Pinhole collimation for ultra-high-resolution, small-field-of-view SPECT

Abstract

The objective of this investigation was to evaluate small-field-of-view, ultra-high-resolution pinhole collimation for a rotating-camera SPECT system that could be used to image small laboratory animals. Pinhole collimation offers distinct advantages over conventional parallel-hole collimation when used to image small objects. Since geometric sensitivity increases markedly for points close to the pinhole, small-diameter and high-magnification pinhole geometries may be useful for selected imaging tasks when used with large-field-of-view scintillation cameras. The use of large magnifications can minimize the loss of system resolution caused by the intrinsic resolution of the scintillation camera. A pinhole collimator has been designed and built that can be mounted on one of the scintillation cameras of a triple-head SPECT system. Three pinhole inserts with approximate aperture diameters of 0.6, 1.2 and 2.0 mm have been built and can be mounted individually on the collimator housing. When a ramp filter is used with a three-dimensional (3D) filtered backprojection (FBP) algorithm, the three apertures have in-plane SPECT spatial resolutions (FWHM) at 4 cm of 1.5, 1.9 and 2.8 mm, respectively. In-air point source sensitivities at 4 cm from the apertures are 0.9, 2.6 and 5.7 counts s(-1) microCi(-1) (24, 70 and 154 counts s(-1) MBq(-1)) for the 0.6, 1.2 and 2.0 mm apertures, respectively. In vitro image quality was evaluated with a micro-cold-rod phantom and a micro-Defrise phantom using both the 3D FBP algorithm and a 3D maximum likelihood-expectation maximization (ML-EM) algorithm. In vivo image quality was evaluated using two (315 and 325 g) rats. Ultra-high-resolution pinhole SPECT is an inexpensive and simple approach for imaging small animals that can be used with existing rotating-camera SPECT system.

Tomographie sténopéïque au 99mTc-MIBI dans l’hyperparathyroïdie primaire

“…Plus récemment, des études cliniques préliminaires ont montré des résultats encourageants dans la pathologie parathyroïdienne. Profanter et al ont comparé la S- [38], a comme principal inconvénient des artéfacts en étoile et des distorsions, d'autant plus marqués que l'on s'éloigne du plan central [39][40]. La reconstruction itérative, notamment avec les algorithmes ML-EM et OS-EM, se montre supérieure aux méthodes analytiques pour la reconstruction des plans éloignés du plan de l'orbite.…”

Dual-Modality Imaging: More Than the Sum of its Components

“…111,112,[118][119][120] These include microCT systems 118,[121][122][123] that incorporate a low power X-ray tube and a phosphor-coupled CCD camera or similar two-dimensional x-ray imaging detector to achieve spatial resolutions as high as 25 microns or better. Similarly, high-resolution images can be obtained using microPET scanners 111,119 having high-resolution detectors operated in coincidence to obtain spatial resolutions in the range of 1 to 2 mm, whereas SPECT imaging of mice [124][125][126][127][128][129] can be performed using pinhole collimation to obtain spatial resolutions better than 1 millimetre. In general, these imaging systems provide characteristics similar to those used for clinical imaging of humans.…”

Development of Dynamic Three-Dimensional Multi-Pinhole Gamma Camera

“…This spatial resolution is comparable to that of the conventional small animal SPECT system equipped with single-pinhole collimators that would provide a spatial resolution of about 3 mm full-width at half-maximum (FWHM). 1,7) The result from the pinhole with an opening angle of 40…”

“…1. In addition, the 57 Co source was placed in two different locations, (1) in the center of the FOV and, (2) at a distance of 12.5 mm from the center in the x-direction. The distance from the 57 Co source to the IP was 100 mm for both of these cases.…”

“…Therefore, SPECT systems with a pinhole collimator have been proposed and have demonstrated good spatial resolution. 1) Pinhole SPECT systems, however, have poor sensitivity for dynamic imaging, that is, real-time imaging with temporal information, of radio pharmaceuticals distributed within the body. In order to improve the sensitivity while maintaining high spatial resolution, SPECT systems employing multi-pinhole collimators have been proposed for small animal imaging.…”