Limits...
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.

Show MeSH

Related in: MedlinePlus

The panels show the decrease of the Dice similarity coefficient (DSC) for structures subject to multiple linked deformable registration transformations. The lines show the result of linear fits to the median values, and the whiskers extends from the 25th to 75th percentiles. The red symbols at zero links show the intra-user variability for redrawing respective structure two times (through editing of single atlas proposals). For the lymph node levels, only data for the union of levels I-VI was available and is shown instead.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig3: The panels show the decrease of the Dice similarity coefficient (DSC) for structures subject to multiple linked deformable registration transformations. The lines show the result of linear fits to the median values, and the whiskers extends from the 25th to 75th percentiles. The red symbols at zero links show the intra-user variability for redrawing respective structure two times (through editing of single atlas proposals). For the lymph node levels, only data for the union of levels I-VI was available and is shown instead.

Mentions: When several registrations are linked, the median of the Dice similarity coefficient decreases approximately linearly with increasing number of linked registrations for all structures as shown in Figure 3. For comparison, DSC values for repeated segmentations of the same structures are shown for l = 0 registrations. For the l = 0 data points in Figure 3, previously unpublished data from [17] was used where one manual segmentation of a patient not included in the leave-one-out data was used as reference and compared to two manually improved (through editing) atlas-based segmentation proposals for the same patient. For the lymph node levels, unfortunately only the union of levels I-VI was available and is thus only an indication of the intra-user uncertainty of lymph node level segmentation as the segmentations in this work was using the unions of levels II-IV.Figure 3


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

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

The panels show the decrease of the Dice similarity coefficient (DSC) for structures subject to multiple linked deformable registration transformations. The lines show the result of linear fits to the median values, and the whiskers extends from the 25th to 75th percentiles. The red symbols at zero links show the intra-user variability for redrawing respective structure two times (through editing of single atlas proposals). For the lymph node levels, only data for the union of levels I-VI was available and is shown instead.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig3: The panels show the decrease of the Dice similarity coefficient (DSC) for structures subject to multiple linked deformable registration transformations. The lines show the result of linear fits to the median values, and the whiskers extends from the 25th to 75th percentiles. The red symbols at zero links show the intra-user variability for redrawing respective structure two times (through editing of single atlas proposals). For the lymph node levels, only data for the union of levels I-VI was available and is shown instead.
Mentions: When several registrations are linked, the median of the Dice similarity coefficient decreases approximately linearly with increasing number of linked registrations for all structures as shown in Figure 3. For comparison, DSC values for repeated segmentations of the same structures are shown for l = 0 registrations. For the l = 0 data points in Figure 3, previously unpublished data from [17] was used where one manual segmentation of a patient not included in the leave-one-out data was used as reference and compared to two manually improved (through editing) atlas-based segmentation proposals for the same patient. For the lymph node levels, unfortunately only the union of levels I-VI was available and is thus only an indication of the intra-user uncertainty of lymph node level segmentation as the segmentations in this work was using the unions of levels II-IV.Figure 3

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