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Impact of region-of-interest method on quantitative analysis of DTI data in the optic tracts.

Lilja Y, Gustafsson O, Ljungberg M, Nilsson D, Starck G - BMC Med Imaging (2016)

Bottom Line: ROI selection in small structures is challenging; the final measurement results could be affected due to the significant impact of small geometrical errors.Manual tracing was performed in 1) the b0 image and 2) a T1-weighted image registered to the FA image.Semi-automatic segmentation was performed based on 3) tractography and 4) the FA-skeleton algorithm in the tract-based spatial statistics (TBSS) framework.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical Neuroscience and Rehabilitation, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden. ylva.lilja@neuro.gu.se.

ABSTRACT

Background: To extract DTI parameters from a specific structure, a region of interest (ROI) must be defined. ROI selection in small structures is challenging; the final measurement results could be affected due to the significant impact of small geometrical errors. In this study the optic tracts were analyzed with the aim to assess differences in DTI parameters due to ROI method and to identify the most reliable method.

Methods: Images of 20 healthy subjects were acquired. Fractional anisotropy (FA) was extracted from the optic tracts by four different ROI methods. Manual tracing was performed in 1) the b0 image and 2) a T1-weighted image registered to the FA image. Semi-automatic segmentation was performed based on 3) tractography and 4) the FA-skeleton algorithm in the tract-based spatial statistics (TBSS) framework. Results were analyzed with regard to ROI method as well as to inter-scan, intra-rater and inter-rater reliability.

Results: The resulting FA values divided the ROI methods into two groups that differed significantly: 1) the FA-skeleton and the b0 methods showed higher FA values compared to 2) the tractography and the T1-weighted methods. The intra- and inter-rater variabilities were similar for all methods, except for the tractography method where the inter-rater variability was higher. The FA-skeleton method had a better reproducibility than the other methods.

Conclusion: Choice of ROI method was found to be highly influential on FA values when the optic tracts were analyzed. The FA-skeleton method performed the best, yielding low variability and high repeatability.

No MeSH data available.


Left: schematic illustration of the visual pathways in the brain (Copyleft from http://thebrain.mcgill.ca). Right: Axial slice of an FA-map, at the level of the optic tracts. The optic tracts are indicated with blue arrows in each image
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Fig1: Left: schematic illustration of the visual pathways in the brain (Copyleft from http://thebrain.mcgill.ca). Right: Axial slice of an FA-map, at the level of the optic tracts. The optic tracts are indicated with blue arrows in each image

Mentions: In this study we focus on the extraction of DTI parameters from the optic tracts (OT) that are part of the anterior visual pathways (Fig. 1). The OTs are an example of small but well-defined structures that are visible in a regular clinical whole-brain DTI scan. Furthermore, the OTs are of specific interest in several pathological conditions affecting the visual pathways and the eyes.Fig. 1


Impact of region-of-interest method on quantitative analysis of DTI data in the optic tracts.

Lilja Y, Gustafsson O, Ljungberg M, Nilsson D, Starck G - BMC Med Imaging (2016)

Left: schematic illustration of the visual pathways in the brain (Copyleft from http://thebrain.mcgill.ca). Right: Axial slice of an FA-map, at the level of the optic tracts. The optic tracts are indicated with blue arrows in each image
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4940685&req=5

Fig1: Left: schematic illustration of the visual pathways in the brain (Copyleft from http://thebrain.mcgill.ca). Right: Axial slice of an FA-map, at the level of the optic tracts. The optic tracts are indicated with blue arrows in each image
Mentions: In this study we focus on the extraction of DTI parameters from the optic tracts (OT) that are part of the anterior visual pathways (Fig. 1). The OTs are an example of small but well-defined structures that are visible in a regular clinical whole-brain DTI scan. Furthermore, the OTs are of specific interest in several pathological conditions affecting the visual pathways and the eyes.Fig. 1

Bottom Line: ROI selection in small structures is challenging; the final measurement results could be affected due to the significant impact of small geometrical errors.Manual tracing was performed in 1) the b0 image and 2) a T1-weighted image registered to the FA image.Semi-automatic segmentation was performed based on 3) tractography and 4) the FA-skeleton algorithm in the tract-based spatial statistics (TBSS) framework.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical Neuroscience and Rehabilitation, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden. ylva.lilja@neuro.gu.se.

ABSTRACT

Background: To extract DTI parameters from a specific structure, a region of interest (ROI) must be defined. ROI selection in small structures is challenging; the final measurement results could be affected due to the significant impact of small geometrical errors. In this study the optic tracts were analyzed with the aim to assess differences in DTI parameters due to ROI method and to identify the most reliable method.

Methods: Images of 20 healthy subjects were acquired. Fractional anisotropy (FA) was extracted from the optic tracts by four different ROI methods. Manual tracing was performed in 1) the b0 image and 2) a T1-weighted image registered to the FA image. Semi-automatic segmentation was performed based on 3) tractography and 4) the FA-skeleton algorithm in the tract-based spatial statistics (TBSS) framework. Results were analyzed with regard to ROI method as well as to inter-scan, intra-rater and inter-rater reliability.

Results: The resulting FA values divided the ROI methods into two groups that differed significantly: 1) the FA-skeleton and the b0 methods showed higher FA values compared to 2) the tractography and the T1-weighted methods. The intra- and inter-rater variabilities were similar for all methods, except for the tractography method where the inter-rater variability was higher. The FA-skeleton method had a better reproducibility than the other methods.

Conclusion: Choice of ROI method was found to be highly influential on FA values when the optic tracts were analyzed. The FA-skeleton method performed the best, yielding low variability and high repeatability.

No MeSH data available.