FDG-PET Scans Research Articles

Analysis and Historical Evolution of Paediatric Bone Tumours: The Importance of Early Diagnosis in the Detection of Childhood Skeletal Malignancies

Even though children’s malignant bone tumours are rare, it is crucial to understand how to identify and stage them accurately to develop an appropriate treatment plan. Ewing’s sarcoma and osteosarcoma are the two main paediatric bone malignancies and require multidisciplinary treatment involving radiologists, orthopaedists, oncologists, pathologists, and paediatricians. These neoplasms may be associated with genetic syndromes but typically occur in patients with no known germline abnormalities. With a frequency of 4.4 per million, osteosarcoma is the most common malignant bone tumour in children. Ewing’s sarcoma has an incidence of 2.5 to 3 per million, making it the second most prevalent. Clinically, these neoplasms present with pain and inflammation in the bones and joints, nocturnal pain unresponsive to drug therapy, systemic symptoms such as fever or weight loss, and persistent symptoms—all of which should prompt clinicians to initiate further diagnostic investigations. The gold standard for diagnosis includes X-ray examination and MRI, which provide an accurate assessment of tumour extension into the medullary canal and surrounding soft tissues. Fluorine-18-labelled FDG-PET scans or fluoro-deoxyglucose positron emission tomography are valuable for evaluating tumour aggressiveness and excluding metastases. A biopsy is mandatory once all other diagnostic tests have been completed. Accurate diagnosis and timely referral to an experienced clinic are essential for ensuring prompt access to treatment and improving patient outcomes.

Exploring the Role of FDG PET CT Scan in Detecting High Grade Diffuse Large B-Cell Lymphoma

Introduction. Diffuse B-cell lymphoma (DLBCL) is the most common type of non-Hodgkin’s lymphoma. Currently, the standard method for evaluating patients at the initial stages of cancer diagnosis in Mashhad oncology centers involves computed tomography scans (CT scans), histopathological evaluation of tissue, bone marrow sampling, and cytogenetic studies, all of which are time-consuming and costly. It is worth mentioning that at present, the most recommended approach for determining lymphoma staging is the FDG-PET/CT scan, which combines labeled glucose with CT scan and offers a more accurate alternative. The objective of this study is to explore the potential of FDG-PET/CT scan as a tool for detecting high-grade lymphoma.Methods. In this study, patients with different types of DLBCL who underwent FDG-PET Scan for staging at Razavi Hospital, Mashhad, Iran between 2017 and 2021 were examined. The necessary clinical and paraclinical information, including the stage of the disease, the involved site at the time of diagnosis, the result of immunohistochemical examination, and the response to treatment were collected. FDG-PET Scan information including the extent of involvement and metabolic activity of the tumor before the start of treatment, pathological characteristics of the tumor, clinical behavior, and response to treatment in the form of response rate (RR), disease-free survival (DFS) and overall survival (OS) of the patients. Was also investigated. Aggressive histology in the present study was classified based on morphological characteristics and immunohistochemical staining, prognostic indicators, clinical behavior and response to treatment. Data were analyzed using SPSS software at a significance level of p<0.05.Results. Comparing the two groups of patients with high grade histology (n=12) and NOS (n=14), the results showed that SUV max values in patients with aggressive lymphoma were 27.5 ± 15.6 (median 25.6) and in patients with NOS lymphoma was 15.4 ± 9.8 (median 14.4) (p=0.01). The overall survival of patients in the aggressive group was 10 months and in the non-aggressive group was 24 months (p=0.002). Also, the cut — off -point of 21.1 for SUV max has a sensitivity of 66 % and a specificity of 72 % in differentiating aggressive from non-aggressive types.Conclusion. The results revealed that FDG PET CT Scan can provide valuable insights into differentiating lymphomas with a more aggressive type from their usual types, as those with heightened metabolic activity (SUVmax) are often indicative of aggressive behaviors.

Cross-modality PET image synthesis for Parkinson's Disease diagnosis: a leap from [18F]FDG to [11C]CFT.

