Fluorodeoxyglucose Research Articles

Relationships between cerebral tau and glucose metabolism in cognitively normal older adults

AbstractBackgroundAlzheimer’s disease (AD) is characterised by the accumulation of amyloid‐β and tau in the brain and subsequent neurodegeneration. The relationship between tau accumulation and glucose metabolism has been elucidated in AD, however the relationship between the two in the early stages of the AD trajectory remains elusive. Here, we examine this relationship using fluorodeoxyglucose (FDG) and flortaucipir (FTP) positron emission tomography (PET) in a cohort of cognitively normal older adults.Method72 cognitively normal participants (mean±SD age 78.7±6.3 years old) were recruited through the Harvard Ageing Brain Study and had available FDG‐PET, FTP‐PET, and structural MRI scans. Region of interest analysis was utilised to determine the regional uptake of each PET tracer. 40 participants were split into high‐tau and low‐tau groups based on the highest 20 and lowest 20 FTP uptake values from the medial temporal lobe excluding the hippocampus (MTL (no hippocampus)). FDG uptake was compared between high‐tau and low‐tau groups, while correlations between FDG and FTP uptake were examined.ResultGlucose metabolism was significantly higher in the low‐tau group than the high‐tau group in the whole brain (p = 0.023), frontal lobe (p = 0.028), temporal lobe (p = 0.014), parietal lobe (p = 0.027), MTL (p = 0.01), MTL (no hippocampus) (p = 0.002), anterior cingulate cortex (p = 0.045), and posterior cingulate cortex (p = 0.023). Significant negative correlations were found between FTP uptake in the MTL (no hippocampus) and FDG uptake in the whole brain (r = ‐0.317,p = 0.046), temporal lobe (r = ‐0.383,p = 0.015), parietal lobe (r = ‐0.316,p = 0.047), MTL (r = ‐0.437, p = 0.005), MTL (no hippocampus) (r = ‐0.444,p = 0.004), anterior cingulate (r = ‐0.320,p = 0.044), and posterior cingulate (r = ‐0.361,p = 0.022). FTP uptake in the temporal lobe negatively correlated with FDG in the temporal lobe (r = ‐0.326, p = 0.04) and MTL (no hippocampus) (r = ‐0.337,p = 0.034).ConclusionHigh tau levels in the MTL was associated with hypometabolism in cognitively normal older adults, suggesting that tau accumulation may cause decreased glucose metabolism without inducing cognitive deficits. Furthermore, negative correlations between FDG and FTP uptake highlight the link between tau accumulation and neurodegeneration before the onset of cognitive decline. The association between tau accumulation and reduced glucose metabolism in cognitively normal participants supports the need for research and intervention to be aimed at the preclinical stages of AD.

