Suicide has a high comorbidity with impulsivity and depression, and finding imaging biomarkers indicative of patients at high risk for suicidal behavior is invaluable to the clinician. Using ...single-photon emission computed tomography (SPECT) imaging, we have previously reported regional cerebral blood flow (rCBF) decreases in the medial prefrontal cortex, ventral tegmental area and subgenual cingulate cortex (Brodmann area 25 (BA 25)), a region found to be hypoperfused with treatment-resistant depression. From 2007 to 2010, we have extended our analysis to include nine additional completed suicides. In all, 27 healthy, age- and gender-matched subjects from a previously acquired healthy brain study served as controls to our 21 completed suicides. All 21 suicides had been previously diagnosed with depression according to Diagnostic and Statistical Manual of Mental Disorder-IV criterion. Voxel-by-voxel analyses were performed using statistical parametric mapping to compare the differences in technetium-99m hexamethylpropylene amine oxime brain uptake between the groups. Factor analysis of the data identified the top 10 regions of hypoperfusion in the suicidal group, including the bilateral superior frontal lobes, the right precuneus, the rolandic operculum, postcentral gyrus, left caudate and insular cortex. We also demonstrate more focal decreases in rCBF in the subgenual cingulate cortex (BA 25) in 18 subjects, supporting our previous hypothesis that hypoperfusion of BA 25 may be a risk factor for suicide in depressed patients. This work suggests that SPECT might be useful in predicting risk for suicide completion in subjects with depression or treatment-resistant depression. Further investigation of this work is necessary to better understand the predictive value of this finding.
Obesity is a risk factor for neurodegenerative disease and has been shown to adversely affect cognitive function. Professional athletes who participate in sports, which expose them to repetitive ...concussions, may be at heightened risk for cognitive impairment. Here, we investigated the effects of body mass as measured by waist-to-height ratio (WHtR) on regional cerebral blood flow using single-photon emission computed tomography imaging in 38 healthy weight (WHtR mean 49.34 ± 2.8; age 58 ± 9.6) and 38 overweight (WHtR mean 58.7 ± 4.7; age 58 ± 13.3) retired National Football League football players. After matching for age and position, we used a two sample t-test to determine the differences in blood flow in healthy versus overweight subjects. Statistical parametric mapping revealed a higher WHtR ratio is associated with decreased blood flow in Brodmann areas 8, 9 and 10, brain regions involved in attention, reasoning and executive function (P<0.05, family-wise error) along with deficits in the temporal pole. Moreover, overweight athletes had significant decrease in attention (P = 0.01326), general cognitive proficiency (P = 0.012; Microcog: Assessment of Cognitive Functioning) and memory (P=0.005; Mild Cognitive Impairment Screen). The association between elevated WHtR percentage and decreased blood flow in the prefrontal cortex and temporal pole may be correlated with the decreased performance on tests of attention and memory. These findings suggest that a weight management program may be critical to the health of athletes who have been exposed to mild brain trauma during their careers.
We report on the results of a radiation campaign with neutrons and protons of Low Gain Avalanche Detectors (LGAD) produced by Hamamatsu (HPK) as prototypes for the High-Granularity Timing Detector ...(HGTD) in ATLAS. Sensors with an active thickness of 50μm were irradiated in steps of roughly 2× up to a fluence of 3×1015neqcm−2. As a function of the fluence, the collected charge and time resolution of the irradiated sensors will be reported for operation at −30 °C.
This paper studies the radiation hardness of low gain avalanche detector (LGAD) developed by the Novel Device Laboratory (NDL) in Beijing and the Institute of High Energy Physics (IHEP) of Chinese ...Academy of Sciences, in the context of an upgrade project of the ATLAS detector for the high luminosity phase of LHC. NDL LGAD sensors with different layouts, epitaxial resistivity and doping profile were irradiated up to 1.02 × 1015 neq/cm2 by 70 MeV protons at Cyclotron and Radioisotope Center (CYRIC). The timing resolution of NDL LGAD sensors reached 50 ps and the collected charge reached 3 - 4 fC after irradiation.
Beam test results of NDL Low Gain Avalanche Detectors (LGAD) Xiao, S.; Alderweireldt, S.; Ali, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2021, Letnik:
989
Journal Article
Recenzirano
A High-Granularity Timing Detector (HGTD) is proposed based on the Low-Gain Avalanche Detector (LGAD) for the ATLAS experiment to satisfy the time resolution requirement for the up-coming High ...Luminosity at LHC (HL-LHC). We report on beam test results for two proto-types LGADs (BV60 and BV170) developed for the HGTD. Such modules were manufactured by the Institute of High Energy Physics (IHEP) of Chinese Academy of Sciences (CAS) collaborated with Novel Device Laboratory (NDL) of the Beijing Normal University. The beam tests were performed with 5 GeV electron beam at DESY. The timing performance of the LGADs was compared to a trigger counter consisting of a quartz bar coupled to a SiPM readout while extracting reference SiPM by fitting with a Gaussian function. The time resolution was obtained as 41 ps and 63 ps for the BV60 and the BV170, respectively.
