Comparison of the Dose Comparison and DVH Comparison modules results

Slicer version:4.10.1
Hi 3D Slicer experts and all
I have 2 RT Dose (RT Dose1 and RT Dose2) and a segmentation (renamed PTV). I compared 2 dose distribution for PTV, with Dose Comparison module; and the Pass Fraction was calculated 96.46%. Also, I calculated DVHs for them with Dose Volume Histogram module and Exported them into a CSV File(figure1), which the results up to 1.7 Gy are similar; but the Agreement acceptance is 92.31%. can you help me about my questions:

1- As shown in figure1, the received dose for PTV , up to 1.7 Gy is similar with RT Dose1 and RT Dose2. so, why is the Agreement acceptance = 92.31%? shouldn’t it be more than 92.31%?

2- Pass Fraction in Dose comparison module is 96.46% and Agreement acceptance is 92.31%. what is the reason for this difference?

Thanks a lot

@gcsharp @cpinter do you know if the results above can be normal or they are unexpected?

  1. Why do you think it “should be more than 92.31%” ? The dose comparison module compares the dose volumes themselves, using the Gamma comparison method [1]. It is based on dose difference and distance-to-agreement, and has many parameters, such as the acceptance thresholds of these two components. SlicerRT’s gamma algorithm has been validated against other implementations, and it was found to have a 100% match to the baselines [2].

  2. Dose comparison is based on the dose volumes themselves, while DVH comparison compares derived metrics: the DVHs, which are a considerably simplified representation of the dose volumes considering the segmented structures. The DVHs are compared using a simplified Gamma method [3], and has similar but different parameters, and different defaults for those.

[1] Low, D. a., & Dempsey, J. F. (2003). Evaluation of the gamma dose distribution comparison method. Medical Physics, 30(9), 2455.
[2] Alexander, K. M., Pinter, C., Fichtinger, G., Olding, T., & Schreiner, L. J. (2018). Streamlined Open-Source Gel Dosimetry Analysis in 3D Slicer. Biomed. Phys. Eng. Express, 1–23.
[3] Ebert, M. a, Haworth, a, Kearvell, R., Hooton, B., Hug, B., Spry, N. a, … Joseph, D. J. (2010). Comparison of DVH data from multiple radiotherapy treatment planning systems. Physics in Medicine and Biology, 55(11), N337-46.

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