Multimodality Imaging of Cardiac Angiolipoma

HomeRadiologyVol. 307, No. 5 PreviousNext Reviews and CommentaryFree AccessImages in RadiologyMultimodality Imaging of Cardiac AngiolipomaSimin Lin, Haojun Chen Simin Lin, Haojun Chen Author AffiliationsFrom the Department of Radiology, Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, No. 2999 Jinshan Rd, Xiamen 361006, China (S.L.); and Department of Nuclear Medicine & Minnan PET Center, First Affiliated Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, China (H.C.).Address correspondence to H.C. (email: [email protected]).Simin LinHaojun Chen Published Online:Jun 13 2023https://doi.org/10.1148/radiol.230116MoreSectionsPDF ToolsImage ViewerAdd to favoritesCiteTrack CitationsPermissionsReprints ShareShare onFacebookTwitterLinked In A 39-year-old man presented with a history of abdominal pain for 2 months. A routine chest radiograph showed an increased cardiothoracic ratio, and US was subsequently performed. At transthoracic echocardiography, an isoechoic cardiac mass was incidentally found in the anterior wall of the right atrium. The patient had no symptoms of chest tightness, chest pain, or dyspnea. His tumor markers showed a mild elevation of cancer antigen 125 (36.50 U/mL) and cancer antigen 724 (14.98 U/mL). The patient was scheduled for cardiac MRI to further characterize the lesion. A static four-chamber view obtained with a steady-state free precession sequence showed a 7.3 × 4.0-cm mass with heterogeneous signal intensity in the right atrium and atrioventricular groove (Figure, A). First-pass perfusion imaging indicated no apparent perfusion in the mass, which encased the right coronary artery (Figure, B). Inhomogeneous enhancement was detected with late gadolinium enhancement sequences (Figure, C), raising suspicion for malignancy. Hence, correlative fluorine 18 (18F) fluorodeoxyglucose (FDG) PET/CT was performed for tumor staging. Axial PET/CT images (Figure, D) revealed areas of fat attenuation and low 18F-FDG uptake, yielding a tumor-to-background ratio of 1:1. No abnormal radioactivity was observed in the extracardiac areas. The patient subsequently underwent radical tumor resection and surgical reconstruction of the right atrium. Histopathologic workup showed adipose tissue and interspersed proliferating blood vessels, consistent with the diagnosis of cardiac angiolipoma.(A) Cardiac MRI scan obtained with steady-state free precession (SSFP) shows a soft-tissue mass with heterogeneous signal intensity in the right atrium and atrioventricular groove (arrow). (B) First-pass perfusion MRI scan shows the mass encasing the right coronary artery (coronary vessel floating sign) without evident perfusion (arrowheads). (C) Short-axial late gadolinium enhancement (LGE) MRI scan shows inhomogeneous enhancement of the mass (arrow). (D) Axial fluorine 18 (18F) fluorodeoxyglucose (FDG) PET/CT image reveals areas of fat attenuation and mild 18F-FDG uptake (arrow) within the lesion (maximum standardized uptake value, 2.9), with a tumor-to-background ratio of 1:1.Download as PowerPointOpen in Image Viewer Disclosures of conflicts of interest: S.L. No relevant relationships. H.C. No relevant relationships.Article HistoryReceived: Jan 17 2023Revision requested: Feb 15 2023Revision received: Feb 17 2023Accepted: Mar 10 2023Published online: June 13 2023 FiguresReferencesRelatedDetailsRecommended Articles Dissection of a Giant Coronary AneurysmRadiology: Cardiothoracic Imaging2023Volume: 5Issue: 1Multimodality Imaging of Transposition of the Great ArteriesRadioGraphics2021Volume: 41Issue: 2pp. 338-360Fibrous Skeleton of the Heart: Anatomic Overview and Evaluation of Pathologic Conditions with CT and MR ImagingRadioGraphics2017Volume: 37Issue: 5pp. 1330-1351Cinematic Rendering of Complex Coronary Artery Left Atrial FistulaRadiology2022Volume: 307Issue: 1Active Cardiac Sarcoidosis Imitating Cardiac MetastasesRadiology: Cardiothoracic Imaging2020Volume: 2Issue: 6See More RSNA Education Exhibits Pearls and Pitfalls in Cardiac ImagingDigital Posters2022Multimodal Imaging Characterization of Cardiac Tumors Emphasizing PET with Pathology Correlation Using the New 2021 WHO ClassificationDigital Posters2022Mulmodality Imaging of Atrioventricular Groove Masses - Diagnostic ApproachDigital Posters2022 RSNA Case Collection Cardiac metastasis from melanomaRSNA Case Collection2022Cardiac myxomaRSNA Case Collection2020Primary Cardiac ParagangliomaRSNA Case Collection2022 Vol. 307, No. 5 Metrics Altmetric Score PDF download

Altered brain energy metabolism related to astrocytes in tauopathies

AbstractBackgroundAccumulated evidence suggests altered energy metabolism in the brain of tauopathies. In Alzheimer’s disease (AD) and progressive supranuclear palsy (PSP), decreased fluorodeoxyglucose (FDG) uptake in the cingulate cortex is considered a marker of neurodegeneration. However, its underlying pathogenesis remains unknown. It is hypothesized that lactate, a glucose metabolite, is produced in astrocytes and subsequently shuttles to neurons as an energy substrate. The current study aims to examine alterations in lactate and glucose concentrations and their association with astrocytic activities in the cingulate cortex of patients with AD and PSP.MethodThirty AD, 30 PSP, and 30 healthy control (HC) subjects were enrolled. Lactate, glucose, and myoinositol (mI), an astroglial marker, in the anterior cingulate cortex (ACC) and posterior cingulate cortex (PCC) were determined by magnetic resonance spectroscopy (MRS) (3T scanner, SPECIAL sequence, TR/TE 3000/8.5ms, LCModel analysis) (Figure 1). Tau depositions were assessed using PET imaging with 18F‐PM‐PBB3.ResultAll the patients with AD and PSP were confirmed to have the typical distribution of tau pathology. Lactate, glucose, and mI levels were higher in the ACC in PSP and AD, and PCC in AD compared to HC (p < 0.05) (Figure 2). In these cortical regions, lactate levels showed a positive correlation with mI levels (p < 0.05) (Figure 3). Lactate levels in the PCC in AD patients showed a positive correlation with Clinical Dementia Rating‐Sum of Boxes (CDR‐SB) scores (p < 0.05) (Figure 4). Moreover, mI levels in the ACC in PSP patients were negatively correlated with Frontal Assessment Battery (FAB) scores (p < 0.05) (Figure 4).ConclusionWe found elevated lactate and glucose levels accompanied by an increased astroglial marker mainly in the PCC in AD and ACC in PSP patients. Moreover, elevated lactate and mI levels in the cingulate cortex reflected the cognitive decline of AD and PSP, respectively. The excess lactate and glucose levels in the disease‐specific regions might reflect decreased energy utilization as shown in previous FDG‐PET studies. Given the residual lactate levels were correlated with mI levels, we speculated that the impaired lactate shuttle of reactivated astrocytes disrupts energy metabolism, leading to cognitive dysfunctions.

