Isolated Splenic Tuberculosis Masquerading as Disease Progression of Hodgkin's Lymphoma on Interim18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Scan.

18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) scan is the imaging modality of choice in the management of lymphoma. However, 18F-FDG is a nonspecific tracer for tumoral metabolic activity and infective pathology, thus posing a challenge in accurate response assessment. Here, we present a case of Hodgkin's lymphoma, referred for staging PET/CT scan which showed FDG-avid disease in the mediastinum, and on interim 18F-FDG PET/CT in addition to the mediastinal mass lesion, a FDG-avid lesion was also noted in the spleen suggestive of disease progression. The biopsy report of the lesion was tuberculosis, which was masquerading as disease progression on interim 18F-FDG PET/CT.

Metabolic Imaging Patterns on 18F-FDG PET in Acute and Subacute LGI1 Autoimmune Limbic Encephalitis.

Autoimmune encephalitis is a diverse group of neuropsychiatric disorders, which are difficult to diagnose clinically. The disorder presents acutely or subacutely with alteration of consciousness, cognitive decline, seizures, and abnormal movements. Autoantibodies are directed against intracellular antigens or extracellular domains of cell surface proteins, critical for neuronal excitability. F-FDG PET/CT has been used to diagnose the metabolic derangement in the brain due to various antibodies. Here we describe a case where acute and subacute phase of disease was visualized on serial F-FDG PET/CT.

18F-FDG PET/CT in Initial Diagnosis and Treatment Response Evaluation of Anti-NMDAr and Anti-GAD Dual Antibody Autoimmune Encephalitis.

We report a case of 34-year-old woman presenting with complaints of abnormal posturing of hand and tonic-clonic seizures of few days' duration, which soon progressed to psychotic episodes and injuries secondary to fall/abnormal movements. She underwent F-FDG PET for a suspicion of encephalitis, which revealed increased FDG uptake in the bilateral parietotemporal lobes (right more than left), anterior cingulate cortex, bilateral basal ganglia, thalami, and cerebellum. This atypical pattern did not conform to any known pattern of encephalitis, which was later attributed to the presence of both anti-NMDAr and anti-GAD antibodies in blood and cerebrospinal fluid.

Localization and restaging of carcinoma prostate by 68Gallium prostate-specific membrane antigen positron emission tomography computed tomography in patients with biochemical recurrence.

INTRODUCTION: Radical prostatectomy (RP) and radical radiotherapy (RT) are well established primary curative options for localized prostate cancer. Despite technical improvements, prostate-specific antigen (PSA)-recurrence after RP and RT is a common clinical scenario. We aimed to assess the role of 68Gallium (68Ga) prostate-specific membrane antigen positron emission tomography computed tomography (PSMA PET/CT) in patients with biochemical recurrence of prostate cancer after RP or RT for the detection and localization recurrent and metastatic disease. MATERIALS AND METHODS: We ambispectively (70 retrospective and 100 prospective) analyzed the data of men with biochemical recurrence post-RP and post-RT who were evaluated by 68Ga PSMA PET/CT at our institute. We aimed to assess the relationship between serum PSA levels and the probability of having a positive scan in patients with recurrent prostate cancer. RESULTS: The study included 170 men, all had adenocarcinoma of the prostate, 124/170 had previous RP and 46/170 had prior RT. The median serum PSA in the RP group was 1.8 ng/ml and 5.2 ng/ml in the RT group. In the post-RP cohort, the detection rate of 68Ga PSMA PET/CT was 39.3% for PSA 0.2 to <0.5 ng/ml, 47.3% for PSA 0.5 to <1 ng/ml, 68.4% for PSA 1 to <2 ng/ml and 93.1% for PSA ≥2 ng/ml. In the post-RT group, the detection rate was 88.8% for PSA 2 to <4 ng/ml and 100% for PSA ≥4 ng/ml. CONCLUSIONS: 68Ga PSMA PET/CT provides a novel imaging modality for the detection of prostate cancer recurrence and metastases at low posttreatment PSA levels, which may help in directing appropriate salvage treatments.

Gastric Mucosal Hypertrophy Masquerading as Metastasis From Neuroendocrine Tumor of the Pancreas Detected on 68Ga-DOTANOC PET/CT.

A 57-year-old man, on octreotide treatment for metastatic neuroendocrine tumor pancreas, was referred for whole-body Ga-DOTANOC PET/CT scan to evaluate treatment response. PET/CT scan revealed DOTANOC-avid lesion in the head of the pancreas with multiple tracer-avid soft tissue lesions in the liver, bilateral adrenal glands, and periportal lymph nodes. In addition, diffuse intense DOTANOC-avid mural thickening with intraluminal polypoidal mass formation was noted within the stomach causing significant luminal compromise, histopathological examination of which turned out be hypertrophic hypersecretory gastropathy. This case highlights the possibility of overexpression of somatostatin receptors in gastric hypertrophy, which has been little explored in literature.

18F-Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography/Magnetic Resonance Imaging in Neurosarcoidosis.

A 41-year-old lady presented with headache and ophthalmoplegia of the left eye for 1 week and underwent magnetic resonance imaging (MRI) of the brain, which showed homogeneously enhancing nodular thickening of meninges in the left anterior and middle cranial fossa with perilesional white matter edema of the left fronto-temporal lobes which appeared suspicious for neurosarcoidosis. She subsequently underwent 18F-fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG PET/CT) to determine the disease extent and to target the optimal biopsy site. Coregistration of 18F-FDG PET-CT brain to MRI was done for better characterization of the brain lesions.

