Emission Tomography Research Articles

Optical emission spectroscopy and imaging of low-pressure N2 plasmas generated by intense fast-pulsed electron beams

An optical emission spectroscopic (OES) and imaging characterization is conducted on N2 plasmas generated by a 100 keV fast-pulsed electron beam. The electron beams are injected into an N2 gas filled volume with a current of 4.5 kA (300 A/cm2) and a 100 ns pulse width. The characterization is conducted at the pressures, 1 Torr and 0.1 Torr, corresponding to two distinct regimes that exhibit significantly different plasma dynamics. Beam impact ionization is shown to be a primary mechanism for producing low temperature plasmas at 1 Torr during beam output. After beam termination, ionization by an inductive electric field becomes the primary mechanism for plasma formation later in time for both pressures. OES and plasma imaging are used in this work as a diagnostic tool to track the distribution of electronic, vibrational, and rotational state transitions and ionized species. This is achieved with the use of a multi-resolution suite of spectrometers capable of acquiring time-resolved spectra. Vibrational and rotational bands of the N2 second positive system (C3Πu→B3Πg) and the N2+ first negative system (B2Σu+→X2Σg+) are identified in both regimes as well as N+ states exclusively in the lower pressure regime. Vibrational and rotational spectra are shown to track the evolution of the time-varying plasma current. Plasma imaging also reveals spatially nonuniform plasma emission at 0.1 Torr. A few hundred shots are recorded to fully characterize the emissions, and results are shown to be highly reproducible (≤±1% with 2σ confidence).

Anisotropy in shear failure of shale: An insight from microcracking to macrorupture

Anisotropic shear failure in shale is crucial to wellbore instability and hydraulic fracturing. While previous studies have examined bedding angles ranging from 0° to 90°, the intermediate angles have not been thoroughly investigated, with limited quantitative analysis from microcracking to macrorupture. To address this gap, we conducted direct shear tests on cubic shale samples with seven bedding angles (α = 0°, 15°, 30°, 45°, 60°, 75°, and 90°) using an innovative combination of acoustic emission (AE) and digital image correlation (DIC) techniques. This approach allowed us to gain a comprehensive understanding of the cracking damage process from the interior to the surface. Under various normal stresses, the minimum peak shear strengths occurred at α = 0°, while the maximum values were observed at α = 45° or 60°, rather than remaining constant. The internal friction angle peaked at α = 45°, not at α = 30° as previously reported. Furthermore, the shear failure pattern was influenced by complex interactions among nominal shear plane, bedding structure, and normal stress. The primary strain concentration zones and microfractures formed not only along the nominal shear plane but also along the bedding planes. Notably, microcracking damage initiated most readily at α = 0°, where the b value in AE events was higher and the fractal dimension was lower. At α = 30°–60°, the b value reached its minimum, while the fractal dimension peaked. The more random distribution of larger-scale microcracks was associated with an increase in the shear strength. These findings provide critical insights into the anisotropy of shear failure in shale and demonstrate the potential of microcracking analysis in predicting critical macrorupture and shear resistance. The identification of three distinct shear failure mechanisms further enhances our understanding of shale anisotropy.

Radiological features of desmoid-type fibromatosis: a two-institution retrospective study.