Longitudinal Changes in Insulin Resistance, Cognition, and AD Biomarkers across the AD Continuum

AbstractBackgroundTo determine if 3‐year changes in serum insulin resistance (IR) were related to changes in brain volume and glucose uptake, cognition, and CSF biomarkers in cognitively unimpaired and impaired older adults.MethodAlzheimer’s Disease Neuroimaging Initiative data was downloaded for 275 aged adults (55‐89 years). Participants had longitudinal T1‐ and T2‐weighted volume scans, fluorodeoxyglucose (FDG) scans, CSF β‐amyloid (Aβ) and tau species, and cognitive performance over baseline and months 6, 12, 18, 24, and 36. Growth curve modeling in R regressed IR against these outcomes, by itself and with clinical diagnosis as a moderator. Cognitively unimpaired (CU) adults were used as a reference group to determine potential effects in pathological aging.ResultIn AD and/or Mild Cognitive Impairment progressors to AD (MCI‐P), higher IR over time was related to progressive atrophy in medial temporal frontoinsular areas. Similarly, decline was seen in global cognition and both memory and executive function. HOMA1‐IR associations were partially mediated by p‐tau‐181. Among clinical diagnosis groups, higher IR was significantly related to amyloid, p‐tau‐181, and total tau 181 among AD patients but not MCI or unimpaired groups.ConclusionThese findings suggest that in older adults who develop AD or had AD at baseline, higher IR over time is related to brain atrophy and consequent cognitive decline, perhaps as a function of amyloid or tau deposition.

Long‐term efficacy and safety of zanubrutinib (ZANU) in relapsed/refractory marginal zone lymphoma (R/R MZL): final analysis of the MAGNOLIA (BGB‐3111‐214) trial

Long‐term efficacy and safety of zanubrutinib (ZANU) in relapsed/refractory marginal zone lymphoma (R/R MZL): final analysis of the MAGNOLIA (BGB‐3111‐214) trial

Comparative study of the quantitative accuracy of oncological PET imaging based on deep learning methods.

[18F] Fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) is an important tool for tumor assessment. Shortening scanning time and reducing the amount of radioactive tracer remain the most difficult challenges. Deep learning methods have provided powerful solutions, thus making it important to choose an appropriate neural network architecture. A total of 311 tumor patients who underwent 18F-FDG PET/CT were retrospectively collected. The PET collection time was 3 min/bed. The first 15 and 30 s of each bed collection time were selected to simulate low-dose collection, and the pre-90s was used as the clinical standard protocol. Low-dose PET was used as input, convolutional neural network (CNN, 3D Unet as representative) and generative adversarial network (GAN, P2P as representative) were used to predict the full-dose images. The image visual scores, noise levels and quantitative parameters of tumor tissue were compared. There was high consistency in image quality scores among all groups [Kappa =0.719, 95% confidence interval (CI): 0.697-0.741, P<0.001]. There were 264 cases (3D Unet-15s), 311 cases (3D Unet-30s), 89 cases (P2P-15s) and 247 cases (P2P-30s) with image quality score ≥3, respectively. There was significant difference in the score composition among all groups (χ2=1,325.46, P<0.001). Both deep learning models reduced the standard deviation (SD) of background, and increased the signal-to-noise ratio (SNR). When 8%PET images were used as input, P2P and 3D Unet had similar enhancement effect on SNR of tumor lesions, but 3D Unet could significantly improve the contrast-noise ratio (CNR) (P<0.05). There was no significant difference in SUVmean of tumor lesions compared with s-PET group (P>0.05). When 17%PET image was used as input, SNR, CNR and SUVmax of tumor lesion of 3D Unet group had no statistical difference with those of s-PET group (P>0.05). Both GAN and CNN can suppress image noise to varying degrees and improve image quality. However, when 3D Unet reduces the noise of tumor lesions, it can improve the CNR of tumor lesions. Moreover, quantitative parameters of tumor tissue are similar to those under the standard acquisition protocol, which can meet the needs of clinical diagnosis.

FDG-PET/CT and rest myocardial perfusion imaging to predict high-degree atrioventricular block recovery in cardiac sarcoidosis.

High-degree atrioventricular block (AVB) recovery in CS has been shown to be highly variable despite immunosuppressive treatment, with no reliable tool available to predict odds of reversibility. This study sought to evaluate the potential of combined fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) and resting myocardial perfusion imaging (rMPI) to predict reversibility of newly diagnosed high-grade AVB in cardiac sarcoidosis (CS). We performed a single-center, retrospective analysis of patients with CS presenting with high-grade AVB who underwent combined FDG-PET/CT and rMPI. The 2016 JCS and the 2014 HRS diagnostic criteria were used for the diagnosis of CS. Patients with a history of coronary artery disease or prior immunosuppressive treatment were excluded. Patients were divided into AVB recovery and non-recovery subgroups. CS disease staging was based on FDG-PET and rMPI findings: (Stage 0) normal FDG-PET and rMPI (Stage 1) positive FDG-PET and normal rMPI (Stage 2) positive FDG-PET with perfusion deficits on rMPI (Stage 3) normal FDG-PET with perfusion deficits on rMPI. Twenty-seven patients, including 13 demonstrating AVB recovery, were identified. Eleven out of fourteen (78.6%) patients presenting with stage 1 CS demonstrated AVB recovery. Stage 1 CS was significantly more present in the recovery group compared to the non-recovery group (84.6% vs 21.4%, P = .002). Eleven presented with stage 2 CS, with only 2 (18.2%) recovering AV nodal conduction. Stage 2 CS presented more frequently in the non-recovery group (64.3% vs 15.4%, P = .020). Combined FDG-PET and rMPI employed to stage CS disease presenting with high-degree AVB appears to have good performance for predicting likelihood of recovery.

