517 research outputs found
Variable Resolution Sampling and Deep Learning-Based Image Recovery for Faster Multi-Spectral Imaging Near Metal Implants
Purpose: In multi-spectral imaging (MSI), several fast spin echo volumes with
discrete Larmor frequency offsets are acquired in an interleaved fashion with
multiple concatenations. Here, a variable resolution (VR) method to nearly
halve scan time is proposed by only acquiring low resolution autocalibrating
signal in half of the concatenations.
Methods: Knee MSI datasets were retrospectively undersampled with the
proposed variable resolution sampling scheme. A U-Net model was trained to
predict the full-resolution images from the VR input. Image quality was
assessed in 10 test subjects.
Results: Spectral bin-combined images produced with the proposed variable
resolution sampling with deep learning reconstruction appear to be of high
quality and exhibited a median structural image similarity of 0.984 across test
subjects and slices.
Conclusion: The proposed variable resolution sampling method shows promise
for drastically reducing the time it takes to collect multi-spectral imaging
data near metallic implants. Further studies will rigorously examine its
clinical utility across multiple implant scenarios
On Functional Activations in Deep Neural Networks
Background: Deep neural networks have proven to be powerful computational
tools for modeling, prediction, and generation. However, the workings of these
models have generally been opaque. Recent work has shown that the performance
of some models are modulated by overlapping functional networks of connections
within the models. Here the techniques of functional neuroimaging are applied
to an exemplary large language model to probe its functional structure.
Methods: A series of block-designed task-based prompt sequences were generated
to probe the Facebook Galactica-125M model. Tasks included prompts relating to
political science, medical imaging, paleontology, archeology, pathology, and
random strings presented in an off/on/off pattern with prompts about other
random topics. For the generation of each output token, all layer output values
were saved to create an effective time series. General linear models were fit
to the data to identify layer output values which were active with the tasks.
Results: Distinct, overlapping networks were identified with each task. Most
overlap was observed between medical imaging and pathology networks. These
networks were repeatable across repeated performance of related tasks, and
correspondence of identified functional networks and activation in tasks not
used to define the functional networks was shown to accurately identify the
presented task. Conclusion: The techniques of functional neuroimaging can be
applied to deep neural networks as a means to probe their workings. Identified
functional networks hold the potential for use in model alignment, modulation
of model output, and identifying weights to target in fine-tuning
The Association Between Persistent White-Matter Abnormalities and Repeat Injury After Sport-Related Concussion
Objective: A recent systematic review determined that the physiological effects of concussion may persist beyond clinical recovery. Preclinical models suggest that ongoing physiological effects are accompanied by increased cerebral vulnerability that is associated with risk for subsequent, more severe injury. This study examined the association between signal alterations on diffusion tensor imaging following clinical recovery of sport-related concussion in athletes with and without a subsequent second concussion. Methods: Average mean diffusivity (MD) was calculated in a region of interest (ROI) in which concussed athletes (n = 82) showed significantly elevated MD acutely after injury (<48 h), at an asymptomatic time point, 7 days post-return to play (RTP), and 6 months relative to controls (n = 69). The relationship between MD in the identified ROI and likelihood of sustaining a subsequent concussion over a 1-year period was examined with a binary logistic regression (re-injured, yes/no). Results: Eleven of 82 concussed athletes (13.4%) sustained a second concussion within 12 months of initial injury. Mean MD at 7 days post-RTP was significantly higher in those athletes who went on to sustain a repeat concussion within 1 year of initial injury than those who did not (p = 0.048; d = 0.75). In this underpowered sample, the relationship between MD at 7 days post-RTP and likelihood of sustaining a secondary injury approached significance [χ2 (1) = 4.17, p = 0.057; B = 0.03, SE = 0.017; OR = 1.03, CI = 0.99, 1.07]. Conclusions: These preliminary findings raise the hypothesis that persistent signal abnormalities in diffusion imaging metrics at RTP following concussion may be predictive of a repeat concussion. This may reflect a window of cerebral vulnerability or increased susceptibility following concussion, though understanding the clinical significance of these findings requires further study
Microcanonical treatment of black hole decay at the Large Hadron Collider
This study of corrections to the canonical picture of black hole decay in
large extra dimensions examines the effects of back-reaction corrected and
microcanonical emission at the LHC. We provide statistical interpretations of
the different multiparticle number densities in terms of black hole decay to
standard model particles. Provided new heavy particles of mass near the
fundamental Planck scale are not discovered, differences between these
corrections and thermal decay will be insignificant at the LHC.Comment: small additions and clarifications, format for J. Phys.
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