180 research outputs found
Exploratory radiomic features from integrated 18F-fluorodeoxyglucose positron emission tomography/magnetic resonance imaging are associated with contemporaneous metastases in oesophageal/gastroesophageal cancer
No full textPurpose: To determine if 18F-fluorodeoxyglucose positron emission tomography/magnetic resonance imaging (18F-FDG PET/MRI) features are associated with contemporaneous metastases in patients with oesophageal/gastroesophageal cancer.
Methods: Following IRB approval and informed consent, patients underwent a staging PET/MRI following 18F-FDG injection (326±28 MBq) and 156 ± 23 minutes uptake time. First- order histogram and second-order grey level co-occurrence matrix features were computed for PET standardized uptake value (SUV) and MRI T1-W, T2-W, diffusion weighted (DWI) and apparent diffusion coefficient (ADC) images for the whole tumour volume. K-means clustering assessed the correlation of feature-pairs with metastases. Multivariate analysis of variance (MANOVA) was performed to assess the statistical separability of the groups identified by feature-pairs. Sensitivity (SN), specificity (SP), positive predictive value (PPV), negative predictive value (NPV), and accuracy (ACC) were calculated for these features and compared with SUVmax, ADCmean and maximum diameter alone for predicting contemporaneous metastases.
Results: 20 patients (18 males, 2 female; median 67 years, range: 52-86) comprised the final study cohort; 10 patients had metastases. Lower second-order SUV entropy combined with higher second-order ADC entropy were the best feature-pair for discriminating metastatic patients, MANOVA p-value <0.001 (SN=80%, SP=80%, PPV=80%, NPV=80%, ACC=80%). SUVmax (SN=30%, SP=80%, PPV=60%, NPV=53%, ACC=55%), ADCmean (SN = 20%, SP = 70%, PPV = 40%, NPV = 47%, ACC = 45%) and tumour maximum diameter (SN=10%, SP=90%, PPV=50%, NPV=50%, ACC=50%) had poorer sensitivity and accuracy.
Conclusion: High ADC entropy combined with low SUV entropy is associated with a higher prevalence of metastases and a promising initial signature for future study
sj-docx-1-jop-10.1177_02698811221099643 – Supplemental material for The association between N-methyl-d-aspartate receptor availability and glutamate levels: A multi-modal PET-MR brain imaging study in first-episode psychosis and healthy controls
No full textSupplemental material, sj-docx-1-jop-10.1177_02698811221099643 for The association between N-methyl-d-aspartate receptor availability and glutamate levels: A multi-modal PET-MR brain imaging study in first-episode psychosis and healthy controls by Katherine Beck, Atheeshaan Arumuham, Stefan Brugger, Robert A McCutcheon, Mattia Veronese, Barbara Santangelo, Colm J McGinnity, Joel Dunn, Stephen Kaar, Nisha Singh, Toby Pillinger, Faith Borgan, Teresa Sementa, Radhouene Neji, Sameer Jauhar, Franklin Aigbirhio, Istvan Boros, Federico Turkheimer, Alexander Hammers, David Lythgoe, James Stone and Oliver D Howes in Journal of Psychopharmacology</p
Initial experience in staging primary oesophageal/gastro-oesophageal cancer with 18F-FDG PET/MRI.
No full textBACKGROUND
18F-fluorodeoxyglucose positron emission tomography/magnetic resonance imaging (18F-FDG PET/MRI) may improve cancer staging by combining sensitive cancer detection with high-contrast resolution and detail. We compared the diagnostic performance of 18F-FDG PET/MRI to 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) for staging oesophageal/gastro-oesophageal cancer. Following ethical approval and informed consent, participants with newly diagnosed primary oesophageal/gastro-oesophageal cancer were enrolled. Exclusions included prior/concurrent malignancy. Following 324 ± 28 MBq 18F-FDG administration and 60-min uptake, PET/CT was performed, immediately followed by integrated PET/MRI from skull base to mid-thigh. PET/CT was interpreted by two dual-accredited nuclear medicine physicians and PET/MRI by a dual-accredited nuclear medicine physician/radiologist and cancer radiologist in consensus. Per-participant staging was compared with the tumour board consensus staging using the McNemar test, with statistical significance at 5%.