Forty adolescents and adults who exhibited aggressive behavior within the six months prior to evaluation by physically attacking another person or destroying property were evaluated with brain SPECT ...imaging. A control group of 40 psychiatric patients who had never been reported to exhibit aggressive behavior were also studied. The brain SPECT studies were read blind to aggressiveness by nuclear physician on two separate occasions. The interreading reliability was very high. The brain SPECT patterns of the group with aggressive behavior showed significant differences from the control group in several areas of brain. These findings were most often seen in the following combination: decreased activity in the prefrontal cortex, increased activity in the anteromedial portions of the frontal lobes, leftsided increased activity in the basal ganglia and/or limbic system in comparison to the whole brain and focal abnormalities in the left temporal lobe. These findings indicate a possible cerebral perfusion profile for those who exhibit violent or aggressive behavior. Several case studies and the implications for treatment are discussed.
A case is presented of a 20-year-old man who became violent on many occasions after ingesting alcohol. On one occasion he committed an armed robbery. Two brain SPECT studies were performed: one when ...he was alcohol free, and one after he ingested alcohol in the same patternas the night of the crime. The "alcohol free" study revealed marked hyperactivity in the eingulate gyrus, right and left lateral frontal lobes, right and left lateral parietal lobes and the right lateral temporallobe. The "alcohol intoxication" study showed an overall dampening effect on the hyperactive areas of the brain, with only the anterior cingulate gyrus showing excessive activity. In addition, the right and left prefrontal cortex became hypoperfused, decreasing impulse control and judgment, as did the left and right temporal lobes, increasing the likelihood for aggression. This study suggests that this man may have been "self-medicating" an overactive brain, but in the process induced a state that increased the likelihood for aggressive behavior. This case study suggests the need for further research in the area of alcohol-induced violence and the potential usefulness of SPECT imaging, although no conclusions can be drawn from one case.
This article documents the muon reconstruction and identification efficiency obtained by the ATLAS experiment for 139
fb
-
1
of
pp
collision data at
s
=
13
TeV collected between 2015 and 2018 during ...Run 2 of the LHC. The increased instantaneous luminosity delivered by the LHC over this period required a reoptimisation of the criteria for the identification of prompt muons. Improved and newly developed algorithms were deployed to preserve high muon identification efficiency with a low misidentification rate and good momentum resolution. The availability of large samples of
Z
→
μ
μ
and
J
/
ψ
→
μ
μ
decays, and the minimisation of systematic uncertainties, allows the efficiencies of criteria for muon identification, primary vertex association, and isolation to be measured with an accuracy at the per-mille level in the bulk of the phase space, and up to the percent level in complex kinematic configurations. Excellent performance is achieved over a range of transverse momenta from 3 GeV to several hundred GeV, and across the full muon detector acceptance of
|
η
|
<
2.7
.
Marijuana abuse is common among young Americans and even more common among teenagers and adults with attention deficit/hyperactivity disorder (AD/HD). Many teenagers and young adults believe that ...marijuana is a safe substance to use despite a number of studies demonstrating cognitive impairment with chronic or heavy usage. Brain single photon emission computer tomography (SPECT) imaging is being used increasingly in psychiatry to study underlying functional brain problems, including AD/HD. SPECT provides information on cerebral blood flow and metabolic function. Brain SPECT studies were performed on 30 heavy marijuana users (who had used on at least a weekly basis for a minimum of one year) with AD/HD from an outpatient psychiatric clinic and 10 AD/HD controlgroup subjects matched for age and sex who had never used drugs. The threedimensional surface images were used in the analysis of the scans, and were blindly interpreted without knowledge of the clinical data. Decreased perfusion in the prefrontal cortex was the only abnormality seen in the AD/HD control group (80%). In the marijuana group, there was a similar decrease in the perfusion of the prefrontal cortex while performing the same concentration task (83%). However, the marijuana group also demonstrated marked decreased activity in the right and left temporal lobes. The severe and moderate ratings were fo und in the heaviest users, but not necessarily the longest users. This study demonstrates decreased cerebral perfusion in the temporal lobe regions of the brain on SPECT imaging from chronic marijuana usage.
PDF
