Quantitative Analysis of Arterial Spin Labeling FMRI Data Using a General Linear Model

Arterial spin labeling techniques can yield quantitative measures of perfusion by fitting a kinetic model to difference images (tagged-control). Because of the noisy nature of the difference images investigators typically average a large number of tagged versus control difference measurements over long periods of time. This averaging requires that the perfusion signal be at a steady state and not at the transitions between active and baseline states in order to quantitatively estimate activation induced perfusion. This can be an impediment for functional magnetic resonance imaging task experiments. In this work, we introduce a general linear model (GLM) that specifies Blood Oxygenation Level Dependent (BOLD) effects and arterial spin labeling modulation effects and translate them into meaningful, quantitative measures of perfusion by using standard tracer kinetic models. We show that there is a strong association between the perfusion values using our GLM method and the traditional subtraction method, but that our GLM method is more robust to noise

Diffuse interstellar bands in fullerene planetary nebulae: the fullerenes - diffuse interstellar bands connection

We present high-resolution (R~15000) VLT/UVES optical spectra of two planetary nebulae (PNe; Tc 1 and M 1-20) where C60 (and C70) fullerenes have already been found. These spectra are of high-quality (S/N > 300) for PN Tc 1, which permits us to search for the expected electronic transitions of neutral C60 and diffuse interstellar bands (DIBs). Surprisingly, we report the non-detection of the most intense optical bands of C60 in Tc 1, although this could be explained by the low C60 column density estimated from the C60 infrared bands if the C60 emission peaks far away from the central star. The strongest and most common DIBs in both fullerene PNe are normal for their reddening. Interestingly, the very broad 4428 A DIB and the weaker 6309 A DIB are found to be unusually intense in Tc 1. We also report the detection of a new broad (FWHM~5 A) unidentified band at ~6525 A. We propose that the 4428 A DIB (probably also the 6309 A DIB and the new 6525 A band) may be related to the presence of larger fullerenes (e.g., C80, C240, C320, and C540) and buckyonions (multishell fullerenes such as C60@C240 and C60@C240@C540) in the circumstellar envelope of Tc 1.Comment: Accepted for publication in Astronomy & Astrophysics Letters (6 pages, 4 figures, and 1 Table

A search for diffuse bands in fullerene planetary nebulae: evidence of diffuse circumstellar bands

Large fullerenes and fullerene-based molecules have been proposed as carriers of diffuse interstellar bands (DIBs). The recent detection of the most common fullerenes (C60 and C70) around some planetary nebulae (PNe) now enable us to study the DIBs towards fullerene-rich space environments. We search DIBs in the optical spectra towards three fullerene-containing PNe (Tc 1, M 1-20, and IC 418). Special attention is given to DIBs which are found to be unusually intense towards these fullerene sources. In particular, an unusually strong 4428A absorption feature is a common charateristic of fullerene PNe. Similar to Tc 1, the strongest optical bands of neutral C60 are not detected towards IC 418. Our high-quality (S/N > 300) spectra for PN Tc 1, together with its large radial velocity, permit us to search for the presence of diffuse bands of circumstellar origin, which we refer to as diffuse circumstellar bands (DCBs). We report the first tentative detection of two DCBs at 4428 and 5780 A in the fullerene-rich circumstellar environment around the PN Tc 1. Laboratory and theoretical studies of fullerenes in their multifarious manifestations (carbon onions, fullerene clusters, or even complex species formed by fullerenes and other molecules like PAHs or metals) may help solve the mystery of some of the diffuse band carriers.Comment: Accepted for publication in Astronomy & Astrophysics (16 pages, 10 figures, and 7 Tables); final version (changes regarding PN M 1-20 and language corrected

Optimizing MRFâ ASL scan design for precise quantification of brain hemodynamics using neural network regression

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154517/1/mrm28051.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154517/2/mrm28051_am.pd

Improved sensitivity and temporal resolution in perfusion FMRI using velocity selective inversion ASL

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146889/1/mrm27461_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146889/2/mrm27461.pd

Arterial cerebral blood volume–weighted functional MRI using pseudocontinuous arterial spin tagging (AVAST)

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110725/1/mrm25220.pd

Graphical tools to the rescue. high resolution aerial photography for the location of missing persons

Since the COVID-19 pandemic changed the rules of the game in many work envi-ronments, adaptation has been a key factor. Restrictions such as social distance or confinement made searches for missing persons more difficult. Although mo-bility limitations led to a decrease in the number of disappearances, they did not stop completely and search teams had to adapt to the new scenario that prevent-ed, for example, the participation of volunteers. For these reasons, it was decided to implement a tool that has been in development for years, based on the Collab-oration Agreement signed in 2015 between the Servicio de Prevención y Extinción de Incendios de la Diputación Provincial de Zaragoza (SPEI-DPZ) and the Uni-versity of Zaragoza. The tool is called Virtual Cloud Search and Rescue (VC-SAR) and is still under development by the authors of this communication. The following is a basic description of the tool and how it was applied in a real case, in which a missing person was being searched. The device used made it possible to obtain about 5000 images of 44.7 megapixels, covering an area of over 2000 hectares. Thanks to the searches carried out, more than 100 pieces of evidence were found over the course of four days, which could be collected for on-site in-vestigation by the Navarra Fire Service. All this was possible thanks to the collab-oration of 5 different fire departments, belonging to three provinces, making pos-sible the participation of a total of 52 searchers from different locations. Keywords: Graphical tools; Aerial images; Search and rescue; Drones

Support vector machine classification of arterial volumeâ weighted arterial spin tagging images

IntroductionIn recent years, machineâ learning techniques have gained growing popularity in medical image analysis. Temporal brainâ state classification is one of the major applications of machineâ learning techniques in functional magnetic resonance imaging (fMRI) brain data. This article explores the use of support vector machine (SVM) classification technique with motorâ visual activation paradigm to perform brainâ state classification into activation and rest with an emphasis on different acquisition techniques.MethodsImages were acquired using a recently developed variant of traditional pseudocontinuous arterial spin labeling technique called arterial volumeâ weighted arterial spin tagging (AVAST). The classification scheme is also performed on images acquired using blood oxygenationâ level dependent (BOLD) and traditional perfusionâ weighted arterial spin labeling (ASL) techniques for comparison.ResultsThe AVAST technique outperforms traditional pseudocontinuous ASL, achieving classification accuracy comparable to that of BOLD contrast images.ConclusionThis study demonstrates that AVAST has superior signalâ toâ noise ratio and improved temporal resolution as compared with traditional perfusionâ weighted ASL and reduced sensitivity to scanner drift as compared with BOLD. Owing to these characteristics, AVAST lends itself as an ideal choice for dynamic fMRI and realâ time neurofeedback experiments with sustained activation periods.In this article, we test the performance of our recently introduced method for dynamic arterial blood volume imaging (AVAST) in the context of functional MRI data classification. AVAST is compared with blood oxygenationâ level dependent (BOLD) and arterial spin labeling (ASL) perfusion data collected during a simple motor task using a support vector machine algorithm to classify the brain state. Findings suggest that the AVAST technique has similar performance as BOLD imaging, while preserving the statistical benefits of ASL techniques.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135476/1/brb3549_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135476/2/brb3549.pd