Dosimetric and radiobiological comparison of TG-43 and Monte Carlo calculations in ¹⁹²Ir breast brachytherapy applications

详细信息    查看全文

• 作者：V. Peppa^a ; E.P. Pappas^a ; P. Karaiskos^a ; T. Major^b ; C. Polgá ; r^b ; P. Papagiannis^a ; ^{ppapagi@med.uoa.gr" class="auth_mail" title="E-mail the corresponding author}
• 关键词：TG-43 ; MBDCA ; 192Ir ; Breast ; Brachytherapy ; Dosimetry
• 刊名：Physica Medica
• 出版年：2016
• 出版时间：October 2016
• 年：2016
• 卷：32
• 期：10
• 页码：1245-1251
• 全文大小：1661 K

文摘

To investigate the clinical significance of introducing model based dose calculation algorithms (MBDCAs) as an alternative to TG-43 in ¹⁹²Ir interstitial breast brachytherapy.

Materials and methods

A 57 patient cohort was used in a retrospective comparison between TG-43 based dosimetry data exported from a treatment planning system and Monte Carlo (MC) dosimetry performed using MCNP v. 6.1 with plan and anatomy information in DICOM-RT format. Comparison was performed for the target, ipsilateral lung, heart, skin, breast and ribs, using dose distributions, dose-volume histograms (DVH) and plan quality indices clinically used for plan evaluation, as well as radiobiological parameters.

Results

TG-43 overestimation of target DVH parameters is statistically significant but small (less than 2% for the target coverage indices and 4% for homogeneity indices, on average). Significant dose differences (>5%) were observed close to the skin and at relatively large distances from the implant leading to a TG-43 dose overestimation for the organs at risk. These differences correspond to low dose regions (<50% of the prescribed dose), being less than 2% of the prescribed dose. Detected dosimetric differences did not induce clinically significant differences in calculated tumor control probabilities (mean absolute difference <0.2%) and normal tissue complication probabilities.

Conclusion

While TG-43 shows a statistically significant overestimation of most indices used for plan evaluation, differences are small and therefore not clinically significant. Improved MBDCA dosimetry could be important for re-irradiation, technique inter-comparison and/or the assessment of secondary cancer induction risk, where accurate dosimetry in the whole patient anatomy is of the essence.