John Ollinger - Academia.edu (original) (raw)

Papers by John Ollinger

Neuropsychology (journal), 2023

The Journal of Nuclear Medicine, May 1, 1994

We have investigated the quantitative accuracy of fully 3D PET using model-based scatter correcti... more We have investigated the quantitative accuracy of fully 3D PET using model-based scatter correction by measuring the half-life of Ga-68 in the presence of scatter from F-18. The inner chamber of a Data Spectrum cardiac phantom was filled with 18.5 MBq of Ga-68. The outer chamber was filled with an equivalent amount of F-18. The cardiac phantom was placed in a 22x30.5 cm elliptical phantom containing anthropomorphic lung inserts filled with a water-Styrofoam mixture. Ten frames of dynamic data were collected over 13.6 hours on Siemens-CTI 953B scanner with the septa retracted. The data were corrected using model-based scatter correction, which uses the emission images, transmission images and an accurate physical model to directly calculate the scatter distribution. Both uncorrected and corrected data were reconstructed using the Promis algorithm. The scatter correction required 4.3% of the total reconstruction time. The scatter fraction in a small volume of interest in the center of the inner chamber of the cardiac insert rose from 4.0% in the first interval to 46.4% in the last interval as the ratio of F-18 activity to Ga-68 activity rose from 1:1 to 33:1. Fitting a single exponential to the last three data points yields estimates of themore » half-life of Ga-68 of 77.01 minutes and 68.79 minutes for uncorrected and corrected data respectively. Thus, scatter correction reduces the error from 13.3% to 1.2%. This suggests that model-based scatter correction is accurate in the heterogeneous attenuating medium found in the chest, making possible quantitative, fully 3D PET in the body.« less

Proceedings of SPIE, Jun 26, 1992

We have developed a technique for finding maximum-likelihood estimates of DNA restriction- fragme... more We have developed a technique for finding maximum-likelihood estimates of DNA restriction- fragment mobilities from images of fluorescently stained electrophoretic gels. Gel images are acquired directly using a CCD camera. The likelihood model incorporates the Poisson nature of the photon counts and models the fluorescence intensity as the superposition of Gaussian functions (corresponding to the fragment bands) of varying magnitude and width. An expectation-maximization algorithm is used to find maximum-likelihood estimates of the number of fragments, fragment mobilities, widths of the bands, background contributions, and DNA concentration. This approach has several advantages. Closely spaced and overlapping fragments are accurately resolved into their components. No a priori knowledge of the number or positions of fragments is required. Fragment lengths estimated by the maximum-likelihood method from experimental data were compared to the known lengths of fragments generated from three different restriction digests of bacteriophage (lambda) DNA. Preliminary results using the maximum-likelihood method indicate residual sizing errors on the order of 1%.

A method is presented that directly calculates the mean number of scattered coincidences in data ... more A method is presented that directly calculates the mean number of scattered coincidences in data acquired with fully 3D positron emission tomography (PET). This method uses a transmission scan, an emission scan, the physics of Compton scatter, and a mathematical model of the scanner in a forward calculation of the number of events for which one photon has undergone a single Compton interaction. The distribution of events for which multiple Compton interactions have occurred is modelled as a linear transformation of the single-scatter distribution. Computational efficiency is achieved by sampling at rates no higher than those required by the scatter distribution and by implementing the algorithm using look-up tables. Evaluation studies in phantoms with large scatter fractions show that the method yields images with quantitative accuracy equivalent to that of slice-collimated PET in clinically useful times.

ISMRM Annual Meeting

Sleep disturbances are common following traumatic brain injury (TBI). The intent of this study is... more Sleep disturbances are common following traumatic brain injury (TBI). The intent of this study is to characterize the role of the noradrenergic locus coeruleus (LC) for sleep maintenance in service members following mild TBI by associating microstructural features, derived from diffusion MRI, of the LC–noradrenergic (NA) system with objective sleep measures. We found that severity of sleep apnea, particularly in rapid eye movement stage during sleep, significantly correlated with microstructural changes in the LC pathways to hypothalamus in mTBI participants. This result suggests sleep apnea following mild TBI may be modulated by sympathetic activity via pathways interconnecting LC and hypothalamus.

