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Comparing approaches to correct for respiratory motion in NH3 PET-CT cardiac perfusion imaging.

Schleyer PJ, O'Doherty MJ, Barrington SF, Morton G, Marsden PK - Nucl Med Commun (2013)

Bottom Line: However, cases were found where alignment worsened and severe artefacts resulted.This occurred in more cases and to a greater extent for the averaged and gated CT, where the anterior wall intensity reduced by more than 10% in 21 and 24 cases, respectively, compared with six cases for the pseudo-gated CT.The pseudo-gated CT was found to be the most robust method.

View Article: PubMed Central - PubMed

Affiliation: Division of Imaging Sciences and Biomedical Engineering, King's College London, King's Health Partners, St. Thomas' Hospital, London, UK.

ABSTRACT

Aim: Respiratory motion affects cardiac PET-computed tomography (CT) imaging by reducing attenuation correction (AC) accuracy and by introducing blur. The aim of this study was to compare three approaches for reducing motion-induced AC errors and evaluate the inclusion of respiratory motion correction.

Materials and methods: AC with a helical CT was compared with averaged cine and gated cine CT, as well as with a pseudo-gated CT, which was produced by applying PET-derived motion fields to the helical CT. Data-driven gating was used to produce respiratory-gated PET and CT images, and 60 NH3 PET scans were attenuation corrected with each of the CTs. Respiratory motion correction was applied to the gated and pseudo-gated attenuation-corrected PET images.

Results: Anterior and lateral wall intensity measured in attenuation-corrected PET images generally increased when PET-CT alignment improved and decreased when alignment degraded. On average, all methods improved PET-CT liver and cardiac alignment, and increased anterior wall intensity by more than 10% in 36, 33 and 25 cases for the averaged, gated and pseudo-gated CTAC PET images, respectively. However, cases were found where alignment worsened and severe artefacts resulted. This occurred in more cases and to a greater extent for the averaged and gated CT, where the anterior wall intensity reduced by more than 10% in 21 and 24 cases, respectively, compared with six cases for the pseudo-gated CT. Application of respiratory motion correction increased the average anterior and inferior wall intensity, but only 13% of cases increased by more than 10%.

Conclusion: All methods improved average respiratory-induced AC errors; however, some severe artefacts were produced. The pseudo-gated CT was found to be the most robust method.

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(a) Example 1. (b) Example 2. Bullseye and horizontal long-axis images of two example cases. (a) An artefact that resembles a defect on the anterior wall is seen on the ACHCT PET images, which results from a PET-CT spatial mismatch. This artefact is corrected in ACACT, ACGCT and ACpseudo images from improved PET-CT alignment. (b) Good PET-CT alignment exists for the ACHCT and ACpseudo data sets, and no defect is seen. For the ACACT and ACGCT images, worse PET-CT alignment produces an artefact that appears as an anterior wall defect. AC, attenuation correction; ACT, averaged cine CT; CT, computed tomography; HCT, helical CT; NAC, non-attenuation-corrected.
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Figure 2: (a) Example 1. (b) Example 2. Bullseye and horizontal long-axis images of two example cases. (a) An artefact that resembles a defect on the anterior wall is seen on the ACHCT PET images, which results from a PET-CT spatial mismatch. This artefact is corrected in ACACT, ACGCT and ACpseudo images from improved PET-CT alignment. (b) Good PET-CT alignment exists for the ACHCT and ACpseudo data sets, and no defect is seen. For the ACACT and ACGCT images, worse PET-CT alignment produces an artefact that appears as an anterior wall defect. AC, attenuation correction; ACT, averaged cine CT; CT, computed tomography; HCT, helical CT; NAC, non-attenuation-corrected.

Mentions: Using the HCT as a baseline for comparison, the SA PET images ACACT, ACGCT and ACpseudo were compared with the ACHCT images to observe the relative change in myocardial wall intensity. The PET images of two example patients are shown in Fig. 2. In Fig. 2a, the ACT, GCT and pseudo-gated CT are all seen to improve the alignment when compared with the HCT. An anterior apical wall defect apparent in the ACHCT PET image is not present in the ACACT, ACGCT and ACpseudo PET images. For this case, the mean liver and cardiac wall PET-CT misalignment was reduced from 10.6 and 7.9 mm, respectively, when the HCT was used to 2.7 and 3.0 mm for the GCT and 4.7 and 0.6 mm for the pseudo-gated CT, respectively.


