Nuclear Imaging in Sarcoidosis

Systemic and Neurosarcoidosis With Rare Involvement of the Extremities' Peripheral Nerves

ABSTRACT

We present a case of sarcoidosis with a rare presentation of involvement of peripheral nerves of the lower limbs and subcutaneous nodules detected on 18 F-FDG PET/CT. The patient also had involvement of the spinal nerves and dura, histologically proven to be sarcoidosis. There were other manifestations of systemic sarcoidosis like metabolically active cervical and mediastinal lymphadenopathy. This case highlights the role of 18 F-FDG PET/CT in evaluating the uncommon sites of sarcoid involvement. Although many cases of sarcoid involvement of central nervous system have been reported, peripheral nerves involvement in the extremities was not found on a literature search.

Imaging Plays a Key Role in the Diagnosis and Control of the Treatment of Bone Sarcoidosis

Sarcoidosis is a multisystem granulomatous disease of unknown origin. The most frequent localizations are thoracic lymph nodes and/or parenchymal lung disease, nevertheless any other organ may be involved. Musculoskeletal sarcoidosis, previously considered a rare manifestation of the disease, is presently recognized with increasing frequency, due to the development of modern imaging modalities. The classical X-ray sign of bone sarcoidosis is the image of lace in the phalanges of the hands. Most other locations present with atypical radiological images. Therefore, they may mimic metastatic neoplastic disease, especially when they are the first sign of sarcoidosis not previously recognized. On such occasions, none of the imaging methods will give the correct diagnosis, histopathological verification, monitoring of lesions or clinical data in a patient with confirmed sarcoidosis are indicated. The article summarizes the current status of knowledge concerning the recognition and therapy of bone sarcoidosis. In addition, an illustrative case of patient with bone and bone marrow sarcoidosis is presented.

FDG PET/CT Imaging of Sarcoidosis

Sarcoidosis is a multisystemic granulomatous disease of unknown etiology. The diagnostic can be made by histological identification of non-caseous granuloma or by a combination of clinical criteria. Active inflammatory granuloma can lead to fibrotic damage. Although 50% of cases resolve spontaneously, systemic treatments are often necessary to decrease symptoms and avoid permanent organ dysfunction, notably in cardiac sarcoidosis. The course of the disease can be punctuated by exacerbations and relapses and the prognostic depends mainly on affected sites and patient management. FDG-PET/CT along with newer FDG-PET/MR have emerged as key imaging modalities in sarcoidosis, namely for certain diagnostic purposes, staging and biopsy guiding. By identifying with a high sensitivity inflammatory active granuloma, FDG hybrid imaging is a main prognostic tool and therapeutic ally in sarcoidosis. This review aims to highlight the actual critical roles of hybrid PET imaging in sarcoidosis and display a brief perspective for the future which appears to include other radiotracers and artificial intelligence applications.

Severe hypercalcemia caused by repeated mineral oil injections: a case report

Hypercalcemia is a frequent condition in clinical practice and when the most frequent causes are excluded, etiological diagnosis can be challenging. A rare cause of PTH-independent hypercalcemia is described in the present case report. A male adult with a history of androgenic-anabolic steroids abuse, and injection of mineral oil and oily veterinary compound containing vitamins A, D and E into muscles for local hypertrophy presented with hypercalcemia, nephrocalcinosis, and end-stage renal disease. On physical examination, the presence of calcified subcutaneous nodules and calcification of musculature previously infused with oily substances drew attention. Laboratory tests confirmed hypercalcemia of 12.62 mg/L, low levels of PTH (10 pg/mL), hyperphosphatemia (6.0 mg/dL), 25(OH)D of 23.3 ng/mL, and elevated 1,25(OH)2D (138 pg/mL). Imaging exams showed diffuse calcification of muscle tissue, subcutaneous tissue, and organs such as the heart, lung, and kidneys. The patient was diagnosed with PTH-independent hypercalcemia secondary to foreign body reaction in areas of oil injection. The patient underwent treatment with hydrocortisone for 10 days, single dose zoledronic acid and hemodialysis. He evolved with serum calcium levels of 10.4 mg/dL and phosphorus of 7.1 mg/dL. In addition, sertraline and quetiapine were prescribed to control body dysmorphic disorder. The medical community should become aware of new causes of hypercalcemia as secondary to oil injection since this should become increasingly frequent due to the regularity with which such procedures have been performed.

