FDG PET in Neurological Manifestations of COVID-19.

ABSTRACT: Both the central and peripheral nervous systems can be affected in COVID-19. Although MRI is the primary investigative tool for neurological imaging, FDG PET may show additional areas of involvement in the brain in the form of regional hypometabolism or hypermetabolism, secondary to synaptic dysfunction and electrical or glial activation. We present a case series of 4 patients who had neurological symptoms attributable to COVID-19 infection with abnormalities in the brain FDG PET scan.

18F-FDG PET/CT and 99mTc-TRODAT Scan Findings in the Variants of Progressive Supranuclear Palsy and Correlation With Clinical Findings.

Aim: The aim of this study is to elucidate the patterns of characteristic hypometabolism on 18F-Fluoro Deoxy-glucose (18F-FDG) Positron Emission Tomography/Computed Tomography (PET/CT) in the variants of Progressive supranuclear palsy (PSP) and its correlation with their core clinical features. Material and Methods: A retrospective analysis of 88 subjects with clinically suspected PSP was done. An institutional informed consent to participate in the study was taken from all the subjects. All the subjects had undergone a prior 99mTechnetium labeled Tropane derivative of dopamine transporter Single Photon Emission Computed Tomography (99mTc TRODAT-1 SPECT) study and had abnormal scans to confirm degenerative parkinsonism. The subjects were clinically examined by the neurologists using the Progressive Supranuclear Palsy Rating Scale proposed by the Movement Disorder Society and were further clinically segregated into eight subtypes. All the included subjects further underwent a detailed clinical analysis to obtain their individual Schwab and England activities of daily living scale and Modified Hoehn and Yahr staging by a neurologist. All the subjects underwent 18F-FDG PET/CT scan after adequate preparation. The scans were analyzed both qualitatively (visually) and quantitatively using Statistical Parametric Mapping. Results: The frontal, limbic, and sensorimotor cortices represented the common areas of hypometabolism among all the subtypes of PSP. The subcortical regions showing the most significant hypometabolism were the thalami, mid-brain, nucleus accumbens, caudate, globus pallidus, and putamen in descending order. Multiple cortical and subcortical regions of hypometabolism were identified in different subtypes of PSP. Conclusion: The characteristic patterns of hypometabolism observed in the different subgroups were more apparent on quantification and based on visual analysis alone, it may not be possible to differentiate the different subtypes of PSP. A good correlation was seen between some of the core clinical features and hypometabolic clusters.

Lewy Body Dementia Associated with Anti-IgLON 5 Encephalitis Detected on 18F Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography and 99mTc-TRODAT Single-Photon Emission Computed Tomography/Computed Tomography.

We present a case of Anti-IgLON 5 encephalitis with Lewy body dementia. 18F fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) scan and 99 mTc-TRODAT-1 SPECT/CT scan were done. 99 mTc-TRODAT-1 scan findings revealed severely reduced concentration of dopamine transporter in bilateral basal ganglia, suggestive of a degenerative parkinsonian disorder. 18F-FDG PET scan findings were suggestive of moderate-to-severe hypometabolism in the bilateral parieto-temporal and bilateral occipital cortices including the primary visual cortices, supporting Lewy body spectrum disease with associated hypermetabolism in the bilateral sensorimotor cortices, bilateral basal ganglia, thalami, brain stem, and bilateral cerebellar hemispheres suggestive of inflammatory pathology.

Comprehensive Functional Evaluation of the Spectrum of Multi-System Atrophy with 18F-FDG PET/CT and 99mTc TRODAT-1 SPECT: 5 Year's Experience from a Tertiary Care Center.