Waldenström macroglobulinemia diagnosed by bronchoalveolar lavage.

An 88-year-old woman with no significant medical history was admitted to the emergency room with persistent dyspnea and cough. Chest computed tomography (CT) showed diffuse ground-glass opacities in both the lungs (Fig. 1A). Collagen disease and infection were ruled out, and lymphoproliferative disease was suspected based on high level of WBC 15 200/μL (lymphocyte 63.7%), soluble interleukin 2 receptor 3070 (151–474) IU/mL and LDH 421 (115–245) U/L. Fluorodeoxyglucose (FDG) did not accumulate in the lymph nodes throughout the body, and its accumulation as ground-glass shadows (Fig. 1B) led us to suspect a lung lesion; therefore, we performed a bronchoscopy. The patient experienced severe hypoxemia during bronchoalveolar lavage, and the biopsy was cancelled. Cell block of bronchoalveolar lavage fluid showed CD20-positive atypical lymphocytes and plasma cells, which were κ chain-positive, IgM-positive, IgG-, IgA- and λ chain-negative (Fig. 2). Blood protein fractionation showed M-protein, with increased IgM at 679 (46–260) mg/dL, and decreased IgG at 425 (870–1700) mg/dL and IgA at 8 (110–410) mg/dL. Based on these findings, the patient was diagnosed with Waldenström macroglobulinemia (WM). The patient was treated with steroids, and fever and dyspnea symptoms were relieved. The haematologist performed a bone marrow biopsy (Fig. 3), and confirmed the diagnosis of WM based on the findings of the bone marrow biopsy and flow cytometry of peripheral blood, which showed small B cells with a κ > > λ bias, negative CD5 and CD23, and IgM-κ and Bence Jones protein-κ detected by immunofixation, after which the patient received rituximab. On chest CT 120 days after starting rituximab, the ground-glass opacities in the both lungs disappeared (Fig. 4), and there has been no relapse for more than a year to date.

Cognitive Deficits in Parkinson's Disease Are Associated with Neuronal Dysfunction and Not White Matter Lesions.

Cognitive deficits considerably contribute to the patient's burden in Parkinson's disease (PD). While cognitive decline is linked to neuronal dysfunction, the additional role of white matter lesions (WML) is discussed controversially. To investigate the influence of WML, in comparison to neuronal dysfunction, on cognitive deficits in PD. We prospectively recruited patients with PD who underwent neuropsychological assessment using the Mattis Dementia Rating Scale 2 (DRS-2) or Parkinson Neuropsychometric Dementia Assessment (PANDA) and both MRI and PET with [18F]fluorodeoxyglucose (FDG). WML-load and PD cognition-related covariance pattern (PDCP) as a measure of neuronal dysfunction were read out. Relationship between cognitive performance and rank-transformed WML was analyzed with linear regression, controlling for the patients' age. PDCP subject scores were investigated likewise and in a second step adjusting for age and WML load. Inclusion criteria were met by 76 patients with a mean (± SD) age of 63.5 ± 9.0 years and disease duration of 10.7 ± 5.4 years. Neuropsychological testing revealed front executive and parietal deficits and a median DRS-2 score of 137 (range 119-144)/144 and PANDA score of 22 (range 3-30)/30. No association between WML and cognition was observed, whereas PDCP subject scores showed a trend-level negative correlation with the DRS-2 (P = 0.060) as well as a negative correlation with PANDA (P = 0.049) which persisted also after additional correction for WML (P = 0.039). The present study indicates that microangiopathic WML do not have a relevant impact on neurocognitive performance in PD whereas neuronal dysfunction does.

Differentiation between rebound thymic hyperplasia and thymic relapse after chemotherapy in pediatric Hodgkin lymphoma.

Rebound thymic hyperplasia (RTH) is a common phenomenon caused by stress factors such as chemotherapy (CTX) or radiotherapy, with an incidence between 44% and 67.7% in pediatric lymphoma. Misinterpretation of RTH and thymic lymphoma relapse (LR) may lead to unnecessary diagnostic procedures including invasive biopsies or treatment intensification. The aim of this study was to identify parameters that differentiate between RTH and thymic LR in the anterior mediastinum. After completion of CTX, we analyzed computed tomographies (CTs) and magnetic resonance images (MRIs) of 291 patients with classical Hodgkin lymphoma (CHL) and adequate imaging available from the European Network for Pediatric Hodgkin lymphoma C1 trial. In all patients with biopsy-proven LR, an additional fluorodeoxyglucose (FDG)-positron emission tomography (PET)-CT was assessed. Structure and morphologic configuration in addition to calcifications and presence of multiple masses in the thymic region and signs of extrathymic LR were evaluated. After CTX, a significant volume increase of new or growing masses in the thymic space occurred in 133 of 291 patients. Without biopsy, only 98 patients could be identified as RTH or LR. No single finding related to thymic regrowth allowed differentiation between RTH and LR. However, the vast majority of cases with thymic LR presented with additional increasing tumor masses (33/34). All RTH patients (64/64) presented with isolated thymic growth. Isolated thymic LR is very uncommon. CHL relapse should be suspected when increasing tumor masses are present in distant sites outside of the thymic area. Conversely, if regrowth of lymphoma in other sites can be excluded, isolated thymic mass after CTX likely represents RTH.

