Unusual Artifacts Encountered during Routine Studies on Positron Emission Tomography-Computed Tomography and Gamma Camera.

Artifacts in nuclear medicine imaging are not uncommon. We are aware of some of these, for which we follow necessary protocols to avoid them. However, there are some unusual and unavoidable artifacts that we come across in daily imaging, which may be of concern and need to be detected and corrected on time. Hence, sharing a few such unusual artifacts we encountered while performing routine studies on positron emission tomography-computed tomography and gamma cameras, evaluating the cause and possible precautions.

Evaluation of treatment response by Hopkins criteria on 18 F FDG PET-CT in patients of non-small cell lung cancer and its comparison with PERCIST response criteria.

AIM: To assess treatment response on FDG PET-CT in NSCLC patients by visual Hopkins score compared to PERCIST criteria and its potential for prognostication (or its correlation with survival). METHODS: Forty-four NSCLC patients with baseline and post-treatment FDG PET-CT scans were included, and interpreted using Hopkins and PERCIST criteria classifying patients into responders and non-responders. PERCIST-based CMR and PMR, and Hopkins Scores 1,2,3 were classified responders. PERCIST-based SD and PD and Hopkins scores 4,5 were classified as non-responders. Patients were followed upto 24 months after treatment completion. Cohen kappa for inter-criteria agreement and Kaplan Meir curve for overall survival (OS) analysis done. RESULTS: Out of 44 patients, PERCIST classified 27 (61.3%) as responders and 17 (38.6%) as non-responders, whereas Hopkins classified 12 patients (27.3%) as responders and 32 (72.7%) as non-responders. Inter-criteria agreement was low (kappa=0.19) with discordance in 45.5% of patients. Eighteen of 20 discordant cases were non-responders on Hopkins and responders on PERCIST, of which 88.8% were non-responders on follow-up as predicted by Hopkins. PERCIST responders had OS of 96.4% and 64.3% at 9 and 24 months, respectively, while non-responders OS was 93.5% and 40.2% at 9 and 24 months, respectively ( P -value = 0.049). However, responders on Hopkins had OS of 100% at 24 months, whereas non-responders had OS of 93.5% and 51.5% at 9 and 24 months, respectively ( P -value = 0.232). CONCLUSION: Semi-quantitative PERCIST and visual Hopkins criteria show low inter-criteria agreement, with visual criteria better-predicting survival in patients of NSCLC.

18 F-FDG PET-CT Evaluation of Primary Adrenal Ewing Sarcoma with Venous Thrombosis: An Unusual Presentation.

Ewing sarcoma (EWS) is primarily an osseous malignancy of childhood and young adults. Extraskeletal occurrence is less frequent and primary adrenal involvement is an even rare presentation. We present such a case of a 7-year-old boy diagnosed with adrenal EWS with associated venous thrombosis and pulmonary embolism detected on 18 F-fluorodeoxyglucose positron emission tomography-computed tomography scan.

Mimicker of Osteoblastic Skeletal Metastasis on 18 F-FDG PET/CT Scan in a Case of Primary Mediastinal Germ Cell Tumor.

ABSTRACT: Primary mediastinal germ cell tumors are uncommon tumors, of which the nonseminomatous type is more likely to metastasize than the seminomatous type. Primary mediastinal germ cell tumors may also present with superior vena cava obstruction. Here, we present this case of primary mediastinal germ cell tumor with superior vena cava obstruction causing dilatation of collaterals in dorsal intravertebral venous plexus, which strongly mimics sclerotic skeletal lesions/metastasis on a Contrast-enhanced CT scan and also appears FDG avid on PET scan. Herein, we can differentiate the two by just a simple review of plain CT scan image.

Role of 18F-FDG PET/CT for detection of recurrence and metastases in renal cell carcinoma-are we underusing PET/CT?

