### Abstract

Objective: This study examined the effects on SPECT quantitation caused by erroneous size and position of the attenuation map and inaccurate pixel size used in the Chang algorithm. Methods: Projection data of a three-dimensional head phantom were simulated with a uniform attenuation coefficient of 0.15/cm for the inside of the phantom. Images were reconstructed using the filtered backprojection algorithm without attenuation compensation and the Chang algorithm with different attenuation maps. Quantitative comparison then was performed between the reconstructed images and the phantom. Results: The pixel values obtained for noisy data by using the first-order Chang algorithm with an accurate attenuation map were less than 10% different from the true values and the left-right asymmetry was under 5%. Small errors in the geometric parameters of the attenuation map, however, caused considerable quantitative inaccuracy in the reconstructed image. For example, a 0.64-cm error in the size of the map caused 10% deviation from the true value and a 0.64-cm shift of the position of the map towards the left produced 10% left-right pixel value asymmetry. Conclusion: The accuracy of the Chang algorithm critically depends on the geometric parameters. For a uniform attenuator with symmetric geometry, such as the human brain, a true left-right symmetry in the pixel value can be altered significantly by a small error in the geometric parameters, while symmetry can be maintained with no attenuation compensation.

Original language | English (US) |
---|---|

Pages (from-to) | 178-185 |

Number of pages | 8 |

Journal | Journal of Nuclear Medicine Technology |

Volume | 26 |

Issue number | 3 |

State | Published - Sep 1 1998 |

### Fingerprint

### Keywords

- Attenuation compensation
- Image reconstruction
- SPECT

### ASJC Scopus subject areas

- Radiological and Ultrasound Technology
- Radiology Nuclear Medicine and imaging

### Cite this

*Journal of Nuclear Medicine Technology*,

*26*(3), 178-185.

**Effects of the attenuation map used in the Chang algorithm on quantitative SPECT results.** / Cao, Zong Jian; Holder, Lawrence E.

Research output: Contribution to journal › Article

*Journal of Nuclear Medicine Technology*, vol. 26, no. 3, pp. 178-185.

}

TY - JOUR

T1 - Effects of the attenuation map used in the Chang algorithm on quantitative SPECT results

AU - Cao, Zong Jian

AU - Holder, Lawrence E.

PY - 1998/9/1

Y1 - 1998/9/1

N2 - Objective: This study examined the effects on SPECT quantitation caused by erroneous size and position of the attenuation map and inaccurate pixel size used in the Chang algorithm. Methods: Projection data of a three-dimensional head phantom were simulated with a uniform attenuation coefficient of 0.15/cm for the inside of the phantom. Images were reconstructed using the filtered backprojection algorithm without attenuation compensation and the Chang algorithm with different attenuation maps. Quantitative comparison then was performed between the reconstructed images and the phantom. Results: The pixel values obtained for noisy data by using the first-order Chang algorithm with an accurate attenuation map were less than 10% different from the true values and the left-right asymmetry was under 5%. Small errors in the geometric parameters of the attenuation map, however, caused considerable quantitative inaccuracy in the reconstructed image. For example, a 0.64-cm error in the size of the map caused 10% deviation from the true value and a 0.64-cm shift of the position of the map towards the left produced 10% left-right pixel value asymmetry. Conclusion: The accuracy of the Chang algorithm critically depends on the geometric parameters. For a uniform attenuator with symmetric geometry, such as the human brain, a true left-right symmetry in the pixel value can be altered significantly by a small error in the geometric parameters, while symmetry can be maintained with no attenuation compensation.

AB - Objective: This study examined the effects on SPECT quantitation caused by erroneous size and position of the attenuation map and inaccurate pixel size used in the Chang algorithm. Methods: Projection data of a three-dimensional head phantom were simulated with a uniform attenuation coefficient of 0.15/cm for the inside of the phantom. Images were reconstructed using the filtered backprojection algorithm without attenuation compensation and the Chang algorithm with different attenuation maps. Quantitative comparison then was performed between the reconstructed images and the phantom. Results: The pixel values obtained for noisy data by using the first-order Chang algorithm with an accurate attenuation map were less than 10% different from the true values and the left-right asymmetry was under 5%. Small errors in the geometric parameters of the attenuation map, however, caused considerable quantitative inaccuracy in the reconstructed image. For example, a 0.64-cm error in the size of the map caused 10% deviation from the true value and a 0.64-cm shift of the position of the map towards the left produced 10% left-right pixel value asymmetry. Conclusion: The accuracy of the Chang algorithm critically depends on the geometric parameters. For a uniform attenuator with symmetric geometry, such as the human brain, a true left-right symmetry in the pixel value can be altered significantly by a small error in the geometric parameters, while symmetry can be maintained with no attenuation compensation.

KW - Attenuation compensation

KW - Image reconstruction

KW - SPECT

UR - http://www.scopus.com/inward/record.url?scp=0031686956&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0031686956&partnerID=8YFLogxK

M3 - Article

C2 - 9755437

AN - SCOPUS:0031686956

VL - 26

SP - 178

EP - 185

JO - Journal of Nuclear Medicine Technology

JF - Journal of Nuclear Medicine Technology

SN - 0091-4916

IS - 3

ER -