Multi-Modality Imaging in Vasculitis.

Systemic vasculitides are a rare and complex group of diseases that can affect multiple organ systems. Clinically, presentation may be vague and non-specific and as such, diagnosis and subsequent management are challenging. These entities are typically classified by the size of vessel involved, including large-vessel vasculitis (giant cell arteritis, Takayasu's arteritis, and clinically isolated aortitis), medium-vessel vasculitis (including polyarteritis nodosa and Kawasaki disease), and small-vessel vasculitis (granulomatosis with polyangiitis and eosinophilic granulomatosis with polyangiitis). There are also other systemic vasculitides that do not fit in to these categories, such as Behcet's disease, Cogan syndrome, and IgG4-related disease. Advances in medical imaging modalities have revolutionized the approach to diagnosis of these diseases. Specifically, color Doppler ultrasound, computed tomography and angiography, magnetic resonance imaging, positron emission tomography, or invasive catheterization as indicated have become fundamental in the work up of any patient with suspected systemic or localized vasculitis. This review presents the key diagnostic imaging modalities and their clinical utility in the evaluation of systemic vasculitis.

Chest Wall Keloids Depicted by 18 F-Piflufolastat PET/CT Imaging.

ABSTRACT: Keloids are pathological scars from exuberant fibroproliferative collagen response and excessive extracellular matrix production usually extending beyond the original wound margins. Although keloids are mostly of dermatological concern, they could be incidentally depicted on scintigraphic planar and PET/CT imaging and could mimic other types of skin diseases. The authors present a case of chest wall keloids documented on 18 F-piflufolastat PET/CT during the evaluation of prostate cancer recurrence.

Anatomic and Functional Imaging of Immunoglobulin G4-related Disease and Its Mimics.

Immunoglobulin G4 (IgG4)-related disease (IgG4-RD) is an immune-mediated fibrosclerosing disease with tumefactive lesions infiltrated by IgG4-positive plasma cells. Initially described as autoimmune pancreatitis, IgG4-RD is now recognized as a discrete entity and is found to affect virtually any organ in the body. Common extrapancreatic sites include the biliary tree, salivary glands, periorbital tissue, lungs, kidneys, lymph nodes, aorta, retroperitoneum, and thyroid gland. Diagnosis-which relies on histopathologic, serologic, and radiologic features-can be challenging with the disease underdiagnosed, as IgG4-RD often mimics malignancy, infectious processes, or other immune-mediated conditions. Patients may present with signs of compression of nearby structures due to mass effect or with organ failure when the disease is left untreated. The clinical course is complex, with single- or multiorgan involvement and metachronous or synchronous occurrence of lesions. IgG4-RD responds well to glucocorticoid therapy, disease-modifying antirheumatic drugs, and B-cell-depleting biologic agents; prompt diagnosis is important to avoid delay in treatment and unnecessary pharmacologic or surgical intervention. While imaging features may not be specific for IgG4-RD, functional whole-body imaging with fluorine 18-fluorodeoxyglucose PET/CT is a useful adjunct for localizing extrapancreatic sites for biopsy, monitoring therapeutic response, and demonstrating disease relapse. The authors describe the pancreatic and extrapancreatic sites of involvement in IgG4-RD, with imaging features and patterns to aid in distinguishing IgG4-RD from its mimics through a multimodality approach with emphasis on functional imaging evaluation. ©RSNA, 2023 Quiz questions in the supplemental material and the slide presentation from the RSNA Annual Meeting are available for this article.

PET/CT of delayed uterine leiomyoma metastasizing to lung and femur.

Benign metastasizing leiomyomas are benign disseminated extra-uterine tumors in patients with prior history of uterine leiomyomas and may occur years after hysterectomy. The lung is mostly affected, with less common occurrence in the brain, heart, spine, retroperitoneum, and bone. The authors present the role of 18F-FDG PET/CT in the metabolic staging and post-surgical monitoring of a patient with lung and femoral involvement.

18F-FDG PET/CT of Malignant Presacral Masses in Currarino Syndrome.

ABSTRACT: The Currarino syndrome is characterized by 3 main features: anorectal malformation, presacral lesion, and dysgenesis of the sacrum and coccyx. The presacral lesion is usually benign with a rare occurrence of malignant degeneration. The author presents 2 cases of Currarino syndrome with presacral mucinous adenocarcinoma and neuroendocrine tumor depicted by 18F FDG PET/CT.

11C-Choline PET/CT Depiction of Rectal Gastrointestinal Stromal Tumor.

ABSTRACT: 18F-FDG PET/CT is an established imaging modality for gastrointestinal stromal tumor evaluation and its posttherapeutic monitoring. 68Ga-PSMA has been recently reported with the incidental demonstration of this neoplasm on PET/CT. The author presents an uncommon case of this tumor detected by 11C-choline during the assessment of prostate cancer.

Histiocytosis and Neoplasms of Macrophage-Dendritic Cell Lineages: Multimodality Imaging with Emphasis on PET/CT.

