Academy of Medical Sciences & Peking Union Medical College, Beijing,. China, 3Department of ... Medical Science, Beijing, China, 5Cancer Hospital, Chinese Academy of. Medical Science .... to the central axis of the sinograms. ... S.W. Choi,6 S.H. Lee,7 C.K. Min,8 W.S. Yoon,9 D.S. Yang,10 Y.J. Park,1 and C.Y. Kim1; ...
E636
International Journal of Radiation Oncology Biology Physics
provide noninvasive safe delivery of the adequate dose to induce lesions to and achieve an electrical conduction block of the PV antra. Further studies are warranted for gated SAS delivery as well as delivery in an animal model to establish the effective dose as well as evaluate the safety and efficacy of this technique. Author Disclosure: J. Rahimian: None. A. Torossian: None. M. Shenasa: None.
Hokkaido University, Sapporo, Japan, 4Global Station for Quantum Medical Science and Engineering, Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University, Sapporo, Japan, 5Stanford University School of Medicine, Stanford, CA, 6 Department of Radiation Oncology, Stanford University, Stanford, CA
3559 A Customized Tissue Compensator With 3-Dimensional Print Technique for Chest Wall Electron Irradiation N. Li,1 Y. Tian,2 J. Jin,1 Y. Li,3 Y. Tang,1 W. Liu, Jr,1 W. Wang,1 S. Wang,3 Y. Liu,1 X. Liu,4 Z. Yu,5 and J. Dai2; 1Cancer Hospital and Institute, Chinese Academy of Medical Sciences (CAMS) and Peking Union Medical College (PUMC), Beijing, China, 2Cancer Hospital & Institute, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China, 3Department of Radiation Oncology, Cancer Hospital and Institute, Chinese Academy of Medical Sciences (CAMS) and Peking Union Medical College (PUMC), Beijing, China, 4Cancer Hospital, Chinese Academy of Medical Science, Beijing, China, 5Cancer Hospital, Chinese Academy of Medical Science, Beijing, China Purpose/Objective(s): To investigate dosimetric distribution of customized tissue compensator with a 3D printing technique for chest wall electron irradiation in patients with breast cancer after mastectomy. Materials/Methods: The customized tissue compensator (C-bolus) was made 0.5 cm thick in the region of the chest wall that was thicker than 2.0 cm. In the region of chest wall thickness of less than 2.0 cm, surface of the bolus was generated by extending 2.0 cm from the posterior border of the chest wall. The flat tissue compensator (F-bolus) was made 0.5 cm thick homogeneously. Six single-beam electron plans were computed for the chest wall with a customized or flat tissue compensator to compare the target dose coverage and doses to the critical structures including heart, lung, and left anterior descending coronary artery (LAD). Three plans were computed for the left chest wall, the other 3 for the right. In order to evaluate the 3D printed bolus, treatment plans were generated with Cbolus, which has a density of 1.335 g/cm3, and printed. For dose profile measurement, film for measuring patient dosimetry for intensity modulated radiation therapy plan verification was used. A photo scanner was also used to determine the optical density of the films, and scientific imaging software was used for the film analysis. Results: Single-beam electron plans with C-bolus or F-bolus showed similar target dose coverage; however, C-bolus provided a lower dose for heart and lung. The mean dose (Gy), V20(%) and V10(%) of the ipsilateral lung were 9.11.9 Gy, 19.7%4.2%, and 28.5%4.1% by F-bolus, and 4.80.54 Gy, 8.3%1.0%, and 16.5%1.6% by C-bolus, respectively. For the left chest wall plans, mean dose (Gy) of heart and LAD were significantly reduced from 2.30.5 Gy and 13.90.9 Gy with F-bolus to 1.80.2 Gy and 4.90.5 Gy with C-bolus, respectively. In addition, mean doses of chest wall were 43.53.0 Gy and 42.82.6 Gy with C-bolus and F-bolus, respectively. On visual inspection, compared with F-bolus, the films showed the same dose in the chest wall and a decreased dose in the lung and heart with C-bolus. Conclusion: C-bolus saved more normal tissue compared with F-bolus without compromising target dose coverage. 3D print C-bolus, a novel technique, is feasible for chest wall electron irradiation. Author Disclosure: N. Li: None. Y. Tian: None. J. Jin: None. Y. Li: None. Y. Tang: None. W. Liu: None. W. Wang: None. S. Wang: None. Y. Liu: None. X. Liu: None. Z. Yu: None. J. Dai: None.