NeuroImage, 1998

Introduction. Neuropsychological studies have suggested that left-Iateralized brain lesions produ... more Introduction. Neuropsychological studies have suggested that left-Iateralized brain lesions produced memory deficits for verbal material, whereas right-Iateralized lesions do so for nonverbal material [I]. By contrast, functional imaging findings have suggested lateralization of brain involvement according to the temporal stage of memory function. These findings led to the conception of the Hemispheric EncodingJRetrieval Asymmetry (HERA) model [2]. The HERA model asserts that left frontal regions are preferentially involved in memory encoding, whereas right frontal regions are preferentially involved in retrieval. The present study attempts to reconcile these conflicting hypotheses. fMRI was used to determine whether different encoding conditions would affectlateralization of frontal activations. We examined three encoding tasks in which materials were manipulated to place varying demands on verbal and nonverbal encoding: encoding of words, namable line-drawn objects, and unfamiliar faces.

Archives of Clinical Neuropsychology, Aug 17, 2022

Objective: Determine whether glucose uptake as measured by 18F-Fluorodeoxyglucose-positron emissi... more Objective: Determine whether glucose uptake as measured by 18F-Fluorodeoxyglucose-positron emission tomography (FDG-PET) imaging is associated with cognitive performance and mild neurocognitive disorder (MNCD) in active-duty service members with a history of mild traumatic brain injury (mTBI). Method: 287 patients with a history of mTBI underwent FDG-PET scans at rest and neuropsychological testing at the National Intrepid Center of Excellence at Walter Reed National Military Medical Center. Glucose uptake in bilateral frontal, parietal, occipital, and temporal lobes, and 58 cortical/cerebellar regions were correlated with seven neuropsychological composite scores, with and without relevant covariates. Results: Prior to correction for multiple comparisons, perceptual reasoning correlated with bilateral hippocampi glucose uptake (rs:.141-.165, ps<.03), processing speed was inversely related to glucose uptake in the left temporal lobe (r=-.134, p=.034), working memory was related to glucose uptake in the left parietal, temporal, and occipital lobes (rs:.128-.140, ps<.05). Partial correlations between cognition and the 56 cortical/cerebellar regions of interest (ROIs) were not significant after correction for multiple comparisons. Increased glucose uptake in the bilateral pericalcarine, left superior temporal, and right occipital, superior parietal, transverse temporal, precuneus, and lingual cortices was related to increased likelihood of MNCD (ORs:41.02-2263.7, ps<.05); however, did not survive correction for multiple comparisons. Conclusions: After correction for multiple comparisons, there was no significant relationship between regional glucose uptake and neurocognitive performance or MNCD. Glucose uptake as measured by FDG-PET is not related to cognitive performance in active-duty service members with a remote history of mTBI and may have limited clinical utility for these individuals.

