Search

The novel coronavirus 2 pandemic is causing widespread disruption in everyday life necessitating urgent and radical adaptations in operating procedures at Nuclear Medicine facilities. The potential for causing severe illness, COVID-19, calls for strict observance of preventive measures aimed to mitigate the spread of the virus. The threat of COVID-19 is particularly serious as there is no vaccine and no specific antiviral therapy. Further complications are introduced by shortages of personal protective equipment for healthcare workers who have direct contact with patients and effective testing to identify infected patients, raising the need for delaying some testing and therapies. Certain vulnerable segments of the general population have been identified (advanced age and certain comorbidities), which should heighten further their preventive efforts. Therefore, this guidance is intended to be operationalized depending on a facility’s specific needs and local disease prevalence.

OBJECTIVE. The purpose of this study is to provide a concise summary of the current experience with (68)Ga-labeled prostate-specific membrane antigen (PSMA)–11 imaging of prostate and nonprostate malignancies and benign conditions. CONCLUSION. PSMA is overexpressed in prostate cancer and in the neovasculature of many other malignancies. The relevance of PSMA as a biologic target, coupled with advances in the design, synthesis, and evaluation of PSMA-based radionuclides for imaging and therapy, is anticipated to play a major role in patient care.

Distant metastases change the prognosis of patients with nasopharyngeal carcinoma (NPC) which most commonly metastasizes to the bone. 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) is reported as useful in imaging NPC metastases. Our study assesses the incidence and distribution of bone metastases detected by 18F-FDG PET/CT in NPC. 717 18F-FDG PET/CT scan reports of histologically proven NPC patients imaged in Singapore General Hospital, Singapore, between 2003 and 2009 were reviewed for the total number of metastases (scanned from vertex to mid-thigh) and analyzed for distribution. Of the 709 FDG avid metastases in these reports, 357/709 (50.35%) were locoregional nodal metastasis and 352/709 (49.65%) were distant metastases of which 192/709 (27.08%) of total metastases and 54.54% of distant metastases (192/352) were in the bones. The majority of the bone lesions 125/192 (65.1%) were in the axial skeleton with 109/192 (56.77%) in the lower skeleton (thoracolumbar spine, sacrum, and pelvis). The incidence of bone metastases in our study (27.08%) was higher than that reported in other studies, for example, 15% by Liu et al. and 11% (230 patients) by Caglar et al. Bone metastases have been reported in the femurs and the feet and as such some metastases may have been outside the field of view of the scans. In our study, 27% of FDG avid NPC metastases are in the bones.

Summary Introduction The only investigation to determine if a whole body FDG PET/CT scan is helpful in the evaluation of NPC is a study from Stanford. In this study, 26 patients with whole body PET/CT, were evaluated for lesions below adrenals and showed that 7.7% of distant metastases were below adrenals. Our study comparing distant metastases below diaphragm with Stanford study to evaluate the need for whole body PET/CT. Material and methods Reports of NPC patients in Singapore General Hospital were reviewed. The lesions were analyzed for total number and number below diaphragm. The lesions below the diaphragm were further analyzed if they were solitary or involved multiple areas and if any additional lesions were above diaphragm. Results 717 reports were included in final analysis. The number of FDG avid lesions in these reports was 709. Distant metastases represented 352 of the 709 lesions. The number of lesions below diaphragm was 152, of the lesions below diaphragm only 16 of lesions have no co-existing distant metastases above diaphragm. From these lesions, there were only 12 solitary lesions. The other 4 has concurrent metastases but all localized below diaphragm. Conclusion Compared to Stanford study, number of reports is more representative in this study and the yield is much lower (7.7% versus 2.26%). From the results of our study we can consider limiting the scan area from vertex to below diaphragm. However, the symptoms and clinical presentation of the patient will further direct the requesting physician in the area to be imaged.

Osseous metastatic disease from malignancy is a common occurrence with significant patient morbidity and mortality as well as increasing health care expenditures. Patient management plans frequently change with the identification of skeletal metastasis and the upstaging of disease status. Bone scintigraphy remains the current mainstay of diagnostic imaging procedures in nuclear medicine for the early detection of skeletal metastasis owing to their high sensitivity. Emerging positron tracers and the increasing use and availability of hybrid single-photon emission computed tomography and positron emission tomography (PET)/computed tomography machines enable physicians to diagnose metastatic disease in bones with superior accuracy. This review introduces the basics of PET and the commonly used positron tracers used to evaluate skeletal metastases.