AIM: To elucidate the patterns of characteristic hypometabolism on 18F- fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) in multisystem atrophy (MSA) and their correlation with the patterns of uptake on dopamine transporter imaging with 99mTc TRODAT-1 SPECT. MATERIAL AND METHODS: A retrospective analysis of 67 patients with clinically diagnosed MSA was performed. All the subjects underwent 99mTc TRODAT-1 SPECT and 18F-FDG PET/CT scanning on two separate days. The 99mTc-TRODAT-1 scans were analyzed visually for asymmetry and rostro-caudal gradient. The FDG uptake patterns were recorded, and areas of hypometabolism that were two standard deviations from the mean were considered abnormal. RESULTS: All the subjects had an abnormal pattern of FDG uptake on PET scan, both on a visual inspection and semiquantitative analysis. In MSA-P subjects (n = 29), diffuse predominant hypometabolism of the globus pallidus-putamen complex was noted, with relative sparing of the caudate nuclei. In MSA-C subjects (n = 25), characteristic hypometabolism was noted in the cerebellum and brainstem. In mixed subtypes (n = 13), variable involvement of the basal ganglia, cerebellum, and brainstem was noted with frontoparietal hypometabolism. A statistically significant difference between MSA-P and MSA-C for gradient reduction and asymmetry with gradient reduction was observed. CONCLUSION: Dopamine transporter imaging with 99mTc TRODAT-1 SPECT not only helps in confirmation of parkinsonian disorders but also demonstrates varying patterns of distribution in different subtypes of MSA. Characteristic patterns of hypometabolism in 18F-FDG PET may help in the differentiation of the subtypes of MSA in the presence of clinically overlapping symptoms.

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.

18F-Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography in Initial Diagnosis and Treatment Response Evaluation of New Onset Refractory Status Epilepticus.

New onset refractory status epilepticus (NORSE), is a rare, neurological condition characterised by prolonged periods of refractory epileptic seizure with no readily identifiable cause in otherwise healthy individuals. Anatomical imaging like MRI and serology is usually unremarkable. In patients who have underlying etiology as auto-immune encephalitis without any evidence of auto-antibodies FDG PET may help in early diagnosis and treatment response as it tends to accumulate in the neuronal tissue whenever there is increased blood flow, metabolic demand or increased electrical activity which reverts back with clinical recovery.

Spectrum of Frontotemporal Lobar Degeneration on 18F-FDG PET/CT Scan.

FTLD (Frontotemporal lobar degeneration) is a clinically and pathologically heterogeneous group of degenerative disorders, characterized by predominantly asymmetric degeneration of frontal and temporal lobes with selective neuronal loss and gliosis. The disease presents with variable degrees of impairment in behavior, language, executive control, and motor symptoms with progressive loss of cognition. On the basis of presenting clinical symptoms, FTLD is further divided into behavioral variant, nonfluent/agrammatic variant primary progressive aphasia (PPA), semantic variant PPA, logopenic variant PPA, progressive supranuclear palsy, and corticobasal ganglionic degeneration. Here we illustrate the utility of FDG PET with statistical parametric analysis for evaluation of these patients.

Semiquantitative Interpretation Criteria for Fluorodeoxyglucose-Positron Emission Tomography/Computed Tomography in Large-Vessel Vasculitis: Pattern Recognition and Correlation with Polymyalgia Rheumatica.

BACKGROUND: Fluorine-18-fluorodeoxyglucose (18F-FDG)-positron emission tomography/computed tomography (PET/CT) is emerging as a useful imaging modality in suspected large-vessel vasculitis (LVV), owing to its ability to accumulate at the sites of inflammation within the arterial walls. However, there remains scope for standardization of reporting criteria to ensure reproducibility. Recently, a semiquantitative scoring system called "total vascular score" (TVS) has been suggested as a method to standardize and harmonize FDG PET/CT evaluation in LVV patients. The purpose of this study was to assess the clinical utility of the proposed semiquantitative grading scale in LVV patients. MATERIALS AND METHODS: Patients presenting with clinical symptoms of vasculitis, who had undergone a baseline FDG-PET/CT were evaluated. 18F-FDG uptake in the major vessels was quantified with standardized uptake values (SUVsmax) using four-point scale by three independent nuclear physicians. TVS was calculated based on the calculation of the vascular uptake values with respect to mediastinal blood pool and liver uptake and the number of vessels involved. RESULTS: A total of 106 PET-positive patients (74 males and 32 females) were evaluated. The most frequently involved vessels were thoracic aorta >abdominal aorta >subclavian arteries with mean SUVmax values of 4.05, 3.12, and 2.70, respectively. Mean TVS was 13.18 ± 3.4 (range 03-19) among 276 involved vessels. TVS showed significant positive correlation with erythrocyte sedimentation rate (r = 0.82; P < 0.005). 18 patients showed periarticular FDG uptake, with shoulder joint being the most commonly involved joint. CONCLUSION: The simplified visual and semiquantitative grading scale for interpretation and reporting classification provides better objectivity in diagnosis, communication with referring clinicians, and planning in patients of LVV.

