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Transmission-dependent convolution subtraction of 99m-Tc-HMPAO rCBF SPECT - a Monte Carlo study
Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
2005 (English)In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 52, no 1, 231-237 p.Article in journal (Refereed) Published
Abstract [en]

Transmission-dependent convolution subtraction has been shown to be useful when correcting for malpositioned scattered events in single photon emission computed tomography (SPECT). The method is based on convolution subtraction but includes a matrix of scatter fractions instead of a global scatter fraction. In this study, this method is evaluated for regional cerebral blood flow SPECT with 99mTc-hexamethyl propylene-amine oxime (HMPAO) by using Monte Carlo simulations. Different geometries for generating the scatter fractions as a function of the attenuation path length are studied and compared. The most optimal value of the exponential describing the falloff of the monoexponential scatter kernel is determined for each geometry. The method is also compared with convolution subtraction with a global scatter fraction. It is shown that the most optimal of the tested geometries is a homogeneous activity distribution. A scatter kernel with an exponential of 0.15 pixel-1 is most optimal for this geometry. A comparison with convolution subtraction shows that transmission-dependent convolution subtraction can give more accurate results if used with optimal parameters.

Place, publisher, year, edition, pages
2005. Vol. 52, no 1, 231-237 p.
Keyword [en]
rCBF SPECT, scatter correction, TDCS, transmission-dependent convolution subtraction
URN: urn:nbn:se:umu:diva-14159DOI: 10.1109/tns.2005.844441OAI: diva2:153830
Available from: 2006-11-08 Created: 2006-11-08 Last updated: 2011-03-21Bibliographically approved
In thesis
1. Corrections for improved quantitative accuracy in SPECT and planar scintigraphic imaging
Open this publication in new window or tab >>Corrections for improved quantitative accuracy in SPECT and planar scintigraphic imaging
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A quantitative evaluation of single photon emission computed tomography (SPECT) and planar scintigraphic imaging may be valuable for both diagnostic and therapeutic purposes. For an accurate quantification it is usually necessary to correct for attenuation and scatter and in some cases also for septal penetration. For planar imaging a background correction for the contribution from over- and underlying tissues is needed. In this work a few correction methods have been evaluated and further developed. Much of the work relies on the Monte Carlo method as a tool for evaluation and optimisation.

A method for quantifying the activity of I-125 labelled antibodies in a tumour inoculated in the flank of a mouse, based on planar scintigraphic imaging with a pin-hole collimator, has been developed and two different methods for background subtraction have been compared. The activity estimates of the tumours were compared with measurements in vitro.

The major part of this work is attributed to SPECT. A method for attenuation and scatter correction of brain SPECT based on computed tomography (CT) images of the same patient has been developed, using an attenuation map calculated from the CT image volume. The attenuation map is utilised not only for attenuation correction, but also for scatter correction with transmission dependent convolution subtraction (TDCS). A registration method based on fiducial markers, placed on three chosen points during the SPECT examination, was evaluated.

The scatter correction method, TDCS, was then optimised for regional cerebral blood flow (rCBF) SPECT with Tc-99m, and was also compared with a related method, convolution scatter subtraction (CSS). TDCS has been claimed to be an iterative technique. This requires however some modifications of the method, which have been demonstrated and evaluated for a simulation with a point source.

When the Monte Carlo method is used for evaluation of corrections for septal penetration, it is important that interactions in the collimator are taken into account. A new version of the Monte Carlo program SIMIND with this capability has been evaluated by comparing measured and simulated images and energy spectra. This code was later used for the evaluation of a few different methods for correction of scatter and septal penetration of I-123 brain SPECT. The methods were CSS, TDCS and a method where correction for scatter and septal penetration are included in the iterative reconstruction. This study shows that quantitative accuracy in I-123 brain SPECT benefits from separate modelling of scatter and septal penetration.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2005. 88 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 983
Quantitative SPECT, scintigraphic imaging, attenuation correction, scatter correction, collimator-detector response, septal penetration, background correction, Monte Carlo simulation
National Category
Radiology, Nuclear Medicine and Medical Imaging
urn:nbn:se:umu:diva-636 (URN)91-7305-938-2 (ISBN)
Public defence
2005-12-09, 244, 7, Norrlands Universitetssjukhus, Umeå, 13:00 (English)
Available from: 2005-11-17 Created: 2005-11-17 Last updated: 2012-04-03Bibliographically approved

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