Burmese python target reflectivity compared to natural Florida foliage background reflectivity.

The Florida Everglades is infested with Burmese pythons caused by the release of exotic pets in the 1980s. The current estimates are between 30,000 and 300,000 pythons, where the result is a severe decline in Everglade mammals: 90% reductions in raccoon, opossum, bobcats, and foxes. The marsh rabbits are completely gone.

Left Ventricular Remodeling Results in Homogenization of Myocardial Work Distribution.

Background: The interaction between regional left ventricular (LV) myocardial work and metabolism in remodeled hearts has not yet been well established. Our aim was to investigate the effect of inhomogeneous LV work distribution on regional metabolism and remodeling in our animal model with reversible dyssynchrony due to pacing.

Methods: In 12 sheep, 8 weeks of right atrial and right ventricular free wall (DDD) pacing lead to LV dilatation, a thinned septum, and thickened lateral wall.

Papillary muscles contribute significantly more to left ventricular work in dilated hearts.

Aims: Left ventricular (LV) dilatation results in increased sphericity and affects position and orientation of papillary muscles (PMs), which may influence their performed work. The aim of this study was to assess the contribution of PM to LV function and its changes with dilatation.

Methods And Results: Fifteen sheep were investigated.

Sheep can be used as animal model of regional myocardial remodeling and controllable work.

Background: Pacing the right heart has been shown to induce reversible conduction delay and subse-quent asymmetric remodeling of the left ventricle (LV) in dogs and pigs. Both species have disadvantages in animal experiments. Therefore the aim of this study was to develop a more feasible and easy-to-use animal model in sheep.

Evaluation of Parallel Level Sets and Bowsher's Method as Segmentation-Free Anatomical Priors for Time-of-Flight PET Reconstruction.

In this article, we evaluate Parallel Level Sets (PLS) and Bowsher's method as segmentation-free anatomical priors for regularized brain positron emission tomography (PET) reconstruction. We derive the proximity operators for two PLS priors and use the EM-TV algorithm in combination with the first order primal-dual algorithm by Chambolle and Pock to solve the non-smooth optimization problem for PET reconstruction with PLS regularization. In addition, we compare the performance of two PLS versions against the symmetric and asymmetric Bowsher priors with quadratic and relative difference penalty function.

Lesion quantification and detection in myocardial (18)F-FDG PET using edge-preserving priors and anatomical information from CT and MRI: a simulation study.

Background: The limited spatial resolution of the clinical PET scanners results in image blurring and does not allow for accurate quantification of very thin or small structures (known as partial volume effect). In cardiac imaging, clinically relevant questions, e.g.

Early decrease of type 1 cannabinoid receptor binding and phosphodiesterase 10A activity in vivo in R6/2 Huntington mice.

Several lines of evidence imply early alterations in endocannabinoid and phosphodiesterase 10A (PDE10A) signaling in Huntington disease (HD). Using [(18)F]MK-9470 and [(18)F]JNJ42259152 small-animal positron emission tomography (PET), we investigated for the first time cerebral changes in type 1 cannabinoid (CB1) receptor binding and PDE10A levels in vivo in presymptomatic, early symptomatic, and late symptomatic HD (R6/2) mice, in relation to glucose metabolism ([(18)F]FDG PET), brain morphology (magnetic resonance imaging) and motor function. Ten R6/2 and 16 wild-type (WT) mice were investigated at 3 different time points between the age of 4 and 13 weeks.

Detection and quantification of acute reperfused myocardial infarction in rabbits using DISA-SPECT/CT and 3.0T cardiac MRI.

Background: Necrosis avid tracer (123)I-hypericin ((123)I-HYP) enables hot-spot imaging on acute myocardial infarction (MI). We explored dual-isotope simultaneous acquisition single photon emission computed tomography/computed tomography (DISA-SPECT/CT) by using (123)I-HYP and standard (99m)Tc-sestamibi ((99m)Tc-MIBI), in comparison with cardiac magnetic resonance imaging (cMRI), autoradiography (AutoRx) and histomorphometry.

Methods: Acute MI was induced by 90-min coronary artery occlusion and 24-h reperfusion in 9 rabbits.

Construction and evaluation of quantitative small-animal PET probabilistic atlases for [¹⁸F]FDG and [¹⁸F]FECT functional mapping of the mouse brain.

Unlabelled: Automated voxel-based or pre-defined volume-of-interest (VOI) analysis of small-animal PET data in mice is necessary for optimal information usage as the number of available resolution elements is limited. We have mapped metabolic ([(18)F]FDG) and dopamine transporter ([(18)F]FECT) small-animal PET data onto a 3D Magnetic Resonance Microscopy (MRM) mouse brain template and aligned them in space to the Paxinos co-ordinate system. In this way, ligand-specific templates for sensitive analysis and accurate anatomical localization were created.

