original report called malignant, but the subspecialist review called benign and subsequently proven to be benign; as well as two metastases called on subspecialist review, but not on the original report, and subsequently biopsy proven to be metastases. In one case, the second opinion read called a suspicious lesion that was biopsy proven to be benign.

CONCLUSION

Subspecialist review improves the accuracy of diagnosis for the presence or absence of malignancy on FDG PET/CT examinations in patients with breast cancer. This demonstrates the value of performing second opinion reads of 18 F-FDG PET/CT studies in patients with breast cancer, particularly by subspecialist second opinion review reducing false positive reads.

Checkpoint Inhibitor Immune-Related Adverse Events: A Multimodality Pictorial Review

Cancer immunotherapies are drugs that modulate the body's own immune system as an anticancer strategy. Checkpoint inhibitor immunotherapies interfere with cell surface binding proteins that function to promote self-recognition and tolerance, ultimately leading to upregulation of the immune response. Given the striking success of these agents in early trials in melanoma and lung cancer, they have now been studied in many types of cancer and have become a pillar of anticancer therapy for many tumor types. However, abundant upregulation results in a new class of side effects, known as immune-related adverse events (IRAEs). It is critical for the practicing radiologist to be able to recognize these events to best contribute to care for patients on checkpoint inhibitor immunotherapy. Here, we provide a comprehensive system-based review of immune-related adverse events and associated imaging findings. Further, we detail the best imaging modalities for each as well as describe problem solving modalities. Given that IRAEs can be subclinical before becoming clinically apparent, radiologists may be the first provider to recognize them, providing an opportunity for early treatment. Awareness of IRAEs and how to best image them will prepare radiologists to make a meaningful contribution to patient care as part of the clinical team.

[18F]FDG-PET Evaluation of Spinal Pathology in Patients in Oncology: Pearls and Pitfalls for the Neuroradiologist

[¹⁸F]FDG-PET is a widely used technique for specific evaluation of disease and treatment response in oncology. However, the principles behind [¹⁸F]FDG-PET imaging allow a wide-ranging array of benign and malignant pathologies to be identified on both initial and routine surveillance imaging. This is important for clinicians and radiologists, alike, in that effective and accurate evaluation of malignancy and metastatic disease, specifically involving the spine and central nervous system, is crucial. In this article, we review the normal and posttherapy appearance of the spine on [¹⁸F]FDG-PET, the various types and patterns of metastatic disease that involve the spine and spinal cord, and, finally, important spinal pathologies that may mimic malignancy on [¹⁸F]FDG-PET.

Potential Applications of PET/CT/MR Imaging in Inflammatory Diseases: Part I: Musculoskeletal and Gastrointestinal Systems

During the past decades, the role of fludeoxyglucose (FDG)-PET and hybrid PET/computed tomography (CT) has been established clinically in the diagnostic workup of a multitude of infectious and inflammatory disorders. In recent years, the fusion of MR imaging to PET has also been increasingly explored, and this may be especially useful in musculoskeletal and gastrointestinal inflammatory diseases due to exceptional soft tissue contrast and reduced radiation dose. This article outlines the current potential for hybrid molecular imaging in the musculoskeletal system and the gastrointestinal tract with special focus on the potential for fused PET/CT/MR imaging.

Significance of incidental intra-articular and peri-articular FDG avid foci on PET/CT

BACKGROUND

Positron emission tomography/computed tomography (PET/CT) is a useful imaging adjunct in patients with sarcoma. Intra-articular and peri-articular 18F-fluoro-2-deoxy-D-glucose (FDG) avid lesions are often discovered incidentally.

PURPOSE

To describe the etiology, appearance, and standardized uptake values (SUV) of incidentally detected FDG avid intra-articular and peri-articular foci in patients with sarcoma.

MATERIAL AND METHODS

The institutional sarcoma database between November 2011 and November 2016 was retrospectively reviewed. Patients were included if a PET/CT scan was performed and an FDG avid intra-articular or peri-articular focus was found that was distinct from the primary sarcoma.

RESULTS

The majority of FDG avid foci represented benign, non-physiologic conditions such as osteoarthritis, enthesopathy, bursitis, and post-surgical changes. Six patients each had radiographic features consistent with tenosynovial giant cell tumor (TSGCT) and metastatic disease, respectively. Lower SUV, bilateral findings, and the absence of metastatic disease elsewhere were associated with benign etiologies. There was a statistically significant difference between the mean SUV measured in patients with TSGCT and those with benign, non-physiologic conditions ( P < 0.001). The difference between the benign, non-physiologic cohort and the cohort with widespread metastatic disease did not reach statistical significance ( P = 0.07).

CONCLUSIONS

In patients with soft-tissue or osseous sarcomas, isolated FDG avid intra-articular or peri-articular foci without additional metastatic lesions likely represent benign processes. Isolated intra-articular or peri-articular foci with significantly elevated SUV measurements were favored to represent TSGCT in this series.

A confounding rib variation: bilateral symmetric aberrant posterior rib articulations and bridgings

INTRODUCTION

Although mild bone angulation with osseous enlargement often suggests fractures with callus formation, in some cases the diagnosis is synchondrosis.

CASE REPORT

We present a rare variation of the chest wall in a 15-year-old male with a history of lymphoma. Bilateral multi-level posterior rib enlargements revealing mild ¹⁸F-fluorodeoxyglucose uptake were detected via positron-emission tomography/computed tomography. The variations were identified as healing fractures, although the more accurate diagnosis was determined to be multi-level posterior rib synchondroses with consecutive bridgings. Although variant bone anatomies are commonly seen in radiological practice, such multiple symmetrical posterior rib synchondroses associated with consecutive bridgings and articulations have not been clearly demonstrated before.

CONCLUSION

Awareness of such a rare combination of a well-known variation is crucial for radiologists to exclude malignancies, possibility of fracture and suspicion of child abuse.