Histiocytosis is a rare inflammatory process characterized by pathologic infiltration and accumulation of cells derived from the monocytic lineage in normal tissue. It encompasses more than 100 different subtypes of disorders that were recently classified into five main groups: (a) Langerhans-related histiocytosis, (b) Rosai-Dorfman histiocytosis, (c) cutaneous and mucocutaneous histiocytosis, (d) malignant histiocytosis, and (e) hemophagocytic lymphohistiocytosis and macrophage activation syndrome. Langerhans cell histiocytosis is the most common histiocytic disorder. Less common types include Erdheim-Chester disease, Rosai-Dorfman disease, adult and juvenile xanthogranuloma, necrobiotic xanthogranuloma, histiocytic sarcoma, interdigitating dendritic cell sarcoma, Langerhans cell sarcoma, and hemophagocytic lymphohistiocytosis. Although the pathogenesis of these disorders may be attributable to mutations in the oncogenic driver, recent discoveries have shown that inflammation and fibrosis secondary to mutated histiocytes, rather than a proliferative cell mechanism, result in manifestation of the disease. Diagnosis, which relies on a multidisciplinary approach, is challenging and often delayed because clinical findings are nonspecific and may mimic malignant processes at radiologic evaluation. Compared with conventional imaging, PET/CT allows detection of the increased metabolic activity in histiocytes. Diagnostic algorithms for histiocytic disorders should include functional imaging with fluorine 18 (18F) fluorodeoxyglucose (FDG) PET/CT, which provides a comprehensive whole-body evaluation of their potential involvement with multiple organ systems and allows monitoring of therapeutic response. The most recent revised classification, pathophysiologic and clinical manifestations, sites of involvement, and imaging features of histiocytosis are described in this review and a multimodality approach is used, with emphasis on 18F-FDG PET/CT evaluation. ©RSNA, 2021.

Parathyroid Scintigraphy with an Incidental Indirect Finding of Pancreatic Cancer.

Modifications of the biodistribution of 99mTc-sestamibi seen during myocardial perfusion and parathyroid imaging may be secondary to benign or malignant processes in visualized anatomic structures not related to the target organs of these imaging procedures. This article presents a case of pancreatic adenocarcinoma indirectly depicted on parathyroid scintigraphy.

Cavernosal Metastasis From Prostate Cancer on 18F-Fluciclovine PET/CT.

Uncommon penile metastasis from prostate cancer has been reported on PET/CT imaging with F-FDG, F-fluorocholine, C-choline, and Ga-PSMA. The author presents an additional case of F-fluciclovine PET/CT depiction of proximal and distal cavernosal metastases from prostate cancer with corresponding contrast-enhanced CT findings.

Molecular Imaging in Diagnosis of Tumor-induced Osteomalacia.

Tumor induced osteomalacia (TIO) is a rare paraneoplastic syndrome caused by overproduction of fibroblast growth factor 23 (FGF23) secreted by benign mesenchymal neoplasm. Due to its nonspecific clinical presentation or lack of awareness, the diagnosis of TIO is often significantly delayed resulting in patients' prolonged physical suffering or psychological distress. Successful detection or complete surgical resection of the causative tumor typically leads to rapid resolution of symptoms or reversal of biochemical imbalance. Nuclear medicine and molecular imaging have been playing a promising role as the first-line imaging modalities in the diagnosis and localization of occult FGF23 secreting mesenchymal tumor, especially with the emerging whole-body, head-to-toe Ga68-DOTATATE PET/CT technique. Combined focused diagnostic CT and/or MRI are imperative for accurate delineation of tumor and surgical guidance.

"Migratory" Pattern of Corticosteroid-Related Multifocal Bone Infarction on Bone Scintigraphy.

We present serial bone scintigraphy examinations in a 38-year-old woman who presented with posterior left rib pain in the setting of adrenal insufficiency secondary to pituitary damage as a result of radiation treatment for orbital sarcoma.

99mTc-Sulfur Colloid Bone Marrow Scintigraphy in Diagnosis of Diffuse Pulmonary Extramedullary Hematopoiesis Secondary to Myelofibrosis.

Our objective was to define the role of combined 99mTc-sulfur colloid bone marrow (SC BM) scintigraphy, SPECT or SPECT/CT, and chest CT in diagnosing diffuse pulmonary extramedullary hematopoiesis (PEMH) in patients with myelofibrosis. Methods: We retrospectively reviewed 99mTc-SC BM scintigraphy scans performed at our institution for the diagnosis of diffuse PEMH, as well as accompanying chest CT and SPECT/CT imaging findings. Relevant clinical information, including respiratory manifestations, pulmonary hypertension, and subjective response to whole-lung radiation therapy, was also summarized. Results: Twenty-two myelofibrosis patients with 27 99mTc-SC BM scintigraphy scans were diagnosed with diffuse PEMH. In 21 patients (95%) with accompanying chest CT and SPECT/CT scans, the most common CT findings were ground-glass opacity, interstitial infiltration, and pleural effusion. Of 20 patients (91%) who underwent 2-dimensional echocardiography studies, 12 (55%) were diagnosed with pulmonary hypertension. All 12 patients exhibited the aforementioned nonspecific CT imaging findings, with 8 (66%) of them presenting with respiratory symptoms, including dyspnea, shortness of breath, and cough. In the remaining 8 patients, without pulmonary hypertension, half had similar respiratory symptoms. Fourteen patients (64%) of this cohort received whole-lung radiation therapy, of whom 7 (50%) experienced symptom relief after therapy. Conclusion: Nonspecific respiratory symptoms should raise concern about pulmonary hypertension and diffuse PEMH in patients with advanced-stage myelofibrosis. Combined 99mTc-SC BM scintigraphy and SPECT/CT is a promising noninvasive imaging tool to diagnose this rare clinical entity.Key Words: hematology; respiratory; SPECT/CT; pulmonary hematopoiesis; Tc-99m sulfur colloid scintigraphy; myelofibrosis.