Positron Emission Tomography Evaluation Research Articles

Preclinical Evaluation of Azabenzimidazole-Based PET Radioligands for γ-8 Dependent Transmembrane AMPA Receptor Regulatory Protein Imaging.

AMPA glutamate receptors (AMPARs) play a pivotal role in excitatory neurotransmission, particularly in the hippocampus where the TARP γ-8 subunit is enriched and serves as a target for emerging anti-epileptic drugs. To enable in vivo visualization of TARP γ-8 distribution and expression by positron emission tomography (PET), this study focuses on the development of novel 18 F-labeled TARP γ-8 inhibitors and their corresponding precursors, stemming from the azabenzimidazole scaffold. The resulting radioligands [18 F]TARP-2204 and [18 F]TARP-2205 were successfully synthesized with acceptable radiochemical yield, high molar activity, and excellent radiochemical purity. In vitro autoradiography demonstrates high level of specific binding of [18 F]TARP-2205 to TARP γ-8 in both rat and nonhuman primate brain tissues. However, unexpected radiodefluorination in PET imaging studies of rodents emphasizes the need for further structural refinement. This work serves as an excellent starting point for the development of future 18 F-labeled TARP γ-8 PET tracers, offering valuable insights into medicinal chemistry design, radiosynthesis and subsequent PET evaluation.

Assessing the role of positron emission tomography and bone scintigraphy in imaging of pleuropulmonary blastoma (PPB): A report from the International PPB/DICER1 Registry.

Pleuropulmonary blastoma (PPB) is the most common primary lung neoplasm of infancy and early childhood. Given the rarity of PPB, the role of positron emission tomography (PET) and bone scintigraphy (bone scans) in diagnostic evaluation and surveillance has not been documented to date. Available PET and bone scan data are presented in this study. Patients with PPB enrolled in the International PPB/DICER1 Registry and available PET imaging and/or bone scan reports were retrospectively abstracted. On retrospective analysis, 133 patients with type II and III (advanced) PPB were identified with available report(s) (PET scan only=34, bone scan only=83, and both bone scan and PET=16). All advanced primary PPB (n=11) and recurrent (n=8) tumors prior to treatment presented with 18 F-fluorodeoxyglucose (FDG)-avid lesions, with median maximum standardized uptake values of 7.4 and 6.7, respectively. False positive FDG uptake in the thorax was noted during surveillance (specificity: 59%). Bone metastases were FDG-avid prior to treatment. Central nervous system metastases were not discernable on PET imaging. Sensitivity and specificity of bone scans for metastatic bone disease were 89% and 92%, respectively. Bone scans had a negative predictive value of 99%, although positive predictive value was 53%. Four patients with distant bone metastases had concordant true positive bone scan and PET. Primary, recurrent, and/or extracranial metastatic PPB presents with an FDG-avid lesion on PET imaging. Additional prospective studies are needed to fully assess the utility of nuclear medicine imaging in surveillance for patients with advanced PPB.

Modified PROMISE criteria for standardized interpretation of gastrin-releasing peptide receptor (GRPR)-targeted PET.

There are image interpretation criteria to standardize reporting prostate-specific membrane antigen (PSMA)-targeted positron emission tomography (PET). As up to 10% of prostate cancer (PC) do not express PSMA, other targets such as gastrin-releasing peptide receptor (GRPR) are evaluated. Research on GRPR-targeted imaging has been slowly increasing in usage at staging and biochemical recurrence (BCR) of PC. We therefore propose a modification of the Prostate Cancer Molecular Imaging Standardized Evaluation (PROMISE) criteria (mPROMISE) for GRPR-targeted PET. [68Ga]Ga-RM2 PET data from initially prospective studies performed at our institution were retrospectively reviewed: 44 patients were imaged for staging and 100 patients for BCR PC. Two nuclear medicine physicians independently evaluated PET according to the mPROMISE criteria. A third expert reader served as standard reference. Interreader reliability was computed for GRPR expression, prostate bed (T), lymph node (N), skeleton (Mb), organ (Mc) metastases, and final judgment of the scan. The interrater reliability for GRPR PET at staging was moderate for GRPR expression (0.59; 95% confidence interval [CI] 0.40, 0.78), substantial for T-stage (0.78; 95% CI 0.63, 0.94), and almost perfect for N-stage (0.97; 95% CI 0.92, 1.00) and final judgment (0.92; 95% CI 0.82, 1.00). The interreader agreement at BCR showed substantial agreement for GRPR expression (0.70; 95% CI 0.59, 0.81) and final judgment (0.65; 95% CI 0.53, 0.78), while almost perfect agreement was seen across the major categories (T, N, Mb, Mc). Acceptable performance of the mPROMISE criteria was found for all subsets when compared to the standard reference. Interpreting GRPR-targeted PET using the mPROMISE criteria showed its reliability with substantial or almost perfect interrater agreement across all major categories. The proposed modification of the PROMISE criteria will aid clinicians in decreasing the level of uncertainty, and clinical trials to achieve uniform evaluation, reporting, and comparability of GRPR-targeted PET. Clinicaltrials.gov Identifier: NCT03113617 and NCT02624518.