PURPOSE The aim of this study was to compare 18F-fluorodeoxyglucose positron emission tomography- computed tomography (18F-FDG PET/CT) scan with computed tomography (CT) scan for detecting recurrence and metastasis in renal cell carcinoma patients. METHODS This retrospective study included patients from October 2013 to April 2017. Contrast-enhanced CT and PET/CT scans were compared and correlated with histopathology or/and follow-up studies. RESULTS Seventy-six patients, 60 males, were included. Lesions included primary renal, recurrent renal fossa lesions, lymph nodes, and distant metastatic lesions. Of 176 malignant lesions, CT detected 157 lesions; of which, 154 were true positive. Twenty-two false-negative lesions showed abnormal FDG uptake. CT scan had positive predictive value (PPV), negative predictive value (NPV), sensitivity, specificity, and accuracy of 98.0%, 37.1%, 87.5%, 81.2%, and 86.9%, respectively. All 176 lesions were PET/CT-positive. PET/CT had PPV, NPV, sensitivity, specificity, and accuracy of 100% each. The specificity and NPV of PET/CT were superior (P < .05). CONCLUSION PET/CT appears more accurate than CT scan for detecting metastasis and recurrence in renal cell carcinoma patients.

Post-COVID-19 Unusual Inflammatory Syndromes Detected on 18F-FDG PET/CT Scan.

ABSTRACT: SARS-CoV-2 is primarily known to cause respiratory symptoms. However, in this global COVID-19 pandemic, we have come across many extrapulmonary manifestations during and in the immediate post-COVID phase such as gastrointestinal symptoms, kidney and liver injury, myocardial dysfunction and acute coronary syndromes, and neurological, thromboembolic, dermatological, and musculoskeletal disorders. We present 2 such unusual cases of post-COVID complications-diffuse panniculitis and inflammatory myositis, as well as their clinical and FDG PET/CT imaging features.

Incidental Detection of Mandibular Metastasis in Renal Cell Carcinoma on 99mTc-MIBI Scan.

ABSTRACT: MIBI scintigraphy is the most widely used modality to identify parathyroid adenomas preoperatively. However, MIBI is also known to accumulate in multiple benign and malignant lesions. In renal cell carcinoma, 30% of the patients present with distant metastasis, commonly lungs and bone; however, jaw bone metastases are extremely rare (<1% of oral malignancies). Here we present a rare case of MIBI-avid mandibular metastasis in bilateral renal cell carcinoma on 99mTc-MIBI scintigraphy. Thus, we emphasize on careful interpretation of 99mTc-MIBI scans, which in addition to parathyroid adenomas can incidentally detect concurrent malignant lesions.

Role of 18F-Fluorodeoxyglucose Positron Emission Tomography-Contrast-Enhanced Computed Tomography in Detection of Early Recurrence with Peritoneal Disease in a Case of Adrenocortical Carcinoma.

Adrenocortical carcinoma (ACC) is an uncommon and highly aggressive malignancy with a poor prognosis. Common sites of metastasis are lung, liver, and lymph nodes. We present a case of ACC in a 54-year-old female with an early disease recurrence of unusual hypervascular peritoneal metastatic abdominal-pelvic deposits detected on 18F-fluorodeoxyglucose positron emission tomography-contrast-enhanced computed tomography scan.

An Unusual Case of Urothelial Carcinoma of Bladder with Metastasis to Brain and Skeletal Muscles Evaluated on 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography.

Urothelial or transitional cell carcinoma is the most prevalent variant of urinary bladder carcinoma worldwide occurring in both men and women. There are a very few cases described in the literature with metastasis to skeletal muscles and even fewer cases with metastatic site in the brain. We present a case of high-grade urothelial carcinoma with metastasis to the left temporal lobe as well as multiple inter- and intra-muscular deposits in the left thigh.

An Unusual Case of Bilateral Ureteric Metastasis on PSMA PET-CT Scan in Carcinoma Prostate.

ABSTRACT: The most common locations for metastasis in adenocarcinoma of the prostate gland are lymph nodes, bone, lung, and liver. The involvement of the ureter as a site of metastasis in prostate carcinoma is quite rare in literature. Here we present a case involving bilateral ureters along with bilateral vesicoureteric junctions in a known case of prostate adenocarcinoma.

Regorafenib-Associated Acute Pancreatitis Diagnosed on 18F-FDG PET/CT.

