A Dose Falloff Gradient Study in RapidArc Planning of Lung Stereotactic Body Radiation Therapy

被引：14

作者：

Narayanasamy, Ganesh ^{[1
]}

Desai, Dharmin ^{[2
]}

Maraboyina, Sanjay ^{[1
]}

Penagaricano, Jose ^{[1
]}

Zwicker, Robert ^{[3
]}

Johnson, Ellis Lee ^{[3
]}

机构：

[1] Univ Arkansas Med Sci, Dept Radiat Oncol, Slot 771,4301 W Markham St, Little Rock, AR 72205 USA

[2] Mem Hosp, Chattanooga, TN USA

[3] Univ Kentucky, Dept Radiat Med, Lexington, KY USA

来源：

JOURNAL OF MEDICAL PHYSICS | 2018年 / 43卷 / 03期

关键词：

Dose falloff; dose gradient; lung stereotactic body radiation therapy; stereotactic body radiation therapy dose falloff; stereotactic body radiation therapy planning;

D O I：

10.4103/jmp.JMP_38_18

中图分类号：

R8 [特种医学]; R445 [影像诊断学];

学科分类号：

1002 ; 100207 ; 1009 ;

摘要：

Introduction: Radiation Therapy Oncology Group (RTOG) report #0813 and 0915 recommends using D-2cm and R-50% as plan quality metrics for evaluation of normal tissue sparing in stereotactic body radiation therapy (SBRT) of lung lesion. This study introduces dose falloff gradient (DFG) as a tool for analyzing the dose beyond the planning target volume (PTV) extending into normal tissue structures. In ascertaining the impact of PTV size and SBRT planning techniques in DFG, this study questions the independence of the RTOG recommended metrics. Materials and Methods: In this retrospective study, 41 RapidArc lung SBRT plans with 2 or 3 complete or partial arcs were analyzed. PTV volumes ranged between 5.3 and 113 cm(3) and their geographic locations were distributed in both lungs. 6MV, 6 MV-FFF, 10 MV, or 10 MV-FFF energies were used. RTOG-0915 metrics conformity index, homogeneity index, D-2cm, R-50% and HDloc were evaluated. DFG was computed from the mean and maximum dose in seven concentric 5 mm wide rings outside the PTV. DFG was investigated against the volume of normal lung irradiated by 50% isodose volume. Treatment plans with alternate energy and couch rotations were generated. Results: The dose falloff beyond PTV was modeled using a double exponential fit and evaluated for relationship with intermediate lung dose. Photon energy and beam configuration had a minimal impact on the dose falloff outside. The product of normalized D-2cm. and R-50% was estimated to have a slowly varying value. Conclusions: Dose falloff outside PTV has been studied as a function of radial distance and ascertained by intermediate dose to normal lung. DFG can serve as a complementary plan quality metric.

引用

页码：147 / 154

页数：8

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