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How much will linked deformable registrations decrease the quality of multi-atlas segmentation fusions?

Sjöberg C, Johansson S, Ahnesjö A - Radiat Oncol (2014)

Bottom Line: The median decrease of the DSC was in the range 2.8% to 8.4% compared to direct registrations for all structures while reducing the computer calculation time to that of a single deformable registration.Linking several registrations showed a DSC decrease almost linear to the number of links, suggesting that extrapolation to zero links provides an observer independent measure of the inherent precision with which the segmentation guidelines can be applied.Linking pre-made registrations of multiple atlases via a runtime registration of a single atlas provides a feasible method for reducing computation time in multi-atlas registration.

View Article: PubMed Central - PubMed

Affiliation: Section for Medical Radiation Physics, Department of Radiology, Oncology and Radiation Sciences, Uppsala University, Akademiska Sjukhuset, Sjukhusfysik Ing. 82, SE-751 85, Uppsala, Sweden. carl.sjoberg@onkologi.uu.se.

ABSTRACT

Background and purpose: Multi-atlas segmentation can yield better results than single atlas segmentation, but practical applications are limited by long calculation times for deformable registration. To shorten the calculation time pre-calculated registrations of atlases could be linked via a single atlas registered in runtime to the current patient. The primary purpose of this work is to investigate and quantify segmentation quality changes introduced by such linked registrations. We also determine the optimal parameters for fusing linked multi-atlas labels using probabilistic weighted fusion.

Material and methods: Computed tomography images of 10 head and neck cancer patients were used as atlases, with parotid glands, submandibular glands, the mandible and lymph node levels II-IV segmented by an experienced radiation oncologist following published consensus guidelines. The change in segmentation quality scored by Dice similarity coefficient (DSC) for linking free-form deformable registrations, modeled by B-splines, was investigated for both single- and multi-atlas label fusion by using a leave-one-out approach.

Results: The median decrease of the DSC was in the range 2.8% to 8.4% compared to direct registrations for all structures while reducing the computer calculation time to that of a single deformable registration. Linking several registrations showed a DSC decrease almost linear to the number of links, suggesting that extrapolation to zero links provides an observer independent measure of the inherent precision with which the segmentation guidelines can be applied.

Conclusions: Linking pre-made registrations of multiple atlases via a runtime registration of a single atlas provides a feasible method for reducing computation time in multi-atlas registration.

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Related in: MedlinePlus

Distributions of relative changes in Dice similarity coefficient (DSC) when linking two registrations compared to direct registration results. Fused segmentations (green dashed lines) and individual segmentation results (blue lines). Different panels show different structures
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Fig4: Distributions of relative changes in Dice similarity coefficient (DSC) when linking two registrations compared to direct registration results. Fused segmentations (green dashed lines) and individual segmentation results (blue lines). Different panels show different structures

Mentions: In Figure 4 the relative DSC change for the individual and fused segmentations are presented. Notably, for the least successful structures, the spread is very large, indicating that the spread of the locations of the segmentation results is larger and that some composed results actually yield better results than the corresponding direct registration. The distribution of segmentation quality for composed and direct segmentation using label fusion are shown in Figure 5 and the fMAD measure as a function of closest distance to the reference is presented for the structures in Figure 6.Figure 4


How much will linked deformable registrations decrease the quality of multi-atlas segmentation fusions?

Sjöberg C, Johansson S, Ahnesjö A - Radiat Oncol (2014)

Distributions of relative changes in Dice similarity coefficient (DSC) when linking two registrations compared to direct registration results. Fused segmentations (green dashed lines) and individual segmentation results (blue lines). Different panels show different structures
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4279807&req=5

Fig4: Distributions of relative changes in Dice similarity coefficient (DSC) when linking two registrations compared to direct registration results. Fused segmentations (green dashed lines) and individual segmentation results (blue lines). Different panels show different structures
Mentions: In Figure 4 the relative DSC change for the individual and fused segmentations are presented. Notably, for the least successful structures, the spread is very large, indicating that the spread of the locations of the segmentation results is larger and that some composed results actually yield better results than the corresponding direct registration. The distribution of segmentation quality for composed and direct segmentation using label fusion are shown in Figure 5 and the fMAD measure as a function of closest distance to the reference is presented for the structures in Figure 6.Figure 4

Bottom Line: The median decrease of the DSC was in the range 2.8% to 8.4% compared to direct registrations for all structures while reducing the computer calculation time to that of a single deformable registration.Linking several registrations showed a DSC decrease almost linear to the number of links, suggesting that extrapolation to zero links provides an observer independent measure of the inherent precision with which the segmentation guidelines can be applied.Linking pre-made registrations of multiple atlases via a runtime registration of a single atlas provides a feasible method for reducing computation time in multi-atlas registration.

View Article: PubMed Central - PubMed

Affiliation: Section for Medical Radiation Physics, Department of Radiology, Oncology and Radiation Sciences, Uppsala University, Akademiska Sjukhuset, Sjukhusfysik Ing. 82, SE-751 85, Uppsala, Sweden. carl.sjoberg@onkologi.uu.se.

ABSTRACT

Background and purpose: Multi-atlas segmentation can yield better results than single atlas segmentation, but practical applications are limited by long calculation times for deformable registration. To shorten the calculation time pre-calculated registrations of atlases could be linked via a single atlas registered in runtime to the current patient. The primary purpose of this work is to investigate and quantify segmentation quality changes introduced by such linked registrations. We also determine the optimal parameters for fusing linked multi-atlas labels using probabilistic weighted fusion.

Material and methods: Computed tomography images of 10 head and neck cancer patients were used as atlases, with parotid glands, submandibular glands, the mandible and lymph node levels II-IV segmented by an experienced radiation oncologist following published consensus guidelines. The change in segmentation quality scored by Dice similarity coefficient (DSC) for linking free-form deformable registrations, modeled by B-splines, was investigated for both single- and multi-atlas label fusion by using a leave-one-out approach.

Results: The median decrease of the DSC was in the range 2.8% to 8.4% compared to direct registrations for all structures while reducing the computer calculation time to that of a single deformable registration. Linking several registrations showed a DSC decrease almost linear to the number of links, suggesting that extrapolation to zero links provides an observer independent measure of the inherent precision with which the segmentation guidelines can be applied.

Conclusions: Linking pre-made registrations of multiple atlases via a runtime registration of a single atlas provides a feasible method for reducing computation time in multi-atlas registration.

Show MeSH
Related in: MedlinePlus