Utility of PET/Computed Tomography in Infection and Inflammation Imaging

The role of nuclear medicine for noninvasive assessment of infection and inflammation is well established. The role of nuclear medicine is limited to initial diagnosis, recurrence, and response assessment of infections and inflammations such as tuberculosis, sarcoidosis, vasculitis, osteomyelitis, immunoglobulin G4-related diseases, and coronavirus disease 2019, as the specificity is affected by false positivity due to physiologic fluorodeoxyglucose uptake in specific organ and nonspecific uptake in postoperative cases. PET with fludeoxyglucose F 18/CT is a well-established modality for diagnosis of fever of unknown origin helping in optimized management of the patient.

A Comprehensive Review of Sarcoidosis Diagnosis and Monitoring for the Pulmonologist

Sarcoidosis is a systemic granulomatous disease with heterogenous clinical manifestations. Here we review the diagnosis of sarcoidosis and propose a clinically feasible diagnostic work-up and monitoring protocol. As sarcoidosis is a systemic disease, a multidisciplinary approach is recommended for best outcomes. However, since the lungs are frequently involved, the pulmonologist is often the referral physician for diagnosis and management. When sarcoidosis is suspected, diagnosis needs to be confirmed and organ involvement/impairment assessed. This process is also required to establish whether the patient is likely to benefit from treatment, as many cases of sarcoidosis are self-limited and remit spontaneously. Whether or not treatment is started, effective regular follow-up is necessary to monitor changes in the disease, including extension, progression, remissions, flare-ups, and complications.

Emerging Preclinical and Clinical Applications of Theranostics for Nononcological Disorders

Studies in nuclear medicine have shed light on molecular imaging and therapeutic approaches for oncological and nononcological conditions. Using the same radiopharmaceuticals for diagnosis and therapeutics of malignancies, the theranostics approach, has improved clinical management of patients. Theranostic approaches for nononcological conditions are recognized as emerging topics of research. This review focuses on preclinical and clinical studies of nononcological disorders that include theranostic strategies. Theranostic approaches are demonstrated as possible in the clinical management of infections and inflammations. There is an emerging need for randomized trials to specify the factors affecting validity and efficacy of theranostic approaches in nononcological diseases.

Fluorodeoxyglucose PET/CT of Arthritis in Rheumatic Diseases: A Pictorial Review

Rheumatic diseases are various painful conditions that affect joints, bones, cartilage, tendons, ligaments, and muscles. Arthritis is a typical condition of rheumatic disease. Although rheumatoid arthritis is a representative rheumatic disease, various diseases other than rheumatoid arthritis can also affect joints, and differential diagnosis of rheumatic diseases is often difficult owing to the similar clinical manifestations. However, accurate diagnosis is crucial for an appropriate treatment strategy. The utility of fluorine 18 fluorodeoxyglucose (FDG) PET/CT has been established, and it is widely used for assessing malignancies. In addition to accumulating in tumor cells, FDG also accumulates in inflammatory tissue, allowing FDG PET/CT to demonstrate arthritis. PET/CT allows evaluation of whole-body articular and extra-articular lesions in one examination, representing a key advantage over US and MRI, which allow assessment of only a few regions because of their limited field of view. Although FDG PET/CT is sensitive for detecting inflammatory lesions, the uptake itself is nonspecific; therefore, knowledge of characteristic uptake patterns is necessary to narrow the differential diagnosis in rheumatic disease. Furthermore, pathognomonic extra-articular findings such as vasculitis, skin lesions, lymphadenopathy, and chondritis play an important role in achieving accurate diagnosis. The authors present the FDG PET/CT appearances of (a) rheumatoid arthritis and allied disorders (polymyalgia rheumatica, remitting seronegative symmetrical synovitis with pitting edema, adult-onset Still disease), (b) spondyloarthritis (ankylosing spondylitis, psoriatic arthritis, reactive arthritis, inflammatory bowel disease arthritis, SAPHO [synovitis, acne, pustulosis, hyperostosis, and osteitis] syndrome, chronic recurrent multifocal osteomyelitis), and (c) miscellaneous systemic disorders with arthropathy (relapsing polychondritis, multicentric reticulohistiocytosis, amyloidosis, sarcoidosis, hemophilia). ^©RSNA, 2020.