RESULTS
Out of 26 participants, 22 (20 males; mean ± SD age 68.8 ± 8.7 years) completed 18F-FDG PET/CT and PET/MRI. Compared to the tumour board, the primary tumour was staged concordantly in 55% (12/22) with PET/MRI and 36% (8/22) with PET/CT; the nodal stage was concordant in 45% (10/22) with PET/MRI and 50% (11/22) with PET/CT. There was no statistical difference in PET/CT and PET/MRI staging performance (p > 0.05, for T and N staging). The staging of distant metastases was concordant with the tumour board in 95% (21/22) with both PET/MRI and PET/CT. Of participants with distant metastatic disease, PET/MRI detected additional metastases in 30% (3/10).
CONCLUSION
In this preliminary study, compared to 18F-FDG PET/CT, 18F-FDG PET/MRI showed non-significant higher concordance with T-staging, but no difference with N or M-staging. Additional metastases detected by 18F-FDG PET/MRI may be of additive clinical value
Radar Based Human Vital Sign Detection In Cars: A System Analysis
No full textThis thesis analyses different radar systems for sensing chest movement to detect human presence inside a car. The detection in this thesis is limited to sensing breathing rate, although heartbeat detection is considered a possibility. A comparison is made between CW-, FMCW-, pulsed- and UWB pulsed radar. UWB pulsed radar was chosen to be a suitable technology for this application. As a benchmark, the Xethru X4 SoC by Novelda is used. The parameters and the working of Xethru X4 are investigated. A suitable antenna for Xethru is designed and simulated. Different detection techniques are discussed. The feasibility of the Xethru X4 is tested by means of calculations in different settings. Based on these tests, the Xethru X4 is evaluated and concluded to be suitable for detecting human presence inside a car by means of vital sign detection.EE3L11 Bachelor graduation project Electrical EngineeringElectrical Engineerin
mapping and water/fat imaging
No full textPurpose
To develop a free-breathing isotropic-resolution whole-heart joint T1 and T2 mapping sequence with Dixon-encoding that provides coregistered 3D T1 and T2 maps and complementary 3D anatomical water and fat images in a single ~9 min scan.
Methods
Four interleaved dual-echo Dixon gradient echo volumes are acquired with a variable density Cartesian trajectory and different preparation pulses: 1) inversion recovery-preparation, 2) and 3) no preparations, and 4) T2 preparation. Image navigators are acquired to correct each echo for 2D translational respiratory motion; the 8 echoes are jointly reconstructed with a low-rank patch-based reconstruction. A water/fat separation algorithm is used to obtain water and fat images for each acquired volume. T1 and T2 maps are generated by matching the signal evolution of the water images to a simulated dictionary. Complementary bright-blood and fat volumes for anatomical visualization are obtained from the T2-prepared dataset. The proposed sequence was tested in phantom experiments and 10 healthy subjects and compared to standard 2D MOLLI T1 mapping, 2D balance steady-state free precession T2 mapping, and 3D T2-prepared Dixon coronary MR angiography.
Results
High linear correlation was found between T1 and T2 quantification with the proposed approach and phantom spin echo measurements (y = 1.1 × −11.68, R2 = 0.98; and y = 0.85 × +5.7, R2 = 0.99). Mean myocardial values of T1/T2 = 1116 ± 30.5 ms/45.1 ± 2.38 ms were measured in vivo. Biases of T1/T2 = 101.8 ms/−0.77 ms were obtained compared to standard 2D techniques.
