Abstract
Conventional single photon emission computed tomography (SPECT) relies on mechanical collimation whose resolution and sensitivity are interdependent, the best performance a SPECT system can attain is only a compromise of these two equally desired properties. To simultaneously achieve high resolution and sensitivity, we propose to use sensitive detectors constructed in a multi-layer in ter spaced mosaicdetectors (MATRICES) architecture to accomplish part of the collimation needed. We name this new approach self-collimation. We evaluate three self-collimating SPECT systems and report their imaging performance: 1) A simulated human brain SPECT achieves 3.88% sensitivity, it clearly resolves 0.5-mm and 1.0-mm hot-rod patterns at noise-free and realistic count-levels, respectively; 2) a simulated mouse SPECT achieves 1.25% sensitivity, it clearly resolves 50- [Formula: see text] and 100- [Formula: see text] hot-rod patterns at noise-free and realistic count-levels, respectively; 3) a SPECT prototype achieves 0.14% sensitivity and clearly separates 0.3-mm-diameter point sources of which the center-to-center neighbor distance is also 0.3 mm. Simulated contrast phantom studies show excellent resolution and signal-to-noise performance. The unprecedented system performance demonstrated by these 3 SPECT scanners is a clear manifestation of the superiority of the self-collimating approach over conventional mechanical collimation. It represents a potential paradigm shift in SPECT technology development.
Highlights
S INGLE photon emission computed tomography (SPECT) is a well-established in vivo molecular imaging technology that is capable of detecting biological signals at sub-nanomolar level [1], [2]
2) Simulated Mouse SPECT: For the mouse SPECT, the sensitivity values range from 0.90% to 2.78% and has an average of 1.25% over the FOV, as shown in the bottom-row of Fig. 8
Compared to the brain SPECT system, the lower sensitivity and more prominent changes over the trans-axial and axial range here are due to the mouse SPECT’s detector geometry — its FOV is more elongated in the axial direction and there are more photons incident towards the MATRICES in oblique angles which may be more likely absorbed by the metal plate
Summary
S INGLE photon emission computed tomography (SPECT) is a well-established in vivo molecular imaging technology that is capable of detecting biological signals at sub-nanomolar level [1], [2]. Mechanical collimation yields an inherent inverse interdependency between a SPECT system’s resolution and sensitivity. Constructed with a heavy metal such as lead or tungsten, a mechanical collimator confines the photon sensitive region through physical apertures that only allow photons within a selective angular range to pass through and absorb the rest. The sizes of the apertures determine both the selectiveness of the region, i.e. resolution, as well as the acceptance quantity from the region, i.e. sensitivity. A boost of resolution means a more constrained angular range leading to a loss of sensitivity, and vice versa. This inverse interdependency defines the overall poor performance of the conventional SPECT systems
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