Resolution recovery in pinhole SPECT based on multi-ray projections: a phantom study

PurposeLow sensitivity can become a major problem when very small pinholes are used in SPECT imaging. Although a larger pinhole aperture will improve the sensitivity, this will be at the cost of the spatial resolution. With a view to improving the resolution–sensitivity trade-off, this paper explores an iterative reconstruction algorithm that models the pinhole aperture based on multi-ray projections.MethodsThis new implementation was validated using simulated data and phantom experiments. Two approaches were investigated. Firstly, the pinhole aperture was modelled in both the forward and the back projector. Secondly, the dual matrix implementation was investigated by modelling the pinhole aperture only in the forward projector. The systematic error, the full-width at half-maximum (FWHM) and the statistical error were quantified using the simulated data. Experimental phantom data were acquired for visual comparison with the reconstructions obtained from the simulated data.ResultsFor a predefined number of iterations, the systematic error, the FWHM and the statistical error could be decreased when the pinhole aperture was modelled during iterative reconstruction. For a fixed, predefined statistical error of ±10%, smaller systematic errors and smaller FWHM were obtained when modelling the pinhole opening. When the dual matrix implementation was used, equivalent results could be obtained as when modelling the pinhole opening in both the forward and the back projector.ConclusionThe multi-ray method to accomplish resolution recovery during the reconstruction of pinhole SPECT projection images offers a better trade-off between spatial resolution and noise compared with a reconstruction which does not model the pinhole aperture.

[1]  Bruce H. Hasegawa,et al.  Quantitative SPECT reconstruction using multiray projection integrators , 1995, 1995 IEEE Nuclear Science Symposium and Medical Imaging Conference Record.

[2]  Irene A. Stegun,et al.  Handbook of Mathematical Functions. , 1966 .

[3]  N. Schramm,et al.  High-resolution SPECT using multi-pinhole collimation , 2002, IEEE Nuclear Science Symposium Conference Record.

[4]  Y. Yonekura,et al.  Ultra-high resolution SPECT system using four pinhole collimators for small animal studies. , 1995, Journal of nuclear medicine : official publication, Society of Nuclear Medicine.

[5]  Max A. Viergever,et al.  Dual matrix ordered subsets reconstruction for accelerated 3D scatter compensation in single-photon emission tomography , 1997, European Journal of Nuclear Medicine.

[6]  Patrick Dupont,et al.  Characterization of pinhole SPECT acquisition geometry , 2003, IEEE Transactions on Medical Imaging.

[7]  F. Beekman,et al.  Design and simulation of a high-resolution stationary SPECT system for small animals. , 2004, Physics in medicine and biology.

[8]  Paul Suetens,et al.  Optimization of geometrical calibration in pinhole SPECT , 2005, IEEE Transactions on Medical Imaging.

[9]  B.M.W. Tsui,et al.  Three-dimensional Iterative Reconstruction Algorithms With Attenuation And Geometric Point Response Correction , 1990, 1990 IEEE Nuclear Science Symposium Conference Record.

[10]  J. Booij,et al.  Evaluation of high-resolution pinhole SPECT using a small rotating animal. , 2001, Journal of nuclear medicine : official publication, Society of Nuclear Medicine.

[11]  D. Weber,et al.  Pinhole SPECT: ultra-high resolution imaging for small animal studies. , 1995, Journal of nuclear medicine : official publication, Society of Nuclear Medicine.

[12]  Tomio Inoue,et al.  Myocardial infarction in rats: high-resolution single-photon emission tomographic imaging with a pinhole collimator , 1996, European Journal of Nuclear Medicine.

[13]  Michel Defrise,et al.  Interest of the ordered subsets expectation maximization (OS-EM) algorithm in pinhole single-photon emission tomography reconstruction: a phantom study , 2000, European Journal of Nuclear Medicine.

[14]  P. V. van Rijk,et al.  U-SPECT-I: a novel system for submillimeter-resolution tomography with radiolabeled molecules in mice. , 2005, Journal of nuclear medicine : official publication, Society of Nuclear Medicine.

[15]  Grant T. Gullberg,et al.  Slab-by-slab blurring model for geometric point response correction and attenuation correction using iterative reconstruction algorithms , 1997, 1997 IEEE Nuclear Science Symposium Conference Record.

[16]  D. Weber,et al.  Ultra-high-resolution imaging of small animals: Implications for preclinical and research studies , 1999, Journal of nuclear cardiology : official publication of the American Society of Nuclear Cardiology.

[17]  S. Meikle,et al.  Small animal SPECT and its place in the matrix of molecular imaging technologies , 2005, Physics in medicine and biology.

[18]  Stefan Eberl,et al.  A prototype coded aperture detector for small animal SPECT , 2001 .

[19]  H. Atkins,et al.  Pinhole SPECT: an approach to in vivo high resolution SPECT imaging in small laboratory animals. , 1994, Journal of nuclear medicine : official publication, Society of Nuclear Medicine.

[20]  Hiroyuki Kudo,et al.  A new reconstruction strategy for image improvement in pinhole SPECT , 2004, European Journal of Nuclear Medicine and Molecular Imaging.

[21]  R. Jaszczak,et al.  Pinhole collimation for ultra-high-resolution, small-field-of-view SPECT. , 1994, Physics in medicine and biology.

[22]  G. Gullberg,et al.  A rotating and warping projector/backprojector for fan-beam and cone-beam iterative algorithm , 1994 .