Dopamine transporter [11C]CFT PET is highly effective for diagnosing Parkinson's Disease (PD), whereas it is not widely available in most hospitals. To develop a deep learning framework to synthesize [11C]CFT PET images from real [18F]FDG PET images and leverage their cross-modal correlation to distinguish PD from normal control (NC). We developed a deep learning framework to synthesize [11C]CFT PET images from real [18F]FDG PET images, and leveraged their cross-modal correlation to distinguish PD from NC. A total of 604 participants (274 with PD and 330 with NC) who underwent [11C]CFT and [18F]FDG PET scans were included. The quality of the synthetic [11C]CFT PET images was evaluated through quantitative comparison with the ground-truth images and radiologist visual assessment. The evaluations of PD diagnosis performance were conducted using biomarker-based quantitative analyses (using striatal binding ratios from synthetic [11C]CFT PET images) and the proposed PD classifier (incorporating both real [18F]FDG and synthetic [11C]CFT PET images). Visualization result shows that the synthetic [11C]CFT PET images resemble the real ones with no significant differences visible in the error maps. Quantitative evaluation demonstrated that synthetic [11C]CFT PET images exhibited a high peak signal-to-noise ratio (PSNR: 25.0-28.0) and structural similarity (SSIM: 0.87-0.96) across different unilateral striatal subregions. The radiologists achieved a diagnostic accuracy of 91.9% (± 2.02%) based on synthetic [11C]CFT PET images, while biomarker-based quantitative analysis of the posterior putamen yielded an AUC of 0.912 (95% CI, 0.889-0.936), and the proposed PD Classifier achieved an AUC of 0.937 (95% CI, 0.916-0.957). By bridging the gap between [18F]FDG and [11C]CFT, our deep learning framework can significantly enhance PD diagnosis without the need for [11C]CFT tracers, thereby expanding the reach of advanced diagnostic tools to clinical settings where [11C]CFT PET imaging is inaccessible.

Urinary formic acid is associated with cerebral amyloid deposition and glucose metabolism in memory clinic patients.

Urinary formic acid (FA) has been reported to be a biomarker for Alzheimer's disease (AD). However, the association between FA and pathological changes in memory clinic patients is currently unclear. This study aims to investigate associations between FA and pathological changes across different cognitive statuses in memory clinic patients. A cohort of patients with mild cognitive impairment (MCI-Aβ- n = 37, MCI-Aβ+ n = 33), AD dementia (n = 39), and cognitively normal subjects (CN-Aβ- n = 98, CN-Aβ+ n = 50) were included. Comprehensive neuropsychological assessment, urinary FA, AD-related plasma biomarkers, MRI scans, [18F]-flurbetapir and [18F]-FDG PET scan data were collected from all participants. Urinary FA levels were higher in patients with MCI and AD than in CN subjects and higher in Aβ+ (CN- Aβ+, MCI-Aβ+, AD dementia) subjects than in Aβ-subjects (CN- Aβ-, MCI-Aβ-). Urinary FA was positively associated with cerebral Aβ deposition and negatively associated with glucose metabolism, both at the global level and in multiple regions of interest cortical regions in participants with different cognitive statuses. Additionally, urinary FA levels were positively correlated with the severity of white matter hyperintensities and hippocampal atrophy. Urinary FA combined with age, Mini-Mental State Examination, plasma p-tau181, and neurofilament light chain could be used to predict Aβ deposition in the brain. Urinary FA is associated with brain pathological changes in memory clinic patients, including cerebral Aβ deposition, glucose metabolism, white matter hyperintensities, and hippocampal atrophy. It could be used as a biomarker for the early diagnosis of AD and predicting Aβ deposition.

A case of Erdheim-Chester disease-a mimicker of IgG4-related disease and large vessel vasculitis.

The patient was a 57-year-old man who developed bilateral thigh pain and chest tightness one year ago. Chest CT scan showed reticular shadows, thickened interlobular septa in both lung fields, and pericardial effusion. Three months ago, his symptoms worsened. A contrast CT scan revealed increased pericardial effusion, multiple masses in the right atrium, soft tissue shadows suggestive of retroperitoneal fibrosis, and soft tissue shadows around the thoracic and abdominal aorta. He visited our hospital, suspecting IgG4-related disease (IgG4-RD) or large vessel vasculitis (LVV). Based on the involvement of various organs and bilateral thigh pain, Erdheim-Chester disease (ECD) was suspected, and an FDG-PET scan was performed. In addition to increased accumulation around the right ventricle, right coronary artery, and aorta, increased accumulation was confirmed in the distal femurs and proximal tibias on both sides, strongly suggesting ECD. A bone biopsy confirmed the diagnosis of ECD, showing bone fibrosis with CD68-positive and CD1a-negative foam cell infiltration, which is a characteristic of ECD. ECD is an extremely rare form of non-Langerhans cell histiocytosis. ECD affects a wide variety of organs, and its imaging findings can sometimes resemble those of IgG4-related disease or LVV. However, bone lesions are characteristic of ECD and are a key finding for its diagnosis. When systemic organ lesions, including bone lesions, are present, ECD should be included in the differential diagnosis, and PET-CT should be considered.