MT1 Challenges and Opportunities with Quantifying Comprehensive Health Economics of Diagnostic Imaging Modalities Using Radiopharmaceuticals: A Case Study in Coronary Artery Disease

The value of diagnostic tests often focuses on their performance (i.e., sensitivity, specificity, accuracy) and endpoints relevant for clinicians. As such, this presents an opportunity to design HEOR models to comprehensively quantify both short- and long-term outcomes derived from diagnostic procedures to improve the decision making process related with diagnostics tests. This research was designed to inform the development of a HEOR model framework to evaluate positron emission tomography (PET) and single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) modalities using radiopharmaceuticals, for coronary artery disease (CAD), incorporating short- and long-term perspectives.

Non-Invasive Imaging Modalities in Intravesical Murine Models of Bladder Cancer

Bladder cancer (BCa) is the sixth most prevalent cancer in men and seventeenth most prevalent cancer in women worldwide. Current treatment paradigms have limited therapeutic impact, suggesting an urgent need for the investigation of novel therapies. To best emulate the progression of human BCa, a pre-clinical intravesical murine model is required in conjunction with existing non-invasive imaging modalities to detect and evaluate cancer progression. Non-invasive imaging modalities reduce the number of required experimental models while allowing for longitudinal studies of novel therapies to investigate long-term efficacy. In this review, we discuss the individual and multi-modal use of non-invasive imaging modalities; bioluminescence imaging (BLI), micro-ultrasound imaging (MUI), magnetic resonance imaging (MRI), and positron emission tomography (PET) in BCa evaluation. We also provide an update on the potential and the future directions of imaging modalities in relation to intravesical murine models of BCa.

Utilization of Radiotherapy in Pediatric Hodgkin Lymphoma after ABVD: A Systematic Review

<h3>Purpose/Objective(s)</h3> Doxorubicin/hydroxydaunorubicin, bleomycin, vinblastine and dacarbazine (ABVD) chemotherapy with or without radiotherapy (RT) is widely used for the management of adult Hodgkin lymphoma (HL); however, data are more limited for pediatric HL (pHL). The use of RT in conjunction with ABVD in pHL is even more uncertain. Considering the ABVD backbone is currently being used in several North American cooperative group studies that include pHL, and that many Latin America centers commonly use ABVD outside a clinical trial, we conducted a systematic review of studies to inform us about the role of RT following ABVD in pHL. <h3>Materials/Methods</h3> A PubMed search was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Articles in English reporting survival outcomes, by risk group, of pediatric patients treated with ABVD ± RT were analyzed. Data were arranged by study design, patient age range, number of patients, risk group, number of ABVD cycles, response assessment with computed tomography (CT) and/or positron emission tomography (PET), RT approach, and survival outcomes. Results were stratified by risk group. <h3>Results</h3> The PubMed search generated 89 abstracts. 7 articles met inclusion criteria. Outcomes for both limited (low- and intermediate-risk groups) and advanced (high-risk group) disease were each specified in 6 articles. Chemotherapy consisted of 4-6 cycles in limited disease, and mostly 6 cycles in advanced disease. RT indications and interim imaging were heterogeneous. For limited disease: 2 studies recommended RT for all patients; 1 only if slow or incomplete response (PET evaluation); 1 if slow or incomplete response for adolescents and young adults, or incomplete response for children (PET or CT); 1 if bulky disease or slow response (PET or CT); and 1 if incomplete response. For advanced disease: 1 study reported RT in all patients; 1 only if bulky disease; 1 if incomplete response; 1 if slow or incomplete response (PET); 1 if bulky disease or slow response (PET or CT); and 1 did not use RT for stages IIIA2 to IV after 8 cycles of ABVD, but did use RT in stages IIIA1 after 6 cycles. Radiation doses ranged between 20 and 40 Gy. Event-free survival (EFS) and overall survival (OS) at 4-10 years ranged from 84%-100%, and 93%-100% in limited disease. In patients with advanced disease, EFS ranged from 50%-84.4% and OS from 75%-95.3%. In studies where a limited RT approach was used, RT was used between 9% and 40% of patients. <h3>Conclusion</h3> Based on the systematic review of pHL treated with ABVD ± RT, the data suggest that RT may be safely limited to cases of slow or incomplete response. This approach could spare RT for more than half of patients and still achieve favorable outcomes, particularly for those with limited-stage disease. More prospective pediatric trials with ABVD are needed to define the optimal RT strategy in pHL worldwide and with imaging availability in mind.

