Epileptogenic Zone Localization With FDG PET Using a New Dynamic Parametric Analysis.

[F]fluorodeoxyglucose (F-FDG) positron emission tomography (PET) is part of the regular preoperative work-up in medically refractory epilepsy. As a complement to visual evaluation of PET, statistical parametric maps can help in the detection of the epileptogenic zone (EZ). However, software packages currently available are time-consuming and little intuitive for physicians.

PISCOM: a new procedure for epilepsy combining ictal SPECT and interictal PET.

Purpose: We present a modified version of the SISCOM procedure that uses interictal PET instead of interictal SPECT for seizure onset zone localization. We called this new nuclear imaging processing technique PISCOM (PET interictal subtracted ictal SPECT coregistered with MRI).

Methods: We retrospectively studied 23 patients (age range 4-61 years) with medically refractory epilepsy who had undergone MRI, ictal SPECT, interictal SPECT and interictal FDG PET and who had been seizure-free for at least 2 years after surgical treatment.

Optimization of the reconstruction parameters in [I]FP-CIT SPECT.

The aim of this work was to obtain a set of parameters to be applied in [I]FP-CIT SPECT reconstruction in order to minimize the error between standardized and true values of the specific uptake ratio (SUR) in dopaminergic neurotransmission SPECT studies. To this end, Monte Carlo simulation was used to generate a database of 1380 projection data-sets from 23 subjects, including normal cases and a variety of pathologies. Studies were reconstructed using filtered back projection (FBP) with attenuation correction and ordered subset expectation maximization (OSEM) with correction for different degradations (attenuation, scatter and PSF).

APOE-by-sex interactions on brain structure and metabolism in healthy elderly controls.

Background: The APOE effect on Alzheimer Disease (AD) risk is stronger in women than in men but its mechanisms have not been established. We assessed the APOE-by-sex interaction on core CSF biomarkers, brain metabolism and structure in healthy elderly control individuals (HC).

Methods: Cross-sectional study.

Improved image quality in pinhole SPECT by accurate modeling of the point spread function in low magnification systems.

Purpose: Single photon emission computed tomography (SPECT) has become an important noninvasive imaging technique in small-animal research. Due to the high resolution required in small-animal SPECT systems, the spatially variant system response needs to be included in the reconstruction algorithm. Accurate modeling of the system response should result in a major improvement in the quality of reconstructed images.

Dopamine transporter imaging in the aged rat: a [¹²³I]FP-CIT SPECT study.

Introduction: Rodent models are extensively used to assess the biochemical and physiological changes associated with aging. They play a major role in the development of therapies for age-related pathologies such as Parkinson's disease. To validate the usefulness of these animal models in aging or age-related disease research, the consistency of cerebral aging processes across species must be evaluated.

Infarct volume prediction using apparent diffusion coefficient maps during middle cerebral artery occlusion and soon after reperfusion in the rat.

Middle cerebral artery occlusion (MCAO) in rodents causes brain infarctions of variable sizes that depend on multiple factors, particularly in models of ischemia/reperfusion. This is a major problem for infarct volume comparisons between different experimental groups since unavoidable variability can induce biases in the results and imposes the use of large number of subjects. MRI can help to minimize these difficulties by ensuring that the severity of ischemia is comparable between groups.

In vivo evaluation of the dopaminergic neurotransmission system using [123I]FP-CIT SPECT in 6-OHDA lesioned rats.

The 6-hydroxydopamine (6-OHDA) rodent model of Parkinson's disease (PD) has been used to evaluate the nigrostriatal pathway. The aim of this work was to explore the relationship between the degree of 6-OHDA-induced dopaminergic degeneration and [(123)I]FP-CIT binding using single photon emission computed tomography (SPECT). Fourteen rats received a 6-OHDA injection (4 or 8 µg) into the left medial forebrain bundle.

Including anatomical and functional information in MC simulation of PET and SPECT brain studies. Brain-VISET: a voxel-based iterative method.

Monte Carlo (MC) simulation provides a flexible and robust framework to efficiently evaluate and optimize image processing methods in emission tomography. In this work we present Brain-VISET (Voxel-based Iterative Simulation for Emission Tomography), a method that aims to simulate realistic [ (99m) Tc]-SPECT and [ (18) F]-PET brain databases by including anatomical and functional information. To this end, activity and attenuation maps generated using high-resolution anatomical images from patients were used as input maps in a MC projector to simulate SPECT or PET sinograms.

