liu.seSearch for publications in DiVA
Change search
ReferencesLink to record
Permanent link

Direct link
Dual-window scatter correction and energy window setting in cerebral blood flow SPECT: a Monte Carlo study
Department of Radiation Physics, Göteborg University, Sahlgrenska University Hospital, Göteborg, Sweden .
Department of Radiation Physics, Göteborg University, Sahlgrenska University Hospital, Göteborg, Sweden .
Department of Radiation Physics, Göteborg University, Sahlgrenska University Hospital, Göteborg, Sweden .
Radiation Physics Department, Lund University, The Jubileum Institute, Lund, Sweden .
Show others and affiliations
2000 (English)In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 45, no 11, 3431-3440 p.Article in journal (Refereed) Published
Abstract [en]

The image quality in SPECT studies of the regional cerebral blood flow (rCBF) performed with 99mTc-HMPAO is degraded by scattered photons. The finite energy resolution of the gamma camera makes the detection of scattered photons unavoidable, and this is observed in the image as an impaired contrast between grey and white matter structures.

In this work, a Monte Carlo simulated SPECT study of a realistic voxel-based brain phantom was used to evaluate the resulting contrast-to-noise ratio for a number of energy window settings, with and without the dual-window scatter correction. Values of the scaling factor k, used to obtain the fraction of scattered photons in the photopeak window, were estimated for each energy window.

The use of a narrower, asymmetric, energy discrimination window improved the contrast, with a subsequent increase in statistical noise due to the lower number of counts. The photopeak-window setting giving the best contrast-to-noise ratio was found to be the same whether or not scatter correction was applied. Its value was 17% centred at 142 keV. At the optimum photopeak-window setting, the contrast was improved by using scatter correction, but the contrast-to-noise ratio was made worse.

Place, publisher, year, edition, pages
Institute of Physics Publishing , 2000. Vol. 45, no 11, 3431-3440 p.
National Category
Medical Image Processing
URN: urn:nbn:se:liu:diva-79207DOI: 10.1088/0031-9155/45/11/323PubMedID: 11098915OAI: diva2:539129
Available from: 2012-07-03 Created: 2012-07-03 Last updated: 2013-02-27
In thesis
1. Evaluation of attenuation and scatter corrections in lung and brain SPECT
Open this publication in new window or tab >>Evaluation of attenuation and scatter corrections in lung and brain SPECT
2001 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Single Photon Emission Computed Tomography (SPECT) is used to image functional processes in the human body. The image process is affected by physical effects such as attenuation, scatter, spatial resolution and statistical noise. The aim of this work was to investigate how attenuation and scatter effects and their associated correction methods affect the image quality in lung and brain SPECT.

The effects of attenuation and scattering on the image of a uniform activity distribution in the lungs was investigated using Monte Carlo simulated data and the attenuation effect was evaluated in healthy volunteers. The homogeneity was measured as the CV inside a well-defined lung contour. The attenuation effect in lung SPECT was estimated to be about 13-14% expressed as the CV. The homogeneity improved with increasing accuracy of the attenuation correction method. After attenuation correction the remaining inhomogeneity in healthy subjects was considerable and could not be explained by statistical noise and camera non-uniformity. A non-uniform attenuation correction was thus required and a TCT-based density map was found to be adequate in most instances.

The accuracy of the attenuation correction methods was studied in Monte Carlo simulated brain SPECT using the normalised mean square error, NMSE. The different degrees of accuracy in the methods were also reflected in the absolute deviation of the relative regional cerebral blood flow (rCBF) according to the min-max method. The NMSE value improved with the accuracy of the attenuationcorrection method. The difference in relative rCBF value was generally less than 5%. Therefore, it is unlikely that the choice of attenuation correction method will affect the diagnostic accuracy.

The detectability, expressed as the contrast-to-noise-ratio dependence on the choice of energy window, was evaluated using SPECT studies of a thorax phantom containing cold lesions inside the lungs and a realistic brain phantom. The effects of subtractive scatter correction methods such as the dual-window method (DW), the triple-energy-window method (TEW) and the Klein-Nishina method (KN) were also evaluated. An optimal photopeak window setting was found to be 128-154 keV in lung SPECT for a gamma camera with 10% energy resolution, and 130-154 keV in rCBF SPECT for a gamma camera with 9% energy resolution. The detection limit for lung SPECT for spherical lesions is about 2 cm in diameter when normal variations in the lungs are relatively small compared with the statistical noise level. Under these conditions the detectability is degraded by using scatter correction, except when the TEW scatter correction is used for small lesions (<3 cm in diameter), when about the same detectability is achieved.

Place, publisher, year, edition, pages
Göteborg: Göteborgs universitet, 2001. 64 p.
SPECT, attenuation, scatter, detectability, Monte Carlo simulation
National Category
Medical and Health Sciences
urn:nbn:se:liu:diva-28146 (URN)12959 (Local ID)91-638-4850-X (ISBN)12959 (Archive number)12959 (OAI)
Public defence
2001-06-01, Sal F3 Odontologen, Medicinaregatan 12 D, Göteborg, 09:15 (Swedish)

Doktorsavhandling framlagd vid Göteborgs universitet 2001-06-01

Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2013-02-27

Open Access in DiVA

No full text

Other links

Publisher's full textPubMed

Search in DiVA

By author/editor
Gustafsson, Agnetha
In the same journal
Physics in Medicine and Biology
Medical Image Processing

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 84 hits
ReferencesLink to record
Permanent link

Direct link