A Case Report of Neuroleukemiosis Detected on FDG PET Scan in a Patient of Mixed Phenotype Acute Leukemia Post Bone Marrow Transplantation in Remission

A Case Report of Neuroleukemiosis Detected on FDG PET Scan in a Patient of Mixed Phenotype Acute Leukemia Post Bone Marrow Transplantation in Remission

Interpretable survival network for progression risk analysis of multimodality imaging biomarkers in poor-prognosis head and neck cancers

This study explores the predictive utility of multi-time point, multi-modality quantitative imaging biomarkers (QIBs) and clinical factors in patients with poor-prognosis head and neck cancers (HNCs) using interpretable machine learning. We examined 93 patients with p16 + oropharyngeal squamous cell carcinoma or locally advanced p16- HNCs enrolled in a phase II adaptive radiation dose escalation trial. FDG-PET and multiparametric MRI scans were conducted before radiation therapy and at the 10th fraction (2 weeks). A survival network analyzed MRI and PET-derived biomarkers such as gross tumor volume (GTV), blood volume (BV), and metabolic tumor volume (MTV50), along with clinical factors to predict local (LF) and distant failures (DF). Feature attributions and interactions were assessed using Expected Gradients (EG) and Expected Hessian (EH). Through rigorous cross-validation, the model for predicting LF, incorporating biomarkers like p16 status and radiation boost, achieved a c-index of 0.758. Similarly, the DF prediction model showed a c-index of 0.695. The analysis of feature attributions and interactions enhanced understanding of important features and complex factor interplays, potentially guiding more personalized and intensified treatment approaches for HNC patients.

Cortical hypometabolism as a predictor of intermittent theta burst stimulation response in treatment-resistant depression patients: An open-label study.

Intermittent theta burst stimulation (iTBS) is an accepted and approved brain stimulation technique to treat patients with treatment-resistant depression. Using neuroimaging, this open-label study aimed to predict the response by observing glucose metabolism with the help of 18-FDG PET scan. A total of 25 treatment-resistant depression patients received 15 sessions of iTBS on the left dorsolateral prefrontal cortex. Two FDG-PET scans were done for all the patients. Fifty-six percent of patients responded to treatment with iTBS. We found that there was hypometabolism in left and right prefrontal lateral regions, left and right inferior parietal regions, and left prefrontal medial regions at baseline but no statistically significant difference in the metabolism between responders and nonresponders. We did not find any statistically significant difference in the metabolism between responders and nonresponders in any brain regions at T0 as well as T1. Further large-scale studies are required.

Divergent neurodegenerative patterns: Comparison of [18F] fluorodeoxyglucose-PET- and MRI-based Alzheimer's disease subtypes.

[18F] fluorodeoxyglucose (FDG)-PET and MRI are key imaging markers for neurodegeneration in Alzheimer's disease. It has been well established that parieto-temporal hypometabolism on FDG-PET is closely associated with medial temporal atrophy on MRI in Alzheimer's disease. Substantial biological heterogeneity, expressed as distinct subtypes of hypometabolism or atrophy patterns, has been previously described in Alzheimer's disease using data-driven and hypothesis-driven methods. However, the link between these two imaging modalities has not yet been explored in the context of Alzheimer's disease subtypes. To investigate this link, the current study utilized FDG-PET and MRI scans from 180 amyloid-beta positive Alzheimer's disease dementia patients, 339 amyloid-beta positive mild cognitive impairment and 176 amyloid-beta negative cognitively normal controls from the Alzheimer's Disease Neuroimaging Initiative. Random forest hierarchical clustering, a data-driven model for identifying subtypes, was implemented in the two modalities: one with standard uptake value ratios and the other with grey matter volumes. Five hypometabolism- and atrophy-based subtypes were identified, exhibiting both cortical-predominant and limbic-predominant patterns although with differing percentages and clinical presentations. Three cortical-predominant hypometabolism subtypes found were Cortical Predominant (32%), Cortical Predominant+ (11%) and Cortical Predominant posterior (8%), and two limbic-predominant hypometabolism subtypes found were Limbic Predominant (36%) and Limbic Predominant frontal (13%). In addition, little atrophy (minimal) and widespread (diffuse) neurodegeneration subtypes were observed from the MRI data. The five atrophy subtypes found were Cortical Predominant (19%), Limbic Predominant (27%), Diffuse (29%), Diffuse+ (6%) and Minimal (19%). Inter-modality comparisons showed that all FDG-PET subtypes displayed medial temporal atrophy, whereas the distinct MRI subtypes showed topographically similar hypometabolic patterns. Further, allocations of FDG-PET and MRI subtypes were not consistent when compared at an individual level. Additional analysis comparing the data-driven clustering model with prior hypothesis-driven methods showed only partial agreement between these subtyping methods. FDG-PET subtypes had greater differences between limbic-predominant and cortical-predominant patterns, and MRI subtypes had greater differences in severity of atrophy. In conclusion, this study highlighted that Alzheimer's disease subtypes identified using both FDG-PET and MRI capture distinct pathways showing cortical versus limbic predominance of neurodegeneration. However, the subtypes do not share a bidirectional relationship between modalities and are thus not interchangeable.