Analytical, experimental, and Monte Carlo system response matrix for pinhole SPECT reconstruction.

Purpose: To assess the performance of two approaches to the system response matrix (SRM) calculation in pinhole single photon emission computed tomography (SPECT) reconstruction.

Methods: Evaluation was performed using experimental data from a low magnification pinhole SPECT system that consisted of a rotating flat detector with a monolithic scintillator crystal. The SRM was computed following two approaches, which were based on Monte Carlo simulations (MC-SRM) and analytical techniques in combination with an experimental characterization (AE-SRM).

Integration of advanced 3D SPECT modeling into the open-source STIR framework.

Purpose: The Software for Tomographic Image Reconstruction (STIR, http://stir.sourceforge.net) package is an open source object-oriented library implemented in C++.

Chronic intermittent hypoxia preserves bone density in a mouse model of sleep apnea.

Very recent clinical research has investigated whether obstructive sleep apnea (OSA) may modulate bone homeostasis but the few data available are conflicting. Here we report novel data obtained in a mouse study specifically designed to determine whether chronic intermittent hypoxia realistically mimicking OSA modifies bone mineral density (BMD). Normal male and female mice and orchidectomized mice (N=10 each group) were subjected to a pattern of high-frequency intermittent hypoxia (20s at 5% and 40s at 21%, 60 cycles/h) for 6h/day.

FocusDET, a new toolbox for SISCOM analysis. Evaluation of the registration accuracy using Monte Carlo simulation.

Subtraction of Ictal SPECT Co-registered to MRI (SISCOM) is an imaging technique used to localize the epileptogenic focus in patients with intractable partial epilepsy. The aim of this study was to determine the accuracy of registration algorithms involved in SISCOM analysis using FocusDET, a new user-friendly application. To this end, Monte Carlo simulation was employed to generate realistic SPECT studies.

Serial dopamine transporter imaging of nigrostriatal function in patients with idiopathic rapid-eye-movement sleep behaviour disorder: a prospective study.

Background: Serial dopamine transporter (DAT) imaging in patients with Parkinson's disease (PD) and other synucleinopathies shows progressive nigrostriatal dopaminergic dysfunction. Because idiopathic rapid-eye-movement (REM) sleep behaviour disorder (IRBD) can precede the classic symptoms of PD and other synucleinopathies, we postulated that serial DAT imaging in patients with IRBD could be used to detect decline in striatal tracer uptake, indicating progressive nigrostriatal cell degeneration.

Methods: In a prospective study, 20 patients with IRBD (mean age 70·55 years [SD 6·02]) underwent serial DAT imaging with (123)I-2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl)-nortropane ((123)I-FP-CIT) SPECT at baseline and again after 1·5 years and 3 years; 20 age-matched and sex-matched control participants (69·50 years [6·77]) underwent imaging at baseline and 3 years.

Subclinical nigrostriatal dopaminergic denervation in the cerebellar subtype of multiple system atrophy (MSA-C).

Nigrostriatal involvement is considered an additional feature in the new consensus criteria for the diagnosis of the cerebellar variant of multiple system atrophy (MSA-C). However, so far, only a few studies, which include a relative small number of patients, give support to this criterion. Our objective was to assess nigrostriatal dopaminergic innervation in patients with MSA-C without parkinsonism by use of dopamine transporter single photon emission computed tomography (DAT SPECT).

Differential brain glucose metabolic patterns in antipsychotic-naïve first-episode schizophrenia with and without auditory verbal hallucinations.

Background: Auditory verbal hallucinations (AVHs) are a core symptom of schizophrenia. Previous reports on neural activity patterns associated with AVHs are inconsistent, arguably owing to the lack of an adequate control group (i.e.

Geometrical and Monte Carlo projectors in 3D PET reconstruction.

Purpose: In the present work, the authors compare geometrical and Monte Carlo projectors in detail. The geometrical projectors considered were the conventional geometrical Siddon ray-tracer (S-RT) and the orthogonal distance-based ray-tracer (OD-RT), based on computing the orthogonal distance from the center of image voxel to the line-of-response. A comparison of these geometrical projectors was performed using different point spread function (PSF) models.

Fluordeoxyglucose-PET study in first-episode schizophrenic patients during the hallucinatory state, after remission and during linguistic-auditory activation.

Objectives: We tested the hypothesis that endogenous auditory verbal hallucinations (AVH) involve activation of auditory/linguistic association cortices that are usually activated by externally presented speech.