Psychiatry Research: Neuroimaging, Dec 1, 2022

IEEE Signal Processing Magazine, 1997

Journal of Neurotrauma, Jul 15, 2019

Brain venous volume above the lateral ventricle in military patients with traumatic brain injury ... more Brain venous volume above the lateral ventricle in military patients with traumatic brain injury (TBI) was assessed using two segmentation approaches on susceptibility weighted images (SWI) and quantitative susceptibility maps (QSM). This retrospective study included a total of 147 subjects: 14 patients with severe TBI; 38 patients with moderate TBI, 58 patients with mild TBI (28 with blast-related injuries and 30 with non-blast-related injuries), and 37 control subjects without history of TBI. Using the multiscale vessel enhancement filter on SWI images, patients with severe TBI demonstrated significantly higher segmented venous volumes compared with controls. Using a threshold approach on QSM images, TBI patients with different severities all demonstrated increased segmented volumes compared with control subjects: in the whole brain (severe, p = 0.001; moderate, p = 0.008; mild, p = 0.042, compared with controls), in the left hemisphere (severe, p = 0.01; moderate, p = 0.038, compared with controls), in the right hemisphere (severe, p = 0.001; moderate, p = 0.013; mild, p = 0.027, compared with controls). While segmented volumes on SWI appear to overlay directly on the visualized venous structures, the QSM-derived segments also encompass some perivascular and deep white matter areas. This might represent the damage in the perivascular regions associated with iron deposition or astroglial scarring.

Brain communications, May 2, 2022

The purpose of this study was to analyze quantitative diffusion tensor imaging measures across th... more The purpose of this study was to analyze quantitative diffusion tensor imaging measures across the spectrum of traumatic brain injury severity and evaluate their trajectories in military service members. Participants were 96 U.S. military service members and veterans who had sustained a mild traumatic brain injury [including complicated mild traumatic brain injury (n = 16) and uncomplicated mild traumatic brain injury (n = 68)], moderate-severe traumatic brain injury (n = 12), and controls (with or without orthopaedic injury, n = 39). All participants had been scanned at least twice, with some receiving up to five scans. Both whole brain voxel-wise analysis and tract-of-interest analysis were applied to assess the group differences of diffusion tensor imaging metrics, and their trajectories between time points of scans and days since injury. Linear mixed modelling was applied to evaluate cross-sectional and longitudinal diffusion tensor imaging metrics changes within and between groups using both tract-of-interest and voxel-wise analyses. Participants with moderate to severe traumatic brain injury had larger white matter disruption both in superficial subcortical and deep white matter, mainly over the anterior part of cerebrum, than those with mild traumatic brain injury, both complicated and uncomplicated, and there was no evidence of recovery over the period of follow-ups in moderate-severe traumatic brain injury, but deterioration was possible. Participants with mild traumatic brain injury had white matter microstructural changes, mainly in deep central white matter over the posterior part of cerebrum, with more spatial involvement in complicated mild traumatic brain injury than in uncomplicated mild traumatic brain injury and possible brain repair through neuroplasticity, e.g. astrocytosis with glial processes and glial scaring. Our results did not replicate ‘V-shaped’ trajectories in diffusion tensor imaging metrics, which were revealed in a previous study assessing the sub-acute stage of brain injury in service members and veterans following military combat concussion. In addition, non-traumatic brain injury controls, though not demonstrating any evidence of sustaining a traumatic brain injury, might have transient white matter changes with recovery afterward. Our results suggest that white matter integrity following a remote traumatic brain injury may change as a result of different underlying mechanisms at the microstructural level, which can have a significant consequence on the long-term well beings of service members and veterans. In conclusion, longitudinal diffusion tensor imaging improves our understanding of the mechanisms of white matter microstructural changes across the spectrum of traumatic brain injury severity. The quantitative metrics can be useful as guidelines in monitoring the long-term recovery. Graphical AbstractOpen in a separate window

Sleep, 2020

Introduction While sleep disorders occur in 40–70% of chronic traumatic brain injury (TBI) patien... more Introduction While sleep disorders occur in 40–70% of chronic traumatic brain injury (TBI) patients, the pathophysiology remains unknown. Increasingly, DTI has been used to evaluate gray matter structures, but no prior studies have evaluated hypothalamic regions in TBI. We hypothesized that TBI patients with poor sleep quality by questionnaire and/or polysomnography (PSG) may have structural injury to hypothalamic sleep circuitry and that this may be detectable by diffusion magnetic resonance imaging (dMRI). We examined diffusion tensor parameters in warfighters using dMRI within the hypothalamus of poor sleepers and compared them to good sleepers. Methods A retrospective review of 92 warfighters with blast TBI and loss of consciousness included demographics, structural MRI, dMRI, PSG and Pittsburgh Sleep Quality Index (PSQI) questionnaire. Acquisition of diffusion-weighted and structural data was performed with three Tesla MRI. Using the California Institute of Technology probabili...