Longitudinal FDG-PET Radiomics for Early Prediction of Treatment Response to Chemoradiation in Locally Advanced Cervical Cancer: A Pilot Study.

Objectives: This study aimed to assess the capacity of longitudinal FDG-PET radiomics for early distinguishing between locally advanced cervical cancer (LACC) patients who responded to treatment and those who did not. Methods: FDG-PET scans were obtained before and midway through concurrent chemoradiation for a study cohort of patients with LACC. Radiomics features related to image textures were extracted from the primary tumor volumes and stratified for relevance to treatment response status with the aid of random forest recursive feature elimination. Predictive models based on the k-nearest neighbors time series classifier were developed using the top-selected features to differentiate between responders and non-responders. The performance of the developed models was evaluated using receiver operating characteristic (ROC) curve analysis and n-fold cross-validation. Results: The top radiomics features extracted from scans taken midway through treatment showed significant differences between the two responder groups (p-values < 0.0005). In contrast, those from pretreatment scans did not exhibit significant differences. The AUC of the mean ROC curve for the predictive model based on the top features from pretreatment scans was 0.8529, while it reached 0.9420 for those derived midway through treatment scans. Conclusions: The study highlights the potential of longitudinal FDG-PET radiomics extracted midway through treatment for predicting response to chemoradiation in LACC patients and emphasizes that interim PET scans could be crucial in personalized medicine, ultimately enhancing therapeutic outcomes for LACC.

Agreement between Cerebrospinal Fluid Biomarkers, Brain 18-Fluorodeoxyglucose PET, and Clinical Diagnosis in Older Adults with Cognitive Impairment.

Background: Clinical practice has advanced toward a combined diagnostic approach that involves clinical criteria and biological markers for Alzheimer's disease (AD) and other dementias. Objective: To establish the level of diagnostic agreement between an initial clinical diagnosis and cerebrospinal fluid (CSF) and [18F]-fluorodeoxyglucose (FDG)-positron emission tomography (PET) biomarkers in a cohort of patients from a memory clinic. Methods: This is a observational, retrospective, cohort study conducted at an outpatient memory clinic. Between July 2018 and September 2023, data from adults' ≥ 55 years with a mild cognitive impairment or dementia diagnosis without etiological diagnosis were obtained, complemented with the evaluation of biomarkers in CSF and [18F] FDG-PET biomarker assessment were included. Kappa coefficients (κ) were used to establish the level of agreement between CSF and [18F] FDG-PET results. Results: Seventy-seven patients had an available [18F] FDG-PET scan, and 25 (32.5%) had both biomarkers. We observed a fair-to-moderate diagnostic agreement between patients' initial and their final diagnosis in the presence of CSF (κ = 0.233, 95% confidence interval [CI]: -0.099-0.566) and [18F] FDG-PET (κ = 0.451, 95% CI: 0.277-0.625, p < 0.001) results. The Kappa value for diagnostic concordance between [18F] FDG-PET and CSF to differentiate between AD and other dementias was 0.733 (95% CI: 0.425-1.000, p < 0.005). Conclusion: This study demonstrates good agreement between the CSF and FDG-PET biomarkers to differentiate AD from other dementias. (Rev Invest Clin. 2024;76(5):230-7).

Recurrence patterns in differentiated thyroid cancer (DTC) following adjuvant radioiodine therapy.

With an increasing incidence of differentiated thyroid cancer (DTC) diagnosis, questions emerge about the optimal duration of follow-up for detecting recurrent disease and its outcomes. The objective of this retrospective research was to assess the clinical course of differentiated thyroid cancer after radioiodine adjuvant treatment in patients monitored over an extended period. Special attention was paid to the analysis of the time from treatment to recurrence. We also assessed patient outcomes after recurrence. A total of 650 patients with DTC after total/near-total thyroidectomy and adjuvant radioiodine post-recombinant human thyrotropin (post-rhTSH) stimulation were evaluated. All patients were followed up with neck ultrasound, serum thyroid-stimulating hormone (TSH), thyroglobulin (Tg), and antithyroglobulin antibody (anti-Tg) measurements at intervals of 6 to 18 months. Only structural recurrences were considered. They were defined as locoregional recurrence confirmed by biopsy or distant metastases [confirmed by computed tomography (CT) or magnetic resonance imaging (MRI), or abnormal foci on radioiodine scintigraphy or 18F-gluorodeoxyglucose positron emission tomography [18 F] FDG-PET scan], regardless of thyroglobulin (Tg) or anti-Tg levels. The median follow-up was 12 years (5-15.5). Structural recurrence was observed in 47 out of 650 patients (7%). All but 3 locoregional recurrences were suitable for surgery. The median time to structural recurrence was 16 months, with only 9 (1.4%) patients presenting with recurrence after more than 60 months. At the time of the database closure, 601 patients (92%) had an excellent response, including 20 out of 47 (42%) patients with structural recurrence. Eighty-one out of 650 patients had died (12.5%) before the database closure. The median age at the last follow-up of the patients who died was 72 years (range 20-88). A second recurrence was diagnosed in 10 out of 650 patients (1.5%), corresponding to 21% (10 out of 47) of patients who had already experienced a recurrence. The median time from radioiodine (RAI) therapy to the second structural recurrence was 108 months. Structural recurrences in DTC are uncommon, with most patients showing a favourable response to treatment. Improved understanding of recurrence timing may define the duration of patient surveillance at reference centres that can be safely discontinued after 5 years in low- and intermediate-risk groups, as indicated in our study.

