Axial Resolution of Helical-Orbit Pinhole SPECT With Synchronized and Unsynchronized Motion

Ayan, A.S.; Metzler, S.

doi:10.1109/tns.2007.910881

Cited by 3 publications

(4 citation statements)

References 11 publications

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“…Numerical methods can be used to evaluate the maximum pitch that gives complete sampling in the case of multiple collimators (40). The choice of the number of steps yields a tradeoff between axial resolution and live time (i.e., the amount of time acquiring data rather than rotating the system) (31). We have generally found 120–180 steps to be a good overall choice for balancing live-time with the requirements for good axial and transaxial resolution.…”

Section: Discussionmentioning

confidence: 99%

“…Pinhole collimation has high sensitivity and high resolution when the object may be brought near the aperture, or when there is a small radius of rotation (ROR) of the pinhole aperture (1,2), which is afixed to the gamma camera, about the axis of rotation (AOR), which is typically centered on the object. These characteristics have made pinhole SPECT a subject of active research for small-animal imaging (1,3–33), including helical pinhole SPECT (15,20,21,26,27,31–33). For tomographic image reconstruction, the inversion of the set of 2D projection images into a 3D distribution requires that the Kirillov-Tuy (34,35) condition be met.…”

Section: Introductionmentioning

confidence: 99%

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Feasibility of Whole-Body Functional Mouse Imaging Using Helical Pinhole SPECT

et al. 2009

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Purpose-Detailed in vivo whole-body biodistributions of radiolabeled tracers may characterize the longitudinal progression of disease, and changes with therapeutic interventions. Small-animal imaging in mice is particularly attractive due to the wide array of well characterized genetically and surgically created models of disease. Single Photon Emission Computed Tomography (SPECT) imaging using pinhole collimation provides high resolution and sensitivity, but conventional methods using circular acquisitions result in severe image truncation and incomplete sampling of data which prevent the accurate determination of whole-body radiotracer biodistributions. This study describes the feasibility of helical acquisition paths to mitigate these effects.Procedures-Helical paths of pinhole apertures were implemented using an external robotic stage aligned with the axis of rotation (AOR) of the scanner. Phantom and mouse scans were performed using helical paths and either circular or bi-circular orbits at the same radius of rotation (ROR). The bi-circular orbits consisted of two 360-degree scans separated by an axial shift to increase the axial field of view (FOV) and to improve the complete-sampling properties.Results-Reconstructions of phantoms and mice acquired with helical paths show good image quality and are visually free of both truncation and axial-blurring artifacts. Circular orbits yielded reconstructions with both artifacts and a limited effective FOV. The bi-circular scans enlarged the axial FOV, but still suffered from truncation and sampling artifacts.Conclusions-Helical paths can provide complete sampling data and large effective FOV, yielding 3D full-body in vivo biodistributions while still maintaining a small distance from the aperture to the object for good sensitivity and resolution.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Feasibility of Whole-Body Functional Mouse Imaging Using Helical Pinhole SPECT

et al. 2009

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“…A similar situation of device synchronization with a step-andshoot SPECT scan is addressed by Ayan and Metzler [8] for the purpose of helical data sampling by stepping the animal bed in tandem with the rotating gamma camera detectors. To achieve this goal, a pair of analog tilt sensors is attached to the gantry of the SPECT scanner.…”

Section: Introductionmentioning

confidence: 98%

Wireless Synchronization of a Multi-Pinhole Small Animal SPECT Collimation Device With a Clinical Scanner

DiFilippo

Patel

2009

IEEE Trans. Nucl. Sci.

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A multi-pinhole collimation device for small animal single photon emission computed tomography (SPECT) uses the gamma camera detectors of a standard clinical SPECT scanner. The collimator and animal bed move independently of the detectors, and therefore their motions must be synchronized. One approach is manual triggering of the SPECT acquisition simultaneously with a programmed motion sequence for the device. However, some data blurring and loss of image quality result, and true electronic synchronization is preferred. An off-the-shelf digital gyroscope with integrated Bluetooth interface provides a wireless solution to device synchronization. The sensor attaches to the SPECT gantry and reports its rotational speed to a notebook computer controlling the device. Software processes the rotation data in realtime, averaging the signal and issuing triggers while compensating for baseline drift. Motion commands are sent to the collimation device with minimal delay, within approximately 0.5 second of the start of SPECT gantry rotation. Test scans of a point source demonstrate an increase in true counts and a reduction in background counts compared to manual synchronization. The wireless rotation sensor provides robust synchronization of the collimation device with the clinical SPECT scanner and enhances image quality.

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“…If the objective is to obtain a planar image of the target, this difference precludes attaining an appropriate projection of the object's signal distribution, if compared with records obtained with single pinhole or parallel collimators. When making 3D reconstructions from single pinhole planar projections, the axial field of view is limited by the pinhole cone acceptance and artifacts are usually introduced in the reconstruction phase (see, e.g., [18]- [20]). If appropriately distributed multiple pinholes are used, projections from individual pinholes can be considered as independent projections of the target.…”

Section: Introductionmentioning

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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Axial Resolution of Helical-Orbit Pinhole SPECT With Synchronized and Unsynchronized Motion

Cited by 3 publications

References 11 publications

Feasibility of Whole-Body Functional Mouse Imaging Using Helical Pinhole SPECT

Feasibility of Whole-Body Functional Mouse Imaging Using Helical Pinhole SPECT

Wireless Synchronization of a Multi-Pinhole Small Animal SPECT Collimation Device With a Clinical Scanner

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

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