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.

Metabolic imaging patterns in posterior cortical atrophy and Lewy body dementia.

PURPOSE: To study the imaging patterns of Posterior cortical atrophy (PCA) and Dementia with Lewy bodies (DLB) on fluoro-deoxyglucose positron emission tomography computed tomography ([F]FDG PET/CT), identify areas of overlap and differences and to develop a prediction model to assist in diagnosis using univariate and multivariate analysis. METHODS: A retrospective analysis of 72 patients clinically suspected of having posterior dementia was done. All patients underwent [FF]FDG PET/CT of the brain and dopamine transporter imaging with [[Tc]TRODAT-1 SPECT scan on separate days. The patients were divided into PCA with normal TRODAT uptake (n=34) and DLB with abnormal TRODAT uptake (n=38). The FDG PET/CT uptake patterns were recorded and areas of significant hypometabolism by z score analysis were considered as abnormal. Receiver operator characteristics (ROC) curve analysis was used to determine cutoff z scores and binary logistic regression analysis was used to determine the Odds ratio of being in the predicted groups. RESULTS: Significantly hypometabolism was found in parieto-temporo-occipital association cortices and cingulate cortices in PCA patients. DLB patients showed significantly reduced uptake in the visual cortex. No significant difference was found between z score of occipital association cortex which showed hypometabolism in both groups. The cut-off z-score values derived from the ROC curve analysis were as follows- parietal association (cut-off-3, sensitivity-65.6%, specificity - 68.7%), temporal association (cut-off-2, sensitivity-78%, specificity-75%) and posterior cingulate (cut-off-0.5, sensitivity-93.7%, specificity-40.6%), their respective Odds ratio (with 95% confidence interval) for being in the PCA group as derived from univariate logistic regression were 3.66 (1.30-10.32), 10.71 (3.36-34.13) and 7.85 (1.57-39.17). The cut-off z score of primary visual cortex as derived from ROC curve was zero with sensitivity of 87.5%, specificity of 71.9%, and the Odds ratio for being the in the DLB group was 24.7 with 95% confidence interval of 5.99-101.85. CONCLUSION: [F]FDG PET may be useful as a non-invasive diagnostic modality in differentiating the two posterior cortical dementias, despite significant overlap. Primary visual cortical hypometabolism can serve as an independent diagnostic marker for DLB, even in the absence of TRODAT imaging.

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.

FDG PET/CT with SPM Analysis in Early Diagnosis of Clinically Suspected Osmotic Demyelination Syndrome with Non-contributory MRI.

Early diagnosis is imperative for adequate management of patients with osmotic demyelination syndrome (ODS), which is usually a result of rapid shifts of osmolality secondary to rapid correction of hyponatremia. Magnetic resonance imaging (MRI) with its special sequences is the investigation of choice for early detection of the osmotic changes in the brain. We report a case of clinically suspected ODS with noncontributory MRI and positive fluoro-2-deoxy-d-glucose positron emission tomography (FDG PET) scan with statistical parametric mapping (SPM) analysis, which localized the focal hypermetabolism in the basal ganglia, thalamus, pons, and cerebellum.

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.