PET2 response associated with survival in newly diagnosed diffuse large B-cell lymphoma: results of two independent prospective cohorts

Studies evaluating Positron Emission Tomography scan after 2 cycles of chemotherapy (PET2) in newly diagnosed diffuse large B cell lymphoma (DLBCL) are heterogeneous in patient characteristics, treatments and have conflicting results. Here we report association of PET2 with outcomes in two large independent prospective cohorts of newly diagnosed DLBCL pts treated with two RCHOP-based regimens. The discovery cohort consisted of pts enrolled in single arm phase 2 MC078E study of lenalidomide with RCHOP (R2CHOP). The validation cohort consisted of RCHOP-treated pts from the Molecular Epidemiology Resource (MER) cohort. Pts who received 3-6 cycles of therapy and had PET2 were included in the study. Patients who progressed on PET2 were excluded. Revised response criteria 2007 were used to define PET2 response PET2 positive (PET2 + ) pts had inferior EFS [24-month EFS 45.5% vs 87.9%, HR 4.0, CI95 (2.1–7.9), p < 0.0001) with a trend towards lower OS [24-months OS 77% vs 94.8%, HR 2.0, CI95 (0.9–4.8), P = 0.1] than PET2 negative (PET2−) pts in MC078E cohort. PET2 + pts had an inferior EFS (24 month EFS 48.7% vs 81.6%, HR 2.9, CI95 2.0–4.2, p < 0.0001) and OS (24-month OS 68.6% vs 88.1%, HR 2.3, CI95: 1.5–3.5, p < 0.0001) in the MER cohort. These results were consistent regardless of age, sex and in the subgroup of advanced stage and high-risk international prognostic index (IPI). For MER, PET2 + pts also had higher odds of positive end of treatment PET (OR: 17.3 (CI95 7.9–37.7), p < 0.001). PET2 is an early predictor DLBCL pts at high risk of progression and death in two independent prospective cohorts. PET2-guided risk-adapted strategies may improve outcomes, and should be explored in clinical trials.

Underdiagnosis of cardiac sarcoidosis by ECG and echocardiography in cases of extracardiac sarcoidosis

BackgroundAlthough screening with 12-lead electrocardiography and transthoracic echocardiography for cardiac involvement has been recommended for patients with biopsy-proven extracardiac sarcoidosis, cardiac sarcoidosis has been reported even in patients with normal electrocardiography and echocardiography findings. We investigated the prevalence and characteristics of these patient cohorts.MethodsWe studied 112 consecutive patients (age, 55±17 years, 64% females) with biopsy-proven extracardiac sarcoidosis who had undergone 18F-fluorodeoxyglucose positron emission tomography and cardiac magnetic resonance imaging for cardiac sarcoidosis evaluation. The patients were categorised as those showing normal findings both in electrocardiography and transthoracic echocardiography (normal group) and those showing abnormal findings in one or both examinations (abnormal group).Results33 (29%) and 79 (71%) patients were categorised into the normal and abnormal groups, respectively, of which 6 (18%) and 43 (54%) patients, respectively, were diagnosed with cardiac sarcoidosis (p<0.01). Of these six patients in the normal group, two with multiple-organ sarcoidosis showed clinical deterioration of cardiac involvement and required steroid therapy; three with small cardiac involvement showed natural remission over follow-up assessments; and one underwent steroid therapy and showed an improvement in the left ventricular ejection fraction to within normal limits.ConclusionsThe prevalence of cardiac sarcoidosis in patients with biopsy-proven extracardiac sarcoidosis and normal electrocardiography and transthoracic echocardiography findings was ∼20%. Electrocardiography and transthoracic echocardiography may not detect cardiac sarcoidosis in patients without conduction and morphological abnormalities. However, some of these patients may subsequently show clinically manifested cardiac sarcoidosis. Physicians should be mindful of this population.