Regional differences in glucose metabolic decline and tau deposition in the Alzheimer's continuum brain.

Alzheimer's disease (AD) is characterized by the accumulation of amyloid-β and tau proteins, leading to neurofibrillary tangles. A biomarker-based diagnostic method called the ATN system categorizes AD pathology into amyloid-β (A), tau (T), and neurodegeneration (N). The relationship between regional tau deposition and reduced glucose metabolism in the preclinical AD stage is not well understood. We presented voxel-by-voxel metabolic/tau deposition ratio (MTR) images to investigate the effects of tau deposition on metabolism in AD brains on a stage-by-stage basis. We selected 174 subjects who underwent 3D-MRI, FDG-PET, amyloid PET, and tau PET scans. MTR images were created by normalizing FDG-PET toMK6240 PET images. Voxel-wise comparisons among 63 cognitively normal amyloid-negative (CNA) subjects, 49 subjects with AD dementia (ADD), 23 subjects with mild cognitive impairment due to AD (MCA), and 39 preclinical AD (PRC) subjects were conducted. There was reduced glucose metabolism in ADD and MCA groups compared to CNA, predominantly in parietotemporal areas. Tau deposition was observed in wider areas in ADD and restricted to the medial temporal lobes in MCA. MTR exhibited significant reductions in broader regions in ADD and MCA, indicating simultaneous glucose metabolism decrease and tau deposition. At the MCA and PRC stages, glucose metabolism impairment and tau deposition were shown in separate regions by FDG PET and tau PET, respectively, while MTR images showed impairment in both regions. Our findings suggest that MTR imaging provides insights into AD pathophysiology by simultaneously assessing glucose metabolism and tau deposition. In the early stage of the AD continuum (MCA and PRC), metabolic decline and tau deposition occur independently in different brain regions.

Persistent dysfunctions of brain metabolic connectivity in long-covid with cognitive symptoms.

Our study examines brain metabolic connectivity in SARS-CoV-2 survivors during the acute-subacute and chronic phases, aiming to elucidate the mechanisms underlying the persistence of neurological symptoms in long-COVID patients. We perfomed a cross-sectional study including 44 patients (pts) with neurological symptoms who underwent FDG-PET scans, and classified to timing infection as follows: acute (7 pts), subacute (17 pts), long-term (20 pts) phases. Interregional correlation analysis (IRCA) and ROI-based IRCA were applied on FDG-PET data to extract metabolic connectivity in resting state networks (ADMN, PDMN, EXN, ATTN, LIN, ASN) of neuro-COVID pts in acute/subacute and long-term groups compared with healthy controls (HCs). Univariate approach was used to investigate metabolic alterations from the acute to sub-acute and long-term phase. The acute/subacute phase was characterized by hyperconnectivity in EXN and ATTN networks; the same networks showed hypoconnectivity in the chronic phase. EXN and ATTN hypoconnectivity was consistent with clinical findings in long-COVID patients, e.g. altered performances in neuropsychological tests of executive and attention domains. The ASN and LIN presented hyperconnectivity in acute/subacute phase and normalized in long-term phase. The ADMN and PDMN presented a preseverved connectivity. Univariate analysis showed hypometabolism in fronto-insular cortex in acute phase, which reduced in sub-acute phase and disappeared in long-term phase. A compensatory EXN and ATTN hyperconnectivity was found in the acute/subacute phase and hypoconnectivity in long-term. Hypoconnectivity and absence of hypometabolism suggest that connectivity derangement in frontal networks could be related to protraction of neurological symptoms in long-term COVID patients.

18F]FDG PET for mapping the cerebral glucose metabolic characteristics of drug-sensitive and drug-resistant epilepsy in pediatric patients.