Comparing approaches to correct for respiratory motion in NH3 PET-CT cardiac perfusion imaging.

Schleyer PJ, O'Doherty MJ, Barrington SF, Morton G, Marsden PK - Nucl Med Commun (2013)

(a) Example 1. (b) Example 2. Bullseye and horizontal long-axis images of two example cases. (a) An artefact that resembles a defect on the anterior wall is seen on the ACHCT PET images, which results from a PET-CT spatial mismatch. This artefact is corrected in ACACT, ACGCT and ACpseudo images from improved PET-CT alignment. (b) Good PET-CT alignment exists for the ACHCT and ACpseudo data sets, and no defect is seen. For the ACACT and ACGCT images, worse PET-CT alignment produces an artefact that appears as an anterior wall defect. AC, attenuation correction; ACT, averaged cine CT; CT, computed tomography; HCT, helical CT; NAC, non-attenuation-corrected.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3815144&req=5

Figure 2: (a) Example 1. (b) Example 2. Bullseye and horizontal long-axis images of two example cases. (a) An artefact that resembles a defect on the anterior wall is seen on the ACHCT PET images, which results from a PET-CT spatial mismatch. This artefact is corrected in ACACT, ACGCT and ACpseudo images from improved PET-CT alignment. (b) Good PET-CT alignment exists for the ACHCT and ACpseudo data sets, and no defect is seen. For the ACACT and ACGCT images, worse PET-CT alignment produces an artefact that appears as an anterior wall defect. AC, attenuation correction; ACT, averaged cine CT; CT, computed tomography; HCT, helical CT; NAC, non-attenuation-corrected.
Mentions: Using the HCT as a baseline for comparison, the SA PET images ACACT, ACGCT and ACpseudo were compared with the ACHCT images to observe the relative change in myocardial wall intensity. The PET images of two example patients are shown in Fig. 2. In Fig. 2a, the ACT, GCT and pseudo-gated CT are all seen to improve the alignment when compared with the HCT. An anterior apical wall defect apparent in the ACHCT PET image is not present in the ACACT, ACGCT and ACpseudo PET images. For this case, the mean liver and cardiac wall PET-CT misalignment was reduced from 10.6 and 7.9 mm, respectively, when the HCT was used to 2.7 and 3.0 mm for the GCT and 4.7 and 0.6 mm for the pseudo-gated CT, respectively.

Bottom Line: However, cases were found where alignment worsened and severe artefacts resulted.This occurred in more cases and to a greater extent for the averaged and gated CT, where the anterior wall intensity reduced by more than 10% in 21 and 24 cases, respectively, compared with six cases for the pseudo-gated CT.The pseudo-gated CT was found to be the most robust method.

View Article: PubMed Central - PubMed

Affiliation: Division of Imaging Sciences and Biomedical Engineering, King's College London, King's Health Partners, St. Thomas' Hospital, London, UK.

ABSTRACT

Aim: Respiratory motion affects cardiac PET-computed tomography (CT) imaging by reducing attenuation correction (AC) accuracy and by introducing blur. The aim of this study was to compare three approaches for reducing motion-induced AC errors and evaluate the inclusion of respiratory motion correction.

Materials and methods: AC with a helical CT was compared with averaged cine and gated cine CT, as well as with a pseudo-gated CT, which was produced by applying PET-derived motion fields to the helical CT. Data-driven gating was used to produce respiratory-gated PET and CT images, and 60 NH3 PET scans were attenuation corrected with each of the CTs. Respiratory motion correction was applied to the gated and pseudo-gated attenuation-corrected PET images.

Results: Anterior and lateral wall intensity measured in attenuation-corrected PET images generally increased when PET-CT alignment improved and decreased when alignment degraded. On average, all methods improved PET-CT liver and cardiac alignment, and increased anterior wall intensity by more than 10% in 36, 33 and 25 cases for the averaged, gated and pseudo-gated CTAC PET images, respectively. However, cases were found where alignment worsened and severe artefacts resulted. This occurred in more cases and to a greater extent for the averaged and gated CT, where the anterior wall intensity reduced by more than 10% in 21 and 24 cases, respectively, compared with six cases for the pseudo-gated CT. Application of respiratory motion correction increased the average anterior and inferior wall intensity, but only 13% of cases increased by more than 10%.

Conclusion: All methods improved average respiratory-induced AC errors; however, some severe artefacts were produced. The pseudo-gated CT was found to be the most robust method.

Show MeSH