To characterize the radiological findings of desmoid-type fibromatosis (DF). This two-institution retrospective study included 152 patients with pathologically confirmed DF who underwent computed tomography (CT), magnetic resonance imaging (MRI), or 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET)/CT between January 2001 and February 2024. Two board-certified radiologists independently evaluated the CT, MRI, and FDG-PET/CT findings, and a third board-certified radiologist resolved discrepancies. Imaging was performed with and without contrast media: 70 patients underwent plain CT, 95 underwent contrast-enhanced (CE) CT, 115 patients underwent plain MRI examinations, 100 patients underwent CE-MRI, and 11 patients underwent FDG-PET/CT (most patients underwent several modalities). The median age of the patients was 40 years, with a female predominance (male, 39.5% vs female, 60.5%). Swelling or palpable mass was the most frequent symptom (78/152, 51.3%). Gross total resection of DF was performed in 57 patients, with a recurrence rate of 38.6% (22/57). Tumors were most frequently observed in the extra-abdominal region (79/152, 51.6%). Characteristic radiological features included intermediate intensity on T2-weighted imaging (112/113, 99.1%), intermediate-to-high intensity on T1-weighted imaging (109/111, 98.2%), substantial enhancement in the late phase on MRI (100/100, 100%), moderate to strong enhancement in the late phase on CT (18/20, 90%), and arterial penetration sign on CE-CT (25/96, 26.0%). The mean apparent diffusion coefficient (ADC) of DFs was 1.46 × 10-3 mm2/s (range, 1.00-2.20). This study highlights the unique imaging features of DF, including the arterial penetration sign and high mean ADC values, which can aid in differentiating DF from other soft tissue tumors. These findings may improve preoperative diagnostic accuracy and reduce the need for invasive procedures. Question Imaging findings of DFare not well-documented in large-scale studies. Findings This study identifies unique imaging features of DF, such as the arterial penetration sign and high mean ADC values. Clinical relevance These distinctive imaging characteristics improve diagnostic accuracy for DF and lead to appropriate patient management, as DF requires distinct treatment strategies.

MIRD Pamphlet No. 32: A MIRD Recovery Coefficient Model for Resolution Characterization and Shape-Specific Partial-Volume Correction.

Accurate quantification in emission tomography is essential for internal radiopharmaceutical therapy dosimetry. Mean activity concentration measurements in objects with diameters less than 10 times the full width at half maximum of the imaging system's spatial resolution are significantly affected (>10%) by the partial-volume effect. This study develops a framework for PET and SPECT spatial resolution characterization and proposes 2 MIRD recovery coefficient models-a geometric mean approximation (RECOVER-GM) and an empirical model (RECOVER-EM)-that provide shape-specific partial-volume correction (PVC). The models were validated using simulations and phantom experiments, with a comparative PVC test on ellipsoidal phantoms demonstrating that the RECOVER models significantly reduced error in activity quantification by factors of approximately 1.3-5.7 compared with conventional sphere-based corrections. The proposed recovery coefficient models and PVC methodology provide a robust framework for improved region-based PVC, including corrections for nonspherical tumor volumes. This work is part of the ongoing MIRDsoft.org project that aims to enhance accessibility to advanced dosimetry tools for improved disease characterization, treatment planning, and radiopharmaceutical therapy dosimetry.

Modelling and validation of a 6 MV compact linear accelerator via Monte Carlo simulation using Geant4 Application for Tomographic Emission (GATE)

Objective. To accurately model and validate the 6 MV Elekta Compact linear accelerator using the Geant4 Application for Tomographic Emission (GATE). In particular, this study focuses on the precise calibration and validation of critical parameters, including jaw collimator positioning, electron source nominal energy, flattening filter geometry, and electron source spot size, which are often not provided in technical documentation.Methods. Simulation of the Elekta CompactTM6 MV linear accelerator was performed using the Geant4 Application for Tomographic Emission (GATE) v.9.1. A 50 cm×50 cm×50 cm water phantom was irradiated with a source-to-surface distance of 100 cm. Percentage Depth Dose Profile (PDD) and Lateral Dose Profile (Crossplane and Inplane) were assessed as reference dose measurements. The half-length field difference (FHLD) method was introduced to optimize the jaw collimator setup. Gamma index analysis was used to quantitatively assess the accuracy of the simulated dosimetry data in relation to the actual dose measurements.Results. Crucial parameters of the Linac Head have been successfully optimized. The validation achieved Gamma-Index acceptance rates of 97.93% for the Depth Dose profile, 100% for the Crossplane (X) Dose Profile, and 93.98% for the Inplane (Y) Dose Profile, all meeting the 1%/1 mm Gamma-Index criteria.Conclusion. The simulation and calibration of the Elekta Compact Linac have achieved a reliable model with high fidelity in dosimetry calculations which could pave the way for the future development and application of new techniques using Elekta CompactTMLinear Accelerator.

Estimation of dose to a bystander from F-18 FDG patients using Monte Carlo simulation in clinical exposure scenarios.