Utility of 18F‐fluorodeoxyglucose positron emission tomography in presurgical evaluation of patients with epilepsy: A multicenter study

18F-Fluorodeoxyglucose positron emission tomography (FDG-PET) is widely used in presurgical assessment in patients with drug-resistant focal epilepsy (DRE) if magnetic resonance imaging (MRI) and scalp electroencephalography (EEG) do not localize the seizure onset zone or are discordant. In this multicenter, retrospective observational cohort study, we included consecutive patients with DRE who had undergone FDG-PET as part of their presurgical workup. We assessed the utility of FDG-PET, which was defined as contributing to the decision-making process to refer for resection or intracranial EEG (iEEG) or to conclude surgery was not feasible. We included 951 patients in this study; 479had temporal lobe epilepsy (TLE), 219 extratemporal epilepsy (ETLE), and 253 epilepsy of uncertain lobar origin. FDG-PET showed a distinct hypometabolism in 62% and was concordant with ictal EEG in 74% in TLE and in 56% in ETLE (p<.001). FDG-PET was useful in presurgical decision-making in 396 patients (47%) and most beneficial in TLE compared to ETLE (58% vs. 44%, p=.001). Overall, FDG-PET contributed to recommending resection in 78 cases (20%) and iEEG in 187 cases (47%); in 131 patients (33%), FDG-PET resulted in a conclusion that resection was not feasible. In TLE, seizure-freedom 1year after surgery did not differ significantly (p=.48) between patients with negative MRI and EEG-PET concordance (n=30, 65%) and those with positive MRI and concordant EEG (n=46, 68%). In ETLE, half of patients with negative MRI and EEG-PET concordance and three quarters with positive MRI and concordant EEG were seizure-free postsurgery (n=5 vs. n=6, p=.28). This is the largest reported cohort of patients with DRE who received presurgical FDG-PET, showing that FDG-PET is a useful diagnostic tool. MRI-negative and MRI-positive cases with concordant FDG-PET results (with either EEG or MRI) had a comparable outcome after surgery. These findings confirm the significance of FDG-PET in presurgical epilepsy diagnostics.

18F-fluorodeoxyglucose positron emission tomography / computed tomography in primary Ewing sarcoma of the lung

Introduction. Ewing sarcoma is rare in medical practice, and evaluating positron emission tomography / computed tomography (PET/CT) imaging of soft tissue Ewing sarcoma is a challenge. Primary Ewing sarcoma of the lung is an infrequent diagnosis. Case outline. A 22-year-old female patient was sent for PET/CT examination to the Center for Nuclear Medicine with Positron Emission Tomography, of the University Medical Center of Serbia, with a referral diagnosis of primary Ewing sarcoma of the right lung. In parallel to tumor visualization, the PET/CT imaging showed a radiological entity named ?kissing sign,? due to an enlarged beaver tail liver. Conclusion. According to the concept of functional mimicry and tissue specificity of molecular markers, a better understanding of the molecular mechanisms of soft tissue Ewing sarcoma is the challenge. These observations can be the platform for further investigation of new therapeutic regimens.

Evaluation of 10-minute post-injection 11C-PiB PET and its correlation with 18F-FDG PET in older adults who are cognitively healthy, mildly impaired, or with probable Alzheimer's disease.

Objective:Positron emission tomography (PET) allows in vivo evaluation of molecular targets in neurodegenerative diseases, such as Alzheimer’s disease. Mild cognitive impairment is an intermediate stage between normal cognition and Alzheimer-type dementia. In vivo fibrillar amyloid-beta can be detected in PET using [11C]-labeled Pittsburgh compound B (11C-PiB). In contrast, [18F]fluoro-2-deoxy-d-glucose (18F-FDG) is a neurodegeneration biomarker used to evaluate cerebral glucose metabolism, indicating neuronal injury and synaptic dysfunction. In addition, early cerebral uptake of amyloid-PET tracers can determine regional cerebral blood flow. The present study compared early-phase 11C-PiB and 18F-FDG in older adults without cognitive impairment, amnestic mild cognitive impairment, and clinical diagnosis of probable Alzheimer’s disease.Methods:We selected 90 older adults, clinically classified as healthy controls, with amnestic mild cognitive impairment, or with probable Alzheimer’s disease, who underwent an 18F-FDG PET, early-phase 11C-PiB PET and magnetic resonance imaging. All participants were also classified as amyloid-positive or -negative in late-phase 11C-PiB. The data were analyzed using statistical parametric mapping.Results:We found that the probable Alzheimer’s disease and amnestic mild cognitive impairment group had lower early-phase 11C-PiB uptake in limbic structures than 18F-FDG uptake. The images showed significant interactions between amyloid-beta status (negative or positive). However, early-phase 11C-PiB appears to provide different information from 18F-FDG about neurodegeneration.Conclusions:Our study suggests that early-phase 11C-PiB uptake correlates with 18F-FDG, irrespective of the particular amyloid-beta status. In addition, we observed distinct regional distribution patterns between both biomarkers, reinforcing the need for more robust studies to investigate the real clinical value of early-phase amyloid-PET imaging.

Evaluation of attenuation correction in PET/MRI with synthetic lesion insertion.

