The effect of attenuation map, scatter energy window width, and volume of interest on the calibration factor calculation in quantitative 177Lu SPECT imaging: Simulation and phantom study

Elham Karimi Ghodoosi, Calogero D'Alessandria, Ye Li, Alexandra Bartel, Markus Köhner, Vera Höllriegl, Nassir Navab, Matthias Eiber, Wei Bo Li, Eric Frey, Sibylle Ziegler

Research output: Contribution to journalArticle

Abstract

Purpose: The objective of this study was to evaluate the image degrading factors in quantitative 177Lu SPECT imaging when using both main gamma photopeak energies. Methods: Phantom measurements with two different vials containing various calibrated activities in air or water were performed to derive a mean calibration factor (CF) for large and small volumes of interest (VOIs). In addition, Monte Carlo simulations were utilized to investigate the effect of scatter energy window width, scatter correction method, such as effective scatter source estimation (ESSE) and triple energy window (TEW), and attenuation map on the quantification of 177Lu. Results: The measured mean CF using large and small VOIs in water was 4.50 ± 0.80 and 4.80 ± 0.72 cps MBq−1, respectively. Simulations showed a reference CF of 3.3 cps MBq−1 for the water-filled phantom considering all photons excluding scattered events. By using the attenuation map generated for 190 keV photons, the calculated CFs for 113 keV and 208 keV are 10% lower than by using the weighted mean energy of 175 keV for 177Lu. The calculated CF using the TEW correction was 17% higher than using the ESSE method for a water-filled phantom. However, our findings showed that an appropriate scatter window combination can reduce this difference between TEW and ESSE methods. Conclusions: The present work implies that choosing a suitable width of scatter energy windows can reduce uncertainties in radioactivity quantification. It is suggested to generate the attenuation map at 113 keV and 208 keV, separately. Furthermore, using small VOIs is suggested in CF calculation.

Original languageEnglish (US)
Pages (from-to)74-80
Number of pages7
JournalPhysica Medica
Volume56
DOIs
StatePublished - Dec 1 2018

Fingerprint

Imaging Phantoms
Single-Photon Emission-Computed Tomography
Calibration
attenuation
Water
Photons
simulation
energy
water
photopeak
Radioactivity
Uncertainty
photons
Air
radioactivity
air

Keywords

  • Lu
  • Attenuation map
  • Calibration factor
  • Scatter fraction
  • Scatter window
  • SPECT/CT

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging
  • Physics and Astronomy(all)

Cite this

The effect of attenuation map, scatter energy window width, and volume of interest on the calibration factor calculation in quantitative 177Lu SPECT imaging : Simulation and phantom study. / Karimi Ghodoosi, Elham; D'Alessandria, Calogero; Li, Ye; Bartel, Alexandra; Köhner, Markus; Höllriegl, Vera; Navab, Nassir; Eiber, Matthias; Li, Wei Bo; Frey, Eric; Ziegler, Sibylle.

In: Physica Medica, Vol. 56, 01.12.2018, p. 74-80.

Research output: Contribution to journalArticle

Karimi Ghodoosi, Elham ; D'Alessandria, Calogero ; Li, Ye ; Bartel, Alexandra ; Köhner, Markus ; Höllriegl, Vera ; Navab, Nassir ; Eiber, Matthias ; Li, Wei Bo ; Frey, Eric ; Ziegler, Sibylle. / The effect of attenuation map, scatter energy window width, and volume of interest on the calibration factor calculation in quantitative 177Lu SPECT imaging : Simulation and phantom study. In: Physica Medica. 2018 ; Vol. 56. pp. 74-80.
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abstract = "Purpose: The objective of this study was to evaluate the image degrading factors in quantitative 177Lu SPECT imaging when using both main gamma photopeak energies. Methods: Phantom measurements with two different vials containing various calibrated activities in air or water were performed to derive a mean calibration factor (CF) for large and small volumes of interest (VOIs). In addition, Monte Carlo simulations were utilized to investigate the effect of scatter energy window width, scatter correction method, such as effective scatter source estimation (ESSE) and triple energy window (TEW), and attenuation map on the quantification of 177Lu. Results: The measured mean CF using large and small VOIs in water was 4.50 ± 0.80 and 4.80 ± 0.72 cps MBq−1, respectively. Simulations showed a reference CF of 3.3 cps MBq−1 for the water-filled phantom considering all photons excluding scattered events. By using the attenuation map generated for 190 keV photons, the calculated CFs for 113 keV and 208 keV are 10{\%} lower than by using the weighted mean energy of 175 keV for 177Lu. The calculated CF using the TEW correction was 17{\%} higher than using the ESSE method for a water-filled phantom. However, our findings showed that an appropriate scatter window combination can reduce this difference between TEW and ESSE methods. Conclusions: The present work implies that choosing a suitable width of scatter energy windows can reduce uncertainties in radioactivity quantification. It is suggested to generate the attenuation map at 113 keV and 208 keV, separately. Furthermore, using small VOIs is suggested in CF calculation.",
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TY - JOUR