The radiation exposure to bystanders from nuclear medicine patients is a common concern raised in nuclear medicine departments. The GATE (Geant4 Application for Tomographic Emission) Monte Carlo radiation transport application was used to estimate the dose to a bystander. Two voxelised phantoms were utilised in a GATE Monte Carlo simulation as the radiation source and target. The absorbed dose to the target phantom from radiation emitted by the source phantom was calculated. Three experimental setups of increasing complexity, with the last one replicating clinical dose rate measurements, were used to validate the simulation results. Four clinical scenarios were simulated to estimate the dose to a healthcare worker from F-18 FDG patients: an ultrasound procedure, two surgical procedures (head and chest), and a face-to-face consultation. The mean absorbed dose to the foetus was also estimated using the same method and pregnant female phantoms as target for ultrasound scan scenario. The effective dose to a healthcare worker from an FDG PET patient who has had 250 MBq of FDG injection 3h post procedures was estimated as: 18.1 ± 0.1 µSv for 30-minute ultrasound scan, 36.5 ± 0.3 µSv for 1-hour chest surgical procedure, and 9.3 ± 0.1 µSv for 15-minute face to face consultation scenario. This method can be easily extended to estimate the dose to bystanders from nuclear medicine patients injected with various radioisotopes in different clinical scenarios.

Relation of Insulin Resistance to Brain Glucose Metabolism in Fasting and Hyperinsulinemic States: A Systematic Review and Meta-analysis.

Abnormal brain glucose metabolism may cause cognitive disease in type 2 diabetes, yet the relation between insulin resistance and brain glucose metabolism has not been systematically described. We evaluated the impact of metabolic condition (fasting vs insulin stimulation, eg, from hyperinsulinemic clamp) on the association between insulin resistance of different etiologies and brain glucose metabolism. PubMed, Embase, Cochrane Library, and Web of Science were systematically searched from inception until February 2022. Of 656 unique records, we deemed 31 eligible. Criteria were studies assessing brain glucose metabolism (uptake or metabolic rate) by 18F-2-fluoro-2-deoxy-D-glucose-positron emission tomography in individuals characterized by measures of or clinical proxies for insulin resistance (eg, type 2 diabetes and obesity). Two independent investigators extracted data and assessed study quality. We applied random-effects models to pool Hedge's g standardized mean differences. Insulin resistance was associated with decreased brain glucose metabolism during fasting [-0.47 SD, 95% confidence interval (CI): -0.73 to -0.22, P < .001, I2 = 71%] and increased metabolism during insulin stimulation (1.44 SD, 95% CI 0.79 to 2.09, P = .002, I2 = 43%). Contrary to type 2 diabetes and other insulin resistance-related conditions, obesity was not associated with brain hypometabolism in fasting states (0.29 SD, 95% CI -.81 to 1.39). Metabolic conditions modify associations between insulin resistance and brain glucose metabolism; ie, most individuals with insulin resistance display hypometabolism during fasting and hypermetabolism during insulin stimulation.

A Method for Estimating Fluorescence Emission Spectra from the Image Data of Plant Grain and Leaves Without a Spectrometer

This study proposes a method for estimating the spectral images of fluorescence spectral distributions emitted from plant grains and leaves without using a spectrometer. We construct two types of multiband imaging systems with six channels, using ordinary off-the-shelf cameras and a UV light. A mobile phone camera is used to detect the fluorescence emission in the blue wavelength region of rice grains. For plant leaves, a small monochrome camera is used with additional optical filters to detect chlorophyll fluorescence in the red-to-far-red wavelength region. A ridge regression approach is used to obtain a reliable estimate of the spectral distribution of the fluorescence emission at each pixel point from the acquired image data. The spectral distributions can be estimated by optimally selecting the ridge parameter without statistically analyzing the fluorescence spectra. An algorithm for optimal parameter selection is developed using a cross-validation technique. In experiments using real rice grains and green leaves, the estimated fluorescence emission spectral distributions by the proposed method are compared to the direct measurements obtained with a spectroradiometer and the estimates obtained using the minimum norm estimation method. The estimated images of fluorescence emissions are presented for rice grains and green leaves. The reliability of the proposed estimation method is demonstrated.

Synchronized acoustic emission and high-speed imaging of cavitation-induced atomization: The role of shock waves.