Diffuse Pulmonary Metastases From Prostate Cancer on 68Ga PSMA PET/CT.

A 63-year-old man, recently diagnosed with carcinoma of the prostate (Gleason's score 4+4), with serum prostate-specific antigen 189.2 ng/mL, underwent Ga PSMA PET/CT scan for pretreatment staging. The study revealed abnormal tracer uptake in the prostatic bed region, the pelvic, abdominal, and mediastinal lymph nodes and diffuse metastases to the bilateral lungs. The lung metastasis was proved to be metastatic adenocarcinoma from analysis of bronchoalveolar lavage.

Uncommon Penio-Scrotal Metastases of Prostate Cancer Detected on 68Ga PSMA PET/CT.

A 68-year-old man, a known case of carcinoma prostate (Gleason score 4 + 4), status post transurethral resection of prostate cancer and radiotherapy, on hormonal treatment with rising prostate-specific antigen 9.0 ng/mL and penile swelling underwent Ga-PSMA PET/CT scan for metastatic workup and restaging. The study revealed abnormal tracer uptake in the prostatic bed region, the pelvic and inguinal lymph nodes, and metastases to the glans of penis and scrotum. The penile and scrotal lesion was proved to be metastatic adenocarcinoma from prostate on fine-needle aspiration cytology.

Mediastinal Duplication Cyst on 99mTc Pertechnetate Scan.

A 3-year-old boy presented with intermittent abdominal pain, melena, and anemia since 2 months. Upper gastrointestinal endoscopy did not reveal any significant abnormality. The child was then referred for Tc-pertechnetate scan to rule out the presence of ectopic functioning gastric mucosa. Tc-pertechnetate scan revealed abnormal tracer accumulation in the thoracic region, which persisted in the delayed images, suspicious for being ectopic gastric mucosa. Subsequently, ultrasound and contrast-enhanced CT (CECT) scans of the chest revealed a large multiseptate cystic lesion in the retrocardiac region, corresponding to the site of increased tracer uptake on Tc-pertechnetate scan.

Incidental Detection of Skeletal Metastases on 99mTc-DTPA Renography.

We present the case of a 53-year-old man with left hydroureteronephrosis who underwent Tc-DTPA renography for functional assessment of bilateral kidneys. Tc-DTPA renography of the patient showed diffusely increased extrarenal Tc-DTPA uptake in the visualized lumbosacral vertebrae and in the pelvic bones, on the blood flow and functional phase of the renography, which was suggestive of disseminated skeletal disease. Subsequent MRI lumbosacral spine and F-FDG PET/CT revealed extensive skeletal metastases corresponding to the increased extrarenal Tc-DTPA uptake in the lumbosacral vertebrae and the pelvic bones from primary left lung mitotic lesion.

Osteoid Osteoma Mimicking Inflammatory Synovitis.

Osteoid osteoma is a common benign bone tumor of unknown etiology affecting the young adult with characteristic clinical and radiographic presentation in its common locations. However, when it arises in unusual intra-articular locations diagnosis may be misleading, often mimicking other entities leading to delayed management. We present a case series of three cases with intra-articular osteoid osteoma that were diagnosed with the help of correlative imaging.

(11)C-Methionine positron emission tomography-computed tomography in localization of methoxyisobutyl isonitrile negative ectopic parathyroid adenoma.

Primary hyperparathyroidism is caused by parathyroid adenomas in 85% of the cases. Since parathyroid adenomas are known for their ectopic location, presurgical localization of the suspected site of adenoma is desirable. However, current imaging modalities are not always successful in localizing ectopic parathyroid adenomas. The aim of this case report is to show that (11)C-methionine positron emission tomography could accurately localize ectopic parathyroid adenomas in patients in whom conventional imaging had failed or is inconclusive.

Characterization of 'cold' vertebrae on 18F-FDG PET/CT.

INTRODUCTION: A photon-deficient ('cold') vertebra on fluorine-18 fluorodeoxyglucose (F-FDG) PET is a known entity and can arise as a result of varying etiologies. A proper interpretation of this observation is required to make an accurate diagnosis for appropriate management. METHODS: Twelve cases with 'cold' vertebrae on F-FDG PET/computed tomography (CT) were selected and analyzed from a population of 600 patients with a known malignancy who had undergone whole-body F-FDG PET/CT for staging, disease viability assessment, response to treatment, or suspected recurrence purposes. The patterns were studied and correlated with clinical history and the results of the low-dose CT performed with the PET scan for attenuation correction and anatomical localization. RESULTS: The most common cause for cold vertebrae was found to be postexternal radiotherapy, causing photopenia involving multiple vertebrae corresponding to the radiotherapy portals. Two other causes found in the study were the destruction of the vertebral marrow cavity by metastatic tumor cells and vertebral hemangioma. Characteristic features of 'cold' vertebrae have been described in the study with illustrations. CONCLUSION: Pattern recognition coupled with clinical history and CT correlation of 'cold' vertebrae on F-FDG PET/CT can help in diagnosing the correct underlying etiology, which can help in better management of the patients.