Conclusion
The proposed joint T1/T2 sequence permitted the acquisition of motion-compensated isotropic-resolution 3D T1 and T2 maps and complementary coronary MR angiography and fat volumes, showing promising results in terms of T1 and T2 quantification and visualization of cardiac anatomy and pericardial fat
Fully integrated 3D high-resolution multicontrast abdominal PET-MR with high scan efficiency
No full textPurpose: To provide 3D multicontrast anatomical MR with high isotropic resolution and metabolic positron emission tomography (PET) images using a respiratory motion-compensated simultaneous PET-MR examination with high scan efficiency. Theory and Methods: Standard abdominal PET-MR examinations combine MR data obtained during multiple breath-holds with free-breathing PET acquisitions, limiting the achievable image resolution and potentially causing misalignment errors between breath-hold and free-breathing data. Here, a 3D free-breathing PET-MR acquisition is presented, yielding T1 and T2-weighted MR images with an isotropic resolution of 1.5mm3. In addition, nonrigid respiratory motion information and respiratory-resolved attenuation-correction maps are obtained without an increase in scan time. Motion information is used in motion-compensated image reconstructions to improve MR and PET image quality while shortening scan times. Results: The proposed approach was evaluated in 11 oncology patients and provided respiratory motion information with an accuracy of 1.3±0.1mm. Sharpness of anatomical features was increased by 19±13% compared with the uncorrected MR images in a 54±26% shorter scan time than a gated MR acquisition. The MR-based motion information improved uptake values (75±94%) and resolution (16±27%) of simultaneously acquired PET images. Conclusions: The proposed method provides motion-compensated 3D high-quality MR and PET images in a comprehensive and highly efficient examination.</p
Distortion‐free 3D diffusion imaging of the prostate using a multishot diffusion‐prepared phase‐cycled acquisition and dictionary matching
No full textPurpose: To achieve three-dimensional (3D) distortion-free apparent diffusion coefficient (ADC) maps for prostate imaging using a multishot diffusion prepared-gradient echo (msDP-GRE) sequence and ADC dictionary matching. Methods: The msDP-GRE sequence is combined with a 3D Cartesian, centric k-space trajectory with center oversampling. Oversampled k-space center averaging and phase cycling are used to address motion- and eddy current–induced magnitude corruption. Extended-phase-graph (EPG) simulations and ADC dictionary matching are used to compensate for T1 effects. To shorten the acquisition time, each volume is undersampled by a factor of two and reconstructed using iterative sensitivity encoding. The proposed approach is characterized using simulations and validated in a kiwifruit phantom, comparing the msDP-GRE ADC maps obtained using both standard monoexponential fitting and dictionary matching with the clinical standard single-shot diffusion weighted-echo planar imaging (ssDW-EPI) ADC. Initial in vivo feasibility is tested in three healthy subjects, and geometric distortion is compared with anatomical T2-weighted-turbo spin echo. Results: In the kiwifruit phantom experiment, the signal magnitude could be recovered using k-space center averaging and phase cycling. No statistically significant difference was observed in the ADC values estimated using msDP-GRE with dictionary matching and clinical standard DW-EPI (P <.05). The in vivo prostate msDP-GRE scans were free of geometric distortion caused by off-resonance susceptibility, and the ADC values in the prostate were in agreement with values found in the published literature. Conclusion: Nondistorted 3D ADC maps of the prostate can be achieved using a msDP sequence and dictionary matching.</p
Fast Automated PET Image Quality Assessment by Deep Learning
No full textThe use of simultaneous positron emission tomography - magnetic resonance imaging (PET-MR) earlier in the diagnostic pathway for memory clinic patients is inhibited by associated radiation dose and tracer costs. Low-dose PET imaging and reconstruction may overcome these limitations, but the higher noise levels compromise image quality. We have developed a convolutional neural network (CNN) capable of automating low-dose PET image quality assessments, typically executed by experienced clinicians. Automating image quality assessments may aid large-scale reconstruction hyperparameter investigations, working faster towards clinically feasible reconstructions at ultra-reduced injected doses. Preliminary work used 1800 reconstructed phantoms to predict, initially, the coefficient of variation (CV) as a noise level measure. For non-normalised and normalised test images, the mean errors in CV prediction were 3.4 ± 2.6% and 16.1 ± 11.9%, respectively. In a real patient study, data from one patient was resampled at different dose levels and reconstructed using maximum-likelihood expectation maximisation. A CNN was trained on 3200 randomly extracted patches, with simultaneous predictions of the dose and three clinician-scored metrics: global quality rating, pattern recognition, and diagnostic confidence. The median prediction for 1000 test-time patches for each dose level was taken, obtaining mean-absolute-errors of 10.20 ± 22.30 MBq, 0.27 ± 0.52, 0.11 ± 0.25 and 0.04 ± 0.04, for each metric, respectively. This study shows that it is possible to automatically predict multiple metrics, both clinician-scored and conventional quantitative image quality measures, simultaneously. Future work will include obtaining more clinically scored reconstructions, to improve training and performance of the model.</p
