ESTRO meets Asia 2024 - Abstract Book

S232

Interdisciplinary – Other

ESTRO meets Asia 2024

densities. Each calculation algorithm requires a linearized calibration curve with respect to electron densities (AAA) or mass densities (Acuros), and this curve is obtained with the DirectDensity reconstruction algorithm. Six plans were created with four 3D beams with AP, PA, LD, and LI distributions to compare the dosimetric differences in the inserts of the standard, eDD, and mDD reconstructions for the AAA and Acuros calculation algorithms.

Results:

In the following table, we present the actual and estimated electron densities, as well as the Hounsfield Units (HU) for each insert, along with the average doses obtained and the percentage error associated with choosing each reconstruction.

Table 1. Measurements

The doses obtained with both algorithms and their corresponding reconstructions (eDD reconstruction with AAA and mDD reconstruction with Acuros) are practically identical. The maximum deviations for AAA in the standard and mDD reconstructions, and for Acuros in the eDD reconstruction, were less than 1%. However, higher errors were obtained in the standard reconstruction with Acuros, with the material "CB2- 30%CaCo3" showing the highest error (2%).

Conclusion:

Generally, for higher densities, the error is greater than for lower densities. However, the error that would be incurred if a different reconstruction were selected is around 0.5%, and therefore, does not represent significant differences.

Keywords: CT, DIRECTDENSITY RECONSTRUCTION ALGORITHM

References:

[1] “DirectDensity cookbook. A guide to personalized CT imaging in RT”. Siemens Healthineers.

[2] “T. Zhao et al. Evaluation of the use of direct Electron Density CT images in RT”. AAPM 2016.