131 I Uptake in a Left Cerebral Infarct on Posttherapy Whole-Body Scan.

ABSTRACT: A 75-year-old woman with papillary thyroid carcinoma who underwent 131 I radioiodine treatment was incidentally found to have an established left cerebral infarct demonstrating 131 I uptake on posttherapy whole-body scan. False-positive iodine accumulation can occur in benign processes and other malignancies, necessitating awareness among nuclear medicine physicians to avoid misdiagnosing metastatic disease. SPECT/CT can be utilized to enhance diagnostic accuracy when needed.

Lymphoma Masquerading as Lung Cancer.

ABSTRACT: Lymphoma typically manifests as lymphadenopathy, with or without solid organ involvement. Lymphomatous masses tend to respect anatomical structures, encasing rather than invading them. Tumor thrombus formation is a rare presentation in lymphoma that has been previously described in the liver and kidneys. We report an unusual presentation of B-cell lymphoma with imaging findings suggestive of metastatic lung cancer with tumor thrombus in the pulmonary vein and left atrium.

Clinical utility of PET/MRI in multiple myeloma.

Introduction: This study aimed to evaluate the clinical utility of positron emission tomography/magnetic resonance imaging (PET/MRI), especially in comparison with PET/computed tomography (CT), which has been widely used in clinical practice in multiple myeloma. Method: F-18 fluorodeoxyglucose PET/MRI and PET/ CT studies were done at baseline and when at least a partial response to treatment was achieved. These were done for newly-diagnosed myeloma patients who have not had more than 1 cycle of anti-myeloma treatment, or for relapsed and/or refractory myeloma patients before the start of next line of therapy. Results: PET/MRI correlated significantly with PET/CT, in terms of number of lesions detected, standardised uptake value (SUVmean and SUVmax, both at baseline and post-treatment. PET/MRI and PET/CT correlated with survival at baseline, but not post-treatment. Conclusion: In this study, PET/MRI was more sensitive in detecting early disease and disease resolution post-treatment, compared with PET/CT. However, PET/MRI was less sensitive in detecting lesions in the ribs, clavicle and skull.

18F-FDG PET/CT Manifestations of IgG4-related Disease.

Immunoglobulin G4-related disease (IgG4-RD) was not recognised as a systemic condition until 2003, when extra pancreatic manifestations were identified in patients with autoimmune pancreatitis. Since then, IgG4-RD has been described to involve virtually every organ system. It is highly responsive to immunosuppressants but can have detrimental effects if left untreated. Early recognition of the disease is, therefore, critical. The diagnosis of IgG4-RD is frequently challenging owing to its non-specific clinical manifestations, indolent nature and broad differential diagnoses. Although histopathological examination remains the cornerstone of diagnosis, imaging plays an important role in establishing extent of disease and identifying areas suitable for biopsy. 18F-Fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) has been demonstrated to be useful in assessing organ involvement, guiding biopsy and monitoring disease response. The 18F-FDG PET/CT scan is highly sensitive and able to evaluate multiorgan involvement in a single examination, a key advantage over conventional imaging modalities. A potential pitfall is its low specificity. As such, detailed knowledge of the imaging findings in IgG4-related disease is required to avoid misdiagnosis. This pictorial review aims to depict the diverse spectrum of imaging findings of IgG4-RD and the key imaging features to distinguish it from other important differential diagnoses.

Atypical Response Patterns in Renal Cell Carcinoma Treated with Immune Checkpoint Inhibitors-Navigating the Radiologic Potpourri.

BACKGROUND: Atypical response patterns have been a topic of increasing relevance since the advent of immune checkpoint inhibitors (ICIs), challenging the traditional RECIST (Response Evaluation Criteria in Solid Tumors) method of tumor response assessment. Newer immune-related response criteria can allow for the evolution of radiologic pseudoprogression, but still fail to capture the full range of atypical response patterns encountered in clinical reporting. METHODS: We did a detailed lesion-by-lesion analysis of the serial imaging of 46 renal cell carcinoma (RCC) patients treated with ICIs with the aim of capturing the full range of radiologic behaviour. RESULTS: Atypical response patterns observed included pseudoprogression (n = 15; 32.6%), serial pseudoprogression (n = 4; 8.7%), dissociated response (n = 22; 47.8%), abscopal response (n = 9; 19.6%), late response (n = 5; 10.9%), and durable response after cessation of immunotherapy (n = 2; 4.3%). Twenty-four of 46 patients (52.2%) had at least one atypical response pattern and 18 patients (39.1%) had multiple atypical response patterns. CONCLUSIONS: There is a high incidence of atypical response patterns in RCC patients receiving ICIs and the study contributes to the growing literature on the abscopal effect. The recognition of these interesting and overlapping radiologic patterns challenges the oncologist to tweak treatment options such that the clinical benefits of ICIs are potentially maximized.

"Hot Cord" Sign on 18F-FDG PET/CT in a Patient With Acute Myelitis Due to Neuromyelitis Optica Spectrum Disorder.

A 44-year-old woman presented with prolonged low-grade fever, bilateral upper limb weakness, and hyperesthesia. MRI showed hyperintense T2 signal and enhancement of the cervicothoracic spinal cord. F-FDG PET/CT was requested to investigate pyrexia of unknown origin. It demonstrated diffusely increased FDG uptake along the entire spinal cord, suggestive of extensive acute myelitis. Initial blood work was positive for antinuclear antibodies and anti-Ro/SSA antibodies. Cerebrospinal fluid analysis revealed lymphocytosis and detected the presence of neuromyelitis optica aquaporin-4-immunoglobulin G antibodies, fulfilling the criteria for diagnosis of neuromyelitis optica spectrum disorder.

Current Status and Growth of Nuclear Theranostics in Singapore.

The concept of theranostics, where individual patient-level biological information is used to choose the optimal therapy for that individual, has become more popular in the modern era of 'personalised' medicine. With the growth of theranostics, nuclear medicine as a specialty is uniquely poised to grow along with the ever-increasing number of concepts combining imaging and therapy. This special report summarises the status and growth of Theranostic Nuclear Medicine in Singapore. We will cover our experience with the use of radioiodine, radioiodinated metaiodobenzylguanidine, peptide receptor radionuclide therapy, prostate specific membrane antigen radioligand therapy, radium-223 and yttrium-90 selective internal radiation therapy. We also include a section on our radiopharmacy laboratory, crucial to our implementation of theranostic principles. Radionuclide theranostics has seen tremendous growth and we hope to be able to grow alongside to continue to serve the patients in Singapore and in the region.