Rapid Whole-Body FDG PET/MRI in Oncology Patients: Utility of Combining Bayesian Penalised Likelihood PET Reconstruction and Abbreviated MRI.

This study evaluated the diagnostic value of a rapid whole-body fluorodeoxyglucose (FDG) positron emission tomography (PET)/magnetic resonance imaging (MRI) approach, combining Bayesian penalised likelihood (BPL) PET with an optimised β value and abbreviated MRI (abb-MRI). The study compares the diagnostic performance of this approach with the standard PET/MRI that utilises ordered subsets expectation maximisation (OSEM) PET and standard MRI (std-MRI). The optimal β value was determined by evaluating the noise-equivalent count (NEC) phantom, background variability, contrast recovery, recovery coefficient, and visual scores (VS) for OSEM and BPL with β100-1000 at 2.5-, 1.5-, and 1.0-min scans, respectively. Clinical evaluations were conducted for NECpatient, NECdensity, liver signal-to-noise ratio (SNR), lesion maximum standardised uptake value, lesion signal-to-background ratio, lesion SNR, and VS in 49 patients. The diagnostic performance of BPL/abb-MRI was retrospectively assessed for lesion detection and differentiation in 156 patients using VS. The optimal β values were β600 for a 1.5-min scan and β700 for a 1.0-min scan. BPL/abb-MRI at these β values was equivalent to OSEM/std-MRI for a 2.5-min scan. By combining BPL with optimal β and abb-MRI, rapid whole-body PET/MRI could be achieved in ≤1.5 min per bed position, while maintaining comparable diagnostic performance to standard PET/MRI.

Independent association of metabolic tumor response on FDG-PET with pulmonary toxicity following risk-adaptive chemoradiation for unresectable non-small cell lung cancer: Inherent radiosensitivity or immune response?

BackgroundIn the context of a phase II trial of risk-adaptive chemoradiation, we evaluated whether tumor metabolic response could serve as a correlate of treatment sensitivity and toxicity. MethodsForty-five patients with AJCCv7 stage IIB-IIIB NSCLC enrolled on the FLARE-RT phase II trial (NCT02773238). [18F]fluorodeoxyglucose (FDG) PET-CT images were acquired prior to treatment and after 24 Gy during week 3. Patients with unfavorable on-treatment tumor response received concomitant boosts to 74 Gy total over 30 fractions rather than standard 60 Gy. Metabolic tumor volume and mean standardized uptake value (SUVmean) were calculated semi-automatically. Risk factors of pulmonary toxicity included concurrent chemotherapy regimen, adjuvant anti-PDL1 immunotherapy, and lung dosimetry. Incidence of CTCAE v4 grade 2+ pneumonitis was analyzed using the Fine-Gray method with competing risks of metastasis or death. Peripheral germline DNA microarray sequencing measured predefined candidate genes from distinct pathways: 96 DNA repair, 53 immunology, 38 oncology, 27 lung biology. ResultsTwenty-four patients received proton therapy, 23 received ICI, 26 received carboplatin-paclitaxel, and 17 pneumonitis events were observed. Pneumonitis risk was significantly higher for patients with COPD (HR 3.78 [1.48, 9.60], p = 0.005), those treated with immunotherapy (HR 2.82 [1.03, 7.71], p = 0.043) but not with carboplatin-paclitaxel (HR 1.98 [0.71, 5.54], p = 0.19). Pneumonitis rates were similar among selected patients receiving 74 Gy radiation vs 60 Gy (p = 0.33), proton therapy vs photon (p = 0.60), or with higher lung dosimetric V20 (p = 0.30). Patients in the upper quartile decrease in SUVmean (>39.7%) were at greater risk for pneumonitis (HR 4.00 [1.54, 10.44], p = 0.005) and remained significant in multivariable analysis (HR 3.34 [1.23, 9.10], p = 0.018). Germline DNA gene alterations in immunology pathways were most frequently associated with pneumonitis. ConclusionTumor metabolic response as measured by mean SUV is associated with increased pneumonitis risk in a clinical trial cohort of NSCLC patients independent of treatment factors. This may be partially attributed to patient-specific differences in immunogenicity.

Influence of Cirrhosis on 68Ga-FAPI PET/CT in Intrahepatic Tumors.