A 56-year-old male patient with a rare dermatofibrosarcoma protuberans and fibrosarcomatous change (DFSPFS) presented with a solitary fluorodeoxyglucose (FDG)-avid tumour with no evidence of metastasis in the left upper extremity [Figure 1A]. This initial presentation was treated with wide excision, and then again at its recurrence 8 months later. At admission, the patient had symptoms of gastritis and underwent an oesophago-gastroduodenoscopy, which was normal. Almost 3 years after the initial presentation, the patient presented with a retroperitoneal mass measuring 1.4 x 0.8 cm. Investigation revealed the tumour, which was avid on FDG-PET/CT (standardised uptake value [SUV] max 11.3) and new compared to the previous study [Figure 2B]. Mild FDG uptake was also noted in a new pulmonary nodule (SUV max 1.9) and appeared malignant [Figure 3B]. Figure 4 shows the maximum intensity projection (MIP) images from the two studies. The retroperitoneal tumour was found to be dermatofibrosarcoma protuberans with extensive fibrosarcomatous transformation, histology grade 3 [Figures 5A and ​and5B5B]. Figure 1: Fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) scans at the same trans-axial levels, showing mildly FDG-avid local recurrence in the shoulder (A), with no lesion subsequently identified in the same region (B). Figure 2: Fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) scan at the same trans-axial level comparing the two scans at the time of local recurrence in 2006, when there was no retro-peritoneal lesion (A) and subsequently at ... Figure 3: Fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) scan at the same trans-axial level comparing the two scans at the time of local recurrence in 2006 when there was no pulmonary lesion (A) and subsequently at the time ... Figure 4: Maximum intensity projection of the fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) scans at the time of the first presentation in 2006 with (A) a mildly FDG-avid local recurrence, and (B) subsequently, in 2009, with ... Figure 5: (A) Pathology slide of low-powered view of fibrosarcoma with herring-bone pattern; (B) Pathology slide showing areas of viable tumor fascicles with adjacent necrosis DFSP is a rare cutaneous tumour of low malignant grade characterised by a pattern of slow, infiltrative growth and a marked tendency to recur locally after surgical excision.1 DFSP is commonly found on the trunk (42–72%), occasionally in the proximal extremities (16–30%), and infrequently above the neck (10–16%).7 Rare distant metastases (in less than 5% of cases) may occur many years after the onset of disease and are limited mostly to the lungs, followed by regional lymph nodes, while the visceral organs and bones are rarely affected.2 Metastases are more likely with repeated incomplete surgical excisions and by tumour de-differentiation to higher grades.6 Metastases are associated with local recurrence and poor prognosis. The 5-year survival rate is estimated at 99.2%.7 DFSP is a fibrosarcoma originating from dermal fibroblasts.6 The genetic abnormalities in DFSP include a supernumerary ring chromosome related to the low amplification of sequences of chromosomes 17 and 22 which is a form of balanced reciprocal translocation.8 This rearrangement will cause fusion of alpha chain type A (COL1A1) located on 17q22 to the platelet-derived growth factor beta (PDGFB) located on 22q13. As a result, the COL1A1-PDGFB gene formation will result in up regulation of PDGFB expression, resulting in continuous autocrine activation of PDGF receptor beta (PDGFR-B) and propagation of the mitotic signal by formation of autocrine and paracrine loops.9 These transformed cells are inhibited by the tyrosine kinase inhibitor imatinib mesylate with reported cases of response often documented with FDG.10 The surgical objective in DFSP is complete tumour excision with maximal normal tissue preservation. Hence, a wide local excision with lateral margins of at least 3 cm and including the underlying fascia is recommended. In addition, micrographic controlled excision (MCE) showed favourable outcomes in treating DFSP.6 FDG-PET/CT findings in a case of recurrence of dermatofibrosarcoma in the surgical scar have been reported.3 FDG-PET/CT has also been used to monitor response to imatinib mesylate in 2 reported cases of unresectable metastatic DFSP, with a decrease in tumour uptake of FDG after treatment documented in both cases.4–5 In the former case, this decrease in uptake coincided with clinical improvement as early as 2 weeks after commencement of the therapy.4 In contrast to our case, where a FDG-avid pulmonary lesion was noted on PET/CT, a previous case reported a pulmonary nodule which was noted on CT but not on FDG-PET. It was thought this may have been due to the size (8 mm). A case has also been reported where DFSP response to imatinib was noted on FDG-PET but not on CT.10 This is similar to findings in other malignancies. DFSP is a rare cutaneous tumour of low malignant grade. FDG-PET/CT has been reported to be useful in DFSP imaging for delineating disease extent, both in staging and recurrence, which can be useful in planning surgery. FDG has also been documented as assessing DFSP response to imatinib, showing response when none was noted on CT. Given the rarity of the disease there are no large studies to date but the existing data appears promising. We suggest that FDG PET/CT be considered as an important component of the treatment plan of patients with DFSP.

Circulating tumor cells (CTCs) are cells shed from tumors or metastatic sites and are a potential biomarker for cancer diagnosis, management, and prognostication. The majority of current studies use single or infrequent CTC sampling points. This strategy assumes that changes in CTC number, as well as phenotypic and molecular characteristics, are gradual with time. In reality, little is known today about the actual kinetics of CTC dissemination and phenotypic and molecular changes in the blood of cancer patients. Herein, we show, using clinical case studies and hypothetical simulation models, how sub-optimal CTC sampling may result in misleading observations with clinical consequences, by missing out on significant CTC spikes that occur in between sampling times. Initial studies using highly frequent CTC sampling are necessary to understand the dynamics of CTC dissemination and phenotypic and molecular changes in the blood of cancer patients. Such an improved understanding will enable an optimal, study-specific sampling frequency to be assigned to individual research studies and clinical trials and better inform practical clinical decisions on cancer management strategies for patient benefits.

