Research Article
Novel Anisotropic Margin Calculation Based On the Cumulative Frequency Distribution of Uncertainties in the Clinical Target Volume
| Ryu Kawamorita1,2*, Hajime Monzen1, Wataru Okada2, Ryuta Nakahara2, Shun Kishimoto2, Kentaro Ishii2, Toshifumi Nakajima2 and Yasumasa Nishimura1 | |
| 1Department of Radiation Oncology, Kinki University, Faculty of Medicine, Osaka-Sayama, Osaka, Japan | |
| 2Department of Radiation Oncology, Tane General Hospital, Osaka-Nishiku, Osaka, Japan. | |
| Corresponding Author : | Ryu Kawamorita Department of Radiation Oncology Tane General Hospital, 1-12-21 Kujo-Minami, Nishi-ku Osaka city, Osaka 550-0025, Japan Tel: +81-6-6581-1071 Fax: +81-6-6585-2772 E-mail: kawamorita@tane.or.jp |
| Received: July 18, 2015 Accepted: August 11, 2015 Published: August 14, 2015 | |
| Citation:Kawamorita R, Monzen H, Okada W, Nakahara R, Kishimoto S, et al. (2015) Novel Anisotropic Margin Calculation Based On the Cumulative Frequency Distribution of Uncertainties in the Clinical Target Volume. OMICS J Radiol 4:202. doi:10.4172/2167-7964.1000202 | |
| Copyright: © 2015 Kawamorita R et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. | |
Abstract
Objective: The purpose of this study was to determine the PTV margins from the cumulative frequency of uncertainties of the clinical target volume (CTV) position obtained using hybrid-image guided radiotherapy (H-IGRT) with volumetric-modulated arc therapy (VMAT).
Materials and Methods: Study participants were 22 patients with intermediate-risk prostate cancer who underwent VMAT. All patients were treated using the following image-guided (IG) procedure: 1) no-correction skin mark setup (no- IG); 2) bony anatomy registration with 2D-imaging (2D-IG); and 3) organ registration using CBCT images (3D-IG). The systematic (Σtot) and random (σtot) errors were obtained from the no-IG, 2D-IG, and 3D-IG registration images of 198 fractions. The PTV margin was computed using the cumulative frequency distribution of the actual position errors of the CTV, and which was compared with the formulation by MPTV = 2.5 Σtot + 0.7 σtot.
Results: The margin size of 3D IG procedure was as follows: 3D-IG: 7.6, 5.4, and 3.5 mm for the AP, SI, and LR axes, respectively. Using MPTV = 2.5 Σtot + 0.7 σtot: 3D-IG: 4.2, 3.7, and 1.3 mm for the AP, SI, and LR axes, respectively. In MPTV: = α Σtot + β σtot, the coefficients α and β were α = 3.4, 2.3, and 4.6 and β = 2.9, 3.0, and 3.0 for AP, SI, and LR, respectively.
Conclusion: The margin size (MPTV) calculated by our modified formulation based on the margin direction satisfied 99% of the prescription dose coverage in each direction and a minimum of 95% of the dose coverage to the CTV for all patients using H-IGRT
