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Scatter-to-primary based scatter fractions for transmission dependent convolution subtraction of SPECT images
Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Radiofysik.
Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Radiofysik.
2003 (Engelska)Ingår i: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 48, nr 22, s. N323-N328Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

In single photon emission computed tomography (SPECT), transmission-dependent convolution subtraction has been shown to be useful when correcting for scattered events. The method is based on convolution subtraction, but includes a matrix of scatter fractions instead of a global scatter fraction. The method can be extended to iteratively improve the scatter estimate, but in this note we show that this requires a modification of the theory to use scatter-to-total scatter fractions for the first iteration only and scatter-to-primary fractions thereafter. To demonstrate this, scatter correction is performed on a Monte Carlo simulated image of a point source of activity in water. The modification of the theory is compared to corrections where the scatter fractions are based on the scatter-to-total ratio, using one and ten iterations. The resulting ratios of subtracted to original counts are compared to the true scatter-to-total ratio of the simulation and the most accurate result is found for our modification of the theory.

Ort, förlag, år, upplaga, sidor
2003. Vol. 48, nr 22, s. N323-N328
Identifikatorer
URN: urn:nbn:se:umu:diva-4825DOI: 10.1088/0031-9155/48/22/N03PubMedID: 14680275OAI: oai:DiVA.org:umu-4825DiVA, id: diva2:144074
Tillgänglig från: 2005-11-17 Skapad: 2005-11-17 Senast uppdaterad: 2018-06-09Bibliografiskt granskad
Ingår i avhandling
1. Corrections for improved quantitative accuracy in SPECT and planar scintigraphic imaging
Öppna denna publikation i ny flik eller fönster >>Corrections for improved quantitative accuracy in SPECT and planar scintigraphic imaging
2005 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Umeå: Umeå universitet, 2005. s. 88
Serie
Umeå University medical dissertations, ISSN 0346-6612 ; 983
Nyckelord
Quantitative SPECT, scintigraphic imaging, attenuation correction, scatter correction, collimator-detector response, septal penetration, background correction, Monte Carlo simulation
Nationell ämneskategori
Radiologi och bildbehandling
Identifikatorer
urn:nbn:se:umu:diva-636 (URN)91-7305-938-2 (ISBN)
Disputation
2005-12-09, 244, 7, Norrlands Universitetssjukhus, Umeå, 13:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2005-11-17 Skapad: 2005-11-17 Senast uppdaterad: 2018-06-09Bibliografiskt granskad

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