Limits...
Automated movement correction for dynamic PET/CT images: evaluation with phantom and patient data.

Ye H, Wong KP, Wardak M, Dahlbom M, Kepe V, Barrio JR, Nelson LD, Small GW, Huang SC - PLoS ONE (2014)

Bottom Line: Image artifacts were significantly diminished after MC.There were significant differences (P<0.05) in the FDDNP DVR and FDG Ki values in the parietal and temporal regions after MC.In conclusion, MC applied to dynamic brain FDDNP and FDG PET/CT scans could improve the qualitative and quantitative aspects of images of both tracers.

View Article: PubMed Central - PubMed

Affiliation: Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America.

ABSTRACT
Head movement during a dynamic brain PET/CT imaging results in mismatch between CT and dynamic PET images. It can cause artifacts in CT-based attenuation corrected PET images, thus affecting both the qualitative and quantitative aspects of the dynamic PET images and the derived parametric images. In this study, we developed an automated retrospective image-based movement correction (MC) procedure. The MC method first registered the CT image to each dynamic PET frames, then re-reconstructed the PET frames with CT-based attenuation correction, and finally re-aligned all the PET frames to the same position. We evaluated the MC method's performance on the Hoffman phantom and dynamic FDDNP and FDG PET/CT images of patients with neurodegenerative disease or with poor compliance. Dynamic FDDNP PET/CT images (65 min) were obtained from 12 patients and dynamic FDG PET/CT images (60 min) were obtained from 6 patients. Logan analysis with cerebellum as the reference region was used to generate regional distribution volume ratio (DVR) for FDDNP scan before and after MC. For FDG studies, the image derived input function was used to generate parametric image of FDG uptake constant (Ki) before and after MC. Phantom study showed high accuracy of registration between PET and CT and improved PET images after MC. In patient study, head movement was observed in all subjects, especially in late PET frames with an average displacement of 6.92 mm. The z-direction translation (average maximum = 5.32 mm) and x-axis rotation (average maximum = 5.19 degrees) occurred most frequently. Image artifacts were significantly diminished after MC. There were significant differences (P<0.05) in the FDDNP DVR and FDG Ki values in the parietal and temporal regions after MC. In conclusion, MC applied to dynamic brain FDDNP and FDG PET/CT scans could improve the qualitative and quantitative aspects of images of both tracers.

Show MeSH

Related in: MedlinePlus

Artifacts of AC with largely misaligned CTs in FDG phantom study.Panel A: the difference map between PET FR12 AC with a 10 mm mismatched CT (CT1) and the reference PET image. The misalignment between PET and CT caused significant AC artifacts; Panel B: the difference map between PET Frame12 AC with a 10 mm mismatched CT (CT1) and the same PET frame AC using the physically aligned CT (CT12). The misalignment between PET and CT caused significant AC artifacts. However, the AC matrix did not add extra noise to the PET images.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4128781&req=5

pone-0103745-g004: Artifacts of AC with largely misaligned CTs in FDG phantom study.Panel A: the difference map between PET FR12 AC with a 10 mm mismatched CT (CT1) and the reference PET image. The misalignment between PET and CT caused significant AC artifacts; Panel B: the difference map between PET Frame12 AC with a 10 mm mismatched CT (CT1) and the same PET frame AC using the physically aligned CT (CT12). The misalignment between PET and CT caused significant AC artifacts. However, the AC matrix did not add extra noise to the PET images.

Mentions: Difference maps were used to further evaluate and validate the MC procedure on the phantom studies. They showed that the accuracy of co-registration (error <2 mm) was adequate to avoid introducing extra artifacts and the MC procedure eliminated artifacts due to large mismatches between PET and CT images. In Figs. 3, 4, and 5, all PET images were co-registered to the reference frame for comparison. The same color scale was applied across all PET frames. A different color scale was applied to the difference maps, where green denotes zero difference. Fig. 3 shows that for small misalignment (2 mm in z direction) between PET and CT, the AC artifact was not noticeable compared to the images with correctly aligned PET and CT. Fig. 4 shows apparent artifacts due to large mismatches between PET and CT images. Panel A of Fig. 4 shows the difference map between the PET frame (FR12) which was based on a misaligned CT (CT1) for AC and the reference frame (FR1) which used a physically aligned CT (CT1). The difference map between the FR12 and the same PET frame based on a physically aligned CT (CT12) is shown in Panel B. Fig. 4 shows that the misalignment between PET and CT caused significant AC artifacts. However, the attenuation correction matrix did not add extra noise to the PET images. After MC, there were no noticeable differences, except noise, among the PET frames (Fig. 5).