Tiger Man Sign-F-18 FDG PET CT Scan Pattern in Muscular and Cutaneous Sarcoidosis: A Case Report and Literature Survey

Sarcoidosis is a chronic granulomatous disorder of unknown etiology which primarily affects the respiratory system. However, 0.5%–2.5% of patients with sarcoidosis show muscle involvement, namely sarcoid myopathy. F-18 Fluorodeoxyglucose positron-emission tomography (F-18 FDG PET) has become an important component of the diagnostic algorithm of these patients, owing to its ability to assess disease extent and identify occult sites of disease involvement and guiding sites of biopsy. Awareness of pattern of FDG uptake in sarcoid myopathy not only helps in identifying muscular involvement in already known cases but also helps in the initial diagnosis of sarcoidosis as in the present case.

Prevalence, distribution and clinical significance of joints, muscles and bones in sarcoidosis: an 18F-FDG-PET/CT study

OBJECTIVES

In Sarcoidosis joints-muscles-bones (JMBs) localizations are of the least common. ¹⁸F-FDG-PET/CT imaging revolutionized detection of JMBs involvement by adding metabolic activity information and allowing for a comprehensive, whole-body mapping of the disease.

AIM AND METHODS

This study investigated prevalence, distribution, and clinical significance of JMBs sarcoidosis in 195 consecutive patients that underwent ¹⁸F-FDG PET/CT examination.

RESULTS

Joint and bone involvement were encountered in 15% of patients with a mean of the maximum-standardized-uptake-value (SUV_max) of 6.1. Most common location was the axial skeleton. Hypercalciuria was significantly more frequent in patients with osseous involvement (p = 0.003). Muscle activity (SUVmax = 2.4) was encountered in 20% of the patients, most frequently in treatment-naïve (p = 0.02). The muscles of the lower extremities were affected the most. Muscle and bone localization coexist in 50% of the cases. JMBs disease was almost asymptomatic, not related to chronicity but to pulmonary, nodal, and systemic disease. Long-term follow-up and treatment response of affected patients confirmed sarcoidosis.

CONCLUSION

¹⁸F-FDG-PET/CT revealed JMBs localizations and coexistence with other organ sites supporting the concept that sarcoidosis is a systemic disease. By allowing an integrative interpretation of multi-organ involvement in the context of a pattern highly suggestive of sarcoidosis, it strongly keeps-off the diagnosis of malignancy.

Infection and Inflammation Imaging: Beyond FDG

This review discusses nuclear imaging of inflammation using molecular probes beyond fluoro-d-glucose, is structured by cellular targets, and focuses on those tracers that have been successfully applied clinically.

Emerging phenotypes of sarcoidosis based on 18F-FDG PET/CT: a hierarchical cluster analysis

Objectives: In sarcoidosis, the definition of organ involvement with traditional means appears laborious and somewhat controversial, and phenotyping by the above overlapping. ¹⁸F-FDG PET/CT defines disease extent by activity more precisely, and may result in a better understanding of sarcoidosis disease behavior and phenotypes expression. We hypothesized that ¹⁸F-FDG PET/CT could add in the phenotyping of sarcoidosis patients by unveiling in detail sites of involvement even in clinically and physiologically silent disease.Methods: This study was designed to investigate the role of ¹⁸F-FDG PET/CT in phenotyping sarcoidosis using cluster analysis by adding this new means in the routine work-up of 195 sarcoidosis patients of a single academic center.Results: ¹⁸F-FDG PET/CT succeeded to identify despite the random distribution of the disease, an ordered stratification into 4 phenotypes: I) thoracic nodal hilar-mediastinal, II) thoracic nodal hilar-mediastinal and lungs, III) an extended thoracic and extra-thoracic only nodal phenotype including inguinal-abdominal-supraclavicular stations, and IV) all the above plus systemic organs and tissues such as muscles-bones-spleen and skin.Conclusion: Though further studies are necessary to confirm findings as patterns of disease behavior; the proposed phenotypes may prove useful in the design of future studies with homogeneous cohorts facilitating in sarcoidosis patients a personalized medicine approach.