Comparative study of iodine-123-labeled hypericin and (99m)Tc-labeled hexakis [2-methoxy isobutyl isonitrile] in a rabbit model of myocardial infarction.

Identification of myocardial infarction (MI) by imaging is critical for clinical management of ischemic heart disease. Iodine-123-labeled hypericin (¹²³I-Hyp) is a new potent infarct avid agent. We sought to compare target selectivity and organ distribution between ¹²³I-Hyp and the myocardial perfusion agent, technetium-99m-labeled hexakis [2-methoxy isobutyl isonitrile] ((99m)Tc-Sestamibi) in rabbits with acute MI.

Fuzzy multi-class statistical modeling for efficient total lesion metabolic activity estimation from realistic PET images.

18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) has become the de facto standard for current clinical therapy follow up evaluations. In pursuit of robust biomarkers for predicting early therapy response, an efficient marker quantification procedure is certainly a necessity. Among various PET derived markers, the clinical investigations indicated that the total lesion metabolic activity (TLA) of a tumor lesion has a good prognostic value in several longitudinal studies.

Evaluation of three MRI-based anatomical priors for quantitative PET brain imaging.

In emission tomography, image reconstruction and therefore also tracer development and diagnosis may benefit from the use of anatomical side information obtained with other imaging modalities in the same subject, as it helps to correct for the partial volume effect. One way to implement this, is to use the anatomical image for defining the a priori distribution in a maximum-a-posteriori (MAP) reconstruction algorithm. In this contribution, we use the PET-SORTEO Monte Carlo simulator to evaluate the quantitative accuracy reached by three different anatomical priors when reconstructing positron emission tomography (PET) brain images, using volumetric magnetic resonance imaging (MRI) to provide the anatomical information.

Multi-pinhole SPECT calibration: influence of data noise and systematic orbit deviations.

The geometry of a single pinhole SPECT system with circular orbit can be uniquely determined from a measurement of three point sources, provided that at least two inter-point distances are known. In contrast, it has been shown mathematically that, for a multi-pinhole SPECT system with circular orbit, only two point sources are needed, and the knowledge of the distance between them is not required. In this paper, we report that this conclusion only holds if the motion of the camera is perfectly circular.

Radiolabeling and preliminary biological evaluation of a (99m)Tc(CO)(3) labeled 3,3'-(benzylidene)-bis-(1H-indole-2-carbohydrazide) derivative as a potential SPECT tracer for in vivo visualization of necrosis.

N,N'-bis(diethylenetriamine pentaacetic acid)-3,3'-(benzylidene)-bis-(1H-indole-2-carbohydrazide) (bis-DTPA-BI) was radiolabeled with (99m)Tc(CO)(3). The resulting (99m)Tc(CO)(3)-bis-DTPA-BI was characterized (LC-MS) and evaluated as a potential SPECT tracer for imaging of necrosis in Wistar rats with a reperfused partial liver infarction and Wistar rats with ethanol induced muscular necrosis. To study the specificity, uptake of (99m)Tc(CO)(3)-bis-DTPA-BI was also studied in a mouse model of Fas-mediated hepatic apoptosis.

Preclinical imaging of therapy response using metabolic and apoptosis molecular imaging.

Purpose: Early after therapy, 2-deoxy-2-[(18)F]fluoro-D-glucose ([(18)F]FDG) imaging is not always reliable due to the influx of inflammatory cells while apoptosis imaging offers a direct and early measurement of therapy effects. This study uses an improved apoptosis probe ((99m)Tc-hAnxA5) in combination with [(18)F]FDG imaging to evaluate therapy response.

Procedures: Daudi tumor tissue was implanted in the spleen of SCID mice.

Comparison between parallel hole and rotating slat collimation: analytical noise propagation models.

We have previously proposed a method to compare tomographic systems. It is assumed that each system acquires a tomographic scan of a certain tracer distribution in the same acquisition time. From this scan, each system is forced to reconstruct an image with a predefined spatial resolution.

Site-specific labeling of 'second generation' annexin V with 99mTc(CO)3 for improved imaging of apoptosis in vivo.

In this study 'second generation' AnxV was specifically labeled with (99m)Tc in three different ways outside the binding region of the protein to obtain an improved target-to-background activity ratio. The compounds were tested in vitro and in vivo in normal mice and in a model of hepatic apoptosis (anti-Fas mAb). The apoptosis binding was most prominent for the HIS-tagged 'second generation' AnxV labeled with (99m)Tc(CO)(3) in comparison to (99m)Tc-HYNIC-cys-AnxV and (99m)Tc(CO)(3)-DTPA-cys-AnxV.

