Role of 18F-FDG PET/CT for providing a targeted approach for etiology of PUO.

AIM: This study aimed to evaluate the potential role of 18F-fluorodeoxyglucose PET/computed tomography (18F-FDG PET/CT) in providing a targeted approach for diagnosing the etiology of Pyrexia of Unknown Origin (PUO). METHODS: A total of 573 PUO patients were included in this ambispective study, with a mean age of 39.40 ±â€…4.6 years. Patients underwent FDG PET/CT scans using dedicated hybrid scanners. PET/CT data were interpreted by experienced nuclear medicine physicians. The study analyzed the guidance provided by FDG PET/CT for appropriate biopsy sites and assessed concordance between PET/CT findings and histopathological examination. RESULTS: Out of the 573 patients, a final diagnosis was reached for 219 patients, including malignancy, infectious causes, noninfectious inflammatory causes (NIID), and precancerous conditions. FDG PET/CT played a crucial role in guiding clinicians to appropriate biopsy sites, contributing to a higher diagnostic yield. Concordance between PET/CT findings and histopathological examination emphasized the noninvasive diagnostic potential of PET/CT in identifying underlying causes of PUO. Overall, FDG PET/CT contributed to guiding the appropriate site of biopsy or concordance of the first differential diagnosis with the final diagnosis in 50.05% of cases. CONCLUSION: This study highlights the valuable role of FDG PET/CT in providing a targeted approach for diagnosing PUO, showcasing its potential in guiding clinicians towards appropriate biopsy sites and improving the diagnostic yield. The findings underscore the importance of integrating FDG PET/CT into the diagnostic pathway for PUO, ultimately enhancing patient management and outcomes. Further prospective studies are necessary to validate these results and refine the integration of FDG PET/CT in the diagnosis of PUO.

Discordant Molecular Imaging Findings with 2-[18F]FDG and [68Ga]Ga-PSMA PET/CT in a Patient with Both Bladder and Prostate Cancer.

The prevalence of double primary prostate and bladder cancer is not uncommon. Though both share a common pathway of malignant transformation, they bear to differ in the case of 2-[18F]FDG PET/CT and [68Ga]Ga-PSMA uptake. We present a case of double primary cancer involving the bladder and prostate, where the prostatic primary showed intense [68Ga]Ga-PSMA uptake with non-avid skeletal and pulmonary metastases, which showed intense 2-[18F]FDG uptake, thus showing discordance due to different clonal origins.

Axillary Lymph Node in Extra-Ocular Retinoblastoma - Benign or Malignant?

A 1-year-old male child presented with whitish discoloration of pupil of the left eye and swelling over the left axilla. A contrast-enhanced magnetic resonance imaging of the brain and orbits performed revealed left eye extra-ocular retinoblastoma. 18F-fluorodeoxyglucose positron emission tomography/computed tomography scan was done in this child as a part of baseline staging of retinoblastoma in an ongoing research project. The scan revealed left eye extra-ocular retinoblastoma along with calcified left axillary level I lymph node.

99mTechnetium-Ubiquicidin Scan with Single-Photon Emission Computed Tomography/Computed Tomography in Skull Base Osteomyelitis.

Malignant otitis externa (MOE) with skull base osteomyelitis (SBO) is an aggressive infection that predominantly affects elderly, diabetic, or immunocompromised patients, and is associated with high disease-specific mortality. Pseudomonas aeruginosa is the most isolated microorganism. External otitis associated with granulation tissue and pain is the most common presenting feature; a biopsy is obtained to rule out malignancy. A proper consensus is lacking regarding the best imaging modality for early initial diagnosis and follow-up. 99mTechnetium (99mTc)-labeled ubiquicidin (UBI) 29-41 is a bacterial attaching peptide that does not bind to activated leukocytes. We report a case of SBO initially misdiagnosed as a chronic otitis media, but later proved to be a case of MOE. 99mTc methylene diphosphonate bone scan and 99mTc-UBI 29-41 scan with single-photon emission computed tomography/computed tomography scans were performed to corroborate the clinical diagnosis. SBO remains a great challenge due to its increasing prevalence and high morbidity are difficult to diagnose and are often confused with cholesteatoma and neoplastic process. The UBI scan could be an auxiliary noninvasive diagnostic alternative in early diagnosis.

Diagnostic accuracy of RBC scintigraphy and CTA for detection of patients with suspected lower gastrointestinal bleeding: a systematic review and meta-analysis.