The association between N-methyl-d-aspartate receptor availability and glutamate levels:A multi-modal PET-MR brain imaging study in first-episode psychosis and healthy controls
No full textBackground: Evidence from post-mortem studies and in vivo imaging studies suggests there may be reduced N-methyl-d-aspartate receptor (NMDAR) levels in the hippocampus in patients with schizophrenia. Other studies have reported increased glutamate in striatum in schizophrenia patients. It has been hypothesised that NMDAR hypofunction leads to the disinhibition of glutamatergic signalling; however, this has not been tested in vivo. Methods: In this study, we investigated the relationship between hippocampal NMDAR and striatal glutamate using simultaneous positron emission tomography-magnetic resonance (PET-MR) imaging. We recruited 40 volunteers to this cross-sectional study; 21 patients with schizophrenia, all in their first episode of illness, and 19 healthy controls. We measured hippocampal NMDAR availability using the PET ligand [ 18F]GE179. This was indexed relative to whole brain as the distribution volume ratio (DVR). Striatal glutamatergic indices (glutamate and Glx) were acquired simultaneously, using combined PET-MR proton magnetic resonance spectroscopy ( 1H-MRS). Results: A total of 33 individuals (15 healthy controls, 18 patients) were included in the analyses (mean (SD) age of controls, 27.31 (4.68) years; mean (SD) age of patients, 24.75 (4.33), 27 male and 6 female). We found an inverse relationship between hippocampal DVR and striatal glutamate levels in people with first-episode psychosis (rho = −0.74, p < 0.001) but not in healthy controls (rho = −0.22, p = 0.44). Conclusion: This study show that lower relative NMDAR availability in the hippocampus may drive increased striatal glutamate levels in patients with schizophrenia. Further work is required to determine whether these findings may yield new targets for drug development in schizophrenia. </p
Factors promoting conduction slowing as substrates for block and reentry in infarcted hearts:Slow conduction and scar-related reentry
No full textThe development of effective and safe therapies for scar-related ventricular tachycardias requires a detailed understanding of the mechanisms underlying the conduction block that initiates electrical re-entries associated with these arrhythmias. Conduction block has been often associated with electrophysiological changes that prolong action potential duration (APD) within the border zone (BZ) of chronically infarcted hearts. However, experimental evidence suggests that remodeling processes promoting conduction slowing as opposed to APD prolongation mark the chronic phase. In this context, the substrate for the initial block at the mouth of an isthmus/diastolic channel leading to ventricular tachycardia is unclear. The goal of this study was to determine whether electrophysiological parameters associated with conduction slowing can cause block and re-entry in the BZ. In silico experiments were conducted on two-dimensional idealized infarct tissue as well as on a cohort of postinfarction porcine left ventricular models constructed from ex vivo magnetic resonance imaging scans. Functional conduction slowing in the BZ was modeled by reducing sodium current density, whereas structural conduction slowing was represented by decreasing tissue conductivity and including fibrosis. The arrhythmogenic potential of APD prolongation was also tested as a basis for comparison. Within all models, the combination of reduced sodium current with structural remodeling more often degenerated into re-entry and, if so, was more likely to be sustained for more cycles. Although re-entries were also detected in experiments with prolonged APD, they were often not sustained because of the subsequent block caused by long-lasting repolarization. Functional and structural conditions associated with slow conduction rather than APD prolongation form a potent substrate for arrhythmogenesis at the isthmus/BZ of chronically infarcted hearts. Reduced excitability led to block while slow conduction shortened the wavelength of propagation, facilitating the sustenance of re-entries. These findings provide important insights for models of patient-specific risk stratification and therapy planning
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