ABSTRACT: A 23-year-old man with metastatic osteosarcoma, with disease progression on conventional chemotherapy, was treated with regorafenib, a multikinase inhibitor. After treatment for 6 months with regorafenib, 18F-FDG PET/CT scan demonstrated FDG uptake in a necrotic space-occupying lesion involving tail of pancreas. After imaging, patient described symptoms of epigastric pain with elevated serum amylase and lipase levels, confirming diagnosis of regorafenib-induced pancreatitis, because patient had no other causative factors of pancreatitis. Physicians should be aware of rare and possibly clinically silent adverse effects of tyrosine kinase inhibitors, like acute pancreatitis, and recognize the 18F-FDG PET/CT findings to guide appropriate clinical management.

Pazopanib-Induced Asymptomatic Necrotizing Pancreatitis Diagnosed on 18F-FDG PET-CT Scan.

Multi-targeted tyrosine kinase inhibitor (TKI) pazopanib approved for the treatment of advanced soft tissue sarcoma (STS) has prolonged the estimated survival times and quality of life of patients. However, several adverse effects associated predominantly with the inhibition of the vascular endothelial growth factor receptor by these drugs may prove to be potentially life-threatening. One such rare adverse event with the use of pazopanib is acute pancreatitis. We present a case of asymptomatic necrotizing pancreatitis induced by pazopanib treatment for metastatic STS detected on 18F-FDG PET-CT imaging.

IgG4-Related disease simulating paraneoplastic syndrome: Role of 18FDG PET/CT imaging.

Immunoglobulin G4 (IgG4)-related systemic disease (IgG4-RSD) is a new systemic entity associated with autoimmune pancreatitis (AIP). Other organ involvements take the form of sclerosing cholangitis, sclerosing cholecystitis, sclerosing sialadenitis, retroperitoneal fibrosis, and interstitial nephritis. Recently, lung diseases related to IgG4 have been described to occur with or without other organ involvement. These diseases include interstitial lung disease (ILD), pulmonary inflammatory pseudotumor, and lymphomatoid granulomatosis. Most of these cases occur in combination with AIP, which also appears to have a general preponderance for males. The true incidence of IgG4-related ILD and the incidence of AIP are unknown. Here, we describe a case of a 53-year-old gentleman who presented with weight loss, fever, loose motions, altered sensorium, and persistent low hemoglobin, for which he was referred for 18-fluorodeoxyglucose positron emission tomography/computed tomography scan to diagnose probable underlying occult malignancy/paraneoplastic syndrome. It revealed features suggestive of IgG4 disease involving the pancreas and lungs, which was confirmed subsequently.

Unusual Asymptomatic Fluorodeoxyglucose Avid Pheochromocytoma in a Case of Myxoid Liposarcoma of the Extremity on 18-F Fluorodeoxyglucose Positron Emission Tomography-computed Tomography.

Sarcomas are a heterogeneous group of rare tumors and arise either from soft tissue or from bone. Soft-tissue sarcomas (STSs) initially metastasize to the lungs. Metastases to extrapulmonary sites such as liver, brain, and soft tissue distant from primary tumor usually develop later. However, cases with isolated adrenal metastasis without disseminated disease have been reported in literature. We present a case of primary myxoid liposarcoma of the lower limb, in which staging 18-F fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET-CT) scan detected a suspicious FDG avid adrenal lesion which eventually on resection was diagnosed as asymptomatic pheochromocytoma. Pheochromocytomas have been reported to demonstrate FDG uptake mimicking metastasis. Hence, while interpreting FDG PET-CT scans in the context of STSs, both the extrapulmonary metastatic potential of aggressive histological subtypes of sarcoma and rare possibility of FDG avid coexistent benign tumor should be taken into consideration.

Potassium Chloride Infusion as the Cause of Altered Bio Distribution of 18F-Fluorodeoxyglucose on Whole-Body Positron Emission Tomography-Computed Tomography Scan.

18F-fluorodeoxyglucose (18F-FDG) positron emission tomography-computed tomography is a standard diagnostic imaging tool in many types of cancer. Its physiological in vivo distribution includes the brain, liver, heart, kidneys, and urinary tract at 1 h after tracer injection. Skeletal muscle is known to show variable amounts of 18F-FDG uptake because it has a relatively high-glucose metabolism. We report a case of a 20-year-old patient with gross 18F-FDG uptake involving multiple muscle groups and its likely correlation to potassium chloride infusion before 18F-FDG injection.