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Improving interobserver agreement and performance of deep learning models for segmenting acute ischemic stroke by combining DWI with optimized ADC thresholds

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Abstract

Objectives

To examine the role of ADC threshold on agreement across observers and deep learning models (DLMs) plus segmentation performance of DLMs for acute ischemic stroke (AIS).

Methods

Twelve DLMs, which were trained on DWI-ADC-ADC combination from 76 patients with AIS using 6 different ADC thresholds with ground truth manually contoured by 2 observers, were tested by additional 67 patients in the same hospital and another 78 patients in another hospital. Agreement between observers and DLMs were evaluated by Bland-Altman plot and intraclass correlation coefficient (ICC). The similarity between ground truth (GT) defined by observers and between automatic segmentation performed by DLMs was evaluated by Dice similarity coefficient (DSC). Group comparison was performed using the Mann-Whitney U test. The relationship between the DSC and ADC threshold as well as AIS lesion size was evaluated by linear regression analysis. A p < .05 was considered statistically significant.

Results

Excellent interobserver agreement and intraobserver repeatability in the manual segmentation (all ICC > 0.98, p < .001) were achieved. The 95% limit of agreement was reduced from 11.23 cm2 for GT on DWI to 0.59 cm2 for prediction at an ADC threshold of 0.6 × 10−3 mm2/s combined with DWI. The segmentation performance of DLMs was improved with an overall DSC from 0.738 ± 0.214 on DWI to 0.971 ± 0.021 on an ADC threshold of 0.6 × 10−3 mm2/s combined with DWI.

Conclusions

Combining an ADC threshold of 0.6 × 10−3 mm2/s with DWI reduces interobserver and inter-DLM difference and achieves best segmentation performance of AIS lesions using DLMs.

Key Points

Higher Dice similarity coefficient (DSC) in predicting acute ischemic stroke lesions was achieved by ADC thresholds combined with DWI than by DWI alone (all p < .05).

DSC had a negative association with the ADC threshold in most sizes, both hospitals, and both observers (most p < .05) and a positive association with the stroke size in all ADC thresholds, both hospitals, and both observers (all p < .001).

An ADC threshold of 0.6 × 10−3 mm2/s eliminated the difference of DSC at any stroke size between observers or between hospitals (p = .07 to > .99).

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Abbreviations

ADC:

Apparent diffusion coefficient

aGT:

ADC-gated ground truth

AIS:

Acute ischemic stroke

DLM:

Deep learning model

DSC:

Dice similarity coefficient

DSCg :

Dice similarity coefficient between two manually contoured ground truths

DSCp :

Dice similarity coefficient between the prediction and the ground truth

DWI:

Diffusion-weighted imaging

ESM:

Electrical supplementary material

GT:

Ground truth

H1:

China Medical University Hospital

H2:

China Medical University Hsinchu Hospital

ICC:

Intraclass correlation coefficient

LOA-95:

95% limits of agreement (i.e., 1.96 standard deviation)

mGT:

Manually contoured ground truth

sGT:

Semiautomatically defined ground truth

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Acknowledgements

The authors are grateful for the financial support from China Medical University Hsinchu Hospital and Taiwan Ministry of Science and Technology (Taiwan).

Funding

C.J.J. received financial support partly from China Medical University Hsinchu Hospital (CMUHCH-DMR-109-017 and CMUHCH-DMR-110-016). Y.J.L. received financial support partly from Taiwan Ministry of Science and Technology (107-2221-E-035 -033 -MY3).

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Correspondence to Ruey-Feng Chang or Yi-Jui Liu.

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The scientific guarantor of this publication is C.J.J.

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The authors of this manuscript declare no relationships with any companies whose products or services may be related to the subject matter of the article.

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One of the authors has significant statistical expertise.

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• retrospective

• diagnostic study

• multi-center study

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Ruey-Feng Chang and Yi-Jui Liu contribute equally to this work.

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Juan, CJ., Lin, SC., Li, YH. et al. Improving interobserver agreement and performance of deep learning models for segmenting acute ischemic stroke by combining DWI with optimized ADC thresholds. Eur Radiol 32, 5371–5381 (2022). https://doi.org/10.1007/s00330-022-08633-6

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