Background Gallium 68 (68Ga)-labeled fibroblast activation protein inhibitor (FAPI) is of great diagnostic value for intrahepatic tumors. However, cirrhosis may lead to increased 68Ga-FAPI uptake in background liver, affecting the diagnostic ability of 68Ga-FAPI. Purpose To assess the effect of cirrhosis on liver parenchyma and intrahepatic tumor uptake of 68Ga-FAPI and to compare the ability of 68Ga-FAPI and fluorine 18 (18F)-labeled fluorodeoxyglucose (FDG) PET/CT to depict intrahepatic tumors in patients with cirrhosis. Materials and Methods In this secondary analysis of a prospective trial, patients who underwent both 68Ga-FAPI and 18F-FDG PET/CT and those who underwent only 68Ga-FAPI PET/CT between August 2020 and May 2022 were considered for inclusion in the cirrhotic or noncirrhotic group, respectively. Patients with cirrhosis were chosen via a comprehensive assessment of imaging and clinical data, and patients without cirrhosis were randomly selected. 68Ga-FAPI and 18F-FDG PET/CT data were measured by two radiologists. Between-groups and within-group data were tested with the Mann-Whitney U test and the Wilcoxon signed-rank test, respectively. Results A total of 39 patients with cirrhosis (median age, 58 years [IQR, 50-68]; 29 male; 24 intrahepatic tumors) and 48 patients without cirrhosis (median age, 59 years [IQR, 51-67]; 30 male; 23 intrahepatic tumors) were evaluated. In patients without intrahepatic tumors, the liver 68Ga-FAPI average standardized uptake value (SUVavg) was higher in the cirrhotic group than in the noncirrhotic group (median SUVavg, 1.42 [IQR, 0.55-2.85] vs 0.45 [IQR, 0.41-0.72]; P = .002). However, no difference was observed in the diagnosis of intrahepatic tumor sensitivity (98% vs 93%, respectively). When compared with 18F-FDG, the sensitivity of 68Ga-FAPI PET/CT in the detection of intrahepatic tumors in patients with cirrhosis (41% vs 98%, respectively) and maximum standardized uptake value of tumors (median SUVmax, 2.60 [IQR, 2.14-4.49] vs 6.68 [IQR, 4.65-10.08]; P < .001) were higher. Conclusion The sensitivity of 68Ga-FAPI in the diagnosis of intrahepatic tumors was not affected by cirrhosis, and diagnostic accuracy of 68Ga-FAPI was higher than that of 18F-FDG in patients with cirrhosis. © RSNA, 2023 Supplemental material is available for this article.

Methods for assessment of disease activity of polymyalgia rheumatica

Polymyalgia rheumatica (PMR) is the second most frequent inflammatory rheumatic disease in old age. Remission and recurrence are frequently used as endpoints in clinical trials; however, there is as yet no international consensus on the definition of these states, which limits the comparability of published studies. The PMR activity score (PMR-AS) is the only composite score specifically developed for PMR, which together with remission is used to define low, middle and high disease activity. In recent studies the PMR-AS was often used and low disease activity was established as endpoint. The most important limitation of the PMR-AS is the potential influence of the individual variables by comorbidities. The value of C‑reactive protein (CRP) and the erythrocyte sedimentation rate (ESR) are of restricted value in studies using drugs that influence the interleukin 6 (IL-6) axis. In these cases, calprotectin and osteopontin are promising alternative biomarkers, as they have already been shown to reflect disease activity independently of CRP in rheumatoid arthritis. Furthermore, imaging modalities including sonography, magnetic resonance imaging and fluorodeoxyglucose (FDG) positron emission tomography could also be helpful in monitoring disease activity; however, these techniques must first be validated in further studies. The PMR impact scale (PMR-IS) is acomposite score to assess the impact of PMR on the patients; however, it has not yet been used in clinical studies. The development of additional patient reported outcomes (PRO) for PMR and the definition of standardized criteria for documentation of remission and recurrence are important questions in the future research agenda for PMR.

Assessment of external radiation dose rate after 18FDG-PET/CT examination

BackgroundF-18 FDG (fluorodeoxyglucose) PET/CT procedures are one of the most growing studies used for patient management in oncology, cardiology, neurology, and other indications, in which the challenges meet both patients and clinicians, especially when we are looking for the presence/absence of disease progression and cure. This study was conducted to assess the external radiation dose after 18FDG-PET/CT examination. In total, 117 patients were enrolled in the study. Radiation exposure was measured using a calibrated RadEye SPRD-ER personal radiation detector. The measurements were taken at 0, 30, 100, 150, and 200 cm distance from the patient. The time of measurement was immediately post-injection, 30 min, 60 min after injection, and at the time of releasing the patient.ResultsThe result showed that the mean radiation equivalent dose rate at 0 min/0 cm was 414 µSv/h, at 30 min/30 cm was 99.7 µSv/h, and 60 min/100 cm was 18.3 µSv/h. The radiation doses at different distances (0, 30, 100, 150, and 200 cm) were 160.9 µSv/h, 70.9 µSv/h, 12.4 µSv/h, 7 µSv/h, and 3.7 µSv/h, respectively.ConclusionIn conclusion, the patient can be safely released after 2 h of injection in (18F-FDG) PET/CT and the radiation dose can be limited by increasing distance from the radiation source and also instructing them to drink much more water to enhance the process of excretions. The dose rates are low in this study; if the staff interact with multiple patients, they will not approach exposure limits. Similarly, dose rates are so low at patient release that family will not receive doses above regulatory limits.