This study aimed to investigate [18F]fluorodeoxyglucose positron emission tomography ([18F]FDG PET) mapping for cerebral glucose metabolism in drug-sensitive and drug-resistant pediatric epilepsy patients. This retrospective study enrolled 40 patients and 25 controls. Patients were categorized into drug-sensitive epilepsy (n = 22) and drug-resistant epilepsy (n = 18) according to the seizure frequency at follow-up. All patients underwent two [18F]FDG PET scans separated by a minimum of one year. Absolute asymmetry index (|AI|) was calculated for assessing metabolic differences and changes in epileptic foci. Statistical Parametric Mapping (SPM) was utilized to reveal voxel-wise metabolic characteristics and alterations throughout the brain. Network analysis based on graph theory was used to investigate network-level differences between the two patient groups. The drug-sensitive group showed a lower |AI| at both baseline (P = 0.038) and follow-up (P = 0.003) PET scans than the drug-resistant group. |AI| decreased in the drug-sensitive group and increased in the drug-resistant group across scans, but these trends were not statistically significant (P = 0.240 and P = 0.450, respectively). Both groups exhibited hypometabolism at baseline. The drug-sensitive group showed less hypometabolic brain regions than the drug-resistant group. The drug-sensitive maintained stable level of hypometabolism between the two scans, whereas the drug-resistant group showed an increasing hypometabolism. Network analysis demonstrated that the drug-sensitive group had a higher global efficiency, average degree, and clustering, along with a shorter characteristic path length compared to the drug-resistant group. For the first time, this study revealed in vivo cerebral glucose metabolic pattern of nonsurgical pediatric epilepsy patients treated by antiepileptic drugs. Especially, drug-resistant epilepsy patients represented significantly extensive and progressive hypometabolism with inefficient brain network connectivity compared with drug-sensitive epilepsy. [18F]FDG PET imaging may be a potential visual approach for theranostics of epilepsy patients.

8465 Diagnostic Conundrum: The Mystery of Metastatic Papillary Thyroid Cancer with Persistently Elusive Thyroglobulin

Abstract Disclosure: P. Vemparala: None. M. Bollineni: None. Introduction- Among endocrine malignancies, differentiated thyroid cancers account for the majority with most of them boasting a favorable prognosis. Thyroglobulin, a pivotal biochemical marker, aids in detecting recurrence or persistent disease when combined with neck ultrasound, I-131 scintigraphy, and FDG PET scans. Anti-thyroglobulin antibodies, found in a quarter of cases, can falsely lower serum thyroglobulin levels in immunometric assays. Our intriguing case features a patient with metastatic papillary thyroid cancer, yet thyroglobulin levels persistently eluded detection. CASE PRESENTATION- A 33-year-old female presented initially to an outside facility with neck swelling, leading to a diagnosis of a 4 x 3 cm papillary thyroid cancer (PTC) in the right lobe and a 0.5 x 0.5 cm focus of PTC in the left lobe, accompanied by capsular extension, malignant cells in the left lobe margin, and lymphovascular invasion. After total thyroidectomy and lymph node exploration, radioactive iodine scan detected disease in right-sided lymph nodes, treated subsequently with radioactive iodine ablation. Two years later, she presented to our clinic with neck swelling, voice changes, and fatigue. Thyroglobulin level was measured which returned at &amp;lt;0.1 ng/ml, however thyroglobulin antibodies were elevated at 292 IU/ml, albeit decreased from a value of 431.5 IU/ml at initial diagnosis. Elevated thyroglobulin antibodies complicated interpretation, prompting liquid chromatography-mass spectrometry (LC-MS) for accurate measurement of thyroglobulin, which returned at &amp;lt;0.5 ng/ml. Ultrasound indicated metastatic disease in right cervical lymph nodes, confirmed by fine needle aspiration. In-office ultrasound-guided FNA of additional nodes validated metastasis. Modified radical neck dissection revealed metastatic PTC in 7 out of 34 lymph nodes. Surprisingly, thyroglobulin levels remained &amp;lt;0.5 ng/ml, pre- and post-operatively. Referred for radioactive iodine ablation, her complex journey underscored the challenges in monitoring thyroid cancer recurrence or persistent disease with thyroglobulin levels even by methods such as mass spectrometry. Conclusion- Key learnings from this case highlight the importance of cognizance in utilizing thyroglobulin levels to guide adjuvant therapy decisions and for postoperative monitoring in high risk patients, as low levels do not rule out recurrence or persistence. Anti-thyroglobulin antibodies pose challenges, necessitating techniques like LC-MS. Finally, recognizing “nonsecretor” thyroid cancers, an aggressive subgroup with poorer prognosis, is vital as they often present with low or undetectable thyroglobulin levels. Presentation: 6/2/2024