This study experimentally investigates the role of cavitation-induced shock waves in initiating and destabilizing capillary (surface) waves on a droplet surface, preceding atomization. Acoustic emissions and interfacial wave dynamics were simultaneously monitored in droplets of different liquids (water, isopropyl alcohol and glycerol), using a calibrated fiber-optic hydrophone and high-speed imaging. Spectral analysis of the hydrophone data revealed distinct subharmonic frequency peaks in the acoustic spectrum correlated with the wavelength of capillary waves, which were optically captured during the onset of atomization from the repetitive imploding bubbles. This finding provides the first direct evidence that the wavelength of the growing surface waves, which governs capillary instability resulting in droplet breakup, is linked to the periodicity of shock waves responsible for the onset of the subharmonic frequencies detected in the acoustic spectra. This work contributes to a deeper understanding of ultrasonic atomization, signifying the role of cavitation and shock waves in the atomization process.

A whole gamma imaging prototype for higher quantitative imaging of 89Zr-labeled antibodies in a tumor mouse model

Objective.Positron emission tomography (PET) has become an important clinical modality, but it is limited to imaging the annihilation radiation from positron-electron collisions. Recently, PET imaging with89Zr, which has a half-life of 3 d, has attracted much attention in immuno-PET to visualize immune cells and cancer cells by targeting specific antibodies on the cell surface. However,89Zr emits a single gamma ray at 909 keV four times more frequently than positrons, causing image quality (IQ) degradation in conventional PET. To overcome this drawback, use of such single gamma rays for imaging was previously proposed as whole gamma imaging (WGI). In WGI, a single gamma ray is detected by Compton imaging; by inserting a scatter detector ring inside the PET ring, WGI can realize both PET imaging and Compton imaging in one modality. A prototype for WGI was developed and Compton imaging of a mouse after intravenous administration of89Zr oxalate was demonstrated. However, the Compton imaging of the single gamma ray still presented a challenge due to its low IQ compared to PET.Approach.In this study, the scatter detector insert of the earlier WGI prototype was redesigned with the aim of improving Compton imaging performance. The new prototype produced WGI images by additive averaging of PET and Compton images after optimizing the ratio of each iteration in the image reconstruction. WGI IQ was then evaluated using the NEMA NU4 IQ phantom, and a tumor-burdened mouse was imaged with WGI up to 12 d after89Zr labeled antibody injection.Main results.Consequently, the Compton imaging performance was improved by lowering the angular resolution measure from 6.7 degrees to 6.4 degrees and the sensitivity from 0.11% to 0.18% compared to the previous prototype WGI. The phantom images with WGI showed a 15% reduction in noise and a 3% increase in contrast recovery under low-statistical conditions compared to images reconstructed by PET data alone.Significance. In-vivomouse imaging with the new prototype WGI was successfully performed. This successful imaging leads to the expectation that future whole-body WGI imaging will enable more sensitive and better quantitative89Zr antigen-antibody reaction imaging to be obtained.

The law of axial compressive damage of wood components with T-shaped and L-shaped cracks

ABSTRACT Wood components are easy to crack, which has great influence on their performance. So it is particularly essential to monitor and clarify the crack propagation law. In this paper, T- and L-shaped cracks were prefabricated on wood components, and acoustic emission (AE) and digital imaging correlation (DIC) technology were combined to monitor and analyse the damage of wood components under axial compression. The effects of different crack types on the damage forms, mechanical properties, damage index and propagation characteristics of acoustic emission signals were studied. It shows that the damage to L-cracked wood components was more serious than that of T-cracked wood and the acoustic emission signal strengthened as the load increased and the degree of rupture intensified. By establishing the corresponding relationship between the initiation and propagation behavior of wood microcracks and the acoustic emission parameters and surface strain, a measurement and evaluation system for in-situ monitoring the crack damage evolution of wood components with parallel and transverse cracks based on acoustic emission technology and digital image correlation method was successfully constructed. The test results provide a reference for further study on the damage mechanism and in-situ monitoring method of crack evolution behavior of wood with cracks.