PO-04-050 ROLE OF FDG-PET CT IN GUIDING THERAPY FOR RELAPSING AND REMITTING MYOCARDITIS

Fluorodeoxyglucose (FDG)-positron emission tomography (PET) scan is considered as a goal standard test for the diagnosis of myocarditis. Low intensity FDG uptake of the lateral wall without perfusion abnormalities is considered to be a variant of normal. It is imperative to correlate myocardial and pericardial abnormality revealed by myocardial FDG uptake with the signs and symptoms of myocardial disease, as it tends to be overlooked. However, recognition of possible underlying disease will support further patient management to avoid complications due to the disease. While the utility of FDG PET in the diagnosis of myocarditis and initiation of therapy is well documented, there is no consensus in the preferred strategy for monitoring the response to therapy. To present a case highlighting the utilization of FDG PET in guiding the therapy for relapsing/remitting myocarditis. N/A A 55yo male presented with new onset HF with LVEF of 15-20% at the time of index presentation. He underwent cardiac catheterization which showed non-obstructive CAD. He was diagnosed with NICM and was discharged home on GDMT with a wearable external defibrillator. His outpatient work-up with FDG PET imaging showed normal perfusion with FDG uptake involving the proximal, mid inferolateral, and lateral region with a SUV-max of 3.4. Biopsy was determined to be too high-risk and was therefore not pursued. He was diagnosed with chronic idiopathic myocarditis with possible isolated cardiac sarcoidosis and started on methotrexate (MTX). Prednisone was considered but decided against due to comorbid diabetes. His follow up FDG PET in 6 months reported an increase in the SUV max to 4.2 and involvement of lateral base in addition to the mid-inferolateral region [Figure 1(a),(b)]. Due to lack of improvement, the patient was switched from MTX to mycophenolate. Repeat 6 month follow up FDG PET showed resolution of myocarditis with SUV-max of 2.6 [Figure 1(c),(d)] and patient was taken off immunosuppressive therapy. Six-month follow-up FDG PET was unchanged and was thus reassuring. One year later, the patient relapsed with focal FDG uptake of entire lateral and mid and basal inferolateral walls with an SUV max of 11.2 on imaging [Figure 1(e),(f)]. The patient was consequently restarted on mycophenolate therapy. This case highlights the relapsing and remitting clinical course of a patient with FDG-PET uptake in myocardium which was treated with immunosuppressive therapy with serial FDG-PET guidance.

PO-01-087 A RARE CASE OF BI-ATRIAL FDG-UPTAKE: PRESENTING AS NEW ONSET ATRIAL FIBRILLATION

Isolated atrial myocarditis is rare, with presenting symptoms that are non-specific. Prior reports have suggested association with atrial arrythmias and increased risk of stroke due to atrial dysfunction. Fluorodeoxyglucose (FDG)-positron emission tomography (PET) CT scan is considered as a goal standard test for the diagnosis of myocarditis. To present a case highlighting that isolated atrial myocarditis had higher incidence atrial arrythmias and oral anticoagulation should be considered in such cases. N/A A 55yo male with no prior medical history presented with non-specific symptoms of fatigue, shortness of breath and frequent palpitations. He underwent 2D echocardiogram showed LVEF of 50-55% with mild bi-atrial dilatation with no regional wall motion abnormalities and was diagnosed with incidental atrial fibrillation during the procedure. He was referred to cardiac electrophysiology for further work up. During his initial EP clinic visit, 12 lead ECG demonstrated normal sinus rhythm with premature atrial contractions and premature ventricular contractions. Due to symptomatic, dual chamber arrythmias, cardiac MRI (CMR) and FDG-PET CT was ordered to rule out myocarditis. The CMR was negative for any LGE however, high-fat dietary preparation FDG-PET CT scan revealed uptake on bi-atrial walls (figure) and interatrial septum with SUV max of 3.1. There was no LV myocardial FDG uptake noted. Patient was diagnosed with isolated atrial myocarditis and was started on dronedarone, OAC (CHADS2VASc =0) for stroke prophylaxis and immunosuppressive therapy (methotrexate and low dose prednisone). Invasive atrial myocardial biopsy was not considered due good response to therapy. Isolated atrial myocarditis is an uncommon presentation of acute myocarditis and is associated with atrial arrythmias. FDG PET-CT or CMR imaging may be useful to aid diagnosis. Long-term response to immunosuppressive therapy may need further investigations. OAC should be considered for stroke prophylaxis, despite low CHADS2VASc due to unknown long-term implications of atrial dysfunction.

