Background: Currently, the volume computed tomography dose index (CTDIvol), the most-used quantity to express the output dose of a computed tomography (CT) patient's dose, is not related to the real size and attenuation properties of each patient. The size-specific dose estimates (SSDE), based on the water-equivalent diameter (D W) overcome those issues. The proposed methods found in the literature do not allow real-time computation of D W and SSDE.
Purpose: This study aims to develop a software to compute D W and SSDE in a real-time clinical workflow.
Method: In total, 430 CT studies and scans of a water-filled funnel phantom were used to compute accuracy and evaluate the times required to compute the D W and SSDE. Two one-sided tests (TOST) equivalence test, Bland-Altman analysis, and bootstrap-based confidence interval estimations were used to evaluate the differences between actual diameter and D W computed automatically and between D W computed automatically and manually.
Results: The mean difference between the D W computed automatically and the actual water diameter for each slice is -0.027% with a TOST confidence interval equal to [-0.087%, 0.033%]. Bland-Altman bias is -0.009% [-0.016%, -0.001%] with lower limits of agreement (LoA) equal to -0.0010 [-0.094%, -0.068%] and upper LoA equal to 0.064% [0.051%, 0.077%]. The mean difference between D W computed automatically and manually is -0.014% with a TOST confidence interval equal to [-0.056%, 0.028%] on phantom and 0.41% with a TOST confidence interval equal to [0.358%, 0.462%] on real patients. The mean time to process a single image is 13.99 ms [13.69 ms, 14.30 ms], and the mean time to process an entire study is 11.5 s [10.62 s, 12.63 s].
Conclusion: The system shows that it is possible to have highly accurate D W and SSDE in almost real-time without affecting the clinical workflow of CT examinations.
Keywords: CT; SSDE; automatic; dose; real-time; software; water-equivalent.
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