Dosimetric Analysis of Optimization Using Generalized Equivalent Uniform Dose in
Radiotherapy Planning for Lower Mid-Thoracic Esophageal Cancer
ZENG Huaqu1,2, ZHANG Hui1,3, WU Qibing1,4
1. School of Biomedical Engineering, Anhui Medical University, Hefei Anhui 230032, China; 2. Radiotherapy Center, Gaozhou
People’s Hospital, Maoming Guangdong 525200, China; 3. Department of Radiation Oncology, The First Affiliated Hospital of
University of Science and Technology of China, Hefei Anhui 230032, China; 4. Department of Radiation Oncology,
The First Affiliated Hospital of Anhui Medical University, Hefei Anhui 230032, China
Abstract：Objective To study the influence of dose-volume (DV) target optimization on dose distribution by adding different
generalized equivalent uniform dose (gEUD) optimization parameters a in the intensity-modulated esophageal cancer volume
planning. Methods Sixteen patients with mid-to-lower esophageal cancer were retrospectively selected, and six volumetric
modulated arc therapy (VMAT) plans, were designed for each patient, DV plan was optimized using only DV, and DV_a1 was
optimized based on the addition of DV to the heart was a=1, the whole lung was a=1 and the spinal cord was a=20. Based on DV,
the mean target parameter was added to the heart and lung, and the spinal cord was a=20, which was optimized as DV_mean. It was
optimized by adding was a=1 to the heart, was a=0.1 to the whole lung and was a=20 to the spinal cord with DV, and was named
DV_a0.1. It was optimized by adding was a=3 in the heart, was a=3 in the lungs and was a=20 in the spinal cord with DV, and was
named DV_a3. It was optimized based on the objective function of adding was a=1 to the heart, was a=1 to the whole lung and
was a=40 to the spinal cord by DV, and named DV_a40. And all plans meet the target prescription dose covering more than 95%
of the target area volume. The conformal index (CI) and homogeneity index (HI) of the target, V5, V10, V20, V30 and mean dose for
both lungs, V30, V40 and mean dose for the heart, and maximum dose for the spinal cord were compared. Results There was no
significant difference in target CI among the six plans (P＞0.05), and the HI of the DV_a3 was significantly lower than
that of DV and DV_a1 (P＜0.001 and P=0.016), were also worse than DV_mean, although there was no significant difference
(P=1.000). Compared with DV, DV_mean and DV_a3, DV_a0.1 significantly decreased V5 (P＜0.05), but significantly increased V20 (P＞0.003), DV_a3 can significantly reduce the V30 of the whole lung (P＜0.02) and cardiac V40 (P＜0.001). There was no
significant difference in mean dose between DV_a1 and DV_mean on lung and heart (P=0.189 and P=1.000), but DV_a1 can lower
the average dose even more. DV_a40 significantly decreased the maximum dose of spinal cord compared with DV_a1 and
DV (P=0.014 and P＜0.001). Conclusion Adding gEUD-upper optimized target to the organs at risk based on the dose volume
plan can significantly reduce the dose to the organ at risk while maintaining dose coverage in the target. Different values of the gEUD
optimization target parameters a can achieve different levels of dose volume reduction to the organ at risk, and optimization with an
objective of a=1 tends to reduce the average dose to the organ at risk more than optimization with an average dose objective function.
