Methodological approaches to planar and volumetric scintigraphic imaging of small volume targets with high spatial resolution and sensitivity

Mejía, Jorge; Galvis-Alonso, Orfa Yineth; Braga, J.; Correa, R.A.; Leite, João Pereira; Simões, Marcus Vinı́cius

doi:10.1590/s0100-879x2009000800001

Cited by 8 publications

(6 citation statements)

References 30 publications

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“…Multiple pinhole collimators, consisting of around a dozen of pinholes, in combination with iterative decoding algorithms, are an alternative to solve the loss in sensitivity (e.g., [7]- [9]). As a limit case, coded mask collimators, consisting of several dozens of appropriately distributed pinholes, have also been proposed to obtain high quality images of small fields of view [10]- [14], even with the possibility of obtaining tomographic resolution with a single projection (see, e.g., [26]). With this type of collimators, the image decoding can be carried out by means of the classical correlation algorithm [27] or by using iterative decoding ones [14].…”

Section: Discussionmentioning

confidence: 99%

Planar and tomographic (SPECT) imaging of small volume targets using a Cross-Slit collimator

Mejía

Galvis-Alonso

Braga

et al. 2010

IEEE Nuclear Science Symposuim &Amp; Medical Imaging Conference

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In vivo imaging techniques applied to small animals are important tools in basic research. Scintigraphic planar and tomographic images allow in vivo functional expression of the protocol's effect on the animal's organs to be assessed. In that way, long term dynamical studies can be developed on the same animal, which can be used as its own control, helping to reduce statistical uncertainties, to cut costs and to improve ethical aspects of the experiment. Considering the small size of those animals' organs, specially adapted instruments must be used in order to reach, simultaneously, good spatial resolution and sensitivity. Because of the intrinsic magnification factor, smallsize pinhole-like collimators seem to be the obvious option to reach good spatial resolution. However, sensitivity is limited by the aperture's size. In this work, we propose the use of a combination of two 11-mm long, 0.8-mm width, mutually perpendicular slits as the collimator, in combination with appropriate restoration algorithms. By being narrow, information on high resolution is encoded on the recorded image, while, by being long, a large effective open area allows for good sensitivity. The slits are short enough such that individual open elements produce almost identical projections of the target. In a pre-processing stage, an implementation of the Maximum Likelihood Expectation Maximization algorithm was used to decode individual projections, producing high resolution planar images of the target. The same algorithm was used to combine those pre-processed individual projections, this time as if they would be obtained with a small size single pinhole collimator, obtaining a three-dimensional (3D) model of the target's radiotracer distribution. Monte Carlo simulations and physical phantoms were used to test the proposed methodology. Spatial resolution, equivalent to the one obtained with a 1.5-mm diameter pinhole collimator, was reached. Considering the collimator's open area, sensitivity should increase by a factor nearly 9, when compared with the same 1.5-mm diameter pinhole collimator. The experimental results are consistent with that theoretical value. Additionally, the pre-processing stage does not introduces a significant increase in the total processing time necessary for convergence to the reconstructed 3D object model. In this way, this kind of collimator appears as a good alternative ).to reduce the acquisition time, improving ethical aspects on animal management, as well as to allow the 3D target emission model to be obtained with no increased machine burden.

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Section: Discussionmentioning

confidence: 99%

Planar and tomographic (SPECT) imaging of small volume targets using a Cross-Slit collimator

Mejía

Galvis-Alonso

Braga

et al. 2010

IEEE Nuclear Science Symposuim &Amp; Medical Imaging Conference

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“…Our research group has recently described the implementation of a high-definition SPECT imaging system based on a pinhole collimator (with only one hole), a rotational support system for the small animal and appropriate software tools adapted to a gamma chamber for clinical use 6,7 . The objective of the present study was to validate this system for quantification in vivo of the myocardial fibrosis area in an experimental model of myocardial infarct in rats that uses as gold standard the in vitro histopathologic infarct measurement.…”

Section: Introductionmentioning

confidence: 99%

Myocardial Infarction Area Quantification using High-Resolution SPECT Images in Rats

Oliveira¹,

Mejía²,

Carvalho³

et al. 2013

Arquivos Brasileiros De Cardiologia

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BackgroundImaging techniques enable in vivo sequential assessment of the morphology and function of animal organs in experimental models. We developed a device for high-resolution single photon emission computed tomography (SPECT) imaging based on an adapted pinhole collimator. ObjectiveTo determine the accuracy of this system for quantification of myocardial infarct area in rats. MethodsThirteen male Wistar rats (250 g) underwent experimental myocardial infarction by occlusion of the left coronary artery. After 4 weeks, SPECT images were acquired 1.5 hours after intravenous injection of 555 MBq of 99mTc-Sestamibi. The tomographic reconstruction was performed by using specially developed software based on the Maximum Likelihood algorithm. The analysis of the data included the correlation between the area of perfusion defects detected by scintigraphy and extent of myocardial fibrosis assessed by histology. ResultsThe images showed a high target organ/background ratio with adequate visualization of the left ventricular walls and cavity. All animals presenting infarction areas were correctly identified by the perfusion images. There was no difference of the infarct area as measured by SPECT (21.1 ± 21.2%) and by histology (21.7 ± 22.0%; p=0.45). There was a strong correlation between individual values of the area of infarction measured by these two methods. ConclusionThe developed system presented adequate spatial resolution and high accuracy for the detection and quantification of myocardial infarction areas, consisting in a low cost and versatile option for high-resolution SPECT imaging of small rodents.

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“…Much effort has been made to optimize SPECT parameters that affect image acquisition as well as quantitative analysis of the target tissues in small animals (7)(8)(9)(10)(11). However, different target tissues represent different optimization challenges.…”

Section: Introductionmentioning

confidence: 99%

Micro–Single-Photon Emission Computed Tomography Image Acquisition and Quantification of Sodium-Iodide Symporter–Mediated Radionuclide Accumulation in Mouse Thyroid and Salivary Glands

Brandt

Kloos

Shen

et al. 2012

Thyroid

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Methodological approaches to planar and volumetric scintigraphic imaging of small volume targets with high spatial resolution and sensitivity

Cited by 8 publications

References 30 publications

Planar and tomographic (SPECT) imaging of small volume targets using a Cross-Slit collimator

Planar and tomographic (SPECT) imaging of small volume targets using a Cross-Slit collimator

Myocardial Infarction Area Quantification using High-Resolution SPECT Images in Rats

Micro–Single-Photon Emission Computed Tomography Image Acquisition and Quantification of Sodium-Iodide Symporter–Mediated Radionuclide Accumulation in Mouse Thyroid and Salivary Glands

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