### Abstract

The qualitative and quantitative accuracy of SPECT images is degraded by physical factors of attenuation, Compton scatter and spatially varying collimator geometric response.

This paper presents a 3D ray-tracing technique for modelling attenuation, scatter and geometric response for SPECT imaging in an inhomogeneous attenuating medium. The model is incorporated into a three-dimensional projector-backprojector and used with the maximum-likelihood expectation-maximization algorithm for reconstruction of parallel-beam data. A transmission map is used to define the inhomogeneous attenuating and scattering object being imaged. The attenuation map defines the probability of photon attenuation between the source and the scattering site, the scattering angle at the scattering site and the probability of attenuation of the scattered photon between the scattering site and the detector. The probability of a photon being scattered through a given angle and being detected in the emission energy window is approximated using a Gaussian function. The parameters of this Gaussian function are determined using physical measurements of parallel-beam scatter line spread functions from a non-uniformly attenuating phantom. The 3D ray-tracing scatter projector-backprojector produces the scatter and primary components. Then, a 3D ray-tracing projector-backprojector is used to model the geometric response of the collimator.

From Monte Carlo and physical phantom experiments, it is shown that the best results are obtained by simultaneously correcting attenuation, scatter and geometric response, compared with results obtained with only one or two of the three corrections. It is also shown that a 3D scatter model is more accurate than a 2D model.

A transmission map is useful for obtaining measurements of attenuation and scatter in SPECT data, which can be used together with a model of the geometric response of the collimator to obtain corrected images with quantitative and diagnostically accurate information.

Original language | English |
---|---|

Pages (from-to) | 3459-3480 |

Number of pages | 22 |

Journal | Physics in Medicine and Biology |

Volume | 45 |

Publication status | Published - 2000 |

### Keywords

- ENERGY-WEIGHTED ACQUISITION
- ITERATIVE RECONSTRUCTION ALGORITHMS
- EMISSION COMPUTED-TOMOGRAPHY
- INVERSE MONTE-CARLO
- COMPTON-SCATTERING
- DETECTOR RESPONSE
- PROJECTOR-BACKPROJECTOR
- IMAGE-RECONSTRUCTION
- SPATIAL-DISTRIBUTION
- MAXIMUM-LIKELIHOOD

### Cite this

*Physics in Medicine and Biology*,

*45*, 3459-3480.

**A three-dimensional ray-driven attenuation, scatter and geometric response correction technique for SPECT in inhomogeneous media.** / Laurette, I ; Zeng, G L ; Welch, A ; Christian, P E ; Gullberg, G T .

Research output: Contribution to journal › Article

*Physics in Medicine and Biology*, vol. 45, pp. 3459-3480.

}

TY - JOUR

T1 - A three-dimensional ray-driven attenuation, scatter and geometric response correction technique for SPECT in inhomogeneous media

AU - Laurette, I

AU - Zeng, G L

AU - Welch, A

AU - Christian, P E

AU - Gullberg, G T

PY - 2000

Y1 - 2000

N2 - The qualitative and quantitative accuracy of SPECT images is degraded by physical factors of attenuation, Compton scatter and spatially varying collimator geometric response.This paper presents a 3D ray-tracing technique for modelling attenuation, scatter and geometric response for SPECT imaging in an inhomogeneous attenuating medium. The model is incorporated into a three-dimensional projector-backprojector and used with the maximum-likelihood expectation-maximization algorithm for reconstruction of parallel-beam data. A transmission map is used to define the inhomogeneous attenuating and scattering object being imaged. The attenuation map defines the probability of photon attenuation between the source and the scattering site, the scattering angle at the scattering site and the probability of attenuation of the scattered photon between the scattering site and the detector. The probability of a photon being scattered through a given angle and being detected in the emission energy window is approximated using a Gaussian function. The parameters of this Gaussian function are determined using physical measurements of parallel-beam scatter line spread functions from a non-uniformly attenuating phantom. The 3D ray-tracing scatter projector-backprojector produces the scatter and primary components. Then, a 3D ray-tracing projector-backprojector is used to model the geometric response of the collimator.From Monte Carlo and physical phantom experiments, it is shown that the best results are obtained by simultaneously correcting attenuation, scatter and geometric response, compared with results obtained with only one or two of the three corrections. It is also shown that a 3D scatter model is more accurate than a 2D model.A transmission map is useful for obtaining measurements of attenuation and scatter in SPECT data, which can be used together with a model of the geometric response of the collimator to obtain corrected images with quantitative and diagnostically accurate information.

AB - The qualitative and quantitative accuracy of SPECT images is degraded by physical factors of attenuation, Compton scatter and spatially varying collimator geometric response.This paper presents a 3D ray-tracing technique for modelling attenuation, scatter and geometric response for SPECT imaging in an inhomogeneous attenuating medium. The model is incorporated into a three-dimensional projector-backprojector and used with the maximum-likelihood expectation-maximization algorithm for reconstruction of parallel-beam data. A transmission map is used to define the inhomogeneous attenuating and scattering object being imaged. The attenuation map defines the probability of photon attenuation between the source and the scattering site, the scattering angle at the scattering site and the probability of attenuation of the scattered photon between the scattering site and the detector. The probability of a photon being scattered through a given angle and being detected in the emission energy window is approximated using a Gaussian function. The parameters of this Gaussian function are determined using physical measurements of parallel-beam scatter line spread functions from a non-uniformly attenuating phantom. The 3D ray-tracing scatter projector-backprojector produces the scatter and primary components. Then, a 3D ray-tracing projector-backprojector is used to model the geometric response of the collimator.From Monte Carlo and physical phantom experiments, it is shown that the best results are obtained by simultaneously correcting attenuation, scatter and geometric response, compared with results obtained with only one or two of the three corrections. It is also shown that a 3D scatter model is more accurate than a 2D model.A transmission map is useful for obtaining measurements of attenuation and scatter in SPECT data, which can be used together with a model of the geometric response of the collimator to obtain corrected images with quantitative and diagnostically accurate information.

KW - ENERGY-WEIGHTED ACQUISITION

KW - ITERATIVE RECONSTRUCTION ALGORITHMS

KW - EMISSION COMPUTED-TOMOGRAPHY

KW - INVERSE MONTE-CARLO

KW - COMPTON-SCATTERING

KW - DETECTOR RESPONSE

KW - PROJECTOR-BACKPROJECTOR

KW - IMAGE-RECONSTRUCTION

KW - SPATIAL-DISTRIBUTION

KW - MAXIMUM-LIKELIHOOD

M3 - Article

VL - 45

SP - 3459

EP - 3480

JO - Physics in Medicine and Biology

JF - Physics in Medicine and Biology

SN - 0031-9155

ER -