Assessment of tissue-air ratios in epoxy resin and PMMA phantoms for radiation dosimetry: findings from experimental measurements and Monte Carlo simulations.

This study assesses radiation doses in multi-slice computed tomography (CT) using epoxy resin and PMMA phantoms, focusing on the relationship between TAR (tissue air ratio) and kilovoltage peak (kVp). The research was conducted using a Hitachi Supria 16-slice CT scanner. An epoxy resin phantom was fabricated from commercially available materials, to simulate human tissue. The phantom contained four peripheral inserts and one central insert for dose measurement, with optically stimulated luminescent dosimeters positioned at various depths (2 to 10cm). Monte Carlo simulations were executed using the Geant4 Application for Tomographic Emission toolkit (GATE) to model photon transport, with the x-ray spectrum generated using SpekPy software. A non-linear fitting model was developed to describe the TAR-kVp relationship across different depths for epoxy resin and PMMA. Results indicated that TAR values were higher at low depths (2cm) and decreased with increasing depth, reflecting the x-ray beam's attenuation. For instance, at 80 kVp and 2cm depth, the experimental TAR for PMMA was 1.102 ± 0.011, closely matching the MC simulation value of 1.110 ± 0.036, resulting in a small difference of 0.7%. At a depth of 10cm, the experimental TAR for PMMA decreased to 0.245 ± 0.006, while the MC TAR was 0.248 ± 0.016, with a relative difference of 1.2%. Similar trends were observed for epoxy resin, where the experimental TAR ranged from 1.070 ± 0.014 at 2cm to 0.235 ± 0.009 at 10cm, while MC simulation values ranged from 1.080 ± 0.038 to 0.238 ± 0.017. Bland-Altman analysis confirmed these results, with mean differences of 0.008 for PMMA and 0.006 for epoxy resin, indicating high agreement between the experimental and simulated TAR values. This study highlights the importance of phantom material selection in dose assessment and the implications of TAR in dose correction within the context of diagnostic radiology.

TSPO-PET in pre-surgical evaluations: Correlation of neuroinflammation and SEEG epileptogenicity mapping in drug-resistant focal epilepsy.

Resective surgery in drug-resistant focal epilepsy (DRFE) requires extensive evaluation to localize the epileptogenic zone (EZ). When non-invasive phase 1 assessments (electroencephalography, EEG; magnetic resonance imaging, MRI; and 18F-Fluorodeoxyglucose-positron emission tomography, [18F]FDG-PET) are inconclusive for EZ localization, invasive investigations such as stereo-EEG (SEEG) are necessary. Epileptogenicity maps (Ems) visualize the EZ using SEEG-identified ictal high-frequency oscillations (iHFOs). PET imaging with radioligands targeting the18-kDa translocator protein (TSPO), a marker of glial activation, may aid EZ localization. This study investigates the correlation between TSPO-PET imaging and SEEG iHFOs in DRFE to determine the utility of TSPO-PET in pre-surgical assessments, especially in complex or non-lesional cases. Patients with DRFE and inconclusive phase 1 assessments were recruited from Bicêtre Hospital (AP-HP) for a prospective study (Eudract 2017-003381-27). They underwent SEEG and [18F]DPA-714 (N,N-diethyl-2-(2-(4-(2-(fluoro-18F)ethoxy)phenyl)-5,7-dimethylpyrazolo[1,5-a]pyrimidin-3-yl)acetamide) (TSPO radioligand) PET imaging. Statistical parametric mapping (SPM) techniques analyzed significant [18F]DPA-714-PET uptake (TSPO-map) and generated epileptogenicity maps (EM-map). Correlation analyses at regional and voxel-of-interest (VOI) levels assessed the relationship between TSPO-map and EM-map. We were able to obtain and analyze both maps in 12 of 17 patients recruited. A significant positive correlation between EM-map and TSPO-map in focal epilepsies was found regionally (r = .81, p < .00004) and at the VOI level (r = .79, p < .00003). Temporal, insular, parietal, and occipital regions showed particularly strong correspondence. In frontal epilepsies, TSPO-map was more focal than EM-map, suggesting increased specificity for SEEG planning. This study also demonstrated the benefit of the TSPO-map in identifying multiple foci in multifocal epilepsies, with or without lesions. These findings suggest that neuroinflammation may be a molecular substrate of the EZ in non-lesional focal epilepsy. Identifying the EZ inpatients with complex DRFE and inconclusive MRI/[18F]FDG-PET imaging is essential to improve resective surgery outcomes. Combining TSPO-PET imaging with SEEG recordings may help bridge this gap.

