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Uncertainty in tissue equivalent proportional counter assessments of microdosimetry and RBE estimates in carbon radiotherapy
| Content Provider | Scilit |
|---|---|
| Author | Hartzell, Shannon Guan, Fada Taylor, Paige Peterson, Christine B. Taddei, Phillip J. Kry, Stephen F. |
| Copyright Year | 2021 |
| Description | Journal: Physics in Medicine & Biology |
| Abstract | Microdosimetry is an important tool for assessing energy deposition distributions from ionizing radiation at cellular and cellular nucleus scales. It has served as an input parameter for multiple common mathematical models, including evaluation of relative biological effectiveness (RBE) of carbon ion therapy. The most common detector used for microdosimetry is the tissue-equivalent proportional counter (TEPC). Although widely applied, the TEPC has various inherent uncertainties. Therefore, this work quantified the magnitude of TEPC measurement uncertainties and their impact on RBE estimates for therapeutic carbon beams. Microdosimetric spectra and frequency-, dose-, and saturation-corrected dose-mean lineal energy $(y_{F}$, $y_{D}$, $y^{}$) were calculated using the Monte Carlo toolkit Geant4 for five monoenergetic and three SOBP carbon beams in water at every millimeter along the central beam axis. We simulated the following influences on these spectra from eight sources of uncertainty: wall effects, pulse pile-up, electronics, gas pressure, W-value, gain instability, low energy cut-off, and counting statistics. statistic uncertainty was quantified as the standard deviation of perturbed values for each source. Bias was quantified as the difference between default lineal energy values and the mean of perturbed values for each systematic source. Uncertainties were propagated to RBE using the modified microdosimetric kinetic model (MKM). Variance introduced by statistic sources in $y_{F}$ and $y_{D}$ averaged 3.8% and 3.4%, respectively, and 1.5% in $y^{}$ across beam depths and energies. Bias averaged 6.2% and 7.3% in $y_{F}$ and $y_{D}$ , and 4.8% in $y^{}$. These uncertainties corresponded to 1.2±0.9% on average in $RBE_{MKM}$. The largest contributors to variance and bias were pulse pile-up and wall effects. This study established an error budget for microdosimetric carbon measurements by quantifying uncertainty inherent to TEPC measurements. It is necessary to understand how robust the measurement of RBE model input parameters are against this uncertainty in order to verify clinical model implementation. |
| Related Links | https://iopscience.iop.org/article/10.1088/1361-6560/ac1366/pdf |
| ISSN | 00319155 |
| e-ISSN | 13616560 |
| DOI | 10.1088/1361-6560/ac1366 |
| Journal | Physics in Medicine & Biology |
| Issue Number | 15 |
| Volume Number | 66 |
| Language | English |
| Publisher | IOP Publishing |
| Publisher Date | 2021-07-12 |
| Access Restriction | Open |
| Subject Keyword | Journal: Physics in Medicine & Biology Carbon Radiotherapy Relative Biological Effectiveness Tissue Equivalent Proportional Counter |
| Content Type | Text |
| Resource Type | Article |
| Subject | Radiology, Nuclear Medicine and Imaging Radiological and Ultrasound Technology |