Automated movement correction for dynamic PET/CT images: evaluation with phantom and patient data.

Ye H, Wong KP, Wardak M, Dahlbom M, Kepe V, Barrio JR, Nelson LD, Small GW, Huang SC - PLoS ONE (2014)

Artifacts of AC with largely misaligned CTs in FDG phantom study.Panel A: the difference map between PET FR12 AC with a 10 mm mismatched CT (CT1) and the reference PET image. The misalignment between PET and CT caused significant AC artifacts; Panel B: the difference map between PET Frame12 AC with a 10 mm mismatched CT (CT1) and the same PET frame AC using the physically aligned CT (CT12). The misalignment between PET and CT caused significant AC artifacts. However, the AC matrix did not add extra noise to the PET images.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4128781&req=5

pone-0103745-g004: Artifacts of AC with largely misaligned CTs in FDG phantom study.Panel A: the difference map between PET FR12 AC with a 10 mm mismatched CT (CT1) and the reference PET image. The misalignment between PET and CT caused significant AC artifacts; Panel B: the difference map between PET Frame12 AC with a 10 mm mismatched CT (CT1) and the same PET frame AC using the physically aligned CT (CT12). The misalignment between PET and CT caused significant AC artifacts. However, the AC matrix did not add extra noise to the PET images.
Mentions: Difference maps were used to further evaluate and validate the MC procedure on the phantom studies. They showed that the accuracy of co-registration (error <2 mm) was adequate to avoid introducing extra artifacts and the MC procedure eliminated artifacts due to large mismatches between PET and CT images. In Figs. 3, 4, and 5, all PET images were co-registered to the reference frame for comparison. The same color scale was applied across all PET frames. A different color scale was applied to the difference maps, where green denotes zero difference. Fig. 3 shows that for small misalignment (2 mm in z direction) between PET and CT, the AC artifact was not noticeable compared to the images with correctly aligned PET and CT. Fig. 4 shows apparent artifacts due to large mismatches between PET and CT images. Panel A of Fig. 4 shows the difference map between the PET frame (FR12) which was based on a misaligned CT (CT1) for AC and the reference frame (FR1) which used a physically aligned CT (CT1). The difference map between the FR12 and the same PET frame based on a physically aligned CT (CT12) is shown in Panel B. Fig. 4 shows that the misalignment between PET and CT caused significant AC artifacts. However, the attenuation correction matrix did not add extra noise to the PET images. After MC, there were no noticeable differences, except noise, among the PET frames (Fig. 5).

Bottom Line: Image artifacts were significantly diminished after MC.There were significant differences (P<0.05) in the FDDNP DVR and FDG Ki values in the parietal and temporal regions after MC.In conclusion, MC applied to dynamic brain FDDNP and FDG PET/CT scans could improve the qualitative and quantitative aspects of images of both tracers.

View Article: PubMed Central - PubMed

Affiliation: Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America.

ABSTRACT
Head movement during a dynamic brain PET/CT imaging results in mismatch between CT and dynamic PET images. It can cause artifacts in CT-based attenuation corrected PET images, thus affecting both the qualitative and quantitative aspects of the dynamic PET images and the derived parametric images. In this study, we developed an automated retrospective image-based movement correction (MC) procedure. The MC method first registered the CT image to each dynamic PET frames, then re-reconstructed the PET frames with CT-based attenuation correction, and finally re-aligned all the PET frames to the same position. We evaluated the MC method's performance on the Hoffman phantom and dynamic FDDNP and FDG PET/CT images of patients with neurodegenerative disease or with poor compliance. Dynamic FDDNP PET/CT images (65 min) were obtained from 12 patients and dynamic FDG PET/CT images (60 min) were obtained from 6 patients. Logan analysis with cerebellum as the reference region was used to generate regional distribution volume ratio (DVR) for FDDNP scan before and after MC. For FDG studies, the image derived input function was used to generate parametric image of FDG uptake constant (Ki) before and after MC. Phantom study showed high accuracy of registration between PET and CT and improved PET images after MC. In patient study, head movement was observed in all subjects, especially in late PET frames with an average displacement of 6.92 mm. The z-direction translation (average maximum = 5.32 mm) and x-axis rotation (average maximum = 5.19 degrees) occurred most frequently. Image artifacts were significantly diminished after MC. There were significant differences (P<0.05) in the FDDNP DVR and FDG Ki values in the parietal and temporal regions after MC. In conclusion, MC applied to dynamic brain FDDNP and FDG PET/CT scans could improve the qualitative and quantitative aspects of images of both tracers.

Show MeSH
Related in: MedlinePlus