Does intensity modulation increase target dose calculation errors of conventional algorithms for lung SBRT?. (1st February 2018)

• Record Type: Journal Article
• Authors: Zheng, Dandan; Verma, Vivek; Wang, Shuo; Liang, Xiaoying; Zhou, Sumin
• Is Part Of: Journal of applied clinical medical physics. Volume 19:Number 2(2018)
• Page Start: 154
• Page End: 159
• Publication Date: 2018-02-01
• Subjects: IMRT -- lung -- Monte Carlo -- SBRT -- VMAT; Medical physics -- Periodicals; Clinical medicine -- Periodicals; Health Physics; Clinical Medicine; Electronic journals; Periodicals; Periodicals; Fulltext; Internet Resources; 610.153
• DOI: 10.1002/acm2.12266
• Languages: English
• ISSNs: 1526-9914

Abstract

Abstract: Purpose: Conventional dose algorithms (Type A and Type B) for lung SBRT can display considerable target dose errors compared to Type‐C algorithms. Intensity‐modulated techniques (IMRT/VMAT) are increasingly being utilized for lung SBRT. Therefore, our study aimed to assess whether intensity modulation increased target dose calculation errors by conventional algorithms over conformal techniques. Methods: Twenty lung SBRT patients were parallely planned with both IMRT and dynamic conformal arc (DCA) techniques using a Type‐A algorithm, and another 20 patients were parallely planned with IMRT, VMAT, and DCA using a Type‐B algorithm. All 100 plans were recalculated with Type‐C algorithms using identical beam and monitor unit settings, with the Type‐A/Type‐B algorithm dose errors defined using Type‐C recalculation as the ground truth. Target dose errors for PTV and GTV were calculated for a variety of dosimetric end points. Using Wilcoxon signed‐rank tests ( p < 0.05 for statistical significance), target dose errors were compared between corresponding IMRT/VMAT and DCA plans for the two conventional algorithms. The levels of intensity modulation were also evaluated using the ratios of MUs in the IMRT/VMAT plans to those in the corresponding DCA plans. Linear regression was used to study the correlation between intensity modulation and relative dose error magnitudes. Results: Overall, larger errors were found for the Type‐A algorithm than for the Type‐B algorithm. However, the IMRT/VMAT plans were not found to have statistically larger dose errors from their corresponding DCA plans. Linear regression did not identify a significant correlation between the intensity modulation level and the relative dose error. Conclusion: Intensity modulation did not appear to increase target dose calculation errors for lung SBRT plans calculated with conventional algorithms.