Session Item

Delineation of target and organ at Risk (OAR) is one of the most important, time consuming and operator-dependent tasks in radiation therapy. There are different systems/algorithms for automatic OAR contouring. One of them is Siemens DirectOrgans algorithm (Optimized Reconstruction based Generative Adversarial Networks).
This study aims to:
a) Evaluate manual and DirectOrgans algorithm for delineation of OARs in thorax.
b) Form the basis for future work to implement automatic DirectOrgan contouring in our clinic.

Manual and DirectOrgans-segmentation of the lungs, heart and esophagus of 16 patients simulated on Siemens Go Open Pro CT were made. Difference between manually delineated volume and automatic volume (∆V, %), dice similarity coefficient (DSC), sensitivity (Se) and specificity (Incl) were calculated to compare the accuracy of these two methods. The contours were also compared visually slice by slice.

The average difference between the lungs, heart and esophagus volume delineated manually and with DirectOrgan algorithm were: -2.65% ± 3.58 (∆V ± SD), 9.93 ±11.43 and 0.86 ± 13.27. For esophagus we found ∆V from about -21.6% to 21.04%. The ∆V values for esophagus underline the difficulty in the contouring. Regarding the DSC index, the average and SD for delineated organs were: 0.96 ± 0.02 for lungs, 0.92 ± 0.03 and 0.72 ± 0.09 for heart and esophagus respectively. DSC index value approach nearly 1 for lungs and heart, it means that manually and DirectOrgans outcomes are significantly similar. For esophagus, differ outcomes significantly. The Se and Incl for lungs were nearly the same: 0.94 ± 0.03 and 0.97±0.01 (Se ± SD and Incl ± SD). For the heart the difference between Se and Incl were larger and were: 0.96 ± 0.02 and 0.88±0.07 respectively. For esophagus both Se and Incl were the same but low: 0.73 ± 0.10.

Result of this study demonstrate that DirectOrgan algorithm can be used for the delineation of OARs in the thorax region. The greatest difference between volumes contoured using the two methods is seen in those patients who had an advanced disease in these organs of interest.
This is a pilot study and future work with more patient data is needed to test the contouring of other organs from DirectOrgan's catalog before implementing in clinical use.