Cristin-prosjekt-ID: 457232
Sist endret: 26. februar 2020 16:23

Cristin-prosjekt-ID: 457232
Sist endret: 26. februar 2020 16:23
Prosjekt

Optimization of pediatric chest CT

prosjektleder

Mona Øynes
ved Institutt for helse og funksjon ved Høgskulen på Vestlandet

prosjekteier / koordinerende forskningsansvarlig enhet

  • Høgskulen på Vestlandet

Klassifisering

Vitenskapsdisipliner

Radiologi og bildediagnostikk

Emneord

Ioniserende stråling

Kategorier

Prosjektkategori

  • Anvendt forskning

Kontaktinformasjon

Telefon
55585618
Sted
Mona Øynes

Tidsramme

Avsluttet
Start: 1. februar 2013 Slutt: 1. juli 2020

Beskrivelse Beskrivelse

Tittel

Optimization of pediatric chest CT

Vitenskapelig sammendrag

Optimizing pediatric chest CT: Reduction of tube potential combined with iterative reconstruction.

Introduction

Since Computed Tomography (CT) was introduced in the 1970’s, its use has rapidly increased, because of the diagnostic benefits of CT over conventional x-ray examinations.  The evidence of an additional lifetime risk of cancer due to the radiation of CT scans is increasing. Children are more sensitive to radiation than adults are, and have a longer expected lifetime, thus a significantly higher risk of developing cancer later in life. The Nordic radiation protection authorities expresses concern about the increased use of CT in the Nordic countries, and emphasizes the need to optimize such examinations.

An important technique for reduction of radiation dose in paediatric CT examinations, is the use of optimal tube potential. The tube potential should be optimized in relation to the size of the patient, and be reduced for smaller patients. Reduced tube potential is combined with increased tube current, to compensate for the reduced SNR that would otherwise be caused by the lower number of photons resulting from the reduced tube potential.

The aim of this study is to investigate in what degree an increased tube current can be replaced with the use of SAFIRE instead of FBP, when the tube potential is decreased for paediatric chest CT examinations.

Method

A CIRS ATOM Dosimetry Verification Phantom model 705 equivalent to a 5 year old child was scanned in a Siemens Somatom Definition AS+ CT scanner with four different tube potentials. Images were reconstructed using filtered backprojection method (FBP) and the iterative reconstruction method Sinogram Affirmed Iterative Reconstruction (SAFIRE) with three different levels. Image noise, mean Hounsfield value, signal- to- noise ratio (SNR) and contrast- to noise ratio (CNR) were calculated from were calculated from voxel values in selected region-of-interests (ROI’s). CT dose index (CTDIvol) and dose-length-product (DLP) calculated of the CT scanner are also reported. The changes in SNR and CNR when filtered back projection was replaced with iterative reconstruction for the different tube potential settings available were studied.

Results

Both SNR and CNR decreases with decreasing tube potential, when all other factors are kept constant. For a fixed tube potential, both SNR and CNR are higher when the images are reconstructed with SAFIRE than the images which are reconstructed with FBP. SNR and CNR are increasing when the level of noise removal of SAFIRE is increasing. If the tube voltage is reduced one level, that is from 120 kV to 100 kV, or from 100 kV to 80 kV, the reduction of CNR is compensated with the replacement of FBP with SAFIRE level 2. A reduction of tube voltage with one level gives a reduction of 40% - 50% of the CTDIvol and DLP.

Conclusion

Using SAFIRE level 2 in combination with reduction of tube voltage can reduce the radiation dose given the paediatric patient in a chest CT with 40-50 %, thus reducing the carcinogenetic risk associated with the procedure.

Tittel

Optimalisering av pediatrisk CT thorax

Vitenskapelig sammendrag

Optimizing pediatric chest CT: Reduction of tube potential combined with iterative reconstruction.

Introduction

Since Computed Tomography (CT) was introduced in the 1970’s, its use has rapidly increased, because of the diagnostic benefits of CT over conventional x-ray examinations.  The evidence of an additional lifetime risk of cancer due to the radiation of CT scans is increasing. Children are more sensitive to radiation than adults are, and have a longer expected lifetime, thus a significantly higher risk of developing cancer later in life. The Nordic radiation protection authorities expresses concern about the increased use of CT in the Nordic countries, and emphasizes the need to optimize such examinations.

An important technique for reduction of radiation dose in paediatric CT examinations, is the use of optimal tube potential. The tube potential should be optimized in relation to the size of the patient, and be reduced for smaller patients. Reduced tube potential is combined with increased tube current, to compensate for the reduced SNR that would otherwise be caused by the lower number of photons resulting from the reduced tube potential.

The aim of this study is to investigate in what degree an increased tube current can be replaced with the use of SAFIRE instead of FBP, when the tube potential is decreased for paediatric chest CT examinations.

 

Method

A CIRS ATOM Dosimetry Verification Phantom model 705 equivalent to a 5 year old child was scanned in a Siemens Somatom Definition AS+ CT scanner with four different tube potentials. Images were reconstructed using filtered backprojection method (FBP) and the iterative reconstruction method Sinogram Affirmed Iterative Reconstruction (SAFIRE) with three different levels. Image noise, mean Hounsfield value, signal- to- noise ratio (SNR) and contrast- to noise ratio (CNR) were calculated from were calculated from voxel values in selected region-of-interests (ROI’s). CT dose index (CTDIvol) and dose-length-product (DLP) calculated of the CT scanner are also reported. The changes in SNR and CNR when filtered back projection was replaced with iterative reconstruction for the different tube potential settings available were studied.

Results

Both SNR and CNR decreases with decreasing tube potential, when all other factors are kept constant. For a fixed tube potential, both SNR and CNR are higher when the images are reconstructed with SAFIRE than the images which are reconstructed with FBP. SNR and CNR are increasing when the level of noise removal of SAFIRE is increasing. If the tube voltage is reduced one level, that is from 120 kV to 100 kV, or from 100 kV to 80 kV, the reduction of CNR is compensated with the replacement of FBP with SAFIRE level 2. A reduction of tube voltage with one level gives a reduction of 40% - 50% of the CTDIvol and DLP.

Conclusion

Using SAFIRE level 2 in combination with reduction of tube voltage can reduce the radiation dose given the paediatric patient in a chest CT with 40-50 %, thus reducing the carcinogenetic risk associated with the procedure.

prosjektdeltakere

prosjektleder

Mona Øynes

  • Tilknyttet:
    Prosjektleder
    ved Institutt for helse og funksjon ved Høgskulen på Vestlandet
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