Author: Klaus Bacher, Louise D'hondt, Jeff Rutten, Gwenny Verfaillie 👨🔬
Affiliation: Ghent University 🌍
Purpose: Manual organ segmentation is a very time-consuming but necessary process in personalized dosimetry. Automatic segmentation tools may alleviate this task. In this study the impact of automatic segmentation on organ dose estimations was investigated.
Methods: Whole-body CT images from 100 patients, who underwent a diagnostic PET-CT scan, were used as a voxel model in the ImpactMC Monte Carlo software. CT scanner characteristics (X-ray spectrum, bowtie filter) were measured and used as an input for the full-body CT exposure simulations. On the original CT images, organ segmentations were done manually and automatically using the open source software tool TotalSegmentator. The Dice coefficient was used to evaluate the quality of the automatic segmentations. The segmented organs were used as an overlay on the simulated dose distribution in order to calculate patient-specific organ doses. As such, for each patient, doses to the heart, liver, lungs, kidneys, ribs, esophagus and spine were calculated.
Results: The average Dice coefficients were 0.74, 0.93, 0.90, 0.90, 0.80, 0.76 and 0.84 for the heart, liver, lungs, kidneys, ribs, esophagus and spine respectively. Compared to the doses based on manual segmentation, automatic segmentation resulted in relative differences of 0.31% ± 0.64%, 0.10% ± 0.23%, -0.58% ± 1.31%, 0.33% ± 0.54%, -2.57% ± 4.40%, -0.89% ± 2.34% and -0.25% ± 4.59% for the heart, liver, lungs, kidneys, ribs, esophagus and spine respectively. All dose differences were found to be non-significant based on a Student's t-test. While the breasts and thyroid were also manually segmented, TotalSegmentator was unable to automatically segment these organs.
Conclusion: We found that TotalSegmentator allows fast and reliable segmentations for the use in personalized organ dosimetry, however, some organs could not be segmented automatically. Although the Dice coefficient did not show great agreement for some organs, the impact on the organ doses was minor.