A Literature Review on Oral Lumenoscopy: A Non-invasive Method for Diagnosing Oral Potentially Malignant Disorders.

Dentistry still faces difficulties in diagnosing oral precancer and cancer, especially when it comes to early phase changes ordisease detection, evaluation, and treatment. In essence, oral lumenography is the process of identifying oral lesions using a chemiluminescent light source and a toluidine blue labeling system. Since neoplastic epithelial cells have a changed nuclear-cytoplasmic ratio, acetic acid dehydration brings out this nuclear density and gives the tissue an "acetowhite" look. This phenomenon is further intensified when diffuse blue-white chemiluminescent illumination is created by using toluidine blue, which preferentially stains premalignant lesions, in place of ordinary lighting. In developing countries like India, oral cancer and other precancerous and malignant lesions of the oral cavity are very common. The most common diagnostic methods for oral mucosal lesions suggestive of malignancy or premalignancy are tissue samples and histological examination. There is a waiting period following this invasive operation before learning the diagnostic findings. Thus, the creation of a non-invasive screening instrument is required to detect oral cancer.Thus, the main goal of our work is to create a real-time, non-invasive diagnostic tool for oral cancer screening that is based on optical imaging methods like fluorescence emission imaging and diffuse reflectance imaging.To enhance clinical assessment and facilitate the diagnosis of premalignant and early-stage malignant lesions, numerous novel approaches have been developed. In this article, the purpose of a tissue reflectance-based analysis has been discussed. It is currently offered for sale under the ViziLite brand (Zila Pharmaceuticals, Phoenix, AZ, US) after being altered for usage in the oral cavity.

Imaging of amyloid, tau and synaptic dysfunction in the brains of type 2 diabetic rats ‐ a multitracer PET study

AbstractBackgroundType 2 diabetes mellitus (T2DM) is associated with a greater risk of Alzheimer's disease (AD). Synaptic impairment and protein aggregates have been reported in the brains of T2DM rodent models. Here, we assessed the changes in synaptic vesicle 2A (SV2A), amyloid‐β, and tau that are featured pathologies in AD in T2DM rats in vivo.MethodPositron emission tomography (PET) using [18F]SynVesT‐1 (SV2A), [18F]flumazenil (GABAA receptor), [18F]florbetapir (amyloid‐β), [18F]APN‐1607 (tau), was carried out in 12‐month‐old diabetic Zucker diabetic fatty (ZDF) and Sprague‒Dawley (SD) rats. Immunofluorescence staining as well as proteomic profiling and pathway analysis were performed on the brain tissues of ZDF and SD rats.ResultsReduced cortical [18F]SynVesT‐1 uptake were observed in 12‐month‐old ZDF rats compared to SD rats. No difference was observed in the [18F]florbetapir and [18F]APN‐1607 uptake in the brains of 12‐month‐old ZDF and SD rats. Immunofluorescence staining revealed Thioflavin S‐negative, phospho‐tau‐positive inclusions in the cortex and hypothalamus of ZDF rats, without amyloid‐beta deposits. Proteomic analysis further demonstrated downregulated synaptic‐related proteins pathways in the hippocampus of ZDF rats compared to SD rats.ConclusionThese findings provide in vivo evidence for synaptic impairment in the brains of aged T2DM ZDF rats.