3560 Enabling Conventional Cone Beam Computed Tomography With the Capability of Dual Energy Imaging Using a Simple Add-on Beam Modifier R. Vinke,1 S. Takao,2 K. Umegaki,3 H. Shirato,4 H. Peng,5 and L. Xing6; 1 Stanford University, Palo Alto, CA, 2Department of Radiation Oncology, Hokkaido University Hospital, Sapporo, Japan, 3Faculty of Engineering,
Purpose/Objective(s): Dual-energy computed tomography (DECT) is currently implemented in 4 different ways, including single-source dual energy, dual-source dual energy, fast kV-switching, and energy discriminant detectors, but none of them is easily adaptable by the onboard imaging system for DECT. In searching for a robust, efficient, and costeffective dual-energy cone beam CT (DE- CBCT) solution for various radiation oncology applications, in particular for improved proton dose planning/replanning accuracy and DE-CBCT guided radiation therapy, we investigated a novel energy modulation scheme using a beam modifier placed between the source and patient and optimized its geometric configuration for routine clinical use. Materials/Methods: The study was performed using a CBCT scanner, and the tube voltage was set at 120 kVp. The higher energy beam was obtained by filtering the incident utilizing a beam modulation layer (material: copper; thickness: 1.8 mm). The energy spectra with and without the modulation layer were measured with a CdTe detector. To avoid the need for double scans (one with and one without the energy modulator), the modulation layer was configured to cover only the half of the x-ray beam so that 2 sets of sinograms corresponding to low and high energies were collected after a single-gantry rotation of 360 degrees. To obtain the respective sinogram for each energy, the measured data were reorganized by flipping low-energy projection data of the first 180 degrees with respect to the central axis of the sinograms. Each measurement consists of 640 projections at an interval of 0.5 degree. To reduce the image noise or imaging dose, the common information shared by the 2 energies were also utilized during the image reconstruction step. A Gammex 467 tissue characterization phantom was used, which includes rods of water, bone (B2-30% mineral), cortical bone (SB3), lung (LN-300), brain, and titanium equivalent materials. The average high-energy and low-energy HU numbers (HUhigh and HUlow) were derived for pixels in a defined region of interest, respectively. Results: The beam modifier increased the threshold of the energy spectrum from w20 keV up to w50 keV. Two complete sets of images were obtained with good alignment between the high-energy and low-energy cases without any artifact observed. The HUlow/HUhigh was w0/0 (water), w394/238 (brain), w1283/1085 (cortical bone), and w3000/1800 (titanium). By applying a bisecting line (HUlowZHUhigh, slopeZ1), the titanium equivalent material was well separated from other materials. Conclusion: The feasibility of the proposed DECT implementation using a beam modifier has been demonstrated. Compared to the existing DECT solutions, the proposed scheme is much more cost-effective and requires minimum hardware modification. The work lays the foundation for us to quantitatively evaluate material density images (iodine/calcium/water) and atomic number (and electron density) of substances, and this is being applied to improve proton therapy. Author Disclosure: R. Vinke: None. S. Takao: None. K. Umegaki: None. H. Shirato: None. H. Peng: None. L. Xing: None.
3561 A Study of Acute Genitourinary and Gastrointestinal Toxicity Relationship With Planning Index in Prostate Cancer Treated by Helical Tomotherapy S. Lee,1 K.H. Kim,2 Y.J. Cao,3 J.B. Shim,4 K.H. Chang,5 J.S. Ko,6 S.W. Choi,6 S.H. Lee,7 C.K. Min,8 W.S. Yoon,9 D.S. Yang,10 Y.J. Park,1 and C.Y. Kim1; 1Department of Radiation Oncology, Korea University Medical Center Anam Hospital, Seoul, South Korea, 2Department of Biomedical Science, College of Science & Technology, Korea University, Sejong, South Korea, 3Department of Radiation Oncology, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer and Tianjin Key Laboratory of Cancer Prevention and Therapy, Tianjin, China, 4Department of radiation Oncology, College of Medicine, Korea University, Seoul, South Korea, 5Department of radiation