OBJECTIVE: Detection of lower gastrointestinal bleeding (LGIB) through noninvasive modalities is very important in the successful management of LGIB. RBC scintigraphy and CT have a role in the detection of LGIB and guiding the management of patient by localization of the bleeding site. However, only a small number of studies have evaluated the role of RBC scintigraphy and CT in the diagnosis of LGIB. This systematic review was conducted to evaluate the diagnostic performance of RBC scintigraphy and CT in the detection of LGIB in patients with clinical or biochemical findings suspicious of LGIB. METHODS: This systematic review followed PRISMA guidelines. Searches in PubMed, Scopus, and Embase were conducted using relevant keywords, and articles published through 30 April 2022, were included. Using endoscopy or surgical outcomes as the reference standard, the numbers of true and false positives and true and false negatives were extracted. Pooled estimates of diagnostic test accuracy - including sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and summary ROC (SROC) curve - were generated using bivariate random-effects meta-analysis. RESULTS: Three studies comprising 171 patients were included in the systematic review and meta-analysis. The pooled sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio for the detection of LGIB using RBC scintigraphy were 0.787 (95% CI, 0.643-0.893), 0.289 (95% CI, 0.164-0.443), 1.214 (95% CI, 0.923-1.597) and 0.576 (95% CI, 0.296-1.121) respectively. The area under the SROC curve was 0.73. The pooled sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio for the detection of LGIB using CT were 0.931 (95% CI, 0.772-0.992), 0.870 (95% CI, 0.737-0.951), 6.085 (95% CI, 0.840-44.097), 0.126 (95% CI, 0.006-2.509) respectively. The area under the SROC curve was 0.095. CONCLUSION: RBC scintigraphy has overall good sensitivity and CTA has excellent sensitivity specificity, positive and negative likelihood ratio in the detection of LGIB in patients with clinical or biochemical findings suspicious for LGIB.CTA along with RBC scintigraphy can be used algorithmically to rule out patients who do not have a localization for the site of LGIB thereby helping these patients to avoid invasive procedures like endoscopy or surgical explorations.

68Ga-DOTANOC PET/CT for Screening and Surveillance of Von Hippel-Lindau (VHL) disease.

Purpose: Hereditary tumor syndrome Von Hippel-Lindau (VHL) disease is characterized by various benign and malignant tumors that are known to express somatostatin receptors (SSTR). We evaluated the role of 68Ga-DOTANOC PET/CT scan in patients with positive germline mutation of the VHL gene, presented initially or on follow-up, for the detection of recurrent or synchronous/metachronous lesions. Methods: Fourteen patients (8 males; 6 females) with mean age 30 ± 9.86 years were retrospectively analyzed, were tested positive for VHL on gene dosage analysis, and underwent 68 Ga-DOTANOC PET/CT scan for disease evaluation. The number and site of lesions were determined. The tracer uptake was analyzed semi-quantitatively by calculating the maximum standardized uptake values (SUVmax) of lesion. Results: Four of the 14 patients underwent scan for initial diagnosis as baseline, 6 patients for post-therapy disease status, and 4 patients for initial diagnosis as well as follow-up evaluation of the disease. A total of 67 lesions were detected in 14 patients. The sites of lesions were cerebellar/vertebral/spinal (17; mean SUVmax = 7.85); pancreatic neuroendocrine tumor (NET) (11; mean SUVmax = 20.64); retina (3; mean SUVmax = 10.46); pheochromocytoma (10; mean SUVmax = 16.32); paragangliomas (3; mean SUVmax = 10.65); pancreatic cyst (9; mean SUVmax = 2.54); and renal cyst (8; mean SUVmax = 1.56) and miscellaneous lesions constituted 6 lesions. Conclusion: Our results show that 68 Ga-DOTANOC PET/CT may be a useful modality for screening and follow-up of associated tumors in patients with germline gene mutation for VHL. It can be used as a one-stop imaging modality for VHL patients and may substitute for separate radiological investigations, making it more convenient for patients in terms of time and cost.

Role of 18 F-FDG PET/CT in the diagnosis of benign vs. malignant tumor thrombus.