Molecular Imaging of Infection: The First 50 Years

Despite significant advances in the understanding of microorganisms and an increased availability of antimicrobial therapy, infection remains a major cause of morbidity and mortality. The diagnosis can be challenging and imaging studies often are used for confirmation and localization. For nearly 50 years, molecular imaging agents have played an important role in the diagnosis of infection. Gallium-67 citrate was perhaps the first molecular imaging agent used for diagnosing and localizing infection. Poor imaging characteristics, along with a lack of specificity, and the long (usually 48-72 hours) interval between administration and imaging motivated investigators to search for alternatives. Currently the role of ⁶⁷Ga is limited to differentiating acute tubular necrosis from interstitial nephritis and as an alternative to ¹⁸F-FDG for indications, such as sarcoid, spondylodiscitis, and fever of unknown origin, when the latter is not available. The development, in the mid-1970s, of techniques for radiolabeling leukocytes that subsequently migrate to foci of infection was a significant advance and labeled leukocyte imaging still has a preeminent role in molecular imaging of infection. There are significant disadvantages to in-vitro labeled leukocyte imaging. Efforts devoted to developing in-vivo leukocyte labeling methods, however, met with only limited success. Over the past 20 years ¹⁸F-FDG has established itself as the molecular imaging agent of choice for fever of unknown origin, vasculitis, sarcoid, and spondylodiscitis. As useful as these agents are, their uptake is based on the host response to infection, not infection itself. Previous attempts at developing infection specific agents, including radiolabeled antibiotics, antibiotics, and vitamins like biotin were limited by poor results and/or limited availability and so investigators continue to focus on developing infection specific molecular imaging agents. Initial results with radiolabeled nucleoside analogs, sugars, and amino acids, and a renewed interest in radiolabeled antibiotics for both diagnosis and monitoring treatment are exciting and hold great promise for the future.

PET/CT Imaging in Soft Tissue Infection and Inflammation-An Update

Nuclear medicine procedures, including Ga-67 and labeled leucocyte SPECT/CT as well as PET/CT using 18F-FDG and recently Ga-68 tracers, have found extensive applications in the assessment of infectious and inflammatory processes in general and in soft tissues in particular. Recent published data focus on summarizing the available imaging information with the purpose of providing the referring clinicians with optimized evidence based results. Guidelines and/or recommendations of clinical societies have incorporated nuclear medicine tests (using both labeled leucocytes and FDG) in their suggested work-up for evaluation of infective endocarditis and in certain patients with suspected vascular graft infections. Joint guidelines of the European and American nuclear medicine societies include fever of unknown origin, sarcoidosis, and vasculitis among the major clinical indications that will benefit from nuclear medicine procedures, specifically from FDG PET/CT. Limitations and pitfalls for the use of radiotracers in assessment of infection and inflammation can be related to patient conditions (eg, diabetes mellitus), or to the biodistribution of a specific radiopharmaceutical. Limited presently available data on the use of functional and/or metabolic monitoring of response to infectious and inflammatory processes to treatment and with respect to the effect of drugs such as antibiotics and glucocorticoids on the imaging patterns of these patients need further confirmation.

Isolated Muscular Sarcoidosis Revealed by Hypercalcemia and 18F-FDG PET/CT

A 43-year-old woman, with previous history of renal lithiasis, was admitted on an emergency for severe hypercalcemia fortuitously discovered in a context of rapidly progressive kidney failure. An F-FDG PET/CT performed to rule out underlying malignancy revealed an intense diffuse and isolated muscular FDG uptake with fascia infiltration on the CT finding. A muscular biopsy was performed and demonstrated a non-necrosing granuloma with multinucleated giant cells consistent with muscular sarcoidosis. A corticotherapy was started with a rapid normalization of serum calcium level. The follow-up F-FDG PET/CT 4 months later showed a complete response of the sarcoidosis myositis.