Purpose: One major challenge facing simultaneous positron emission tomography (PET)/ magnetic resonance imaging (MRI) is PET attenuation correction (AC) measurement and evaluation of its accuracy. There is a crucial need for the evaluation of current and emergent PET AC methodologies in terms of absolute quantitative accuracy in the reconstructed PET images. Approach: To address this need, we developed and evaluated a lesion insertion tool for PET/MRI that will facilitate this evaluation process. This tool was developed for the Biograph mMR and evaluated using phantom and patient data. Contrast recovery coefficients (CRC) from the NEMA IEC phantom of synthesized lesions were compared to measurements. In addition, SUV biases of lesions inserted in human brain and pelvis images were assessed from PET images reconstructed with MRI-based AC (MRAC) and CT-based AC (CTAC). Results: For cross-comparison PET/MRI scanners AC evaluation, we demonstrated that the developed lesion insertion tool can be harmonized with the GE-SIGNA lesion insertion tool. About CRC curves difference between simulation and measurement was achieved. An average of 1.6% between harmonized simulated CRC curves obtained with mMR and SIGNA lesion insertion tools was achieved. A range of to 12% MRAC to CTAC SUV bias was respectively achieved in the vicinity and inside bone tissues in patient images in two anatomical regions, the brain, and pelvis. Conclusions: A lesion insertion tool was developed for the Biograph mMR PET/MRI scanner and harmonized with the SIGNA PET/MRI lesion insertion tool. These tools will allow for an accurate evaluation of different PET/MRI AC approaches and permit exploration of subtle attenuation correction differences across systems.

CXCR4 PET/MRI for follow-up of gastric mucosa–associated lymphoid tissue lymphoma after first-line Helicobacter pylori eradication

AbstractPosttreatment evaluation of gastric mucosa-associated lymphoid tissue (MALT) lymphoma currently relies on esophagogastroduodenoscopy with histological assessment of biopsies. Overexpression of the G protein–coupled C-X-C chemokine receptor type 4 (CXCR4) has been previously observed in MALT lymphoma. The aim of this prospective study was to evaluate positron emission tomography (PET) with the novel CXCR4 tracer [68Ga]Pentixafor as a potential alternative to follow up biopsies for assessment of residual disease (noncomplete remission [CR]) after first-line Helicobacter pylori eradication. Forty-six post–H pylori eradication [68Ga]Pentixafor–PET/magnetic resonance imaging (MRI) examinations of 26 gastric MALT lymphoma patients, and 20 [68Ga]Pentixafor–PET/MRI examinations of 20 control group patients without lymphoma, were analyzed. In the MALT lymphoma group, time-matched gastric biopsies were used as reference standard and showed CR in 6 cases. Pooled examination-based accuracy, sensitivity, specificity, and positive and negative predictive values of [68Ga]Pentixafor–PET for detection of residual gastric MALT lymphoma at follow-up were 97.0%, 95.0%, 100.0%, 100.0%, and 92.9%, respectively. Maximum and mean PET standardized uptake values showed moderate correlation with immunohistochemistry-based CXCR4+ cell counts, with correlation coefficients of r = 0.51 and r = 0.52 (P = .008 and P = .006). In summary, CXCR4 imaging with [68Ga]Pentixafor–PET may represent a promising test for assessment of residual gastric MALT lymphomas after H pylori eradication.

Synthesis and characterization of the radiopharmaceutical [18F]fluoroestradiol

[18F]Fluoroestradiol ([18F]FES), an estrogen analog, may be used in Positron Emission Tomography (PET) for evaluation of the tumor cell receptor profile in a noninvasive way, which is an important factor for determining the therapy to be used, disease staging, prognosis and response to therapy in breast cancer. [18F]FES is a new radiopharmaceutical and does not have an official monograph in any pharmacopeia until now. Therefore, the objective of this work was the optimization of the [18F]FES automatic synthesis and the elaboration of an analytical protocol for final product analyses. Initially, the synthesis of [18F]FES was performed according to a modified commercial protocol, using a TracerLab MXFDG synthesis module specific for [18F]FES synthesis. New protocols for the physicochemical quality control assays of the radiopharmaceutical were developed, including pH, chemical purity, residual solvents, radiochemical identity and purity. Physicochemical and microbiological analysis were performed with the synthesized [18F]FES at different time points to evaluate its stability. The uncorrected synthesis yield was 18.37 ± 3.07 %. All Quality Control methodologies proved to be effective for the product. The physicochemical and microbiological results obtained in the stability study showed that [18F]FES is stable during 8 hours after its synthesis, even under stress conditions. At the end of the study, it was concluded that the [18F]FES complies with all specifications required for a radiopharmaceutical intended for diagnostic use.