Methods: Nine neuroleptic-naive patients with first-episode schizophrenia (Diagnostic and Statistical Manual for Mental Disorders-IV criteria) with prominent AVH underwent three PET scans using F-fluordeoxyglucose (FDG): (i) shortly after presentation, while experiencing prominent and frequent AVH; (ii) after medication-induced remission (R), using a stable dose of risperidone; (iii) also in remission, during bilateral linguistic auditory activation (LAA) induced by spoken text mimicking the content of the hallucinations experienced while the first PET was performed, using headphones. PET scans were acquired using an Advanced-Nxi Scanner (GE Healthcare).

Assessment of SPM in perfusion brain SPECT studies. A numerical simulation study using bootstrap resampling methods.

Statistical parametric mapping (SPM) has become the technique of choice to statistically evaluate positron emission tomography (PET), functional magnetic resonance imaging (fMRI), and single photon emission computed tomography (SPECT) functional brain studies. Nevertheless, only a few methodological studies have been carried out to assess the performance of SPM in SPECT. The aim of this paper was to study the performance of SPM in detecting changes in regional cerebral blood flow (rCBF) in hypo- and hyperperfused areas in brain SPECT studies.

Quantification of dopaminergic neurotransmission SPECT studies with 123I-labelled radioligands. A comparison between different imaging systems and data acquisition protocols using Monte Carlo simulation.

Purpose: (123)I-labelled radioligands are commonly used for single-photon emission computed tomography (SPECT) imaging of the dopaminergic system to study the dopamine transporter binding. The aim of this work was to compare the quantitative capabilities of two different SPECT systems through Monte Carlo (MC) simulation.

Methods: The SimSET MC code was employed to generate simulated projections of a numerical phantom for two gamma cameras equipped with a parallel and a fan-beam collimator, respectively.

Test-retest variability and reliability of 123I-IBZM SPECT measurement of striatal dopamine D2 receptor availability in healthy volunteers and influence of iterative reconstruction algorithms.

Objective: 123I-IBZM single photon emission computed tomography (SPECT) is a widely used method to measure D(2) receptor availability. However, test-retest variability and reliability have not been reported yet. This study aimed to further characterize 123I-IBZM SPECT in healthy volunteers (HVs), by assessing (1) pseudoequilibrium interval after bolus injection; (2) normal specific uptake ratio (SUR) values using filtered-backprojection (FBP); and the iterative reconstruction algorithm ordered-subsets expectation maximization (OSEM); (3) test-retest variability and reliability (intraclass correlation coefficient); and (4) influence of OSEM on test-retest variability and reliability.

Characterization of the SPECT 5-HT2A receptor ligand 123I-R91150 in healthy volunteers: Part 1--pseudoequilibrium interval and quantification methods.

Unlabelled: With the aim of characterizing radioiodinated 4-amino-N-1-[3-(4-fluorophenoxy)propyl]-4-methyl-4-piperidinyl]5-iodo-2-methoxybenzamide ((123)I-R91150) as a SPECT ligand for subtype 2A of the 5-hydroxytryptamine receptor (5-HT(2A)), tracer kinetic compartmental analyses were compared with the tissue ratio method (TR). The pseudoequilibrium interval after a single bolus injection was identified, and a reference database of specific uptake ratio (SUR) values was obtained. Within-scan and between-subject variability was also assessed.

Absolute quantification in dopaminergic neurotransmission SPECT using a Monte Carlo-based scatter correction and fully 3-dimensional reconstruction.

Unlabelled: Dopamine transporter (DAT) ligands have been developed for in vivo imaging of the dopaminergic system in SPECT. Although the visual analysis of SPECT images is, in general, suitable for clinical assessment, the accurate quantification of the striatal uptake might increase the sensitivity of the technique and help in the early diagnosis, follow-up, and eventual treatment response of Parkinson's disease (PD). This work is focused on assessment of the quantification of specific uptake of (99m)Tc-DAT ligands when compensation for all degrading phenomena is performed.

Iterative reconstruction with correction of the spatially variant fan-beam collimator response in neurotransmission SPET imaging.

The dopamine transporter (DAT) has been shown to be a sensitive indicator of nigrostriatal dopamine function. Although visual inspection is often sufficient to assess DAT imaging, quantification could improve the diagnostic accuracy of single-photon emission tomography (SPET) studies of the dopaminergic system. The aim of this study was to assess the accuracy of quantification of the striatal/background uptake ratio when correction for attenuation, scatter and spatially variant fan-beam collimator response is performed in technetium-99m and iodine-123 SPET imaging.