Archives of Clinical Neuropsychology, Aug 31, 2015

Objective: The purpose of this study was to examine the relation between white matter integrity o... more Objective: The purpose of this study was to examine the relation between white matter integrity of the brain, as measured by diffusion tensor imaging (DTI), and postconcussion symptom reporting following traumatic brain injury (TBI). Method: Participants were 34 U.S. service members (Age: M ¼ 29.7 years, SD ¼ 7.9, 97.1% male) who sustained a mild-moderate TBI; enrolled from Walter Reed National Military Medical Center. Participants completed the Neurobehavioral Symptom Inventory (NSI) and DTI, on average, 4.6 months post-injury (SD ¼ 3.2). Participants were divided into groups based on DSM-IV symptom criteria for postconcussional disorder (PCD): (a) PCD-Present (n ¼ 10) and (b) PCD-Absent (n ¼ 24). A subgroup of 19 participants was also evaluated at 12 months post-injury (8 PCD-Present, 11 PCD-Absent). Results: There were significant differences (p , .05) and/or meaningful effect sizes (d..50) for approximately half of the 18 regions of interest (ROI) when using measures of axial diffusivity (AD; d ¼ .55-.95), mean diffusivity (MD; d ¼ .52-1.03), and radial diffusivity (RD; d ¼ .51-.75; PCD-Present. PCD-Absent). However, when considering all 18 ROIs simultaneously, there were no group differences (p. .05) for the mean number of ROIs that fell within normal limits for AD, MD, RD, and Fractional Anisotropy (p. .05). Longitudinal comparisons revealed no association between PCD and the number of DTI measures that fell within normal limits from baseline to 12 month follow-up. Conclusion: These results suggest that there may be some association between reduced white matter integrity in the brain and self-reported postconcussion symptoms within the first 12 months following mild-moderate TBI for some people. However, in this sample, this association was weak at best.

Utilities to work with files from BIOPAC's AcqKnowlege software

Tractography of Richardson-Lucy Spherical Deconvolution under Rician noise of Sparse Multiple q-s... more Tractography of Richardson-Lucy Spherical Deconvolution under Rician noise of Sparse Multiple q-shell Diffusion Imaging Ping-Hong Yeh, Erick Jorge CanalesRodríguez, John Morissette, Arman A. Taheri, Li-Wei Kuo, Fang-Cheng Yeh, Wei Lui, John Ollinger, Terrence Oakes, Mark L. Ettenhofer, and Gerard Riedy Henry Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, United States, FIDMAG Research Foundation, Germanes Hospitalaries and CIBERSAM, Barcelona, Spain, National Intrepid Center of Excellence, Walter Reed National Military Medical Center, MD, United States, National Health Research Institutes, Taiwan, Carnegie Mellon University, PA, United States, Uniformed Services University of the Health Sciences, MD, United States