PURPOSE: Hypercoagulable state is a complication of various infections, and inflammatory processes and is a common scenario in cancer patients also. Timely diagnosis and treatment are essential to reduce further complications in such patients. The present study aimed to assess the role of FDG PET/CT in the diagnosis of benign vs. malignant tumor thrombus and to determine cut-off SUVmax to differentiate them. PATIENTS AND METHODS: We retrospectively reviewed all FDG PET/CT scans of patients done in our department from January 2017 to March 2022. All scans were reviewed by two experienced nuclear medicine physicians. A total of 135 patients who had venous or arterial thrombus in FDG PET/CT scans were included. All the FDG PET/CT scans of 135 patients were analyzed for primary tumor site and/or site of thrombus. Additional clinical data were collected for patients with benign conditions in the form of ESR and CRP if available and doubtful cases were followed up by HPE reports and/or CEMRI. The SUV max of the primary tumor(in cancer patients), thrombus, and background (aorta) were calculated. RESULTS: A total of 135 patients (108 cancer patients and 27 with benign thrombus) were included with an age range of 3 to 86 years (median 50 years). There were 91 males and 44 females. Of 108 cancer patients, the most common cancers were hepatocellular cancer - 38 (35.18%), renal cell cancer - 28(25.92%), and carcinoma of the thyroid - 6 (5.55%). Of 108 cancer patients, 36 (33.33%) had tumor thrombosis in inferior vena cava, 31 (28.70%) in the portal vein, and 41 (37.96%) in other vessels (renal vein, jugular vein, etc.). Of 27 patients with benign conditions,13 had venous thrombi, 11 had arterial thrombus and three had atrial thrombus and the most common thrombus sites were thoraco-abdominal aorta in seven (25.92%) and right atrium in three (11.11%) patients. In the subgroup of 108 oncological patients, the mean SUV max of the primary tumors was 17.67 (range 2.1-91.0; median 10.82), thrombi were 17.61 (range 2.14-90.11; median 14.56) and background was 5.29 (range 0.29-25.00; median 3.12). Of 27 patients with benign conditions, the mean SUV max of the thrombi was 11.09 (range 1.98-31; median 8.10) and the background was 9.80 (range 1.46-24.50; median 10.20) The ESR was raised in 13 of 26 patients (mean 35.84, range 10.98-62.00, median 35.00) and CRP was raised 22 of 26 patients (mean11.46, range 3.45-24.50, median 20.40). Upon plotting the receiver operating curve, a cutoff SUV max of 12.7 with a sensitivity of 62.96% and specificity of 77.77% was produced to demarcate tumor thrombus from benign thrombus. CONCLUSION: FDG PET/CT plays a significant role in the detection of thrombo-embolic disease and can differentiate benign thrombus from tumor thrombus.

Incidentally Detected Gastrointestinal Stromal Tumor in a Patient with Carcinoma Prostate: 68Ga-Prostate-Specific Membrane Antigen Versus 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography.

Uptake of 68Ga-prostate-specific membrane antigen (PSMA) in various nonprostatic tumors is well documented in the literature. We present a case of a gastrointestinal stromal tumor, incidentally detected on 68Ga-PSMA positron emission tomography/computed tomography imaging in a patient who underwent imaging for a suspected recurrence of carcinoma prostate.

Renal Dynamic Scintigraphy as a Sensitive Tool for Detecting Small Volume Urinoma Following Live-Related Renal Transplant.

Renal transplant (RT) is the preferred treatment modality in patients with end-stage renal disease (ESRD). However, it is associated with a significant rate of complications. Early diagnosis and management of these complications are essential to prevent graft loss. Herein, we describe a case of a 48-year-old male who developed ESRD due to underlying autosomal-dominant polycystic kidney disease and underwent an RT. A routine renal dynamic scintigraphy (RDS) performed on day 4 posttransplant showed a focal minute area of radiotracer accumulation on the delayed static images raising suspicion for urinoma. However, it was deemed normal considering the normal renogram curve and stable clinical condition of the patient. However, on day 9 posttransplant, in view of clinical deterioration marked by decreasing urine output and rising serum creatinine levels, ultrasonography - kidney, ureter, and bladder (USG-KUB) and a repeat RDS were performed. Although the USG-KUB described a peri-nephric fluid collection, the nature of the collection could not be determined. RDS confirmed that the collection was urinoma. On retrospective analysis, the focal area of increased radiotracer uptake corresponded to the site of initial suspicion, although there was an increase in the size of the same. In experienced hands, RDS thus proves to be a highly sensitive tool for the diagnosis of urinoma, much before the clinical complications set in.

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.

F-18 DOPA PET/CT in pediatric patients with hyperinsulinemic hypoglycemia: A correlation with genetic analysis.