11C]meta-hydroxyephedrine PET evaluation in experimental pulmonary arterial hypertension: Effects of carvedilol of right ventricular sympathetic function

BackgroundLittle is known about the sequelae of chronic sympathetic nervous system (SNS) activation in patients with pulmonary arterial hypertension (PAH) and right heart failure (RHF). We aimed to, (1) validate the use of [11C]-meta-hydroxyephedrine (HED) for assessing right ventricular (RV) SNS integrity, and (2) determine the effects of β-receptor blockade on ventricular function and myocardial SNS activity in a PAH rat model. MethodsPAH was induced in male Sprague-Dawley rats (N = 36) using the Sugen+chronic hypoxia model. At week 5 post-injection, PAH rats were randomized to carvedilol (15 mg·kg−1·day−1 oral; N = 16) or vehicle (N = 16) for 4 weeks. Myocardial SNS function was assessed with HED positron emission tomography(PET). ResultsWith increasing PAH disease severity, immunohistochemistry confirmed selective sympathetic denervation within the RV and sparing of parasympathetic nerves. These findings were confirmed on PET with a significant negative relationship between HED volume of distribution(DV) and right ventricular systolic pressure (RVSP) in the RV (r = −0.90, p = 0.0003). Carvedilol did not reduce hemodynamic severity compared to vehicle. RV ejection fraction (EF) was lower in both PAH groups compared to control (p < 0.05), and was not further reduced by carvedilol. Carvedilol improved SNS function in the LV with significant increases in the HED DV, and decreased tracer washout in the LV (p < 0.05) but not RV. ConclusionsPAH disease severity correlated with a reduction in HED DV in the RV. This was associated with selective sympathetic denervation. Late carvedilol treatment did not lead to recovery of RV function. These results support the role of HED imaging in assessing SNS innervation in a failing right ventricle.

Microsleep disturbances are associated with noradrenergic dysfunction in Parkinson's disease.

Parkinson's disease (PD) commonly involves degeneration of sleep-wake regulating brainstem nuclei; likewise, sleep-wake disturbances are highly prevalent in PD patients. As polysomnography macroparameters typically show only minor changes in PD, we investigated sleep microstructure, particularly cyclic alternating pattern (CAP), and its relation to alterations of the noradrenergic system in these patients. We analyzed 27 PD patients and 13 healthy control (HC) subjects who underwent overnight polysomnography and 11C-MeNER positron emission tomography for evaluation of noradrenaline transporter density. Sleep macroparameters, as well as CAP metrics, were evaluated according to the consensus statement from 2001. Statistical analysis comprised group comparisons and correlation analysis of CAP metrics with clinical characteristics of PD patients as well as noradrenaline transporter density. PD patients and HC subjects were comparable in demographic characteristics (age, sex, body mass index) and polysomnography macroparameters. CAP rate as well as A index differed significantly between groups, with PD patients having a lower CAP rate (46.7 ± 6.6% versus 38.0 ± 11.6%, p = 0.015) and lower A index (49.0 ± 8.7/hour versus 40.1 ± 15.4/hour, p = 0.042). In PD patients, both CAP metrics correlated significantly with diminished noradrenaline transporter density in arousal prompting brainstem nuclei (locus coeruleus, raphe nuclei) as well as arousal propagating brain structures like thalamus and bitemporal cortex. Sleep microstructure is more severely altered than sleep macrostructure in PD patients and is associated with widespread dysfunction of the noradrenergic arousal system.

Quantitative Evaluation of 18F-Flutemetamol PET in Patients With Cognitive Impairment and Suspected Alzheimer's Disease: A Multicenter Study.

Background: In clinical practice, equivocal findings are inevitable in visual interpretation of whether amyloid positron emission tomography (PET) is positive or negative. It is therefore necessary to establish a more objective quantitative evaluation method for determining the indication for disease-modifying drugs currently under development.Aims: We aimed to determine cutoffs for positivity in quantitative analysis of 18F-flutemetamol PET in patients with cognitive impairment and suspected Alzheimer's disease (AD). We also evaluated the clinical efficacy of amyloid PET in the diagnosis of AD. This study was registered in the Japan Registry of Clinical Trials (jRCTs, 031180321).Methods: Ninety-three patients suspected of having AD underwent 18F-flutemetamol PET in seven institutions. A PET image for each patient was visually assessed and dichotomously rated as either amyloid-positive or amyloid-negative by two board-certified nuclear medicine physicians. If the two readers obtained different interpretations, the visual rating was rerun until they reached consensus. The PET images were quantitatively analyzed using the standardized uptake value ratio (SUVR) and standardized Centiloid (CL) scale with the whole cerebellum as a reference area.Results: Visual interpretation obtained 61 positive and 32 negative PET scans. Receiver operating characteristic analysis determined the best agreement of quantitative assessments and visual interpretation of PET scans to have an area under curve of 0.982 at an SUVR of 1.13 and a CL of 16. Using these cutoff values, there was high agreement between the two approaches (kappa = 0.88). Five discordant cases had SUVR and CL values ranging from 1.00 to 1.22 and from 1 to 26, respectively. In these discordant cases, either diffuse or mildly focal elevation of cortical activity confused visual interpretation. The amyloid PET outcome significantly altered the diagnosis of AD (χ2 = 51.3, p < 0.0001). PET imaging elevated the proportions of the very high likelihood category from 20.4 to 46.2% and the very low likelihood category from 0 to 22.6%.Conclusion: Quantitative analysis of amyloid PET using 18F-flutemetamol can objectively evaluate amyloid positivity using the determined cutoffs for SUVR and CL. Moreover, amyloid PET may have added value over the standard diagnostic workup in dementia patients with cognitive impairment and suspected AD.

