Tadamasa Yoshitake MD, Presenter: Nothing to Disclose

Yoshiyuki Shioyama, Abstract Co-Author: Nothing to Disclose

Katsumasa Nakamura MD, PhD, Abstract Co-Author: Nothing to Disclose

Saiji Ohga MD, Abstract Co-Author: Nothing to Disclose

Takeshi Nonoshita, Abstract Co-Author: Nothing to Disclose

Kayoko Ohnishi, Abstract Co-Author: Nothing to Disclose

Kaori Asai, Abstract Co-Author: Nothing to Disclose

Keiji Matsumoto, Abstract Co-Author: Nothing to Disclose

Hideki Hirata, Abstract Co-Author: Nothing to Disclose

Hiroshi Honda MD, Abstract Co-Author: Nothing to Disclose

Purpose:"Although ground glass opacity (GGO) nodules were often treated with stereotactic radiotherapy (SRT), the influence of the internal electron density on heterogeneity correction of calculation algorithm and dose prescription method has not been clarified yet. In this study, we evaluated the impact of the difference between GGO and solid nodules on calculation algorithm and dose prescription methods in SRT."Materials and Methods:"Fifteen patients with pulmonary GGO nodules (GGO group) which were treated with SRT in Kyushu University Hospital were enrolled. Fifteen similar-sized solid nodules (solid group) which were treated with SRT were selected as controls. The radiotherapy was planned using a three-dimensional radiotherapy treatment planning system (Eclipse version 6.5; Varian Medical Systems, Inc., Palo Alto, CA). Total monitor units (MUs) and lung V20 were calculated with four different methods as follows: Homo-IC, Batho Power Law (BPL) algorithm and prescribed at isocenter; Homo-D95, BPL algorithm and prescribed to PTV D95; Hetero-IC, anisotropic analytical algorithm (AAA) algorithm and prescribed at isocenter; and Hetero-D95, AAA algorithm and prescribed to PTV D95. In each pulmonary nodule, the proportion of total MUs and lung V20 using Homo-D95, Hetero-IC, and Hetero-D95 compared to those using Homo-IC was calculated, respectively. Student’s t-test was performed between GGO and solid groups."Results:"In GGO / solid groups, the proportion of total MUs using Homo-D95, Hetero-IC, and Hetero-D95 compared to that using Homo-IC were 1.040 ± 0.008 / 1.036 ± 0.008 (p=0.170), 1.054 ± 0.033 / 1.019 ± 0.025 (p=0.003), and 1.182 ± 0.036 / 1.172 ± 0.038 (p=0.447), respectively, and the proportion of lung V20 were 1.040 ± 0.012 / 1.041 ± 0.020 (p=0.974), 0.998 ± 0.030 / 0.952 ± 0.024 (pConclusion:"In SRT for GGO using calculation algorithm with heterogeneity correction and prescription to isocenter, radiation dose can be escalated unexpectedly compared to solid nodules."

Yoshitake, T, Shioyama, Y, Nakamura, K, Ohga, S, Nonoshita, T, Ohnishi, K, Asai, K, Matsumoto, K, Hirata, H, Honda, H, Dosimetric Evaluation In Stereotactic Radiotherapy for Pulmonary Ground-glass Opacity Nodules: The Relationship with Calculation Algorithm And Dose Prescription Methods.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9020229.html