Predicting cognitive function from multimodal mesoscale neuroimaging data

AbstractBackgroundOur objective was to assess individual and joint relationships between various mesoscale indicators of brain health (e.g., neuronal, metabolic, and vascular integrity) and cognitive function.MethodWe used 7224 timepoint measures originating from 1825 participants of the ADNI study who were cognitively healthy or with mild cognitive impairment at initial assessment. Cognitive function outcomes were test results on the Alzheimer’s Disease Assessment Scale–Cognitive Subscale (ADAS‐Cog), the Rey auditory Verbal Learning Test immediate recall (RAVLTi), the Rey auditory Verbal Learning Test delayed recall (RAVLTd), the Trail Making Test A (Trail a), and the Trail Making Test B (Trail b) tasks. Four families of markers were used. First were three families of mesoscale neuroimaging assessed by MRI for 88 brain regions: 1. Neuronal integrity was estimated by FreeSurfer 6.0 produced volumes extracted from T1‐weighted (T1w) images; 2. Neurite integrity was estimated through T1w/T2‐weighted MRI ratios; 3. Cerebral metabolism integrity was measured by synthetic fluorodeoxyglucose‐positron emission tomography, generated by a model based on a latent‐space regularized generative adversarial net from T1w MRIs. Secondly, 4. Systemic markers of vascular health‐related factors were included in the model (history of cardiovascular diseases, alcohol abuse, smoking history, systolic and diastolic blood pressure, history of hypertension, type 2 diabetes, Hachinski score).Cross‐sectional and future cognitive outcomes were all predicted in a single machine learning model using all combinations of predictor families at baseline, time interval between outcomes and baseline as long as sex and education. Three types of regression models were tested (Ridge, Partial Least Squares and Support Vector).ResultIndividually, neuronal and metabolism integrity were the best predictors of cognitive function (Figure 1; R2: .15‐.35 and MAE in Z score: .08‐.23). The combination of two or more mesoscale brain health markers improved predictions, with the best combination being neuronal integrity with metabolism (Figures 2‐3; mean R2: .28; mean MAE: .12). However, increasing the number of markers led to similar results.ConclusionWhile the prediction of cognition improved with a combination of brain health mesoscale markers, a plateau seems to be reached after combining two families.

Real-World and Clinical Trial Validation of a Deep Learning Radiomic Biomarker for PD-(L)1 Immune Checkpoint Inhibitor Response in Advanced Non-Small Cell Lung Cancer.

This study developed and validated a novel deep learning radiomic biomarker to estimate response to immune checkpoint inhibitor (ICI) therapy in advanced non-small cell lung cancer (NSCLC) using real-world data (RWD) and clinical trial data. Retrospective RWD of 1,829 patients with advanced NSCLC treated with PD-(L)1 ICIs were collected from 10 academic and community institutions in the United States and Europe. The RWD included data sets for discovery (Data Set A-Discovery, n = 1,173) and independent test (Data Set B, n = 458). A radiomic pipeline, containing a deep learning feature extractor and a survival model, generated the computed tomography (CT) response score (CTRS) applied to the pretreatment routine CT/positron emission tomography (PET)-CT scan. An enhanced CTRS (eCTRS) also incorporated age, sex, treatment line, and lesion annotations. Performance was evaluated against progression-free survival (PFS) and overall survival (OS). Biomarker generalizability was further evaluated using a secondary analysis of a prospective clinical trial (ClinicalTrials.gov identifier: NCT02573259) evaluating the PD-1 inhibitor sasanlimab in second or later line of treatment (Data Set C, n = 54). In RWD Test Data Set B, the CTRS identified patients with a high probability of response to ICI with a PFS hazard ratio (HR) of 0.46 (95% CI, 0.26 to 0.82) and an OS HR of 0.50 (95% CI, 0.28 to 0.92) in the first-line ICI monotherapy cohort, after adjustment for baseline covariates including the PD-L1 tumor proportion score. In Clinical Trial Data Set C, the CTRS demonstrated an adjusted PFS HR of 1.03 (95% CI, 0.43 to 2.47) and an OS HR of 0.33 (95% CI, 0.14 to 0.91). The CTRS and eCTRS outperformed traditional imaging biomarkers of lesion size in PFS and OS for RWD Test Data Set B and in OS for the Clinical Trial Data Set. The study developed and validated a deep learning radiomic biomarker using pretreatment routine CT/PET-CT scans to identify ICI benefit in advanced NSCLC.

