Post traumatic brain perfusion SPECT analysis using reconstructed ROI maps of radioactive microsphere derived cerebral blood flow and statistical parametric mapping

<p>Abstract</p> <p>Background</p> <p>Assessment of cerebral blood flow (CBF) by SPECT could be important in the management of patients with severe traumatic brain injury (TBI) because changes in regional CBF can affect outcome by promoting edema formation and intracranial pressure elevation (with cerebral hyperemia), or by causing secondary ischemic injury including post-traumatic stroke. The purpose of this study was to establish an improved method for evaluating regional CBF changes after TBI in piglets.</p> <p>Methods</p> <p>The focal effects of moderate traumatic brain injury (TBI) on cerebral blood flow (CBF) by SPECT cerebral blood perfusion (CBP) imaging in an animal model were investigated by parallelized statistical techniques. Regional CBF was measured by radioactive microspheres and by SPECT 2 hours after injury in sham-operated piglets versus those receiving severe TBI by fluid-percussion injury to the left parietal lobe. Qualitative SPECT CBP accuracy was assessed against reference radioactive microsphere regional CBF measurements by map reconstruction, registration and smoothing. Cerebral hypoperfusion in the test group was identified at the voxel level using statistical parametric mapping (SPM).</p> <p>Results</p> <p>A significant area of hypoperfusion (P < 0.01) was found as a response to the TBI. Statistical mapping of the reference microsphere CBF data confirms a focal decrease found with SPECT and SPM.</p> <p>Conclusion</p> <p>The suitability of SPM for application to the experimental model and ability to provide insight into CBF changes in response to traumatic injury was validated by the SPECT SPM result of a decrease in CBP at the left parietal region injury area of the test group. Further study and correlation of this characteristic lesion with long-term outcomes and auxiliary diagnostic modalities is critical to developing more effective critical care treatment guidelines and automated medical imaging processing techniques.</p

Metabolomics of Oxidative Stress in Recent Studies of Endogenous and Exogenously Administered Intermediate Metabolites

Aerobic metabolism occurs in a background of oxygen radicals and reactive oxygen species (ROS) that originate from the incomplete reduction of molecular oxygen in electron transfer reactions. The essential role of aerobic metabolism, the generation and consumption of ATP and other high energy phosphates, sustains a balance of approximately 3000 essential human metabolites that serve not only as nutrients, but also as antioxidants, neurotransmitters, osmolytes, and participants in ligand-based and other cellular signaling. In hypoxia, ischemia, and oxidative stress, where pathological circumstances cause oxygen radicals to form at a rate greater than is possible for their consumption, changes in the composition of metabolite ensembles, or metabolomes, can be associated with physiological changes. Metabolomics and metabonomics are a scientific disciplines that focuse on quantifying dynamic metabolome responses, using multivariate analytical approaches derived from methods within genomics, a discipline that consolidated innovative analysis techniques for situations where the number of biomarkers (metabolites in our case) greatly exceeds the number of subjects. This review focuses on the behavior of cytosolic, mitochondrial, and redox metabolites in ameliorating or exacerbating oxidative stress. After reviewing work regarding a small number of metabolites—pyruvate, ethyl pyruvate, and fructose-1,6-bisphosphate—whose exogenous administration was found to ameliorate oxidative stress, a subsequent section reviews basic multivariate statistical methods common in metabolomics research, and their application in human and preclinical studies emphasizing oxidative stress. Particular attention is paid to new NMR spectroscopy methods in metabolomics and metabonomics. Because complex relationships connect oxidative stress to so many physiological processes, studies from different disciplines were reviewed. All, however, shared the common goal of ultimately developing “omics”-based, diagnostic tests to help influence therapies

Computer phantom study of brain PET glucose metabolism imaging using a rotating SPECT/PET camera

Positron emission tomography (PET) with [18F] fluoro-deoxy-glucose (FDG) provides information about glucose metabolism and is used to measure tissue glucose kinetics in the brain. The recent interest in hybrid SPECT/PET systems emerged as a practical approach to reduce the high cost of purchasing a dedicated ring-detector PET system. We have implemented interpolation methods for processing the projection data that could potentially reduce artifacts when reconstructing a dynamic imaging sequence in a PET study from a dual-head rotating SPECT/PET system. The computer simulations predict that parameter estimates from the dedicated PET system will be superior to results using the rotating camera system. However, the rotating camera system using projection interpolation may approach the accuracy of the dedicated PET system if the data noise is below 20%

Quantitation of Metabolic Change in Serial FDG-PET Brain Scans of Pediatric Patients with Traumatic Brain Injury

The aim of this research was to develop a method to quantitate the changes in regional brain metabolism on serial FDG-PET scans in children with Traumatic Brain Injury (TBI) in order to determine their response to treatment with psycho stimulant medication. Methods: A Fusion-Based Image Subtraction (FBIS) technique was developed in order to calculate the differences in metabolism between baseline and follow-up scans. The FDG-PET brain images were count normalized to account for differences in the injected activity. Image registration was then performed using a 3D normalized mutual information algorithm and subsequently the fused images were subtracted on a pixel by pixel basis. FBIS extracted areas of increased or decreased metabolism were then compared to a database of normal subjects using NeuroQ (Syntermed, Inc.) and analyzed for statistical significance in cluster areas defined by a standard brain template. Results: Validation of the technique was performed using images from 15 pediatric cases with severe TBI who had baseline (pre-treatment) and follow-up (post-treatment) scans. The FBIS technique was found to be accurate in detecting and localizing the statistically significant changes in regional cerebral metabolism and provided useful data that could be applied clinically. Conclusions: The developed FBIS method identified and quantified areas of regional brain metabolic change thus providing a way to evaluate the effects of pharmacologic treatment in children with TBI. This quantitative technique could be used as an adjunct tool to enhance the interpretation of FDG-PET brain images and aid the referring clinician to assess the response to pharmacologic treatment

Selective brain cooling increases cortical cerebral blood flow in rats

To evaluate the effect of selective brain cooling on cortical cerebral blood flow, we reduced brain temperature in nitrous oxide anesthetized adult rats using a high speed fan while keeping rectal temperature at 37-38 degrees C. During selective brain cooling, cortical cerebral blood flow, as measured by laser-Doppler flowmetry, increased to 215 +/- 26% (mean +/- SE) of baseline at a cortical brain temperature of 30.9 +/- 0.5 degrees C and a rectal temperature of 37.5 +/- 0.1 degrees C. During rewarming, as brain temperature increased, cortical cerebral blood flow decreased. The cerebral vasodilatory response to hypothermia may explain its protective effects during and after cerebral ischemia