SPECT and PET in nonlesional epilepsy

AbstractBackgroundPositron emission tomography (PET) and single-photon emission computed tomography (SPECT) are applied in epilepsy mostly during presurgical assessment. Nonlesional focal epilepsy is very challenging for presurgical evaluation in cases of refractory epilepsy.ObjectivesWe aimed to investigate the contribution of PET and SPECT to focus localization in nonlesional epilepsy.MethodsThe basic principles of SPECT and PET including different tracers were reviewed. The literature and the most recent publications are discussed in view of findings in nonlesional epilepsy.ResultsIctal SPECT shows a high sensitivity of over 80% for ictal onset zone in nonlesional epilepsy. Postprocessing with subtraction ictal SPECT co-registered with MRI (SISCOM) or statistical parametric mapping are the gold standard. Histopathological findings in nonlesional epilepsies with concordant ictal SPECT imaging show focal cortical dysplasia in up to 75% of cases. Ictal injection is unsuccessful in approximately 20% of cases and the procedure is very time consuming and labor intensive. Fluorodeoxyglucose (FDG)-PET in nonlesional epilepsy shows variable sensitivity of 46–76%. As with ictal SPECT, it benefits from postprocessing of co-registration with magnetic resonance imaging (MRI) or even statistical parametric mapping. Hybrid PET/magnetic resonance imaging (MRI) scanners provide additional benefits for identifying lesions. Other PET tracers (11C‑Flumazenil (FMZ), α-11C‑methyl-L-tryptophane (AMT)) are clinically applied in special cases only. Both procedures contribute complementary information in multimodal imaging diagnostics.ConclusionsIctal SPECT and PET are optional diagnostic tools for presurgical assessment in nonlesional epilepsies. They may reverse nonlesional to lesional epilepsy status and identify nonlesional epileptic foci with a fair chance of seizure freedom after epilepsy surgery.

Who needs a fine‐needle biopsy? A comparison of the ATA and ACR TI‐RADS guidelines in a single‐centre retrospective study

AbstractThe 2015 American Thyroid Association (ATA) and 2017 American College of Radiology: Thyroid Imaging, Reporting and Data System (ACR TI‐RADS) guidelines are two popular guidelines adopted to stratify sonographic risk of malignancy for thyroid nodules, and to select cases for fine‐needle aspiration (FNA). To understand the test performance of the two systems in predicting thyroid malignancy, 164 thyroidectomy cases performed in a regional hospital in Hong Kong between January 2021 and June 2022 were reviewed. Sonographic images of the index nodule in each case were retrospectively classified into different risk categories using the ATA and ACR TI‐RADS guidelines, respectively, followed by retrieval of cytological and pathological results, for comparison. The index nodule was proven malignant in 26.8% of cases in the final pathology. There was a strong and positive correlation between the ATA and ACR TI‐RADS risk categories assignment (rs = .931, p &lt; .001). Recommending FNA according to the ATA had a better sensitivity for malignancy than using the ACR TI‐RADS (81.8% vs 72.7%), at the expense of a lower specificity (10.8% vs 40.8%). The sensitivity for malignancy of both systems could be further improved if all fluorodeoxyglucose (FDG)‐avid nodules were investigated with FNA regardless of sonographic features and size. There was a statistically significant association between “nodules with FDG avidity and nodules recommended for FNA by the ACR TI‐RADS guideline” and an eventual malignant thyroid nodule (p = .002).

Increased tryptophan, but not increased glucose metabolism, predict resistance of pembrolizumab in stage III/IV melanoma

ABSTRACT Clinical trials of combined IDO/PD1 blockade in metastatic melanoma (MM) failed to show additional clinical benefit compared to PD1-alone inhibition. We reasoned that a tryptophan-metabolizing pathway other than the kynurenine one is essential. We immunohistochemically stained tissues along the nevus-to-MM progression pathway for tryptophan-metabolizing enzymes (TMEs; TPH1, TPH2, TDO2, IDO1) and the tryptophan transporter, LAT1. We assessed tryptophan and glucose metabolism by performing baseline C11-labeled α-methyl tryptophan (C11-AMT) and fluorodeoxyglucose (FDG) PET imaging of tumor lesions in a prospective clinical trial of pembrolizumab in MM (clinicaltrials.gov, NCT03089606). We found higher protein expression of all TMEs and LAT1 in melanoma cells than tumor-infiltrating lymphocytes (TILs) within MM tumors (n = 68). Melanoma cell-specific TPH1 and LAT1 expressions were significantly anti-correlated with TIL presence in MM. High melanoma cell-specific LAT1 and low IDO1 expression were associated with worse overall survival (OS) in MM. Exploratory optimal cutpoint survival analysis of pretreatment ‘high’ vs. ‘low’ C11-AMT SUVmax of the hottest tumor lesion per patient revealed that the ‘low’ C11-AMT SUVmax was associated with longer progression-free survival in our clinical trial (n = 26). We saw no such trends with pretreatment FDG PET SUVmax. Treatment of melanoma cell lines with telotristat, a TPH1 inhibitor, increased IDO expression and kynurenine production in addition to suppression of serotonin production. High melanoma tryptophan metabolism is a poor predictor of pembrolizumab response and an adverse prognostic factor. Serotoninergic but not kynurenine pathway activation may be significant. Melanoma cells outcompete adjacent TILs, eventually depriving the latter of an essential amino acid.