9183 Pituitary Metastasis Of Lung Adenocarcinoma Presenting As Anterior Pituitary Dysfunction

Abstract Disclosure: O. faour: None. M. Kinaan: None. S.K. Suryanarayanan: None. Introduction: The pituitary should not be overlooked as a site for metastasis and can be the first presentation of neoplastic disease in some patients. Most common presenting symptoms: headache, ophthalmoplegia, visual field defect and Arginine Vasopressin Deficiency (AVP-D). We present a case of pituitary metastasis of lung adenocarcinoma presenting as anterior Pituitary dysfunction that also showed partial AVP-D unmasked after starting steroids. Case Description: A 63-year-old male with history of tobacco use, COPD, and hypertension presented with syncope. He reported a 30lbs weight loss within prior 2 months, low energy, increased thirst, and polyuria. Physical exam was significant for cachexia, normal visual field on confrontation, and vital signs of BP 100/61, HR 83, and Weighing 180 lbs. Since he had syncope, Cortisol checked was undetectable and Free T4 was low, He was started on hydrocortisone and levothyroxine. CTA chest revealed a right hilar mass measuring 2.7 x 3 cm. Endobronchial biopsy was consistent with lung adenocarcinoma. MRI of pituitary gland revealed solid hypointense lesion with glandular thickening and diffuse heterogeneity involving most of the pituitary gland measuring up to 16 mm. No cavernous sinus invasion. Pituitary infundibulum showed diffuse thickening and enhancement of the pituitary stalk throughout with Intact posterior pituitary bright spot. Labs showed low LH, cortisol, ACTH, GH, TSH, and ADH. Initially, the patient was able to maintain a euvolemic status through increased water intake; however, he was later found to have partial central AVP-D when steroids were introduced. He responded to the use of Desmopressin, developed hyponatremia after 3 doses. He was started on a combination of carboplatin/pemetrexed/pembrolizumab but had no response and was transferred to palliative care/hospice and passed away within 7months after diagnosis.Discussion:Pituitary metastasis is rare and most commonly occurs in lung and breast cancers. Unfortunately, they are associated with poor prognosis. MRI findings of loss of posterior pituitary bright spot, thickening of the stalk, and dumbbell shape can be helpful in distinguishing between primary pituitary tumors and metastases. PET-FDG scan has limited value. Pituitary metastasis commonly presents with posterior pituitary dysfunction due to direct blood supply. Unmasking or worsening of AVP-D can happen with steroid replacement in patients requiring initiation or intensification of Desmopressin therapy. Treatment involves combination of surgery, radiation therapy, and systemic treatment for the primary cancer which can improve symptoms only but does not improve mortality. Presentation: 6/1/2024

12459 Exceptional Response To A Single Dose Of Pembrolizumab As Salvage Therapy In A Patient With Metastatic Adrenocortical Carcinoma (ACC)

Abstract Disclosure: L. Branchaud-Croisetière: None. J. Castilloux: None. E. Turcotte: None. A. Bégin: None. M. St-Jean: Advisory Board Member; Self; GlaxoSmithKline, HRA Pharmaceuticals. Research Investigator; Self; AstraZeneca, Novo Nordisk, Spruce Biosciences. Speaker; Self; GlaxoSmithKline, Recordati Rare Diseases. In advanced ACC, limited effective treatment options are available beyond mitotane and cytotoxic chemotherapy. PD-L1 blockade has shown promising results in small numbers of advanced ACC. In ACC, the reported partial response rate to pembrolizumab is around 25%.[1] Only one case of a significant partial response to a single dose of Pembrolizumab as salvage therapy for metastatic ACC was previously published.[1] In April 2023, a 19-year-old woman presented with severe hypertension, hypokalemia and clinical signs of Cushing syndrome (CS). Thoraco-abdominal scan revealed a left-sided cluster of confluent adrenal masses (7.3 x 14.4 x 11.4 cm), a left cortical renal lesion (2.8x2x2.1cm), a right ovarian teratoma (7.9 x 7.8x7.9 cm) and at least 25 pulmonary micronodules. FDG-PET SCAN revealed a significant hypermetabolism of the left adrenal lesions (SUV 18.6), ovarian teratoma (SUV 5.5) and pulmonary micronodules (SUV 1.1-2). Cortisol and androgens secretion was confirmed biochemically. Initially, she was not candidate for a debulking surgery because the tumor was surrounding the aorta, and mesenteric arteries. Hypertension and hypokalemia were treated with spironolactone, amlodipine, amiloride and irbesartan. Cushing syndrome was treated with metyrapone. In April 2023, Etoposide-Doxorubicine-Cisplatin (EDP) was administered in combination with Mitotane (max: 8g/day). After 6 cycles of EDP-M the disease regressed slightly but was considered stable based on RECIST criteria. After 8 cycles, the follow-up imaging showed a progression of the adrenal lesion (9.2x18.2cm) but stable pulmonary micronodules. A biopsy of the adrenal lesion, for therapeutic purpose, revealed microsatellite stability (MSS). The patient refused germinal genetic testing. It was decided in multidisciplinary tumor board to try Pembrolizumab. In December 2023, she received one cycle of Pembrolizumab (140mg), but the treatment was complicated by grade 4 immune-mediated hepatitis. A few weeks following Pembrolizumab she completely normalized her blood pressure and hypokalemia despite cessation of all her anti-hypertensive drugs. Pembrolizumab and Mitotane were stopped and hepatitis completely resolved after two months of Mycophenolate Mofetil and ongoing decreasing dose of prednisone. In March 2024, CT scan showed a 60% regression of the adrenal mass (4.1 x 7.2 cm), stability of the renal lesion and ovarian teratoma and complete resolution of the pulmonary micronodules. We suspect an ongoing effect of immunotherapy and Mitotane, since Mitotane levels were still in the therapeutic range (15.1 mg/L) six weeks following cessation. Mitotane was resumed in March 2024. The patient will potentially have a resection of the left adrenal lesion in the next month. This is second published case of a significant response to Pembrolizumab as second-line therapy for advanced ACC. [1] Raj Net al. J Clin Oncol. 2020 Presentation: 6/1/2024