AIM: Persistent hyperinsulinemic hypoglycemia is a rare but life-threatening disease of infancy and childhood. 18F-DOPA PET/CT has been shown to be a useful modality in the localization of focal pancreatic lesions in these patients. We aimed to assess the role of 18F-DOPA PET/CT in such patients at our institution. MATERIALS AND METHODS: In this prospective study, 18F-DOPA PET/CT scans and clinical details of 20 children with clinical diagnosis of hyperinsulinemic hypoglycemia were reviewed. Scans were acquired at 5 min postinjection of 2-3 mCi of 18F-DOPA on dedicated PET/CT scanners (Biograph mCT, Siemens Inc and Discovery PET/CT, GE). Abdominal spot images over 1-2 bed positions were acquired. Additionally, genetic mutation status, where available, was correlated to the scan findings. RESULTS: Out of 20 children (7 female and 13 male), 13 were infants. The age of the children ranged from 3 months to 8 years. Fifteen children had undergone gene analysis, 12 were positive for mutation in ABCC8, 1 for GLUD-1, 1 for GCK mutations and 1 had not shown any mutation. 18F-DOPA PET/CT scan showed 5 focal pancreatic lesions in 5 children (1 in each), two focal lesions in 1 child and diffuse pancreatic uptake in 14 children. CONCLUSION: 18F-DOPA PET/CT is a useful modality for localizing focal pancreatic lesions in children with persistent hyperinsulinemic hypoglycemia. The detection rate is significantly higher in patients with ABCC8 paternal monoallelic recessive gene mutation. 18F-DOPA PET/CT scan consequent to findings on genetic analysis appears to be useful in planning the management of children with hyperinsulinism.

Omicron Variant of COVID-19: Imaging Pattern on F-18 Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography.

We report a case of omicron infection in a biopsy-proven case of carcinoma breast sent for staging F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) during the omicron COVID wave. FDG PET/computed tomography (CT) revealed increased FDG uptake in nasopharyngeal, oropharynx, and tonsillar regions and bilateral cervical lymph nodes along with uptake in primary carcinoma and locoregional lymph nodes. Based on the clinical history and specific pattern of FDG PET/CT findings (as suggested by SNMMI Taskforce), COVID history and reverse transcription polymerase chain reaction positivity was elicited.

A Curious Case of Suspicious Lymphadenopathy in a Hereditary Spherocytosis Patient Reported as Extramedullary Hematopoiesis.

We present a case of a 23-year-old male patient with complaints of fever, cough, and persistent anemia for the past 6 months and with a known history of hereditary spherocytosis. Computed tomography (CT) thorax demonstrated multiple paravertebral lesions in the bilateral thoracic cavities, suggestive of lymphadenopathy; subsequently, 18Flurodeoxyglucose PET/CT was done with suspicion of lymphoma, which showed no significant metabolic activity in those lesions. Thus, in view of clinical and metabolic status, lesions were considered extramedullary hematopoiesis (EMH). This case highlights the importance of considering EMH, while interpreting suspicious lymphadenopathy in cases of chronic anemia and also possible scan findings in the same.

Solitary Subcutaneous Tissue Metastasis as Recurrence in a Case of Primary Angiosarcoma of Breast: Findings on 18F-Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography.

Primary angiosarcomas of the breast are rare tumors, with a fatal outcome. We present a rare case of an operated primary angiosarcoma of the right breast in a 20-year-old female who showed disease recurrence in the right posterior arm subcutaneous tissue on 18F-fluorodeoxyglucose positron emission tomography-computed tomography after 1 year of surgery without any other visceral metastasis.

An Unusual Case of Simultaneous Cricoid and Thyroid Cartilage Metastases from Prostatic Adenocarcinoma on 68Ga-PSMA PET/CT.

Although prostate cancer can metastasize to any part of the body, laryngeal cartilage metastasis is extremely rare and few cases have been published so far. Here we present the case of a 65-year-old male patient, recently diagnosed with prostate adenocarcinoma, referred for staging with 68Ga-PSMA PET/CT. He was found to have extensive skeletal metastasis along with cartilage metastasis involving both thyroid and cricoid cartilages.

Extramedullary Infiltration in Multiple Organs in a Relapsed Case of Acute Lymphoblastic Leukemia on 18F-Fluorodeoxyglucose Positron Emission Tomography.

T-cell acute lymphoblastic leukemia (ALL) is hematological malignancy with a propensity to involve extramedullary organs. We present the case of a 7-year-old child who was diagnosed with disease free from ALL for 1 year and then developed fever. 18F-fluorodeoxyglucose positron emission tomography/computed tomography revealed extramedullary infiltration of ALL in lungs, pancreas, kidneys, bone, muscles, and subcutaneous tissues.