PET evaluation of light-induced modulation of microglial activation and GLP-1R expression in depressive rats

Light therapy has been accepted as a promising therapeutic choice for depression. Positron emission tomography (PET) combined with specific radiotracers has great benefits for revealing pathogenesis and developing therapeutics. This study aimed to investigate the influences of light therapy on microglial activation and glucagon-like peptide-1 receptor (GLP-1R) expression in the brain of depressive rats using [18F]DPA-714 and [18F]exendin-4 PET. The results showed that chronic unpredictable mild stress (CUMS)-induced depressive rats had poorer performance in behavioral tests compared to normal rats (p < 0.05) and the depressive-like behavior could be ameliorated by light therapy. Besides, depressive rats had significantly higher [18F]DPA-714 uptake and lower [18F]FDG uptake compare to normal rats in 11 and 9 regions of interest (ROIs) of the brain, respectively (p < 0.05). After 5 weeks of light therapy, higher [18F]FDG and [18F]exendin-4 uptake was observed in most ROIs of light therapy-treated depressive rats compared to untreated depressive rats (p < 0.05) and no significant differences existed in [18F]DPA-714 uptake between the two groups. This study demonstrated that light therapy can ameliorate depressive-like behavior, improve glucose metabolism, and halt the decline of brain GLP-1R expression of depressive rats, but have no effects on microglial activation caused by CUMS. Besides, this study validated that [18F]DPA-714 and [18F]exendin-4 PET have the potential for noninvasive evaluation of microglial activation and GLP-1R expression in the brain of depression.

NIMG-12. 18F-FLUORETHYLTYROSINE POSITRON EMISSION TOMOGRAPHY VERSUS MAGNETIC RESONANCE SPECTROSCOPY IN PREOPERATIVE DETECTION OF NEWLY DIAGNOSED GLIOMAS BY USING MACHINE LEARNING

Abstract BACKGROUND Advanced imaging techniques entered the field of neurooncology. In this analysis we compare the diagnostic potential of 18F-fluorethyltyrosine (FET) positron emission tomography (PET) and magnetic resonance spectroscopy (MRS) in their potential to preoperatively predict certain glioma subtypes. AIMS Goal of this analysis ist the evaluation of FET PET and MRS regarding the preoperative prediction of glioma subtypes. METHODS We analyzed 33 patients with histopathologically confirmed newly diagnosed glioma. The patients received FET PET and MRS during one single preoperative diagnostic session. According to the molecular portfolio patients were subdivided in IDH wildtype glioblastoma patients (GBM), IDH wildtype WHO grade II/III glioma patients (Astro_IDHwt), IDH mutant WHO grade II/III glioma patients without 1p/19q codeletion (Astro_IDHmut) and with 1p/19q codeletion (ODG). Mean and maximum tumor-to-brain ratio (TBRmean and TBRmax), N-acetylaspartate, choline and creatine peaks were correlated with postoperative tumor diagnosis. To gain generalizable implications we subdivided the study cohort into a development and validation subcohort. A support vector machine model was fitted to the development subcohort and evaluated on the validation subcohort. Receiver operating characteristic curve served to assess model performance. RESULTS GBM patients had highest TBRmax and TBRmean values (mean: 3.5 and 3.8) and the ODG patients showed the second highest TBRmax and TBRmean values (mean: 2.6 and 3). The distribution of MRS markers exhibited to clear trend. The performance of glioma subtyping was comparatively low for the TBR values (AUC: 0.68) and even lower for the MRS markers (AUC: 0.60). These results are in line with preliminary investigations performed by our institute for the comparison of 11C-methionine PET with MRS in preoperative glioma subtyping. CONCLUSIONS FET PET and MRS bear limited potential in glioma subgrouping. However, FET PET appears to be slightly superior. Investigation in a larger cohort is required to draw definite conclusions.