T1 - The effect of attenuation map, scatter energy window width, and volume of interest on the calibration factor calculation in quantitative 177Lu SPECT imaging

T2 - Simulation and phantom study

AU - Karimi Ghodoosi, Elham

AU - D'Alessandria, Calogero

AU - Li, Ye

AU - Bartel, Alexandra

AU - Köhner, Markus

AU - Höllriegl, Vera

AU - Navab, Nassir

AU - Eiber, Matthias

AU - Li, Wei Bo

AU - Frey, Eric

AU - Ziegler, Sibylle

PY - 2018/12/1

Y1 - 2018/12/1

N2 - Purpose: The objective of this study was to evaluate the image degrading factors in quantitative 177Lu SPECT imaging when using both main gamma photopeak energies. Methods: Phantom measurements with two different vials containing various calibrated activities in air or water were performed to derive a mean calibration factor (CF) for large and small volumes of interest (VOIs). In addition, Monte Carlo simulations were utilized to investigate the effect of scatter energy window width, scatter correction method, such as effective scatter source estimation (ESSE) and triple energy window (TEW), and attenuation map on the quantification of 177Lu. Results: The measured mean CF using large and small VOIs in water was 4.50 ± 0.80 and 4.80 ± 0.72 cps MBq−1, respectively. Simulations showed a reference CF of 3.3 cps MBq−1 for the water-filled phantom considering all photons excluding scattered events. By using the attenuation map generated for 190 keV photons, the calculated CFs for 113 keV and 208 keV are 10% lower than by using the weighted mean energy of 175 keV for 177Lu. The calculated CF using the TEW correction was 17% higher than using the ESSE method for a water-filled phantom. However, our findings showed that an appropriate scatter window combination can reduce this difference between TEW and ESSE methods. Conclusions: The present work implies that choosing a suitable width of scatter energy windows can reduce uncertainties in radioactivity quantification. It is suggested to generate the attenuation map at 113 keV and 208 keV, separately. Furthermore, using small VOIs is suggested in CF calculation.

AB - Purpose: The objective of this study was to evaluate the image degrading factors in quantitative 177Lu SPECT imaging when using both main gamma photopeak energies. Methods: Phantom measurements with two different vials containing various calibrated activities in air or water were performed to derive a mean calibration factor (CF) for large and small volumes of interest (VOIs). In addition, Monte Carlo simulations were utilized to investigate the effect of scatter energy window width, scatter correction method, such as effective scatter source estimation (ESSE) and triple energy window (TEW), and attenuation map on the quantification of 177Lu. Results: The measured mean CF using large and small VOIs in water was 4.50 ± 0.80 and 4.80 ± 0.72 cps MBq−1, respectively. Simulations showed a reference CF of 3.3 cps MBq−1 for the water-filled phantom considering all photons excluding scattered events. By using the attenuation map generated for 190 keV photons, the calculated CFs for 113 keV and 208 keV are 10% lower than by using the weighted mean energy of 175 keV for 177Lu. The calculated CF using the TEW correction was 17% higher than using the ESSE method for a water-filled phantom. However, our findings showed that an appropriate scatter window combination can reduce this difference between TEW and ESSE methods. Conclusions: The present work implies that choosing a suitable width of scatter energy windows can reduce uncertainties in radioactivity quantification. It is suggested to generate the attenuation map at 113 keV and 208 keV, separately. Furthermore, using small VOIs is suggested in CF calculation.

KW - Lu

KW - Attenuation map

KW - Calibration factor

KW - Scatter fraction

KW - Scatter window

KW - SPECT/CT

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M3 - Article

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JO - Physica Medica

JF - Physica Medica

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