Fisher information-based evaluation of image quality for time-of-flight PET.

The use of time-of-flight (TOF) information during positron emission tomography (PET) reconstruction has been found to improve the image quality. In this work we quantified this improvement using two existing methods: 1) a very simple analytical expression only valid for a central point in a large uniform disk source and 2) efficient analytical approximations for postfiltered maximum likelihood expectation maximization (MLEM) reconstruction with a fixed target resolution, predicting the image quality in a pixel or in a small region of interest based on the Fisher information matrix. Using this latter method the weighting function for filtered backprojection reconstruction of TOF PET data proposed by C.

Small animal imaging with multi-pinhole SPECT.

With Single Photon Emission Computed Tomography (SPECT), images of minute concentrations of tracer molecules can be acquired, allowing in vivo molecular imaging. For human imaging, the SPECT system has a modest spatial resolution of 5-15 mm, a large field of view and a high sensitivity. Using multi-pinhole SPECT, one can trade in field of view for resolution with preserved sensitivity, which enables the implementation of a small animal SPECT system with an improved resolution, currently ranging from 0.

Effect of overlapping projections on reconstruction image quality in multipinhole SPECT.

Multipinhole single photon emission computed tomography (SPECT) imaging has several advantages over single pinhole SPECT imaging, including an increased sensitivity and an improved sampling. However, the quest for a good design is challenging, due to the large number of design parameters. The effect of one of these, the amount of overlap in the projection images, on the reconstruction image quality, is examined in this paper.

Preliminary in vivo evaluation of a novel 99mTc-labeled HYNIC-cys-annexin A5 as an apoptosis imaging agent.

A novel cys-annexin A5 with a single cysteine-residue at its concave side has been developed by site-directed mutagenesis to allow conjugation through thiol-chemistry without affecting its apoptotic cell binding properties and was derivatized with HYNIC in a 1:1 stoichiometry. Similar to that of the 1st generation 99mTc-HYNIC-annexin A5, the novel 99mTc-HYNIC-cys-annexin A5 derivative shows in normal mice mainly renal and, to a lesser extent, hepatobiliary excretion. In murine models of hepatic apoptosis there was 257% increase in hepatic uptake of 99mTc-HYNIC-cys-annexin A5 as compared to normal mice.

Non-invasive detection and quantification of acute myocardial infarction in rabbits using mono-[123I]iodohypericin microSPECT.

Aims: Mono-[(123)I]iodohypericin ([(123)I]MIH) has been reported to have high avidity for necrosis. In the present study, by using rabbit models of acute myocardial infarction, we explored the suitability of [(123)I]MIH micro single photon emission computed tomography (microSPECT) for non-invasive visualization of myocardial infarcts in comparison with [(13)N]ammonia micro positron emission tomography (microPET) imaging, postmortem histomorphometry, and [(123)I]MIH autoradiography.

Methods And Results: Fourteen rabbits were divided into four groups.

Necrosis avidity of (99m)Tc(CO)3-labeled pamoic acid derivatives: synthesis and preliminary biological evaluation in animal models of necrosis.

In a search for an infarct avid tracer agent with improved properties, we have observed that bis-DTPA derivatives of pamoic acid have a high avidity for necrotic tissue. Here, we report the synthesis, radiolabeling, and preliminary evaluation in normal mice and rats with hepatic infarction of the (99m)Tc-tricarbonyl complexes of N, N'-bis(diethylenetriaminopentaacetato)-4,4'-methylene bis(2-hydroxy-3-naphthoic hydrazide) ( (99m)Tc(CO) 3-bis-DTPA-pamoate) and [ N-(5-aminopentyl)pyridin-2-yl-methylamino]methylacetato-4,4'-methylene-2-hydroxy-3-napthalenecarboxamide-(2'-hydroxy-3'-naphthoic acid methyl ester) ( (99m)Tc(CO) 3 -12). Radiolabeling with (99m)Tc(CO) 3 (+) was achieved with a radiochemical yield of over 95% for both tracer agents.

Synthesis and evaluation of a (99m)Tc-MAMA-propyl-thymidine complex as a potential probe for in vivo visualization of tumor cell proliferation with SPECT.

Introduction: Cytosolic thymidine kinase (TK1) catalyzes phosphorylation of thymidine to its monophosphate. TK1 activity is closely related with DNA synthesis, and thymidine analogs derivatized with bulky carboranylalkyl groups at the N-3 position were reported to be good substrates for TK1. Accordingly, we have synthesized (99m)Tc-MAMA-propyl-thymidine and evaluated it as a potential tumor tracer.