Prognostic Impact of Metabolic Tumor Burden in Large B-Cell Lymphoma Patients Receiving CAR T-Cell Therapy

Introduction Chimeric antigen receptor (CAR) T-cell therapy provides long-term remissions in a substantial proportion of patients with large B-cell lymphoma (LBCL) who have relapsed or are refractory (R/R) to chemoimmunotherapy. The identification of prognostic factors to identify which patients will benefit most from this therapy is crucial to improve patient selection. Even though metabolic tumor burden assessed by 18F-fluorodeoxyglucose Positron Emission Tomography (PET) has a confirmed prognostic value in the setting of chemoimmunotherapy, its predictive role after CAR T-cell therapy is not established. Methods We conducted a single-center study including all patients with R/R LBCL who received a single infusion of CD19-targeted second-generation CAR T-cells carrying a 4-1BB costimulatory domain from July 2018 to January 2020. Adverse events were graded according to the American Society for Transplantation and Cellular Therapy (ASTCT) consensus. All patients underwent a baseline PET scan and metabolic disease evaluation after infusion. Disease response assessment was conducted according to Lugano criteria. Metabolic tumor volume (MTV) and maximum standardized uptake value (SUVmax) were measured at baseline and at 1-month after CAR T-cell infusion, and correlated with disease response and development of adverse events. To identify the optimal cut-offs for metabolic parameters we used the maximally selected log-rank statistics in the PFS analysis. Results Thirty-five consecutive patients with R/R LBCL who received CAR T-cell therapy were included in the study. Patients' baseline characteristics are summarized in Table 1. Median age at treatment was 58 years, and 74% were males. At the time of diagnosis most of them had an advanced stage of disease (86%) and were refractory to the last therapy (n=31, 88%). Best response after CAR T-cell therapy included 9 (26%) patients in complete remission (CR) and 16 (46%) in partial remission (PR). Ten (28%) patients were in progressive disease (PD) at the 1-month disease evaluation. At a median follow-up of 7.6 months, median PFS and OS were 3.4 months and 8.2 months, respectively. Regarding toxicity, eleven (31%) patients developed clinically significant CAR T-cell related toxicity, defined as grade 2 or higher CRS (n=7, 20%) and grade 2 or higher ICANS (n=6, 17%). Median baseline MTV and MTV41% were 270 cm3(IQR 87-875) and 119 cm3 (IQR 32-300), respectively. Median SUVmax was 24 (IQR 17-32). Patients who responded (CR and PR) had lower baseline MTV values compared with non-responders (median of 228 cm3 vs 645 cm3, p=0.04) (Figure 1a). No association was found between MTV41% or SUVmax and disease response. In terms of PFS, a high baseline MTV (&amp;gt;82 cm3) was associated with a lower PFS compared to patients with lower MTV values (median PFS, 2.1 months vs. 6 months; HR 3.15, p= 0.02) (Table 2 and Figure 2). Patients with high baseline MTV41% values (&amp;gt;25 cm3) also had an inferior PFS (HR 3.44, p= 0.02); no association was found between baseline SUVmax and PFS (Table 2). As per OS, there was no significant association with baseline MTV, MTV41% and SUVmax (Table 2). Regarding toxicity, there was no significant association between baseline MTV, MTV 41% and SUVmax values with grade 2 or higher CRS and ICANS events (Figure 1b). All patients underwent a 1-month post-infusion PET evaluation. Disease response at this timepoint was: CR in 8 patients (23%), PR in 17 patients (49%) and PD in 10 patients (28%). For patients in CR and PR at 1-month the probability of PFS at 6 months was 62.5% and 12.7%, respectively (HR=3.89, p=0.02). For patients in PR at the 1-month evaluation, MTV values at that timepoint were predictive for PFS; patients in PR with low (&amp;lt;35 cm3) and high 1-month MTV values had a 6m-PFS of 33% and 0%, respectively (Figure 3)(HR=4.6, p = 0.01). In these patients, SUVmax values also predicted PFS and a trend towards significance was observed for MTV41% (HR=3, p=0.07). Conclusion Metabolic tumor burden parameters measured by 18FDG-PET before and 1-month after CAR-T cell infusion identify LBCL patients who benefit most from these therapies and could aid patient selection. Disclosures Iacoboni: Novartis, Gilead, Celgene, Roche: Honoraria. Villacampa:AstraZeneca: Other: advisory role; Merck Sharp &amp; Dohme: Honoraria. Abrisqueta:AbbVie: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Honoraria, Speakers Bureau; Celgene: Consultancy, Honoraria; Roche: Consultancy, Honoraria, Speakers Bureau. Bosch:Hoffmann-La Roche: Research Funding. Barba:Novartis, Celgene, Gilead, Pfizer, Amgen, Roche: Honoraria.