Cross sectional dopamine transporter imaging and myocardial sympathetic scintigraphy study in patients with dementia with Lewy bodies

AbstractBackgroundDopamine transporter (123I‐FP‐CIT) single‐photon emission tomography (SPECT) and 123I‐meta‐iodobenzylguanidine (123I‐MIBG) image play roles as indicative biomarkers in diagnosing patients with dementia with Lewy bodies (DLB). Brain‐ and body‐first subtypes of DLB were hypothesized implying that subset of DLB may have normal 123I‐FP‐CIT or 123I‐MIBG results, respectively. The purpose of this study was to explore the diagnostic sensitivity of two combination imaging modalities (123I‐FP‐CIT SPECT and 123I‐MIBG image) in patients with DLB and examine the clinical difference between brain‐ and body‐first subtype.MethodPossible DLB patients, defined by the fourth consensus DLB criteria, who underwent both 123I‐FP‐CIT SPECT and 123I‐MIBG image was retrospectively collected. Semi‐automated software and their results were utilized to define abnormality for both scans. Demographic data, cognition, motor, and core features were compared between the brain‐first and body first DLB subgroups.ResultOf the 114 patients with DLB, 66 underwent both scans. Mean (SD) age was 74.1 (7.1) years, male was predominant (62.1%), min‐mental state examination total score was 21.7 (4.8) and unified Parkinson’s disease rating scale motort subscore was 14.7 (4.8). Thirty‐six (54.5%) patients showed both abnormal scans and four patients (6.1%) were both normal scans. Seventeen patients (25.8%) showed abnormal 123I‐FP‐CIT result with normal 123I‐MIBG result (brain‐first DLB), nine patients (13.6%) showed normal 123I‐FP‐CIT result with abnormal 123I‐MIBG result (body‐first DLB). No clinical differences were observed between brain‐first and body‐first DLB subtypes.ConclusionApproximately 40% of DLB patients displayed normal result in either image. Normal results of a single imaging test may not refute the possibility of DLB.No clinical difference was observed between brain‐ and body‐first DLB subtypes.

Studies of gas ionization by high-power, sub-nanosecond microwave pulses

This study investigates the ionization pressure threshold of a gas (air, helium, argon, and SF6 across a wide pressure range) filled dielectric tube when a ∼300 MW, ∼0.7 ns, 9.6 GHz high-power microwave (HPM) pulse propagates through it. The thresholds are determined as the pressure for which the energy of the transmitted HPM pulse decreases to ∼30%, which is close to the same HPM pulse's transmission coefficient when a metal rod fills the tube. These thresholds are found to be 0.4 × 105 Pa,105 Pa, 1.8 × 105 Pa, and 0.2 × 105 Pa, for air, argon, helium, and SF6, respectively. The measured intensity of the plasma light emission starts to decrease at a pressure which coincides with the pressure threshold determined by HPM pulse propagation. Additionally, at gas pressures &amp;lt;5 × 104 Pa, it is shown that time- and space-resolved images of the light emission display a diffused plasma which at higher pressures &amp;gt;105 Pa transforms into streamer like plasma. Simplified numerical simulations of a microwave discharge in air at 1 × 105 Pa and 4 × 105 Pa are consistent with the experimental plasma light observations.

Effect of Lateral Pressure on the Stability of Inclined Layered Rock Tunnel: A 3D-printed Model Investigation by Cement-based Materials

The inclined layered rock tunnel engineering in the alpine canyon area subject to tectonic stress will be influenced by high lateral stress. Currently, there are scarce reports on the impact of the lateral pressure coefficient on the stability of inclined layered rock tunnels. Hence, the mechanical response of the inclined layered tunnel model was investigated based on the 3D-printed model test, supplemented by acoustic emission (AE) and digital image correlation (DIC) monitoring methods under three cases of lateral pressure coefficients of 1.2, 1.5 and 1.8. The results reveal that for the tunnel model with a 60° bedding inclination, the bearing capacity is negatively correlated with the lateral pressure coefficient. The normal deformation of the bedding of the tunnel model is prominent, exhibiting significant asymmetric deformation characteristics. When the lateral pressure coefficient k increases from 1.2 to 1.5, the failure of the tunnel model changes from shear-slip failure along the layer to bedding cracking and buckling failure of the sidewall. The test results have enlightenment significance for the stability evaluation of inclined layered surrounding rock tunnels in the alpine canyon area.