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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.


Mean and 95 % confidence interval (CI) of FA values per position, for all four ROI methods separately. Overall trends are represented as splines fitted to data
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Fig4: Mean and 95 % confidence interval (CI) of FA values per position, for all four ROI methods separately. Overall trends are represented as splines fitted to data

Mentions: There were no significant differences of FA between the sides (left and right OTs), therefore the averaged FA over both sides was used for further comparisons between methods. The resulting FA values divided the ROI methods into two groups that were significantly different from each other (corrected p < 0.05), but within each group there were no significant differences: 1) the manual b0 and the FA-skeleton methods and 2) the manual T1W and the tractography methods (Fig. 4, Table 1). The latter was true for all sections but Background section (the most anterior 5 mm) where the tractography and the manual T1W methods differed significantly. FA values were higher using the FA-skeleton and the manual b0 methods compared to the tractography and the manual T1W method, for all OT sections (Table 2).Fig. 4


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)

Mean and 95 % confidence interval (CI) of FA values per position, for all four ROI methods separately. Overall trends are represented as splines fitted to data
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig4: Mean and 95 % confidence interval (CI) of FA values per position, for all four ROI methods separately. Overall trends are represented as splines fitted to data
Mentions: There were no significant differences of FA between the sides (left and right OTs), therefore the averaged FA over both sides was used for further comparisons between methods. The resulting FA values divided the ROI methods into two groups that were significantly different from each other (corrected p < 0.05), but within each group there were no significant differences: 1) the manual b0 and the FA-skeleton methods and 2) the manual T1W and the tractography methods (Fig. 4, Table 1). The latter was true for all sections but Background section (the most anterior 5 mm) where the tractography and the manual T1W methods differed significantly. FA values were higher using the FA-skeleton and the manual b0 methods compared to the tractography and the manual T1W method, for all OT sections (Table 2).Fig. 4

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.