Brain Connectivity

INTRODUCTION Comorbid mild traumatic brain injury (mTBI) and post-traumatic stress disorder (PTSD... more INTRODUCTION Comorbid mild traumatic brain injury (mTBI) and post-traumatic stress disorder (PTSD) are common in military service members. The aim of this study is to investigate brain metabolic inter-relationships in service members with and without persistent PTSD symptoms following mTBI using 18F-fluorodeoxyglucose positron emission tomography. METHODS Service members (n=408) diagnosed with mTBI were studied retrospectively. Principal component analysis was applied to identify latent metabolic systems, and the associations between metabolic latent systems and self-report measures of post-concussive and PTSD symptoms were evaluated. Participants were divided into two groups based on DSM-IV-TR criteria for PTSD, and structural equation modeling was performed to test a priori hypotheses on metabolic inter-relationships among the brain regions in the cortico-limbic circuitry responsible for top-down control and bottom-up emotional processing. The differences in metabolic inter-relationships between age-matched PTSD-absent (n=204) and PTSD-present (n=204) groups were evaluated. RESULTS FDG uptake in the temporo-limbic system was positively correlated with post-concussive and hyperarousal symptoms. For the bottom-up emotional processing, the insula and amygdala-hippocampal complex in PTSD-present group had stronger metabolic inter-relationships with the bilateral rostral anterior cingulate, left lingual, right lateral occipital, and left superior temporal cortices, but a weaker relationship with the right precuneus cortex, compared to PTSD-absent group. For the top-down control, PTSD-present group had decreased metabolic engagements of the dorsolateral prefrontal cortex on the amygdala. DISCUSSION Our results suggest altered metabolic inter-relationships in the cortico-limbic circuitry in mTBI subjects with persistent PTSD symptoms, which may underlie the pathophysiological mechanisms of comorbid mTBI and PTSD.

Military Medicine

Introduction To address the military gap in the standardized collection of lifetime blast exposur... more Introduction To address the military gap in the standardized collection of lifetime blast exposures across clinical and research endeavors, researchers at the National Intrepid Center of Excellence (NICoE) completed a quality improvement project that utilized systematic, iterative focus groups that leveraged the input from various stakeholders including subject matter experts, clinical providers, and service members (SMs) to develop a comprehensive, self-report blast exposure inventory that could be completed within 5-10 minutes. This manuscript outlines the process of the development of this inventory. Materials and Methods This project included three phases of focus groups that occurred at the NICoE between August 2020 and March 2021 to collect feedback and input from relevant military stakeholders. The study team utilized related assessments available in the literature, together with clinical experience with the NICoE patient population, to inform the development of an initial dr...

Sleep, 2021

Introduction Traumatic brain injury (TBI) plagues service members in times of war and training. D... more Introduction Traumatic brain injury (TBI) plagues service members in times of war and training. Diagnosis and management of TBI remain challenging, with many suffering from sleep disorders. We hypothesized that TBI-related damage to the hypothalamus, a master regulator of breathing and sleep, could be related to post-TBI obstructive sleep apnea (OSA) and serve as a pathophysiological biomarker for a subpopulation of OSA patients. Methods This was a retrospective study of warfighters with TBI from the National Intrepid Center of Excellence (NICoE). Subjects were identified by severe TBI on neuroimaging and compared against a control group without TBI. All subjects underwent screening polysomnography (PSG). MRI was acquired via 3T scanner. The hypothalamus was automatically segmented using a diffeomorphic algorithm. DTI scalar values were analyzed with scalar t-tests between subjects and controls. Generalized linear modeling with DTI scalar values was used to predict AHI in subjects. ...

Frontiers in Physiology, 2021

ObjectiveTo characterize the relationship between persistent post-traumatic headache (pPTH) and t... more ObjectiveTo characterize the relationship between persistent post-traumatic headache (pPTH) and traumatic cerebrovascular injury (TCVI) in chronic traumatic brain injury (TBI). Cerebrovascular reactivity (CVR), a measure of the cerebral microvasculature and endothelial cell function, is altered both in individuals with chronic TBI and migraine headache disorder (Amyot et al., 2017; Lee et al., 2019b). The pathophysiologies of pPTH and migraine are believed to be associated with chronic microvascular dysfunction. We therefore hypothesize that TCVI may contribute to the underlying migraine-like mechanism(s) of pPTH.Materials and Methods22 moderate/severe TBI participants in the chronic stage (>6 months) underwent anatomic and functional magnetic resonance imaging (fMRI) scanning with hypercapnia gas challenge to measure CVR as well as the change in CVR (ΔCVR) after single-dose treatment of a specific phosphodiesterase-5 (PDE-5) inhibitor, sildenafil, which potentiates vasodilation ...