Related Experiment Video
Updated: Dec 11, 2025
Construction of a Preclinical Multimodality Phantom Using Tissue-mimicking Materials for Quality Assurance in Tumor Size Measurement
Published on: July 29, 2013
[Effect of Relative Electron Density and Physical Density Adjustment in Patient-specific Quality Assurance Using PMMA
Hiroyuki Nakamura1, Kazuhiro Kawano1, Takaaki Tooyama1
1Department of Central Radiology, Saiseikai Suita Hospital.
Purpose:
The purpose of this study was to improve the accuracy of dose-distribution calculations by understanding how the calculated dose varies with the change in the relative electron density replacing polymethyl methacrylate (PMMA) in patient-specific quality assurance.
Method:
We calculated the relative electron density at which dose attenuation in each dose calculation algorithm coincides with the measured value of the dose attenuation of single-field irradiation. Next, the dose change was calculated by changing the relative electron density or physical electron density for substituting PMMA for each X-ray energy and calculation algorithm. Furthermore, using clinical plans, changes in point-dose verification and dose-distribution verification that occurred when the relative electron density or physical electron density was varied were investigated.
Results:
The dose attenuation varies depending on the dose-calculation algorithm, and the optimum value of the electron density is different for each. After the electron density optimization, the point dose verification using the 97.1% to 98.3% (3%/3 mm), 90.0% to 94.3% (2%/3 mm) and gained a dominant improvement tendency (P<0.001).
Conclusions:
We clarified dose change accompanying relative electron density or physical electron density change. We concluded that the accuracy of dose-distribution calculation for verification improves by replacing PMMA with optimal relative electron density or physical electron density.
