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Purpose: Tour objective is to design a novel SPECT system for molecular breast imaging (MBI) and evaluate its performance. The limited angle SPECT system, or emission tomosynthesis, is designed to achieve 3D images of the breast with high spatial resolution/sensitivity. The system uses a simplified detector motion and is conducive to on-board biopsy and mult-modal imaging with mammography. Methods: The novel feature of the proposed gamma camera is a variable-angle, slant-hole (VASH) collimator, which is well suited for limited angle SPECT of a mildly compressed breast. The collimator holes change slant angle while the camera surface remains flush against the compression paddle. This allows the camera to vary the angular view ({+-}30{degrees}, {+-}45{degrees}) for tomographic imaging while keeping the camera close to the object for high spatial resolution and/or sensitivity. Theoretical analysis and Monte Carlo simulations were performed assuming a point source and isolated breast phantom. Spatial resolution, sensitivity, contrast and SNR were measured. Results were compared to single-view, planar images and conventional SPECT. For both conventional SPECT and VASH, data were reconstructed using iterative algorithms. Finally, a proof-of-concept VASH collimator was constructed for experimental evaluation. Results: Measured spatial resolution/sensitivity with VASH showed good agreement with theory including depth-of-interaction (DOI)more » effects. The DOI effect diminished the depth resolution by approximately 2 mm. Increasing the slant angle range from {+-}30{degrees} to {+-}45{degrees} resulted in an approximately 1 mm improvement in the depth resolution. In the breast phantom images, VASH showed improved contrast and SNR over conventional SPECT and improved contrast over planar scintimmammography. Reconstructed images from the proof-of-concept VASH collimator demonstrated reasonable depth resolution capabilities using limited angle projection data. Conclusion: We conclude that this limited angle SPECT approach using a VASH collimator can achieve superior 3D image quality for MBI in a design that has attractive characteristics for clinical imaging.« less |
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