A 25-year-old woman presented with a fever of 1-month duration. There were no specific localizing signs or symptoms. Apart from a raised serum C-reactive protein (108 mg/L, normal 0.2–8.8 mg/L) and erythrocyte sedimentation rate (129 mm/h, normal 3–15 mm/h), the blood tests were unremarkable, including a normal full blood count, autoimmune screen, and microbiology tests. The patient completed a course of antibiotics, but the fever persisted. A contrast-enhanced computed tomography (CT) scan of the abdomen and pelvis was performed to evaluate the cause of the prolonged fever. The CT scan showed multiple hypodense lesions in both kidneys (Fig. 1, white arrows), bulkiness of both ovaries (Fig. 1, black arrows), and permeative osteolytic lesions in the bony pelvis (Fig. 1, arrowhead). The differential diagnoses of a malignancy and an infection were entertained. AnF-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) scan was performed to evaluate the cause of fever, assess the extent of involvement, and determine the most suitable site of biopsy. The FDG PET/CT scan showed multiple hypermetabolic lesions in both kidneys (maximum standardized uptake value, SUVmax 16; Fig. 2, arrows), both ovaries (SUVmax 24; Fig. 2, dotted arrow), and multiple bones of the axial and appendicular skeleton, including the calvarium, clavicles, scapulae, multiple ribs bilaterally, multiple vertebrae, bony pelvis, and proximal femora (SUVmax 27; Fig. 2, arrowheads). No nodal disease was detected. A bone marrow aspiration and trephine biopsy were performed, and the results revealed the diagnosis of a diffuse large B-cell lymphoma (DLBCL). The imaging and histopathological findings were compatible with a primary multifocal extranodal DLBCL with extensive involvement of the kidneys, ovaries, and bones. After three cycles of R-CHOP chemotherapy (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone), a repeat FDG PET/CT scan showed a complete metabolic resolution of the lesions in the kidneys, ovaries, and bones, indicative of an excellent treatment response (Fig. 3). The patient went on to complete six cycles of chemotherapy, and achieved complete remission. DLBCL is the largest subtype of non-Hodgkin lymphoma (NHL). Extranodal involvement in the NHL is common with primary extranodal lymphoma accounting for approximately one third of the NHL cases [1, 2]. Extranodal lymphoma can occur in any organ, and can be multifocal involving two or more organs. The most common site of primary extranodal lymphoma is the gastrointestinal tract; the other common sites include the skin, central nervous system and testis [2–4]. Kidneys and ovaries are relatively uncommon sites of primary extranodal lymphoma [2–4]. Concurrent involvement of the kidneys, ovaries and bones in a primary multifocal extranodal lymphoma is an uncommon presentation of a common condition. Lymphoma is a known cause of a fever of unknown origin (FUO). FDG PET/CT scan has been shown to be useful in the evaluation of FUO [5]. FDG PET/CT scan allows a quick and non-invasive screen of the whole body, and is useful in localizing the source of fever and determining the most accessible site to guide further diagnostic procedures like a biopsy [5]. Hence performing an FDG PET/CT early in the investigation of a prolonged fever may potentially lead to a quicker diagnosis and help to expedite the treatment. S.-J. Lu (&) M. M. L. Tan S. Osmany Department of Nuclear Medicine and PET, Singapore General Hospital, Outram Road, Singapore 169608, Singapore e-mail: suat_jin_lu@yahoo.com

Erdheim-Chester disease is a rare non-Langerhans cell histiocytosis characterized by progressive histiocytic proliferation with multiorgan involvement, typically of the kidney, skin, brain, and lung, and less frequently, the heart and retro-orbital tissue. Fluorine-18 fluorodeoxyglucose positron emission tomography (F-18 FDG PET) plays an important role in the management of this disease. It has been reported that FDG PET imaging allows accurate evaluation of the extent of the disease at baseline, as well as assessment of response to any specific therapy. In this case, a 57-year-old Chinese man presented with functional decline and a urinary tract infection. He had a prior history of xanthogranulomas of bilateral canthal masses. On imaging, he was found to have left hydronephrosis, diffuse urothelial thickening, increased density of the perinephric fat, mural thickening of the descending aorta and soft tissue masses along the posterior wall of the right atrium extending into the region of the interatrial septum and involving the right atrioventricular groove. Histopathology revealed retroperitoneal fibrosis. An IV contrast-enhanced FDG PET scan showed increased activity in a previously unidentified brain stem mass and the shafts of bilateral femora. Varying levels of FDG uptake were seen in the other lesions.

Clinically metastases to the thyroid are rare with an autopsy series incidence ranging from 1.25% to as high as 24% in widespread malignancy. Although detection of metastasis to the thyroid gland often indicates poor prognosis, aggressive surgical and medical therapy may be effective in a small percentage of patients. In this article we describe F-18 FDG PET/CT images of metastases to the thyroid in a case of nasopharyngeal carcinoma (NPC). Because anaplastic NPC metastases to the thyroid are rare, it is important to make a correct diagnosis, so that appropriate treatment may be chosen.