Automated deep learning segmentation of cardiac inflammatory FDG PET

BackgroundFluorodeoxyglucose positron emission tomography (FDG PET) with suppression of myocardial glucose utilization plays a pivotal role in diagnosing cardiac sarcoidosis. Reorientation of images to match perfusion datasets and myocardial segmentation enables consistent image scaling and quantification. However, such manual tasks are cumbersome. We developed a 3D U-Net deep-learning (DL) algorithm for automated myocardial segmentation in cardiac sarcoidosis FDG PET. MethodsThe DL model was trained on FDG PET scans from 316 patients with left ventricular contours derived from paired perfusion datasets. Qualitative analysis of clinical readability was performed to compare DL segmentation with the current automated method on a 50-patient test subset. Additionally, left ventricle displacement and angulation, as well as SUVmax sampling were compared with inter-user reproducibility results. A hybrid workflow was also investigated to accelerate study processing time. ResultsDL segmentation enhanced readability scores in over 90% of cases compared with the standard segmentation currently used in the software. DL segmentation performed similar to a trained technologist, surpassing standard segmentation for left ventricle displacement and angulation, as well as correlation of SUVmax. Using the DL segmentation as initial placement for manual segmentation significantly decreased the processing time. ConclusionA novel DL-based automated segmentation tool markedly improves processing of cardiac sarcoidosis FDG PET. This tool yields optimized splash display of sarcoidosis FDG PET datasets with no user input and offers significant processing time improvement for manual segmentation of such datasets.

Long-term trends in total administered radiation dose from brain [18F]FDG-PET in children with drug-resistant epilepsy

PurposeTo assess the trends in administered 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) doses, computed tomography (CT) radiation doses, and image quality over the last 15 years in children with drug-resistant epilepsy (DRE) undergoing hybrid positron emission tomography (PET) brain scans.MethodsWe retrospectively analyzed data from children with DRE who had [18F]FDG-PET/CT or magnetic resonance scans for presurgical evaluation between 2005 and 2021. We evaluated changes in injected [18F]FDG doses, administered activity per body weight, CT dose index volume (CTDIvol), and dose length product (DLP). PET image quality was assessed visually by four trained raters. Conversely, CT image quality was measured using region-of-interest analysis, normalized by signal-to-noise (SNR) and contrast-to-noise ratio (CNR).ResultsWe included 55 children (30 male, mean age: 9 ± 6 years) who underwent 61 [18F]FDG-PET scans (71% as PET/CT). Annually, the injected [18F]FDG dose decreased by ~ 1% (95% CI: 0.92%-0.98%, p < 0.001), with no significant changes in administered activity per body weight (p = 0.51). CTDIvol and DLP decreased annually by 16% (95% CI: 9%-23%) and 15% (95% CI: 8%-21%, both p < 0.001), respectively. PET image quality improved by 9% year-over-year (95% CI: 6%-13%, p < 0.001), while CT-associated SNR and CNR decreased annually by 7% (95% CI: 3%-11%, p = 0.001) and 6% (95% CI: 2%-10%, p = 0.008), respectively.ConclusionOur findings indicate stability in [18F]FDG administered activity per body weight alongside improvements in PET image quality. Conversely, CT-associated radiation doses reduced. These results reaffirm [18F]FDG-PET as an increasingly safer and higher-resolution auxiliary imaging modality for children with DRE. These improvements, driven by technological advancements, may enhance the diagnostic precision and patient outcomes in pediatric epilepsy surgery.